Smart Antennas: Latest Trends in Design and Application 3030766357, 9783030766351

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EAI/Springer Innovations in Communication and Computing

Praveen Kumar Malik Joan Lu B T P Madhav Geeta Kalkhambkar Swetha Amit Editors

Smart Antennas Latest Trends in Design and Application

EAI/Springer Innovations in Communication and Computing Series Editor Imrich Chlamtac, European Alliance for Innovation, Ghent, Belgium

The impact of information technologies is creating a new world yet not fully understood. The extent and speed of economic, life style and social changes already perceived in everyday life is hard to estimate without understanding the technological driving forces behind it. This series presents contributed volumes featuring the latest research and development in the various information engineering technologies that play a key role in this process. The range of topics, focusing primarily on communications and computing engineering include, but are not limited to, wireless networks; mobile communication; design and learning; gaming; interaction; e-health and pervasive healthcare; energy management; smart grids; internet of things; cognitive radio networks; computation; cloud computing; ubiquitous connectivity, and in mode general smart living, smart cities, Internet of Things and more. The series publishes a combination of expanded papers selected from hosted and sponsored European Alliance for Innovation (EAI) conferences that present cutting edge, global research as well as provide new perspectives on traditional related engineering fields. This content, complemented with open calls for contribution of book titles and individual chapters, together maintain Springer’s and EAI’s high standards of academic excellence. The audience for the books consists of researchers, industry professionals, advanced level students as well as practitioners in related fields of activity include information and communication specialists, security experts, economists, urban planners, doctors, and in general representatives in all those walks of life affected ad contributing to the information revolution. Indexing: This series is indexed in Scopus, Ei Compendex, and zbMATH. About EAI EAI is a grassroots member organization initiated through cooperation between businesses, public, private and government organizations to address the global challenges of Europe’s future competitiveness and link the European Research community with its counterparts around the globe. EAI reaches out to hundreds of thousands of individual subscribers on all continents and collaborates with an institutional member base including Fortune 500 companies, government organizations, and educational institutions, provide a free research and innovation platform. Through its open free membership model EAI promotes a new research and innovation culture based on collaboration, connectivity and recognition of excellence by community.

More information about this series at http://www.springer.com/series/15427

Praveen Kumar Malik  •  Joan Lu B T P Madhav  •  Geeta Kalkhambkar Swetha Amit Editors

Smart Antennas Latest Trends in Design and Application

Editors Praveen Kumar Malik School of Electronics and Electrical Engineering Lovely Professional University Phagwara, Punjab, India B T P Madhav Electronics and Communication Engineering K L Deemed to be University Vaddeswaram, Andhra Pradesh, India

Joan Lu School of Computing and Engineering University of Huddersfield Huddersfield, United Kingdom Geeta Kalkhambkar Electronics and Telecommunication Department Sant Gajanan Maharaj College of Engineering Kolhapur, India

Swetha Amit Department of Electronics and Telecommunication Engineering M S Ramaiah Institute of Technology Bengaluru, India

ISSN 2522-8595     ISSN 2522-8609 (electronic) EAI/Springer Innovations in Communication and Computing ISBN 978-3-030-76635-1    ISBN 978-3-030-76636-8 (eBook) https://doi.org/10.1007/978-3-030-76636-8 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

This book is dedicated to my late father, who taught me to be an independent and determined person, without whom I would never be able to achieve my objectives and succeed in life.

Late (Sr.) Dharamveer Singh

Preface

This edited book aims to bring together leading academic scientists, researchers, and research scholars to exchange and share their experiences and research results on all aspects of planer and printed antenna design. The book primarily focuses on the latest trends in the field of patch and printed antenna design and their application in various fields of wireless communication, mobile communication, vehicular communication, and wearable applications. Students from different branches of electronics, communication, and electrical engineering, researchers, and industry persons will benefit from this book. This book provides the literature students and researchers can use to design antennas for the above-mentioned applications. It also provides a premier interdisciplinary platform for researchers, practitioners, and educators to present and discuss the most recent innovations, trends, and concerns as well as practical challenges encountered and solutions adopted in the field of planer antenna design. Phagwara, Punjab, India Huddersfield, UK Vaddeswaram, Andhra Pradesh, India Kolhapur, Maharashtra, India Bengaluru, Karnataka, India

Praveen Kumar Malik Joan Lu B. T. P. Madhav Geeta Kalkhambkar Swetha Amit

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Contents

Part I Overview and Introduction of Microstrip Antenna  Microstrip Antenna: An Overview and Its Performance Parameter����������    3 Hirendra Das, Mridusmita Sharma, and Qiang Xu  Compact Dual-Fed Self-Diplexing Antenna A for Wireless Communication Application������������������������������������������������������   15 Alpesh Vala, Amit V. Patel, Rashmi Vaghela, Keyur Mahant, Hiren Mewada, Esraa Ali, and Biren Patel  Multiband Slot Microstrip Antenna for Wireless Applications ������������������   23 Mehaboob Mujawar and T. Gunasekaran  Effect of Encapsulating Materials on Monopole Antenna Performance for Underwater Communication ��������������������������������������������   35 Mehaboob Mujawar and T. Gunasekaran  Parasitic Antennas for Current and Future Wireless Communication Systems: Trends, Challenges, and Emerging Aspects����������������������������������   43 Roktim Konch, Sivaranjan Goswami, Kumaresh Sarmah, Kandarpa Kumar Sarma, and Nikos Mastorakia  Multiband Laptop Antenna with Enhanced Bandwidth for WLAN/WiMAX/GPS Wireless Applications ������������������������������������������   55 Trushit Upadhyaya, Killol Pandya, Arpan Desai, Upesh Patel, Rajat Pandey, and Merih Palandoken Part II Performance Analysis of Micro-strip Antenna  Antenna Optimization Using Taguchi’s Method������������������������������������������   69 Archana Tiwari and A. A. Khurshid

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 Novel Compact Frequency and Polarization Reconfigurable A Slot Antenna Using PIN Diodes for Cognitive Radio Applications ������������   85 V. N. Lakshmana Kumar, M. Satyanarayana, Sohanpal Singh, and Dac-Nhuong Le  Mathematical Analysis and Optimization of a Remodeled Circular Patch for 5G Communication ������������������������������������������������������������������������   97 Ribhu Abhusan Panda and Debasis Mishra  Study of Various Beamformers and Smart Antenna Adaptive Algorithms for Mobile Communication����������������������������������������  111 Elizabeth Caroline Britto, Sathish Kumar Danasegaran, Susan Christina Xavier, A. Sridevi, and Abdul Rahim Sadiq Batcha  Microstrip Patch Antennas: Past and Present State of the Art ������������������  131 Manish Sharma Part III Multiple Input Multiple Output (MIMO) Antenna Design and Uses  Planar Design, Analysis, and Characterization of Multiple-Input Multiple-Output Antenna ����������������������������������������������������  149 Manish Sharma  Design of Smooth Curved Hexagonal-­Shaped Four-Element MIMO Antenna for WiMAX, Wi-Fi, and 5G Applications��������������������������  163 S. Rekha, G. Shine Let, and Madam Singh  Quad-Port Orthogonal Wideband MIMO Antenna Employing Artificial A Magnetic Conductor for 60 GHz Millimeter-Wave Applications����������������  179 G. Viswanadh Raviteja  Massive MIMO-OFDM System Model: Existing 5G Channel Estimation Algorithms and Its Review ������������������������������������������  193 Nilofer Shaik and Praveen Kumar Malik Part IV Fractal and Defected Ground Structure Microstrip Antenna Dual-Band Compact Transparent Fractal Antenna for Smart WLAN Applications ����������������������������������������������������������������������  213 Minesh Thaker, Ashwin Patani, Arpan Desai, and Trushit Upadhyaya  Tapered Circular CPW-Fed Wideband Fractal Patch Antenna A for IoT Applications ����������������������������������������������������������������������������������������  223 Geeta Kalkhambkar, Rajashri Khanai, Pradeep Chindhi, and Pradeep Kumar  Novel Ultra-Wideband Monopole Antenna with Defected A Ground Structure for X-Band and WiMAX Applications ��������������������������  233 T. Poornima and Korhan Cengiz

Contents

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 Design and Analysis of DGS-Based Fractal Antenna for Metrological Satellite ��������������������������������������������������������������������������������  247 Vimlesh Singh, Amit Kumar, and Mahesh Kumar Aghwariya Part V Importance and Uses of Microstrip Antenna in IoT  Applications of Microstrip Antenna in IoT ��������������������������������������������������  259 Amit Kumar, Mahesh Kumar Agwariya, and Vimlesh Singh  Design of High Gain and Low Side Lobe Smart Antenna Array for IoT Applications on Human Monitoring ������������������������������������������������  267 Mihir Narayan Mohanty, Shaktijeet Mahapatra, Sarmistha Satrusallya, and Amit Kant Pandit  Planar Multiband Smart Antenna for Wireless Communication Applications��������������������������������������������������������������������������  285 B. Elizabeth Caroline, B. Neeththi Aadithiya, J. Jeyarani, and Abdul Rahim Sadiq Batcha Part VI Ultra-Wide-Band Antenna Design for Wearable Applications  Low-Profile Compact EBG Integrated Circular Monopole A Antenna for Wearable Medical Application��������������������������������������������������  301 Prasad Jones Christydass Sam, U. Surendar, Unwana M. Ekpe, M. Saravanan, and P. Satheesh Kumar Slot-Based Miniaturized Textile Antenna for Wearable Application����������  315 Pranita Manish Potey, Kushal Tuckley, and Anjali Thakare Terahertz Antenna Technology for Detection of Explosives and Weapons: A Concise Review��������������������������������������������  331 A. Praveena, V. A. Sankar Ponnapalli, and G. Umamaheswari Part VII Microstrip Antenna Design for Various and Miscellaneous Applications  Determination of Moisture Content from Microstrip Moisture Sensor with Minimum Mean Relative Error��������������������������������  345 Sweety Jain Configurable OPFET-Based Photodetector for 5G Smart Antenna Applications ��������������������������������������������������������������  359 Jaya V. Gaitonde and Rajesh B. Lohani  Bandwidth Optimization of a Novel Slotted Fractal Antenna Using Modified Lightning Attachment Procedure Optimization����������������  379 Rohit Anand and Paras Chawla

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 Design and Fabrication of Axially Corrugated Gaussian Profiled Horn Antenna������������������������������������������������������������������������������������  393 Prashant D. Sachaniya, Jagdishkumar M. Rathod, and Utkal Mehta  Antipodal Vivaldi Antennas Arranged in Circular Array for RADAR������  405 Sasmita Mohapatra Index������������������������������������������������������������������������������������������������������������������  415

About the Editor

Praveen Kumar Malik  is a professor in the School of Electronics and Electrical Engineering, Lovely Professional University, Phagwara, Punjab, India. He received his B.Tech. in 2000, M.Tech. (Honors) in 2010, and Ph.D. in 2015 with specialization in wireless communication and antenna design. He has authored or coauthored more than 40 technical research papers published in leading journals and conferences by the IEEE, Elsevier, Springer, and Wiley. Some of his research findings are published in top cited journals. He has also published three edited/authored books with international publishers. Dr. Malik has guided several M.E./M.Tech. and Ph.D. students. He is associate editor of different journals. His current interest includes micro-strip antenna design, MIMO, vehicular communication, and IoT. He has been as guest editor/editorial board member of many international journals, invited keynote speaker at many international conferences in Asia, and invited program chair, publications chair, publicity chair, and session chair at many international conferences. Dr. Malik has been granted two design patents, and few more are in the pipeline. Joan  Lu  is in the Department of Computer Science and is the research group leader of Information and System Engineering (ISE) at the Centre for High Intelligent Computing (CHIC), having previously been team leader in the IT department of Charlesworth Group publishing company. She successfully led and completed two research projects in the area of XML database systems and document processing in collaboration with Beijing University. Both systems were deployed as part of company commercial productions. Professor Lu has published seven academic books and more than 200 peer-reviewed academic papers. Her research publications have 1388 reads and 185 citations by international colleagues, according to incomplete statistics from the research gate. Professor Lu has acted as the founder and a program chair for the International XML Technology Workshop for 11 years and serves as chair of various international conferences. She is the founder and editor-in-chief of the International Journal of Information Retrieval Research and serves as a BCS examiner of Database and Advanced Database Management Systems, and is an FHEA. She has been the UOH principle investigator for four xiii

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About the Editor

recent EU interdisciplinary (computer science and psychology) projects: Edumecca (student responses system) (143545-LLP-NO-KA3-KA3MP), DO-IT (multilingual student response system) used by more than 15 EU countries (2009-1-NO1-­ LEO05-01046), and DONE-IT (mobile exam system) (511485-LLP-1-2010-NO-­­ KA3-KA3MP), HRLAW2016 - 3090 / 001 - 001. B.  T.  P.  Madhav  was born in Andhra Pradesh, India, in 1981. He received his B.Sc., M.Sc., MBA, and M.Tech. degrees from Nagarjuna University, A.P, India, in 2001, 2003, 2007, and 2009, respectively. He received his Ph.D. in the field of antennas from KLEF. Currently he is working as professor and associate dean at KLEF. He has published more than 496 papers in international and national journals and conferences. He has a Scopus and SCI publications of 336 with H-Index of 32 and total citations are more than 3842. Madhav is reviewer for several international journals by IEEE, Elsevier, Springer, Wiley, and Taylor and Francis and has served as reviewer for several international conferences. His research interests include antennas, liquid crystals applications, and wireless communications. He is a member of IEEE and life member of ISTE, IACSIT, IRACST, IAENG, and UACEE, and fellow of IAEME. Madhav has received several awards, such as record holder in the Indian Book of Records and Asian Book of Records, outstanding reviewer award from Elsevier, and best researcher and distinguished researcher awards from K L University. He has received best teacher award from KLU for 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, and 2019; excellent citation award from IJIES; and outstanding faculty award from Venus International; and many more. Madhav is the editorial board member for 46 journals. He has authored 15 books and published 12 patents. He has guided three Ph.D. scholars for awards, three of his Ph.D. scholars submitted their theses, and six scholars are pursuing Ph.D. Swetha Amit  received her Ph.D. in electronics engineering from Jain University, Bangalore, in 2018; M.Tech. in communication systems from R.  V. College of Engineering, Bangalore, securing gold medal in 2009; and B.E. from AIT, Chikmagalur, in 2005. She is presently working as assistant professor in the Department of Electronics and Telecommunication Engineering, M S Ramaiah Institute of Technology, Bangalore. Her research work is on antenna design, wearable and textile antenna, SAR analysis and reduction of radiation in human body, liquid antennas, and metamaterials. Dr. Amit was awarded first place jointly with a startup company Avgarde Systems Pvt Ltd for winning Defense India Startup Challenge (DISC 4) 2021. She has published over 35 articles in journals and conferences, has patents to her credit, and written book chapters, in addition to guest lectures. She has two ongoing government-funded projects with AICTE MODROBS and VGST K_FIST Level 2 for 50 Lakhs. Dr. Amit has several consultancy projects and a YouTube Channel “Antenna’s Enclave.”

About the Editor

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Geeta  Kalkhambkar  is working as a Ph.D. scholar in the Department of Electronics and Telecommunication at KLE Dr. MSSCET, Belagavi, India, and research and development head at Sant Gajanan Maharaj College of Engineering, Mahagaon, Maharashtra. Her research interest includes studies on multifrequency, ultra-wideband antennas computational electronics, fractal and slotted antennas, and miniaturized antennas for Internet of Things applications. She has contributed over eight research papers and published two books.

Part I

Overview and Introduction of Microstrip Antenna

Microstrip Antenna: An Overview and Its Performance Parameter Hirendra Das, Mridusmita Sharma, and Qiang Xu

1  Introduction Antennas are the most critical components in modern age for wireless communications. The first wireless electromagnetic system was demonstrated in 1886 [1], and in 1901, Marconi succeeded in sending signals over long distances from England to Newfoundland, Canada. In 1950, the idea of microstrip antenna was first introduced [2]; however, it took almost 20 years for researchers to practically realize the concept, thanks to the development of printed circuit board (PCB) in the 1970s [3]. The necessity for having antennas with low profile, low weight, low cost, easy integration into arrays and microwave-integrated circuits, or polarization diversity, encouraged the researchers to develop microstrip antennas [4, 5]. The compatibility of microstrip antennas with integrated electronics is very evident and is a great impetus to antenna designers particularly so, now that a large variety of new substrate materials are commercially available in the market. Unlike other antennas, microstrip patch antennas can be configured with either the transmitting or receiving modes of operations. The limitations of the original microstrip antennas such as narrow bandwidth, poor polarization purity, spurious feed radiation, limited H. Das (*) Department of Electronics and Communication Technology, Gauhati University, Guwahati, Assam, India e-mail: [email protected] M. Sharma Department of Electronics and Communication Engineering, Gauhati University, Guwahati, Assam, India Q. Xu Department of Engineering and Technology, University of Huddersfield, Huddersfield, UK e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 P. K. Malik et al. (eds.), Smart Antennas, EAI/Springer Innovations in Communication and Computing, https://doi.org/10.1007/978-3-030-76636-8_1

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power-handling capacity, and tolerance problems have been overcome by continuous research, design developments, and performance optimizations. This leads to the design of novel microstrip antenna configurations with accurate and versatile analytical models for the understanding of inherent limitation of microstrip antennas to satisfy increasingly stringent system requirements [6, 7]. The three main fundamental disadvantages of microstrip antenna are narrow bandwidth, low gain, and relatively large size. Among these three, narrow bandwidth is the most significant one and can be directly improved by increasing the substrate thickness. However, with increasing thickness of the substrate, the radiation power decreases [8]. Different ways are proposed by the researchers to improve the bandwidth of the antenna without compromising the radiation power, including impedance matching networks using stub [9, 10]; novel designs [11, 12]; using different shapes and sizes of shots on the patch or in the ground plane such as U, step U, half step U, and L-shaped rectangular microstrip antenna [13]; W-shaped patch antenna [14]; M-slot folded patch antenna [15]; microstrip antennas using magneto-dielectric substrate [16]; complementary rhombus resonator [17]; nanomaterial-based microstrip antenna [18]; etc. The low-­gain problem can be solved by using cavity backing, which eliminates the bidirectional radiation to provide higher gain compared to conventional microstrip antenna [19]. The large size of the microstrip antenna particularly at lower microwave frequencies is another limitation which could be addressed by inductive or capacitive loading techniques [20] to fabricate electrically small microstrip antenna. In some other studies, works are also reported on different composite metamaterial resonators and magneto-dielectric substrate-based microstrip antennas for size reduction. It is evident from the above discussion that continuous improvements and performance enhancement of microstrip antenna are ongoing to meet the demands of compact, highly efficient, lightweight, and low-cost devices. Lately, the demand of compact wireless designs has necessitated the importance of continuously size-­ decreasing configurations. Emerging novel nanomaterials could also play an important part in the development of next-generation microstrip patch antennas. However, it is important to have a balance among bandwidth, gain, and size of microstrip antenna. In this chapter, we will discuss the basic theory and different design and performance parameters of microstrip antennas followed by a state-of-the-art review of the recent trends in this area.

2  D  esign and Performance Parameters of Microstrip Antenna: An Overview Due to features like compact design, efficiency, high performance, lightweight, low cost, etc., microstrip patch antennas (MPA) have become common elements in modern transmit-receive systems. The microstrip antennas are often termed as microstrip patch antenna (MPA). The radiating elements and feed lines are usually photo etched on the dielectric substrate. The basic structure of a rectangular microstrip patch antenna is shown in Fig. 1a. Depending on the shape of the patch, the antenna

Microstrip Antenna: An Overview and Its Performance Parameter

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Fig. 1 (a) Schematic of a rectangular microstrip patch antenna (b) Shapes of microstrip patch element

may be square, rectangular, thin strip (dipole), circular, elliptical, triangular, or any other configuration as shown in Fig. 1b. The length “L” defines the resonant frequency of the antenna, and width “W” determines the radiation which in turn determines the bandwidth and gain of the antenna. There are many feeding methods which can be used in microstrip antennas. The traditional microstrip antennas have the impedance bandwidth of only a few percent and radiation pattern with omnidirection, which obviously does not meet the requirements of various wireless applications. To solve this problem, a variety of different design topologies have been used with different microstrip antenna element structures and different microstrip array arrangements to meet the requirements of ultra-wideband (UWB), high-gain, multi-polarized, and compact design.

2.1  Feeding Techniques Feeding techniques are one of the most important things to be considered while designing a microstrip antenna because many potential good designs have been rejected because of their bad feeding quality. The four most commonly used feeding techniques are microstrip line feed, coaxial feed, aperture coupling, and proximity coupling. The schematic diagram of the four types of feeding techniques is given in Fig. 2. Microstrip line feeding is the most widely used technique because of its simplicity in design and easy manufacturing process [21–23]. Figure 2a shows a patch with microstrip line feed from the side of the patch. This type of feeding is used in both single- and multi-patch (array) antennas. Coaxial feed which is also known as co-­ planner feed is one of the cheapest and simplest ways to couple power to the patch antenna through a probe. The N-coaxial connector is coupled to the ground plane, and the center connector of the cable is soldered to the patch as shown in Fig. 2b.

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Fig. 2  A schematic representation of different feeding techniques used in microstrip antenna

The coaxial feed connected at exactly 50 ohm does not require any external matching network for impedance matching. Proximity coupled, which is also known as electromagnetically coupled, microstrip feed is shown in Fig. 2c. Two different substrates with different dielectric constants are used at the top and bottom of this structure as ground plane. The patch is at the top, and the microstrip line is connected to the power source lying between the two substrates. The working principle is based on the capacitive behavior of the patch and the feed strip line which can be used for impedance matching of the antenna. This design is relatively complicated compared to the earlier two techniques. Figure  2d shows the aperture coupling mechanism used for microstrip antenna. A circular or rectangular aperture at the ground plane separates the upper substrate εr1 with the patch on it and the lower substrate εr2 which contains the microstrip feed line under it. A wider bandwidth can be achieved using this feeding technique with improved polarization purity. All the feeding techniques have their advantages and disadvantages and are used based on the requirements. A comparison between different parameters of the four feeding techniques can be seen in Fig. 3. From the pie chart, a comparison among return loss, bandwidth, and impedance of the four feeding techniques could be obtained. Microstrip feed provides balanced characteristics among the four, except the bandwidth. Aperture feed provides the best bandwidth, whereas return loss is maximum for coaxial feeding technique. The discussion and comparison of feeding techniques are very important as they affect important parameters of the microstrip antenna such as the bandwidth, patch size, VSWR, and return loss up to a great extent. Table  1 shows an overall comparison among the parameters of different feeding techniques.

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Fig. 3  Comparison of return loss, bandwidth, and impedance parameters of different feeding techniques Table 1  Parameters of different feeding techniques: a comparison Characteristic Bandwidth Return loss Impedance matching Reliability Resonant frequency VSWR Polarization

Microstrip feed 2–5% Less Easy Better More < 1.5 Poor

Aperture feed 21% Less Easy Good Least ~2 Excellent

Coaxial feed 2–5% More Easy Poor Less 1.4–1.8 Poor

Proximity feed 13% More Easy Good Highest < 1.23 Poor

2.2  Performance Parameters 2.2.1  Directivity and Gain The directivity of an antenna is defined as the ratio of the radiation intensity U in a given direction from the antenna to the radiation intensity averaged over all directions. Mathematically it can be represented as: Directivity ( D ) =

4π U Prd

(1)

Here, Prd is antenna input power. Gain can be defined as the directivity reduced by losses on the antenna structure. Losses are represented by radiation efficiency er (0 ≤ er ≤ 1). Mathematically:

Gain ( G ) = e r D



(2)

Continuous works are being reported by the researchers to enhance the directivity and gain of the MPA. A narrow bandwidth (BW) and unidirectional dual-layer

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microstrip patch antenna with small-sized design for specific use in security and military systems were designed in 2014 [24], where they have achieved a gain of 5.2 dB with directivity 7.6 dB by using a dual substrate layer of FR-4 of thickness of 1.6 mm. Another report proposed two MPA arrays with enhanced gains of 12.41 and 10.11 dB as compared to 5.06 dB of conventional microstrip antenna array [25]. In a recent study, enhancement of gain up to 5.54 dB was reported using proximity coupled MPA operating in 7.067GHz–7.40 GHz frequency range [26]. 2.2.2  Return Loss The return loss of MPA can be given by the measure of how properly the devices or lines are matched. For a mismatched load, the whole input power is not delivered to the load, and a fraction of the power is returned, which is termed as return loss. Mathematically it can be given by: R L ( dB) = 10 log10

Pin Prd

(3)

where RL → return loss in dB Pin → incident radiation Prd → reflected power. From Eq. 3, return loss can also be defined as the logarithmic ratio of the antenna input power from the transmission line to the antenna’s reflected power.



R L = 20 log10

SWR SWR − 1

(4)

Here, SWR is the standing wave ratio. Return loss is an important parameter to describe the quality of the MPA, and several studies can be found in this area [27–29]. 2.2.3  Radiating Pattern and Efficiency It is defined as the ratio of radiating power to the incident power of the antenna. The value of radiating efficiency lies between 0 and 1, and “d” is measured in terms of percentage (%). Mathematically it is given by: er =

Prd Pin

(5)

Here, er → radiating power. It is less than 100% due to the losses in the antenna.

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Fig. 4 (a) 3D Radiation pattern and (b) efficiency vs. frequency graph of a microstrip antenna

Antenna efficiency is given by the radiation efficiency multiplied by the impedance mismatch, which is always less than the radiating efficiency. Researchers are continuously working to enhance the efficiency of MPA using different designs and other techniques, which can be found in various reports [30–33]. The 3D simulated radiation pattern and efficiency of a novel microstrip patch antenna designed at 1.84 GHz is shown in Fig. 4a and b, respectively. From the radiation pattern, it can be observed that the maximum gain for the microstrip antenna is 2.86 dB.

2.3  Microstrip Antenna Topologies: A Review of Literature A wide variety of MPA design topologies, along with different microstrip antenna element structures and array arrangements, have been investigated throughout the years by the researchers to achieve high gain and ultra-wideband operations. The lowest frequency for which microstrip antenna is designed and fabricated is 450 MHz, published in 2017 [34]. The highest-frequency microstrip antenna published till date is 60 GHz antenna reported in 2019 [35]. They measured a bandwidth of 4.92 GHz for this antenna that covers channels 2 and 3 of 60 GHz WLAN/ WPAN applications. A novel wideband quasi-Yagi microstrip antenna design with operating frequency in the range of 4.4–9.6 GHz and gain higher than 5 dB at most frequency band was reported [36]. Works are being reported on the design of a wideband planar microstrip-fed quasi-Yagi antenna using two rows of directors to achieve a higher gain [37]. This proposed structure results a frequency range of 1.84–4.59 GHz and a gain of about 4.5–9.3 dB. The current emerging wireless systems and radar applications require wide frequency bands, which encourages the researchers to design wideband antennas. In a recent study, researchers have proposed a compact high-gain quasi-Yagi antenna array using split-ring resonator (SRR) at an operating frequency of 2.45 GHz [38]. The SSR antenna could be used to suppress mutual coupling with possible high gain. Ground-plane slot microstrip antennas have the advantages of large bandwidth and good impedance matching [39]. Works are also being proposed by researchers

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on combining different types of MPA and frequency selective surfaces (FSSs) to enhance certain antenna characteristics [40, 41]. Researchers have also used FSS superstrate layer to increase the impedance bandwidth as well as the gain of an aperture coupled microstrip patch antenna [42]. Other significant works and recent developments are also being reported on the use of microstrip antennas for broadband applications [43, 44], mobile and satellite 5G communication [45, 46], radiofrequency identification [47], WLAN/WiMAX applications [48], automobile application [49], and so on. In recent times, researchers are also exploring the idea of nanomaterial and low-­ dimensional structure-based efficient microstrip antenna for a wide range of applications. Tools like physical vapor deposition (PVD) and chemical vapor deposition (CVD) can be used to deposit the required amount of conductive patch material on the dielectric substrate instead of the conventional lithographic process or removing the unwanted metal from a dielectric substrate. Nano-thin films as radiating patch used to fabricate aperture coupled microstrip patch antenna (ACMPA) by researchers were reported in 2012 [50]. A nanotechnology-based proximity coupled patch antenna in the X band frequencies was reported in 2013 [51]. They have discussed the effect of nano-thin films as radiating patch on the antenna resonant frequency and bandwidth. Nano-fillers such as fumed silica and aluminum oxide were used with RT/duroid 5880 to fabricate antenna substrates with compact dimensions [52]. Silver nanoparticles are used to fabricate flexible microstrip antenna using a polymer substrate [53]. An inkjet printer was used to print the antenna using the silver nanoparticles. The said antenna is flexible and weighs only 0.208 g, which makes it suitable for applications in wearable electronic devices. Works are also reported on the use of carbon nanotube-based patch for microstrip antenna design to enhance the gain of the system [54]. The reported multi-walled carbon nanotube (MWCNT)based microstrip patch antenna was fabricated using spin coating technique operating in the frequency range of 8.5–11 GHz, which exhibits an increased impedance bandwidth of 20%. In a recent study, researchers have reported investigation of graphene-based microstrip radiating structure for possible use in L- and S-band applications [55]. They obtained a multiband and tunable frequency response by changing the reflection coefficient by varying the chemical potential of graphene. The designed antenna showed the highest gain of 9.42 dB at a resonance frequency of 3.25 GHz.

3  Design Parameters of Microstrip Antenna The performance of MPA depends on different design parameters. One major design parameter is the choice of the substrate. Substrate dielectric constant and thickness are two major parameters for the selection of substrate. A few popular substrates for MPA with the most pertinent parameters, such as substrate name, thickness, dielectric constant, frequency range, and loss tangent, are given in Table 2.

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Table 2  Different substrates with most pertinent parameters Substrate Duroid 5880 RO 3003 RO 3010 RO 4350 HK 04 J IS 410 FR4 DiClad 870 RF-60A NH 9320 Polyguide

Thickness (mm) Dielectric constant (εr) 0.127 2.20 1.575 3.00 3.175 10.2 0.168 3.48 0.025 3.50 0.05–3.2 0.10 0.05–100 4.70 0.091 2.33 0.102 6.15 3.175 3.20 0.102 2.32

Frequency (GHz) 0–40 0–40 0–10 0–10 0.001 5.40 0.001 0–10 0–10 0–10 0–10

Loss tangent (tanδ) 0.0009 0.0010 0.0022 0.0037 0.0050 0.0350 – 0.0013 0.0038 0.0024 0.0005

Apart from the abovementioned substrates, many others are also present in the market. From the above, RO series along with FR4 is very popular for microstrip antenna design. The bandwidth of the antenna related to the material substrate is given by the following equation: 96 BW ≅

µr

t ε r λ0

2  4 + 17 µr ε r 

(6)

where “t” is the thickness of the substrate and “λ0” is resonance frequency wavelength. The term µ r ε r is known as miniaturization factor or refractive index, which determines the size of the antenna. The dimensions of the patch (length and width) are also vital for antenna performance. “W” is always related to the radiation edge, whereas “L” is always related to the non-radiating edge. The width for an efficient radiator is given by:



c  εr +1  W= 2 fr  2 

−1

2

(7)

where c → velocity of light fr → antenna operating frequency εr → dielectric constant. The length of the patch is given by: L=

c 2 fr ε e

− 2 ∆l (8)

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Here, εe is the effective dielectric constant, and Δl represents the line extension at the ends given by Hammerstad as: ∆l = 0.412 h

( εe + 0.3) ( w / t + 0.264 ) ( εe − 0.258 ) ( w / t + 0.8 ) (9)

where “t” is the substrate thickness.

4  Conclusions A brief overview of microstrip antenna with different performance and design parameters is provided in this chapter. From the above discussion, it can be observed that using different substrates and feeding techniques and controlling the performance parameters, MPAs can be designed with different topologies and structures to meet the modern-day requirements such as high flexibility, high gain and bandwidth, compact, lightweight, and low cost. A state-of-the-art literature review is also included in the chapter to outline the continuous research development works in this field and future prospects for these structures. It is also observed from the study that extensive works are ongoing nanomaterial-based microstrip antennas, which are showing promising improvements in recent years. These new classes of materials could be a game changer for developments of next-generation microstrip antennas.

References 1. Hertz, H.R.: Ueber sehr schnelle electrische Schwingungen. Ann. Phys. 267(7), 421–448 (1887) 2. Deschamps, G.A.: Microstrip microwave antennas. In: Proceedings of the 3rd USAF Symposium on Antennas (1953) 3. Byron, E.V.: A new flush-mounted antenna element for phased array application. In: Proceedings of the Phased Array Antenna Symposium-1970, pp. 187–192 (1970) 4. Carver, K.R., Mink, J.W.: Microstrip antenna technology. IEEE Trans. Antennas Propag. 1(1), 2–24 (1981) 5. Pozar, D.M.: Microstrip antennas. Proc. IEEE. 80(1), 79–91 (1992) 6. Balanis, C.A.: Antenna theory: a review. Proc. IEEE. 80(1), 7–23 (1992) 7. Ranjan, P.: A new approach for improving the bandwidth of microstrip patch antenna. In: 2nd International Conference on Micro-Electronics and Telecommunication Engineering, pp. 122–125 (2018) 8. Pozar, D.M.: Microstrip antennas. Proc. IEEE. 80(1), 79–91 (1992) 9. Pozar, D.M., Kaufman, B.: Increasing the bandwidth of a microstrip antenna by proximity coupling. Electron. Lett. 23(8), 368–369 (1987) 10. Pues, H.F., Van de Capelle, A.R.: Impedance-matching technique for increasing the bandwidth of microstrip antennas. IEEE Trans. Antennas Propag. 37(11), 1345–1354 (1989) 11. Kamakshi, K., Singh, A., Aneesh, M., Ansari, J.A.: Novel design of microstrip antenna with improved bandwidth. Int. J. Microw. Sci. Technol. 2014, 659592, 7 pages (2014)

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12. Keskin, U., Döken, B., Kartal, M.: Bandwidth improvement in microstrip patch antenna. In: 8th International Conference on Recent Advances in Space Technologies (RAST), Istanbul, pp. 215–219 (2017) 13. Deshmukh, A.A., Kumar, G.: Compact broadband U-slot-loaded rectangular microstrip antennas. Microw. Opt. Technol. Lett. 46(6), 556–559 (2005) 14. Joshi, N.K., Upadhye, P.A.: Microstrip patch antenna with W-shape slot using dual dielectric substrates. In: 2019 2nd International Conference on Communication Engineering and Technology (ICCET), Nagoya, Japan, pp. 121–124 (2019) 15. Jolani, F., Dadgarpour, A.M., Hassani, H.R.: Compact M-slot folded patch antenna for WLAN. Prog. Electromagn. Res. Lett. 3, 35–42 (2008) 16. Zaid, J., Farahani, M., Denidni, T.A.: Magneto-dielectric substrate-based microstrip antenna for RFID applications. IET Microw. Antenna Propag. 11(10), 1389–1392 (2017) 17. Tao, L., Xu, J., Li, H., Hao, Y., Huang, S., Lei, M., Bi, K.: Bandwidth enhancement of microstrip patch antenna using complementary Rhombus resonator. Wirel. Commun. Mob. Comput. 2018, 6352181, 8 pages (2018) 18. Mahesh, C.P., Shaikh, M.M., Sharon, M., Sharon, M.: Zinc nanoparticles loaded rectangular microstrip antenna for multiband operation. Int. J. Res. Appl. Sci. Eng. 6(5), 261–264 (2018) 19. Yuan, Y., Si, L.-M., Liu, Y., Lv, X.: Integrated log periodic antenna for Terahertz applications. In: International Conference on Microwave Technology and Computational Electromagnetics, pp. 276–279 (2009) 20. Azadegan, R., Sarabandi, K.: A novel approach for miniaturization of slot antennas. IEEE Trans. Antennas Propag. 51(3), 421–429 (2003) 21. Wang, H., Huang, X.B., Fang, D.G., Han, G.B.: A microstrip antenna array formed by microstrip line fed tooth-like-slot patches. IEEE Trans. Antennas Propag. 55, 1210–1214 (2007) 22. Sung, Y.: A printed wide-slot antenna with a modified L-shaped microstrip line for wideband applications. IEEE Trans. Antenna Propag. 59, 3918–3923 (2011) 23. Sung, Y.: Bandwidth enhancement of a microstrip line-fed printed wide-slot antenna with a parasitic center patch. IEEE Trans. Antennas Propag. 60, 1712–1217 (2012) 24. Mekki, A.S., Hamidon, M.N., Ismail, A., Alhawari, A.R.H.: Gain enhancement of a microstrip Patch antenna using a reflecting layer. Int. J. Antenna Propag. 2015, 975263, 7 pages, (2015) 25. Prahlada Rao, K., Vani, R.M., Hunagund, P.V.: Planar microstrip patch antenna array with gain enhancement. Procedia Comput. Sci. 143, 48–57 (2018) 26. Saxena, S., Saxena, N.: Proximity coupled microstrip patch antenna for gain enhancement. In: 2020 International Conference on Advances in Computing, Communication & Materials (ICACCM), Dehradun, India, pp. 423–426 (2020) 27. Mohanna, S., Farahbakhsh, A., Tavakoli, S., Ghassemi, N.: Reduction of mutual coupling and return loss in microstrip array antennas using concave rectangular patches. Int. J. Microw. Sci. Technol. 2010, 297519, 5 pages (2010) 28. Khinda, J.S., Tripathy, M.R., Gambhir, D.: Improvement in depth of return loss of microstrip antenna for S-band applications. J. Circuits Syst. Comput. 27(4), 1850058 (2018) 29. Nazari, M.E., Huang, W., Alavizadeh, Z.: Return loss-bandwidth evaluation for electrically small microstrip antennas. J. Electromag. Waves Appl. 34(16), 2220–2235 (2020) 30. Kim, Y., Lee, G.-Y., Nam, S.: Efficiency enhancement of microstrip antenna by elevating radiating edges of patch. Electron. Lett. 39(19), 1363 (2003) 31. Arya, A.K., Kartikeyan, M.V., Patnaik, A.: Efficiency enhancement of microstrip patch antenna with defected ground structure. In: 2008 International Conference on Recent Advances in Microwave Theory and Applications (2008) 32. Nahas, M.M., Nahas, M.: Bandwidth and efficiency Enhancement of rectangular patch antenna for SHF applications. Eng. Technol. Appl. Sci. Res. 9(6), 4962–4967 (2019) 33. Kamakshi, K., Singh, A., Aneesh, M., Ansari, J.A.: Novel design of microstrip antenna with improved bandwidth. Int. J. Microw. Sci. Technol. 2014, 659592, 7 pages, (2014) 34. Ahmed, Z., Yang, K., Evoy, P.M., Ammann, M.J.: Study of mm-wave microstrip patch array on curved substrate. In: Loughborough Antenna and Propagation Conference 2017 (LAPC ‘17), Loughborough, United Kingdom, November 13–14, 2017.

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35. Hock, G.C., Tho, N.T.N., Charabarty, C.K., Kiong, T.S.: Design of patch antennas array at low frequency application by using unknown FR4 material. J. Adv. Res. Dyn. Control Syst. 11(7), 510–524 (2019) 36. Jiang, K., Guo, Q.G., Huang, K.M.: Design of a wideband quasi-Yagi microstrip antenna with bowtie active elements. In: 2010 International Conference on Microwave and Millimeter Wave Technology, Chengdu, pp. 1122–1124 (2010) 37. Wang, H., Liu, S.-F., Li, W.-T., Shi, X.-W.: Design of a wideband planar microstrip-Fed Quasi-­ Yagi antenna. Prog. Electromagn. Res. Lett. 46, 19–24 (2014) 38. Zhou, W., Lu, M.: Miniaturization of Quasi-Yagi antenna array with high gain using split-ring resonators. Int. J. Antenna Propag. 2020, 4915848, 12 pages, (2020) 39. Le, T.T., Tran, H.H., Park, H.C.: Simple-structured dual-slot broadband circularly polarized antenna. IEEE Antenna Wirel. Propag. Lett. 17(3), 476–479 (2018) 40. Kurra, L., Abegaonkar, M.P., Basu, A., Koul, S.K.: fss properties of a uniplanar ebg and its application in directivity enhancement of a microstrip antenna. IEEE Antenna Wirel. Propag. Lett. 15(1), 1606–1609 (2016) 41. Abadi, S.M.A.M.H., Behdad, N.: Wideband linear-to-circular polarization converters based on miniaturized-element frequency selective surfaces. IEEE Trans. Antenna Propag. 64(2), 525–534 (2016) 42. Pirhadi, A., Bahrami, H., Nasri, J.: Wideband high directive aperture coupled microstrip antenna design by using a FSS superstrate layer. IEEE Trans. Antenna Propag. 60(4), 2101–2106 (2012) 43. Godaymi, W.’i.A., Shaaban, R.M., Al-Tumah, Tahirand, A.S., Ahmed, Z.A.: Multi-forked microstrip patch antenna for broadband application. J. Phys. Conf. Ser. 1294, 022020 (2019) 44. Ali, Z.J.: A printed microstrip patch antenna Design for ultra wideband applications. Int. J. Sci. Res. 3(4), 422–424 (2014) 45. Rashmitha, R., Niran, N., Jugale, A.A., Ahmed, M.R.: Microstrip patch antenna design for fixed mobile and satellite 5G communications. Procedia Comput. Sci. 171, 2073–2079 (2020) 46. Tiwari, R., Sharma, R., Dubey, R.: Microstrip patch antenna array design analysis for 5G communication applications. Smart Moves J. Ijosci. 6(5), 1–5 (2020) 47. Deif, S., Olokede, S.S., Nosrati, M., Daneshmand, M.: Stepped-impedance slotted microstrip-­ fed patch antenna for on-metal radio frequency identification applications. Microw. Opt. Technol. Lett. 62(10), 3324–3332 (2020) 48. Sanskriti, T., Sakshi, K., Kumar, C.P.: Micro strip patch antenna for WLAN/WiMAX applications: a review. In: International Conference of Advance Research & Innovation (ICARI), January 19, 2020, 5 pages (2020) 49. Sumana, L., Florence, S.E.: Pattern reconfigurable microstrip patch antenna based on shape memory alloys for automobile applications. J.  Electron. Mater. 49, 6598–6610 (September 2020) 50. Urbani, F., Stollberg, D.W., Verma, A.: Experimental characterization of nanofilm microstrip antennas. IEEE Trans. Nanotechnol. 11(2), 406–411 (November 2011) 51. Patil, R.R., Vani, R.M., Hunagund, P.V.: Design and simulation of nanotechnology based proximity coupled patch antenna at X-band. Int. J. Adv. Res. Comput. Commun. Eng. 2(9), 3344–3348 (2013) 52. Thabet, A., El Dein, A.Z., Hassan, A.: Design of compact microstrip antenna by using new nano-composite materials. In: The 4th IEEE International Nano Electronics Conference, pp. 1–2 (2011) 53. Matyas, J., Slobodian, P., Munster, L., Olejnik, R., Urbanek, P.: Microstrip antenna from silver nanoparticles printed on a flexible polymer substrate. Mater. Today Proc. 4, 5030–5038 (2017) 54. Chaya Devi, K.S., Angadi, B., Mahesh, H.M.: Multiwalled carbon nanotube-based patch antenna for bandwidth enhancement. Mater. Sci. Eng. B. 224, 56–60 (2017) 55. Dhasarathan, V., Bilakhiya, N., Parmar, J., Ladumor, M., Patel, S.K.: Numerical investigation of graphene-based metamaterial microstrip radiating structure. Mater. Res. Express. 7, 016203 (2020)

A Compact Dual-Fed Self-Diplexing Antenna for Wireless Communication Application Alpesh Vala, Amit V. Patel, Rashmi Vaghela, Keyur Mahant, Hiren Mewada, Esraa Ali, and Biren Patel

1  Introduction Modern wireless communication system requires a multi-band antenna system with better performance in terms of gain, size, and isolation among the frequency band [1, 2]. The wireless device operated at different frequencies requires the dual-band antenna with high isolation between ports. To reduce the requirement of the diplexer, the idea of self-diplexing antenna is used nowadays. By reducing the required component, it results in a less-dense RF front-end as well as a lower cost. Various efforts are put by the researcher for the development of diplexer and triplexer antennas. A substrate integrated waveguide (SIW)-based self-triplexer antenna is proposed in [1]. Cavity-backed slot antenna concept is used for the realization of the antenna. A self-diplexer antenna concept using half-mode SIW (HMSIW) is proposed in [2]. A tunable self-diplexing patch antenna is proposed by [3], in which two U-shapes are etched on the radiating patch and fed by two ports. A. Vala · A. V. Patel (*) · R. Vaghela · K. Mahant Chandubhai S Patel Institute of Technology, Charotar University of Science and Technology (CHARUSAT University), Anand, Gujarat, India e-mail: [email protected]; [email protected]; keyurmahant.ec@ charusat.ac.in H. Mewada Electrical Engineering Department, Prince Mohammad Bin Fahd University, Al Khobar, Saudi Arabia e-mail: [email protected] E. Ali Aviation Science Faculty, Amman Arab University, Amman, Jordan B. Patel General Dynamics Mission System, Fairfax, VA, USA © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 P. K. Malik et al. (eds.), Smart Antennas, EAI/Springer Innovations in Communication and Computing, https://doi.org/10.1007/978-3-030-76636-8_2

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A multilayer patch antenna with additional filtering techniques to improve the port’s isolation is given in [4, 5]. A nonplanar self-diplexing antenna is proposed in [6, 7]. A self-diplexing patch antenna design based on slot antenna concept is proposed in this paper. A circular patch is divided into two parts, with the slot on the top plane. Rectangular and tilted shape slots are created on top of the patch, excited by two separate feed lines to resonate at two different frequencies in S-band 2.4 GHz (2–4 GHz) and C-band 4.3 GHz (4–8 GHz). A high return loss and better isolation between two input ports are achieved by properly optimizing the antenna dimensions.

2  Realization of Self-Diplexing Antenna To realize the self-diplexing antenna, initially, a circular patch antenna is designed for the cutoff frequency of 2.4 GHz. Equation 1 is used to calculate the diameter of the patch. Inset type of feeding is used in a proposed antenna. Figure 1a shows the patch antenna design with its associate dimension. Simulation is carried out with the high-frequency structure simulator (HFSS) software which used the finite element method. Simulation result of the structure for return loss is shown in Fig. 1b. It provides resonance at 2.4 GHz of frequency. a=

F=

F 1   2 2h   πF   1 +  + 1.7726    ln    πε ϒ F   2h   8.791 × 10 9

fr ε r

(1)



Here in Eq. 1, a is the patch’s radius, εr is the dielectric constant, fr is the resonance frequency, and h is the height of the substrate. Fr4 is used as a substrate material having a dielectric constant of 4.4. For the realization of the self-diplexing antenna, the above structure is divided into two parts, as shown in Fig. 2. Dimensions of Fig. 2 are tabulated in Table 1. Separate excitation is provided to both positions, as shown in Fig. 2. For the realization of the antennas, two rectangle type slots are provided in the first part. In the second part of the antenna, the tilted type of slots is introduced. A detailed dimension of the proposed antenna is tabulated in Table 1. A simulated S-parameter result of the proposed antenna is shown in Fig. 3. It shows that it provides the resonance at 2.4 GHz of frequency when the excitation is provided at port 1 and resonates at 4.3 GHz of frequency while the excitation is at the port 2. Isolation among the port is near 20 dB, as shown in Fig. 3. Figure 4 indicates the simulation result of the radiation pattern and gain at the required frequency of operation. It provides 3.26 dBi gain at 2.4 GHz of frequency and 3.72 dBi at 4.3 GHz of frequency. A 3D polar plot for the same is shown in Fig. 3.

A Compact Dual-Fed Self-Diplexing Antenna for Wireless Communication Application

17

Fig. 1 (a) Circular patch antenna (b) Simulated return loss

3  Hardware Realization For the proof of concept, the proposed structure is fabricated and tested. Figure 5a shows the realized hardware of the proposed design. Agilent RF analyzer N9912A is used for the measurement. It is a two-port network analyzer with a frequency range of 2 MHz–6 GHz. A test setup for the same is shown in Fig. 5b. A measured result of the realized structure is shown in Fig. 6. It indicates a similar performance as a simulated one. A comparison has been carried out of the proposed antenna with previously published diplexer antennas in size, resonance frequency, and gain. A comparison table for the same is tabulated in Table 2. The proposed structure provides small size and better gain.

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Fig. 2  Geometry of the self-diplexing antenna

Fig. 3  Reflection coefficient value of the proposed antenna

Table 1  Dimensions of self-diplexing antenna Parameters

Value

Height of patch h (mm) 1.6

Wf1 and Wf (width of the microstrip line) (mm) 3.05

Lf1 and Lf (length of the microstrip line) (mm) 24.76 and 21

S1,S2 (mm)

S3,S4(mm)

14.8, 1.5

10, 2

A Compact Dual-Fed Self-Diplexing Antenna for Wireless Communication Application

19

Fig. 4 (a) 3D polar plot of simulated proposed antenna at 2.4 GHz and 4.3 GHz (b) Radiation pattern of simulated proposed antenna at 2.4 GHz and 4.3 GHz

4  Parametric Analysis of the Proposed Structure Parametric analysis is carried out by changing the length and width of the slot. In this section, the effect of the length and width on the antenna performance is discussed. Initially, the length and width of the first antenna are changed. Figure 7a indicates the return loss value for different slot lengths, and Fig. 7b indicates the return loss value for different slot widths. The numerical value of the above analysis is tabulated in Tables 3 and 4. It shows that by changing the slot’s length, it is possible to optimize the resonance frequency. Here the length slot is varied from 8.00 mm to 11.0 mm. The corresponding results indicate that it is possible to change the resonance frequency from 2.4  GHz to 2.9  GHz. Similarly, the resonance frequency can be optimized by changing the width of the slot. Figure 8a and b indicates return loss value of various width and slot on antenna one. The numerical value of the above figure is tabulated in Tables 5 and 6. It shows that by changing the slot’s length, it is possible to optimize the return loss value of the resonance frequency. Here the length slot is varied from 12.00 mm to 15.0 mm.

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Fig. 5 (a) Realized structure of the proposed antenna (b) Measurement setup of the proposed antenna

Fig. 6  Measured return loss of the antenna

Table 2  Comparison of the proposed antenna with previously published work Reference [8] [9] [10] [11] Proposed antenna

Area 0.70 λ × 1.9 λ 0.42 λ × 0.85 λ 0.49 λ × 0.7 λ 0.65 λ × 1.04 λ 0.32 λ × 0.56 λ

Resonance frequencies (GHz) fr1,fr2 6.44, 7.09 5.1, 5.2 2.1, 2.5 3.9, 4.63 2.4, 4.3

Gain (dBi) fr1 fr2 3.1 2.78 2.02 2.96 1.96 2.97 3.82 4.23 3.26 3.72

A Compact Dual-Fed Self-Diplexing Antenna for Wireless Communication Application

Fig. 7  Return loss value by changing (a) length of the slot (b) width of the slot Table 3  Parametric analysis by changing the length of the slot Slot length (mm) Parameters

Frequency(GHz) Return loss (dB) Gain (dB)

11.0 2.57 −23 2.83

10.0 2.4 −28.9 3.26

9.00 2.78 −21.57 2.822

8.00 2.99 −18.57 2.87

Table 4  Parametric analysis by changing the width of the slot Slot width (mm) Parameters Frequency(GHz) Return loss (dB) Gain (dB)

1.0 2.57 −20.67 3.33

1.5 2.45 −24.72 2.71

2.0 2.4 −28.92 3.26

2.5 2.35 −22.92 3.14

Fig. 8  Return loss value by changing (a) width of the slot (b) length of the slot Table 5  Parametric analysis by changing the length of the slot Slot length(mm) Parameters Frequency (GHz) Return loss (dB) Gain (dB)

12.0 4.3 −21.25 3.609

13.0 4.3 −20.00 2.636

14.8 4.3 −21.00 3.722

15.0 4.3 −27.00 2.892

1.5 4.3 −21.00 3.722

2.0 4.3 −18.46 2.978

Table 6  Parametric analysis by changing the width of the slot Slot width(mm) Parameters

Frequency(GHz) Return loss (dB) Gain (dB)

0.5 4.3 −30.00 3.492

1.0 4.3 −31.45 2.636

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The corresponding results indicate that it is possible to change the return loss value of resonance frequency from 20  dB to 27  dB.  Similarly, the return loss value of resonance frequency can be optimized by changing the slot’s width.

5  Conclusion A compact, high-gain dual-fed self-diplexing antenna is designed and developed in this chapter. The structure is realized by dividing a circular patch antenna into two parts. Rectangular and tilted slots are placed on top of the structure to realize the dual-band response. HFSS software is used for the simulation of the design. The proposed design resonates at two frequencies, 2.4  GHz and 4.3  GHz, with more than 20 dB return loss. Sufficient isolation of 20 dB is achieved between two ports. Hardware is developed to prove the concept; the measured result of the proposed structure is quite similar to the simulated one. Parametric analysis is carried out to tune the resonance frequency and to achieve a better return loss.

References 1. Vala, A., Patel, A.: A multi-band SIW based antenna for wireless communication. Int. J. Electron. Lett. 9, 1–9 (2020) 2. Vala, A., Patel, A.V., Mahant, K., Chaudhari, J., Mewada, H.K.: HMSIW-and QMSIW-based antenna for wireless communication application. Circuit World. (2021) 3. Boukarkar, A., Lin, X.Q., Jiang, Y., Yu, Y.Q.: A tunable dual-fed self-diplexing patch antenna. IEEE Trans. Antennas Propag. 65(6), 2874–2879 (2017) 4. Montero de Paz, J., Muñoz, E.U., Martínez, F.J.H., Posadas, V.G., Muñoz, L.E.G., Vargas, D.S.: Multifrequency self-diplexed single patch antennas loaded with split ring resonators. Prog. Electromagn. Res. 113, 47–66 (2011) 5. Herraiz-Martinez, F.J., Ugarte-Munoz, E., Gonzalez-Posadas, V., Garcia-Munoz, L.E., Segovia-Vargas, D.: Self-diplexed patch antennas based on metamaterials for active RFID systems. IEEE Trans. Microw. Theory Tech. 57(5), 1330–1340 (2009) 6. Boyle, K.R., Udink, M., de Graauw, A., Ligthart, L.P.: A dual-fed, self-diplexing PIFA and RF front-end. IEEE Trans. Antennas Propag. 55(2), 373–382 (2007) 7. Chang, C.-C., Row, J.-S.: Dual-feed dual-polarized patch antenna with low cross polarization and high isolation. IEEE Trans. Antennas Propag. 57(10), 3405–3409 (2009) 8. Luo, G.Q., Hu, Z.F., Dong, L.X., Sun, L.L.: Planar slot antenna backed by substrate integrated waveguide cavity. IEEE Antenna Wirel. Propag. Lett. 7, 236–239 (2008) 9. Herraiz-Martinez, F.J., Ugarte-Munoz, E., Gonzalez-Posadas, V., Garcia-Munoz, L.E., Segovia-Vargas, D.: Self-diplexed patch antennas based on metamaterials for active RFID systems. IEEE Trans. Microw. Theory Tech. 57(5), 1330–1340 (2009) 10. Boukarkar, A., Lin, X.Q., Jiang, Y., Yu, Y.Q.: A tunable dual-fed self-diplexing patch antenna. IEEE Trans. Antennas Propag. 65(6), 2874–2879 (2017) 11. Nakano, M., Arai, H.I.R.O.Y.U.K.I., Chujo, W., Fujise, M.A.S.A.Y.U.K.I., Goto, N.: Feed circuits of double-layered self-diplexing antenna for mobile satellite communications. IEEE Trans. Antennas Propag. 40(10), 1269–1271 (1992)

Multiband Slot Microstrip Antenna for Wireless Applications Mehaboob Mujawar and T. Gunasekaran

1  Introduction: Background 4G internet networks are expected to have a data speed of 1  Gbps, while non-­ stationary networks will have a fixed data speed of 100 Mbps. Long-distance communication is possible only because of wireless communications and antenna being the main element of the system, which converts electric power into radio waves and vice versa. Wireless communication has seen an increase in the number of users, and there have been restrictions on available bandwidth, so commercial operators have large-capacity network with good-quality coverage. There are many merits which are associated with the use of MSA, for example, it’s possible to achieve antenna design which will provide more gain, compact design, narrow bandwidth, and low profile. The main requirements of an antenna to be used for commercial applications include impedance matching and bandwidth enhancement. There is a direct relation between antenna size and resonance frequency of the antenna. As the frequency increases, the size of the antenna becomes smaller. While designing MSA, we have to choose the shape of the patch and feeding method based on the desired applications. The performance of an antenna can be affected in many ways, due to different shapes of the antenna. Different dielectric substrates have varying dielectric constants which influence the antenna design parameters as well as antenna performance. There are different feeding techniques available to feed the antenna in order to allow it to radiate. The main motivation of this chapter is in the use of MSA, which provides a huge range of advantages in communication systems that have ultimately led to more demand of antennas for commercial purposes with M. Mujawar (*) Goa College of Engineering, Ponda, Goa, India T. Gunasekaran Higher College of Technology, Muscat, Oman © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 P. K. Malik et al. (eds.), Smart Antennas, EAI/Springer Innovations in Communication and Computing, https://doi.org/10.1007/978-3-030-76636-8_3

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more enhanced features like multiband, wider bandwidth, and low profile. Conventionally, there was a need for specific antenna for specific communication application, since the antenna used to operate on one or two frequencies. This has been a problem in the implementation of the antenna on the devices, since these antennas had occupied a lot of space on the device. To get rid of this problem, there was a need for a single antenna which could operate at wide bands of frequencies, which can be obtained using multiband antennas. One of the methods to obtain such antenna is by using defective ground plane and creating slots on the patch. Defected ground structure is a technique which helps to improve the operation of an antenna by purposely changing the ground-plane element of MSA.

2  Review of the Existing Techniques This paper [1] describes the MSA, which is rectangular in shape and can be operated on wide range of frequencies. The optimization of the antenna has been carried out for a wide range of frequencies, which shows the improvement in various parameters of the antenna. The gain of the antenna was increased along with the surface current by making four slots of L shape on the patch. The feeding technique used in this project was inset feedline; the substrate used was RT-duroid having dielectric constant of 2.2. The simulation software used for the project was CST. This paper [2] deals with MSA, which is compact and has slots that improve the performance of the antenna for a wide range of applications, including X-band and LTE. This antenna operates on a wide range of frequencies, having the substrate material FR4 with 4.4 dielectric constant. In this project, U- and Y-shaped slots were created on the patch for the antenna, which was kept under test. The feeding technique used in this project was inset feedline. The simulation software used for the project was CST. The antenna which was kept under test had resonated at 7.98GHz with −20 dB, 4.1 GHz with −13.7 dB, and 2.4 GHz with −21.3 dB return loss with frequencies, respectively. This paper [3] describes an antenna, which is specifically designed to operate in C-band and S-band. The main aim of this paper was to reduce the size of the antenna in comparison to other multiband antennas, and it was achieved. In order to operate on multiple frequency bands, this antenna utilized the technique of stubs. It had T- and E-shaped stubs, which helped to operate on multiple frequency bands and also reduced the size of the antenna. The software used in the project was HFSS. The main aim of this antenna was achieved, as it resonated at desired frequencies. This paper [4] deals with an antenna having fractal slots, which is operated at a frequency of 4.1 GHz. E shape has been mounted on the patch which is resonating at the center. FR4 has been selected as substrate, having a height of 2 mm. This antenna has been miniaturized with the slots, specifically of H and L shape, to about 60%, which has a wide range of applications such as in C-band, S-band, GPRS, GSM, and 4G.  In this paper [5], wideband antenna has been designed, which is operating in the frequency range of 800  MHz–9  GHz. this ensures that antenna can be operated in almost ten bands. For the construction of

Multiband Slot Microstrip Antenna for Wireless Applications

25

antenna, inverted F-, L-, and C-type shapes were used. The main outcomes of this antenna were the possibility to obtain a gain of 2 dB, reflection coefficient of less than −10 dB, and all the bands with a bandwidth of 3 dB. This paper [6] deals with antenna, which will be desired for 4G applications. It uses substrate material such as RT-duroid. The software used for antenna design is IE3D. It has been constructed using slots of L, Z, and U shape. Using this antenna, it was possible to achieve VSWR less than 2 and return loss to be −20 dB. This paper [7] deals with the construction and design of an antenna that is widely used for the transmission and reception of TV signals. The antenna structure with defected ground plane widely improves the overall performance of MSA. This antenna can be operated on multiple frequency bands, which includes C- and S-band frequencies. The substrate material used for the implementation of the antenna is FR4, with substrate thickness to be 1.7 mm and having a dielectric constant of 4.4. The antenna parameters have been analyzed using CST software. This paper [8] describes multiheaded starfish-­ shaped multiband microstrip patch antenna for satellite communication. This antenna could help us to achieve a reflection coefficient of less than −10  dB.  It could resonate at 9.13 GHz, 7.81 GHz, 10.18 GHz, and 3.04 GHz frequencies. This paper [9] describes a quad-band CPW-fed slot antenna array for LTE and WiMAX application. This antenna mainly consists of slot, which is tapered and etched on the antenna, so that it could support a wide range of frequencies (3.45, 2.6, 0.8, and 1.8 GHz), which operate on multiple frequency bands for different applications. It has a reflection coefficient of less than −10 dB, and simulated radiation patterns were omnidirectional, which is desired in case of mobile terminals. This paper [10] describes a modified planar inverted F antenna with triple-band for Wi-Fi and LTE applications. It provides a detailed study and implementation of the planar inverted F antenna. The construction of the antenna involves two L-shaped open and shared short arms. This antenna is designed taking into consideration various factors, which yield antenna having less reflection coefficient and omnidirectional radiation patterns with good gain, which operates on three different frequency bands that support LTE and Wi-Fi applications. This paper [11] describes the design of multiband microstrip patch antenna for WiMAX, C-band, and X-band applications. The feeding technique used in the construction of this antenna is microstrip feedline. The substrate material used in the construction of this antenna is FR4. The multiband characteristic created by two different slots employed on the radiating patch. This antenna covered three frequency bands: from 3.2 to 3.4 GHz for WiMAX, from 6.57 to 6.8 GHz for C-band applications, and from 7.24 to 7.57 GHz for X-band satellite communication. The provided return losses are better than −23 dB at 3.32 GHz, −15.74 dB at 6.67 GHz, and − 22.4 dB at 7.39 GHz. The VSWR is less than 2 at all operating resonance frequencies. This paper [12] describes a multiband PIFA with a slot on the ground plane for wireless applications. The software used for the optimization of the antenna is HFSS. Various parameters of the antenna have been analyzed by using HFSS. It was possible to obtain acceptable return loss over multiple frequency bands. This antenna was built using the substrate material of FR4. It basically describes PIFA antenna, whose parameters have been varied to obtain a suitable antenna for wireless applications. This paper [13] describes dual-band

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microstrip patch antenna. This antenna has been constructed using microstrip patch, which is square in shape and operating on dual frequencies. It is operating on C- and X-band. The simulation software used was HFSS. Using this software, it was possible to analyze various antenna parameters. It helped to obtain acceptable reflection coefficient for both the frequency bands and VSWR within the acceptable range for an ideal antenna, i.e., between 1 and 2. The frequencies at which the antenna resonated at both bands are 6.7, 6.4, and 7.3. This paper [14] describes compact triple C-shaped microstrip patch antenna for WLAN, WiMAX, and Wi-Fi application at 2.5 GHz. The software used for the antenna design is computer simulation technology microwave studio. The substrate material used for the construction of antenna is FR4. After obtaining the simulation results, it was analyzed that return loss was –10 dB, and VSWR was within the range of 1–2.

3  Antenna Design Considerations of Proposed Work This chapter proposes an inverted HE-shaped microstrip patch antenna for four different frequencies ranging from 2 to 8 GHz. It is designed on defective ground plane so as to increase the bandwidth. This antenna has been mainly designed to operate on multiple frequency bands, and the performance of the antenna with various substrates such as RT-duroid, FR4, and Rogers has been analyzed. Detailed analyses of antenna performance parameters like gain, directivity, return loss, and VSWR are obtained. The software used for the construction of the antenna is IE3D. The main objectives of the chapter are (a) to design a microstrip patch antenna using three different substrates, (b) to optimize the dimensions of the antenna to find the desired results, (c) to observe the results for individual antenna design, and (d) to compare the results of all the three designs.

4  Antenna Structure The overall structure of the antenna includes H- and E-shaped slots, which are basically in the inverted orientation. The performance of the antenna has been enhanced with the use of different substrates with fixed height. This antenna is constructed at four different frequencies to obtain the desired multiband characteristics within the frequency band for wireless applications. This antenna configuration mainly involves MSA and inverted HE slot, which helps to operate on multiple frequency bands. Patch antenna shown below is designed using FR4 with dimensions of [−W/2, W/2] and [−L/2, L/2] and the ground plane with dimensions as [−Wg/2, Wg/2] and [−Lg/2, Lg/2], where L is the length and W is the width of the patch, whereas Lg is the length and Wg is the width of the ground plane. The patch is cut on the substrate. The dimensions of the microstrip feedline are [−(Wf/2), (Wf/2)] and [−(Lf/2), (Lf/2)] (Figs. 1, 2, and 3).

27

Multiband Slot Microstrip Antenna for Wireless Applications 10mm 4mm 4mm 8mm

5mm

1mm

Fig. 1  Dimensions of HE slot with FR4 11mm

5mm

5mm 9mm

1mm 6mm

Fig. 2  Dimensions of HE slot with Rogers

The proposed antenna can be operated on multiple frequencies with the formation of inverted H- and E-shaped slots. The horizontal slots operate at 3–3.7 GHz. The vertical slot of the H shape operates at 4.5–5.5 GHz. The three vertical slots of E shape operate from 5.9 GHz to 6.3 GHz. With the introduction of defect in the ground plane, it leads to bandwidth enhancement. Mathematical analyses with the help of antenna design equations have been carried out to obtain the desired design.

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13mm 7mm

7mm 11mm

2mm 7mm

Fig. 3  Dimensions of HE slot with RT-duroid Table 1  Patch and the ground-plane dimensions Sr. no 1 2 3

Substrate FR4 Rogers 4350 RT-duroid

Patch length in mm (L) 29 31

Patch width in mm (W) 38 41

Ground-plane length in mm (Lg) 47 49

Ground-plane width in mm (Wg) 56 59

39

48

57

66

IE3D software has been used to analyze various antenna parameters, and optimization of the antenna helps to get the desired results. The antenna has been designed with three different dielectric substrates and analyzed for the frequency ranging from 2 GHz to 8 GHz. Substrate thickness is taken at a height of 3 mm for all three substrates. FR4, Rogers, and RT-duroid have dielectric constant of 4.4, 3.48, and 2.2 and loss tangent of 0.002, 0.02, and 0.0004, respectively (Table 1). Table 2 gives the remaining parameters of the designed antenna like slot width, slot length, and feedline.

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Multiband Slot Microstrip Antenna for Wireless Applications Table 2  Dimensions of the slot and feedline Parameters (mm) Wf Lf Ls Ws

FR4 16 4.59 30 39

Rogers 4350 19 5.71 32 42

RT-duroid 27 8.42 40 49

Fig. 4  Return loss of the proposed antenna with FR4 substrate

5  Results 5.1  Return Loss (dB) The return loss of the proposed antenna with FR4 substrate is shown in Fig. 4. The antenna resonates over four frequencies, i.e., 2.2  GHz, 3.3  GHz, 5.3  GHz, and 6.0 GHz. The return loss for all frequencies varies from −13 dB to −22 dB; the maximum value of return loss for this design is −21.22 dB. The simulated results of the antenna designed on Rogers 4350 substrate are shown in Fig. 5. The antenna resonates over four frequencies, i.e., 2.2 GHz, 3.6 GHz, 5.3 GHz, and 6.2 GHz. The return loss for all frequencies varies from −13 dB to −18 dB; the maximum value of return loss for this design is −17.48 dB at 2.2 GHz. Figure 6 shows the graph of return loss of an antenna designed on RT-duroid substrate. The antenna resonates over four frequencies, i.e., 2.2  GHz, 3.6  GHz, 5.3 GHz, and 5.9 GHz. The return loss for all frequencies varies from −14 dB to −26 dB. All frequencies achieve a high value of return loss, which means that this antenna radiates maximum power, for all the frequencies. Maximum return loss is achieved at −25.66 dB at 5.9 GHz.

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Fig. 5  Return loss of the proposed antenna with Rogers 4350

Fig. 6  Return loss of the antenna designed on RT-duroid

5.2  VSWR VSWR plays a very important role in determining the performance of the antenna. Antenna having VSWR within the range of 0–2 is considered to be a good design. The VSWR plot of an antenna designed on FR4 substrate is shown in Fig. 7. The minimum value of VSWR is 1.18, which is obtained at 6.0 GHz. Figure 8 shows the VSWR graph for an antenna designed on Rogers 4350 substrate. VSWR achieved for the frequencies 2.2 GHz, 3.6 GHz, 5.3 GHz, and 6.2 GHz are 1.32, 1.57, 1.82, and 1.43, respectively. Figure 9 shows the graph of VSWR, designed on RT-duroid substrate. The values of VSWR achieved for this design are 1.2, 1.5, 1.2, and 1.1 for the four different

Multiband Slot Microstrip Antenna for Wireless Applications

31

Fig. 7  VSWR of the antenna designed on FR4

Fig. 8  VSWR of the antenna designed on Rogers 4350

frequencies. These VSWR values are close to 1. Hence, we can say that the mismatch between the antenna and the feed is minimum. As can be seen in Table 3, return loss obtained for the antennas designed with different substrates is below –10 dB. Antenna with return loss below –10 dB is considered to be a perfect antenna desirable for wireless applications. When the antenna was designed using RT-duroid substrate and resonated at four different frequencies, the return loss was maximum. The antenna which was designed with FR4 offered minimum return loss.

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Fig. 9  VSWR of the antenna designed on RT-duroid Table 3  Return loss and VSWR Substrate FR4

Rogers 4350

RT-duroid

Frequency (GHz) 2.2 3.3 5.3 6 2.2 3.6 5.3 6.2 2.2 3.6 4.8 5.9

Return loss (dB) −13.53 −17.48 −14.18 −21.22 −17.11 −13.08 −10.74 −14.89 −18.38 −14.09 −19.84 −25.66

VSWR 1.57 1.31 1.4 1.18 1.32 1.57 1.82 1.43 1.2 1.5 1.2 1.1

The return loss value of the antenna using Rogers 4350 substrate was in between RT-duroid and FR4.The antenna designed with RT-duroid substrate also offered VSWR approximately equal to 1 for the desired range of frequencies. Table 4 gives the values of gain, directivity, and bandwidth. The maximum gain and directivity for FR4 is observed at 5.3GHz, which is 4.60 dBi and 6.39 dBi, respectively. The maximum bandwidth of 570 MHz is seen at 5.9 GHz. Antenna designed with RT-duroid has maximum values at a frequency of 3.6 GHz with a gain of 5.1 dBi, directivity of 5.55dBi, and bandwidth of 512 MHz. It is seen that Rogers 4350 has good gain and directivity compared to FR4 and RT-duroid, whereas greater bandwidth is achieved with RT-duroid.

Multiband Slot Microstrip Antenna for Wireless Applications

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Table 4  Gain, directivity, and bandwidth Substrate FR4

Rogers 4350

RT-duroid

Frequency (GHz) 2.2 3.3 5.3 5.9 2.2 3.6 5.3 6.2 2.2 3.6 4.8 5.9

Gain (dBi) 4.31 3.28 4.60 3.21 5.18 3.47 4.07 3.79 4.91 5.12 3.39 4.96

Directivity (dBi) 5.48 5.14 6.39 6.50 5.49 4.79 5.44 5.46 4.44 5.55 3.49 5.03

Bandwidth (MHz) 290 229 320 570 200 300 500 600 491 512 339 496

6  Conclusion The proposed antenna works on four different frequencies. This antenna has been designed with different substrate materials to enhance the performance of the antenna. The operation of this antenna on multiple frequency bands was possible with the introduction of H- and E-shaped slots on the microstrip patch. Bandwidth enhancement was possible with defected structures on the ground plane. The thickness of the substrate was kept constant throughout the design, and analyses of the antenna with different substrates were done. From the comparison of simulation results obtained for the antenna, it is clear that antenna designed with RT-duroid substrate offers better performance results. The antenna designed using RT-duroid substrate is more preferred because this antenna can offer good performance in terms of various antenna parameters such as bandwidth, VSWR, and return loss. Antenna can be designed with different patch shapes and different shapes of the slot so as to get better performance. Aperture coupled feed can be used as a feeding technique which can give very high bandwidth of about 21%.

References 1. Saxena, N.: Design and analysis of multi band ANTENNA for S and C band. IEEE Transactions on Advances in Computing, Communication Control and Networking, 978-1-5386-4119-4/18//$31.00 ©2018 IEEE 2. Ajay Dadhich, J.K., Deegwal, M., Sharma, M.: Multiband slotted microstrip patch antenna for TD-LTE, ITU and X-band applications. IEEE Transaction on Signal Processing and Integrated Networks, IEEE – 43488(c) (2018) 3. Indharapu, S.S., Abhishikth, M.B.: A multiband slot antenna for wireless communication. IEEE Transaction on Computing, Communication and Network Technologies, 978-1-5386-3045-7/18/$31.00 ©2018 IEEE 4. Mehr-e-Munir, Khalid Mahmood, Saad Hassan Kiani: E-shape multiband patch antenna for 4G, C-band and S-band applications. Int. J. Adv. Comput. Sci. Appl. 9(5) (2018)

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5. Snehalatha, T.K.A.C., Kumar, N.: Design of multiband planar antenna. IEEE Transactions on Antenna Innovations & Modern Technologies for Ground, Aircraft and Satellite Applications, 978-1-5386-0646-9/17/$31.00 ©2017 IEEE 6. Mishra, P.K., Sachdeva, V., Sharma, D., Gupta, S.D.: Multiband microstrip antenna for 4G mobile application. IEEE Transactions on Communication Systems and Network Technologies, 978-1-4799-1797-6/15 $31.00 © 2015 IEEE 7. Bhadouria, A.S., Kumar, M.: Multiband DGS based microstrip patch antenna for open satellite communication. IEEE Transaction on Advances in Engineering & Technology Research, 978-1-4799-6393-5/14/$31.00 ©2014 IEEE 8. Md. Sazzad Hossain, Md. Towsif Abir, Md. Hadiur Rahman Khan, Md. Tariqul Islam. Multiheaded starfish shaped multiband microstrip patch antenna for satellite communication. IEEE Transaction on Electrical and Computer Engineering, 978-1-5386-7482-6/18/$31.00©2018 IEEE 9. Elahi, M., Khan, R.: A Quad-Band CPW Fed Slot Antenna Array for LTE and WiMAX Application. Prog. Electromagn. Res. M. 61, 159167 (2017) 10. Mujawar, M.: Design and analysis of log-periodic dipole antenna as a proximity fuse antenna. In: 2020 International Conference on Industry 4.0 Technology (I4Tech), Pune, India, pp. 182–185, (2020). https://doi.org/10.1109/I4Tech48345.2020.9102636 11. Badr, S., Hamad, E.K.I.: Design of multiband microstrip patch antenna for WiMax, C-band and X-band applications. Aswan Eng. J. (AswEJ) 12. Hosseini, S.E., Member, IACSIT, Attari, A.R., Pourzadi, A.: A Multiband PIFA with a Slot on the Ground Plane for Wireless Applications. Int. J. Inf. Electron. Eng. (3, 4), 349–352 (2013) 13. Shamim Banu, A., Kavitha, R., Aayisha Siddika, R., Elakkiya, M., Kaovyaa, S.: Dual Band Microstrip Patch Antenna. Int. J. Eng. Res. Technol. (IJERT) ICONNECT – 2018 Conference Proceedings 14. Dutta, D., Hira, A., Asjad, F., Haider, T.I.: Compact triple C shaped microstrip patch antenna for WLAN, WiMAX & Wi-Fi Application at 2.5  GHz. IEEE Transaction, 978-1-4799-6399-7/14/$31.00 ©2014 IEEE

Effect of Encapsulating Materials on Monopole Antenna Performance for Underwater Communication Mehaboob Mujawar and T. Gunasekaran

1  Introduction It is realized that 70% of the Earth involves water, and the greatest merchandise transportation is finished over the sea; thus, sea communication is a critical part in everyday life. Truly a huge number of ships or other vessels are far away in the ocean. Consequently, dependable oceanic communications are considered to play an imperative part in sea operations [1]. Because of progression in unmanned autonomous vehicles, robots venture to every part of the ocean without any supervision or control from the administrator. There is a requirement for communication of information, which is gathered by these unmanned autonomous vehicles with the host ship or to a ground station, yet their correspondence over the ocean is affected by different variables, for example, at the point when the electromagnetic waves spread over the ocean surface, there exists reflection, dispersion, and diffraction [2]. This chapter deals with wireless communication of autonomous underwater vehicle (AUV) [3, 4] with a ground station or aboard a ship for 2.4 GHz band. A design of an elementary-enclosed Marconi antenna operating at 2.4  GHz is simulated in CADFEKO simulator, and the results are analyzed. Autonomous underwater vehicle (AUV) explores by submerging below the sea even when no instructions are provided by the administrator. AUVs have six degrees of freedom, namely, surge, sway, heave, roll, pitch, and yaw. AUVs have a vital part for a nation that has a vast sea area. AUV is broadly utilized for sea investigation and contour mapping and as a method for defense under the sea. Due to advancements in AUVs, they are utilized for various research and military tasks for their broad information-gaining M. Mujawar (*) Goa College of Engineering, Ponda, Goa, India T. Gunasekaran Higher College of Technology, Muscat, Oman © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 P. K. Malik et al. (eds.), Smart Antennas, EAI/Springer Innovations in Communication and Computing, https://doi.org/10.1007/978-3-030-76636-8_4

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capacities; this obtained information is sent to the host transport, which is basically the ship utilizing EM waves on the plane of the sea, yet the nature of the EM wave is corrupted due to the accompanying components which influence the transmission and reception of EM waves on the sea plane. Doppler shift plays a very important role in the transmission and reception of EM waves because a signal having a high frequency is affected by this mechanism due to movement of the sea, rough plane of the sea due to wind additionally affects the transmission and reception of the EM waves, distance communication is also affected by the reflection which is occurring above sea, and losses are due to interference at the sea level [5]. Various networks using sensors working on the plane of the ocean have been helplessly set up to send EM waves to various communication systems located near the plane of the ocean, close to level of the ocean, or when the seaside height is low [6]. When signals need to be transmitted over very long distances, line of sight is required by the signals, which need frequency to be very high. Additionally, changes in the boundary layer of the atmosphere cause signal reflections and straightforwardly affect wave behavior and propagation paths, resulting in blurring [7]. Thinking about marine condition, the state of the ocean, also taking into consideration cyclonic winds, has a very close impact on both the transmission and reception of EM waves on the plane of the ocean. The said impacts are explicitly an issue for significant distance communication (past several hundred meters or 2 or 3 km). One of the important plans is to relocate the autonomous unmanned vehicles and unmanned surface vehicles or main ship adjacently with a particular ultimate objective to improve the radio channel. This causes wastage of time as well as resources. For instance, fuel will be used more because the movement between the vehicles will be longer. Spacecraft interface association is a commonplace methodology that has a number of obstructions, including incomplete satellite inclusion by most structure frameworks with little impression, as well as tolerably high expenses and generally low information rate [8]. There is a significant improvement in the radio channel which is used for communication with the help of communication relays; however, it needs a raised stage to give adequate location. To relieve these problems, it is desirable to construct antennas specifically for autonomous unmanned vehicles, which relatively have more gain, resulting in transmission and reception of signals at greater separations of up to 100 m. The parameters of the antenna are restricted by the autonomous unmanned vehicles because the sizes of the autonomous unmanned vehicles are typically small. The antenna is covered using a covering material to protect it below the water surface whenever an autonomous unmanned vehicle navigates. Delrin is the typical covering material used because of its excellent performance in underwater application. There may be loss in signal quality because of this material; consequently in this research, distinctive material are utilized for embodying the antenna, and the best material for antenna is decided by considering the value, which is obtained by designing the antenna in simulation software FEKO. The antenna will be operating at a frequency band of 2.4 GHz.

Effect of Encapsulating Materials on Monopole Antenna Performance for Underwater…

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Table 1  Antenna covering materials used Sr. no 1 2 3 4 5 6 7

Material PET PETG ULTEM Hydex 301 Tecaform AH PVC Delrin

Dissipation factor 0.002 0.02 0.0015 0.025 0.001

Dielectric constant at 2.4 Ghz 3.74 2.64 4.07 3.74 4.07

Mass density kg/m3 1380 1380 1270 1200 1410

Water absorption 24 hours 0.1 0.2 0.25 0.19 0.18

0.0096 0.005

3.509 4.07

1100–1450 1410

0.02 0.25

2  Antenna Encapsulating Materials Used While picking the covering material for the embodiment of the antenna, several standards have been considered; before selecting the covering material, we need to make sure that the material can withstand critical conditions below the surface of the water as the autonomous unmanned vehicles can move somewhere below the sea surface without contorting or disfiguring. The material strength should be strong enough to bear the critical conditions, and it should be free from corrosion, since the vehicle can stay below water surface for weeks. In the below table, we have enlisted covering materials which are considered suitable for underwater applications (Table 1).

3  Antenna Design A basic monopole antenna [7, 8] is intended for a frequency of 2.4 GHz; the conducting rod is placed on the ground plane, which is circular; and its height and diameter are simulated for a frequency of 2.4 GHz. The antenna has been covered with the covering material whose length is 10 m. The investigation is accomplished for characteristics of its frequency and theta versus gain. The antenna which uses a covering material and also the antenna which does not use a covering material have been shown in Fig. 1. The wavelength of an antenna can be calculated as the ratio of the speed of light to the frequency [9]; as we already know, the antenna is operating at a frequency of 2.4  GHz. In order to calculate the diameter of the conducting ground plane, we need to take the ratio of thrice wavelength to twice. The height of the covering material for the antenna is now fixed, yet the width of the covering material is varied with respect to its position from the antenna for different covering materials listed in the table below, and analyzed values are noted.

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Fig. 1  Antenna structure (a) covering material not used. Antenna structure (b) covering material used

a

conducting rod 1 wavelength 4

ground plane

b monopole antenna

t d

encapsulation for monopole conducting ground plane

Frequency versus Gain when encapsulation thickness is 5 mm and it is placed at a distance 0 mm from monopole 4.5 4 3.5

delrin

gain in dB

3

hydex

2.5

PET

2

PETG

1.5

PVC

1

Tecaform

0.5

Ultem

0 2

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

3

Frequency in GHz

Fig. 2  Gain vs frequency chart for the different materials when the encapsulation of 5 mm thickness is placed 0 mm away from the monopole antenna

4  Results Figure 2 shows the gain vs frequency simulation result, when the encapsulation of 5 mm thickness is placed at a distance of 0 mm away from the monopole antenna for different materials. We can see that the highest gain at 2.4 GHz is for PET with a gain of 4.25537516 dB and the lowest is for PETG with a gain of 3.71669396 dB. PET encapsulation gives 0.53 dB gain more as compared to PETG.

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Frequency versus Gain when encapsulation thickness is 5 mm and it is placed at a distance 5 mm from monopole 4.5 4 3.5

delrin

gain in dB

3

hydex

2.5

PET

2

PETG

1.5

PVC

1

Tecaform

0.5

Ultem

0 2

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

3

Frequency in GHz

Fig. 3  Gain vs frequency chart for the different materials when the encapsulation of 5 mm thickness is placed 5 mm away from the monopole antenna

Figure 3 shows the gain vs frequency simulation result for when the encapsulation of 5 mm thickness is placed at a distance of 5 mm away from the monopole antenna for different materials. The highest gain at 2.4 GHz is for Tecaform with a gain of 3.97090007  dB, and the lowest gain is for Hydex with a gain of 3.82773938 dB. The difference between the gains from Tecaform encapsulation is only 0.14 dB; we can also see that more or less all the materials exhibit similar gain. Figure 4 shows the gain vs frequency simulation result when the encapsulation of 8 mm thickness is placed at a distance of 5 mm away from the monopole antenna for different materials. The highest gain at 2.4 GHz is for Tecaform with a gain of 4.00149462 dB, and the lowest gain is for Hydex with a gain of 3.62640553 dB. We can see that Tecaform encapsulation gives a 0.62 dB more gain compared to Hydex encapsulation. Figure 5 shows the gain vs frequency simulation result, when the encapsulation of 11  mm thickness is placed at a distance of 5  mm away from the monopole antenna, for different materials. The highest gain at 2.4 GHz is for PET with a gain of 3.84855183 dB, and the lowest gain is for PETG with a gain of 2.39470329 dB. The difference in the observed gain is very high for PET and PETG encapsulation about 1.45 dB, whereas all other encapsulation materials have gain similar to PET. Figure 6 shows the gain vs frequency simulation result, when the encapsulation of 5  mm thickness is placed at a distance of 10  mm away from the monopole antenna, for different materials. The highest gain at 2.4 GHz is for Tecaform with a gain of 4.07821083 dB, and the lowest gain is for PET with a gain of 3.96754903 dB. It can be seen that the gain difference between Tecaform encapsulation and PET is only 0.11 dB; we can also see that more or less all the materials exhibit similar gain.

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M. Mujawar and T. Gunasekaran Frequency versus Gain when encapsulation thickness is 8 mm and is placed at a distance 5mm from monopole 4.5 4 3.5

delrin

gain in dB

3

hydex

2.5

PET

2

PETG

1.5

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1

Tecaform

0.5

Ultem

0 2

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

3

Frequency in GHz

Fig. 4  Gain vs frequency chart for the different materials when the encapsulation of 8 mm thickness is placed 5 mm away from the monopole antenna

Frequency versus Gain when encapsulation thickness is 11 mm and is placed at a distance 5 mm from monopole 4.5 4 3.5

delrin

gain in dB

3

hydex

2.5

PET

2

PETG

1.5

PVC

1

Tecaform

0.5

Ultem

0 2

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

3

Frequency in GHz

Fig. 5  Gain vs frequency chart for the different materials when the encapsulation of 11 mm thickness is placed 5 mm away from the monopole antenna

Effect of Encapsulating Materials on Monopole Antenna Performance for Underwater…

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Frequency versus Gain when encapsulation thickness is 5 mm and it is placed at a distance 10 mm from monopole 4.5 4 3.5

delrin

gain in dB

3

hydex

2.5

PET

2

PETG

1.5

PVC

1

Tecaform

0.5

Ultem

0 2

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

3

Frequency in GHz

Fig. 6  Gain vs frequency chart for the different materials when the encapsulation of 5 mm thickness is placed 10 mm away from the monopole antenna

5  Conclusion As can be observed from the results, it has been clear that if we keep the separation between the covering material and the antenna fixed at a particular value, for example, around 5 mm from the antenna, and the covering material width is shifted for various covering materials, the antenna would have less gain, while the width of the covering material is more. As we practically know, the antenna will be mounted on the autonomous unmanned vehicles, which will be exploring below the plane of the sea. So antenna should be strong enough to withstand the strong winds and pressure created by the water under several critical conditions; so for this purpose, it will be very effective to have more width for the covering material. It is likewise seen from the software that the antenna will have more gain when the separation of the covering material from the antenna is less, that is, 0 mm, for the condition when the width of the covering material is fixed at 5  mm and the separation values between the antenna and covering material are different. When we compare the plots of gain vs frequency of the various covering materials, it is clear that antenna gain is more, that is, 4.25 dB, for the PET covering material when the separation between the antenna and PET was 0 mm.

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References 1. Yang, K., Roste, T., Bekkadal, F.: Channel characterization including path loss and Doppler effects with sea reflections for mobile radio propagation over sea at 2  GHz. In: Wireless Communications and Signal Processing (WCSP), International Conference (2010) 2. Dong, F., Lee, Y.H.: Non-Line-of-Sight Communication Links over Sea Surface at 5.5GHz. Microwave Conference Proceedings (APMC) (2011) 3. Zhang, Q., Yang, K., Shi, Y., Xidang: Oceanic Propagation Measurement in the Northern Part of the South China Sea. Yan School of Marine Science and Technology, OCEANS 2016  – Shanghai on, 10–13 April 2016 4. Mujawar, M.: Design and analysis of log-periodic dipole antenna as a proximity Fuse A tenna. In: 2020 International Conference on Industry 4.0 Technology (I4Tech), Pune, India, pp. 182–185 (2020). https://doi.org/10.1109/I4Tech48345.2020.9102636 5. Aboderin, O., Pessoa, L.M., Salgado, H.M.: Wideband dipole antennas with parasitic elements for underwater communications. OCEANS 2017  – Aberdeen, Aberdeen, pp.  1–6 (2017). https://doi.org/10.1109/OCEANSE.2017.8084865 6. Homer, D.P., Healey, A.J.: Use of artificial potential fields for UAV guidance and optimization of WLAN communications. 2004 IEEWOES, Centre for AUV Research Naval Postgraduate School, Monterey CA 93943 7. Pasya, I., Zali, H.M., Saat, M., Ali, M.T., Kobayashi, T.: Buffer layer configuration for wideband microstrip patch antenna for underwater applications. 2016 Loughborough Antennas & Propagation Conference (LAPC), Loughborough, pp.  1–5 (2016). https://doi.org/10.1109/ LAPC.2016.7807577 8. Inácio, S.I.: Antenna design for underwater radio communications. OCEANS 2016 – Shanghai, Shanghai, pp. 1–6 (2016). https://doi.org/10.1109/OCEANSAP.2016.7485705 9. Swetha, K., Jayasree, P.V.Y., Saradhi, V.: Orthogonal mode dual band MIMO antenna system for 5G smartphone applications using characteristic mode analysis. Circuit World, Vol. aheadof-print No. ahead-of-print (2021). https://doi.org/10.1108/CW-11-2020-0319

Parasitic Antennas for Current and Future Wireless Communication Systems: Trends, Challenges, and Emerging Aspects Roktim Konch, Sivaranjan Goswami, Kumaresh Sarmah, Kandarpa Kumar Sarma, and Nikos Mastorakia

1  Introduction Antennas are generally classified according to their physical structure or operating frequencies. Depending upon the structure, these are categorized as wire antennas, aperture [1] antennas, reflector antennas, lens antennas, microstrip antennas, and array antennas. Due to its unique radiation properties, these antennas are used in different applications. When input power is fed to an antenna, some power gets reflected back to the source, while the other part is transmitted through the antenna. In that transmission, some portions are lost due to conduction, while the remaining part of the power is radiated to the medium from the antenna. This radiation occurs from a radiating surface in the form of electromagnetic waves. Therefore, the radiating structure plays a crucial role in an antenna system; the radiating surface determines the antenna’s resonance frequency, gain, and polarization [2]. The parasitic element plays a crucial role in enhancing the efficiency of an antenna [3]. The parasitic element-based antenna design concept is very old. It was first proposed by H. Yagi and S. Uda in 1926, a very popular type of antenna called R. Konch (*) · S. Goswami · K. K. Sarma Department of Electronics and Communication Engineering, Gauhati University, Guwahati, Assam, India e-mail: [email protected]; [email protected]; [email protected] K. Sarmah Department of Electronics and Communication Technology, Gauhati University, Guwahati, Assam, India e-mail: [email protected] N. Mastorakia Technical University Sofia, Sofia, Bulgaria e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 P. K. Malik et al. (eds.), Smart Antennas, EAI/Springer Innovations in Communication and Computing, https://doi.org/10.1007/978-3-030-76636-8_5

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Yagi-Uda antenna. Yagi-Uda antennas consist of a parallel set of linear dipole radiators typically reflector, driven dipole, and directors. The reflector element is a little longer [4] than the driven dipole, whereas the directors are a little shorter. These combinations of elements opened a new era of antenna design. Parasitic elements are passive structures present in the radiating system and have an effect on the radiation of the system. Each of these elements absorbs and re-­radiates the radio waves from the driven element with a different phase, modifying the dipole’s radiation pattern. It is similar to an end-fire array, meaning that radiation pattern is along the axis of the array in the direction of director elements. The Yagi-Uda antenna is a widely used early radar system, television broadcasting system, etc. Micostrip antenna was proposed in 1952 as a solution for wireless communication through portable devices [5]. Various techniques have been reported for the improvement of microstrip antennas in terms of size reduction, diversity of the far-field radiation pattern, enhancing bandwidth up to ultra-wideband, and resonance at multiple frequencies. Some of the approaches include the use of modification geometry [6], multilayer substrate [7], introducing cut slots of various sizes and shapes on the ground plane or near the top of the active patch [8], etc. Currently, parasitic-based designs for high-performance and low-size antennas have attracted the attention of researchers around the world. A number of novel techniques have been proposed worldwide in the last few decades to enhance the performance of the antennas. Microstrip parasitic antennas have received wide attention in the past few decades due to their advantages such as steerable radiation patterns [9], multiband function [10], ultra-­wideband application [11], and polarization diversity [12], which can reduce the size [13], complexity [14], and cost of an antenna while improving the total performance of a communication system. A simple design of a parasitic element-based microstrip antenna structure is shown in Fig. 1. In [15], authors presented a simple patch antenna surrounded by a parasitic element that can broaden the resonance frequency of the antenna. It has been recognized as a pioneer work in the use of parasitic elements for designing antennas with tunable parameters. The planar version of the Yagi-Uda antenna is introduced in [16]. After that, many similar structures have been proposed by different researchers

Fig. 1  Simple microstrip patch antenna surrounded by parasitic elements

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[17]. Yet performance improvement is required for meeting the increasing demand of greater reliability. Nowadays, planer and stack parasitic element structures along RF switches [18] are extensively used in microstrip antennas. The switch parasitic antenna (SPA) is one of the most popular structures reported in the recent times. The key objective of the chapter is to provide a practical insight into the design and application of the parasitic block-based microstrip antennas. So far, a brief introduction to the trends and practices of parasitic element-based design of microstrip antenna has been covered. This is followed by a brief theoretical overview of the parasitic structures along with the analysis and several experimental techniques for the antenna characteristics reported by previous works. Electrically steerable passive array radiator antenna and its widely used parasitic structure are discussed. In this discussion, microstrip parasitic-based antenna design and its future perspective in terms of a new adaptable modern wireless communication system have been highlighted. Introducing reconfigurable intelligent surfaces and its future prospects in the next-generation wireless communication system is also discussed.

2  P  erformance Enhancement of the Microstrip Antenna by Using Parasitic Elements In this section, we discuss the different configurations of the parasitic elements and their contributions to performance improvement of the microstrip patch antenna. For the analysis of various antenna structures, each of the designs is categorized in terms of bandwidth enhancement, steerable radiation pattern, and parasitic element-­ based reconfigurable structures.

2.1  Bandwidth Enhancement The bandwidth (BW) of a microstrip antenna rises with the increase in thickness (h) or with a decrease in the dielectric constant (ε). However, increasing the thickness, surface wave propagation takes place, resulting in degradation in antenna performance. Therefore, parasitic coupling multiple resonator techniques using microstrip patches for broadband operation are preferred. Only one patch is fed. Further, the other patches are parasitically coupled. The coupling between the multiple resonators has been realized by either using a little gap [19] between the patches or directly connecting the patches through a thin microstrip line [20]. A patch closer to the active one gets excited through the coupling between the two patches. These are called parasitic patches. If the resonance frequencies f1 and f2 of these two patches are closer to each other, then broad BW is obtained as shown in Fig. 2 [21]. If the

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Fig. 2  VSWR plots of two coupled resonators having (a) BW (…) individual resonators and (---) overall response (b) A simple coaxial feed microstrip antenna

BW is narrow for the individual patch, then the combination of f1 and f2 results in broader BW. Based on the position of the parasitic element, it is divided into gap-coupled, direct-coupled, or hybrid-coupled [22]. In gap-coupled microstrip antennas, the structure is excited at the fundamental TM10 mode and has one λ/2 cycle variation in the field along its length and has uniform field along its width [21]. The edges along the width and length are correspondingly known as radiating and non-­ radiating edges [22–24] as shown in Fig. 3. Either one or two parasitic equal rectangular patches can be placed along one or both of the radiating edges of the fed rectangular patch with a small gap between them. The BW of the gap-coupled antenna can be increased further by choosing the parasitic patches of different sizes. In the non-radiating edges, the coupling between the parasitic elements is smaller as compared to the coupling along the radiating edges, because the field varies in the non-radiating edge in a sinusoidal pattern and is uniform along the radiating edges. In direct-coupled [25] approach, a thin microstrip line is connected in between the fed patch and parasitic patch. The strip is usually located at the midpoint of the widths of the patches, so the antenna is symmetric with the fed-point axis. In the hybrid type, the coupling between the patches is through the gap as well as through the connecting strip. Similar configurations can be constructed for patches and parasitic elements of various sizes and shapes.

2.2  Parasitic Antenna Arrays with Steerable Radiation Pattern The energy radiated by an antenna is represented by the radiation diagram of the antenna. Radiation is the term used to represent the emission or reception of an electromagnetic wavefront at the antenna, specifying its strength. From the radiation pattern, one can understand the function and directivity of an antenna. Figure 4a shows a simple patch antenna fed by a microstrip line. A RF switch [18] is

Parasitic Antennas for Current and Future Wireless Communication Systems: Trends…

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a Non-radiating edge gap coupled

Radiating edge gap coupled

b

Direct couple patch

Fig. 3  Parasitic coupling for broad BW (a) Gap coupling (b) Direct coupling

connected in between the active patch and parasitic patch. If the RF switch is OFF and the input power is fed into the antenna, then the radiation occurs from the active patch together with the mutually coupled parasitic patch. When the RF switch is ON, some current flows through the switch into the parasitic patch; these combinations of the radiating surfaces increase the resonance length of the antenna and produce an overall change within the radiation pattern. Using this ON or OFF technique, the radiation pattern of an antenna can be changed in a desired direction as shown in Fig.  4b. Based on this technique, different shapes and combinations of parasitic patch have been reported [26]. Also there is a change in cross-pole. For simplicity, here only co-pole radiation pattern is given. In [27–29], it is reported that when a parasitic structure is present near the patch or at the ground plan of the microstrip patch antenna, there is a change in the radiation pattern of the antenna. When a parasitic antenna is used, the antenna radiates more power in a specific direction and less power in some other directions. This results in a radiating power variation in a direction. Moreover, this steerable

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Fig. 4  A simple example (a) A microstrip-fed patch antenna with RF switch (b) Co-pole radiation pattern

property of the radiation pattern helps in beam-space multi-input multi-output (MIMO) [30].

2.3  Parasitic Element-Based Reconfigurable Antenna Design of reconfigurable antennas is one of the emerging areas of research worldwide due to its multirole properties. Depending on the performance of the antenna, it can be classified as frequency reconfigurable [31], radiation pattern

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reconfigurable [32], polarization reconfigurable [33], and hybrid reconfigurable [34] type. The dynamic tuning can be achieved by manipulating a certain switching mechanism through controlling electric, mechanical, and physical or optical switches [35]. Among them, electric switches are the most popular in constituting reconfigurable antennas due to their efficiency, reliability, and ease of integrating in microwave circuitry. The combination of parasitic elements and RF switches leads to configurability properties of the antenna. In [31, 36], the operating frequency of the antenna has been shifted to some other frequency by using PIN diodes as a microwave switch. This frequency configuration is achieved by altering the electrical length of the antenna. Similarly, changing the radiating structure of the antennas leads to a change in radiation pattern [26]. Polarization reconfiguration allows to change the polarization of an antenna by altering the vertical orientation of the E field and without altering the resonant frequencies and shape of the radiation diagram [33].

3  N  ext-Generation Communication Design and a Passive Radiator To increase the capacity and higher data rates, wireless system designers recently have drawn attention to the reconfigurable intelligent surface (RIS) [37, 38, 39] to create smart wireless communication. In a smart radio environment, surfaces are able to control the propagation of incident electromagnetic waves in a programmable way to actively adjust the channel realization, which turns the wireless channel into a controllable system block that may be optimized to boost the overall system performance [40]. MIMO technology is already a part of the high data rate of wireless communication systems as well as radar systems. One of the most common applications of MIMO technology is to utilize spatial diversity in order to enhance data rate and reliability of a wireless communication system [41]. However, there are many challenges in the implementation of a MIMO system in many scenarios, especially with regard to patch antenna design [42]. First of all, unavailability of sufficient space impedes the design of efficient and decorated MIMO antennas [43]. Second, traditional MIMO requires each antenna to be fed by a unique RF chain. It makes the system costly and bulky [42]. In order to overcome these two limitations, a number of reduced complexity and antenna-decoupling schemes have been proposed. Among them, beam-space MIMO has attracted the attention of many researchers worldwide. Beam-space MIMO is viewed by many researchers as the next-generation implementation technique for massive MIMO. Most of the works related to beam-space MIMO consider switched parasitic array (SPAs) and electronically steerable passive array radiators (ESPARs) [37]. An SPA involves an active radiating element and several physically separated parasitic elements, which can be either connected or disconnected with the active radiating elements using PIN diode switches. To control the switches, the system

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requires an extra power, and failure of any switches disrupts the system performance. An ESPAR, on the other hand, is a smart antenna [44] whose beam pattern can be controlled. ESPAR also contains an active element and switched parasitic elements. However, the parasitic elements are loaded with adjustable reactive elements so that the input impedances of the elements can be controlled. To meet the exponential increase in the demand of the recent wireless data services, massive MIMO with antenna arrays deployed at both base station and user terminals is able to increase the capacity of the channel. To increase the radio frequency transmission or more reliable circuitry, there are a few major limitations in an electromagnetic wave, such as diffraction, scattering effect, and signal being weaker after traveling through obstacles such as buildings in the urban area. As a result, it is not possible to ensure a global coverage of wireless services in 5G and beyond using conventional cellular techniques. So the current progress of the RIS technique provides a revolutionarily new solution to implement the problem by artificially controlling the propagation environment of the radio signal. In general, a RIS is contained in a large number of low-cost and energy-efficient reconfigurable reflecting elements that can reflect the transmitting electromagnetic waves with a smart controller. These intelligent systems provide an extra high-quality channel link to overcome unfavorable propagation conditions of wireless communication systems (Fig. 5). The dissipated electromagnetic wave in the sky and signal loss due to the obstacle in direct line of sight communication can be reduced using the RIS system.

Fig. 5  Next-generation communication system using RIS antenna

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Table 1  Summary of the important work and contribution Description BW improvement with parasitic elements

Important work [21] [23] [24]

Beam steering with parasitic elements

[45] [47] [18]

Reconfigurable antenna with parasitic elements

[44] [35] [33]

Reconfigurable intelligent surface (RIS)

[40] [41] [42] [38, 46]

Contribution A stable radiation pattern over the resonance frequency Dual polarization antenna using RF switch Circularly polarized wideband antenna by using inner and outer parasitic elements Flexible and wearable antenna using partially reflective surface with a parasitic patch array A novel null steering antenna for angle-of-arrival (AoA) estimation Planer application of the RF switches and its modeling Theory of mode analysis of ESPER for a RF MIMO system Different switching techniques used in reconfigurable antennas Reconfigurable antenna and its used in wireless communication Working principle of RIS Next-generation wireless design and use of RIS High-speed data rate and upcoming challenges Practical implementation of RIS

Switch reconfigurable antennas can be used to cope up with the requirement of the environment, including operating from car, confined by ceilings, clothes [45], building facades, etc. Since RIS is used as a passive component, it consumes very less energy as compared to conventional wireless systems [46]. Since RIS only reflects the electromagnetic wave, it can support full-duplex and full-band transmission. The advantage is the absence of analog-to-digital/digital-to-analog converters and power amplifier for which it is low cost and reliable. The contributions of the various recent works in this direction are summarized in Table 1.

4  Conclusion In this chapter, the design considerations for some trending applications of the microstrip parasitic patch have been discussed. The proper design of antenna can fit into the next-generation efficient and high data rate wireless communication systems. Parasitic element-based microstrip antenna design and its radiation principle have been discussed. Also, introducing the new trends of RIS and its importance in the next-generation communication systems have been covered. From the literature, it is observed that the objective is to focus on designs that provide low radiation loss, higher bandwidth, compact, and smaller size and help in energy conservation. The

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chapter has focused on the works dealing with microstrip antennas with parasitic elements used for bandwidth enhancement, beam width and radiation steering, reconfigurable structures, and reconfigurable intelligent surface systems. Further, the coverage has included ESPARs, which have far-reaching consequences and are critical for a range of applications.

References 1. Bird, T.S.: Fundamentals of aperture antennas and arrays: from theory to design, fabrication and testing. Wiley, Chichester (2015) 2. Stutzman, W.L.: Polarization in electromagnetic systems. Artech house, Norwood (2018) 3. Li, Z., Zhengwei, D., Takahashi, M., Saito, K., Ito, K.: Reducing mutual coupling of MIMO antennas with parasitic elements for mobile terminals. IEEE Trans. Antenna Propag. 60(2), 473–481 (2011) 4. Carr, J.J., George, W.: Practical antenna handbook. McGraw-Hill Education, New York (2012) 5. Deschamps, G., Sichak, W.: Microstrip Microwave Antennas. In: Proceedings of the Third Symposium on the USAF Antenna Research and Development Program, October 18–22, 1953. 6. Sze, J.-Y., Wong, K.-L.: Slotted rectangular microstrip antenna for band-width enhancement. IEEE Trans. Antenna Propag. 48(8), 1149–1152 (Aug. 2000). https://doi.org/10.1109/8.884481 7. Katyal, A., Basu, A.: Compact and broadband stacked microstrip patch antenna for target scanning applications. IEEE Antenna Wirel. Propag. Lett. 16, 381–384 (2016) 8. Nakano, H., Yamauchi, J.: Printed slot and wire antennas: a review. Proc. IEEE. 100(7), 2158–2168 (2012) 9. Zhang, S., Syrytsin, I., Pedersen, G.F.: Compact beam-steerable antenna array with two passive parasitic elements for 5G mobile terminals at 28  GHz. IEEE Trans. Antenna Propag. 66(10), 5193–5203 (2018) 10. Lin, K.-C., Lin, C.-H., Lin, Y.-C.: Simple printed multiband antenna with novel parasitic-­ element design for multistandard mobile phone applications. IEEE Trans. Antenna Propag. 61(1), 488–491 (2012) 11. Abbosh, A.M., Bialkowski, M.E.: Design of UWB planar band-notched antenna using parasitic elements. IEEE Trans. Antenna Propag. 57(3), 796–799 (2009) 12. Byun, G., Choo, H.: Antenna polarisation adjustment for microstrip patch antennas using parasitic elements. Electron. Lett. 51(14), 1046–1048 (2015) 13. Nikkhah, M.R., Rashed-Mohassel, J., Kishk, A.A.: Compact low-cost phased array of dielectric resonator antenna using parasitic elements and capacitor loading. IEEE Trans. Antenna Propag. 61(4), 2318–2321 (2013) 14. Ojaroudi, N.: Compact UWB monopole antenna with enhanced bandwidth using rotated L-shaped slots and parasitic structures. Microw. Opt. Technol. Lett. 56(1), 175–178 (2014) 15. Wood, C.: Improved bandwidth of microstrip antennas using parasitic elements. In: IEE Proceedings H (Microwaves, Optics and Antennas). 127. No. 4. IET Digital Library (1980) 16. Huang, J.: Planar microstrip Yagi array antenna. Digest on Antennas and Propagation Society International Symposium, IEEE (1989) 17. Huang, J., Densmore, A.C.: Microstrip Yagi array antenna for mobile satellite vehicle application. IEEE Trans. Antenna Propag. 39(7), 1024–1030 (1991) 18. Kumar, J., Basu, B., Talukdar, F.A.: Modeling of a PIN diode RF switch for reconfigurable antenna application. Scientia Iranica. Trans. D Comput. Sci. Eng. Electr. 26.3, 1714–1723 (2019) 19. Lee, R.Q., Acosta, R., Lee, K.F.: Radiation characteristics of microstrip arrays with parasitic elements. Electron. Lett. 23(16), 835–837 (1987). https://doi.org/10.1049/el:19870591

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Multiband Laptop Antenna with Enhanced Bandwidth for WLAN/WiMAX/GPS Wireless Applications Trushit Upadhyaya, Killol Pandya, Arpan Desai, Upesh Patel, Rajat Pandey, and Merih Palandoken

1  Introduction Wireless communication systems rely on Internet access technology where portable devices incorporating recent technologies are in immense demand as they satisfy the requirements of high-quality wireless links for higher data rates. Apart from adequate performance, wireless devices should be compact and thin to get fitted in laptops, tablets, and notebooks. These devices should also adopt technological advancements to cater to the growing communication needs. The literature depicts that planar monopole antennas are an appropriate candidate for tri-band performance where various resonant frequencies could be attained by structural changes. The planar monopole antenna could be understood as the wire element of an ideal monopole with a planar element. It offers various advantages such as compact in size, wide impedance bandwidth, and omnidirectional radiation pattern. In [1], a compact monopole antenna was proposed for WLAN and WiMAX applications. In design, a toothbrush-shaped patch, U-shaped patch, and a meander line were provided for a tri-band generation. The detailed review of this literature shows targeted resonances could be achieved by changing the dimensions of the structure. The tri-band monopole antenna with good impedance matching was presented in [2]. A compact radiator was introduced in the structure to satisfy the requirement of impedance matching. The planar monopole antennas could fulfill T. Upadhyaya (*) · K. Pandya · A. Desai · U. Patel · R. Pandey Charotar University of Science and Technology, Changa, Gujarat, India e-mail: [email protected]; [email protected]; arpandesai.ec@ charusat.ac.in; [email protected]; [email protected] M. Palandoken Izmir Katip Celebi University, Izmir, Turkey e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 P. K. Malik et al. (eds.), Smart Antennas, EAI/Springer Innovations in Communication and Computing, https://doi.org/10.1007/978-3-030-76636-8_6

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the demand for wireless devices that are embedded in laptops, tablets, and notebooks. A miniaturized novel inverted F antenna for laptop computers was discussed in [3]. In this antenna, two meander shorting strips with a C-shaped radiator are proposed to obtain dual-band operations. Similarly, an ultrathin inverted E-shaped novel antenna was proposed for wireless applications [4]. Two radiating strips are provided for wider impedance bandwidth at targeted frequencies in this design. In [5], an open-slot, dual-wideband, low-profile, L-shaped antenna has been presented for LTE/WWAN application-based tablet devices. Two inverted L-shaped open slots were provided, where a longer inverted L (IL) shape was utilized for the lower frequency band, and shorter IL was utilized for higher frequency band optimization. Compact wideband monopole antenna for LTE/GSM/UMTS applications was presented in [6]. A distributed inductive strip was engineered with the design for size reduction and better impedance matching. There is some evidence of multiband operations by planar antennas in the literature. A uniplanar eight-band antenna with adequate size reduction was discussed in [7]. In this design, a printed coupling circuit was introduced by utilizing a printed loop, which was integrated with a shorted strip to resonate the structure for LTE/ GSM/UMTS band applications. A frequency reconfigurable antenna for LTE/ WWAN applications was proposed in [8]. The geometry includes a loop feeding strip where the radio frequency (RF) switch was engineered for resonance mode variation. Due to such arrangement, the model provided multiband operations with reasonably good gain and radiating efficiency. A dual-strip monopole antenna was presented in [9]. A monopole antenna was resonating for GSM and UMTS band applications. In this structure, an antenna is embedded between hinges and a metal cover. Due to this design, the operating bandwidth could be enhanced with moderate radiation efficiency. The researchers have reported another technique where the branch strip of an antenna was inductively coupled to achieve the desired bandwidth and size miniaturization. Due to this branch strip, an additional resonance was excited near a resonance mode that increases the bandwidth of the lower band [10]. Planar antennas having dual-wideband characteristics were designed [11]. In this design, feeding strip, tuning strip, and parasitic strip were provided to reduce ground effects for the betterment of antenna performance. The size miniaturization is very essential for any antenna development. Such kind of compact antenna model was proposed in [12], where radiating branches and stubs were directly connected with a monopole. With this geometry, the effective size could be reduced to 60%. Few researchers have worked on specific antenna structures where two antennas were combined for 4G/5G applications [13]. The meandered structure and various stubs played a vital role in achieving resonances at desired frequencies. In [14], the half-­ loop antenna structure was discussed for tablet devices. In this structure, the metal casing was utilized to make the model thinner. The literature describes multiple variants of technologies for achieving the multiband planar antennas [15–29]. These antennas incorporate modifications in the electrical length of the conducting resonator by altering the conducting surface path. The alterations primarily involve the introduction of the slots on conducting patches of various structures (Table 1).

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Table 1  Comparison of proposed laptop antenna with other antennas Resonance frequencies (GHz) 0.7, 0.92, 1.7, 1.9, 2.3 [2] 0.83, 1.95, 2.35, 2.66 [3] 0.85, 0.92, 1.79, 1.92, 2.045 [4] 2.4, 2.59, 2.95, 3.7, 4.56, 5.5 [5] 0.46, 0.7, 0.9, 1.5, 1.9, 3.3, 5.5 [6] 0.86, 0.91 [7] 2.4, 5.2 Proposed 1.57, 2.4, 3.5, 5

Ref. [1]

Antenna dimensions (mm3) Gain (dBi) 35 × 10 × 0.8 0.8, 0.9, 1, 1.2, 1.6, 2, 1.8 60 × 200 × 4 −0.9, 0.1, −0.95, −0.98 60 × 200 × 0.8 0.6, 0.5, 1.2, 2.2, 1.8 50 × 200 × 1.6 1.89, 1.61, 0.97, 0.98, 1.72, 1.92 200 × 150 × 1.5 1.8, 3.5, 3.2, 2.83, 3.65, 5.9, 5 128.3 × 50 × 1.6 −12.56, −4.98 260 × 200 × 1.6 4.8, 6.8 50 x 200 x 1.56 6.2, 6.5, 6.2, 8.2

Bandwidth (%) 28, 44 (covering few bands only) 36.47,59.37 22.59, 37.22 14.16, 6.78, 6.21, 3.15, 7.77, 8.18 4.35, 34.2, 90.6, 23.2 – 3.6, 7.5 20.6, 46.44, 20.94, 7.26

Fig. 1  Antenna design configuration (a) Top view (b) Back view

2  Antenna Structure and Parametric Variation The designed antenna is presented in Fig. 1 along with the physical size notations. The antenna is having a size of 50 × 200  m2. The electrical dimensions of the antenna are in the order of 0.86λ × 0.21λ mm2 at the lowest frequency, which is considered large in terms of the typical resonator size, but the objective of the presented design is to incorporate the proposed antenna in the laptop configuration, which has a larger base sheet dimension.

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The antenna was designed by making use of the standard FR4 laminates. These laminates offer the benefits of cost-effectiveness in bulk production. The disadvantage of FR4 laminates is the high losses at frequencies about 1 GHz; however, the tradeoff between cost and losses is needed to be considered while engineering the antenna structure. The surface-mountable antenna has multiple slits that are responsible for the generation of multiple resonance modes. The dimensions of the conducting slits on the top of the substrate are further engineered to improve the impedance bandwidth at each exciting mode. The antenna is excited using offset feed. The feed dimensions are calculated to present 50 Ω impedance to the SMA connector. The engineered feed offers better radiation characteristics of the antenna. The surface current density on the slits of the antenna can be effectively varied by altering the electrical dimension of the feedline at target resonance. The partial ground plane has been employed to improve the bandwidth of the patch resonator; however, the partial ground plane does offer the disadvantage of reducing the antenna F/B ratio. The antenna dimensions are selected after carrying out parametric variation and observing its effect on the reflection coefficient. The four parameters including PL13, PL14, PW13, and GL are varied after which the optimized parameters are decided. Figure 2a indicates that the variation of PL13 leads to a change in the reflection coefficient values along with the impedance bandwidth of the antenna. When the length of PL13 decreases, the bandwidth and reflection coefficient are smaller as

Fig. 2  Performance analysis of antenna in terms of |S11| by varying (a) PL13 (b) PL14 (c) PW13 (d) GL

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Multiband Laptop Antenna with Enhanced Bandwidth for WLAN/WiMAX/GPS… Table 2  Antenna dimensions (in mm) SW SL Pi1 Pi2 Pi3 Pi4 Pi5 Pi6

200 50 13 6 4 5 5 10

Pi7 Pi8 Pi9 Pi10 Pi11 Pi12 Pi13 Pi14

19 26 2 6 3 13 3 17

Pw1 Pw2 Pw3 Pw4 Pw5 Pw6 Pw7 Pw8

92.9 2.1 66 59 11 56 31 39

Pw9 Pw10 Pw11 Pw12 Pw13 Pw14 Pw15 Gi

85 10 11 58 15 26 2 14

compared to the values when the size of the PL13 increases. The optimum value of PL13 is selected as 3 mm. The variation of PL14 and PW13 helps in achieving the acceptable values of reflection coefficient at the second band, while bandwidth at the respective bands is not much affected. The value of PL14 and PW13 is selected as 6 mm. Ground length (GL) variation helps in achieving the required bands of operation. The GL is chosen as 14 mm to accomplishing the proposed application bands. The optimized parameters of the antenna are shown in Table 2. The top and bottom view of an antenna fabricated on the FR4 substrate is illustrated in Fig. 3.

3  Results and Discussion The fabricated antenna is tested in terms of reflection coefficient and radiation patterns using Keysight VNA 9912A and anechoic chamber, respectively. The reflection coefficient plot of the radiator is depicted in Fig. 4, where antenna bandwidth spans from (20.6%) 1.3–1.6 GHz, (46.44%) 2.0–3.21 GHz, (20.94%) 3.42–4.22 GHz, and (7.26%) 4.91–5.28  GHz below the −10  dB level which covers GPS, ISM, WiMAX, and WLAN bands, respectively. The current distribution pattern at 1.49 GHz depicts that current is concentrated near the edges toward the right, middle, and upper left side connected arms as shown in Fig. 5a. At 2.59 GHz, the majority of the current flows in the lower arm of the antenna, while a small amount of current is observed at the other parts of the antenna as illustrated in Fig. 5b. The measured |S11| shows a great correlation with the simulated values. Figure 5c depicts that maximum current distribution at 3.87 GHz is on the feedline and toward the right lower side of the antenna, while at 5 GHz, the current is concentrated at the feedline and right lower side of the radiator, whereas at 5 GHz, the current is concentrated near the feedline and right lower side as illustrated from Figs. 5d and 6. The 2D radiation pattern measured in an anechoic chamber at E and H plane shows that at all frequencies, the antenna shows an omnidirectional pattern which makes the antenna suitable for its use in laptop applications since it can detect the

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Fig. 3  Fabricated prototype of the proposed antenna (a) Top view (b) Back view

Fig. 4  Reflection coefficient of the antenna [simulated (solid) and measured (dashed)]

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Fig. 5  Surface current densities at (a) 1.498 GHz (b) 2.59 GHz (c) 3.87 GHz (d) 5 GHz

signals from all sides. Simulated 2D patterns are in good association with the measured patterns. The setup for radiation pattern measurement is illustrated in Fig. 7. Figure 8 shows the measured gain where an average gain value of more than 5 dBi is observed at bands of concern, which matches well with the simulated gain. The 75% efficiency is achieved for the antenna. The characteristics of the antenna are illustrated in Table 3.

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Fig. 6  2D radiation patterns at (a) 1.498 GHz (b) 2.59 GHz (c) 3.87 GHz (d) 5 GHz [simulated (solid) and measured (dashed)]

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Fig. 7  Radiation pattern measurement setup in anechoic chamber (a) E plane (b) H plane

Fig. 8  Gain and efficiency of the antenna

4  Conclusion A quad-band flat-plate antenna operating at (20.6%) 1.3–1.6  GHz, (46.44%) 2.0–3.21 GHz, (20.94%) 3.42–4.22 GHz, and (7.26%) 4.91–5.28 GHz bands suitable for integrated or internal laptop applications is proposed. The bandwidth of the

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Table 3  Antenna characteristics Impedance bandwidth (%) S M 1.3–1.6 GHz 1.31–1.59 GHz (20.6%) (19.3%) 2.0–3.21 GHz 2.12–3.01 GHz (46.44%) (34.7%) 3.42–4.22 GHz 3.40–4.12 GHz (20.94%) (19.14%) 4.91–5.28 GHz 4.88–5.20 GHz (7.26%) (6.34%)

Center frequency (GHz) 1.498

Peak gain (dBi) S M 6.2 5.5

Efficiency Radiation (abs) pattern S M 0.84 0.81 Omnidirectional

2.59

6.5

7.1 0.83

0.80 Omnidirectional

3.87

6.2

6.3 0.82

0.81 Omnidirectional

5

8.2

8.2 0.78

0.75 Omnidirectional

antenna at the proposed bands is sufficient enough to cover the GPS, ISM, WiMAX, and WLAN bands. The omnidirectional radiation pattern, economical antenna material, gain, and efficiency values more than 5 dBi and 75%, respectively, with ease of integration make the antenna suitable for its use in midsize laptop applications. The simulated and experimental results are presented, where a good correlation is observed. The antenna could be made low profile in order to make it useful for mini tablets and laptops.

References 1. Li, Y., Wenhua, Y.: A miniaturized triple-band monopole antenna for WLAN and WiMAX applications. Int. J. Antenna Propag. 57, 706–709 (2015) 2. Kang, L., Wang, X.-H., Li, H., Shi, X.-W.: Planar monopole antenna with a compact radiator for tri-band applications. Microw. Opt. Technol. Lett. 57(3), 706–709 (2015) 3. Liu, H.-W., Lin, S.-Y., Yang, C.-F.: Compact inverted-F antenna with meander shorting strip for laptop computer WLAN applications. IEEE Antenna Wirel. Propag. Lett. 10, 540–543 (2011) 4. Kulkarni, J.S., Seenivasan, R.: A novel, very low profile dual band inverted ‘E’ monopole antenna for wireless applications in the laptop computer. IEICE Electron. Express. 16, 1–6, (2019) 5. Wong, K.-L., Pei-Rong, W.: Low-profile dual-wideband dual-inverted-L open-slot antennafor the LTE/WWAN tablet device. Microw. Opt. Technol. Lett. 57(8), 1813–1818 (2015) 6. Kim, G.-H., Yun, T.-Y.: Small wideband monopole antenna with a distributed inductive strip for LTE/GSM/UMTS. IEEE Antenna Wirel. Propag. Lett. 14, 1677–1680 (2015) 7. Kulkarni, J., Kulkarni, N., Desai, A.: Development of “H-Shaped” monopole antenna for IEEE 802.11 a and HIPERLAN 2 applications in the laptop computer. Int. J. RF Microw. Comput. Aided Eng. 30(7), e22233 (2020) 8. Ban, Y.-L., Sun, S.-C., Li, P.-P., Li, J.L.-W., Kang, K.: Compact eight-band frequency reconfigurable antenna for LTE/WWAN tablet computer applications. IEEE Trans. Antenna Propag. 62(1), 471–475 (2013) 9. Chen, S.-C., Tsou, Y.-C.: Small-size LTE/WWAN two-strip monopole exciter antenna integration with metal covers. IEEE Trans. Antenna Propag. 64(8), 3707–3711 (2016) 10. Wong, K.-L., Chen, M.-T.: Small-size LTE/WWAN printed loop antenna with an inductively coupled branch strip for bandwidth enhancement in the tablet computer. IEEE Trans. Antenna Propag. 61(12), 6144–6151 (2013)

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11. Sim, C.-Y.-D., Chen, C.-C., Li, C.-Y., Ge, L.: A novel uniplanar antenna with dual wideband characteristics for tablet/laptop applications. Int. J. RF Microw. Comput. Aided Eng. 27(9), e21145 (2017) 12. Subbaraj, S., Kanagasabai, M., Alsath, M.G.N., Ganesan, G., Selvam, Y.P., Kingsly, S.: Compact multiservice monopole antenna for tablet devices. Int. J. Electron. 105(8), 1374–1387 (2018) 13. Subbaraj, S., Kanagasabai, M., Mohammed, G.N.A., Palaniswamy, S.K., Tipparaju, R.R., Kingsly, S., Selvam, Y.P.: Integrated 4G/5G Multiservice MIMO Antenna for Hand-Held Devices. Wirel. Pers. Commun. 111(3), 2023–2043 (2020) 14. Wong, K.-L., Tsai, C.-Y.: Half-loop frame antenna for the LTE metal-casing tablet device. IEEE Trans. Antenna Propag. 65(1), 71–81 (2016) 15. Patel, H., Upadhyaya, T.K.: Printed multiband monopole antenna for smart energy meter/ WLAN/WiMAX Applications. Prog. Electromagn. Res. 89, 43–51 (2020) 16. Patel, H., Upadhyaya, T.: Surface mountable compact printed dipole antenna for GPS/WiMAX applications. Prog. Electromagn. Res. Lett. 96, 7–15 (2021) 17. Pandya, A., Upadhyaya, T.K., Pandya, K.: Tri-band defected ground plane based planar monopole antenna for Wi-Fi/WiMAX/WLAN applications. Prog. Electromagn. Res. 108, 127–136 (2021) 18. Pandya, A., Upadhyaya, T.K., Pandya, K.: Design of metamaterial based multilayer antenna for Navigation/WiFi/satellite applications. Prog. Electromagn. Res. 99, 103–113 (2021) 19. Desai, A., Patel, R., Upadhyaya, T., Kaushal, H., Dhasarathan, V.: Multiband inverted E and U shaped compact antenna for Digital broadcasting, wireless, and sub 6 GHz 5G applications. AEU Int. J. Electron. Commun. 123, 153296 (2020) 20. Subbaraj, S., Malathi, K., Gulam Nabi Alsath, M., Ganesan, G., Selvam, Y.P., Kingsly, S.: Compact multiservice monopole antenna for tablet devices. Int. J. Electron. 105, 1374–1387 (2018). https://doi.org/10.1080/00207217.2018.1440435 21. Bhaskar, S., Singh, A.K.: A dual band dual antenna with read range enhancement for UHF RFID tags. Int. J. RF Microw. Comput. Aided Eng. 29(7), e21717 (2019) 22. Bansal, A., Sharma, S., Khanna, R.: Platform tolerant dual band UHF RFID tag antenna with enhanced read range using artificial magnetic conductor structures. Int. J. RF Microw. Comput. Aided Eng. 30(2), e22065 (2020) 23. Chen, S.C., Huang, C.C., Cai, W.S.: Integration of a low-profile, long-term evolution/wireless wide area network monopole antenna into the metal frame of tablet computers. IEEE Trans. Antenna Propag. 65(7), 3726–3731 (2017) 24. Chou, J.H., Chang, J.F., Lin, D.B., Wu, T.L.: Dual-band WLAN MIMO antenna with a decoupling element for full-metallic bottom cover tablet computer applications. Microw. Opt. Technol. Lett. 60(5), 1245–1251 (2018) 25. Nie, L.Y., Lin, X.Q., Wang, B., Zhang, J.: A planar multifunctional four-port antenna system for sub-urban mobile tablet. IEEE Access. 7, 56986–56993 (2019) 26. Patel, U., Upadhyaya, T.K.: Design and analysis of compact μ-negative material loaded wideband electrically compact antenna for WLAN/WiMAX applications. Prog. Electromagn. Res. 79, 11–22 (2019) 27. Patel, R., Upadhyaya, T.: An electrically small antenna for nearfield biomedical applications. Microw. Opt. Technol. Lett. 60(3), 556–561 (2018) 28. Upadhyaya, T.K., Desai, A., Patel, R.H.: Design of printed monopole antenna for wireless energy meter and smart applications. Prog. Electromagn. Res. 77, 27–33 (2018) 29. Desai, A., Upadhyaya, T., Palandoken, M., Patel, J., Patel, R.: Transparent conductive oxide-­ based multiband CPW fed antenna. Wirel. Pers. Commun. 113(2), 961–975 (2020)

Part II

Performance Analysis of Micro-strip Antenna

Antenna Optimization Using Taguchi’s Method Archana Tiwari and A. A. Khurshid

1  Introduction Wireless communication has been widely used all over the world. Antenna is the key component of wireless communication, and hence it has attracted the interest of researchers from industry and academics toward antenna design [1]. Antenna requirements for wireless communication include features like miniaturization, flexibility, high data rate, etc. [2]. The flexibility feature of antenna can open the possibility of flexible antennas to be integrated into clothing or wearable devices [3]. These antennas should have the ability to adopt any arbitrary shape during various movements of the body, specifically for the wearable devices [4, 5]. Critical parameters of flexible antenna design are as follows [6, 7]: (i) Selection of flexible substrate (ii) Antenna’s performance when the antenna is flexed or bent (iii) Reconfigurability (iv) Fabrication method (v) Specific absorption rate (SAR) (vi) Close proximity with human body This will allow exploiting the area of clothing and other flexible materials to create efficient antennas in critical applications including communication and tracking for defense or safety and monitoring of patients in a hospital or workforce in industries [8, 9].

A. Tiwari (*) · A. A. Khurshid Department of Electronics Engineering, Shri Ramdeobaba College of Engineering and Management, Nagpur, India e-mail: [email protected]; [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 P. K. Malik et al. (eds.), Smart Antennas, EAI/Springer Innovations in Communication and Computing, https://doi.org/10.1007/978-3-030-76636-8_7

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The aim is to achieve the compactness of antenna without affecting the performance of antenna. Microstrip patch antenna with rectangular shape is considered for the performance analysis as a case study. The antenna performance is dependent on the following parameters [10]: (i) Width of patch (ii) Ground plane (iii) Feed point location (iv) Height of substrate (v) Dielectric constant (vi) Loss tangent (vii) Probe diameter (viii) Cover/coating Parametric variations of above parameters can lead to performance improvement in terms of resonance frequency, return loss, gain, bandwidth, etc. The parametric variations need to be done in a systematic way, which can be done by optimization. Optimization can be achieved by various methods like genetic algorithm, Taguchi’s optimization, simulated annealing, artificial neural network, gradient-based techniques, particle swarm optimization, etc. [11]. Taguchi’s optimization technique is explained in the further part of the book chapter, where orthogonal array is used for optimization. Orthogonal array method is more preferred over other two methods, like trial-and-error approach and full factorial experimentation method, because it reduces the number of experiments to be performed and requires less time and resources [12].

2  Microstrip Patch Antenna Microstrip patch antennas are more preferred because of its features like light weight, low profile, ease of fabrication, etc. Microstrip antennas are of various types like circular, triangular, rectangular, etc., out of which rectangular-shaped patch is the simplest one. The basic structure of rectangular patch with inset feed is shown below in Fig. 1. The rectangular patch is designed taking into consideration the frequency of resonance (fr) as 2.45 GHz, which is assigned for ISM (Industrial Scientific Medical) band. The substrate material is selected as FR4, which is an easily available material. The dielectric constant (εr) is 4.4 and height of substrate (h) is 1.59 mm. After considering fr, εr and h, the rectangular patch parameters can be calculated using the following formulas: Width of patch ( w p ) =

c 2 fr

2  r +1

(1)

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Fig. 1  Rectangular microstrip patch antenna with inset feed  Where; a, width of substrate; b, length of substrate; c, height of substrate; a1, width of patch; b1, length of patch; u, width of feedline; v, length of feedline; u1, width of slot between patch and feed; v1, length of slot between patch and feed

where: c – velocity of light Length of patch ( L p ) =

c 2 fr  eff

Effective dielectric constant ( eff ) =

− 2 ∆L

r + 1 + 2

(2) r − 1 2 1 + 12



Extended length ( ∆L ) =

 wp  + 0.264  h  

h wp

(3)

(eff + 0.3)  (eff

 wp  + 0.8  − 0.258 )   h 

∗ 0.412h (4)



Width of substrate ( ws ) = 6h + 6h + w p

(5)



Length of substrate ( Ls ) = 6h + 6h + L p

(6)

The width and length of the patch are calculated as 37.26 mm and 29.72 mm by using formulas 1 and 2, respectively. The width and length of the substrate is calculated as 56.34 mm and 48.80 mm using formulas 5 and 6, respectively. Hence, the size of the antenna is found out to be 56.34 × 48.80 × 1.59 mm3. But for wearable device application, the compact size of the antenna is desirable. Hence, miniaturization is achieved by using Taguchi’s optimization method.

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3  Taguchi’s Optimization Method Optimization techniques are basically classified into two types, i.e., local optimization technique and global optimization technique. Gradient-based techniques come under local optimization technique, whereas global optimization technique is used in particle swarm optimization, genetic algorithm, Taguchi’s method, simulated annealing, and artificial neural network. For achieving optimization there are various methods like trial-and-error approach, full Factorial experimentation and orthogonal array method. Orthogonal array method basically reduces the trial experiments by the systematic selection of input parameters, whereas in other two methods, the number of experiments to be performed is more, which requires more time and resources. Hence, orthogonal arrays are more preferred over other methods. Taguchi’s method is selected for optimization. The process flow of Taguchi’s method is explained in Flow Chart 1. The first step of the process flow of Taguchi’s method is to design an orthogonal array (OA) to select a fitness function. Orthogonal array consists of: N – rows or number of experiments k – columns or number of input parameters s – levels of parameters t – strength (0 ≤ t ≤ k) Hence, orthogonal array is in the form OA (N, k, s, t). In the orthogonal array, the number of experiments to be performed is decided by Rao’s inequality equations, and the parameters of OA must satisfy the equations of existence and construction as shown in Eqs. 7 and 8 [13].



u k i N ≥ ∑   ( s − 1) , if t = 2u, u > 0 i =0  i  (7)



u  k − 1 k i u +1 N ≥ ∑   ( s − 1) +   ( s − 1) , if t = 2u + 1, u ≥ 0 i =0  i   u  (8)

4  I mplementations of Taguchi’s Method for Rectangular Patch Antenna The antenna size is targeted to be reduced without affecting the performance of the antenna, like frequency of resonance, return loss, and gain. This is achieved using parametric variations by systematic section method, i.e., using OA of Taguchi’s optimization method. The parameters which are considered for variation are width of patch, ground plane, and position of feed for FR4 as substrate material. The ground-plane variation is further divided into two parameters, such as width and length of ground plane. As in the design, full ground plane is used; hence, the size

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Flow Chart 1  Process flow of Taguchi’s method

of the ground plane is the size of the substrate. Also the position of feed is further divided into two parameters, such as width of slot and width of feed. The OA for the rectangular patch antenna is considered for the following parameters of antenna: P1 – width of patch P2 – width of ground plane P3 – length of ground plane P4 – width of slot P5 – width of feed The above five parameters of antenna are considered for five different levels, which is given in Table 1. The OA (25, 5, 5, 2) designed is shown in Table 2. For the designed OA (25, 5, 5, 2) shown in Table 2, a total of 25 design experiments are simulated in the first iteration. The first iteration results found in terms of resultant frequency and return loss, after simulations, are presented in Table 3. The parametric variations observed from Table 3 simulation experimentation are as follows.

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Table 1  Parameters of antenna with five different levels

Factor levels 1 2 3 4 5

Ground plane Width of substrate P2 23.4 35.1 46.8 58.5 70.2

Width of patch P1 18.63 27.94 37.26 46.57 55.89

Length of substrate P3 39.26 44.17 49.07 53.83 58.89

Feed point location Width of Width of slot feed P4 P5 0.25 1.515 0.37 2.27 0.5 3.03 0.62 3.79 0.75 4.545

Table 2  OA (25, 5, 5, 2) Experiment E1 E2 E3 E4 E5 E6 E7 E8 E9 E10 E11 E12 E13 E14 E15 E16 E17 E18 E19 E20 E21 E22 E23 E24 E25

Elements P1 1 1 1 1 1 2 2 2 2 2 3 3 3 3 3 4 4 4 4 4 5 5 5 5 5

P2 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5

P3 1 2 3 4 5 2 3 4 5 1 3 4 5 1 2 4 5 1 2 3 5 1 2 3 4

P4 1 2 3 4 5 3 4 5 1 2 5 1 2 3 4 2 3 4 5 1 4 5 1 2 3

P5 1 2 3 4 5 4 5 1 2 3 2 3 4 5 1 5 1 2 3 4 3 4 5 1 2

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Table 3  First iteration results of OA after simulation Width of patch (a1) Experiments P1 E1 18.63 E2 18.63 E3 18.63 E4 18.63 E5 18.63 E6 27.94 E7 27.94 E8 27.94 E9 27.94 E10 27.94 E11 37.26 E12 37.26 E13 37.26 E14 37.26 E15 37.26 E16 46.57 E17 46.57 E18 46.57 E19 46.57 E20 46.57 E21 55.89 E22 55.89 E23 55.89 E24 55.89 E25 55.89

Width of substrate (a) P2 23.4 35.1 46.8 58.5 70.2 23.4 35.1 46.8 58.5 70.2 23.4 35.1 46.8 58.5 70.2 23.4 35.1 46.8 58.5 70.2 23.4 35.1 46.8 58.5 70.2

Length of substrate (b) P3 39.26 44.17 49.07 53.83 58.89 44.17 49.07 53.83 58.89 39.26 49.07 53.83 58.89 39.26 44.17 53.83 58.89 39.26 44.17 49.07 58.89 39.26 44.17 49.07 53.83

Width of slot (u1) P4 0.25 0.37 0.5 0.62 0.75 0.5 0.62 0.75 0.25 0.37 0.75 0.25 0.37 0.5 0.62 0.37 0.5 0.62 0.75 0.25 0.62 0.75 0.25 0.37 0.5

Width of feed (u) P5 1.515 2.27 3.03 3.79 4.545 3.79 4.545 1.515 2.27 3.03 2.27 3.03 3.79 4.545 1.515 4.545 1.515 2.27 3.03 3.79 3.03 3.79 4.545 1.515 2.27

Resultant frequency 2.44 2.48 2.48 2.54 2.58 2.42 2.44 2.38 2.4 2.42 2.4 2.38 2.36 2.36 2.3 2.3 2.32 2.26 2.56 2.34 2.66 2.48 2.32 2.58 2.58

Return loss −24.93 −20.02 −11.8 −10.96 −12.7 −23.69 −28.71 −8.91 −29.32 −23.81 −10.76 −14.39 −16.44 −23.7 −7.64 −29.79 −10.89 −8.08 −22.19 −14.96 −22.45 −18.94 −19.98 −10.89 −18.99

Fitness function 0.01 −0.03 −0.03 −0.09 −0.13 0.03 0.01 0.07 0.05 0.03 0.05 0.07 0.09 0.09 0.15 0.15 0.13 0.19 −0.11 0.11 −0.21 −0.03 0.13 −0.13 −0.13

S/N ratio 40 30.46 30.46 20.91 17.72 30.46 40 23.10 26.02 30.46 26.02 23.10 20.91 20.91 16.48 16.48 17.72 14.42 19.17 19.17 13.55 30.46 17.72 17.72 17.72

4.1  Effect of Width of Patch The width of the patch has significant effect on the performance of antenna such as input impedance, resonance frequency BW, and gain of the antenna. For the five different values of width of patch, performance variation is observed in terms of resonance frequency of antenna, and it is found that if the width of the patch is decreased from 44.71 mm to 22.35 mm, the resonance frequency of the antenna is increased from 2.43 GHz to 2.53 GHz. So as the width of the patch increases, resonance frequency decreases; hence, it will increase the gain and bandwidth of the antenna.

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4.2  Width of Slot Feed point location of patch is another important parameter, and in the discussed optimization method, it is governed by the parameter width of slot. For the five different widths of slot from 0.25 mm to 0.75 mm variations, the resonance frequency is observed to be varied from 2.43 GHz to 2.53 GHz.

4.3  Width of Feed Width of feed is also considered as one of the parameters for optimization, and it is observed that if the width of feed is increased from 5.98 mm to 8.97 mm, the resonance frequency is decreased from 2.53 GHz to 2.43 GHz. In the first iteration, it is observed that experiments 1, 2, 3, 6, 7, 10, and 22 have given minimum fitness function and high signal-to-noise ratio, which is shown in Table  4. Optimization results are considered based on resonance frequency and return loss parameter. It is evident from the identified experiments that the first design experiment from the first iteration gives optimized results in terms of return loss parameter and directivity. The optimum design selected with parameters is shown in Table 5. After simulation of experiment 1, the size of the antenna is optimized as 39.26 × 23.4 ×1.59 mm3 at a resonance frequency of 2.44 GHz with a return loss of −24.93 dB and operational bandwidth of 4.09%. The optimized antenna fabricated on FR4 substrate with dielectric constant 4.4 has a loss tangent of 0.02. The optimized antenna’s front and back sides after simulation and fabrication are shown in Fig. 2. The measurement of the optimized antenna is performed with the use of VNA from Keysight technologies with a 50 Ω SMA connector to the microstrip feedline. Figures 3 and 4 show the return loss plot vs frequency and Smith chart plot of simulated and fabricated antenna, respectively. Comparative analysis of simulated and measured results of the antenna is shown in Table 6.

5  F  lexible Antenna and Implementation of Taguchi’s Method for Rectangular Patch Antenna To cope up with the design requirements of flexible antenna, flexible substrate is required. Some identified alternative flexible substrate materials with their comparative studies are shown in Table 7. Textile polyester material is considered as flexible antenna substrate with dielectric constant of 2.75 and thickness of 1.5 mm, for further designing procedure. The

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Table 4  Results with minimum fitness function and maximum S/N ratio Antenna parameters (a) Width of substrate (mm) (b) Length of substrate (mm) (a1) Width of patch (mm) (u1) Width of slot of feed (u) Width of feedline (mm) εr Feed type

Exp 1 23.4 39.26

18.63 0.25 1.515 4.4 Inset feed Height of substrate (mm) 1.59 Length of patch (mm) 29.72 Length of feedline (mm) 16.62 ∆L (mm) 0.29 εr (effective) (mm) 4.082 Effective length (mm) 30.3 Electrical length (mm) 87.38 Results achieved after simulation Resultant frequency (GHz) 2.44 Return loss −24.93

Exp 2 35.1 44.17

Exp 3 46.8 49.07

Exp 6 23.4 44.17

Exp 7 35.1 49.07

Exp 10 Exp 22 70.2 35.1 39.26 39.26

18.63 0.37 2.27 4.4 Inset feed 1.59 29.72 16.62 0.29 4.082 30.3 87.38

18.63 0.5 3.03 4.4 Inset feed 1.59 29.72 16.62 0.29 4.082 30.3 87.38

27.94 0.5 3.79 4.4 Inset feed 1.59 29.72 16.62 0.29 4.082 30.3 87.38

27.94 0.62 4.545 4.4 Inset feed 1.59 29.72 16.62 0.29 4.082 30.3 87.38

27.94 0.37 3.03 4.4 Inset feed 1.59 29.72 16.62 0.29 4.082 30.3 87.38

2.48 2.48 −20.02 −11.8

2.42 2.44 2.42 2.48 −23.69 −28.71 −23.81 −18.94

Table 5  Results with minimum fitness function and maximum S/N ratio Antenna parameters (a) Width of substrate (mm) (b) Length of substrate (mm) (a1) Width of patch (mm) (u1) Width of slot of feed (u) Width of feedline (mm) Dielectric constant εr (for FR4 material) Feed type Height of substrate (mm) Length of patch (mm) Length of feedline (mm) ∆L (mm) Effective dielectric constant εr (effective) (mm) Effective length (mm) Electrical length (mm) Results after simulation Resultant frequency (GHz) Return loss Operational bandwidth

Experiment 23.4 39.26 18.63 0.25 1.515 4.4 Inset feed 1.59 29.72 16.62 0.29 4.082 30.3 87.38 2.44 −24.93 4.09%

55.89 0.75 3.79 4.4 Inset feed 1.59 29.72 16.62 0.29 4.082 30.3 87.38

78

Fig. 2  Simulated and fabricated antenna, front and back side

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Fig. 3  Return loss vs frequency plot of simulated and fabricated antenna

Fig. 4  Smith chart of simulated and fabricated antenna

parameters of antenna are calculated, and for compactness, Taguchi’s method is implemented on flexible textile polyester substrate-based rectangular patch antenna. As discussed earlier, Taguchi’s optimization procedure includes orthogonal array design with consideration of different antenna parameters. Five parameters of antenna are considered for five different levels as shown in Table 8. The orthogonal array is considered for N, rows or number of experiments; k, columns or number of input parameters; s, levels of parameters; and t, strength (0 ≤ t ≤ k) with the values N = 25, k = 5, s = 5, and t = 2. Hence, for the designed OA (25, 5, 5, 2), 25 design experiments are simulated in the first iteration. The first iteration results found after simulations are presented in Table 9. In the first iteration, experiments 1, 2, 3, 6, 10, 14, and 15 have given minimum fitness function and high signal-to-noise ratio, which is shown in Table  10. Optimization results can be considered based on resonance frequency and return loss parameter. From the identified experiments, best result is then considered based on minimum fitness function and maximum S/N ratio, and better return loss.

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Table 6  Comparative analysis of simulated and measured results of the antenna Proposed antenna Simulated results Measured results

Resonance frequency (GHz) 2.44

Bandwidth (%) 4.06

Real part of impedance Return loss measured on Smith chart (ohms) (dB) −24.93 47.26

2.43

2.46

−30.35

49.9

Table 7  Comparative study of flexible substrate materials Paper reference Year of publication Substrate material Antenna type

[14] 2019

[15] 2019

[16] 2018

[17] 2019

[18] 2019

Fabric

PDMS

Paper

Polyimide

PET

Textile

PDMS

Paper

Antenna shape

Inset feed rectangular patch Size (mm) 54 × 37 Thickness (mm) 1.5 Dielectric 2.75 constant Dielectric loss Not mentioned (tan δ) 2.45 Frequency (GHz) Band Single

Unit cell 8×8 2 2.63

Kapton polyimide Square MIMO complex shape 50x50 22 × 31 0.18 0.125 2.8 3.4

Polyester (PETP) film-based Rectangular 50 × 33 0.1 3.8

0.076

0.15

Not mentioned

0.0021

11.4

2.45

2.9–12 GHz

Single

Single Variable

2.21–2.69 and 3.14–3.55 Variable

Table 8  Parameters of flexible antenna with five different levels

Factor levels 1 2 3 4 5

Width of patch P1 (a1) 44.71 39.12 33.53 27.94 22.35

Ground-plane width of substrate P2 (a) 62.71 57.12 51.53 45.94 40.35

Length of substrate P3 (b) 53.89 49.39 44.89 40.39 36

Width of slot P4 (u1) 0.25 0.37 0.5 0.62 0.75

Length of slot P5 (v1) 8.97 8.22 7.47 6.72 5.98

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Table 9  Simulation results of flexible antenna after the first iteration of OA Width of patch (a1) Experiment P1 E1 44.71 E2 44.71 E3 44.71 E4 44.71 E5 44.71 E6 39.12 E7 39.12 E8 39.12 E9 39.12 E10 39.12 E11 33.53 E12 33.53 E13 33.53 E14 33.53 E15 33.53 E16 27.94 E17 27.94 E18 27.94 E19 27.94 E20 27.94 E21 22.35 E22 22.35 E23 22.35 E24 22.35 E25 22.35

Width of substrate (a) P2 62.71 57.12 51.53 45.94 45 62.71 57.12 51.53 45.94 40.35 62.71 57.12 51.53 45.94 40.35 62.71 57.12 51.53 45.94 40.35 62.71 57.12 51.53 45.94 40.35

Length of substrate (b) P3 53.89 49.39 44.89 40.39 36 49.39 44.89 40.39 36 53.89 44.89 40.39 36 53.89 49.39 40.39 36 53.89 49.39 44.89 36 53.89 49.39 44.89 40.39

Width of slot (u1) P4 0.25 0.37 0.5 0.62 0.75 0.5 0.62 0.75 0.25 0.37 0.75 0.25 0.37 0.5 0.62 0.37 0.5 0.62 0.75 0.25 0.62 0.75 0.25 0.37 0.5

Length of slot (v1) P5 8.97 8.22 7.47 6.72 5.98 6.72 5.98 8.97 8.22 7.47 8.22 7.47 6.72 5.98 8.97 5.98 8.97 8.22 7.47 6.72 7.47 6.72 5.98 8.97 8.22

Resultant frequency 2.43 2.43 2.43 3.98 5.06 2.45 2.45 2.46 2.54 2.44 2.48 2.48 2.57 2.46 2.46 4.91 4.83 2.5 2.5 4.86 2.63 2.53 2.54 2.54 2.55

Return loss −22.46 −19.72 −14.01 −28.34 −24.23 −10.59 −7 −7.41 −3.49 −32.66 −7.53 −4.03 −2.8 −11.77 −17.39 −34.12 −20.66 −9.39 −7.5 −15.08 −1.86 −5.15 −3.55 −3.81 −2.23

Fitness function 0.02 0.02 0.02 −1.53 −2.61 −0.01 −0.01 −0.01 −0.09 0.01 −0.03 −0.03 −0.12 −0.01 −0.01 −2.46 −2.38 −0.05 −0.05 −2.41 −0.18 −0.08 −0.09 −0.09 −0.1

S/N ratio 33.98 33.98 33.98 −3.694 −8.333 45.04 45.04 40 20.92 40 30.46 30.46 18.42 40 40 −7.819 −7.532 26.02 26.02 −7.64 14.89 21.94 20.92 20.92 20

Table 10  Identified experiments after optimization with minimum fitness function and maximum S/N ratio Antenna parameters (a) Width of substrate (mm) (b) Length of substrate (mm) (a1) Width of patch (mm) (u1) Width of slot of feed (u) Width of feedline (mm) εr

Exp 1 62.71

Exp 2 57.12

Exp 3 51.53

Exp 6 62.71

Exp 10 Exp 14 Exp 15 40.35 45.94 40.35

53.89

49.39

44.89

49.39

53.89

53.89

49.39

44.71 0.25 8.97 2.75

44.71 0.37 8.22 2.75

44.71 0.5 7.47 2.75

39.12 0.5 6.72 2.75

39.12 0.37 7.47 2.75

33.53 0.5 5.98 2.75

33.53 0.62 8.97 2.75

(continued)

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Table 10 (continued) Antenna parameters Feed type

Exp 1 Inset feed Height of substrate (mm) 1.5 Length of patch (mm) 35.89 Length of feedline (mm) 17.97 ∆L (mm) 0.92 εr (effective) (mm) 2.63 Effective length (mm) 37.74 Electrical length (mm) 105.51 Results achieved after simulation Resultant frequency 2.43 (GHz) Return loss (dB) −22.46 Gain (dBi) 6.75

Exp 2 Inset feed 1.5 35.89 14.97 0.92 2.63 37.74 105.51

Exp 3 Inset feed 1.5 35.89 11.97 0.92 2.63 37.74 105.51

Exp 6 Inset feed 1.5 35.89 13.47 0.92 2.63 37.74 105.51

Exp 10 Inset feed 1.5 35.89 16.47 0.92 2.63 37.74 105.51

Exp 14 Inset feed 1.5 35.89 14.98 0.92 2.63 37.74 105.51

Exp 15 Inset feed 1.5 35.89 15.72 0.92 2.63 37.74 105.51

2.43

2.43

2.45

2.44

2.46

2.46

−19.72 −14.01 −10.59 −32.66 −11.77 −17.39 6.56 6.35 6.48 6 6 6

It is evident from the identified experiments that the 15th design experiment from the first iteration has given optimized results in terms of return loss parameter, resonance frequency, and compactness. After simulation of experiment 15, the return loss found is −17.39 dB at a resonance frequency of 2.46 GHz for a compact size of 49.39 x 40.35 mm2, which is comparatively small than the size obtained by considering formulae which is 62.71 x 53.89 mm2. The return loss vs frequency plot is shown in Fig. 5. Gain plot is shown in Fig. 6, which shows a maximum gain of 6 dBi. It is observed that after application of Taguchi’s optimization, the first iteration results indicate a percentage reduction of around 58.97% in size. In order to comply with the requirements of various wearable devices or other biomedical applications, the design can be simulated for further set of iterations to achieve compactness. The results presented are exemplary, and the designers can apply the same as per their requirements.

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Fig. 5  Return loss vs frequency plot of optimized design of flexible antenna

Fig. 6  3D and 2D gain plot of optimized design of flexible antenna

References 1. Abbasi, Q.H., Rehman, M.U., Yang, X., Alomainy, A., Qaraqe, K., Serpedin, E.: Ultrawideband band-notched flexible antenna for wearable applications. Antenna Wirel. Propag. Lett. 12, 1606–1609 (2013). https://doi.org/10.1109/LAWP.2013.2294214 2. Ahmed, S., Tahir, F.A., Shamim, A., Cheema, H.M.: A compact Kapton-based inkjet-printed multiband antenna for flexible wireless devices. Antenna Wirel. Propag. Lett. 14, 1802–1805 (2015). https://doi.org/10.1109/LAWP.2015.2424681 3. Hu, J.: Overview of Flexible Electronics from ITRI’s Viewpoint, p. 1 4. Velasco-Castillo, E.: The smart wearables market will be worth USD22.9 billion worldwide by 2020, p. 3 (2014) 5. Kiourti, A., Volakis, J.L.: Stretchable and Flexible E-Fiber Wire Antennas Embedded in Polymer. Antenna Wirel. Propag. Lett. 13, 1381–1384 (2014). https://doi.org/10.1109/ LAWP.2014.2339636

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6. Hu, B., Gao, G.-P., He, L.-L., Cong, X.-D., Zhao, J.-N.: Bending and On-Arm Effects on a Wearable Antenna for 2.45  GHz Body Area Network. Antenna Wirel. Propag. Lett. 15, 378–381 (2016). https://doi.org/10.1109/LAWP.2015.2446512 7. Salonen, P., Rahmat-Samii, Y., Kivikoski, M.: Wearable antennas in the vicinity of human body. In: IEEE Antennas and Propagation Society Symposium, 2004., Monterey, CA, USA, 2004, pp. 467–470 Vol.1, https://doi.org/10.1109/APS.2004.1329675 8. Embong, E.N.F.S.E., Rani, K.N.A., Rahim, H.A.: The wearable textile-based microstrip patch antenna preliminary design and development. In: 2017 IEEE 3rd International Conference on Engineering Technologies and Social Sciences (ICETSS), Bangkok, Aug. 2017, pp. 1–5, https://doi.org/10.1109/ICETSS.2017.8324149 9. Vallozzi, L., Vandendriessche, W., Rogier, H., Hertleer, C., Scarpello, M.L.: Wearable textile GPS antenna for integration in protective garments, p. 4 10. Kumar, G., Ray, K.P.: Broadband microstrip antennas. Artech House, Boston (2003) 11. Weng, W.-C., Choi, C.: Optimal design of CPW Slot Antennas Using Taguchi’s Method. IEEE Trans. Magn. 45(3), 1542–1545 (2009). https://doi.org/10.1109/TMAG.2009.2012737 12. Jia, X., Lu, G.: A Hybrid Taguchi binary particle swarm optimization for antenna designs. Antenna Wirel. Propag. Lett. 18(8), 1581–1585 (2019). https://doi.org/10.1109/ LAWP.2019.2924247 13. Weng, W.-C., Yang, F., Elsherbeni, A.: Electromagnetics and Antenna Optimization Using Taguchi’s Method. Morgan & Claypool (2008) 14. Vital, D., Bhardwaj, S., Volakis, J.L.: Textile based large area RF-power harvesting system for wearable applications. IEEE Trans. Antenna Propag. 68, 2323–2331 (2019). https://doi. org/10.1109/TAP.2019.2948521 15. Hossain, T.M., Mirza, H., Soh, P.J., Jamlos, M.F., Sheikh, R.A., Al-Hadi, A.A., Akkaraekthalin, P.: Broadband single-layered, single-sided flexible linear-to-circular polarizer using square loop array for S-band pico-satellites. IEEE Access. 7, 149262–149272 (2019). https://doi. org/10.1109/ACCESS.2019.2944901 16. Tran Thi Lan and Hiroyuki Arai, “Propagation loss reduction between on-body antennas by using a conductive strip line”, IEEE Antenna Wirel. Propag. Lett., 17 12: 2449-2453 December 2018. 17. Li, W., Hei, Y., Grubb, P.M., Shi, X., Chen, R.T.: Compact inkjet-printed flexible MIMO antenna for UWB applications. IEEE Access (2018). https://doi.org/10.1109/ACCESS.2018.2868707 18. Saraswat, K., Harish, A.R.: Flexible dual-band dual-polarised CPW-fed monopole antenna with discrete-frequency reconfigurability. IET Microw. Antenna Propag. 13(12), 2053–2060, ISSN 1751-8725 (2019). https://doi.org/10.1049/iet-­map.2018.5711

A Novel Compact Frequency and Polarization Reconfigurable Slot Antenna Using PIN Diodes for Cognitive Radio Applications V. N. Lakshmana Kumar, M. Satyanarayana, Sohanpal Singh, and Dac-Nhuong Le

1  Introduction Present days, wireless communications systems need advanced ways to bring speed data communication and superior use of frequency spectrum in consonance to user requirement. An auspicious surrogate that achieves these symptoms is cognitive radio systems. As per the guidelines of FCC, CR means real-time scanning of a channel or frequency spectrum and inhibits communications in terms of power and frequency in order to avert unhealthy interference to other frequency users [1, 2]. The authors in the paper [2] comment that, for a cognitive radio (CR) equipment to function properly, it must fundamentally follow a series of steps: (1) sensing channel operation, (2) selecting which frequency part is applicable for transmission, (3) communication starts through that channel, and (4) culture from earlier channel activity. In CR, empty frequency slots of the spectrum are identified and allocated to other users dynamically [3]. The most important subsystem of CR is the antenna. It should be reconfigurable in performance parameters like polarization, pattern, and frequency, depending on V. N. Lakshmana Kumar (*) · M. Satyanarayana Department of Electronics and Communication Engineering, M.V.G.R College of Engineering(A), Vizianagaram, Andhra Pradesh, India e-mail: [email protected] S. Singh Department of Electronics and Communication Engineering, Mahatma Gandhi Institute of Technology, Hyderabad, Telangana, India e-mail: [email protected] D.-N. Le Haiphong University, Haiphong, Vietnam e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 P. K. Malik et al. (eds.), Smart Antennas, EAI/Springer Innovations in Communication and Computing, https://doi.org/10.1007/978-3-030-76636-8_8

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the system’s needs [4]. In the paper [5], the authors have mentioned the capabilities that are required for an antenna in order to play a vital role in CR systems. An antenna design for spectrum sensing and communication is highly difficult. Many researchers have been trying to cross the requirements for the design of such type of antennas for CR systems. The reconfiguration is accomplished through the reconstruction of the currents, so that the EM fields of the effective interstitial antenna cause reversible variations in the radiation properties or impedance of the antenna [6].These variations are facilitated via different mechanisms. These are material adjustment, structural changes, and switching. Different antennas are not required for covering different frequency bands with this reconfigurability. There are disparate alternative methods to achieve reconfigurable antenna. For example, the authors have proposed a microstrip antenna with circular intersection truncation to obtain polarization reconfigurability [7]. In [8], reconfigurability was achieved with tunable inductor. The concept of placing switchable PIN diodes is explained to achieve dual-band absorber in [9]. The combination of varactor diodes and PIN diodes for printed monopole antennas resulted in a reconfigurable ultra-wideband MIMO antenna in [10].The concept of DC-controlled varactor-based matching network is proposed to design reconfigurable ultra-wideband antenna for cognitive radio applications [11].  To achieve circular polarization, the idea of orthogonally placing stub and strip in the ground plane of the microstrip patch antenna is presented in [12]. In this study, we have mentioned an investigation and composition of a compact polarization and frequency reconfigurable slot antenna. This is reconfigured with HPND4005 PIN diodes for CR applications.

2  Design The proposed design is a compact polarization and frequency reconfigurable single-­ slot microstrip antenna. The feedline of this antenna is λ/4. The current through the antenna surface is linear when all the diodes are OFF, which increase the antenna gain and efficiency. Figure 1 shows the structure of this antenna. The impedance of the feedline is 50 ohms, and the resonant frequency is 5.2 GHz. FR4 substrate material is used for the design of the proposed antenna with εr = 4.4 .The simulations are carried out using high-frequency structure simulator (HFSS). The dimensions of the proposed design are calculated using the equations in [6]. The polarization reconfiguration was achieved by placing four L-shaped microstrip lines in the four corners of the patch antenna. The four L-shaped strip lines are of different widths and lengths. The dimensions of L-shaped strip lines are chosen by optimetrics in HFSS tool to achieve polarization reconfigurability. By changing the effective electrical length, the L-shaped strip lines provide polarization

A Novel Compact Frequency and Polarization Reconfigurable Slot Antenna Using PIN…

Fig. 1 (a) Antenna design top view (b) Antenna design ground view

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reconfigurability. These are interconnected with the patch by ON/OFF of the PIN diode switches. When switches S1, S2, S3, and S4 are OFF, the proposed antenna radiates with linear polarization. For circular polarization, switches S1, S2, S3, and S4 are ON. The frequency reconfiguration was achieved by changing the state of switch S5.

2.1  Design Equations The proposed antenna design specifications are as follows. The substrate material is FR4 epoxy with a dielectric constant of 4.4 and height of substrate (h) = 1.6 mm. The operating frequency of the recommended antenna f0 is 5.2  GHz. The design steps for the proposed antenna are as follows: The width (W) of the patch is calculated using Eq. (1): c

W 2 f0



(1)

 r  1 2



where c = 3 × 108 m/s and εr = 4.4. The effective length of patch antenna depends on the resonance frequency (f0) and is given by Eq. (2): Leff 

c

(2)

2 f0  reff





Where  reff

1

  1  r  1  12h  2  r  1 2 2  w 

(3)

The E fields at the edges of the patch undergo fringing effects. Because of these effects, the effective length of the patch antenna appears to be greater than its actual length. So, the actual and effective length of a patch antenna can be related as:

L  Leff  2L

(4)

where L is the actual length, ΔL is a function of an effective dielectric constant εreff, and w/h is the width-to-height ratio.



w   0.264   reff  0.3  h L   0.412 w h   0 258 .  reff    0.8  h   

(5)

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The calculated values of W and L are 17.5  mm and 12.56  mm, respectively, which are named as Wp and LP in the following table. The quarter-wave impedance transformer rule is used for calculating the feedline dimensions. The diagonal slot length is chosen as 12 mm, which is the optimized value selected between λg/3 and λg/2. λg, which is the guided wave length.

2.2  D  imensional Parameters for the Designed Antenna (Table 1) Table 1  Dimensions of the proposed antenna in mm Ls 58.94 W1 8 W4 6 Sw3 2.12*2.25

Ws 35.9 W11 2.1 W41 1

Lg 58.9 L2 6 V1 12

Wg 35.9 W2 7.5 Wp 17.5

Lf 14 W21 2 Lp 12.56

Wf 3.05 L3 5.5 Sw4 1.62*1.19

Lf1 8.29 W3 7 Sw5 1*0.75

Wf1 0.9 W31 1.5 Sw1 3.17*2.19

L1 6 L4 5 Sw2 2.62*2.25

3  Results and Discussion The S11 plot of the recommended antenna is shown in Fig. 2. This antenna operates in different bands, achieved by changing the state of the PIN diode. When switches S1, S2, S3, S4, and S5 are OFF, the minimum return loss of 13.2 dB is observed at

Fig. 2 S11 plot for four switching states (0, OFF; 1, ON)

0 –5

S11(dB)

–10 –15 –20 –25

00000 00001 11110 11111

7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 FREQUENCY(GHz)

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Fig. 3  VSWR plot for four switching states (0, OFF; 1, ON)

5

VSWR

4 3 2 00000 00001 11110 11111

1 0

7

8

9 10 FREQUENCY(GHz)

11

12

a frequency of 10.75 GHz. When switches S1, S2, S3, and S4 are OFF and S5 is ON, the antenna resonates at 10.5 GHz with a return loss of 19.36 dB .When the state of switches S1, S2, S3, S4, and S5 changes to ON condition, the antenna resonates at 10.9 GHz with a return loss of 27.42 dB. When S1, S2, S3, and S4 are ON and S5 is OFF, the antenna resonates at 11.41  GHz with a return loss of 18.97 dB. Thus, the proposed antenna achieved frequency reconfiguration. Figure 3 shows the VSWR plot for the four switching states. For all the states, VSWR value less than 2 is achieved at different frequencies. The radiation pattern for different switch conditions is shown in Fig. 4. They are plotted for phi (Φ = 00) and for different values of “θ.” For S1, S2, S3, S4, and S5 ON-state combination, maximum radiation is observed for θ = −200 direction. The 3D polar plots of the recommended antenna for the two switching states are shown in Fig. 5. A maximum gain of 3 dBi is achieved when S1, S2, S3, and S4 are ON and S5 is in OFF condition, and maximum gain of 5 dBi is achieved when the five switches are in the ON-state condition. The proposed design switches from linear (LP) to circular polarization (CP), when the switching states of S1–S4 are changed from OFF condition to ON condition. Figure  6 shows the axial ratio plot for the two mentioned states. The axial ratios less than 3 dB are obtained at 9.75 GHz, 11.7 GHz, and 13.75 GHz, respectively, for switches 11111 combination. The surface current distribution of the suggested antenna is shown in Fig. 7. For the switch state where S1, S2, S3, and S4 are OFF and S5 is ON, the maximum current density of 1.57 × 102A/m is achieved, and for the another state where S1–S5 are ON, the maximum current density is 2.47 × 102 A/m.

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Fig. 4  Radiation pattern for (a) S1,S2,S3,S4, and S5 ON (b) S1,S2,S3,S4, ON; S5, OFF (c) For S1,S2,S3,S4, and S5, OFF

4  Comparison of Parameters Table 2 shows the comparison of parameters for different switch combinations. For circular polarization, 11110 and 11111 switch combinations are desirable, and for linear polarization, the other two combinations of the switches are selected.

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Fig. 5  3D gain plot for (a) S1,S2,S3,S4, and S5, ON (b) S1,S2,S3,S4, ON and S5, OFF

A Novel Compact Frequency and Polarization Reconfigurable Slot Antenna Using PIN… Fig. 6  Axial ratio plot for switch state 00001 and 11111(0, OFF; 1, ON)

93

50 45

00001 11111

AXIAL RATIO(dB)

40 35 30 25 20 15 10 5 0 7

8

9

10 11 12 FREQUENCY(GHz)

13

14

Table 2  Performance comparison for different switching states Switch state 00000 00001 11110 11111

Resonant frequency(GHz) 7.4,10.75 9.1,10.5 11.4 10.9

S11 (dB) −10.9,−13.2 −14.23,−19.36 −18.97 −27.42

Gain (dBi) 3 3 5 5

Axial ratio (dB) 45 30 2 1.5

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a Jsurf (A/m) 1.5720E+002 1.4673E+002 1.3626E+002 1.2580E+002 1.1533E+002 1.0486E+002 9.4395E+001 8.3927E+001 7.3460E+001 6.2992E+001 5.2525E+001 4.2058E+001 3.1590E+001 2.1123E+001 1.0656E+001 1.8811E–001

b Jsurf (A/m) 2.4797E+002 2.3146E+002 2.1495E+002 1.9844E+002 1.8194E+002 1.6543E+002 1.4892E+001 1.3241E+001 1.1590E+001 9.9391E+001 8.2882E+001 6.6374E+001 4.9865E+001 3.3356E+001 1.6847E+001 3.3857E–001

Fig. 7  J-surface plot for the switch state (a) 00001 (0, OFF; 1, ON) (b) 11111(0, OFF; 1, ON)

5  Conclusion A novel antenna design for polarization and frequency reconfiguration is presented. Microstrip patch antenna with diagonal slot and four L-shaped strip lines on the four corners of the patch is designed. The frequency reconfiguration is obtained by putting a switch on the diagonal slot, and polarization reconfiguration is obtained with the help of the four switches on the four corners of the patch antenna, which connect

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to the L-shaped strip lines. The simulated results indicate that both polarization and frequency reconfiguration are achieved. Frequency reconfiguration gives resonant frequencies in the X-band. Axial ratio less than 3 dB is also achieved for polarization reconfiguration. This antenna is useful in cognitive radio and satellite communication applications.

References 1. Jayaweera, S.K.: Distributed Reinforcement Learning based MAC protocols for autonomous cognitive secondary users”, (WOCC), 2011, pp.1–6. 2. Analysis and design of a reconfigurable antenna for ISM and GSM bands for CR applications, Fernando Lopez-Marcos, IEEE, 2015. 3. FCC Spectrum policy task force “Report of the spectrum Efficiency working group”, Technical Report, Washington DC, 2002. 4. Constantine, J.: Cognitive radio and antenna functionalities: a tutorial. IEEE APM. 56(1), 231–243 (2014) 5. Narlawar, M.S., Badjate, S.L.: A circular monople with a rectangular microstrip antenna for cognitive radio applications. IJIRSE. 2(4), 190–194 (2014) 6. Balanis, C.A.: Modern Antenna Handbook. Wiley, Somerset (2008) 7. Parihar, M.S., Basu, A., Koul, S.K.: Polarization reconfigurable microstrip antenna. Asia Pacific Microwave conference, December 2009 8. Abou Shahine, M.Y., Al-Husseini, M., Nasser, Y., Kabalan, K.Y., El-Hajj, A.: A reconfigurable miniaturized spiral monopole antenna for TV white spaces. In: PIERS Proc., pp. 1026–1029 (2013) 9. Ghosh, S., Srivastava, K.V.: Polarization-insensitive dual-band switchable absorber with independent switching. IEEE Antenna Wirel. Propag. Lett. 16, 1687–1690 (2017) 10. Zhao, X., Riaz, S., Geng, S.: A reconfigurable MIMO/UWB MIMO antennas for cognitive radio applications. IEEE Access. 7, 46739–46747 (2019) 11. Adnan, K., Tak, J., Siyari, P., Abdelrahman, A.H., Krunz, M., Xin, H.: A novel compact reconfigurable Broadband antenna for cognitive radio applications. IEEE Trans. Antenna Prop. 68(9), 6538–6547 (2020) 12. Rekha, S., Nesasudha, M.: Design of circularly polarized planar monopole antenna with improved axial ratio bandwidth. Microw. Opt. Technol. Lett. 59(9), 2353–2358 (2017)

Mathematical Analysis and Optimization of a Remodeled Circular Patch for 5G Communication Ribhu Abhusan Panda

and Debasis Mishra

1  Introduction As per the need of time, antenna designs have evolved faster than expected. In the past decade, there are many designs based on perturbed patch antenna for suitable applications. As soon as 5G applications are incorporated in technology, designs of planar antenna have taken shape with better efficiency. Novel planar antennas have been designed for 5G communications [1–4]. Antisymmetric L-shaped probe feeds have been included in the patch antenna for 5G application in the year 2018 [5]. Circular polarization and the revitalization of dielectric resonating antenna have been developed in the year 2019 [6, 7]. The 28/38 GHz frequency ranges have been considered for designing planar antennas in the year 2018 and 2019 [8–10]. The conventional patches have been modified in terms of design frequency and its corresponding wavelength for different applications. These modified structures resemble bicircular shape [11], biconvex shape [12], and biconcave shape [13]. Array of patches and fractal structure also have been designed for 5G application with novel analysis [14–16]. A prominent integration of antenna design with different optimization techniques has emerged in recent years. In 2020, hybrid topology optimization has been used for a patch with novel discontinuities in it [17]. In 2019, deep neural network has been implemented for an E-shaped patch antenna [18], and an equilateral triangle antenna has been designed with a soft computing-based model in the year 2018 [19]. In this paper, the mathematical approach to determine R. A. Panda () Department of Electronics and Communication Engineering, GIET University, Gunupur, Odisha, India e-mail: [email protected] D. Mishra Veer Surendra Sai University of Technology, Burla, Odisha, India © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 P. K. Malik et al. (eds.), Smart Antennas, EAI/Springer Innovations in Communication and Computing, https://doi.org/10.1007/978-3-030-76636-8_9

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the appropriate resonance frequency for a perturbed circular patch has been done on the basis of available theories of cavity model of circular patches. The working formula for the design of the patch is ascertained by machine learning algorithms like linear regression, polynomial regression, logistic regression, naive Bayes classifier, and decision tree. The dataset including different values of maximum arc-to-­ arc length is considered for optimization with different algorithms. A comparative study of results determined from different optimization algorithms is also reported. The design of the patch has been done on a substrate with dimension 40 mm×40 mm×1.6 mm, including FR4 epoxy material.

2  Mathematical Analysis of the Remodeled Circular Patch 2.1  Circular Disc Cavity For a disc patch with height “h” smaller than the radius, TMz modes of vibration (Z is taken perpendicular to the plane of the patch) can be considered in the cavity model for mathematical analysis. In a disc patch, the top and bottom parts of its metallization are bound by electric field, and the edge is bound by magnetic field. Because “h” is very small, the electric field is considered in Z-direction, and magnetic field is in ρ and φ directions represented in cylindrical coordinate system (CCS). The field inside the cavity can be calculated in terms of vector potential Az [20] as







− j ∂2 Az ωµ ∂ρ∂z

(1)

− j 1 ∂2 A2 ωµ ρ ∂φ∂z

(2)

− j  ∂2 2  2 + k  Az ωµ  ∂z 

(3)

1 ∂A z µρ ∂φ

(4)

1 ∂A z µ ∂ρ

(5)

Eρ =

Eφ = Ez =

Hρ =

Hφ = −

Hz = 0

(6)

Electric and magnetic field are denoted as Eρ, Eϕ, Ez, Hρ, Hϕ, and Hz, respectively, in cylindrical coordinate system. The wave equation is given by

∇ 2 Az + K r2 Az = 0

(7)

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where the magnitude of the propagation vector kr is given by

K r = ωr2 µ

(8)

The boundary conditions which are applicable for circular patch are

Eρ = 0 for 0 ≤ ρ ≤ r ,θ ≤ φ ≤ 2π , z = 0

(9)



Eρ = 0 for 0 ≤ ρ ≤ r ,θ ≤ φ ≤ 2π , z = h

(10)



Hφ = 0 for ρ = r ,θ ≤ φ ≤ 2π , 0 ≤ z ≤ h

(11)

2.2  Geometry of Proposed Design and Boundary Conditions The remodeled shape of the patch is, by geometry, the intersection of two circular shapes of radius “r” each, in such a way that the center of one circle lies on the circumference of the other, as shown in Fig. 1. The centers C1 and C2 are at distance “r,” the radius of the circle. The shape is a part of circular shape, so can be a circular waveguide. 2≠ This design is encircled by two arcs of length r. 3 The angle produced by the arc with the axis is

θ = cos−1

r 3 = cos−1 ≈ 170 πr π 3

(12)

The patch metallization is only in the region where “φ” varies between θ and π-θ. The magnetic field that is produced in the ρ,φ region of the patch is now a limited space. Thus, the boundary conditions become

Eρ = 0 for 0 ≤ ρ ≤ r ,θ ≤ φ ≤ π − θ , z = 0

Fig. 1  Geometrical representation of the proposed patch shape

(13)

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Eρ = 0 for 0 ≤ ρ ≤ r ,θ ≤ φ ≤ π − θ , z = h

(14)



Hφ = 0 for ρ = r ,θ ≤ φ ≤ π − θ , 0 ≤ z ≤ h.

(15)

2.3  Solution of Wave Equation Solving Eq. 7, the expression for magnetic vector potential Az is given by Az = BJ m ( k p ρ ) ( A2 cos mφ + B2 sin mφ ) cos kz Z





(16)

where B, A2, and B2 are constants m=0, 1, 2……; n=1, 2, 3 and are the values for different modes for vibration As k p 2 + kz2 = K r2 = ωr2 µ



(17)

Using boundary conditions (13, 14, 15), the result produced is J mn′ ( k p ρ ) = 0 When ρ = r





(18)

′ Considering X mn as the zeroes of the derivatives of Bessel’s function Jmn (kpρ), we get

′



kρ =

′ X mn r

(19)

Provided (A2 cos mϕ + B2 sin mϕ) ≠ 0 as coskzZ = 1 for z=0 As by the boundary condition Eqs. 13 and 14 the value of “φ” is limited, which is between 170 and 1630, m has the minimum value to produce resonance:



is

180 0 ⊕11 170

2.4  Resonance Frequency Using Eqs. 17 and 19, for the proposed biconvex patch, the resonance frequency can be calculated by the formula



fmnp =

′ X mn µ r

1 2π

(20)

Mathematical Analysis and Optimization of a Remodeled Circular Patch for 5G…

1

µ



=

c r

101

(21)

where “c” is the speed of light (EM radiation in air) and ϵr is the dielectric constant m of the patch material. Considering c = 3 × 108 and ϵr = 4.4 , n=1 and m=11: s ′ X = 12 . 826 (22) mn Taking r = 10.625 mm, fmnp = 27.47 GHz, which is established by the resonance frequency.

3  Optimization for Maximum Arc-to-Arc Length As explained in the previous section, the presence of a circular part in a design can be a circular waveguide. In this case, the shape is produced by intersection of two circles, and the possibility that the center of one circle falls on the circumference of the other is one of the many. The mathematics discussed in the previous section is feasible only when the maximum distance between two arcs is equal to the radius of ′ the circle. As stated in Eq. 20, the frequency of resonance depends on X mn and r as other factors are constant for the same substrate. Here, the variables are “m” and the arc-to arc distance “r”. With datasets that have been generated by simulation values, the algorithms can be employed to calculate “r.” The machine learning mathematics utilizes probability statistics to find out the best-suited value. There are different algorithms like linear regression, logistic regression, polynomial regression, naive Bayes classification, and decision tree. Each one has been explained in the following part.

3.1  Linear Regression This is a type of supervised machine learning algorithm that is used to analyze incessant range of data. It performs tasks on one dependent variable and one or more independent variable. If there is a single dependent variable, then simple linear regression occurs. Similarly, if there is more than one dependent variable, multiple linear regression occurs. This type of regression is used to find the linear relationship of both input and output variables. The hypothesis function of linear regression is ,

where

B = n1 + n 2.a (23) ,

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Fig. 2 (a) Linear regression for maximum arc-to-arc length, (b) logistic regression for maximum arc-to-arc length, (c) polynomial regression for maximum arc-to-arc length, (d) naive Bayes classifier, (e) decision tree, (f) comparative analysis of different algorithms

“a” = input data B’ = labeled data Ө1 = intercept Ө2 = coefficient of data

2π  r c , . A variation is produced , a = r, n1 = 0, n 2 = ′ f mn X mn which is represented in Fig. 2a. It is observed that in case of linear regression, the arc length varies linearly. The arc length and feed dimension have been considered as input training data and dielectric constant as output labeled data. The accuracy rate is more than 85%. The error rate of the proposed model has also been calculated. The most accurate value of arc length lies within the range of 10–11 mm, i.e., 10.85 mm. ,

Relating to Eq. 20, B =

Mean Absolute Error: 0.34947547432692666 Mean Squared Error: 0.15705959804731964 Root Mean Squared Error: 0.39630745393863037

3.2  Logistic Regression It is a type of supervised machine learning, which takes trained data as input and predicts the target value. It is binary in nature and only contains Boolean values, which are 0 and 1. It may contain unordered pair of data. It is of three types, binomial, ordinal, and nominal, but for the data, ordinal and binomial logistic regression can be considered. The mathematical equation uses sigmoid function:

Mathematical Analysis and Optimization of a Remodeled Circular Patch for 5G…

g (z) =



1 1 + e− z

103

(24)

g(z) is used to find the threshold value based on the dependent variable of the computed model. The plot, which has been illustrated in Fig. 2b, is obtained by using sigmoid threshold function. The arc length, line of feed, and dielectric constant are used for training and testing a model. Equation 20 can be remodeled as

λ 2 = a 2 k ′r

where k′ is constant and λ =

(25)

c . fmn

The accuracy is more than 90% and the best arc length value is nearly 10.99 mm. Here, the error rate is very less. Mean Absolute Error: 1.0 Mean Squared Error: 1.5714285714285714 Root Mean Squared Error: 1.2535663410560174

3.3  Polynomial Regression It is a regression analysis in which there is a relationship between independent input variables and dependent output variables. The output of the model is determined by the degree of the polynomial:

d = β 0 + β 1.i + n

(26)

where i = independent variable d = dependent variable β0 = an intercept β1 = slope coefficient n = error rate The plot, which has been shown in Fig. 2c, is obtained by considering the degree of polynomial function. The arc length, dimension of the feed, and dielectric constant of the substrate are used for independent and dependent value of the computational model. The accuracy is more than 97%, and the best arc length value is nearly 10.99 mm. Here, the error rate is very less. Mean Absolute Error: 0.23789618690576209 Mean Squared Error: 0.08814209614415353 Root Mean Squared Error: 0.29688734588081306

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3.4  Naive Bayes Classifier It is a conditional classifier based on probability statistics. The dataset evaluation can be determined by response vector and feature matrix. Bayes theorem for finding the probable values can be considered:

P ( A|B ) = P ( B|A ) .P ( A ) / P ( B )

(27)

where P(A|B) = posterior probability P(B|A) = likelihood function P(A) = prior probability P(B) = probability of B This uses the concept of probability statistics. The resultant plot is reported in Fig. 2d. The arc length, dimension of feed, and dielectric constant of substrate are used for input value, i.e., P(A), and output value, i.e., P(B), for the computational model. The accuracy is more than 81% and the best arc length value is nearly 10.78 mm. Mean Absolute Error: 1.7142857142857142 Mean Squared Error: 4.857142857142857 Root Mean Squared Error: 2.2038926600773587

3.5  Decision Tree It can be both supervised and unsupervised machine learning algorithm. Decision tree is classified based on regression and classification. It is a tree-type flow structures which consist of Internal Node: Attribute of model Branch: Output of the test data Leaf Node: Labeled data Decision tree algorithm is used to find the final value, and the plot that has been obtained by implementing this algorithm has been illustrated in Fig.  2e. The arc length and dimension of feed are input data variable, and the dielectric constant is the input value for model. The accuracy is more than 99% and the best arc length value is nearly 10. 98 mm. Hence, there is very acute average error. Mean Absolute Error: 0.5 Mean Squared Error: 0.5 Root Mean Squared Error: 0.707

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3.6  Performance Evaluation Mathematical model for the proposed patch has been analyzed by using different machine learning algorithms like linear regression, polynomial regression, logistic regression, naive Bayes classifier, and decision tree. The major internal parameters that are to be observed are arc-to-arc length, dielectric constant, and feed dimension. Evaluation of accuracy has been done, and also the error rate of the model is calculated. The accurate value of the arc length lies within 10–11. Different classifiers predict different values. It is observed that in polynomial regression, the accuracy rate is very high, i.e., 99%, minimizing the error rate. Root mean squared error (RMSE) is used to identify the deviation of data point from regression line. Mean squared error (MSE) is used to find the difference between the actual value and estimated values. Mean absolute error (MAE) is the absolute average value between actual and predicted values. In this case, the suitable arc length is 10.625 mm, which gives the best result for computing our model. The comparison statistics has been reported in Fig. 2f. As a result, of which it can be concluded that among all types of learning algorithms, polynomial regression gives accurate result.

4  Design of the Antenna Design has been done using HFSS software, and the design parameters have been shown in Fig. 3, and the dimensions are provided in Table 1. High-frequency structure simulator (HFSS) that includes finite element method is used for simulation.

Fig 3  Design using Ansys HFSS

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Table 1  Design parameters Parameters Maximum arc-to-arc length Substrate width Substrate length Ground-plane width Ground-plane length

Symbol r ws wl gw gl

Value (mm) 10.625 40 40 40 40

Fig. 4  S-parameter of the proposed antenna with resonance frequency of 27.8GHz and bandwidth of 5.2 GHz

5  Results Figure 4 highlights the resonance frequency, -10dB bandwidth, and return loss of the proposed patch. This result has been compared to four other results of the antennas, which have been designed for this frequency range for 5G communication. The comparison of works for the frequency 28 GHz has been shown in Table 2. The antenna gain is 4.01 dB at the frequency of 27.8 GHz, as shown in Fig. 5. The E-field and H-field polarizations have been shown in Figs. 6 and 7, respectively. Figure 8a indicates standing wave measured in terms of voltage with a value of 1.056. Radiation pattern in 3D and distribution of surface current have been shown in Figs. 8b and 8c, respectively.

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Table 2  Comparison of works at 28 GHz application

Work Ref 3 Ref 4 This work

Return loss S11 (dB) −18.25 −40.64 −39.13

Resonance frequency (GHz) 28.06 28 27.7

Bandwidth (GHz) 1.1 4.864 5.2

Antenna gain (dB) 6.8 5.75 4.01

Substrate material and its cost Roger RT5880, high Roger RT5880, high FR4 epoxy, low

Fig 5  Antenna gain at 27.7 GHz

6  Conclusion With theoretical approach including a mathematical derivation and analysis with different optimization algorithms, the appropriate dimension of a modified circular patch resembling biconvex shape is determined, which provides a sharp resonance frequency at 27.7  GHz with high gain. So, it can be used efficiently for 5G communication.

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Fig 6  E-plane polarization

Fig 7  H-plane polarization

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Fig. 8 (a) VSWR at 27.7 GHz having the value of 1.056, (b) 3D radiation pattern (c) Surface current distribution

References 1. Wong, K., Chang, H., Chen, J., Wang, K.: Three wideband monopolar patch antennas in a Y-shape structure for 5G multi-input–multi-output access points. IEEE Antennas Wirel. Propag. Lett. 19(3), 393–397 (2020). https://doi.org/10.1109/LAWP.2020.2967354 2. Lee, W., Hong, Y.-K., Won, H., Choi, M., Jeong, N.S., Lee, J.: Dual-band (5G millimetre and dedicated short-range communication) stacked patch antenna for advanced telematics applications. Microw. Opt. Technol. Lett. 61, 1–7 (2019). https://doi.org/10.1002/mop.31737 3. Goyal, R.K., Shankar Modani, U.: A compact microstrip patch antenna at 28  GHz for 5G wireless applications. In: 2018 3rd International Conference and Workshops on Recent Advances and Innovations in Engineering (ICRAIE), Jaipur, India, pp. 1–2 (2018). https://doi. org/10.1109/ICRAIE.2018.8710417 4. Ali, C.K., Arif, M.H.: Dual-band millimeter-wave microstrip patch array antenna for 5G smartphones. In: 2019 International Conference on Advanced Science and Engineering (ICOASE), Zakho – Duhok, Iraq, pp. 181–185 (2019). https://doi.org/10.1109/ICOASE.2019.8723719 5. Mak, K.M., Lai, H.W., Luk, K.M.: A 5G wideband patch antenna with antisymmetric L-shaped probe feeds. IEEE Trans. Antennas Propag. 66(2), 957–961 (2018). https://doi.org/10.1109/ TAP.2017.2776973 6. Mohanta, J., Meher, P.R., Behera, B.R., Mishra, S.K.: A circularly polarized hybrid plasmonic nanoantenna. Microw. Opt. Technol. Lett. 62, 278–283 (2020). https://doi.org/10.1002/ mop.32003

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7. Meher, P.R., Behera, B.R., Mishra, S.K.: Broadband circularly polarized edge feed rectangular dielectric resonator antenna using effective glueless technique. Microw. Opt. Technol. Lett. 62, 1–9 (2020). https://doi.org/10.1002/mop.32439 8. Ahmed, M.I., Marzouk, H.M., Shaalan, A.: A two-element microstrip antenna 28/38 GHz for 5G mobile applications. In: 2019 6th International Conference on Advanced Control Circuits and Systems (ACCS) & 2019 5th International Conference on New Paradigms in Electronics & information Technology (PEIT), Hurgada, Egypt, pp. 71–76 (2019). https://doi.org/10.1109/ ACCS-­PEIT48329.2019.9062881 9. Lee, S., Kim, S., Choi, J.: Dual-band dual-polarized proximity fed patch antenna for 28 GHz/39 GHz 5G millimeter-wave communications. In: 2019 13th European Conference on Antennas and Propagation (EuCAP), Krakow, Poland, pp. 1–5 (2019) 10. Rahayu, Y., Hidayat, M.I.: Design of 28/38 GHz dual-band triangular-shaped slot microstrip antenna array for 5G applications. In: 2018 2nd International Conference on Telematics and Future Generation Networks (TAFGEN), Kuching, pp. 93–97 (2018). https://doi.org/10.1109/ TAFGEN.2018.8580487 11. Panda, R.A., Mishra, D.: Efficient design of bi-circular patch antenna for 5G communication with mathematical calculations for resonant frequencies. Wirel. Pers. Commun. 112, 717–727 (2020). https://doi.org/10.1007/s11277-­020-­07069-­9 12. Panda, R.A., Dash, P., Mandi, K., Mishra, D.: Gain enhancement of a biconvex patch antenna using metallic rings for 5G application. In: 2019 6th International Conference on Signal Processing and Integrated Networks (SPIN), Noida, India, pp.  840–844 (2019). https://doi. org/10.1109/SPIN.2019.8711581 13. Panda, R.A., Panda, M., Nayak, P.K., Mishra, D.: Log periodic implementation of butterfly shaped patch antenna with gain enhancement technique for X-band applications. In: Gunjan, V., Garcia Diaz, V., Cardona, M., Solanki, V., Sunitha, K. (eds.) ICICCT 2019  – System Reliability, Quality Control, Safety, Maintenance and Management. ICICCT 2019. Springer, Singapore (2020) 14. Dzagbletey, P.A., Jung, Y.: Stacked microstrip linear array for millimeter-wave 5G baseband communication. IEEE Antennas Wirel. Propag. Lett. 17(5), 780–783 (2018). https://doi. org/10.1109/LAWP.2018.2816258 15. Shen, X., Liu, Y., Zhao, L., Huang, G., Shi, X., Huang, Q.: A miniaturized microstrip antenna array at 5G millimeter-wave band. IEEE Antennas Wirel. Propag. Lett. 18(8), 1671–1675 (2019). https://doi.org/10.1109/LAWP.2019.2927460 16. El-Khamy, S.E., Zaki, A., Hamdy, S., El-Khouly, A.: A new fractal-like tree structure of circular patch antennas for UWB and 5G multi-band applications. Microw. Opt. Technol. Lett. 59, 2168–2174 (2017). https://doi.org/10.1002/mop.30707 17. Zhu, S.-H., Yang, X.-S., Wang, J., Wang, B.-Z.: Miniaturization of patch antenna based on hybrid topology optimization. Int. J.  RF Microw. Comput. Aided. Eng. 30, e22308 (2020). https://doi.org/10.1002/mmce.22308 18. Ustun, D., Toktas, A., Akdagli, A.: Deep neural network–based soft computing the resonant frequency of E–shaped patch antennas. AEU Int. J.  Electron. Commun. 102, 54–61, ISSN 1434-8411 (2019). https://doi.org/10.1016/j.aeue.2019.02.011 19. Kayabasi, A.: Soft computing-based synthesis model for equilateral triangular ring printed antenna. AEU Int. J. Electron. Commun. 94, 332–338, ISSN 1434-8411 (2018). https://doi. org/10.1016/j.aeue.2018.07.030 20. Balanis, C.A.: Antenna Theory: Analysis and Design. Wiley, New York (2012)

Study of Various Beamformers and Smart Antenna Adaptive Algorithms for Mobile Communication Elizabeth Caroline Britto, Sathish Kumar Danasegaran, Susan Christina Xavier, A. Sridevi, and Abdul Rahim Sadiq Batcha

1  4G/5G Technology In today’s economy and lifestyles, mobile connectivity plays a critical role and has grown rapidly over the last few decades. In the 1980s, the first generation (1G) was deployed and provided speech chat, which was the only 1G operation. It was based on analogue methodology [1, 2]. It had a simple mobile connectivity structure and basics such as cellular architecture adoption, frequency band multiplexing, domain roaming, mobile communication without interruption, etc. During the 1990s, the second-generation wireless mobile infrastructure [3] based on digital cellular networks was a major success for global mobile connectivity systems. In October 2001, the third-generation system was launched in Japan [4] to offer data service speeds of 144–384 kbps and 2 Mbps, respectively, in areas of outdoor and outdoor coverage. A word used to characterize the next full evolution of wireless connectivity is the fourth generation (4G), also known as beyond 3G. [5]. A 4G framework will be able to offer a robust alternative to the Internet protocol, where users will be provided E. C. Britto (*) · S. K. Danasegaran Department of ECE, IFET College of Engineering, Villupuram, Tamil Nadu, India S. C. Xavier Department of ECE, MAM College of Engineering and Technology, Tiruchirappalli, Tamil Nadu, India A. Sridevi Department of ECE, M. Kumarasamy College of Engineering, Karur, Tamil Nadu, India e-mail: [email protected] A. R. S. Batcha Department of EEE, Mahsa University, Mahsa, Malaysia e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 P. K. Malik et al. (eds.), Smart Antennas, EAI/Springer Innovations in Communication and Computing, https://doi.org/10.1007/978-3-030-76636-8_10

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with voice, data, and streamed multimedia content on an “anytime, anywhere” basis and at faster data speeds than previous generations. This includes automatic roaming between various networks, as well as user transparency. 4G will be able to offer both indoor and outdoor speeds of between 100 Mbps and 1 Gbps, with premium content and high security. The two candidates for 4G coverage are actually universal interoperability for microwave connectivity [6, 7] and long-term evolution [8, 9]. 5G will be substantially better than 4G, providing up to 20 Gigabits per second (Gbps). While large-scale MIMO would improve spectrum and data bandwidth utilization by 5G [10, 11], it is not easy to integrate multiple antenna systems into a very tightly spaced cell phone. In response to the diversity antenna and 4G main antenna, 5G mobile antenna packages would support additional operational bands and resonant modes, which is a challenging problem for the 5G mobile antenna design, taking into account the future requirements for large-scale multiband and multimode MIMO implementations.

1.1  Multiple-Input Multiple-Output A single antenna for transmission and a single antenna for reception are used by conventional wireless communication networks. These systems are classified as single-input and single-output (SISO) systems, and Fig. 1 indicates one such system. Important improvement has been made in the development of systems seen in Fig.  2 in recent years, which use multiple transmitter and receiver antennas to achieve improved performance. These schemes are called MIMO systems. In broadband wireless networking, MIMO has recently gained interest, as it provides a substantial improvement in data throughput and connectivity range without extra bandwidth or transmitting power. This is accomplished by higher spectral efficiency (more bits per second per bandwidth hertz) and stability or variety of connections (reduced fading). Due to its uses [12] in satellite media, cellular local area networks, regional area networks, and mobile networking, MIMO technology has provoked concern. Multiple users can connect at about the same time and/or speed in a cellular wireless communication network. The more time and frequency resources are reused more efficiently, the greater the performance of the network, given that the broadcast signals can be accurately detected. The time (time-division) or frequency (frequency-­division) or code will distinguish different users (code-division). In MIMO networks, the spatial dimension creates an extra dimension to differentiate consumers, allowing frequency and time resources to be utilized more vigorously, therefore increasing network bandwidth. Fig. 1  SISO wireless systems

DSP

RF TX

RF

DSP RX

Study of Various Beamformers and Smart Antenna Adaptive Algorithms for Mobile… Fig. 2  MIMO wireless systems

RF1

RF1 DSP

DSP RFNt

RFNr

TX

Fig. 3  Smart antenna types (a) Switched beamformer (b) Adaptive beamformer

a

113

RX

b

Spatial multiplexing(SM) and spatial diversity (SD) characterize MIMO systems. Signal copies are sent or obtained from more than one SD antenna [13]. With SM [14, 15], the device concurrently retains over than one spatial source of data onto one frequency over antenna elements. SM reaches higher capability [16], but improved signal efficiency lags behind it. SM is forced to its limits, especially in extensive network areas, as it demands high signal power, while SD increases signal quality increases and the receiver side achieves a higher signal-to-noise ratio.

1.2  Smart Antenna System A rising market for heterogeneous broadband services and applications would have to be met by future mobile connectivity systems. It needs to provide high data rate connectivity for growing wireless users, given the restricted bandwidth available. The implementation of smart antennas is bound to enhance the total capacity and efficiency of the device. In order to refine the transmitting and reception beam patterns automatically, a smart antenna [17] integrates multiple antenna components with a signal processing power. Smart antenna development [18, 19] provides a dramatically improved approach that decreases the amount of interference and improves the range of linking and enables channel frequency reuse. With this technology, the signal from each device is sent and received only in the direction of that specific user by the base station (BS). This significantly decreases the power budget of the connection as well as the total system intrusion. For each user in the system, a smart antenna unit is composed of an array antenna controlling different communication beams. Smart antennas, as seen in Fig.  3, are split into two classes. One approach is referred to as switched beamforming [20–23] if the complicated weights are chosen in unique, predetermined positions from a library of weights that shape beams. In this method, based on the obtained wireless signal observations, BS essentially

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switches between different beams. The other approach is called adaptive beamforming [24, 25], in which the weights are measured in real time and adaptively modified. The BS shapes broader beams into the target user by adaptive beamforming and nullifies the intervening users, greatly increasing the ratio of signal-to-interference-plus-noise. Smart antenna transmitters encrypt separate data streams on various paths, maximizing the data rate or redundantly encoding data on paths that fade individually to shield the receiver from ruinous fades of the signal. This leads to an improvement in the efficiency of the signal by more oriented propagation and also increases frequency reuse capability. For a fixed number of customers and perhaps more devices for a given data rate per account, this improved flexibility would contribute to higher data rates. The utilization of smart antenna technologies allows clients to expand their spectrum, enhance coverage efficiency, and allow more optimal use of channel and bandwidth capacities with almost any wireless communication system. Smart antenna systems include the benefits and features [26] of signal gain, greater range, rejection of interference, improved performance, multipath rejection of spatial diversity, power quality, and decreased service costs.

2  Beamforming Technology Beamforming engineering experiments have provided insight into the motives and implications of this study and are contrasted to newer technologies. This segment consists of simple phased antenna array (PAA), beamforming network, and various beamforming developments.

2.1  Phased Array Antenna Fundamentals The phased array antenna (PAA) [27–30] consists of an array of radiating elements, each with a phase shifter that enables the transmitting and/or receiving of electromagnetic waves through adequate integrated circuits. The array consists of two or three components of the antenna as seen in Fig. 4. They are spatially organized and electrically interconnected to create a directional pattern of radiation. Interconnection between the components, called the feed network, will include the fixed phase of each element and thus the name of the phased array. To form a single array output, the signals induced by multiple elements of an array are combined. It is claimed that the direction of the beam pointing is the direction in which the array has maximum reaction, and so it is the direction in which the array has maximum gain. In order to steer the beams in the direction required, beams are created to provide constructive/destructive interference by adjusting the phase of the signal generated from each radiating unit. The phase shift φ between

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Main Direction θs

x

x d

ϕ

8

x d

ϕ

7

x d

ϕ

6

x d

ϕ

5

x d

ϕ

4

x d

ϕ

3

d ϕ

ϕ 2

Phase shifters 1

Fig. 4  Phased array components

two consecutive components, as shown in Eq. (1), is constant and is called phase increment:





360 d sin  s   (1)

where φis the phase change between two consecutive elements,dis the range amid the two radiating components, and θs is the beam navigation angle. The major advantages of PAA are the low side lobes’ high gain width, the ability to allow the beam to jump in a few microseconds and system power from one target to the next, and modes of tracking or sensing and multipurpose operation by emitting several beams. While PAAs have significant advantages over mechanically operated antennas, such as shifting speed and durability, issues of height, weight, cost, and complexity have hindered traditional phased array antennas. As the PAA for beamforming is used in fixed locations, there is no power over phase and amplitude of the signal induced between the different elements of the array.

2.2  Beamforming Network Beam-steering and beam-shaping circuits are referred to as beamforming networks (BFN). BFN integrates the arrays of antenna with signal processor to dynamically redirect the signal in retort to the orientation of arrival to pick up the signal and to isolate the signal from the location of disturbance. BFN can perform a lot of purposes such as beam-guiding, beam-shaping, beam-grinding, and multibeam transmission. Signal magnitude and phase are governed independently by the BFN according to the propagation of the signal in the expected direction. First, the number of antenna components with an electrical power splitter separates the input electrical signal to be distributed. Nonetheless, where high-bit rate signals are considered, electrical BFN has significant disadvantages. Electrical circuits tend to be dense,

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lossy, heavy, and more sensitive to electromagnetic interference working at these higher frequencies. Three beamforming techniques for array antennas are known as RF, digital, and optical beamforming [31, 32] technique.

2.3  RF Beamforming Method The most popular technique is RF beamforming, which is commonly used in small-­ scale structures [33]. Figure 5 shows the simple beamforming network design using RF technologies, assuming that there are M input beams and N output components in a multibeam transmission array antenna. The standard type of matrix network includes M × N phase-shifter elements, attenuators, and linkages to regulate the phase and magnitude of the received signals and redirect the orientation of the consumer. However, it has the downside that the hardware architecture becomes complicated and cumbersome, and thus, costly hardware is required for large-scale systems as the size of the antenna is increased.

Antenna Elements

Attenuator

Phase shifter

Fig. 5  RF beamforming method setup

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2.4  Digital Beamforming Method Signal processing is performed in an arithmetical format for the automatic beamforming procedure, where highly scalable algorithms [34] are used to modify the signal received at the BS. To form a very narrow beam against individual users in the cell, this technology incorporates the inputs of multiple antennas. Figure 6 displays the basic configuration of the digital network for beamforming. The obtained data are received digitally and require up-/downconverters and analogue-to-digital converters in parallel. However, the digital computer’s speed limits the signal bandwidth to 100 MHz [35].

2.5  Optical Signal Processing Beamforming Method Optical signal processing beamforming network (OSPBFN) provides both signal delivery and optical domain processing functionality. The approach of optical signal processing (OSP) substantially decreases the difficulty and speed of the traditional device. Using OSPBFN techniques in the BS, the limitations described in electrical BFN are overcome. For example, the optical frequency is reasonably greater than the RF frequency by several folds; the OSPBFN itself is independent of the RF

Antenna Elements

up/down converter

up/down converter

Analog to digital converter

Analog to digital converter

up/down converter

Analog to digital converter

Parallel Digital signal Processing

Fig. 6  Digital beamforming techniques

up/down converter

Analog to digital converter

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frequency. Due to the obvious optical elements, benefits such as large bandwidth, low mass, compact size, and sensitivity to electromagnetic interference are commonly accepted. Furthermore, because of the use of parallel signal processing, the number of hardware components M x N is diminished to M+N in the category of RF-BFN. By way of spatial sequential signal processing, an OSP in a BFN achieves the desired magnitude and phase variation for each array element. Individual optical carriers at the control station correctly modulate the data corresponding to each beam. These optical upconverted messages are transmitted through the optical fiber to the base station (BS). An optical equivalent carrier is sent by another fiber to BS as well. Each modulated optical signal is processed at BFN in the BS with spectral conversion, and then converted RF signal is obtained by the heterodyne method using optical backing carrier. In order to reach individual mobile terminals, the multibeam antenna nurtured by the transformed RF signals emits alone beam. Figure 7 displays the condensed diagram of OSPBFN for eight antenna components. The number of antenna components with an optical power splitter separates the optically modulated input signal to be sent to the BS. These signals are connected to amplitude controls, which regulate each signal’s amplitude levels and ultimately decide the shape of the transmitted beam (i.e., the main lobe beam width and the side lobe power levels) and are called beam-shaping operations. By adjusting the amplitude of the optical signal applied to each antenna part, beam-shaping is accomplished. This is achieved through optical attenuators in operation. An optical phase shifter, which controls the phase of each signal and sets the direction of the transmitted wave, is then related to each of the amplitude-regulated signals. The location of the transmitted signal is determined by the differential phase delay. This process is called steering with beams. Finally, after downconversion to electrical signal by a picture detector, the individual controlled signals are added to their respective element and sent out to the end-user.

3  Overview of Existing OSPBFN Many applications like ad hoc mobile communication, remote-controlled networks, wireless satellite links, and 4G/5G handheld devices require the extensive use of multi-antenna technologies with active phased array antennas. Most of the

Laser Source

Electro-optic modulator

1*8 Optical power splitter

Amplitude Modulator as Beam shaping section

Electrical input signal to be transmitted

Fig. 7  Basic schematic diagram of an OSPBFN

Phase Controller as beam-steering section

Photo detector

1*8 antenna

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signal processing algorithms used are based on arrival direction, and another technique is adaptive beamforming algorithm. Usually in the available systems, the arrival direction calculation algorithm is used first to calculate the incoming signal direction of arrival; after that, system parameters are updated with the help of adaptive beamforming algorithms. MMIC (monolithic microwave integrated chip) methods require very complex, heavy, and costly beamforming networks to arrange a great number of beams (BFNs). Although there has been a great deal of activity in the research and development of digital-based BFNs, bandwidth is still minimal. The application of optical or photonic [36] technologies to microwave array antennas has been researched over the past few decades. Optically controlled smart antenna techniques are based on Fourier optics, fibers [37–46], optical delay element [47–53], acousto-optic [54], fiber-optic prism [55], spatial light modulator, spatial Fourier optical processing approach [56], chirped fiber gratings, microelectromechanical system-spatial light modulation (MEMS-SLM) [57, 58], fiber optic dispersive prism [59], and micro-ring resonator [60] and liquid crystal-based beamformer. The amplitude and phase errors (tracking) of all subsystems within the frequency spectrum of interest are a crucial requirement within the OSPBFN. The radiated beam pattern that influences the average and peak side lobe levels and the precision of the beam aiming is specifically influenced by this definition.

4  Beamforming Algorithm The smart antenna array is an amalgamation of different structured antenna part arrays and digital signal processing techniques, adapting its weights to the common parameter and adaptive algorithm types. The main goal of the beamforming is to reduce the co-channel interference and methods of assigning the weight for the algorithm [61]. Few quasi-algorithms like least mean square (LMS), minimum variance distortionless response (MVDR) algorithm, normalized least mean square (NLMS), sample matrix inversion (SMI), constant modulus (CMA) algorithm, recursive least square (RLS) and hybrid least mean square algorithm/SMI (LMS/ SMI), maximal directivity (MD) algorithm, and hybrid MD/SMI algorithm, which can be related by changing the number and displacement of radiating elements between the array elements. There are many performance parameters to be measured, like stability of beam formation, width of the beam, maximum achievable level of side lobes, null depth, and rate of convergence. All these algorithms work on deciding and assigning the complex weights for every signal value, in which it generates narrow beams for deliberate users and deep nulls in the direction of interference.

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4.1  LMS Algorithm The use of this LMS algorithm to approximate the optimum conditions of an array is normal, and its research has been of significant interest for some time. By computing the mean of the quadratic mean square error (MSE) surface and then adjusting the values by a small amount in the reverse direction of the gradient, the algorithms change the weights for each iteration. The constant that defines this quantity is known as the size of the phase. If the step size is relatively small, the process contributes to suitable weights for such approximate weights. A real-time, unregulated LMS algorithm is given to evaluate the optimum device WMSE using the reference signal:

 n  1  s  n    g  s  n   (2)

where s(n + 1) represents the original weights computed at the (n + 1)th reiteration, μis an optimistic scalar, and g(s(n)) is an impartial assessment of the MSE gradient. For a presumed s(n), the MSE is quantified by



2   s  n    E ( r  n  1   s H  n  Rs  n   s H  n  z  z H s  n    (3)

The gradient of MSE at the nth iteration is found by distinguishing the above equation wrt w, yielding

 w  s   2 Rs  n   2 z

(4)

At the (n + 1)threpetition, the array is operating with weights s(n) calculated at the earlier reiteration; however, the array signal direction isx(n + 1), the reference signal illustration is r(n + 1), and the assortment output is

y  s  n    s H  n  x  n  1

(5)

The algorithm contains three steps in each recursion: • Compute the processed signal with the current weights. • Generate the error between the processed signal and the desired signal. • Adjust the weights using the new error information by the gradient method [11]. For each iteration in VSLMS algorithm, the step-size parameters of weights are updating [68]; variable step-size adaptive algorithms like variable step-size LMS (VS-LMS), variable step-size sign LMS (VS-SLMS), and variable step-size normalized LMS (VS-NLMS) are made with the variation of antenna elements and spacing between them. The purpose of data reusing the least mean square (DRLMS) is to increase the convergence rate by reusing the same dataset (i.e., input and reference signal) many times. DRLMS adaptive algorithm reuses the same dataset (n)

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input and t(n) desired L time at the same time index n. The DRLMS algorithm with L data reuse and coefficient is modified.

4.2  MVDR Algorithm The aim is to maximize the response of the beamformer in such a way that the output involves minimal contributions owing to noise and signal coming from places besides the signal line expected. A linear filter vector is desired for this optimization procedure; it is an explanation to the limited minimization s(f, θ)topic that agrees  signals from the 2direction of the look to pass with a defined gain:  MV  s  fi ,  R  fi  n  s  fi ,  , Minimize: subject to 

where

s  fi ,  D  fi ,   1

D  fi , 

(6)

is the conventional steering vector. The solution is given by s  fi , ,  



R 1  fi  D  fi , , 

D   fi , ,  R 1  fi  D  fi , , 

(7)

It delivers adaptive steering vectors for the N hydrophone line array beamforming of the received signals. Then, the adaptive beam at a steering θs is defined in the frequency domain by 

B  fi ,   s  fi ,  x  fi 



(8)

4.3  RLS Algorithm The computational burden of the LMS algorithm varies on the array correlation matrix’s actual values. In a framework that delivers an array correlation matrix with massive eigenvalues, the clustering is based at a slow rate. With the RLS algorithm, this problem is solved by substituting the gradient phase size μ with a gain matrix R−1(n) at the nth iteration, generating the equation for weight update:

s  n   s  n  1  R 1  n  x  n     s  n  1 

−1 where Rn is given by



Rˆ  n    0 Rˆ  n  1  x  n  x H  n 



(9)

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  0n  k x  k  x H  k 



k 0

(10)

with δ0 denoting a real scalar less than but close to 1. This is used for past data exponential weighting δ0, which is referred to as the forgetting factor, as the equation of the update appears to deemphasize the old samples. This is being used for exponential grading of past results δ0, which is known as the forgotten factor, as the update equation tends to deemphasize the old datasets. The quantity 1/(1 − δ0) is in general denoted to as the algorithm memory. So, the memory of the algorithm is close to 100 samples for δ0 = 0.99. Using the previous samples and the present samples, the RLS algorithm updates the necessary inverse as



Rˆ 1  n  1 x  n  x H  n  Rˆ 1  n  1  1  Rˆ 1  n    Rˆ 1  n  1   ˆ  0   0  x H  n  R 1  n  1 x  n   (11) The matrix isadjustedas



1 Rˆ 1  0   I e ,  0  0 0

(12)

4.4  CMA Algorithm Using the LMS algorithm, adaptive beamformer typically minimizes array performance power subject to constraints. There are two important shortcomings with these beamformers. At the beginning, the two signals are mutually associated; they appear to cancel the signal of interest along with the disturbance. In multipath contexts, this has discouraged its use. Second, they are especially susceptible to imperfections in the array. Any of the above alignments does not suffer from the CMA. It is unaffected by correlated source issues since it does not use output power minimization to adopt the array weights. Similarly, to set a constraint, it does not depend on array geometry or benefit functionality and is thus unaffected by array imperfection. Such two benefits make the CMA an enticing choice for traditional adaptive beamformers. CMA is gradient-based and operates under the basis that current interference induces array output amplitude changes that otherwise have constant modules. By decreasing the price features, it updates the weights:



J n 

Using the following equation,



2 1  E  y  n   y0 2 2 

  (13) 2

Study of Various Beamformers and Smart Antenna Adaptive Algorithms for Mobile…

s  n  1  s  n    g  s  n  



123

(14)

where y(n) = sH(n)x(n + 1) is the array output after the nth iteration, y0 is the necessary amplitude in the lack of imperfection, and g(s(n))signifies an estimate of the cost function gradient. Similar to the LMS algorithm, the CMA uses an estimate of the gradient by changing the true gradient with an instant value given by g  s  n    2  n  x  n  1



where





(15)



  n   y  n   y0 2 y  n  2

(16)

The weight update equation of this case suits s  n  1  s  n   2   n  x  n  1



(17)

In appearance, this is similar to the LMS algorithm with reference signal where ε(n) = r(n) − y(n). CMA suitable for eliminating correlated arrivals is an operative constant modulated enveloped signal.

4.5  MD Algorithm For adaptive beamforming in mobile communication, the maximum directivity (MD) algorithm [62] is used to measure these magnitudes and phase weights. Beamforming is usually carried out by complicated weighting and combing the distinct antenna signals. This results in the array element G (𝛳), which defines the characteristic of the antenna array’s spatial radiation. In this way, it is possible to adjust the angular distribution of the radiation intensity in the transmit case and the sensitivity in the receive case to the respective parameters. The yield of the beamformer is assumed by M

G    sm e



j  m 1 sin  

m 1

(18)

∗ m

w where is the complex weight that desires to be adjusted to optimize the radiation pattern and M is the number of the antenna components of the array. Generally, the number of nulls will usually differ from 0 to M-1. Equation (17) effects in the more general expression: M



G    sm gm   m 1

(19)

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where gm(θ)is the radiation features of array elements. The face of the complex factor of weight can be written as sm  bm e



 j  m 1 a

(20)

where Ωa =  − π sin ψis the normalized wave number in azimuth direction and ψ is the azimuth angle and bm is the magnitude of the signal. In the special case of eight antenna elements, one look direction θLDand K null directions θ0K1 ≤ k ≤ K with K between 1 and 7 are given. The linear equation system (LES) can be written as



 G  LD    g1  LD  g2  LD     G    01    g1  01  g2  01   .   . .    . .  .    G     g   g   0 K 8 x 1 2 0K   1 0K

. . . . .

. g8  LD    s1  1      . g8  01    s2  0   .  . . .      . .   .  .    . g8  0 K  8 x 8  s8 8 x1  0 8 x1 (21) 

In the corresponding angular direction, each row of the LES defines the constraints. The LES has a differing number of rows due to the variance of null paths. The built beam pattern is the best solution for the uplink channel of mobile communication systems due to optimum directivity. The value of this algorithm is that, simply by solving an LES, it produces the optimal solution. The complex weights of the antenna array components are determined using unit response in the direction of the look in this algorithm, which maximizes the output signal-to-noise ratio (SNR). So this algorithm steers the peaks of the main lobe in the direction of the look and minimums of the side lobes in the directions of interference while preserving maximum directivity.

Table 1  LDs and NDs for two simultaneous signals using MD algorithm Radiation pattern Figure 8a Figure 8b Figure 8c Figure 8d

Signal S1 S2 S1 S2 S1 S2 S1 S2

LD 20 −20 37 −40 55 −55 25 03

ND1 37 42 20 25 04 −40 50 25

ND2 0 02 0 −10 16 −16 11 −15

ND3 −22 78 −20 07 −12 12 −36 45

ND4 −37 15 −57 10 32 −04 −65 −45

ND5 65 -65 63 −65 35 32 −22 −60

ND6 48 60 −38 45 −55 55 72 60

ND7 −70 −32 −72 −25 80 −80 −08 80

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5  Result and Discussion Using the MD/SMI algorithm, the beams are steered from +60° to -60°. Thus the beam steering covers a 120° sector for a cellular base station. A maximum error of 5.5% in the beam direction occurs for look directions beyond +55° and -55°. The desired look direction (LD) and null direction (ND) are tabulated in Table 1. In these examples, the antenna’s simultaneous look directions for two beams are chosen as (20°,−20°), (37°,−40°), (55°,−55°), and (25°, 03°). The gain difference between the main lobe and the side lobes is found to be −10 dB. For two sets of LDs and NDs, the radiation patterns are plotted in polar coordinates (Fig. 8a, b) and in rectangular coordinates (Fig. 8c, d). From the figures, it is clear that the nulls are found to be at the exact angles of the given interference. Table 2 depicts the comparisons between different adaptive beamforming algorithms. The significances of MD algorithm are observed as follows: this algorithm gives the maximum directivity, which results in a minimum bit error rate for the reverse link of a CDMA-based mobile communication system. The algorithm provides an optimum solution for arbitrary spaced constraints while maintaining a maximum possible directivity and doesn’t require additional reference signal. The

a

90 0.8

120

0.6 0.4

120

180

0

240

270

330

270

300

Signal1=(37;20,0,–20,–57,63,–38,–72) Signal2=(–40;25,–10,71,0,–65,45,–25)

Azimuth angle in degree

d

0

–10

–20

–20

signal1 signal2

Amplitude in dB

Amplitude in dB

0

240

300

Signal1=(20;37,0,–22,–37,65,–48,–70) Signal2=(20;42,02,78,15,–65,60,–32)

–10

–30

–30

–40

–40

–50

–50 –60 –70

30

210

0

signal1 signal2

60

180

Azimuth angle in degree

c

0.6 0.2

330

210

90 0.8 0.4

150

30

0.2

Amplitude

Amplitude

150

b

signal1 signal2

60

signal1 signal2

–80

–60

–60

Signal1=(55;04,16,–12,–32,35,–55,70) Signal2=(–55;35,–16,12,–04,32,55,–70)

–40 –20 0 20 40 Azimuth angle in degree

60

80

–70

Signal1=(25;50,11,–36,–65,–22,72,–08) Signal2=(03;25,–15,45,–45,–60,60,80)

–80 –60

–40 –20 0 20 40 Azimuth angle in degree

60

80

Fig. 8  Radiation patterns with different LDs and NDs for two simultaneous signals (a) LD (20, −20), (b) LD (37, −40), (c) LD (55, −55), and (d) LD (25, 03)

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Table 2  Comparison of beamforming algorithms [61, 63–71]

Algorithm VSLMS VS-SLMS VS-NLMS DRLMS

LMS

MVDR RLS CMA MD

Hybrid LMS/(SMI)

Maximum in desired direction and nulling the interfering signal Maximum signal strength in the user direction Not available

Required

Scan BER sector (°) Minimum −60 to +60 Normal −60 to +60 Minimum −60 to +60 Low −50 to 50

Required

High

Required

High

Interference rejection better Interference rejection good Interference rejection best

Required

Amplitude response Interference rejection good Interference rejection good High directivity

Reference signal Required Required Required

Not required Not required

Hybrid LMS and SMI Required

−50 to 50

+52 to −52 Low Not available High −55 to +55 Minimum −60 to +60 Minimum −60 to +30

Convergence rate / computation Slow convergence Faster Less computation Faster

Slow/less computation Faster Faster/ more computation Not available Not available/less computation-­ solving LES Small time to converge less computation

weights can efficiently be calculated solving a set of LES. The approach can easily be extended to apply for three-dimensional beams as well.

6  Conclusion In this article, various beamformers and beamforming algorithms are discussed and are capable of providing 3G/4G/5G wireless mobile applications in areas such as channel bandwidth (frequency reuse), distortion elimination, power budget linking, and high-speed networking. The analogy of various beamforming algorithms for smart antennas was the idea of a fractal sequence of MD algorithms whose performance is analyzed. It also decreases memory requirements to a larger degree. Optical beamformers are known to provide ultrafast multibeam control for smart antennas with an optimized radio link between the BS and the MS. Acknowledgment  We are gratefully thankful to the reviewers for their critical comments and suggestions to improve the quality of the book chapter.

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Microstrip Patch Antennas: Past and Present State of the Art Manish Sharma

1  Introduction Research for microstrip-fed antennas took an exponential rise when the US Federal Communications Commission (FCC) in 2002 designated ultra-wideband unlicensed bandwidth of 3.10 GHz–10.60 GHz. The UWB bandwidth constituted the features such as application for short-range wireless communication, increase in the transfer of data with high speed, utilization of very low power of consumption for its operation, very compact size of the antenna useful for its operation and for UWB applications, and ease of fabrication of the prototype which is applicable for different imaging applications [1]. The UWB technology is well suited for applications including WPAN (wireless personal area networks), WBAN (wireless body area networks), WUSB (wireless universal serial bus), WSN (wireless sensor networks), RFID (radio frequency identification), robotics, LTS (location tracking systems), surveillance system, etc. The near-field and far-field results are well maintained including stability of radiation patterns, larger bandwidth ratio, very low profile, and simplest geometry. Generally, radiating patches such as circular-, semicircular-, square-, rectangular-, triangular-, elliptical-horizontal-/vertical-, crescent-shaped radiators and fractal geometries (Sierpinski, Minkowski) are few to name them. It has been observed that the existing wireless communication module does interfere with the operating bandwidth of UWB, and hence the need for bandstop filters is required. These interfering bands are worldwide interoperability for microwave access, wireless local area network, and satellite uplink/downlink frequency bands. Also, the UWB overall working module requires no power amplifier due to the M. Sharma (*) Chitkara University Institute of Engineering and Technology, Chitkara University, Punjab, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 P. K. Malik et al. (eds.), Smart Antennas, EAI/Springer Innovations in Communication and Computing, https://doi.org/10.1007/978-3-030-76636-8_11

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lower-power requirement features of UWB systems, and the UWB antenna is capably attaining as high as 20 Mb/s data rate speed. To eliminate the abovesaid interference, various technologies have been reported which are discussed in the upcoming sections. Section 2 addresses various UWB monopole antennas. Sections 3 and 4 discuss single- and dual-band-notched UWB antennas with extended bandwidth. Section 5 also represents the triple-, quadra-, and penta-band-notched characteristics of UWB antennas. Section 6 represents the characterization of various UWB antennas in frequency, time, and space domain.

2  UWB Antennas Microstrip patch antennas have a narrow bandwidth. To enhance the bandwidth from narrow to wide, two techniques have been reported, i.e., impedance matching and multiple resonances. Antennas with various radiating shapes along with modified ground plane to cover UWB bandwidth are studied by researchers on a different substrate like RT/duroid 5880/5870, FR4, and silicon with a dielectric constant of 2.2, 2.3, 4.4, and 11.9, respectively [2–16].

2.1  Microstrip Feed Figure 1a–w shows different shape UWB antenna configurations covering FCC-­ specified impedance bandwidth (3.1  GHz–10.6  GHz) with fractional impedance bandwidth of 109.48%. The shape of the designed radiating patches is square, rectangle, triangle, circular, annular ring, elliptical (horizontal and vertical), pentagon, or hexagon, and the published results show that the UWB antennas maintain a wide bandwidth (3.08  GHz–12.69  GHz) with an average gain of nearly 2.58 dBi. Considering guide wavelength (λg in GHz), the dimensions of the radiating patch are calculated by λg = c/fc√εreff, where c is the velocity of light in free space (3 × 108 m/s), fc is the center frequency (i.e., 6.85 GHz), and εreff is the effective relative permittivity [2]. Planar octagonal-shaped patch is modified by etching minimal distribution area of current so that RCS (RADAR cross-section) is reduced up to 25 dBsm, making it capable for stealth platform RADAR application [3]. Fork-shaped radiating patch with rectangular ground plane provides dual-band operations covering 2.40 GHz–2.484 GHz (Bluetooth) and 3.10 GHz–10.6 GHz (UWB) frequency bands [4]. Vase-shaped radiating patch provides fractional bandwidth of 136% (3.0 GHz–15.6 GHz) [5]. Integration of the telecommunication system within the garment and wearable merchandise is fabricated, known as textile antenna [6]. Antenna with a dimension of 40 × 38 mm2 consisting of a regular dodecagon on each side measuring 5.17 mm [7] is used to reveal breast tumor in the vicinity of UWB range, and care has also been taken by confining the specific absorption rate (SAR) within admissible range surrounding tissues and the skin. By joining two

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distinct semi-ellipses through their major axes and triangular-shaped groove at the ground plane [8], Bluetooth and UWB antenna fabricated and exhibit good omnidirectional pattern in H-plane and dipole-like pattern in E-plane at 2.45  GHz and 3.10 GHz. At higher frequencies, it is also observed that the cross-polarization in both E- and H-planes increases due to an increase in the area of radiation. Embedding an elliptical patch with a trapezoid, wide-slot UWB antenna with a compact dimension of 30  ×  30  mm2 is designed. Furthermore, the microstrip line is tapered for impedance matching, and the hexagonal slot is etched from a finite ground plane placed on another side of the substrate, resulting in fractional impedance bandwidth of 145% (2.90 GHz–18.00 GHz), and thus wide-slot antenna for UWB application is obtained [9]. Dipole-like radiation pattern in E-plane and the omnidirectional pattern are obtained in H-plane with a dome-topped bowl-shaped radiating patch measured at 3.40  GHz and 8.00  GHz [10]. An M-shaped radiating patch replacing

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conventional monopole antenna with modified cutting rectangular slots in the ground plane and beak-shaped radiating patch with two rectangular slots on the radiator along with hexagonal-shape defected ground structure (DGS) are designed [11, 12] for UWB application. Another MIMO ultra-wideband antenna with dual monopoles is located side to side at a spacing of 4.0 mm, with a subsequent radiator placed at 90° with a distance of 1.0 mm to prevent mutual coupling. Polarization diversity performance was calculated by envelope correlation coefficient (ECC) resulting below −20 dB [13]. Universal methodologies for designing a UWB diversity antenna by using asymmetrical monopole feed minimize mutual decoupling between dual radiators by adjusting their distance between radiators and feeding lines [14]. Bandwidth improvement is achieved by DGS (defected ground structure), including 11 step slots along with elliptical radiator forming monopole antenna for diversified applications as autonomous robot communication for disaster recovery, info-station systems communications, e-ward round, and imaging communications in UWB range [16]. The Federal Communications Commission-­ measured impedance bandwidth should be less than -10 dB. Therefore, it is observed that the values of impedance bandwidth (S11) are 10.35 GHz, 10.02 GHz, and 8.90 GHz, respectively. The reduction in RCS (RADAR cross-section) for the very sensitive target is very important in stealth (invisible) as well as military applications. Therefore, the antennas play a very important role as they are the source of electromagnetic radiation and are majorly dominant scatters. The design of lower RCS antennas encounters two major problems: one the reduced RCS for the complete useable band of the antenna and the other preserving the bandwidth of interest. As observed in [3], the UWB-designed antenna has a lower RCS with a value of 25 dBsm. Figure (x) shows the simulated impedance bandwidth of the antenna with values ranging from 2.684  GHz to 12.182  GHz, which is useful for UWB applications.

2.2  Microstrip/CPW Feed Figure 2 shows UWB antennas with microstrip/CPW feed-extended bandwidth including electromagnetic coupling [17–19]. The different parasitic elements are used in the conductor-backed plane for excitation of higher resonance frequencies, and the impedance bandwidth of the antenna is increased by introducing two inverted U-shaped slots in the ground plane. But these results only increase

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bandwidth on the higher side, and there is a deficiency of radiation on the lower side, and to overcome this problem, a pair of L-shaped elements are added, which acts as a resonator leading to the coupling of current from the ground structure to the parasitic element. This modification leads to the improvement of bandwidth, and two new resonance frequencies at 11.00 GHz and 14.10 GHz are excited [17]. A quadrangle UWB antenna is designed with a flipped T-shaped slot in the patch and a flipped T-shaped conductor in the ground plane near the ground conductor, which leads to a wider usable fractional bandwidth of more than 130% [18]. CPW-fed [20, 21] fractal UWB antennas are presented in [22–24]. Adding small fractal elements to the polygon shape radiator results in bandwidth enhancement [22]. CPW-fed antenna with nano-arm fractal results in the wideband (2.55GHz–11.84 GHz) [24]. L-type slots and the parasitic elements in a square patch fed by microstrip line and consisting of the modified ground are capable of covering bandwidth from 2.950  GHz to 14.270  GHz with 130% bandwidth [25]. Additional resonances at lower and higher frequency at 2.9 GHz and 10.7 GHz are achieved by horizontal H-shaped slots in the ground. Further, to extend the bandwidth, a vertically placed H-shaped element is etched, which resonates at 14.7 GHz and 17.0 GHz, respectively, thereby increasing the overall impedance bandwidth [26]. As observed in [25], electromagnetic coupling with an inverted T-shaped slot provides larger bandwidth of 2.91 GHz–14.1 GHz. CPW monopole antenna with small fractal elements covers 3.0 GHz–12.0 GHz bandwidth, which is shown in [22]. H-shaped etching in the ground plane provides useable fractional bandwidth of 150% (2.5 GHz–17.5 GHz) as observed from [26]. The bandwidth beyond covering X-, Ku-, and K-band applications is useful for applications in satellite and RADAR [27–33].

3  Single Notched Band Characteristics of UWB Antennas Figure 3a–i shows ultra-wideband monopole antennas with single notched band function, which are obtained by including filters with L-shaped slot, rectangular slot, and exciting resonance frequency by electromagnetic coupling theory or by the introduction of T-shaped stub either to eliminate WiMAX band or WLAN band [34–41]. Rogers RT/duroid 5870 and Rogers RT/duroid 5880 substrate with low relative permittivity of 2.33 support features such as wideband characteristics and stable radiation pattern concerning frequency. Annular ring UWB antenna with the partial annular slot is embedded at the lower portion of the ring radiator, which leads to high impedance at notch frequency of 5.5  GHz, removing wireless local area network (WLAN) and dedicated short-range communication (DSRC) interference [34]. The S-parameter signifies the matching of impedance. The better the S-parameter, the better the matched impedance, which also indicates that the maximum power is absorbed by the load. Application of particle swarm optimization method (PSOM) for the utmost mode coupling and better operating frequency for a comparatively smaller tapered length and a circular band-notched radiating patch with raised cosine-tapered is designed

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for ultra-wideband applications [35]. A T-type stub within the T-type slot in the radiation patch provides strong notched-band rejection with VSWR=26 and is also tuned over a wide tunable frequency ranging from 3.56  GHz to 6.81  GHz [37]. Electromagnetic coupling theory either between radiation patch and parasitic element or between the ground plane and parasitic element results in single notched-­ band function as represented in [39]. Folded T-type element (FTSE) is capable of controlling the filtering characteristics, where the tuning of the FTSE plays a major role. Further, the impedance bandwidth of the designed antenna is increased at a higher-frequency band side by introducing a pair of rectangular notched filters [41]. Figure 3j–k shows return loss curves for two versions of single notched-band UWB antennas. Figure 3j shows the elimination of the WiMAX interfering band, while Figure 3k shows the removal of the WLAN interfering band. This concludes that the UWB antennas in Fig. 3 have the capability of mitigating interfering bands.

4  Dual Notched-Band Characteristics of UWB Antennas Figure 4a–y represents UWB antenna with dual notched-band function [41–71]. WiMAX (3.30 GHz–3.80 GHz) and WLAN (5.150 GHz–5.825 GHz) occupy the UWB bandwidth, and hence they interfere. However, they are eliminated by using band stop filters in designing microstrip patch antennas. To achieve dual notched-­ bands, a rectangular slot of either C-shaped or U-shaped is removed on the radiation patch or the 50 Ω microstrip feedline. Moreover, two notched-band functions are also obtained by SRR (split-ring resonator) or CSRR (complementary split-ring

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resonator). The abovesaid techniques are represented by [42–48], which are discussed below. E-ring-shaped printed monopole antenna is used for UWB applications with a dual notched-band performance. A trapezoid-shaped radiating patch with a rectangular ground plane forms UWB antenna with U-T-type stubs inserted into two trapezoid-geometry slots of the radiating plane [43]. UWB antenna with two notched-functions are obtained by C-L-type etched slot/extrude stub in the radiation/ground plane [44]. A hexagon radiating patch with a circular slotted ground plane with two notched-band functions is represented. The addition of a pair of bent

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L-type structures to the symmetric slot ground results in two notched-band functions: one is WiMAX (3.30 GHz–3.70 GHz) and the other is WLAN (5.150 GHz–5.825 GHz) [49]. By using upper and lower SIR on the radiation patch of a CPW-fed UWB antenna, dual notched-band characteristics are obtained [52]. A wide frequency range (2.85 GHZ–15.4 GHz) of CPW-fed UWB antenna with elliptical path and chamfered edges across the ground plane at 45 degrees are presented in [51]. Impedance bandwidth of antenna with radiating patch and ground plane having the shape of a rectangle covers UWB frequencies from 3.10  GHz to 10.2 GHz. The bandwidth of the antenna is increased by etching a pair of rectangular ring-type slit in the ground plane, and the new bandwidth covers 2.80 GHz–17.5  GHz. To convert the abovesaid enhanced bandwidth antenna to two notched functions, a set of inverted T-type and inverted Ω-type slots are removed from the radiating patch and ground plane, respectively [53]. The antenna with a square radiating patch along with a V-type embedded strip over a rectangular ground plane covers enhanced bandwidth from 2.88  GHz to 17.85  GHz. Moreover, two notched-band antennas result by etching out a pair of L-type and E-type slots on the radiating patch [54]. Additional resonance is exhibited when an inverted fork-type slit is introduced in the ground, which in turn produces wider bandwidth. Radiating patch is embedded with a notched filter where coupled U-type is attached to it [54]. Ultra-wideband antenna with four equal-sided radiating patches beside hook-type slot along with customized ground plane with an inverted anchor-type slot and two Γ-type added strips inside the rectangular slot in the ground-plane leads to dual notched-band function with wider fractional impedance bandwidth of 130.20% [56]. The dual band-notched characteristics of UWB antennas are presented with electromagnetic coupling theory (ECT) [58–66]. Wider fractional bandwidth of an additional 125% is the result of the insertion of rotated T-type ring slot on rectangular radiation patch, which, in turn, covers C-type slot. To achieve the intended two notched-band functional antennas, a rotated T-type slot is covered by a C-type slot on the radiation patch, and by embedding rotated T-type ECT structure within the rotated T-type slot on the radiation patch, two notched-band functional antennas with wider bandwidth are resulted [58]. Additional enhanced bandwidth is obtained by etching out dual notch from the lower corner of the radiation patch, which is the result of ECT between the radiation patch and the ground plane. Embedding two T-U-type stubs on the radiating patch and near the microstrip feed, respectively, two notched-bands centered at 3.60 GHz and 5.50 GHz, respectively, are obtained [60]. Two notched-functions with ECT to increase impedance bandwidth of the antenna are shown in [61]. A slotted rectangular radiating patch with two rotated L-type slots and rotated T-type stubs results in a dual notched-band function. UWB antenna which consists of a modified T-shaped slot and a ground plane with two E-shaped slots including W-shaped conductor backed plane results in dual notched-band function [62]. Stepped-shaped patch and dual-rectangular slots over the ground plane for wider impedance bandwidth of 155% are shown in [63]. Dual notched-­ band characteristics are also obtained by eliminating the U-type slot on the radiating patch and butterfly-shaped conducting-element backed plane for ECT.  Fractalshaped dual notch UWB antennas are reported [67]. The multiple resonance

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characteristics with Koch fractal geometry and rectangular ground plane from ultrawideband antenna and dual notched-band function are obtained by embedding a pair of C-type slots on the radiation patch. Figure 4z shows the removal of the dual interfering band, namely, WiMAX and WLAN, which are due to the introduction of band stop filters. These filters can be in the form of the embedded stub, etched slot, electromagnetic coupling backed plane, or even electromagnetic bandgap structure.

5  T  riple/Quadra/Quintuple Notched-Band Characteristics of UWB Antennas Three, four, and five notched-filter UWB antennas are shown in Fig. 5a–n. Figure 5o shows the return loss of the triple notched-band UWB antenna. Triple notched-band function is obtained by removing dual circular-shaped slots corresponding to one-­ half the wavelength on the radiation patch for 3.30 GHz–3.70 GHz/5.150 GHz–5.85 GHz bands and downlink satellite communication band (7.10  GHz–7.90  GHz); two C-type slots in the ground plane are etched [72, 73]. By removing dual circular slots on the radiating patch and a couple of C-type slots over the ground plane, three notched-band functions are resulted [74, 75]. Triple notched-band characteristics are also obtained by three pairs of split-ring resonators along with the 50 Ω microstrip feedline [76, 77]. UWB antenna comprises a rectangle plane as a radiating patch with a set of two steps on the feed edge, a rotated stair-shaped ground plane, and a CPW feedline. The staircase structure increases the impedance bandwidth. By introducing a C-type slot on the main radiating patch, complementary split-ring resonator (CSRR) at the ground plane and rotated U-type slot at the middle of the radiating patch result in fineband rejection of WiMAX/WLAN/X-band satellite bands [78–84]. Three circular slots on the radiation patch with etched pair of C-type slots over the ground plane result in four notches intended for the WiMAX band (3.3 GHz–3.7 GHz), lower WLAN band (5.150 GHz–5.350 GHz), higher WLAN band (5.725 GHz–5.875 GHz), and X-band downlink satellite communication band (7.10 GHz–7.76 GHz) [85]. Notched-band filters are achieved with three C-type slots etched on the circular radiating patch and dual C-type slots etched on the opposite plane in the partial ground [86]. Also, UWB antenna with four, five notched bands are reported [87, 88] while the operating bandwidth is preserved. Multiband antenna [89, 90] is designed for applications which includes Bluetooth, LTE offering reconfigurable characteristics.

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6  Conclusions This chapter has focused on different UWB antennas with mitigation of interference. UWB antennas discussed are useful in wideband wireless applications in RADARs, different imaging systems, and also wireless sensor networks. All the potential interferences such as WiMAX (wireless interoperability for microwave access), WLAN (wireless local area network), and DSS (downlink satellite system) are mitigated where band stop filters are used in the form of stub, slots, ECT method, and metamaterial, using EBG structures. Here few UWB antennas have been reported in terms of their latest developments for applications in UWB, testing of electromagnetic radiation, and different imaging applications. The final selection of UWB antennas will always be a trade-off between different requirements.

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References 1. First Report and Order: Revision of Part 15 of the commission’s rules regarding ultra-­wideband transmission systems, Federal Communications Commission, FCC 02-48 (2002) 2. Sun, Y.Y., Cheung, S.W., Yik, T.I.: Planar monopole ultra-wideband antennas with different radiator shapes for body-centric wireless networks. In: Progress in Electromagnetics Research Symposium Proceedings Malaysia, pp. 839–843 (2012) 3. Dikmen, C.M., Simen, S., Cakir, G.: Planar octagonal-shaped UWB antenna with reduced radar cross section. IEEE Trans. Antennas Propag. 62, 2946–2953 (2014) 4. Mishra, S.K., Gupta, R.K., Vaidya, A., Mukherjee, J.: A compact dual-band fork-shaped monopole antenna for Bluetooth and UWB applications. IEEE Antennas Wirel. Propag. Lett. 10, 627–630 (2011) 5. Kumar, R., Awasthi, Y.K., Singh, H., Sharma, M., Kumari, S.: Vase shape UWB antenna. Adv. Sci. Lett. 22, 3714–3718 (2016) 6. Shakhirul, M.S., Juosh, M., Sahadah, A., Nor, C.M., Rahim, H.A.: Embroidered wearable textile antenna on bending and wet performances for UWB application. Microw. Opt. Technol. Lett. 56(9), 2158–2163 (2014) 7. Kahar, M., Ray, A., Sarkar, D., Sarkar, P.P.: An UWB microstrip monopole antenna for breast tumor detection. Microw. Opt. Technol. Lett. 57, 49–54 (2015) 8. Silveria, G.N.M., Yoshioka, R.T., Bertuzzo, J.E., Figueroa, H.E.H.: Printed monopole antenna with triangular-shape groove at ground plane for Bluetooth and UWB applications. Microw. Opt. Technol. Lett. 57, 28–31 (2015) 9. Ghaderi, M.R., Mohajeri, F.: A compact hexagonal wide-slot antenna with microstrip-fed monopole for UWB application. IEEE Antennas Wirel. Propag. Lett. 10, 682–685 (2011) 10. Koohestani, M., Moghadasi, M.N., Virdee, B.S.: Miniature microstrip-fed ultra wideband printed monopole antenna with a partial ground plane structure. IET Microw. Antennas Propag. 5, 1683–1689 (2011) 11. Shrivastava, M.K., Gautam, A.K., Kanaujia, B.K.: An M-shaped monopole like slot UWB antenna. Microw. Opt. Technol. Lett. 56, 127–131 (2014) 12. Chandel, R., Gautam, A.K., Kanaujia, B.K.: Microstrip-line fed beak-shaped monopole-like slot UWB antenna with enhanced bandwidth. Microw. Opt. Technol. Lett. 56, 2624–2628 (2014) 13. Khan, M.S., Capobianco, A.D., Naqvi, A., Ijaz, B., Asif, S., Braaten, B.D.: Planar, compact ultra wideband polarization diversity antenna array. IET Microw. Antennas Propag. 9, 1761–1768 (2015) 14. Zhao, H., Zhang, F., Wang, C., Zhang, X.: A universal methodology for designing a UWB diversity antenna. J. Electromagn. Waves Appl. 28, 1221–1235 (2014) 15. Mao, X., Chu, Q.X.: Miniaturization of UWB antenna by asymmetrically extending stub from ground. J. Electromagn. Waves Appl. 28, 531–541 (2014) 16. Hanapi, K.M., Rahim, S.K.A., Saad, B.M., Rani, M.S.A., Aziz, M.Z.A.: An elliptically planar UWB monopole antenna with step slots defective ground structure. Microw. Opt. Technol. Lett. 56, 2084–2088 (2014) 17. Zafarlou, R., Ghobadi, C., Nourinia, J.: Design, simulation, and fabrication of an ultra wideband monopole antenna for use in circular cylindrical microwave imaging systems. Aust. J. Basic Appl. Sci. 7, 674–680 (2013) 18. Ojaroudi, M., Yazdanifard, S., Ojaroudi, N., Moghaddasi, M.N.: Small square monopole antenna with enhanced bandwidth by using inverted T-shaped slot and conductor-backed plane. IEEE Trans. Antennas Propag. 59, 670–674 (2011) 19. Reddy, G.S., Mishra, S.K., Kharche, S., Mukherjee, J.: High gain and low cross-polar compact printed elliptical monopole UWB antenna loaded with partial ground and parasitic patched. Prog. Electromagn. Res. B. 43, 151–167 (2012) 20. Gautam, A.K., Yadav, S., Kanaujia, B.K.: A CPW-fed compact UWB microstrip antenna. IEEE Antennas Wirel. Propag. Lett. 12, 151–154 (2013)

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21. Mobashsher, A.T., Islam, M.T.: Design, investigation and measurement of a compact ultra wide band antenna for portable applications. Meas. Sci. Rev. 13, 169–176 (2013) 22. Fallahi, H., Atlasbaf, Z.: Bandwidth enhancement of a CPW-fed monopole antenna with small elements. Int. J. Electron. Commun. 69, 590–595 (2015) 23. Kumar, R., Magar, D., Sawant, K.K.: On the design of inscribed triangle circular fractal antenna for UWB applications. Int. J. Electron. Commun. 66, 68–75 (2012) 24. Kumar, R., Gaikwad, S.: On the design of Nano-arm fractal antenna for UWB wireless applications. J. Microw. Optoelectron. Electromagn. Appl. 12, 158–171 (2013) 25. Ojaroudi, N., Ojaroudi, M., Ebazadeh, Y.: UWB/Omni-directional microstrip monopole antenna for microwave imaging applications. Prog. Electromagn. Res. C. 47, 139–146 (2013) 26. Ojaroudi, N., Ojaroudi, Y., Ojaroudi, S.: Omnidirectional monopole antenna for use in circular cylindrical microwave imaging systems. Wirel. Pers. Commun. 80, 1035–1046 (2015) 27. Gorai, A., Karmakar, A., Pal, M., Ghatak, R.: A super wideband chebyshev tapered antipodal vivaldi antenna. Int. J. Electron. Commun. 69, 1328–1333 (2015) 28. Krishna, R.V.S.R., Kumar, R.: Design of a square ring shape slot antenna for UWB polarization-­ diversity applications. Int. J. Electron. Commun. 69, 1305–1313 (2013) 29. Fakharian, M.M., Rezaei, P.: Very compact palmate leaf-shaped CPW-fed monopole antenna for UWB applications. Microw. Opt. Technol. Lett. 56, 1612–1616 (2014) 30. Jahangiri, P., Sadeghzadeh, R.A., Pourzaid, A.: Log spiral antenna with CPW feed line for UWB application and circular polarization. Microw. Opt. Technol. Lett. 58, 17–21 (2016) 31. Bekasiewicz, A., Koziel, S.: Structure and computationally efficient simulation driven design of compact UWB monopole antenna. IEEE Antennas Wirel. Propag. Lett. 14, 1282–1285 (2015) 32. Siddiqui, J.W., Saha, C., Antar, Y.M.M.: Compact dual SRR loaded UWB monopole antenna with dual frequency and wideband notch characteristics. IEEE Antennas Wirel. Propag. Lett. 14, 100–103 (2014) 33. Liu, Y.F., Wang, P., Qin, H.: Compact ACS-fed UWB monopole antenna with extra Bluetooth band. Electron. Lett. 50, 1263–1264 (2014) 34. Azim, R., Islam, M.T.: Compact planar UWB antenna with band notch characteristics for WLAN and DSRC. Prog. Electromagn. Res. 133, 391–406 (2013) 35. Malik, J., Kartikeyan, M.V.: Band notched UWB antenna with raised cosine-tapered ground plane. Microw. Opt. Technol. Lett. 56, 2576–2579 (2014) 36. Satyanarayana, B., Mulgi, S.: Design of planar band-notched monopole antenna for 2.4GHz WLAN and UWB applications. Microw. Opt. Technol. Lett. 57, 2496–2501 (2015) 37. Abbas, S.M., Ranga, Y., Verma, A.K., Esselle, P.: A simple ultra wideband printed monopole antenna with high band rejection and wide radiation patterns. IEEE Trans. Antennas Propag. 62, 4816–4820 (2014) 38. Tasouji, N., Nourinia, J., Ghobadi, C., Tofigh, F.: A novel printed UWB slot antenna with reconfigurable band-notch characteristics. IEEE Antennas Wirel. Propag. Lett. 12, 922–925 (2013) 39. Azim, R., Mobashsher, A.T., Islam, M.T.: UWB antenna with notched band at 5.5  GHz. Electron. Lett. 49, 922–924 (2013) 40. Subbarao, A., Raghavan, S.: Coplanar waveguide-fed ultra-wideband planar antenna with WLAN-band rejection. J. Microw. Optoelectron. Electromagn. Appl. 12, 50–59 (2013) 41. Moghadasai, M.N., Sadeghzadeh, R.A., Sedghi, T., Aribi, T., Birdee, B.S.: UWB CPW-fed fractal patch antenna with band-notched function employing folded T-shaped element. IEEE Trans. Antennas Propag. 12, 504–507 (2013) 42. Zhou, D., Gao, S., Zhu, F., Abd-Alhameed, R.A., Xu, D.: A simple and compact planar ultra wide band antenna with single or dual band-notched characteristics. Prog. Electromagn. Res. 123, 47–65 (2012) 43. Wang, J., Yin, Y., Liu, X., Wang, T.: Trapezoid UWB antenna with dual band-notched characteristics for WiMAX/WLAN bands. Electron. Lett. 49, 685–686 (2013) 44. Gao, P., Xiong, L., Dai, J., He, S., Zheng, Y.: Compact printed wide-slot UWB antenna with 3.5/5.5  GHz dual band-notched characteristics. IEEE Antennas Wirel. Propag. Lett. 12, 983–986 (2013)

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45. Kazim, J., Bibi, A., Rauf, M., Tariq, M., Owais: A compact planar dual band-notched monopole antenna for UWB application. Microw. Opt. Technol. Lett. 56, 1095–1097 (2014) 46. Singh, R., Pandey, G.K., Agarwal, M., Singh, H.S., Bharti, P.K., Meshram, M.K.: Compact planar monopole antenna with dual band-notched characteristics using T-shaped stub and rectangular mushroom type Electromagnetic band gap structure for UWB and Bluetooth applications. Wirel. Pers. Commun. 78, 215–230 (2014) 47. Kumar, R., Naidu, V.P., Kamble, V., Krishna, R.V.S.R.: Simulation, design of compact multi-­ band microstrip slot antennas for WiMAX/WLAN and UWB applications. Wirel. Pers. Commun. 80, 1175–1192 (2015) 48. Fakharian, M.F., Rezaei, P., Aadi, A.: A planar UWB bat-shaped monopole antenna with dual band-notched for WiMAX/WLAN/DSRC. Wirel. Pers. Commun. 81, 881–891 (2015) 49. Liu, X., Yin, Y., Liu, P., Wang, J., Xu, B.: A CPW-fed dual band-notched UWB antenna with a pair of bended dual-L-shape parasitic branches. Prog. Electromagn. Res. 136, 623–634 (2013) 50. Yadav, A., Sethi, D., Khanna, R.K.: Slot loaded UWB antenna: dual band notched characteristics. Int. J. Electron. Commun. (AEÜ). 70, 331–335 (2016) 51. Sefidi, M., Zehforoosh, Y., Moradi, S.: A novel CPW-fed antenna with dual band-notched characteristics for UWB applications. Microw. Opt. Technol. Lett. 57, 2391–2394 (2015) 52. Sefidi, M., Zehforoosh, Y., Moradi, S.: A small CPW-fed UWB antenna with dual band-­ notched characteristics using two stepped impedance resonators. Microw. Opt. Technol. Lett. 58, 464–467 (2016) 53. Ojaroudi, N., Ojaroudi, M.: Dual band-notched monopole antenna with multi-resonance characteristic for UWB wireless communications. Prog. Electromagn. Res. C. 40, 187–199 (2013) 54. Mehranpour, M., Nourinia, J., Ghobadi, C., Ojaroudi, M.: Dual band-notched square monopole antenna for ultra wideband applications. IEEE Trans. Antennas Propag. 11, 172–175 (2012) 55. Ojaroudi, M., Ojaroudi, N., Ghadimi, N.: Dual band-notched small monopole antenna with novel coupled inverted U-ring strip and novel fork-shaped slit for UWB applications. IEEE Antennas Wirel. Propag. Lett. 12, 182–185 (2013) 56. Ojaroudi, N., Ghadimi, N., Ojaroudi, Y.: Compact multi-resonance monopole antenna with dual band-stop property for UWB wireless communications. Wirel. Pers. Commun. 81, 563–579 (2015) 57. Ojaroudi, N., Ghadimi, N.: Ultra-wideband slot antenna with rejection of WLAN and ITU bands using protruded strip resonators. Wirel. Pers. Commun. 79, 929–939 (2014) 58. Ojaroudi, N., Ojaroudi, M.: Novel design of dual band-notched monopole antenna with bandwidth enhancement for UWB applications. IEEE Antennas Wirel. Propag. Lett. 12, 698–701 (2013) 59. Rahimi, M., Sadeghzadeh, R.A., Zarrabi, F.B., Mansouri, Z.: Band-notched UWB monopole antenna design with novel feed for taper rectangular radiating patch. Prog. Electromagn. Res. C. 47, 147–155 (2014) 60. Jiang, W., Che, W.: A novel UWB antenna with dual notched bands for WiMAX and WLAN applications. IEEE Antennas Wirel. Propag. Lett. 11, 293–296 (2012) 61. Moosadadeh, M., Abbosh, A.M., Esmati, Z.: Design of compact planar ultra wideband antenna with dual-notched bands using slotted square patch and pi-shaped conductor-backed plane. IET Microw. Antennas Propag. 6, 290–294 (2012) 62. Ojaroudi, N., Ojaroudi, M., Ghadimi, N.: Dual band-notched small monopole antenna with novel W-shaped conductor backed-plane and novel T-shaped slot for UWB applications. IET Microw. Antennas Propag. 7, 8–14 (2013) 63. Beigi, P., Nourinia, J., Mohammadi, B., Valizade, A.V.: Bandwidth enhancement of small square monopole antenna with dual band notch characteristics using U-shaped slot and butterfly shape parasitic element on backplane for UWB applications. ACES J. 30, 78–85 (2015) 64. Khalizadeh, A., Tan, A.E.C., Rambabu, K.: Design of an integrated UWB antenna with dual band notch characteristics. Int. J. Electron. Commun. (AEÜ). 67, 433–437 (2013) 65. Ojaroudi, N., Ojaroudi, M.: Dual band-notched small monopole antenna with enhanced bandwidth for UWB applications. Wirel. Pers. Commun. (Springer). 75, 569–578 (2014)

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66. Ojaroudi, Y., Ojaroudi, S., Ojaroudi, N.: A novel 5.5/7.5GHz band-stop antenna with modified ground plane for UWB communications. Wirel. Pers. Commun. (Springer). 81, 319–332 (2015) 67. Sharma, M., Awasthi, Y.K., Singh, H.: Planar high rejection dual band-notch UWB antenna with X & Ku-bands wireless applications. Int. J. Microw. Wirel. Technol. 9, 1725–1733 (2017) 68. Mishra, S.K., Mukherjee, J.: Compact printed dual band-notched U-shape UWB antenna. Prog. Electromagn. Res. C. 27, 169–181 (2012) 69. Pandey, G.K., Singh, H.S., Bharti, P.K., Meshram, M.K.: Design and analysis of Ψ-shaped UWB antenna with dual band notch characteristics. Wirel. Pers. Commun. 89, 1–14 (2016) 70. Sharma, M., Awasthi, Y.K., Singh, H.: Compact planar UWB monopole antenna with dual band-notch characteristics. Int. J. Ultra Wideband Commun. Syst. 3, 133–142 (2016) 71. Sharma, M., Awasthi, Y.K., Singh, H., Kumar, R., Kumari, S.: Design of compact flower shape dual notched-band monopole antenna for extended UWB wireless applications. J.  RF Eng. Telecommun. (Frequenz). 70, 499–506 (2016) 72. Bakariya, P.S., Dwari, S., Sarkar, M.: Triple band notch UWB printed monopole antenna with enhanced bandwidth. Int. J. Electron. Commun. 69, 26–30 (2015) 73. Zarrabi, F.B., Mansouri, Z., Gandji, N.P., Kuhestani, H.: Triple-notch UWB monopole antenna with fractal koch and T-shaped stub. Int. J. Electron. Commun. 70, 64–69 (2016) 74. Bakariya, P.S., Dwari, S., Sarkar, M.: A triple band notch compact UWB printed monopole antenna. Wirel. Pers. Commun. 82, 1095–1106 (2015) 75. Venkata, S.K., Rana, M., Bakariya, P.S., Dwari, S., Sarkar, M.: Planar ultra wideband monopole antenna with Tri-Notch characteristics. Prog. Electromagn. Res. C. 46, 163–170 (2014) 76. Zhang, Y., Hong, W., Yu, C., Kuai, Z.Q., Don, Y.D., Zhou, J.Y.: Planar ultra wideband antennas with multiple notched bands based on etched slots on the patch and/or split ring resonators on the feed line. IEEE Trans. Antennas Propag. 56, 3063–3068 (2008) 77. Das, S., Mitra, D., Chaudhuri, S.R.B.: Design of UWB planar monopole antennas with etched spiral slot on the patch for multiple band-notched characteristics. Int. J. Microw. Sci. Technol. 2015, 1–9 (2015) 78. Haroon, S., Alimgeer, K.S., Khalid, N., Malik, B.T., Shafique, M.F., Khan, S.A.: A low profile UWB antenna with triple band suppression characteristics. Wirel. Pers. Commun. 82, 498–507 (2015) 79. Sarkar, M., Dwari, S., Daniel, A.: Printed monopole antenna for ultra-wideband application with tunable triple-band-notched characteristics. Wirel. Pers. Commun. 84, 2943–2954 (2015) 80. Srivastava, G., Dwari, S., Khanujia, B.K.: A compact triple band notch circular ring antenna for UWB applications. Microw. Opt. Technol. Lett. 57, 668–672 (2015) 81. Pandey, G.K., Singh, H.S., Bharti, P.K., Meshram, M.K.: Design and analysis of mul tiband notched pitcher-shaped UWB antenna. Int. J.  RF Microw. Comput. Aided Eng. 25, 795–805 (2016) 82. Sharma, M., Awasthi, Y.K., Singh, H., Kumar, R., Kumari, S.: Compact printed high rejection triple band-notch UWB antenna with multiple wireless applications. Eng. Sci. Technol. Int. J. 19, 1626–1634 (2016) 83. Srivastava, K., Kumar, A., Verma, A.K., Zhang, Q., Kanaujia, B.K., Dwari, S.: Integrated GSM And UWB fractal monopole antenna with triple notches. Microw. Opt. Technol. Lett. 58, 2364–2366 (2016) 84. Sharma, M., Awasthi, Y.K., Singh, H.: Design of CPW-fed high rejection triple band-notch UWB antenna on silicon with diverse wireless applications. Prog. Electromagn. Res. C. 74, 19–30 (2017) 85. Bakariya, P.S., Dwari, S., Sarkar, M.: Printed ultra wideband monopole antenna with four notch band. Wirel. Pers. Commun. 84, 2989–2999 (2015) 86. Islam, M., Islam, M.T., Samsuzzaman, M., Faruque, M.R.I.: Five band-notched ultra wideband (UWB) antenna loaded with C-shaped slots. Microw. Opt. Technol. Lett. 57, 1470–1475 (2015) 87. Sharma, M.M., Deegwal, J.K., Kumar, A., Govil, M.C.: Compact planar monopole UWB antenna with quadruple band-notched characteristics. Prog. Electromagn. Res. C. 47, 29–36 (2014)

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88. Zhang, J., Cao, P., Huang, Y., Alrawashdeh, R., Zhu, X.: Compact planar ultra-wideband antenna with quintuple band-notched characteristics. IET Microw. Antennas Propag. 9, 206–216 (2015) 89. Srivastava, G., Mohan, A.: Compact dual-polarized UWB diversity antenna. Microw. Opt. Technol. Lett. 57, 2951–2955 (2015) 90. Sharma, M., Awasthi, Y.K., Singh, H.: Compact multiband planar monopole antenna for Bluetooth, LTE, and reconfigurable UWB applications including X-band and Ku-band wireless communications. Int. J. RF Microw. Comput. Aided Eng. 29, 1–11 (2019)

Part III

Multiple Input Multiple Output (MIMO) Antenna Design and Uses

Planar Design, Analysis, and Characterization of Multiple-Input Multiple-Output Antenna Manish Sharma

1  Introduction Microwave antennas play a major vital role in a modern wireless communication system. The requirement for speedy wireless communication has become an important mode to fulfill the needs, and thus, peer-to-peer wireless link between transmitter and receiver has to fulfill the necessity of wireless applications. The number of transmitting/receiving antennas plays a major role, and it is a proven fact that a single antenna transceiver suffers drawbacks like multiple path fading and inter-­ symbol interference which lowers the working capability. To improve the above factors, a multiple-input multiple-output (MIMO) antenna system provided the solution for an increase in channel capacity, thereby reducing the demerits of the single antenna system. This chapter focuses on the design aspects, analysis, and characterization of MIMO antennas fulfilling the application needs for ultra-wideband (UWB) and multiband antennas [1–49]. There are various techniques used to develop MIMO antennas which give solution to the designer, such as obtaining required near-, far-­ field, and diversity performance of the antenna system. While discussing wideband antennas (ultra-wideband/super-wideband), several geometries, as well as numerous isolation techniques, have been reported [1–17] to obtain MIMO antenna configuration. Geometries such as quarter circular patch [1, 8, 9], modified rectangular patch [2], circular patch [3, 6, 12], slotted rectangular patch [4], combination of ellipse and rectangular patch [5, 13, 14, 16, 17], modified elliptical patch [7, 15], semicircular slotted patch [10], hexagon patch [11], etc. are transformed to MIMO M. Sharma (*) Chitkara University Institute of Engineering and Technology, Chitkara University, Punjab, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 P. K. Malik et al. (eds.), Smart Antennas, EAI/Springer Innovations in Communication and Computing, https://doi.org/10.1007/978-3-030-76636-8_12

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configuration by placing two or more than two radiating elements in adjacent, orthogonal, or face-to-face orientations. The isolation between the radiating elements is another important factor to preserve the diversity performance and techniques such as etched slots, embedded stub, and fractal geometries. Further, super-wideband antennas are used to obtain operating bandwidth beyond ultra-­ wideband bandwidth, having a bandwidth ratio >10:1 [18, 19] to cover the remaining applications. Dual-polarization MIMO antennas are obtained by feeding a single patch with two ports placed orthogonally [21, 22], leading to either right-­ handed circular polarization or left-handed circular polarization. On the other hand, there are several MIMO multiband antennas reported either for 2 × 2 or 4 × 4, and even 8  ×  8 configurations are designed for several narrowband applications (WiMAX, WLAN, Bluetooth, X-band, etc.) [22–49].

2  2 × 2 UWB/Super-Wideband MIMO Antennas The Federal Communications Commission (FCC-2002), USA, introduced unlicensed bandwidth of 3.10 GHz–10.60 GHz. This bandwidth covers large numbers of wireless applications such as imaginary systems, through-wall imaging systems, and surveillance systems. The applications beyond UWB are achieved by super-­ wideband antennas with a bandwidth ratio >10:1, which is useful for applications in satellite as well as RADAR applications. Figure 1a–g represents few UWB 2 × 2 MIMO antenna configurations. Polarization diversity of the quadrant-shaped monopole is achieved by placing the patch orthogonally as shown in Fig. 1a. Integration of the MIMO antenna is achieved on FR4 substrate with dimensions 21 × 35 mm2. The antenna is placed in a different orientation, but the transmission coefficient for the entire operating bandwidth of UWB is achieved in orthogonal orientation. The stubs and slots used in the design provide an additional current path, thereby improving the lower and higher frequency resonances. Figure  1b shows a circularly

Fig. 1  UWB 2 × 2 MIMO antenna configuration (a–g)

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polarized MIMO antenna exhibiting pattern and polarization diversity. Reported MIMO antenna provides axial ratio bandwidth of 8.11 GHz–10.56 GHz (2.45 GHz) with the impedance bandwidth of 8.07 GHz–11.59 GHz (3.52 GHz). Five iterations are performed from basic rectangular patch to final design for X-band applications. Figure 1c depicts a circular patch 2 × 2 MIMO antenna with the rectangular ground plane. A pair of rectangular slots are etched for wideband impedance matching. However, without decoupling structure, the average isolation in the operating band is around −12 dB, and with the presence of the decoupling structure, excellent isolation of more than −30 dB is achieved. The decoupling structure is also used in the ground, providing better isolation when compared in the absence as observed in Fig. 1d. However, WLAN interfering band (5.150 GHz–5.825 GHz) is filtered by etching a rectangular slot on the radiating patches of 2 × 2 MIMO antenna configuration. Figure  1e–f shows 2  ×  2 MIMO antenna configuration with mitigating WiMAX and WLAN interfering bands. In both cases, the T-type parasitic stub acts as the decoupling structure, providing better isolation between the radiating elements. It is also desired. to eliminate interfering bands with bandwidth of 3.25  GHz–3.60  GHz, 5.05  GHz–5.48  GHz, 5.60  GHz–6.00  GHz, and 7.80  GHz–8.40  GHz. This is achieved in 2 × 2 MIMO antenna configuration shown by Fig. 1g, and etched L-type meandered slot, pair of L-shaped slots, and addition of C-type stub achieve the objective. Table 1 shows the detailed comparison of the notched-band 2 × 2 MIMO antenna with near-, far-field, and diversity performance comparison. Table 1 shows the comparison of the designed UWB/super-wideband monopole 2  ×  2 MIMO antennas. As per the observations from Table 1, the latest state-of-the-art designed MIMO antennas are considered for comparison, which includes the size of the antenna, operating bandwidth, techniques used for isolation, maximum gain, and the comparison of ECC parameter. It can be concluded from comparison in Table 1 that these MIMO antennas maintain gain variation between 3.00 dBi and 5.00 dBi with ECC ranging between 0.02 and 0.250. Also, isolation technique is applied between the radiating elements or the ground plane, and in [19], no isolation technique is used because the orthogonal orientation itself provides better isolation.

3  2 × 2 Dual-Polarization and Multiband MIMO Antennas Figure 2 shows a 2  ×  2 MIMO antenna configuration with dual-polarization and multiband applications. In single-polarization antennas, there is a dependency on the wave being polarized, which can be either horizontal, vertical, or inclined linear polarizations. However, to overcome the limitations and to receive both horizontal and vertical polarized waves, dual-polarization MIMO antennas are used, forming MIMO configuration with one radiating element and two input ports. Figure  2a shows a dual-polarized MIMO antenna, which consists of an octagonal defected ground structure and ring-shaped radiator. The MIMO antenna is suitable for

29.0 × 40.0

20.0 × 20.0 38.5 × 38.5 25.0 × 39.0 30.75 × 37.80 22.0 × 28.0

[7]

[9] [10] [12] [15] [16]

[19] 19.0 × 28.0

3.10–10.60

32.0 × 65.0

[5]

0.70–18.50

1.20–19.40 3.10–10.60 2.68–12.50 2.70–11.22 3.00–11.00

3.10–11.00

Operating bandwidth (GHz) 2.90–11.00 3.00–11.00

Size of antenna Ref. (mm2) [1] 21.0 × 35.0 [3] 47.0 × 93.0

2020

2019 2020 2020 2020 2018

2020

2020

Year of publication 2017 2018

None

Parasitic T-stub Parasitic T-stub Addition of two U-shaped branch Hilbert fractal slots in the ground Extruding T-type stub in the ground

Isolation technique used Two L-shaped slots on radiator Modified T-type stub between radiating elements and etched slit at the center of the common ground plane Meandered line electromagnetic bandgap structure Vertical stub in the ground

Table 1  Comparison of the work published (2 × 2 MIMO UWB/super-wideband) antennas