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Miniaturized Microwave Devices and Antennas for Wearable, Implantable and Wireless Applications

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Miniaturized Microwave Devices and Antennas for Wearable, Implantable and Wireless Applications Miniaturized Microwave Devices and Antennas for Wearable, Implantable and Wireless Applications Muhammad Ali Babar Abbasi Department of Electrical Engineering Frederick University, Nicosia, Cyprus A thesis submitted for the degree of arXiv:1806.00379v1 [physics.app-ph] 1 Jun 2018 PhD { Electrical Engineering 2017 Dedicated to my parents. Acknowledgements Praise be to Allah úÍAªK ð éKAjJ ., the Most Gracious, the Most Mer- ciful, for blessing me with the strength to complete this work. I pray that the growth I achieved would be used in his cause. I am infinitely grateful to my parents for passing down the values and constant en- couragement throughout my educational career. I thank the Frederick University for giving me the opportunity to pursue my doctoral stud- ies. I am also thankful to the Erasmus Mundus INTACT doctoral level scholarship program for funding my research. I am thankful to the School of Electrical Engineering and Computer Sciences, National University of Sciences and Technology (NUST), Islamabad, Pakistan in grooming my research aptitude. Specifically, I am grateful to Dr. Munir Ahmed Tarar for advising my thesis. I am thankful to COM- SATS Institute of Information and Technology, Islamabad, Pakistan for providing me strong undergraduate education and to Dr. Syed Muzahir Abbas for his guidance. I would like to extend my profound gratitude to my mentor and prin- cipal advisor Dr. Symeon Nikolaou for his constant guidance and encouragement that I received from him. He trusted in me, always held me to a high standard, and encouraged me to work hard. In addition to being my advisor, he is an amazing person and I have been thoroughly enriched working with him. It has been an honor for me to work under his supervision. I am also thankful to Dr. Marco A. Antoniades for his active participation in my research endeavors throughout my tenure at Frederick University. He always encouraged and supported me. He extended his help by allowing me to be a part of his research laboratory at the University of Cyprus (UCY). I would like to thank Dr. Photos Vrionides for his constant support and kind words. I would like to thank Professor Antonije R. Djordjevic and Dr. Marija M. Nikolic for their help and guidance while my scientific mis- sion in the University of Belgrade, Serbia. Also, thanks to Tim and Harish from Cambridge University for contributing in public CUED Latex material. I would like to thank my friends who made my stay in Cyprus the most memorable, always supported me and encouraged me, tolerated my sarcasm, and accepted me with my workaholic nature. Thanks to Waqar (the guide), Salman (the information), Naveed (doctor sab), Taqua (the kindness), Christina (the humbleness), Mostafa (the inspi- ration), Rafay (the discipline), (sweet) Abdul, Agn´e(the amazing), Yousaf (the curious), Haroon (the help), Zunaib (the calm), Aqeela (the taste) and Zainab (the fun). I could always count on the support and encouragement from Badar bhai, Haroon bhai and family, also from Saleem, Rizwan, Ilyas, Hamza, Sahar, Ambreen and Hassan, even remotely. I also enjoyed the company of Dr. Hassaan, Maria Api and kids, Sir Zeeshan, Sir Ajmal, Dr. Adnan, Dr. Umer, Ms. Rania, Birendra (late), Diogo, Daniela, Kinga, Andreas(s), Hanne, Constantinos, Ouan, Mohamed, Kata, Simran, George, Marilena(s), Angelena, Krisztina, Veronica, Dora, Chloe, Mainul Haque, James, Krish, Ahmed, Winnie, Talha, Parash, Melanie and Sergio. The time spent with my colleagues, working as a team, deep discussions, long walks, adventures, travelling within Cyrus and abroad, road trips, and most of all the sleepless nights working in the lab and time spent in \PhD House" will always be a valuable part of my memory. Abstract This thesis presents a number of microwave devices and antennas that maintain high operational efficiency and are compact in size at the same time. One goal of this thesis is to address several miniaturization challenges of antennas and microwave components by using the theo- retical principles of metamaterials, metasurfaces coupling resonators and stacked radiators, in combination with the elementary antenna and transmission line theory. While innovating novel solutions, stan- dards and specifications of next generation wireless and bio-medical applications were considered to ensure advancement in the respec- tive scientific fields. A compact reconfigurable phase-shifter based on negative-refractive-index transmission-line (NRI-TL) materialist unit cells is presented. The corresponding work focuses on implementa- tion of two inter-switchable NRI-TL metamaterial unit cells collocated within the same board area in a reconfigurable manner. In addition to phase shifter, a practical implementation of a miniaturized mi- crowave crossover using NRI-TL metamaterials is demonstrated. The metamaterial theory has signify that by loading a conventional trans- mission line with lumped LC elements, a large phase shift per-unit- length can be achieved. Using this feature of NRI-TL metamaterials, the miniaturization of a crossover has been achieved by replacing the conventional microstrip transmission lines in a three-section branch- line coupler crossover with NRI-TL metamaterials lines, representing a compact NRI-TL crossover with an area 47 times smaller than the area of the conventional counterpart. By moving from 1D metamateri- als to 2D metasurfaces, an array of Electromagnetic Band Gap (EBG) structures is introduce. The corresponding study discussed the use of an EBG array structure as a director for efficient radiation of a wear- able antenna. A planar monopole printed on a partially grounded substrate is first loaded with a M ×N EBG structure to achieve a maximum directivity along the z-axis when the antenna is placed in the x-y plane. A successful attempt of miniaturizing such structure to a 2×1 element array excited by a monopole to form an efficient antenna is presented. The reflection phase of a single EBG unit cell has been studied and exploited towards efficient radiation of planar monopole. The shape of the EBG unit cell and the gap between the ground and the EBG layer are adjusted so that the antenna operates at 2.45 GHz. The proposed antenna retained its impedance matching when placed directly upon a living human subject with an impedance bandwidth of 5%, while it exhibits a measured gain of 6.88 dBi. A novel equivalent array model is presented to qualitatively explain the radiation mechanism of the antenna. In the next study, a fork shaped wearable sensor antenna is designed by utilizing the available ground space of the EBG backed monopole. The antenna is designed to ef- ficiently radiate towards the human body while keeping the detuning and impedance mismatching affects to a minimum, which are reported to be inevitable due to body loading. For this study, a high resolu- tion numerical human body phantom was used and Finite Difference Time-domain (FDTD) solver was used as a simulation environment. Challenges and possible solutions for through-body communication has been investigated. Next, a fully parametrized solution for an im- plantable antenna is proposed using metallic coated stacked substrate layers. The intended solution makes it possible to use the proposed antenna structure as an implant at several different areas of the hu- man body with potentially distinct electrical properties with conse- quently different detuning effect. Particle swarm algorithm has been implemented to optimize the antenna performance while operating inside distinct human tissue surroundings. Within dead tissue (quasi in-vivo) operation of the implantable antenna, on-body operation of the wearable sensor antenna, and an efficient communication of EBG backed monopole with an off-body transceiver depicts a practical so- lution for body-centric wireless communication system. The entire study answered several research questions of applied electromagnetic in the field of bio-medicine. Next, miniaturization and implementa- tion of a UWB antenna along with an analytical model to predict the resonance is presented. Lastly, several miniaturized rectifiers de- signed specifically for efficient wireless power transfer are proposed, experimentally verified, and discussed. Contents Contents vii List of Figures xi Nomenclature xviii 1 Introduction 1 1.1 Motivation . .1 1.2 Objectives . .2 1.3 Organization of the Dissertation . .2 2 Metamaterial Based Electrically Small Microwave Devices 4 2.1 Introduction to Metamaterials . .5 2.1.1 Electromagnetic wave propagation in metamaterials . .6 2.1.2 Metamaterial Applications . .9 2.2 Reconfigurable NRI-TL Metamaterial Phase Shifter . 10 2.2.1 Design Process . 12 2.2.2 Optimization Algorithm . 15 2.2.3 Realization . 18 2.2.4 Results and Discussion . 21 vii CONTENTS 2.3 A Compact NRI-TL Metamaterial Microstrip Crossover . 23 2.3.1 Implementation . 24 2.3.2 Fabrication and Measurements . 27 2.4 Chapter Conclusions . 28 3 Metasurface Based Miniaturized Wearable Antenna 30 3.1 Introduction to Metasurfaces . 31 3.1.1 Possible application of Metamaterial and Metasurfaces . 32 3.2 2×1 EBG-backed Planar Monopole Antenna Design . 34 3.2.1 Antenna Configuration and EBG Structure Selection . 36 3.2.2 Antenna Miniaturization . 39 3.2.3 Parametric analysis . 41 3.2.4 Radiation performance and mechanism . 43 3.2.5 Experimental Results . 49 3.3 Analysis of Antenna for Wearable Applications . 50 3.3.1 Effects of Structural Deformation . 50 3.3.2 Human body loading . 54 3.3.3 Specific Absorption Rate (SAR) analysis . 57 3.4 Chapter Conclusions . 59 4 Electrically Small Implantable Antenna 61 4.1 Design Challenges . 62 4.2 Multi-layered Implantable Antenna . 64 4.3 Numerical Phantom Selection for Implant Study . 68 4.3.1 Simulation Setup . 69 4.3.2 Results and Discussion . 71 viii CONTENTS 4.4 Practical Realization . 73 4.4.1 Measurements within Tissue . 74 4.5 Chapter Contributions . 75 5 Through- and across-body communication 77 5.1 Introduction . 78 5.1.1 Wearable Sensor Antenna for Through-body communication 78 5.1.2 Wearable Sensor Node Architecture .
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