METAMATERIAL MICROSTRIP TRANSMISSION LINE BASED MICROWAVE CIRCUITS AND SENSORS By Nophadon Wiwatcharagoses A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Electrical Engineering 2012 ABSTRACT METAMATERIAL MICROSTRIP TRANSMISSION LINE BASED MICROWAVE CIRCUITS AND SENSORS By Nophadon Wiwatcharagoses There is significant interest in metamaterials (MTMs) for the design of novel microwave circuits and sensors. Metamaterials with their unique properties allow for the design of circuits and sensors that are compact and provide new functionalities that are difficult to achieve using conventional design approaches. Split ring resonators (SRRs) and complimentary split ring resonators (CSRRs) have been studied in great detail over the last decade as metamaterial structures. However, so far these designs have largely been implemented at low-frequencies (1-3 GHz) and require complex fabrication. To design active microwave circuits, planar metamaterial unit cell structures that readily allow the integration of active devices as an integral part of the structure are necessary. This thesis investigates the use of composite right/left handed microstrip metamaterial transmission lines in the design of microwave planar circuits and sensors. Microstrip based designs are compatible with wafer-level integration and lead to the integration of active device elements as an integral part of the metamaterial unit cell. Microfluidic channels can also be integrated with these planar structures to form sensors. Here, high frequency metamaterial transmission lines integrated with active devices to design microwave circuits are studied. Such metamaterial structures that are sensitive to their environments in the near-field are also investigated for sensor design applications. Metamaterial structures can be designed to achieve high field strengths at local spots within the unit cell structure. Dielectric (or capacitive) loading at these local spots is investigated in detail. Actively changing the capacitance at these spots using varactor diodes leads to reconfigurable circuits and allows for the design of new functions that are difficult to achieve using conventional circuit designs. In contrast, observing a change in the performance of microwave circuits by loading with biological or chemical samples allows for the design of novel microwave sensors. The dispersion diagram of these structures shows composite right/left handed properties. These properties change upon loading with capacitive elements and are analyzed to demonstrate the working principle of the sensor circuits. In order to accommodate active device elements as an integral part of the MTM structure, a new metamaterial unit cell is proposed in the X-band (7.5-12 GHz) frequency range that utilizes single-side metallization. Detailed analysis of the unit cell is carried out to incorporate varactor diodes at optimum locations for the design of reconfigurable or tunable microwave circuits. A novel reconfigurable power splitter with unequal power division function, a wide-band reconfigurable X-band phase shifter with high linearity of phase shift, and a miniaturized reconfigurable antenna are designed and demonstrated. Apart from the design of high frequency microwave circuits, metamaterial structures have been exploited in the designs of novel microwave sensors. A metamaterial-inspired microfluidic sensor and a novel high-Q compact volatile molecular sensor are designed and demonstrated. Furthermore, a near-field RF probe array for material characterization and simultaneous sub- wavelength imaging of structures is demonstrated. Sensors built using metamaterials-based microstrip transmission show high sensitivity compared to conventional designs. Copyright by NOPHADON WIWATCHARAGOSES 2012 For loving memory of my dear grandparents and In memory of 26 years of our sincere friendship, Werachai Wongkiatthaworn. v ACKNOWLEDGEMENTS There are many people who deserve acknowledgement throughout my years at Michigan State University. First and foremost, many special thanks to my advisor, Dr. Premjeet Chahal for everything that he has done for me. His magnificent ideas and suggestions inspired me to discover the new things while I was doing the research. In other words, this thesis is really the outcome of his encouragement, support and generosity over many years in my research under his guidance. I could not have asked for better guidance from anyone. I would like to express my gratitude to my committee members, Dr. Tim Hogan, Dr. Alejandro R. Diaz and Dr. Fang Z. Peng for their invaluable comments and for inspirational ideas for my research since part B of the doctoral qualifying examination. I really appreciate their help and guidance and most importantly for serving as my PhD committee. Also, I would like to thank my colleagues at the Terahertz Systems Laboratory, NDE laboratory and EM Research Group for their helpful discussions. Many thanks to Brian Wright for helpful discussions in microfabrication. Special thanks to Dr. J. A. Hejase, X. Yang, C. S. Meierbachthol, J. C. Myers, C. Acosta and my best labmate - Kyoung Youl Park for all their help, encouragement as well as sincere friendship in many years at Michigan State University. I sincerely hope our friendship never ends. Especially, I would like to thank Gordon Jensen, Heidi Jensen and their cute daughter - Nori Jensen for their good friendships and entire dedication during these years in Michigan. They introduced me to learn many things about American culture and visit various places in Michigan. Moreover, they helped me a lot with assimilation in language. I had a great time with them and their hospitality will be missed. vi Furthermore, I am thankful to the Royal Thai Government and the Department of Electrical and Computer Engineering at King Mongkut’s University of Technology (North Bangkok) for funding my PhD study in the States. I express my greatest thanks to my friends in Thailand, especially Chaiyan Suwancheewasiri, Chavana Yoopakdee, Dr. Phoemphun Oothongsap and Dr. Pisit Liutanakul, for their steadfast friendships and strong support, despite the large distance between us. Also, I would like to thank my Thai friends at Michigan State University, especially Tanatorn Tongsumrith and his family for their help and encouragement throughout my studies at MSU. Finally, I deeply want to thank my parents, Opas Wiwatcharagoses, Orasa Wiwatcharagoses, Niwat Palapinyo, Tadsanee Palapinyo, and my parents in-law, Piboon Anuraksakul, Prapai Anuraksakul and all of my family members for their generous contributions and unconditional support, especially the last period of my study here. Also, I would like to express my sincere thanks to my wife’s colleagues and neurosurgery team including critical care unit staff at Rajavithi Hospital who provided my beloved wife with the best medical treatment in time to save her life. It is really a miracle that I still have her in my life; I could not imagine my life without her. Lastly, the most important one to whom I am indebted is my beloved wife, Dr. Kittiyaporn Wiwatcharagoses. My deepest gratitude is reserved for her whom I love with all my heart. Everything in my life is possible because of her love, her support, her understanding, her trust, her belief and especially her sacrifice. Although she was in the most critical time of her life, she still insisted and convinced me to stay for completing my PhD study as well as promised to stay strong until I return. vii TABLE OF CONTENTS LIST OF TABLES .......................................................................................................................... x LIST OF FIGURES ....................................................................................................................... xi CHAPTER 1 INTRODUCTION .......................................................................................................................... 1 1.1 Background and Motivation ............................................................................................... 1 1.2 Dissertation Overview ........................................................................................................ 3 1.3 Research Contribution ........................................................................................................ 6 CHAPTER 2 FUNDAMENTAL THEORY OF METAMATERIALS................................................................ 9 2.1 Definition of Metamaterials and Left-Handed Media .......................................................... 9 2.2 Experimental Left-Handed Metamaterials .......................................................................... 11 2.3 Composite Right/Left-Handed (CRLH) Metamaterials...................................................... 14 2.3.1 Pure Right-Handed Transmission Line ...................................................................... 20 2.3.2 Pure Left-Handed Transmission Line ........................................................................ 21 2.3.3 Composite Right/Left Handed Transmission Line (Unbalanced) ............................. 23 2.3.4 Composite Right/Left Handed Transmission Line (Balanced) .................................. 24 2.4 LC Network Implemented on Metamaterials ..................................................................... 26 2.5 Periodic Analysis Addressed LC Loaded Transmission Line Network ............................. 29 2.5.1 Periodic Lumped-Element Right-Handed Line ........................................................