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Synthetic Aperture Radar-Based Techniques and Reconfigurable Antenna Design for Microwave Imaging of Layered Structures

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Synthetic Aperture Radar-Based Techniques and Reconfigurable Antenna Design for Microwave Imaging of Layered Structures Scholars' Mine Doctoral Dissertations Student Theses and Dissertations 2013 Synthetic aperture radar-based techniques and reconfigurable antenna design for microwave imaging of layered structures Mojtaba Fallahpour Follow this and additional works at: https://scholarsmine.mst.edu/doctoral_dissertations Part of the Electrical and Computer Engineering Commons Department: Electrical and Computer Engineering Recommended Citation Fallahpour, Mojtaba, "Synthetic aperture radar-based techniques and reconfigurable antenna design for microwave imaging of layered structures" (2013). Doctoral Dissertations. 1847. https://scholarsmine.mst.edu/doctoral_dissertations/1847 This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. SYNTHETIC APERTURE RADAR-BASED TECHNIQUES AND RECONFIGURABLE ANTENNA DESIGN FOR MICROWAVE IMAGING OF LAYERED STRUTURES by MOJTABA FALLAHPOUR A DISSERTATION Presented to the Faculty of the Graduate School of the MISSOURI UNIVERSITY OF SCIENCE AND TECHNOLOGY In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY in ELECTRICAL ENGINEERING 2013 Approved by Dr. Reza Zoughi, Advisor Dr. Richard E. DuBroff Dr. David J. Pommerenke Dr. Kristen M. Donnell Dr. Von L. Richards 2013 Mojtaba Fallahpour All Rights Reserved iii ABSTRACT In the past several decades, a number of microwave imaging techniques have been developed for detecting embedded objects (targets) in a homogeneous media. New applications such as nondestructive testing of layered composite structures, through-wall and medical imaging require more advanced imaging systems and image reconstruction algorithms (post-processing) suitable for imaging inhomogeneous (i.e., layered) media. Currently-available imaging algorithms are not always robust, easy to implement, and fast. Synthetic aperture radar (SAR) techniques are some of the more prominent approaches for image reconstruction when considering low loss and homogeneous media. To address limitations of SAR imaging, when interested in imaging an embedded object in an inhomogeneous media with loss, two different methods are introduced, namely; modified piecewise SAR (MPW-SAR) and Wiener filter-based layered SAR (WL-SAR). From imaging system hardware point-of-view, microwave imaging systems require suitable antennas for signal transmission and data collection. A reconfigurable antenna which its characteristics can be dynamically changed provide significant flexibility in terms of beam-forming, reduction in unwanted noise and multiplicity of use including for imaging applications. However, despite these potentially advantageous characteristics, the field of reconfigurable antenna design is fairly new and there is not a methodical design procedure. This issue is addressed by introducing an organized design method for a reconfigurable antenna capable of operating in several distinct frequency bands. The design constraints (e.g., size and gain) can also be included. Based on this method, a novel reconfigurable coplanar waveguide-fed slot antenna is designed to cover several different frequency bands while keeping the antenna size as small as possible. iv ACKNOWLEDGMENTS I am grateful with all of my being to my family. I believe I never could have embarked on my Ph.D. journey and finished it without an overwhelming support from my lovely mother and father. I am thankful to my sister for her help and especially for tutoring me in the past when I was trying to self-study over the summer to go directly from the third grade to the fifth grade in elementary school. I owe my older brothers for helping me be prepared for every new high school year over the summer. I cordially would like to thank my advisor, Dr. Reza Zoughi, for providing me with this opportunity to come here and do my Ph.D. I am thankful for the kind support, encouragement, and the many hours he has devoted to me. I not only learned many technical things from him but also how to look at the world from a different perspective. His statement, “you create your own world”, helped me to find my path in early days in here when I was trying to adapt to the place. I would like to thank Dr. Richard E. DuBroff, Dr. David J. Pommerenke, Dr. Von L. Richards, and Dr. Kristen M. Donnell for serving on my committee and for their valuable effort and the time they spent on my dissertation. I would also like to thank all my dear teachers, colleagues, and friends, at Applied Microwave Nondestructive Testing Lab (amntl) and Electromagnetic Compatibility (EMC) lab, in particular Dr. Jun Fan, Dr. Sergiy Kharkovsky, Dr. Mohammad Tayeb Ghasr, Dr. Joseph T. Case, Dr. Hamed Kajbaf, Mr. Ashkan Hashemi, Mr. Ali Foudazi, Mr. Arpit Kothari, Mr. Matthew Kempin, and Mr. Sanjay Tadepally. I would like to acknowledge the American Society for Nondestructive Testing (ASNT) for supporting this work partially by granting me a Graduate Fellowship Award (2009). Also, this research was in part sponsored by the Army Research Laboratory and was accomplished under Cooperative Agreement Number W911NF-10-2-0077. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Laboratory or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes not withstanding any copyright notation herein. v TABLE OF CONTENTS Page ABSTRACT ....................................................................................................................... iii ACKNOWLEDGMENTS ................................................................................................. iv LIST OF ILLUSTRATIONS ........................................................................................... viii LIST OF TABLES ........................................................................................................... xiv NOMENCLATURE ......................................................................................................... xv SECTION 1. INTRODUCTION ...................................................................................................... 1 1.1. BACKGROUND AND MOTIVATIONS .......................................................... 1 1.2. OBJECTIVES AND OVERVIEW OF DISSERTATION ................................. 7 2. FIELD CALCULATION IN A LAYERED STRUCTURE USING GREEN’S FUNCTION ................................................................................................................ 9 2.1. INTRODUCTION .............................................................................................. 9 2.2. WAVE PROPAGATION INSIDE A PLANAR LAYERED STRUCTURE .. 12 2.3. A POINT SOURCE EMBEDDED IN A LAYERED STRUCTURE .............. 13 2.3.1. Propagation Factor in Region 1 ( zlayer n , z ' layer m , n m) .......... 15 2.3.2. Propagation Factor in Region 2 ( zlayer n , z ' layer m , n m) .......... 15 2.3.3. Propagation Factor in Region 3 ( zlayer n , z ' layer m , n m) .......... 16 2.3.4. Scalar Green’s Function Calculation for Layered Structure .................. 16 2.3.5. Examples ................................................................................................ 16 2.4. A VECTOR DISTRIBUTED SOURCE IN A LAYERED STRUCTURE ..... 20 2.4.1. Calculation of Ge ( r , r ') .......................................................................... 22 2.4.2. Calculation of Ge ( r , r ') .................................................................... 25 2.4.3. Embedded Electric Dipole Antenna in a Layered Structure. ................. 28 2.5. CONCLUSION ................................................................................................. 29 3. SAR-BASED MICROWAVE IMAGING OF EMBEDDED ACIVE TARGETS . 31 3.1. INTRODUCTION ............................................................................................ 31 3.2. RELATIONSHIP BETWEEN QUALITATIVE IMAGE AND COLLECTED DATA....................................................................................... 34 vi 3.3. SAR ALGORITHM .......................................................................................... 37 3.4. MODIFIED PIECEWISE SAR ALGORITHM ............................................... 38 3.5. WIENER FILTER-BASED SAR ..................................................................... 40 3.6. SIMULATIONS ............................................................................................... 43 3.6.1. Finding a Radiating Trace in a Single Layer PCB ................................. 45 3.6.2. Locating Radiating Traces in Multilayered PCB. .................................. 51 3.6.3. Experimental Result ............................................................................... 55 3.7. CONCLUSION ................................................................................................. 58 4. MONOSTATIC SAR-BASED MICROWAVE IMAGING OF EMBEDDED PASSIVE OBJECTS ................................................................................................ 59 4.1. INTRODUCTION ............................................................................................ 59 4.2. MONOSTATIC SAR AND MPW-SAR .......................................................... 60 4.3. MONOSTATIC WL-SAR ...............................................................................
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