RECONFIGURABLE ANTENNAS FOR MICROWAVE IMAGING ANKITA ADARSH MALHOTRA BHARTI SCHOOL OF TELECOMMUNICATIONS TECHNOLOGY AND MANAGEMENT INDIAN INSTITUTE OF TECHNOLOGY DELHI AUGUST 2017
Indian Institute of Technology Delhi (IITD), New Delhi, 2017
RECONFIGURABLE ANTENNAS FOR MICROWAVE IMAGING by ANKITA ADARSH MALHOTRA Bharti School of Telecommunications Technology and Management Submitted in fulfillment of the requirements of the degree of Doctor of Philosophy to the INDIAN INSTITUTE OF TECHNOLOGY DELHI AUGUST 2017
DEDICATION This dissertation is dedicated to my family (specially my husband) for their immense love and support and to my supervisor for his sincere advice, direction and counsel.
EPIGRAPH Take up one idea. Make that one idea your life - think of it, dream of it, live on that idea. Let the brain, muscles, nerves, every part of your body, be full of that idea, and just leave every other idea alone. This is the way to success.swami Vivekananda
CERTIFICATE This is to certify that the thesis entitled, RECONFIGURABLE ANTENNAS FOR MICROWAVE IMAGING, being submitted by Mrs. Ankita Adarsh Malhotra for the award of the degree of Doctor of Philosophy to the, Bharti School of Telecommunications Technology and Management Indian Institute of Technology Delhi, New Delhi, is a record of bonafide research work carried out by her under my guidance and supervision. Mrs. Ankita Adarsh Malhotra has fulfilled the requirements for the submission of this thesis, which to our knowledge has reached the requisite standard. The results contained in this thesis have not been submitted in part or in full to any other university or institute for the award of any degree or diploma. Date: Place: New Delhi (Dr. Ananjan Basu) Professor Centre for Applied Research in Electronics Indian Institute of Technology Delhi Hauz Khas, New Delhi-110016, India
ACKNOWLEDGEMENTS This dissertation would not be possible without the help and support of many people. First, I would like to thank my supervisor, Prof. Ananjan Basu, for allowing me to continue with this thesis topic. His technical insight complimented with his understanding and patience make him one of the remarkable persons I have ever met. I sincerely thank him for his contributions to my personal and professional growth. I would also thank Prof. Shiban. K. Koul and Prof. Mahesh P Abegaonkar for taking the time to serve on my dissertation committee. I appreciate their contributions for reviewing this dissertation and participating in the oral presentation. Next, I would like to thank all of my colleagues here in the RF and Microwave group for making this journey a pleasant experience, including, Dr. Manoj Singh Parihar, Dr. Madhur Deo Upadhyay, Dr. Ritabrata Bhattacharya, Dr. Lalithendra Kurra, Dr. Sukomal Dey, Sanjeev Kumar, Dr. Srujana Kagita, Saurabh Pegwal, Rajesh Singh, Robin Kanyal, Deepika Sipal, Anushruti Jaiswal, Ayushi Barthwal, Amit Kumar Singh, Pranav Srivastava, Harikesh and Shakti Singh Chauhan. Their friendships made this journey enjoyable and will make my graduation memorable. I would like to thank Mr. Ashok Pramanik for his support and help rendered during my research work. I would also like to express my gratitude to all respected faculty and staffs members from the CARE at IIT Delhi, for all of the support that they have given me during my dissertation period. Finally, I would like to thank my family for their steadfast support particularly my parents, Mr. Ashwani Kumar Katyal and Mrs. Pushpa Katyal and my husband, Adarsh Malhotra. The constant encouragement by my siblings, Aayush Kumar Katyal and Nikita Katyal and strong support by my in-laws has been really helpful. They all encouraged me at every step by investing their considerable time and never doubted on my ability to complete the task. I needed it the most and I will forever be grateful to them. Ankita Adarsh Malhotra
ABSTRACT This dissertation presents design and analysis of stacked microstrip antennas and a reconfigurable stacked antenna for application in microwave imaging systems. The thesis is broadly divided into three parts. The first part of the thesis focuses on developing a far-field microwave imaging technique for metallic targets kept in a realistic noisy environment (without anechoic chamber). Standard waveguide antennas are used initially to study image reconstruction of regular and irregular shaped objects. Two-dimensional target scanning is done using randomly distributed sensors to generate an image. Next part of thesis covers design and analysis of stacked microstrip antennas. Stacked microstrip antennas are designed to operate in microwave bands, and the focus here is on X-band and C-band. Stacked antenna properties and the effect of different design parameters are studied extensively. Further, circuit-level analysis of stacked antennas is done based on transmission-line model theory. A novel transmission-line model applicable to a large class of stacked antennas is developed with the exclusion of slot-coupling in the model, i.e. antennas without slots are considered. The model s response is found to be in agreement with simulated and measured results. The implementation of the developed model is further studied for reconfigurable X-band stacked antenna design. As the model describes the circuit-level behaviour of stacked antenna, it can be extended for arriving at an initial design of an arbitrary stacked antenna with desired response, through fast circuit-level optimizations. To validate this, a C-band stacked antenna is designed using the proposed transmission-line model which is further optimised using EM simulations to arrive at the final design. The last part of the thesis concentrates on carrying out microwave imaging using designed stacked microstrip antennas operating in X-band and C-band. Several real-life metallic objects are considered as targets for performing microwave imaging in far-field region. Image reconstruction of individual targets kept in free-space is observed in the two frequency bands (X-band and C-band). Further, two targets are kept in free-space and imaged to observe the achievable resolution. Next, image reconstruction of targets, hidden behind dielectric material is studied.
Finally, imaging is done using frequency reconfigurable/switchable stacked antenna design that switches between X-band and C-band antenna through pin diodes (connected to a common feed line). Target information contained in these two different frequency bands is combined in two ways: in one way by adding image matrices, obtained in different bands individually; and in the other way by combining the received signals (in two different frequency bands) in frequency domain, to have more spectral information of the target. The study shows that image gets improved by using the first method, while second method still has scope for improvement.
स र श यह श ध स ट कड म ईक र स ट स ट प ए ट न और र क स ट फ ग बल स ट कड ए ट न क ड ज इन एव ड श ल षण क प रस त त क त ह ए इनक उपय गगत क म इक र इम डज ग प रण ल म दर त ह इस र ध क म ख य र प स त न भ ग म ब ट गय ह थ ड क पहल भ ग द क ष त म श र ग ल / क ल हल प र त रण म ख ह ई ध त क बन वस त ओ क म इक र इम डज ग गवकगसत क न क तकन क / गवगध क ड क पर क ड त ह स ट ड व व ग इड ए ट न क उपय ग, प र म भ म डनयडमत और अडनयडमत आक र क स त ओ क छड प नडनडम डण क अध ययन क न ह त गकय गय ह अगनयगमत र प स गवगभन न स थ न प लग ए ह ए स स क द व द आय म लक षय स क गन ग क गई ह, लक षय क ब हत प रगतगबम ब उत पन न क न क गलए थ ड क अगल भ ग स ट कड म ईक र स ट स ट प ए ट न क ड ज इन और उसक ड श ल षण प प रक र ड लत ह स ट कड म ईक र स ट स ट प ए ट न क म इक र ब म क म करन क डलए त य र गकय गय ह, और यह ध य न एक स-ब और -ब क ष त पर ह यह स ट क ए ट न क ग ण और इसक अलग अलग ड ज इन म नक क प रभ क गवस त त र य प स अध ययन गकय ज ह ह इ क अल, स ट कड ए ट न क डकड ट स तर क ड श ल षण स च ल इन म ल ड द त क आध र पर डकय गय ह स ट कड ए ट न क एक बड गड पर प रय ग क न क गलए एक नव न स च ल ईन म ल क ड कड त डकय गय ह डज डबन स ल ट क भ ए ट न क ड शल षण म भ ह म ल क प रडतडक रय क क डत म और म डपत पररण म क अन र प प य ह ड कड त म ल क डक रय न वयन ह त ररल न फ गरबल एक स ब स ट कड ए ट न क ड ज इन क प न: अध ययन डकय ज रह ह च गक यह म ल स ट कड ए ट न क डकड ट स तर क व य ह र क बत त ह, इस आब ट स ट कड ए ट न क प र र डभक ड ज इन पर पह चन क पहल कदम म न ज कत ज डकड ट स तर अन क लन क अन र प इन फ त पररण म दत ह इ म न य करन क डलए, एक -ब स ट कड ए ट न ज प रस त ड त चरण ल इन म ल प आध र त ह, तथ उसम ईएम ड म ल शन क उपय ग डकय गय ह, अ डतम ड ज इन पर पह चन क डलए अन क डलत थ ड क अ गतम भ ग म इक र इम डज ग पर क ड त ह डज म स ट कड म ईक र स ट स ट प ए ट न क प रय ग करत हए एक स-ब और -ब क ष त म प रच गलत गकय गय ह कई ध त क स त ओ क म इक र ईम डज ग क डलए लक षय क र प म प रय ग डकय गय ह म क त अ तररक ष म रख व यन फक तगत लक ष क छड प नडनडम डण द आ ड ब (एक स-ब और -ब ) म गन गक षत क गई ह तथ द लक षय क प रडतडबम ब क प र न फ क भ डनर क षण डकय ह इ क अडतररक त डक स त क प छ डछप हए लक षय क प रडतडबम ब क प र न फ क भ डनर क षण डकय गय ह अ तत:, द क ष त म क म क न व ल र क ग ग र बल ए ट न द व गवगभन न लक षय क प रगतगबम ब प र पत गकय गय ह इसम द अलग अलग क ष त म उपलब ध लक ष क स चन क ज ड गय ह ऐस क न स हम गकस भ लक षय क ब हत प रगतगबम ब क प र स ट ह ई ह
TABLE OF CONTENTS Certificate... i Acknowledgements... iii Abstract... v Table of Contents... vii List of Figures... xiii List of Tables... xxiii Chapter 1: Introduction.1 1.1. Microwave Imaging...1 1.2. Advantages of Microwave Imaging...3 1.3. Classification of Microwave Imaging Systems...4 1.4. Microwave Imaging System Requirements...5 1.5. Stacked Microstrip Patch Antenna...6 1.5.1 Properties of stacked microstrip patch antennas...8 1.6. Advantages of Stacked Antennas as Transceiver Unit in Microwave Imaging System.....8 1.7. Reconfigurable Stacked Antennas for Microwave Imaging...10 1.8. Scope and Objectives of the Work....10 1.9. Thesis Organisation..... 13 Chapter 2: Microwave Imaging...16 2.1. Introduction...16 2.2. Factors Crucial for Imaging...17 2.3. Measurement Setup...17 2.4. Target Scanning...19
2.5. Imaging Algorithm...21 2.5.1. Data Processing...21 2.5.2. Image Reconstruction...25 2.6. Reconstructed Images.......28 2.7. Observations......30 2.8. Conclusion...32 Chapter 3: Stacked Microstrip Antenna...33 3.1. Introduction...33 3.2. Stacked antenna design (Stage I)...35 3.2.1. Driven patch of stacked antenna at stage...35 3.2.2. Parasitic patch I of stacked antenna at stage I...36 3.2.3. Parasitic patch II of stacked antenna at stage I...39 3.3. Stacked antenna design (stage II)...40 3.4. Properties of initial antenna...42 3.4.1. Surface Current Distribution...42 3.4.2. Antenna Gain...43 3.4.3. Radiation Pattern...44 3.4.4. Initial Stacked Antenna with Large Ground Plane...45 3.5. Improved/Proposed Stacked Antenna Design (Stage III)...47 3.6. Proposed stacked antenna properties...49 3.6.1. Surface Current Distribution...49 3.6.2. Gain and Efficiency...50 3.6.3. Radiation Pattern...51 3.6.4. Proposed Stacked Antenna with Large Ground Plane...53 3.7. Conclusion...57 Chapter 4: Stacked Antenna Analysis Based on Transmission Line Theory...59 4.1. Introduction...59
4.2. Method of Analysis...60 4.2.1. Transmission Line Model Parameters...65 4.3. Proposed Stacked Antenna Design...67 4.4. Transmission Line Model Analysis...70 4.4.1. Analysis of Single Layered Antenna...71 4.4.2. Analysis of Two Layered Stacked Antenna...74 4.4.3. Analysis of Three Layered Broadband Stacked Antenna...78 4.5. Sensitivity of the Model...82 4.6. Conclusion...85 Chapter 5: Implementation And Application Of Transmission-Line Model Analysis...86 5.1. Introduction...86 5.2. Implementation of the transmission-line model on reconfigurable stacked antenna..87 5.2.1. Frequency Reconfigurable Stacked Antenna...87 5.2.2. Analysis of Reconfigurable Stacked Antenna...89 5.3. Design of C-band stacked microstrip antenna using transmission-line model...94 5.3.1. Initial Antenna Design using circuit-level optimizations...95 5.4. Conclusion...104 Chapter 6: Microwave Imaging Using Stacked Microstrip Antennas...105 6.1. Introduction...105 6.2. Resolution in range and cross-range...107 6.3. Comparison of waveguide antenna and stacked antenna response...108 6.4. Microwave imaging using proposed X-band stacked antenna...110 6.4.1. Imaging of Targets in Free Space...111 6.4.2 Imaging of targets hidden behind a dielectric material...117 6.5. Microwave imaging using C-band stacked antenna...119 6.5.1. Imaging of Targets kept in Free Space...121 6.5.2 Imaging of targets hidden by dielectric medium...126
6.6. Conclusion...128 Chapter 7: Microwave Imaging Using Reconfigurable Stacked Antenna...130 7.1. Introduction...130 7.2. Reconfigurable Stacked Antenna...131 7.3. Measurement Set-up Employing Reconfigurable Stacked Antenna...134 7.4. Image Reconstruction Using Reconfigurable Stacked Antenna, Method I...136 7.5. Image Reconstruction Using Reconfigurable Stacked Antenna, Method II...140 7.6. Conclusion...144 Chapter 8: Conclusions and Future Scope..146 8.1. Summary of the Thesis.146 8.2. Future Scope of the Work...148 References...150 Publications...159 Brief Bio-Data of the Author.160