University of South Carolina Scholar Commons Theses and Dissertations 2017 Wideband Low Side Lobe Aperture Coupled Patch Phased Array Antennas Dhruva Poduval University of South Carolina Follow this and additional works at:http://scholarcommons.sc.edu/etd Part of theElectrical and Computer Engineering Commons Recommended Citation Poduval, D.(2017).Wideband Low Side Lobe Aperture Coupled Patch Phased Array Antennas.(Master's thesis). Retrieved from http://scholarcommons.sc.edu/etd/4144 This Open Access Thesis is brought to you for free and open access by Scholar Commons. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of Scholar Commons. For more information, please [email protected]. WIDEBAND LOW SIDE LOBE APERTURE COUPLED PATCH PHASED ARRAY ANTENNAS by Dhruva Poduval Bachelor of Engineering Fr. C. Rodrigues Institute of Technology, University of Mumbai, 2010 Submitted in Partial Fulfillment of the Requirements For the Degree of Master of Science in Electrical Engineering College of Engineering and Computing University of South Carolina 2017 Accepted by: Mohammod Ali, Director of Thesis Grigory Simin, Reader Cheryl L. Addy, Vice Provost and Dean of the Graduate School © Copyright by Dhruva Poduval, 2017 All Rights Reserved. ii ACKNOWLEDGEMENTS I am very grateful to my thesis advisor Dr. Mohammod Ali for his patience, advice and encouragement throughout this endeavor. Without his support this research would not have been possible. I would also like to thank my colleague Dr. Chamok Nowrin Hasan for all the help and assistance that he provided me with when I just started working on this thesis. I have got to learn a great deal from him. Lastly, I would like to thank my parents for all their blessings and financial support which has enabled me to attend graduate school. iii ABSTRACT Low profile printed antenna arrays with wide bandwidth, high gain, and low Side Lobe Level (SLL) are in great demand for current and future commercial and military communication systems and radar. Aperture coupled patch antennas have been proposed to obtain wide impedance bandwidths in the past. Aperture coupling is preferred particularly for phased arrays because of their advantage of integration to other active devices and circuits, e.g. phase shifters, power amplifiers, low noise amplifiers, mixers etc. However, when designing such arrays, the interplay between array performance characteristics, such as gain, side lobe level, back lobe level, mutual coupling etc. must be understood and optimized under multiple design constraints, e.g. substrate material properties and thicknesses, element to element spacing, and feed lines and their orientation and arrangements with respect to the antenna elements. The focus of this thesis is to investigate, design, and develop an aperture coupled patch array with wide operating bandwidth (30%), high gain (17.5 dBi), low side lobe level (20 dB), and high Forward to Backward (F/B) ratio (21.8 dB). The target frequency range is 2.4 to 3 GHz given its wide application in WLAN, LTE (Long Term Evolution) and other communication systems. Notwithstanding that the design concept can very well be adapted at other frequencies. Specifically, a 16 element, 4 by 4 planar microstrip patch array is designed using HFSS and experimentally developed and tested. Starting from mutual coupling minimization a corporate feeding scheme is designed to achieve the needed performance. iv To reduce the SLL the corporate feeding network is redesigned to obtain a specific amplitude taper. Studies are conducted to determine the optimum location for a metallic reflector under the feed line to improve the F/B. An experimental prototype of the antenna was built and tested validating and demonstrating the performance levels expected from simulation predictions. Finally, simulated beam scanning in several angles of the array is shown considering specific phases for each antenna element in the array. v TABLE OF CONTENTS ACKNOWLEDGEMENTS ........................................................................................................ iii ABSTRACT .......................................................................................................................... iv LIST OF TABLES .................................................................................................................. ix LIST OF FIGURES ...................................................................................................................x CHAPTER 1: INTRODUCTION ..................................................................................................1 1.1 MOTIVATION FOR WORK .......................................................................................1 1.2 OVERVIEW OF THESIS ............................................................................................2 CHAPTER 2: APERTURE COUPLED PATCH .............................................................................4 2.1 INTRODUCTION ......................................................................................................4 2.2 SLOT FED PATCHES ...............................................................................................5 2.3 DESIGN AND OPTIMIZATION OF SINGLE ELEMENT APERTURE COUPLED PATCH ANTENNA ..................................................................................7 2.4 DESIGN OF SINGLE ELEMENT PATCH ANTENNA ..................................................15 CHAPTER 3: LINEAR AND PLANAR ARRAY ANTENNAS .......................................................18 3.1 INTRODUCTION ....................................................................................................18 3.2 THE ARRAY FACTOR ...........................................................................................18 3.3 FOUR ELEMENT LINEAR ARRAY ..........................................................................22 3.4 4X4 PLANAR ARRAY ANTENNA ..........................................................................28 CHAPTER 4: ANTENNA ARRAY FEED NETWORKS ...............................................................35 vi 4.1 INTRODUCTION....................................................................................................35 4.2 THE CORPORATE FEED NETWORK.......................................................................36 4.3 4X4 ARRAY WITH INCREASED SEPARATION AND CORPORATE FEED NETWORK ..............................................................................47 CHAPTER 5: REDUCING SIDE LOBE AND BACKLOBE LEVELS IN PLANAR ARRAYS ..............50 5.1 INTRODUCTION....................................................................................................50 5.2 BINOMIAL ANTENNA ARRAYS ............................................................................51 5.3 DOLPH-CHEBYSHEV ANTENNA ARRAYS .............................................................54 5.4 SYNTHESIZING ARRAY FACTORS ........................................................................58 5.5 AMPLITUDE TAPERED CORPORATE FEED ............................................................61 5.6 REDUCING BACKLOBE RADIATION .....................................................................67 CHAPTER 6: FABRICATION AND MEASUREMENT OF ARRAY ...............................................75 6.1 INTRODUCTION....................................................................................................75 6.2 FABRICATION ......................................................................................................76 6.3 MEASUREMENT RESULTS FOR 4X4 ARRAY .........................................................81 6.4 MEASUREMENT RESULTS FOR 4X4 ARRAY WITH REFLECTOR .............................86 6.5 MEASUREMENT RESULTS FOR 4X4 ARRAY WITH SUPERSTRATE .........................89 6.6 MEASUREMENT RESULTS FOR 4X4 ARRAY WITH REFLECTOR AND SUPERSTRATE .................................................................92 CHAPTER 7: PHASED ARRAY ...............................................................................................96 7.1 INTRODUCTION....................................................................................................96 7.2 BEAM STEERING .................................................................................................96 CHAPTER 8: CONCLUSION AND FUTURE WORK ................................................................105 8.1 CONCLUSION .....................................................................................................105 vii 8.2 FUTURE WORK ..................................................................................................106 REFERENCES .....................................................................................................................108 viii LIST OF TABLES Table 2.1 Antenna parameters ...........................................................................................15 Table 3.1 Summary of simulation results for linear array .................................................27 Table 3.2 Summary of simulation results for individually fed planar array antenna ........34 Table 4.1 Summary of simulation results for individually fed planar array antenna with increased separation ...........................................................................................................46 Table 4.2 Summary of simulation results for planar array antenna fed using a corporate feed .....................................................................................................................................49 Table 5.1 Summary of radiation pattern data for binomial array ......................................54 Table 5.2 Summary of radiation pattern data for Dolph-Chebyshev array........................57 Table 5.3 Summary of radiation pattern data for synthesized array ..................................61 Table 5.4 Summary of radiation pattern data for array with tapered corporate feed .........67 Table 5.5 Simulation data for the 4X4 array with metal reflector .....................................74 Table 6.1 Measured data for 4X4 array .............................................................................85 Table 6.2 Measured data for 4X4 array with reflector.......................................................88 Table 6.3 Measured data for 4X4 array with superstrate ...................................................92 Table 6.4 Measured data for 4X4 array with superstrate and reflector .............................95 Table 7.1 Summary of radiation pattern data with main beam at θ = +10𝑜,Φ = 90𝑜 ..100 ix