DESIGN AND TESTING OF HELICAL ANTENNAS FOR A RF TEST FACILITY _______________________________________ A Thesis presented to the Faculty of the Graduate School at the University of Missouri-Columbia _______________________________________________________ In Partial Fulfillment of the Requirements for the Degree Master of Science _____________________________________________________ by MIKE YOUNG Dr. Randy Curry, Thesis Supervisor MAY, 2012 The undersigned, appointed by the dean of the Graduate School, have examined the Thesis entitled DESIGN AND TESTING OF HELICAL ANTENNAS FOR A RF TEST FACILITY Presented by Mike B Young A candidate for the degree of MASTER OF SCIENCE IN ELECTRICAL ENGINEERING And hereby certify that, in their opinion, it is worthy of acceptance. Professor Dr. Randy Curry, ECE Professor Dr. Carmen Chicone, MATH Professor Dr. Gregory Triplett, ECE Professor Dr. Justin Legarsky, ECE ACKNOWLEDGEMENTS This thesis would not have been possible without the guidance, support, encouragement, and pressure from Dr. Randy Curry. Dr. Curry has been a wonderful influence in my life, and I would not be where I am today without him. I am deeply indebted to him for all that he has done for me. I am extremely appreciative of the help that Dr. Bob Druce has given me throughout his involvement at the University of Missouri-Columbia. His office door is always open, and he is always more than willing to help anyone who walked in. I have taken much advantage of this, and am very grateful. None of this could have been accomplished if it weren't for the help of our lab supervisor, Bill Carter. Bill's management abilities, leadership skills, and charm meant that if something needed to be accomplished around lab, Bill would be the one who could produce results. My good friend Stan Ikpe has literally been a lifesaver throughout my college career. The friendship and moral support that he has provided over the years has been the source of my motivation. Having gone through undergraduate and graduate school together, we have shared many cherished memories. Stan has been, and always will be, a wonderful friend. I am also grateful to many of my fellow students, both graduate and undergraduate, who have supported me on this project. Very few things in life can be accomplished on your own as easily as they can with the help from wonderful people around you. I would finally like to acknowledge the help from family. Without their continued support, this would have not been possible. ii TABLE OF CONTENTS ACKNOWLEDGEMENTS ................................................................................................................................. ii TABLE OF CONTENTS .................................................................................................................................... iii LIST OF FIGURES ............................................................................................................................................ v LIST OF TABLES ............................................................................................................................................. xi ABSTRACT .................................................................................................................................................... xii 1. INTRODUCTION TO RF FACILITIES ......................................................................................................... 1 2. ANTENNA BACKGROUND ...................................................................................................................... 6 2.1 Radiation Mechanism ................................................................................................................... 7 2.2 Radiation Patterns ...................................................................................................................... 10 2.3 Field Regions ............................................................................................................................... 14 2.4 Power Density ............................................................................................................................. 16 2.5 Beamwidth .................................................................................................................................. 18 2.6 Directivity .................................................................................................................................... 19 2.7 Efficiency ..................................................................................................................................... 20 2.8 Gain ............................................................................................................................................. 21 2.9 Realized Gain ............................................................................................................................... 22 2.10 Polarization ................................................................................................................................. 23 2.11 Friis Transmission Equation ........................................................................................................ 24 2.12 Radar Cross Section..................................................................................................................... 25 2.13 Radar Range Equation ................................................................................................................. 26 2.14 S11 and VSWR .............................................................................................................................. 27 3. HELICAL ANTENNAS ............................................................................................................................ 29 3.1 Introduction to Helical Antennas ................................................................................................ 30 3.2 Modes of Operation .................................................................................................................... 32 3.2.1 Helical Transmission Modes................................................................................................ 33 3.2.2 Normal Mode ...................................................................................................................... 34 3.2.3 Axial Mode .......................................................................................................................... 36 3.3 Performance Optimization .......................................................................................................... 38 3.3.1 Maximum Gain .................................................................................................................... 39 iii 3.3.2 Optimal Circumference ....................................................................................................... 40 3.3.3 Optimal Ground Plane ........................................................................................................ 41 4. HELICAL ANTENNA DESIGN ............................................................................................................... 45 4.1 Initial Simulation ......................................................................................................................... 46 4.2 First Build .................................................................................................................................... 50 4.3 Dielectric-Loaded CST Simulations .............................................................................................. 56 4.4 Design Modifications .................................................................................................................. 59 4.5 Optimized Turns Ratio Construction ........................................................................................... 62 4.6 Commercial Results ..................................................................................................................... 67 4.7 Bandwidth Improvements .......................................................................................................... 69 5. EQUIPMENT & MEASUREMENTS ........................................................................................................ 77 5.1 Anechoic Chamber ...................................................................................................................... 77 5.2 Equipment ................................................................................................................................... 84 5.3 Gain Measurements .................................................................................................................... 86 5.4 Turntable ..................................................................................................................................... 89 6. CONCLUSION ..................................................................................................................................... 146 APPENDIX A - MATLAB CODE FOR CALCULATING ANTENNA GAIN........................................................ 152 APPENDIX B - MATLAB CODE FOR TURNTABLE BASED POLAR PLOTS ................................................... 157 APPENDIX C - "360° ANTENNA" REPORT ................................................................................................ 167 Bibliography .............................................................................................................................................. 185 iv LIST OF