A 24FT/7.3M PARABOLIC REFLECTOR ANTENNA PERFORMANCE & FEED DESIGN ANALYSIS A Thesis Presented to the Faculty of the College of Science & Technology Morehead State University In Partial Fulfilhnent of the Requirements for the Degree Master of Science by Anthony Shelley 2010 /YlSU Tif t;-S£S '1:ll. 3g~4 S54St Accepted by the faculty of the College of Science & Technology, Morehead State University, in partial fulfillment of the requirements for the Master of Science degree. flfmt,7£_1 -if!J w Director of Th7 Master's Committee: A.£2,.,.._e-) €/<:J ~ ,Chair ~:;A--- .l>~ - 1.\-A-lu.S: Ct-1-A--PWVh-J c~ 0~ Date A 24FT/7.3M PARABOLIC REFLECTOR ANTENNA PERFORMANCE & FEED DESIGN ANALYSIS Anthony Shelley, M.S. Morehead State University, 2010 Director of Thesis: -~~~-'-"'""--"-..__-c;;.__..,_,_,_~u.,__.."---'-_,_Ab l):l1 a._ j ZCJt" 'f /j'I" I ____ The pmpose of this thesis was to analyze existing feeds for a 24 foot/7.3 meter parabolic dish antenna as well as analyzing the dish geometry. This data was then used to determine if the existing feeds were capable of conducting research in the L Band range and comparative analysis of both existing feeds was conducted to determine the better performing feed. Both feeds were determined to be operational within L Band, with existing Feed 1 performing slightly better than existing Feed 2. Design alterations or new feed designs were proposed that enhance the performance of the feeds tested. The new designs were a single ring Chaparral style feed and a three ring Chaparral style feed, both performing equally well as substitutes. A feed support was also designed that works within the requirements of both the dish and the feed. Calculatio_ns for antenna performance were also done for operations within the S, C, and Ku Bands. Accepted by: Acknowledgements The author is thankful to the Space Science Center of Morehead State University, notably Dr. Benjamin Malphrus, Mr. JeffKruth, and Mr. Michael Combs. Without previous construction and testing of the 24 ft parabolic dish, this thesis would not have come into fruition. Hard work, continuous support, and belief in a single student's abilities supplied the author the opportunities granted as an undergraduate and continue as a graduate student. Many thanks to the Applied Engineering Department of Morehead State University, notably Dr. Ahmad Zargari and Dr. Hans Chapman. With their support, guidance, and encouragement, this thesis was able to build upon the author's previous success and further his admiration and knowledge of his field of study. Thanks to Dr. Capp Y ess for his support and critiquing of the thesis towards completion as well as serving on the thesis committee. The author must especially thank his parents, Herman and Virgie Shelley, and his brother, Nicholas Shelley, for the support provided beneath a watchful eye, providing brightness from obscurity. TABLE OF CONTENTS CHAPTER I: INTRODUCTION .............................................................................. 1 INTRODUCTION •..•..•.....•...........................................................•.....•..•..................•..... 1 GENERAL AREA OF CONCERN •...............................•..•.••..••..•.••.•...•...............•..•.•........ 1 STATEMENT OF THE PROBLEM, •.•..................................•...•..••.••.•..••.•..................•..•.•.. 3 SIGNIFICANCE OF THE STUDY .•..••..•........................................•..•.••....•..•..•.••..•........... 4 RESEARCH OBJECTIVES ...•...•..•..••.••.•...............................................•.••.••.•.••.••........... 4 ASSUMPTIONS ••.•..•..•.••..•..•..••..•..............................................................•.•..•.••.•....•.... 5 LIMITATIONS ..•.••..•..•.••..•..•.....•............•.....................•......•..•......•............................... 5 DEFINITION OF TERMS ............................................................................................... 5 CHAPTER II: REVIEW OF LITERATURE .......................................................... 9 BACKGROUND •..•....••.•..•..••.••..•...•..•.•...•..•..••.•..••........•...................................•....•..•.•.. 9 21 METER SPACE TRACKING ANTENNA .•..•..•..•..••..•..•..•..••.••.••..•..•..•.••.••....••••.•..•..•.•.. 9 7.3 M/24 FT ANTENNA DISH ..................•........•..••.••..•..•..••.••..•..•..•..•..•.••....••.•.•..•. : ..• 15 L-BAND RADIO ASTRONOMY·················································································· 16 FEED DESIGN •.••.•..•..•..••..•..•..••....•..•......•..•..•..•...•.••..••.•..••..•..•..•..•..•..•.••.••.•..•....•....•. 17 CHAPTER ill: l\IBTHODOLOGY ........................................................................ 21 RESTATEMENT OF THE PROBLEM ..•..•..•.........•........•..••.............................•..•.•..•.•..•.• 21 RESTATEMENT OF OBJECTIVES .......................................•.........•.......•.....•.•.............. 21 DISH GEOMETRY & PERFORMANCE CALCULATIONS ..•..•..•......•....•.....•....••.•..•..•....•. 21 ANTENNA TESTING .................................................................................................. 26 VSWR Testing...................................................................................................... 26 Gain Measurement & Illumination Function ..................................................... 30 Anechoic Chamber .............................................................................................. 31 FEED DESIGN ........................................................................................................... 32 Phase and Phase Center ..................................................................................... 32 FEED MOUNT ........................................................................................................... 33 CHAPTER IV: FINDINGS AND ANALYSIS ....................................................... 35 DISH GEOMETRY & PERFORMANCE ANALYSIS ........................................................ 35 GAIN MEASUREMENT .............................................................................................. 44 ILLUMINATION FUNCTION ........................................................................................ 44 COMPARISON & ANALYSIS OF ANTENNA FEEDS ...................................................... 53 FEED DESIGN ANALYSIS .......................................................................................... 58 FEED MOUNT ANALYSIS .......................................................................................... 65 CHAPTER V: SUMMARY, CONCLUSION, & RECOMMENDATIONS ....... 73 SUMMARY ................................................................................................................ 73 CONCLUSION ............................................................................................................ 74 RECOMMENDATIONS ................................................................................................ 75 REFERENCES .......................................................................................................... 76 APPEND IX A ............................................................................................................ 79 APPENDIX B ............................................................................................................ 86 List of Figures Figure 2.1: 21 M STA ........................................................................... 10 Figure 2.2: Taurus A Scan................................................................... 13 Figure 2.3: Cassiopeia A Map .................................................................. 14 Figure 3 .1: Complete Antenna Test Structure ............................................. 27 Figure 4.1: Radiation Pattern of First Antenna at 1.3 GHz .............................. 47 Figure 4.2: Radiation Pattern of First Antenna at 1.421 GHz ........................... 47 Figure 4.3: Radiation Pattern of First Antenna at 1.648 GHz ........................... 48 Figure 4.4: Radiation Patterns of First Antenna Combined .............................. 48 Figure 4.5: Radiation Pattern of Second Antenna at 1.3 GHz ........................... 51 Figure 4.6: Radiation Pattern of Second Antenna at 1.421 GHz ........................ 51 Figure 4.7: Radiation Pattern of Second Antenna at 1.648 GHz ........................ 52 Figure 4.8: Radiation Patterns of Second Antenna Combined ........................... 52 Figure 4.9: Charted Comparison ofFeeds at 67.5 degrees ................................... 56 Figure 4.10: Feed Design 1 (Trimetric View) ................................................. 61 Figure 4.11: Feed Design I (Side View) ....................................................... 61 Figure 4.12: Feed Design i (Trimetric View) ................................................. 62 Figure 4.13: Feed Design 2 (Side View) ....................................................... 62 Figure 4.14: Feed Design 1 Schematics ........................................................ 63 Figure 4.15: Feed Design 2 Schematics ........................................................ 64 Figure 4.16: DC Motor Drive with Optical Encoders ..................................... 66 Figure 4.17: Feed Support Structure (Full View) .......................................... 67 Figure 4.18: Feed Support Antenna Connection View (Face View) .................... 67 Figure 4.19: Feed Support Antenna Connection View (Rear View) .................... 67 Figure 4.20: Feed Support Structure with Feed Design I (Full View)