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Performance of Reflector Antennas by Employing PERFORMANCE OF REFLECTOR ANTENNAS BY EMPLOYING TRIPLE MODE FEEDHORN AND A FREQUENCY RECONFIGURABLE SPIRAL LOADED PLANAR DIPOLE ANTENNA _______________ A Thesis Presented to the Faculty of San Diego State University _______________ In Partial Fulfillment of the Requirements for the Degree Master of Science in Electrical Engineering _______________ by Mukund Ranga Thyagarajan Fall 2012 iii Copyright © 2012 by Mukund Ranga Thyagarajan All Rights Reserved iv ABSTRACT OF THE THESIS Performance of Reflector Antennas by Employing Triple Mode Feedhorn and a Frequency Reconfigurable Spiral Loaded Planar Dipole Antenna by Mukund Ranga Thyagarajan Master of Science in Electrical Engineering San Diego State University, 2012 This thesis focuses on two aspects: triple mode feedhorn as a feed source to reflector antennas and a compact spiral loaded planar dipole antenna with frequency reconfiguration. For the first aspect, parabolic symmetric and offset reflector antennas are adaptively illuminated using a novel triple (TE11+ TM01+ TE21) modes feedhorn with different mode combinations and impedance and radiation performances are presented. The combination of the radiating modes in a feedhorn with proper amplitude and fixed phase values helps in electronically pointing the main beam of the radiating patterns such as obtained in a beam steering antenna with limited beam scan range. This type of radiation performance virtually creates a displaced phase center location for the feedhorn, which consequently, adaptively illuminates the reflector antenna surface. Impedance matching bandwidths are preserved for both reflector antennas similar to the case of feedhorn alone. The co-polarization gain and peak cross-polarization levels are far better with the offset reflector antenna than the symmetric reflector antenna. Such reflector antennas find applications in radars. The simulation and analysis have been performed using EMSS's FEKO tool which is a Method of Moments (MOM) based Maxwell equation solver. The other design performed is a reconfigurable spiral loaded planar dipole antenna design which is frequency reconfigurable in the 0.76 GHz, 1.47 GHz and 2.2 GHz bands by employing PIN diodes as switching elements. This design is implemented to show the compactness achieved using spiraling in a planar dipole antenna. This antenna was fabricated and tested with nearly matching results. It can be used in wireless communication applications and for many other devices which operate over these frequency bands. v TABLE OF CONTENTS PAGE ABSTRACT ............................................................................................................................. iv LIST OF TABLES ................................................................................................................. viii LIST OF FIGURES ...................................................................................................................x ACKNOWLEDGEMENTS ................................................................................................... xiv CHAPTER 1 INTRODUCTION .........................................................................................................1 1.1 Feedhorns ...........................................................................................................1 1.1.1 Pyramidal Horn .........................................................................................4 1.1.2 Conical Horn .............................................................................................4 1.1.3 Corrugated Horn .......................................................................................6 1.2 Reflector Antenna and Types .............................................................................6 1.2.1 Plane Reflector ..........................................................................................9 1.2.2. Corner Reflector.....................................................................................10 1.2.3 Parabolic Reflector ..................................................................................10 1.2.3.1 Front Fed Parabolic Reflector ........................................................12 1.2.3.2 Offset Reflector Antenna ...............................................................12 1.2.3.3 Cassegrain Reflector Antenna........................................................15 1.3 Reconfigurability in Spiral Loaded Planar Dipole Antenna ............................15 1.4 Simulation Techniques and Experimental Verification Methods ....................17 1.5 Organization of Thesis .....................................................................................18 2 DOMINANT MODE FEEDHORN REFLECTOR SIMULATIONS USING GRASP AND FEKO ...................................................................................................19 2.1 Introduction ......................................................................................................19 2.2 TICRA Grasp Simulations ...............................................................................19 2.3 Design and Analysis of A Cylindrical Feedhorn .............................................23 2.4 Conical Feedhorn Symmetrically Feeding A Large Reflector ........................26 2.5 Conclusion .......................................................................................................31 vi 3 TRIPLE MODE FEEDHORN PERFORMANCE AND PHASE CENTER DETERMINATION ....................................................................................................33 3.1 Introduction ......................................................................................................33 3.2 Design Methodology ........................................................................................34 3.3 Simulated Results and Performance ................................................................35 3.3.1 Individual Mode Analysis of the Triple Mode Feedhorn .......................37 3.3.2 Dual Mode Analysis for Various Mode Combinations ..........................41 3.3.3 Triple Mode Analysis for Various Mode Combinations ........................42 3.4 Phase Center Determination ............................................................................44 3.5 Wilkinson Unequal 1:5 Power Divider Design and Results ............................50 3.6 Conclusion .......................................................................................................56 4 SYMMETRIC REFLECTOR ANTENNA FED BY TRIPLE MODE FEEDHORN ................................................................................................................62 4.1 Introduction to Reflector Antennas ..................................................................62 4.2 Design and Simulated Results .........................................................................66 4.2.1 Single Mode Analysis .............................................................................67 4.2.2 Dual Mode Analysis ...............................................................................68 4.2.3 Triple Mode Analysis .............................................................................72 4.3 Analysis on Amplitude Variation on Triple Mode Combination ....................74 4.4 Conclusion .......................................................................................................77 5 OFFSET REFLECTOR ANTENNA FED BY TRIPLE MODE FEEDHORN ..........79 5.1 Introduction ......................................................................................................79 5.2 Design and Simulated Results .........................................................................80 5.2.1 Single Mode Analysis .............................................................................81 5.2.2 Dual Mode Analysis ...............................................................................82 5.2.3 Triple Mode Combination Analysis........................................................86 5.3 Conclusion .......................................................................................................88 6 FREQUENCY RECONFIGURABLE SPIRAL LOADED PLANAR DIPOLE ........95 6.1 Introduction ......................................................................................................95 6.2 Planar vs. Spiral Dipole Antenna .....................................................................98 6.3 Frequency Reconfigurable Spiral Loaded Planar Dipole Antenna ................103 6.3 Conclusion .....................................................................................................110 7 CONCLUSIONS AND FUTURE STUDY ...............................................................115 vii REFERENCES ......................................................................................................................117 viii LIST OF TABLES PAGE Table 2.1: Fundamental Mode Circular Waveguide Analysis for Variable f/D ......................20 Table 2.2: Gaussian Beam Mode Analysis for Variable f/D ...................................................20 Table 2.3: The Co-Polarization Gain Values Vs Frequency for Conical Feedhorn. ...............28 Table 2.4: The Co-Polarization Gain Values Vs Frequency for Conical Feedhorn- Reflector Configuration. ..............................................................................................31 Table 3.1. Peak Co- and Cross-Polarization Gain Values at 7.73 GHz for Triple Mode Feedhorn with Equal Amplitude ..................................................................................41
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