Handbook of Reflector Antennas and Feed Systems Volume I Theory and Design of Reflectors Satish K. Sharma Sudhakar Rao Lotfollah Shafai
Preface Acknowledgments ix x Introduction 1 1.1 Introduction 1 1.2 Reflector Antenna Basics 2 1.3 Feed Sources for Reflector Antennas 6 1.4 Analysis of Reflector Antennas 6 1.5 Advanced Reflector Antenna Configurations 7 1.6 Important Fundamental Parameters 8 1.7 Organization of the Book 9 References 10 Numerical Techniques for Reflectors 13 2.1 Introduction 13 2.2 Reflector Geometry Using a Surface of Revolution 14 2.2.1 Rays in a Parabola 14 2.3 Geometric Optics 15 2.4 Feed Modeling 16 2.4.1 Analytical Feed Models 16 2.4.2 Spherical Wave Expansion Feed 18 2.4.3 Currents Expansion Feed 19 2.5 Reflector Analysis Methods 19 2.5.1 Aperture Method 19 2.5.2 PO Analysis 23 2.5.3 GO/GTD Analysis 29 2.5.4 Shooting and Bouncing Analysis 31 2.5.5 Moment Method Reflector Analysis 32 2.6 Reflector Size Limitation 38 2.7 Struts 40 2.7.1 Polygon Struts 43 2.7.2 Metal Space Frame Radome 47 2.8 Dual Reflector 51 2.9 Dual Grid Reflector 60 v
vi Contents 2.10 Reflector Coupling 63 Acknowledgments 64 References 64 Classical Reflector Antennas: Design Guidelines and Performance Characteristics 67 3.1 Introduction 67 3.2 General Conic-Section-Generated Reflectors 68 3.2.1 Conic Sections 68 3.2.2 Conic-Section-Generated Reflectors 69 3.3 Parabolic Reflectors 70 3.3.1 Geometrical Parameters 71 3.3.2 Feed Patterns 72 3.3.3 Edge Tapers and Feed Tapers 77 3.3.4 Reflector Pattern Characteristics 78 3.3.5 Off-Focus Feeds 83 3.3.6 Beam Squint 94 3.3.7 Symmetric Versus Offset Parabolic Configurations 96 3.4 Folded-Optics Reflectors 97 3.4.1 Cassegrain and Gregorian Reflectors 98 3.4.2 The Equivalent Paraboloid 101 3.4.3 Feed and Subreflector Blockage 102 3.4.4 Sidelobes 102 3.4.5 Efficiency Factors 105 3.4.6 Offset Dual-Reflector Systems 106 3.4.7 Antenna Noise Temperature 108 3.4.8 Reflector Shaping 113 3.5 Other Classical Reflectors 113 3.5.1 Corner Reflectors 113 3.5.2 Spherical Reflector 115 3.5.3 Reflectors with Parabolic Arc 117 References 119 Reflector Antennas with Adaptive Apertures 125 4.1 Introduction 125 4.2 Theory and Overview 126 4.3 Reflector Antenna Performance with Individual TEll5 TM01, and TE2i Modes of a Circular Waveguide Feed 128 4.4 Reflector Antenna Performance with Dual Mode Feed Horns 130 4.4.1 Symmetric Reflector with TEj + 1 TM01 Mode Feed Horn 131 4.4.2 Offset Reflector with TEn + TM01 Mode Feed Horn 135 4.4.3 Symmetric Reflector with TEn + TE21 Mode Feed Horn 139 4.4.4 Offset Reflector with TEn + TE21 Mode Feed Horn 143 4.5 Symmetric Reflector with a Tri-Mode Circular Waveguide Feed 145
vii 4.5.1 Practical Triple-Mode Feed Horn 149 4.5.2 Symmetric Reflector Antenna Performance with the Tri-Mode Feed 154 4.6 Multiple Phase Center Offset Reflectors with TMn + TM21 Microstrip Patch Feeds 155 References 160 Reflector Shaping 163 5.1 Introduction 163 5.2 Reflector Shaping Considerations 164 5.3 Reflector Shaping Techniques 166 5.4 Frequency Re-Use 168 5.5 Reflector Shaping Using Synthesis Techniques 169 5.6 Shaping Limitations and Manufacturing Aspects 176 References 178 CHAPTER 6 Bifocal and Bicollimated Dual Reflector Antennas 6.1 Introduction 6.2 Bifocal Dual Reflector Antennas 6.2.1 Cassegrain Configuration 6.2.2 Gregorian Configuration 6.3 Multifocal Dual Reflector Antennas 6.4 Bicollimated Dual Reflector Antenna 6.4.1 Design Procedure 6.4.2 Polynomial Approximation 6.4.3 Equivalent Gregorian Confocal Reflector 6.4.4 Limiting Gregorian Confocal Reflector 6.4.5 Phase Error Analysis 6.4.6 Design Example 6.5 Bifocal and Bicollimated Dual Reflector Antenna Applications Acknowledgments Appendix A: Determination of the Parameters P, L, a, and d Appendix B: Three-Dimensional Ray Tracing Procedure References 181 181 182 182 193 195 197 199 202 202 203 203 204 207 212 212 213 216 CHAPTER 7 Advanced Reflector Antennas 219 7.1 Introduction 219 7.2 Confocal Antenna System 221 7.3 Side-Fed and Front-Fed Offset Cassegrain Antenna Systems 225 7.4 Nonfocused Reflector Antenna 229 7.5 Reconfigurable Reflector Antennas 234 7.6 ADE Reflector Antennas 241 References 245
CHAPTER 8 Reflectarray Antennas 247 8.1 Introduction 247 8.2 General Design Guidelines 249 8.3 Aperture Efficiency of Reflectarray and Comparison with Conventional Parabolic Reflector 253 8.3.1 Illumination Efficiency 253 8.3.2 Spillover Efficiency 254 8.3.3. Polarization Efficiency 256 8.3.4 Phase Efficiency 256 8.3.5 Blockage Efficiency 257 8.3.6 Dielectric and Conductor Loss 258 8.4 Contribution of Scattering from Constituent Components of a Reflectarray to Its Near-Field and Far-Field Operation 259 8.4 Different Types of Reflectarray Cell Elements 264 8.5 Different Types of Reflectarray Antennas 274 Acknowledgments 284 References 289 About the Editors 295 List of Contributors 298 Index 299