Modern Lens Antennas for Communications Engineering

Preface ix Acknowledgments xi 1 INTRODUCTION 1 John Thornton and Kao-Cheng Huang 1.1 Lens Antennas: An Overview 2 1.1.1 The Microwave Lens 2 1.1.2 Advantages of Lens Antennas 4 1.1.3 Materials for Lenses 5 1.1.4 Synthesis 6 1.2 Feeds for Lens Antennas 8 1.2.1 Microstrip Feeds 8 1.2.2 Horn Feeds 9 1.3 Luneburg and Spherical Lenses 10 1.4 Quasi Optics and Lens Antennas 14 1.5 Lens Antenna Design 18 1.6 Metamaterial Lens 26 1.7 Planar Lens or Phase-Shifting Surface 30 1.7.1 Refl ect Array 31 1.7.2 Planar Lens or Lens Array 33 1.8 Applications 36 1.9 Antenna Measurements 37 1.9.1 Radiation Pattern Measurement 37 1.9.2 Gain Measurement 38 1.9.3 Polarization Measurement 38 1.9.4 Anechoic Chambers and Ranges 38 2 REVIEW OF ELECTROMAGNETIC WAVES 49 Kao-Cheng Huang 2.1 Maxwell's Equations 49 2.1.1 Boundary Conditions 53 2.1.2 Equivalence Theorem 55 2.2 Antenna Parameters 56 2.2.1 Beam Solid Angle and Antenna Temperature 56 2.2.2 Directivity and Gain 58 2.2.3 Antenna Beamwidth 60 2.2.4 Aperture of a Lens 62 2.2.5 Phase Center 63 2.3 Polarization 64 2.4 Wave Propagation in Metamaterials 71 3 POLYROD ANTENNAS 77 Kao-Cheng Huang 3.1 Polyrods as Resonators 78 3.2 The Polyrod as a Radiator 83 3.2.1 Tapered Polyrod Antenna 85 3.3 Patch-Fed Circular Polyrod 90 3.4 Array of Polyrods 97 3.5 Multibeam Polyrod Array 105 4 MILLIMETER WAVE LENS ANTENNAS 113 Kao-Cheng Huang 4.1 Millimeter Wave Characteristics 114 4.1.1 Millimeter Wave Loss Factors 114 4.1.2 Ray-Tracing Propagation 117 4.2 Millimeter Wave Substrate Lens for Imaging 121 4.3 Millimeter Wave and Submillimeter Wave Lens 126 4.3.1 Extended Hemispherical Lens 128 4.3.2 Off-Axis Extended Hemispherical Lens 133 4.3.3 Submillimeter Wave Lens Antennas for Communications 136 4.4 Analysis of Millimeter Wave Spherical Lens 139 4.5 Waveguide-Fed Millimeter Wave Integrated Lens 141 5 LENS ANTENNAS FOR COMMUNICATIONS FROM HIGH-ALTITUDE PLATFORMS 147 John Thornton 5.1 Introduction 147 5.2 The High-Altitude Platform Concept 148 5.2.1 Spectrum Reuse Using HAPs 150 5.2.2 Example Results: Cell Power and Interference 155 5.3 Advantages of Lenses over Reflector Antennas 159 5.3.1 Reflectors 160 5.3.2 Lenses 161 5.3.3 Commercial Lens Antennas 162 5.4 Development of a Shaped Beam Low-Sidelobe Lens Antenna with Asymmetric Pattern 164 5.4.1 Primary Feed 165 5.4.2 Symmetric 5° Beamwidth Antenna 166 5.4.3 Asymmetric Beam 166 5.4.4 Measurements 174 5.5 Lens Antenna Payload Model 177 5.6 Multifeed Lens 178 5.7 Multiple Beam Spherical Lens Antennas for HAP Payload 181 6 SPHERICAL LENS ANTENNAS 187 John Thornton 6.1 Introduction 187 6.2 Spherical Lens Overview 192 6.3 Analytical Methods 195 6.3.1 Ray Tracing 195 6.3.2 SWE 197 6.3.3 Computational Method and Results 202 6.3.4 Generic Feed Pattern 206 6.3.5 Commercial Solvers 208 6.4 Spherical Lens Materials and Fabrication Methods 210 6.4.1 Machined Polymers 210 6.4.2 Molding 212 6.4.3 Polymer Foams 212 6.4.4 PU Dielectric Loss 214 6.4.5 Artifi cial Dielectrics 215 6.5 Revisiting the Constant-Index Lens 215 6.5.1 A Practical, Patch-Fed Hemispherical Constant-Index Lens 219 6.5.2 Off-Axis Array-Fed Spherical Lens 219 6.6 Cross-Polarization Properties of Spherical Lenses 221 7 HEMISPHERICAL LENS-REFLECTOR SCANNING ANTENNAS 225 John Thornton 7.1 Introduction 225 7.2 Candidate Scanning Antenna Technologies 226 7.3 Spherical and Hemispherical Lens Antenna 228 7.4 Hemispherical Lens Prototype 229 7.5 Evolution of a Two-Layer Stepped-Index Polymer Lens 232 7.6 A Hemispherical Lens-Reflector Antenna for Satellite Communications 238 7.6.1 Requirements 239 7.6.2 Lens Analysis 240 7.6.3 Three-Layer Lens Geometry 240 7.6.4 Lens Fabrication and Performance 243 7.6.5 Mechanical Tracking System 245 7.6.6 Ground Plane Effects 249 7.6.7 Aperture Blockage in Scanning Lens Reflector 251 7.7 A Low-Index Lens Reflector for Aircraft Communications (Contribution by D. Gray) 252 About the Authors 267 Index 268