Author Biographies ix
Acknowledgments xi
1 A Perspective of Antennas for 5G and 6G 1
1.1 5G Requirements of Antenna Arrays 1
1.1.1 Array Characteristics 1
1.1.2 Frequency Bands 3
1.1.3 Component Integration and Antennas-in-Package (AiP) 3
1.2 6G and Its Antenna Requirements 5
1.3 From Digital to Hybrid Multiple Beamforming 6
1.3.1 Digital Beamforming 7
1.3.2 Hybrid Beamforming 8
1.4 Analog Multiple Beamforming 11
1.4.1 Butler Matrix 12
1.4.2 Luneburg Lenses 13
1.5 Millimeter-Wave Antennas 14
1.6 THz Antennas 15
1.7 Lens Antennas 16
1.8 SIMO and MIMO Multi-Beam Antennas 18
1.9 In-Band Full Duplex Antennas 19
1.10 Conclusions 20
References 20
2 Millimeter-Wave Beamforming Networks 23
2.1 Circuit-Type BFNs: SIW-Based Butler and Nolen Matrixes 23
2.1.1 Butler Matrix for One-Dimensional Multi-Beam Arrays 23
2.1.2 Butler Matrix for a 1-D Multi-Beam Array with Low Sidelobes 27
2.1.3 Butler Matrix for 2-D Multi-Beam Arrays 29
2.1.4 Nolen Matrix 34
2.2 Quasi Optical BFNs: Rotman Lens and Reflectors 36
2.2.1 Rotman Lens 36
2.2.2 Reflectors 40
2.2.2.1 Single Reflectors 41
2.2.2.2 Dual Reflectors 44
2.3 Conclusions 45
References 46
3 Decoupling Methods for Antenna Arrays 49
3.1 Electromagnetic Bandgap Structures 49
3.2 Defected Ground Structures 51
3.3 Neutralization Lines 54
3.4 Array-Antenna Decoupling Surfaces 58
3.5 Metamaterial Structures 62
3.6 Parasitic Resonators 70
3.7 Polarization Decoupling 81
3.8 Conclusions 83
References 84
4 De-scattering Methods for Coexistent Antenna Arrays 89
4.1 De-scattering vs. Decoupling in Coexistent Antenna Arrays 89
4.2 Mantle Cloak De-scattering 92
4.3 Lumped-Choke De-scattering 95
4.4 Distributed-Choke De-scattering 113
4.5 Mitigating the Effect of HB Antennas on LB Antennas 130
4.6 Conclusions 132
References 132
5 Differential-Fed Antenna Arrays 135
5.1 Differential Systems 135
5.2 Differential-Fed Antenna Elements 137
5.2.1 Linearly Polarized Differential Antennas 138
5.2.2 Circularly Polarized Differential Antennas 143
5.3 Differential-Fed Antenna Arrays 146
5.3.1 Balanced Power Dividers 147
5.3.2 Differential-Fed Antenna Arrays Employing Balanced Power Dividers 151
5.4 Differential-Fed Multi-Beam Antennas 161
5.5 Conclusions 165
References 166
6 Conformal Transmitarrays 169
6.1 Conformal Transmitarray Challenges 169
6.1.1 Ultrathin Element with High Transmission Efficiency 169
6.1.2 Beam Scanning and Multi-Beam Operation 171
6.2 Conformal Transmitarrays Employing Triple-Layer Elements 171
6.2.1 Element Designs 171
6.2.2 Conformal Transmitarray Design 173
6.3 Beam Scanning Conformal Transmitarrays 179
6.3.1 Scanning Mechanism 180
6.3.2 Experimental Results 182
6.3.3 Limits of the Beam Scanning Range 183
6.4 Conformal Transmitarray Employing Ultrathin Dual-Layer Huygens Elements 185
6.4.1 Huygens Surface Theory 186
6.4.2 Ultrathin Dual-Layer Huygens Elements 189
6.4.3 Conformal Transmitarray Design 194
6.5 Elliptically Conformal Multi-Beam Transmitarray with Wide-Angle Scanning Ability 198
6.5.1 Multi-Beam Transmitarray Design 200
6.5.2 Concept Verification Through Simulation 204
6.6 Conclusions 209
References 209
7 Frequency-Independent Beam Scanning Leaky-Wave Antennas 213
7.1 Reconfigurable Fabry–Perot (FP) LWA 213
7.1.1 Analysis of 1-D Fabry–Perot LWA 214
7.1.2 Effect of Cj on the Leaky-Mode Dispersion Curves 216
7.1.3 Optimization of the FP Cavity Height 218
7.1.4 Antenna Prototype and Measured Results 219
7.2 Period-Reconfigurable SIW-Based LWA 222
7.2.1 Antenna Configuration and Element Design 223
7.2.2 Suppression of Higher-Order Harmonics 226
7.2.3 Element Activation States and Scanning Properties 230
7.2.4 Results and Discussion 233
7.2.4.1 Element Pattern and Antenna Prototype 233
7.2.4.2 Radiation Patterns and S-Parameters 236
7.3 Reconfigurable Composite Right/Left-Handed LWA 240
7.3.1 Parametric Analysis 242
7.3.2 Initial Frequency-Scanning CRLH LWA 245
7.3.3 Reconfigurable Fixed-Frequency Scanning CRLH LWA 247
7.3.3.1 Antenna Configuration 247
7.3.3.2 DC Biasing Strategy 249
7.3.3.3 Simulation Results 250
7.3.3.4 Measured Results 252
7.3.3.5 Discussions 254
7.4 Two-Dimensional Multi-Beam LWA 256
7.4.1 Antenna Design 257
7.4.1.1 Horn BFN 257
7.4.1.2 Phase-Compensation Method 258
7.4.1.3 Phase Shifter Based on Phase Inverter 259
7.4.1.4 Fixed-Frequency Beam Scanning Leaky-Wave Antenna 260
7.4.2 Performance and Discussion 264
7.5 Conclusions 267
References 270
8 Beam Pattern Synthesis of Analog Arrays 275
8.1 Thinned Antenna Arrays 275
8.1.1 Modified Iterative FFT 276
8.1.2 Examples of Thinned Arrays 279
8.2 Arrays with Rotated Elements 283
8.2.1 The Pattern of an Element-Rotated Array 283
8.2.2 Vectorial Shaped Pattern Synthesis Using Joint Rotation/Phase Optimization 285
8.2.3 The Algorithm 287
8.2.4 Examples of Pattern Synthesis Based on Element Rotation and Phase 288
8.2.4.1 Flat-Top Pattern Synthesis with a Rotated U-Slot Loaded Microstrip Antenna Array 288
8.2.4.2 Circular Flat-Top Pattern Synthesis for a Planar Array with Rotated Cavity-Backed Patch Antennas 290
8.3 Arrays with Tracking Abilities Employing Sum and Difference Patterns 294
8.3.1 Nonuniformly Spaced Dipole-Rotated Linear Array 295
8.3.2 PSO-Based Element Rotation and Position Optimization 297
8.3.3 Examples 298
8.3.3.1 Synthesis of a 56-Element Sparse Linear Dipole Array 298
8.3.3.2 Synthesizing Sum and Difference Patterns with Multi-Region SLL and XPL Constraints 300
8.4 Synthesis of SIMO Arrays 301
8.4.1 Analog Dual-Beam Antenna Arrays with Linear Phase Distribution 302
8.4.2 Phase-Only Optimization of Multi-Beam Arrays 303
8.4.3 The Algorithm 306
8.4.4 Simulation Examples 306
8.5 Conclusions 308
References 308
Index 311
