ULTRA-WIDEBAND ANTENNAS AND PROPAGATION FOR COMMUNICATIONS, RADAR AND IMAGING Edited by Ben Allen University of Oxford, UK Mischa Dohler France Telecom R&D, France Ernest E. Okon BAE Systems Advanced Technology Centre, UK Wasim Q. Malik University of Oxford, UK Anthony K. Brown University of Manchester, UK David J. Edwards University of Oxford, UK 3ICENTENNIAL iicentennial John Wiley & Sons, Ltd
Edltors Prime Contributors Preface Acknowledgments Abbreviations & Acronyms xv xvii xxi xxvii xxix 1 Introduction to UWB Signals and Systems 1 Andreas F. Molisch 1.1 HistoryofUWB 1 1.2 Motivation 3 1.2.1 Large Absolute Bandwidth 3 1.2.2 Large Relative Bandwidth 5 1.3 UWB Signals and Systems 6 1.3.1 Impulse Radio 6 1.3.2 DS-CDMA 8 1.3.3 OFDM 9 1.3.4 Frequency Hopping 10 1.3.5 RADAR 11 1.3.6 Geolocation 11 1.4 Frequency Regulation 12 1.5 Applications, Operating Scenanos and Standardisation 13 1.6 System Outlook 15 References 16 Part I Fundamentals 19 Introduction to Part I 21 Wasim Q. Malik and David J. Edwards 2 Fundamental Eleetromagnetic Theory 25 Mischa Dohler 2.1 Introduction 25 2.2 Maxwell's Equations 25 2.2.1 Differential Formulation 25 2.2.2 Interpretation 26 2.2.3 Key to Antennas and Propagation 27
vi Contents 2.2.4 Solving Maxwell's Equations 28 2.2.5 Harmonie Representation 29 2.3 Resulting Principles 30 References 30 3 Basic Antenna Elements 31 Mischa Dohler 3.1 Introduction 31 3.2 Hertzian Dipole 31 3.2.1 Far-Field - Fraunhofer Region 33 3.2.2 Near-Field - Fresnel Region 33 3.3 Antenna Parameters and Terminology 34 3.3.1 Polarisation 34 3.3.2 Power Density 35 3.3.3 Radiated Power 36 3.3.4 Radiation Resistance 37 3.3.5 Antenna Impedance 37 3.3.6 Equivalent Circuit 37 3.3.7 Antenna Matching 38 3.3.8 Effective Length and Area 38 3.3.9 Friis' Transmission Formula 39 3.3.10 Radiation Intensity 39 3.3.11 Radiation Pattern 39 3.3.12 (Antenna) Bandwidth 41 3.3.13 Directive Gain, Directivity, Power Gain 41 3.3.14 Radiation Efficiency 42 3.4 Basic Antenna Elements 42 3.4.1 Finite-Length Dipole 42 3.4.2 Monopole 44 3.4.3 Printed Antennas 45 3.4.4 Wideband and Frequency-Independent Elements 45 References 47 4 Antenna Arrays 49 Ernest E. Okon 4.1 Introduction 49 4.2 Point Sources 49 4.2.1 Point Sources with Equal Amplitude and Phase 50 4.2.2 Point Sources with Equal Amplitude and 180 Degrees Phase Difference 53 4.2.3 Point Sources of Unequal Amplitude and Arbitrary Phase Difference 53 4.3 The Principle of Pattern Multiplication 55 4.4 Linear Arrays of n Elements 56 4.5 Linear Broadside Arrays with Nonuniform Amplitude Distributions 58 4.5.1 The Binomial Distribution 59 4.5.2 The Dolph-Tschebyscheff Distribution 59 4.6 Planar Arrays 62 4.6.1 Rectangular Arrays 62 4.6.2 Circular Arrays 63
Vll 4.7 Design Considerations 65 4.7.1 Mutual Coupling 65 4.7.2 Array Gain 65 4.8 Summary 66 References 66 5 Beamforming 67 Ben Allen 5.1 Introduction 67 5.7.7 Historical Aspects 67 5.7.2 Concept ofspatial Signal Processing 68 5.2 Antenna Arrays 69 5.2.7 Linear Array 70 5.2.2 Circular Array 71 5.2.3 Planar Array 72 5.2.4 Conformal Arrays 72 5.3 Adaptive Array Systems 73 5.3.7 Spatial Filtering 73 5.3.2 Adaptive Antenna Arrays 74 5.5'..? Mutual Coupling and Correlation 74 5.4 Beamforming 75 5.4.1 Adaptive Antenna Technology 75 5.4.2 Beam Steering 78 5.4.5" Gräting Lobes 83 5.4.4 Amplitude Weights 84 5.4.5 Window Functions 85 5.5 Summary 86 References 87 6 Antenna Diversity Techniques 89 Junsheng Liu, Wasim Q. Malik, David J. Edwards and Mohammad Ghavami 6.1 Introduction 89 6.2 A Review of Fading 89 6.2.7 Signal Fading 90 6.2.2 Channel Distribution 91 6.3 Receive Diversity 93 6.3.1 Single Branch without Diversity 93 6.3.2 General Combining Schemes for Receive Diversity 95 6.3.3 Maximum Ratio Combining 96 6.3.4 Equal Gain Combining 98 6.3.5 Selection Combining and Switched Diversity 99 6.3.6 Fading Correlation 99 6.4 Transmit Diversity 100 6.4.7 Channel Unknown to the Transmitter 101 6.4.2 Channel Known to the Transmitter 102 6.5 MIMO Diversity Systems 102 References 103
viii Contents Part II Antennas for UWB Communications 105 Introduction to Part II 107 Ernest E. Okon 7 TheoryofUWB Antenna Elements 111 Xiaodong Chen 7.1 Introduction 111 7.2 Mechanism of UWB Monopole Antennas 112 7.2.1 Basic Features of a CPW-Fed Disc Monopole 112 7.2.2 Design Analysis 118 7.2.3 Operating Principle of UWB Monopole Antennas 120 7.3 Planar UWB Monopole Antennas 121 7.3.1 CPW-Fed Circular Disc Monopole 121 7.3.2 Microstrip Line Fed Circular Disc Monopole 125 7.3.3 Other Shaped Disc Monopoles 129 7.4 Planar UWB Slot Antennas 132 7.4.7 Microstrip/CPW Feed Slot Antenna Designs 132 7.4.2 Performance of Elliptical/Circular Slot Antennas 134 7.4.3 Design Analysis 138 7.5 Time-Domain Characteristics of Monopoles 140 7.5.1 Time-Domain Performance of Disc Monopoles 142 7.5.2 Time-Domain Performance of Slot Antenna 143 7.6 Summary 144 Acknowledgements 144 References 144 8 Antenna Elements for Impulse Radio 147 Zhi Ning Chen 8.1 Introduction 147 8.2 UWB Antenna Classification and Design Considerations 148 8.2.1 Classification of UWB Antennas 148 8.2.2 Design Considerations 150 8.3 Omnidirectional and Directional Designs 153 8.3.1 Omnidirectional Roll Antenna 153 8.3.2 Directional Antipodal Vivaldi Antenna 155 8.4 Summary 160 References 161 9 Planar Dipole-like Antennas for Consumer Products 163 Peter Massey 9.1 Introduction 163 9.2 Computer Modelling and Measurement Techniques 164 9.3 Bicone Antennas and the Lossy Transmission Line Model 164 9.4 Planar Dipoles 167 9.4.1 Bowtie Dipoles 167 9.4.2 Elliptical Element Dipoles 171 9.4.3 Fan Element Dipoles 173 9.4.4 Diamond Dipoles 176
ix 9.5 Practical Antennas 178 9.5.1 Printed Elliptical Dipoles 178 9.5.2 Line-Matched Monopoles 185 9.5.3 Vivaldi Antenna 189 9.6 Summary 194 Acknowledgements 195 References 195 10 UWB Antenna Elements for Consumer Electronic Applications 197 Dirk Manteujfel 10.1 Introduction 197 10.2 Numerical Modelling and Extraction of the UWB Characterisation 199 10.2.1 FDTD Modelling 199 10.2.2 UWB Antenna Characterisation by Spatio-Temporal Transfer Functions 201 10.2.3 Calculation oftypical UWB Antenna Measures from the Transfer Function ofthe Antenna 202 10.2.4 Example 204 10.3 Antenna Design and Integration 205 10.3.1 Antenna Element Design and Optimisation 206 10.3.2 Antenna Integration into a DVD Player 208 10.3.3 Antenna Integration into a Mobile Device 211 10.3.4 Conclusion 213 10.4 Propagation Modelling 214 10.5 System Analysis 215 10.6 Conclusions 218 References 220 11 Ultra-wideband Arrays 221 Ernest E. Okon 11.1 Introduction 221 11.2 Linear Arrays 221 11.2.1 Broadside Array 222 11.2.2 End-fire Array 222 11.2.3 End-fire Array with Increased Directivity 224 11.2.4 Scanning Arrays 224 11.3 Null and Maximum Directions for Uniform Arrays 225 11.3.1 Null Directions 225 11.3.2 Maximum Directions 226 11.3.3 Circle Representations 228 11.4 Phased Arrays 230 11.4.1 Element Spacing Required to Avoid Gräting Lobes 231 11.5 Elements for UWB Array Design 232 11.6 Modelling Considerations 234 11.7 Feed Contigurations 234 11.7.1 Active Array 235 11.7.2 Passive Array 235 11.8 Design Considerations 238
11.9 Summary 239 References 240 12 UWB Beamforming 241 Mohammad Ghavami and Kaveh Heidary 12.1 Introduction 241 12.2 Basic Concept 242 12.3 A Simple Delay-line Transmitter Wideband Array 243 12.3.1 Angles of Gräting Lobes 246 12.3.2 Inter-null Beamwidth 248 12.4 UWB Mono-pulse Arrays 249 12.4.1 Problem Formulation 249 12.4.2 Computed Results 251 12.5 Summary 257 References 258 Part III Propagation Measurements and Modelling for UWB Communications 259 Introduction to Part III 261 Mischa Dohler and Ben Allen 13 Analysis of UWB Signal Attenuation Through Typical Building Materials 265 Domenico Porcino 13.1 Introduction 265 13.2 A Brief Overview of Channel Characteristics 267 13.3 The Materials Under Test 270 13.4 Experimental Campaign 272 13.4.1 Equipment Configuration 275 13.4.2 Results 278 13.5 Conclusions 281 References 281 14 Large- and Medium-scale Propagation Modelling 283 Mischa Dohler, Junsheng Liu, R. Michael Buehrer, Swaroop Venkatesh and Ben Allen 14.1 Introduction 283 14.2 Deterministic Models 284 14.2.1 Free-space Pathloss - Excluding the Effect ofantennas 284 14.2.2 Free-space Pathloss - Considering the Effect ofantennas 287 14.2.3 Breakpoint Model 291 14.2.4 Ray-tracing and FDTD Approaches 296 14.3 Statistical-Empirical Models 297 14.3.1 Pathloss Coefficient 297 14.3.2 Shadowing 301 14.4 Standardised Reference Models 303 14.4.1 IEEE 802.15.3a 304 14.4.2 IEEE 802.15.4a 304
XI 14.5 Conclusions 306 References 306 15 Small-scale Ultra-wideband Propagation Modelling 309 Swaroop Venkatesh, R. Michael Buehrer, Junsheng Liu and Mischa Dohler 15.1 Introduction 309 15.2 Small-scale Channel Modelling 310 15.2.1 Statistical Characterisation ofthe Channel Impulse Response 310 15.2.2 Deconvolution Methods and the Clean Algorithm 312 15.2.3 The Saleh-Valenzuela Model 312 15.2.4 Other Temporal Models 316 15.3 Spatial Modelling 321 15.4 IEEE 802.15.3a Standard Model 324 15.5 IEEE 802.15.4a Standard Model 325 15.6 Summary 327 References 327 16 Antenna Design and Propagation Measurements and Modelling for UWB Wireless BAN 331 Yang Hao, Akram Alomainy and Yan Zhao 16.1 Introduction 331 16.2 Propagation Channel Measurements and Characteristics 332 16.2.1 Antenna Element Design Requirements for WBAN 332 16.2.2 Antennas for UWB Wireless BAN Applications 333 16.2.3 On-Body Radio Channel Measurements 335 16.2.4 Propagation Channel Characteristics 338 16.3 WBAN Channel Modelling 345 16.3.1 Radio Channel Modelling Considerations 346 16.3.2 Two-Dimensional On-Body Propagation Channels 349 16.3.3 Three-Dimensional On-Body Propagation Channels 350 16.3.4 Pathloss Modelling 351 16.4 UWB System-Level Modelling of Potential Body-Centric Networks 353 16.4.1 System-Level Modelling 353 16.4.2 Performance Analysis 354 16.5 Summary 355 References 358 17 Ultra-wideband Spatial Channel Characteristics 361 Wasim Q. Malik, Junsheng Liu, Ben Allen and David J. Edwards 17.1 Introduction 361 17.2 Preliminaries 361 17.3 UWB Spatial Channel Representation 362 17.4 Characterisation Techniques 363 17.5 Increase in the Communication Rate 364 17.5.1 UWB Channel Capacity 364 17.5.2 Capacity with CSIR Only 365
xii Contents 17.5.3 Capacity with CSIT 366 17.5.4 Statistical Characterisation 366 17.5.5 Experimental Evaluation of Capacity 367 17.6 Signal Quality Improvement 370 17.6.1 UWBSNRGain 371 17.6.2 SNR Gain with CSIR Only 371 17.6.3 SNR Gain with CSIT 371 17.6.4 Statistical Characterisation 372 17.6.5 Experimental Evaluation of Diversity 372 17.6.6 Coverage Range Extension 375 17.7 Performance Parameters 375 17.7.1 Spatial Fading Correlation 375 17.7.2 Eigen Spectrum 377 17.7.3 Angular Spread 379 17.7.4 Array Orientation 379 17.7.5 Channel Memory 380 17.7.6 Channel Information Quality 380 17.8 Summary 381 References 381 Part IV UWB Radar, Imaging and Ranging 385 Introduction to Part IV 387 Anthony K. Brown 18 Localisation in NLOS Scenarios with UWB Antenna Arrays 389 Thomas Kaiser, Christiane Senger, Amr Eltaher and Bamrung Tau Sieskul 18.1 Introduction 389 18.2 Underlying Mathematical Framework 394 18.3 Properties of UWB Beamforming 398 18.4 Beamloc Approach 401 18.5 Algorifhmic Framework 403 18.6 Time-delay Estimation 404 18.7 Simulation Results 406 18.8 Conclusions 410 References 410 19 Antennas for Ground-penetrating Radar 413 Ian Craddock 19.1 Introduction 413 19.2 GPR Example Applications 413 19.2.1 GPRforDemining 413 19.2.2 Utility Eocation and Road lnspection 414 19.2.3 A rchaeology and Forensics 416 19.2.4 Built-structure Imaging 418 19.3 Analysis and GPR Design 419 19.3.1 Typical GPR Configuration 419 19.3.2 RF Propagation in Lossy Media 420
xiii 19.3.3 Radar Waveform Choice 423 19.3.4 Other Antenna Design Criteria 424 19.4 Antenna Elements 425 19.4.1 Dipole, Resistively Loaded Dipole and Monopoles 425 19.4.2 Bicone and Bowtie 426 19.4.3 Hörn Antennas 428 19.4.4 Vivaldi Antenna 428 19.4.5 CPW-fed Slot Antenna 429 19.4.6 Spiral Antennas 429 19.5 Antenna Measurements, Analysis and Simulation 430 19.5.1 Antenna Measurement 430 19.5.2 Antenna Analysis and Simulation 432 19.6 Conclusions 433 Acknowledgements 434 References 434 20 Wideband Antennas for Biomedical Imaging 437 Ian Craddock 20.1 Introduction 437 20.2 Detection and Imaging 437 20.2.1 Breast Cancer Detection Li'sing Radio Waves 437 20.2.2 Radio-wave Imaging ofthe Breast 438 20.3 Waveform Choice and Antenna Design Criteria 440 20.4 Antenna Elements 441 20.4.1 Dipoles, Resistively Loaded Dipoles and Monopoles 441 20.4.2 Bowtie 442 20.4.3 Hörn Antennas 443 20.4.4 Spiral Antennas 443 20.4.5 Stacked-patch Antennas 444 20.5 Measurements, Analysis and Simulation 445 20.5.1 Antenna Measurement 445 20.5.2 Antenna Analysis and Simulation 446 20.6 Conclusions 447 Acknowledgements 448 References 448 21 UWB Antennas for Radar and Related Applications 451 Anthony K. Brown 21.1 Introduction 451 21.2 Medium-and Long-Range Radar 452 21.3 UWB Reflector Antennas 453 21.3.1 Definitions 453 21.3.2 Equivalent Aperture Model for Impulse Radiation 454 21.3.3 Parabolic Antenna 456 21.4 UWB Feed Designs 459 21.4.1 Feed Pattern Effects 460 21.4.2 Phase Centre Location 460 21.4.3 Input Impedance 460
xiv Contents 21.4.4 Polarisation 460 21.4.5 Blockage Effects 461 21.5 Feeds with Low Dispersion 461 21.5.1 Planar Spiral Antennas 461 21.5.2 TEM Feeds 462 21.5.3 Impulse Radiating Antenna (IRA) 466 21.6 Summary 468 References 468 Index 471