ANTENNAS FROM THEORY TO PRACTICE

Yi Huang University of Liverpool, UK

Kevin Boyle NXP Semiconductors, UK

©WILEY A John Wiley and Sons, Ltd, Publication

Contents

Preface xi

Acronyms and Constants xiii

1 Introduction 1 1.1 A Short History of Antennas 1 1.2 Radio Systems and Antennas 4 1.3 Necessary Mathematics 6

1.3.1 Complex Numbers 6 1.3.2 Vectors and Vector Operation 7 1.3.3 Coordinates 10

1.4 Basics of Electromagnetics 11 1.4.1 The Electric Field 12 1.4.2 The Magnetic Field 15 1.4.3 Maxwell's Equations 16 1.4.4 Boundary Conditions 19

1.5 Summary 21 References 21 Problems 21

2 Circuit Concepts and Transmission Lines 23 2.1 Circuit Concepts 23

2.1.1 Lumped and Distributed Element Systems 25 2.2 Transmission Line Theory 25

2.2.7 Transmission Line Model 25 2.2.2 Solutions and Analysis 28 2.2.3 Terminated Transmission Line 32

2.3 The Smith Chart and Impedance Matching 41 2.3.1 The Smith Chart 41 2.3.2 Impedance Matching 44 2.3.3 The Quality Factor and Bandwidth 51

2.4 Various Transmission Lines 55 2.4.1 Two-wire Transmission Line 56 2.4.2 Coaxial Cable 57 2.4.3 Microstrip Line 60

vi Contents

2.4.4 Stripline 63 2.4.5 Coplanar Waveguide (CPW) 66 2.4.6 Waveguide 68

2.5 Connectors 70 2.6 Summary 74

References 74 Problems 74

3 Field Concepts and Radio Waves 77 3.1 Wave Equation and Solutions 77

3.1.1 Discussion on Wave Solutions 79 3.2 The Plane Wave, Intrinsic Impedance and Polarization 80

3.2.1 The Plane Wave and Intrinsic Impedance 80 3.2.2 Polarization 82

3.3 Radio Wave Propagation Mechanisms 83 3.3.1 Reflection and Transmission 83 3.3.2 Diffraction andHuygens's Principle 91 3.3.3 Scattering 92

3.4 Radio Wave Propagation Characteristics in Media 93 3.4.1 Media Classification and Attenuation 93

3.5 Radio Wave Propagation Models 97 3.5.7 Free Space Model 97 3.5.2 Two-ray Model/Plane Earth Model 98 3.5.3 Multipath Models 99

3.6 Comparison of Circuit Concepts and Field Concepts 101 3.6.1 Skin Depth 101

3.7 Summary 104 References 104 Problems 104

4 Antenna Basics 107 4.1 Antennas to Radio Waves 107

4.1.1 Near Field and Far Field 108 4.1.2 Antenna Parameters from the Field Point of View 112

4.2 Antennas to Transmission Lines 122 4.2.1 Antenna Parameters from the Circuit Point of View 122

4.3 Summary 125 References 126 Problems 126

5 Popular Antennas 129 5.1 Wire-Type Antennas 129

5.1.1 Dipoles 129 5.1.2 Monopoles and Image Theory 137 5.1.3 Loops and the Duality Principle 141 5.7.4 Helical Antennas 147

Contents vii

5.1.5 Yagi—Uda Antennas 152 5.1.6 Log-Periodic Antennas and Frequency-Independent Antennas 157

5.2 Aperture-Type Antennas 163 5.2.7 Fourier Transforms and the Radiated Field 163 5.2.2 Horn Antennas 169 5.2.3 Reflector and Lens Antennas 175 5.2.4 Slot Antennas and Babinet's Principle 180 5.2.5 Microstrip Antennas 184

5.3 Antenna Arrays 191 5.3.1 Basic Concept 192 5.3.2 Isotropic Linear Arrays 193 5.3.3 Pattern Multiplication Principle 199 5.3.4 Element Mutual Coupling 200

5.4 Some Practical Considerations 203 5.4.1 Transmitting and Receiving Antennas: Reciprocity 203 5.4.2 Baluns and Impedance Matching 205 5.4.3 Antenna Polarization 206 5.4.4 Radomes, Housings and Supporting Structures 208

5.5 Summary 211 References 211 Problems 212

6 Computer-Aided Antenna Design and Analysis 215 6.1 Introduction 215 6.2 Computational Electromagnetics for Antennas 217

6.2.7 Method of Moments (MoM) 218 6.2.2 Finite Element Method (FEM) 228 6.2.3 Finite-Difference Time Domain (FDTD) Method 229 6.2.4 Transmission Line Modeling (TLM) Method 230 6.2.5 Comparison of Numerical Methods 230 6.2.6 High-Frequency Methods 232

6.3 Examples of Computer-Aided Design and Analysis 233 6.3.1 Wire-type Antenna Design and Analysis 233 6.3.2 General Antenna Design and Analysis 243

6.4 Summary 251 References 251 Problems 252

7 Antenna Manufacturing and Measurements 253 7.1 Antenna Manufacturing 253

7.7.7 Conducting Materials 253 7.7.2 Dielectric Materials 255 7.7.5 New Materials for Antennas 255

7.2 Antenna Measurement Basics 256 7.2.7 Scattering Parameters 256 7.2.2 Network Analyzers 258

viii Contents

7.3 Impedance, Su, VSWR and Return Loss Measurement 261 7.3.1 Can I Measure These Parameters in My Office? 261 7.3.2 Effects of a Small Section of a Transmission Line or a Connector 262 7.3.3 Effects of Packages on Antennas 262

7.4 Radiation Pattern Measurements 263 7.4.1 Far-Field Condition 264 7.4.2 Open-Area Test Sites (OATS) 265 7.4.3 Anechoic Chambers 267 7.4.4 Compact Antenna Test Ranges (CATR) 268 7.4.5 Planar and Cylindrical Near-Field Chambers 270 7.4.6 Spherical Near-Field Chambers 270

7.5 Gain Measurements 272 7.5.1 Comparison with a Standard-Gain Horn 272 7.5.2 Two-Antenna Measurement 272 7.5.3 Three-Antenna Measurement 273

7.6 Miscellaneous Topics 273 7.6.7 Efficiency Measurements 273 7.6.2 Reverberation Chambers 21Л 7.6.3 Impedance De-embedding Techniques 275 7.6.4 Probe Array in Near-Field Systems 276

7.7 Summary 281 References 281 Problems 282

8 Special Topics 283 8.1 Electrically Small Antennas 283

8.1.1 The Basics and Impedance Bandwidth 283 8.1.2 Antenna Size-Reduction Techniques 299

8.2 Mobile Antennas, Antenna Diversity and Human Body Effects 304 8.2.1 Introduction 304 8.2.2 Mobile Antennas 305 8.2.3 Antenna Diversity 318 8.2.4 User Interaction 325

8.3 Multiband and Ultra-Wideband Antennas 334 8.3.1 Introduction 334 8.3.2 Multiband Antennas 334 8.3.3 Wideband Antennas 337

8.4 RFID Antennas 340 8.4.1 Introduction 340 8.4.2 Near-Field Systems 343 8.4.3 Far-Field Systems 349

8.5 Reconfigurable Antennas 352 8.5.1 Introduction 352 8.5.2 Switching and Variable-Component Technologies 352 8.5.3 Resonant Mode Switching/Tuning 354

Contents ix

8.5.4 Feed Network Switching/Tuning 355 8.5.5 Mechanical Reconfiguration 355

8.6 Summary 356 References 356

Index 357