EM Detection of Concealed Targets

Preface xi

Acknowledgments xiii

List of Frequently used Acronyms xv

1 Introduction 1

1.1 Scope and Objectives 1

1.2 Structure 2

1.3 Market Needs for Security 2

1.4 Targets inside Containers 5

1.5 Buried Land Mines 5

1.6 Forensic Detection of Buried Bodies 6

1.7 Avalanche and Earthquake Victims 7

1.8 Concealed Humans 7

1.9 Concealed Targets on Humans 8

1.10 Radiological Considerations 8

1.11 Licensing Considerations 10

1.12 Statistics of the Detection Performance of a Sensor 12

1.13 Summary 19

2 Physics of Propagation 20

2.1 Introduction 20

2.2 Propagation of Electromagnetic Fields in Free Space 21

2.2.1 Reactive Fields 22

2.2.2 Near Fields 23

2.2.3 Far Fields 23

2.2.4 Polarization 24

2.2.5 Radar Cross Section 27

2.2.6 Reflection 30

2.2.7 Refraction 31

2.2.8 Brewster Angle 31

2.2.9 Dispersion 33

2.2.10 Anisotropy 33

2.2.11 Clutter 33

2.3 Propagation of Energy in a Dielectric 35

2.3.1 Introduction 35

2.3.2 Velocity in a Dielectric 37

2.3.3 Impedance of a Dielectric 38

2.3.4 Propagation Loss in a Dielectric 39

2.3.5 Coupling Losses into Materials 44

2.4 Dielectric Properties of Soils and Rocks 45

2.5 Propagation in Water 51

2.6 Atmospheric Absorption of Electromagnetic Waves 53

2.6.1 Rain and Fog 55

2.6.2 Dust, Smoke, and Sand Storms 57

2.7 Attenuation of Electromagnetic Fields by Materials 59

2.7.1 Human and Animal 59

2.7.2 Heartbeat 61

2.7.3 Respiration 62

2.7.4 Clothing 66

2.7.5 Construction Materials 71

2.7.6 Explosives 76

2.8 Summary 82

3 Antennas 83

3.1 Introduction 83

3.2 Antenna Parameters 85

3.2.1 Antenna Directivity 85

3.2.2 Antenna Gain 86

3.2.3 Antenna Efficiency 88

3.2.4 Side Lobes and Back Lobes 88

3.2.5 Bandwidth 88

3.2.6 Polarization—Linear, Elliptical, and Circular 89

3.2.7 Antenna Phase Center 89

3.2.8 Antenna Patterns 90

3.2.9 Time Side Lobes and Ring-down 91

3.2.10 Antenna Footprint 93

3.3 Aperture Antennas 95

3.4 Antennas for Proximal Operation 97

3.4.1 Introduction 97

3.4.2 Coupling Energy into the Ground or a Dielectric 98

3.5 Linear Phase Antennas 101

3.5.1 Dipoles 101

3.5.2 Loaded Antennas 103

3.5.3 BiConical Antennas 106

3.5.4 Bow-Tie Antennas 107

3.5.5 Dielectric Road Antennas 108

3.5.6 TEM Horn Antennas 109

3.5.7 Impulse Radiating Antennas 115

3.6 Nonlinear Phase Antennas 117

3.6.1 Vivaldi Antennas 118

3.6.2 Equiangular Antennas 119

3.6.3 Horn Antennas 120

3.7 Antenna Arrays 121

3.8 Summary 126

4 Nuclear Quadrupole Resonance 128

4.1 Introduction 128

4.2 Pulse Sequences 131

4.3 System Design 138

4.3.1 Introduction 138

4.3.2 Transmit-and-Receive Coils 139

4.3.3 Receiver and Coil Considerations 143

4.4 Signal Processing 144

4.5 Detection of Explosives 148

4.6 Land-Mine Detection 152

4.7 Illicit Drugs 156

4.7.1 Cocaine 157

4.7.2 Cocaine Hydrochloride 157

4.7.3 Heroin (Diamorphine) 158

4.8 Summary 162

5 Radar Systems 164

5.1 Introduction 164

5.2 Doppler Radar Systems 164

5.3 Frequency-Domain Radars 169

5.3.1 Introduction 169

5.3.2 Two-Frequency Doppler Radar 170

5.3.3 Stepped Frequency Radar Systems 170

5.3.4 Frequency-Modulated Continuous-Wave Radar 177

5.4 Harmonic Radar 188

5.5 Noise Radar 194

5.6 Spatial Modulation 198

5.7 Amplitude Modulation 202

5.8 Summary 213

6 Passive Systems 214

6.1 Introduction 214

6.2 Principles of Radiometry 215

6.3 Total Power Radiometer 218

6.4 Dicke Radiometer 219

6.5 Minimum Detectable Temperature 220

6.6 Temperature Resolution 221

6.7 Imaging Systems 226

6.8 Summary 227

7 Applications and Technology 229

7.1 Introduction 229

7.2 Physiological Monitoring 229

7.3 Earthquake and Avalanche Radar Systems 231

7.4 Forensic Applications 233

7.5 Through-Wall Radar (TWR) for Surveillance 234

7.6 Harmonic Radar Systems 240

7.7 Land-Mine Detection Radar Systems 240

7.7.1 Handheld Land-Mine Detection Radar Systems 240

7.7.2 Vehicle-Mounted Land-Mine Detection Radar Systems 243

7.8 Radar for General Search Operations 246

7.9 Spatially Modulated Systems 248

7.10 Millimeter-Wave Radar Systems 248

7.11 Summary 253

8 Summary 254

References 260

Index 279