Antennas for Portable Devices

Foreword ix

Acknowledgements xi

List of Contributors xiii

1 Introduction 1
Zhi Ning Chen

References 7

2 Handset Antennas 9
Brian S. Collins

2.1 Introduction 9

2.2 Performance Requirements 11

2.3 Electrically Small Antennas 14

2.4 Classes of Handset Antennas 18

2.5 The Quest for Efficiency and Extended Bandwidth 20

2.5.1 Handset Geometries 21

2.5.2 Antenna Position in the Handset 21

2.5.3 The Effect of the User 23

2.5.4 Antenna Volume 24

2.5.5 Impedance Behavior of a Typical Antenna in the Low Band 24

2.5.6 Fields and Currents on Handsets 27

2.5.7 Managing the Length–Bandwidth Relationship 29

2.5.8 The Effect on RF Efficiency of Other Components of the Handset 35

2.5.9 Specific Absorption Rate 38

2.5.10 Hearing Aid Compliance 39

2.5.11 Economic Considerations 39

2.6 Practical Design 40

2.6.1 Simulations 40

2.6.2 Materials and Construction 41

2.6.3 Recycling 41

2.6.4 Building the Prototype 41

2.6.5 Measurement 42

2.6.6 Design Optimization 44

2.7 Starting Points for Design and Optimization 44

2.7.1 External Antennas 45

2.7.2 Balanced Antennas 47

2.7.3 Antennas for Other Services 48

2.7.4 Dual-Antenna Interference Cancellation 49

2.7.5 Multiple Input, Multiple Output 49

2.7.6 Antennas for Lower-Frequency Bands – TV and Radio Services 50

2.8 The RF Performance of Typical Handsets 52

2.9 Conclusion 55

References 55

3 RFID Tag Antennas 59
Xianming Qing and Zhi Ning Chen

3.1 Introduction 59

3.2 RFID Fundamentals 60

3.2.1 RFID System Configuration 60

3.2.2 Classification of RFID Systems 62

3.2.3 Principles of Operation 65

3.2.4 Frequencies, Regulations and Standardization 67

3.3 Design Considerations for RFID Tag Antennas 71

3.3.1 Near-field RFID Tag Antennas 73

3.3.2 Far-field RFID Tag Antennas 80

3.4 Effect of Environment on RFID Tag Antennas 97

3.4.1 Near-field Tags 98

3.4.2 Far-field Tags 100

3.4.3 Case Study 106

3.5 Summary 109

References 109

4 Laptop Antenna Design and Evaluation 113
Duixian Liu and Brian Gaucher

4.1 Introduction 113

4.2 Laptop-Related Antenna Issues 114

4.2.1 Typical Laptop Display Construction 114

4.2.2 Possible Antennas for Laptop Applications 115

4.2.3 Mechanical and Industrial Design Restrictions 116

4.2.4 LCD Surface Treatment in Simulations 118

4.2.5 Antenna Orientation in Display 119

4.2.6 The Difference between Laptop and Cellphone Antennas 120

4.2.7 Antenna Location Evaluations 122

4.3 Antenna Design Methodology 124

4.3.1 Modeling 125

4.3.2 Cut-and-Try 125

4.3.3 Measurements 125

4.4 PC Card Antenna Performance and Evaluation 127

4.5 Link Budget Model 129

4.6 An INF Antenna Implementation 131

4.7 Integrated and PC Card Solutions Comparison 133

4.8 Dualband Examples 134

4.8.1 An Inverted-F Antenna with Coupled Elements 135

4.8.2 A Dualband PCB Antenna with Coupled Floating Elements 138

4.8.3 A Loop Related Dualband Antenna 142

4.9 Remarks on WLAN Antenna Design and Evaluations 148

4.10 Antennas for Wireless Wide Area Network Applications 148

4.10.1 INF Antenna Height Effects on Bandwidth 149

4.10.2 A WWAN Dualband Example 152

4.11 Ultra-Wide Band Antennas 157

4.11.1 Description of the UWB Antenna 159

4.11.2 UWB Antenna Measurement Results 163

References 164

5 Antenna Issues in Microwave Thermal Therapies 169
Koichi Ito and Kazuyuki Saito

5.1 Microwave Thermal Therapies 169

5.1.1 Introduction 169

5.1.2 Classification by Therapeutic Temperature 169

5.1.3 Heating Schemes 170

5.2 Interstitial Microwave Hyperthermia 171

5.2.1 Introduction and Requirements 171

5.2.2 Coaxial-Slot Antenna 173

5.2.3 Numerical Calculation 173

5.2.4 Performance of the Coaxial-Slot Antenna 177

5.2.5 Temperature Distributions Around the Antennas 180

5.3 Clinical Trials 183

5.3.1 Equipment 183

5.3.2 Treatment by Use of a Single Antenna 183

5.3.3 Treatment by Use of an Array Applicator 185

5.3.4 Results of the Treatment 187

5.4 Other Applications 189

5.4.1 Treatment of Brain Tumors 189

5.4.2 Intracavitary Microwave Hyperthermia for Bile Duct Carcinoma 189

5.5 Summary 194

References 195

6 Antennas for Wearable Devices 197
Akram Alomainy, Yang Hao and Frank Pasveer

6.1 Introduction 197

6.1.1 Wireless Body Area Networks 198

6.1.2 Antenna Design Requirements for Wireless BAN/PAN 199

6.2 Modelling and Characterization of Wearable Antennas 204

6.2.1 Wearable Antennas for BANs/PANs 204

6.2.2 UWB Wearable Antennas 209

6.3 WBAN Radio Channel Characterization and Effect of Wearable Antennas 213

6.3.1 Radio Propagation Measurement for WBANs 214

6.3.2 Propagation Channel Characteristics 214

6.4 Case Study: A Compact Wearable Antenna for Healthcare Sensors 218

6.4.1 Application Requirements 218

6.4.2 Theoretical Antenna Considerations 218

6.4.3 Sensor Antenna Modelling and Characterization 220

6.4.4 Propagation Channel Characterization 223

6.5 Summary 226

References 227

7 Antennas for UWB Applications 231
Zhi Ning Chen and Terence S.P. See

7.1 UWB Wireless Systems 231

7.2 Challenges in UWB Antenna Design 233

7.3 State-of-the-Art Solutions 247

7.3.1 Frequency-Independent Designs 247

7.3.2 Planar Broadband Designs 248

7.3.3 Crossed and Rolled Planar Broadband Designs 253

7.3.4 Planar Printed PCB Designs 254

7.3.5 Planar Antipodal Vivaldi Designs 257

7.4 Case Study 258

7.4.1 Small Printed Antenna with Reduced Ground-Plane Effect 258

7.4.2 Wireless USB 270

7.5 Summary 282

References 283

Index 287