Yongxin Guo is a Full Professor at National University of Singapore. He is a Fellow of IEEE and Singapore Academy of Engineering. He is serving as Editor-in-Chief, IEEE Journal of Electromagnetics, RF and Microwave in Medicine and Biology. He is a Distinguished Lecturer for IEEE Antennas and Propagation Society and his current research interests include wireless power transfer, antennas, oxford, electromagnetic sensing and MMIC modelling and design for biomedicine, internet of things and wireless communications.

Yuan Feng is a Research Fellow of National University of Singapore and an Adjunct Associate Investigator of NUS Suzhou Research Institute. Dr. Feng serves as a Reviewer for the IEEE Transactions on Antennas and Propagation and he received his PhD. from Tsinghua University, China, in 2020. His research interests include neuromodulation technology, implantable and wearable antennas for biomedical and healthcare applications, RF energy harvesting, and wireless power.

Changrong Liu is an Associate Professor at Soochow University, China, and is a member of the IEEE. He received his PhD in radio physics from the University of Electronic Science and Technology of China in 2015 and his research interests include LTCC-based millimeter-wave antenna array design, circularly polarized beam-steering antenna array, and implantable antennas for biomedical applications, including wireless data telemetry, and power transfer.

Foreword xi

Preface xiii

Acknowledgment xv

1 Introduction: Toward Biomedical Applications 1

1.1 Biomedical Devices for Healthcare 1

1.1.1 Wearable Devices 3

1.1.2 Implantable Devices 6

1.2 Wireless Date Telemetry and Powering for Biomedical Devices 8

1.2.1 Wireless Data Telemetry for Biomedical Devices 8

1.2.2 Wireless Power Transmission for Biomedical Devices 12

1.3 Overview of Book 13

2 Miniaturized Wideband and Multiband Implantable Antennas 17

2.1 Introduction 17

2.2 Miniaturization Methods for Implantable Antenna Design 18

2.2.1 Use of High-permittivity Dielectric Substrate/Superstrate 18

2.2.2 Use of Planar Inverted-F Antenna Structure 20

2.2.3 Lengthening the Current Path of the Radiator 22

2.2.4 Loading Technique for Impedance Matching 24

2.2.5 Choosing Higher Operating Frequency 26

2.3 Wideband Miniaturized Implantable Antenna 28

2.3.1 Introducing Adjacent Resonant Frequency Points 28

2.3.1.1 Linear Wire Antenna 28

2.3.1.2 Slot Antenna 32

2.3.1.3 Loop Antenna 34

2.3.1.4 Microstrip Patch Antenna 34

2.3.2 Multiple Resonance and Wideband Impedance Matching 35

2.3.3 Advanced Technology for Detuning Problem 49

2.4 Multiband Miniaturized Implantable Antennas 50

2.4.1 Compact PIFAWith Multi-current Patch 50

2.4.2 Open-end Slots on Ground 54

2.4.3 Single-layer Design 55

2.5 Conclusions 61

3 Polarization Design for Implantable Antennas 67

3.1 Introduction 67

3.2 Compact Microstrip Patch Antenna for CP-implantable Antenna Design 68

3.2.1 Capacitively-loaded CP-implantable Patch Antenna 68

3.2.1.1 An Implantable Microstrip Patch Antenna with a Center Square Slot 68

3.2.1.2 Compact-implantable CP Patch Antenna with Capacitive Loading 71

3.2.1.3 Communication Link Study of the CP-implantable Patch Antenna 73

3.2.1.4 Sensitivity Evaluation of the Implantable CP Patch Antenna 75

3.2.2 Miniaturized Circularly Polarized-implantable Annular-ring Antenna 79

3.3 Wide AR Bandwidth-implantable Antenna 83

3.3.1 Miniaturized CP-implantable Loop Antenna 83

3.3.1.1 Configuration of the CP-implantable Loop Antenna 83

3.3.1.2 Principle of the CP-implantable Loop Antenna 86

3.3.1.3 Antenna Measurement and Discussions 88

3.3.1.4 Communication Link of the Implantable CP Loop Antennas 90

3.3.2 Ground Radiation CP-implantable Antenna 91

3.4 Application Base Design of CP-implantable Antenna -- Capsule Endoscopy 97

3.4.1 Axial-mode Multilayer Helical Antenna 97

3.4.1.1 Antenna Structure 99

3.4.1.2 Conformal Capsule Antenna Design Including Biocompatibility Shell Consideration 101

3.4.1.3 Wireless Capsule Endoscope System in a Human Body 103

3.4.1.4 In Vitro Testing and Discussions 108

3.4.2 Conformal CP Antenna for Wireless Capsule Endoscope Systems 112

3.4.2.1 Antenna Layout and Simulation Phantom 112

3.4.2.2 Mechanism of CP Operation 114

3.4.2.3 Results and Discussion 115

3.5 In Vivo Testing of Circularly Polarized-implantable Antennas 118

3.5.1 In Vivo Testing Configuration 118

3.5.2 Measured Reflection Coefficient 119

3.5.3 Analysis of the Results and Discussions 120

3.6 Conclusions 122

4 Differential-fed Implantable Antennas 129

4.1 Introduction 129

4.2 Dual-band Implantable Antenna for Neural Recording 130

4.2.1 Differential Reflection Coefficient Characterization 130

4.2.2 Antenna Design and Operating Principle 131

4.2.3 Measurement and Discussions 134

4.2.4 Communication Link Study 136

4.3 Integrated On-chip Antenna in 0.18¿m CMOS Technology 137

4.3.1 System Requirement and Antenna Design 139

4.3.2 Chip-to-SMA Transition Design and Measurement 142

4.4 Dual-band Implantable Antenna for Capsule Systems 146

4.4.1 Planar-implantable Antenna Design 146

4.4.2 Conformal Capsule Design 149

4.4.3 Coating and In Vitro Measurement 153

4.5 Miniaturized Differentially Fed Dual-band Implantable Antenna 154

4.5.1 Miniaturized Dual-band Antenna Design 155

4.5.2 Parametric Analysis and Measurement 158

4.5.2.1 The Effect of the Shorting Strip 158

4.5.2.2 The Effect of the Length of L-shaped Arms 158

4.5.2.3 Measurement 159

4.6 Differentially Fed Antenna With Complex Input Impedance for Capsule Systems 160

4.6.1 Antenna Geometry 161

4.6.2 Operating Principle 162

4.6.2.1 Equivalent Circuit 163

4.6.2.2 Parametric Study 164

4.6.2.3 Comparison With T-Match 166

4.6.3 Experiment 169

4.7 Conclusions 172

5 Wearable Antennas for On-/Off-Body Communications 177

5.1 Introduction 177

5.2 ExploringWearable Antennas: Design and Fabrication Techniques 179

5.2.1 Typical Designs ofWearable Antennas 179

5.2.2 Variation of Antenna Characteristics and Design Considerations 181

5.2.3 AMC-Backed Near-EndfireWearable Antenna 182

5.3 Latex Substrate and Screen-Printing forWearable Antennas Fabrication 183

5.4 AMC-backed Endfire Antenna 184

5.4.1 Bidirectional Yagi Antenna for Endfire Radiation 184

5.4.2 Near-Endfire Yagi Antenna Backed by SAMC 184

5.4.3 Near-Endfire Yagi Antenna Backed by DAMC 187

5.5 Simulations of the Antennas in Free Space 189

5.5.1 Return Loss 189

5.5.2 Radiation Patterns 189

5.5.3 Gain 190

5.6 Simulations of the Antennas on Human Body 191

5.6.1 Frequency Detuning 191

5.6.2 SAR and Antenna Efficiency 192

5.6.3 Radiation Patterns on A Human Body 194

5.7 Antenna Performance Under Deformation 195

5.8 Experiment 198

5.8.1 Return Loss 198

5.8.2 Radiation Pattern Measurement 198

5.8.3 Gain Measurement 201

5.9 Conclusion 201

6 Investigation and Modeling of Capacitive Human Body Communication 205

6.1 Introduction 205

6.2 Galvanic and Capacitive Coupling HBC 206

6.3 Capacitive HBC 207

6.3.1 Experimental Characterizations 207

6.3.2 Numerical Models 211

6.3.3 Circuit Models of Capacitive HBC 212

6.3.4 Theoretical Analysis 212

6.4 Investigation and Modeling of Capacitive HBC 214

6.4.1 Measurement Setup and Results 214

6.4.2 Simulation Setup and Results 220

6.4.3 Equivalent Circuit Model 226

6.5 Conclusions: Other Design Considerations of HBC Systems 230

6.5.1 Channel Characteristics 231

6.5.2 Modulation and Communication Performance 232

6.5.3 Systems and Application Examples 232

7 Near-field Wireless Power Transfer for Biomedical Applications 237

7.1 Introduction 237

7.2 Resonant InductiveWireless Power Transfer (IWPT) and IWPT Topologies 238

7.2.1 Resonances in IWPT 238

7.2.2 Resonant IWPT Topologies 242

7.2.3 Power Transfer Efficiency 242

7.2.4 Experimental Verification 244

7.2.5 Limitations of the Resonance Tuning 245

7.3 IWPT Topology Selection Strategies 247

7.3.1 For Applications With a Fixed Load 247

7.3.2 For Applications With a Variable Load 249

7.3.3 Optimal Operating Frequency 251

7.3.4 Upper Limit on Power Transfer Efficiency 252

7.4 CapacitiveWireless Power Transfer (CWPT) 254

7.4.1 NCC Link Modeling 256

7.4.1.1 Tissue Model 257

7.4.1.2 Tissue Loss 258

7.4.1.3 Conductor Loss (RC) 260

7.4.1.4 Self-inductance 260

7.4.1.5 Equivalent Capacitance 260

7.4.1.6 Return Loss 261

7.4.1.7 Power Transfer Efficiency 261

7.4.1.8 Power Transfer Limit 262

7.4.2 Full-wave Simulation 264

7.4.3 Optimal Link Design 266

7.5 CWPT: Experiments in Nonhuman Primate Cadaver 267

7.5.1 Study on Power Transfer Efficiency 267

7.5.2 Flexion Study 269

7.6 Summary 270

8 Far-field Wireless Power Transmission for Biomedical Application 275

8.1 Introduction 275

8.2 Far-Field EM Coupling 275

8.2.1 Power Transfer Efficiency 277

8.2.2 Link Design 278

8.2.3 Challenges and Solutions 279

8.3 Enhanced Far-field WPT Link for Implants 280

8.3.1 Safety Considerations for Far-field Wireless Power Transmission 280

8.3.2 Implantable Rectenna Design 281

8.3.2.1 Implantable Antenna Configuration 281

8.3.2.2 Wireless Power Link Study 284

8.3.2.3 Safety Concerns 285

8.3.2.4 Method to Enhance the Received Power 287

8.3.2.5 Wireless Power Link With the Parasitic Patch 288

8.3.3 Measurement and Discussion 290

8.3.3.1 Rectifier Circuit Design 291

8.3.3.2 Integration Solution of the Implantable Rectenna 294

8.3.3.3 Measurement Setup 295

8.4 WPT Antenna Misalignment: An Antenna Alignment Method Using Intermodulation 297

8.4.1 Operation Mechanism 298

8.4.1.1 PCE Enhancement and Intermodulation Generation 298

8.4.1.2 Relation Between Intermodulation and Misalignments 300

8.4.2 Miniaturized IMD Rectenna Design With NRIC Link 300

8.4.2.1 Miniaturized Rectifier With Intermodulation Readout 300

8.4.2.2 IMD Antenna CodesignedWith Rectifier Circuit 302

8.4.2.3 NRIC Link Establishment 304

8.4.3 Experimental Validation 306

8.4.3.1 Experimental Setup 306

8.4.3.2 Results and Discussion 308

8.5 Summary 309

9 System Design Examples: Peripheral Nerve Implants and Neurostimulators 313

9.1 Introduction 313

9.2 Wireless Powering and Telemetry for Peripheral Nerve Implants 314

9.2.1 Peripheral Nerve Prostheses 314