Antennas and Wireless Power Transfer Methods for Biomedical Applications
Description
Join the cutting edge of biomedical technology with this essential reference
The role of wireless communications in biomedical technology is a significant one. Wireless and antenna-driven communication between telemetry components now forms the basis of cardiac pacemakers and defibrillators, cochlear implants, glucose readers, and more. As wireless technology continues to advance and miniaturization progresses, it's more essential than ever that biomedical research and development incorporate the latest technology.
Antennas and Wireless Power Transfer Methods for Biomedical Applications provides a comprehensive introduction to wireless technology and its incorporation into the biomedical field. Beginning with an introduction to recent developments in antenna and wireless technology, it analyzes the major wireless systems currently available and their biomedical applications, actual and potential. The result is an essential guide to technologies that have already improved patient outcomes and increased life expectancies worldwide.
Readers will also find:
- Authored by internationally renowned researchers of wireless technologies
- Detailed analysis of CP implantable antennas, wearable antennas, near-field wireless power, and more
- Up to 100 figures that supplement the text
Antennas and Wireless Power Transfer Methods for Biomedical Applications is a valuable introduction for biomedical researchers and biomedical engineers, as well as for research and development professionals in the medical device industry.
More details
Other editions
Additional editions
Persons
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.
Content
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 0.18µm 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
9.2.1.1 Stimulator Implant 314
9.2.1.2 Neural Recording 314
9.2.1.3 Wireless Power Delivery and Telemetry Requirements 316
9.2.2 Wireless Platform for Peripheral Nerve Implants 317
9.2.2.1 Wireless Platform for Stimulator Implant 317
9.2.2.2 Wireless Platform for Recording Implant 319
9.2.3 Design and Experiments 319
9.2.3.1 Power Transfer Characteristics in Tissue Environments 320
9.2.3.2 Power Transfer Link for Peripheral Nerve Implants 323
9.2.3.3 Stimulator Implant Experiment 324
9.2.4 Safety 328
9.2.4.1 Biosafety 328
9.2.4.2 Electrical Safety 328
9.2.5 Near-field Resonant Inductive-coupling Link (NRIC) Versus Near-field Capacitive-coupling Link (NCC) 328
9.3 Co-matching Solution for Neurostimulator Narrow Band Antenna 330
9.3.1 Co-matching Antenna Operating Mode 332
9.3.2 Antenna Property in Body Phantom 334
9.3.3 Co-matching Circuit Design 336
9.3.4 Fabrication Processing of the Proposed Antenna 338
9.3.5 Reflection Coefficient and Impedance Measurement 339
9.3.6 Radiation Performance 340
9.4 Reconfigurable Antenna for Neurostimulator 343
9.4.1 Tuning Principle 344
9.4.2 Antenna Configuration and Design Procedures 344
9.4.3 Antenna Manufacturing and Measurement Setup 347
9.4.4 System Design 348
9.4.5 Antenna Tuning and Optimized RF Link 349
9.5 Summary 352
References 352
Index 357
1
Introduction: Toward Biomedical Applications
1.1 Biomedical Devices for Healthcare
The advancement in healthcare and health monitoring technologies has closely paralleled the overarching trajectory of human civilization. In ancient China, for example, practitioners of traditional medicine utilized methodologies such as observation, auditory examination, inquiry, and pulse diagnosis-referred to as "Wang, Wen, Wen, Qie"-to determine an individual's health status. These practices, marking the earliest recorded instances of health monitoring, underscored the importance of examining physical manifestations, listening to patients' reported symptoms, inquiring about their medical history, and palpating their pulse in the diagnosis and treatment of various health conditions. Though these methods hinged on subjective assessments, they established an understanding of the crucial linkage between external physical signs and internal health conditions.
With the advent of revolutionary technological and medical breakthroughs, we have embarked on a remarkable journey toward a more precise, quantitative characterization of human health and disease states. This entails harnessing an extensive array of physical, electrical, and chemical indicators in a quest for precise and quantitative comprehension [1] (Figure 1.1). This transition, marking the dawn of modern, data-driven medicine, spurred the development of advanced biomedical devices [2]. These devices integrate sophisticated sensing technologies, data analysis algorithms, and wireless communication capabilities, paving the way for precise and continuous health monitoring [3].
Physical indicators tied to human health include metrics such as heart rate and pulse, which can be gauged through the detection of bodily mechanical movements. Electrical indicators involve signals generated by potential differences within the human body, such as electrocardiograms (ECGs), electroencephalograms (EEGs), and electromyograms (EMGs). These electrical signals reflect the electrical activity of the heart, brain, and muscles, respectively, offering valuable insights into the functionality of these vital organs and our overall physiological state.
Chemical indicators, including metrics such as blood oxygen saturation and glucose levels, provide crucial insights into metabolic activities and bodily functions. These parameters are measured using specialized sensors and analytical techniques, facilitating the early detection and proactive management of a myriad of health conditions, ranging from respiratory disorders and cardiovascular diseases to diabetes.
Figure 1.1 Physical, electrical, and chemical indicators for a human body.
Source: Chen et al. [1]/Springer Nature/CC BY 4.0.
Figure 1.2 Biomedical sensors for health monitoring.
Source: Choi et al. [3]/John Wiley & Sons.
The advent of biomedical devices has revolutionized healthcare by integrating these physical, electrical, and chemical indicators into comprehensive health-monitoring systems, as shown in Figure 1.2. Designed to measure, record, and analyze vital signs, these devices equip healthcare professionals with the data necessary to make informed decisions regarding patient diagnosis, treatment, and care. As technology continues to advance, biomedical devices are becoming increasingly miniaturized, accurate, and interconnected. This evolution not only enables individuals to actively monitor their health, but it also fosters the rise of personalized healthcare models, reshaping the healthcare landscape as we know it.
Over the years, the evolution of biomedical devices for healthcare has been marked by substantial advancements, primarily driven by the growing demand for accurate and tailored health-monitoring solutions. Initially, the focus of biomedical devices centered on recording basic vital signs, such as heart rate and blood pressure, using analog tools. However, the emergence of digital technology and the drive toward miniaturization have led to the transformation of these devices into intricate systems capable of monitoring a broad spectrum of physiological parameters [4].
The integration of sensor technologies [4], signal processing algorithms [5], and wireless communication capabilities [6] has spearheaded the development of wearable devices [7], remote health-monitoring systems [8], and implantable medical devices [9]. Wearable devices, such as fitness trackers and smartwatches, have gained significant popularity due to their ability to provide real-time monitoring of vital signs, physical activity, and sleep patterns. These tools empower individuals to keep track of their health and make informed lifestyle decisions.
Remote monitoring systems have brought about a revolution in healthcare, enabling medical professionals to remotely monitor patients' health status and intervene as necessary. These systems typically utilize wearable sensors, home-monitoring devices, and mobile applications, facilitating patients to transmit their health data to healthcare providers for analysis and timely intervention. This approach is especially beneficial for individuals with chronic conditions, the elderly, and those residing in remote locations, as it minimizes the need for frequent hospital visits, thereby enhancing overall healthcare accessibility and outcomes.
Implantable medical devices have also played a pivotal role in the advancement of healthcare. These devices are surgically placed inside a human body to monitor and manage specific medical conditions. Examples of such devices include pacemakers for regulating cardiac rhythm disorders, neurostimulators for controlling chronic pain or movement disorders, and implantable glucose monitors for diabetes management. These devices often incorporate wireless communication capabilities to facilitate data transfer and remote monitoring, enabling healthcare professionals to closely track patients' conditions and adjust treatment protocols accordingly.
The relentless advancements in technology, including miniaturization, improved power efficiency, and enhanced connectivity, have significantly broadened the capabilities of biomedical devices. Further, the integration of artificial intelligence and machine learning algorithms enhances the diagnostic and monitoring abilities of these devices, enabling early detection of irregularities, personalized treatment recommendations, and improved patient outcomes.
In the following sections, we will provide examples of some of the current state-of-the-art wearable and implantable medical devices. These devices showcase the advancements in technology and their potential to revolutionize healthcare.
1.1.1 Wearable Devices
As illustrated in Figure 1.3, wearable devices embody a multitude of forms, merging sophisticated sensing technologies with accessible and user-centric designs [10]. These devices offer an array of capabilities, granting individuals the opportunity to track their health indicators in real-time. Here, we delve into a variety of wearable devices, elucidating their distinct functionalities and application methods.
Figure 1.3 Wearable medical devices used in patient care.
Source: Ref. [10].
Wearable spirometers integrated with masks: Specifically designed for individuals managing respiratory conditions such as asthma or chronic obstructive pulmonary disease (COPD), these devices make measuring lung function parameters, including forced vital capacity (FVC) and forced expiratory volume in one second (FEV1), conveniently accessible [11]. The ability to track respiratory health, observe changes in lung function, and adjust medication or treatment plans accordingly equips users with a proactive approach to their health. Additionally, wireless communication technology facilitates data transmission to healthcare providers for remote monitoring and analysis, enabling prompt intervention and personalized care.
Wearable watches and wristbands with integrated blood pressure, oxygen saturation, and pulse monitoring sensors: These devices offer consistent monitoring of vital signs, including blood pressure, oxygen saturation levels, and pulse rate. Throughout the day, users can easily track these parameters, fostering early detection of any potential irregularities. This vital information is particularly useful for individuals managing hypertension, cardiovascular diseases, or respiratory conditions. Furthermore, wireless connectivity supports seamless transmission of vital sign data to healthcare professionals for remote monitoring, providing real-time feedback and proactive condition management [12].
Body temperature and activity tracking sensors: Devices equipped with temperature sensors and accelerometers empower users to monitor body temperature variations and track their physical activity levels [13]. These devices find versatile applications, including fitness tracking, sleep monitoring, and remote patient monitoring. With wireless connectivity, data is seamlessly transmitted to healthcare providers, allowing for remote assessments and personalized care recommendations based on collected data.
Upper arm wearable...
