DOPPLER RADAR PHYSIOLOGICAL SENSING

1 Introduction 1
1.1 Current Methods of Physiological Monitoring, 2
1.2 Need for Noncontact Physiological Monitoring, 3
1.2.1 Patients with Compromised Skin, 3
1.2.2 Sleep Monitoring, 4
1.2.3 Elderly Monitoring, 5
1.3 Doppler Radar Potential for Physiological Monitoring, 5
1.3.1 Principle of Operation and Power Budget, 6
1.3.2 History of Doppler Radar in Physiological Monitoring, 8
References, 16
2 Radar Principles 21
2.1 Brief History of Radar, 21
2.2 Radar Principle of Operation, 22
2.2.1 Electromagnetic Wave Propagation and Reflection, 23
2.2.2 Radar Cross Section, 24
2.2.3 Radar Equation, 25
2.3 Doppler Radar, 28
2.3.1 Doppler Effect, 28
2.3.2 Doppler Radar Waveforms: CW, FMCW, Pulsed, 29
2.4 Monostatic and Bistatic Radar, 32
2.5 Radar Applications, 35
References, 36
3 Physiological Motion and Measurement 39
3.1 Respiratory System Motion, 39
3.1.1 Introduction to the Respiratory System, 39
3.1.2 Respiratory Motion, 40
3.1.3 Chest Wall Motion Associated with Breathing, 43
3.1.4 Breathing Patterns in Disease and Disorder, 43
3.2 Heart System Motion, 44
3.2.1 Location and Gross Anatomy of the Heart, 45
3.2.2 Electrical and Mechanical Events of the Heart, 46
3.2.3 Chest Surface Motion Due to Heart Function, 48
3.2.4 Quantitative Measurement of Chest Wall Motion Due to Heartbeat, 50
3.3 Circulatory System Motion, 53
3.3.1 Location and Structure of the Major Arteries and Veins, 54
3.3.2 Blood Flow Through Arteries and Veins, 55
3.3.3 Surface Motion from Blood Flow, 56
3.3.4 Circulatory System Motion: Variation with Age, 57
3.4 Interaction of Respiratory, Heart, and Circulatory Motion at the Skin Surface, 58
3.5 Measurement of Heart and Respiratory Surface Motion, 58
3.5.1 Radar Measurement of Physiological Motion, 59
3.5.2 Surface Motion Measurement of Respiration Rate, 59
3.5.3 Surface Motion Measurement of Heart/Pulse Rate, 61
References, 63
4 Physiological Doppler Radar Overview 69
4.1 RF Front End, 70
4.1.1 Quadrature Receiver, 73
4.1.2 Phase Coherence and Range Correlation, 77
4.1.3 Frequency Choice, 79
4.1.4 Antenna Considerations, 80
4.1.5 Power Budget, 80
4.2 Baseband Module, 83
4.2.1 Analog Signal Conditioning and Coupling Methods, 83
4.2.2 Data Acquisition, 85
4.3 Signal Processing, 86
4.3.1 Phase Demodulation, 86
4.3.2 Demodulated Phase Processing, 87
4.4 Noise Sources, 90
4.4.1 Electrical Noise, 90
4.4.2 Mechanical Noise, 92
4.5 Conclusions, 92
References, 93
5 CW Homodyne Transceiver Challenges 95
5.1 RF Front End, 95
5.1.1 Single-Channel Limitations, 96
5.1.2 LO Leakage Cancellation, 103
5.1.3 IQ Imbalance Assessment, 109
5.2 Baseband Module, 113
5.2.1 AC and DC Coupling, 113
5.2.2 DC Canceller, 114
5.3 Signal Demodulation, 118
5.3.1 DC Offset and DC Information, 118
5.3.2 Center Tracking, 125
5.3.3 DC Cancellation Results, 130
References, 134
6 Sources of Noise and Signal-to-Noise Ratio 137
6.1 Signal Power, Radar Equation, and Radar Cross Section, 138
6.1.1 Radar Equation, 138
6.1.2 Radar Cross Section, 140
6.1.3 Reflection and Absorption, 141
6.1.4 Phase-to-Amplitude Conversion, 141
6.2 Oscillator Phase Noise, Range Correlation and Residual Phase Noise, 143
6.2.1 Oscillator Phase Noise, 143
6.2.2 Range Correlation and Residual Phase Noise, 147
6.3 Contributions of Various Noise Sources, 151
6.3.1 Phase Noise, 151
6.3.2 Baseband 1/f Noise, 154
6.3.3 RF Additive White Gaussian Noise, 154
6.4 Signal-to-Noise Ratio, 155
6.5 Validation of Range Correlation, 157
6.6 Human Testing Validation, 158
References, 168
7 Doppler Radar Physiological Assessments 171
7.1 Actigraphy, 172
7.2 Respiratory Rate, 176
7.3 Tidal Volume, 179
7.4 Heart Rates, 184
7.5 Heart Rate Variability, 185
7.6 Respiratory Sinus Arrhythmia, 190
7.7 RCs and Subject Orientation, 196
References, 204
8 Advanced Performance Architectures 207
8.1 DC Offset and Spectrum Folding, 208
8.1.1 Single-Channel Homodyne System with Phase Tuning, 208
8.1.2 Heterodyne System with Frequency Tuning, 213
8.1.3 Low-IF Architecture, 220
8.2 Motion Interference Suppression, 224
8.2.1 Interference Cancellation, 226
8.2.2 Bistatic Radar: Sensor Nodes, 231
8.2.3 Passive RF Tags, 240
8.3 Range Detection, 250
8.3.1 Physiological Monitoring with FMCW Radar, 250
8.3.2 Physiological Monitoring with UWB Radar, 251
References, 266
9 Applications and Future Research 269
9.1 Commercial Development, 269
9.1.1 Healthcare, 269
9.1.2 Defense, 272
9.2 Recent Research Areas, 272
9.2.1 Sleep Study, 272
9.2.2 Range, 275
9.2.3 Multiple Subject Detection, 276
9.2.4 Animal Monitoring, 279
9.3 Conclusion, 282
References, 282
Index 285

This book includes an overview of current physiological monitoring techniques and explains the fundamental technology used in remote non-contact monitoring methods. Basic radio wave propagation and radar principles are introduced along with the fundamentals of physiological motion and measurement. Specific design and implementation considerations for physiological monitoring radar systems are then discussed in detail. The authors address current research and commercial development of Doppler radar based physiological monitoring for healthcare and other applications.
• Explains pros and cons of different Doppler radar architectures, including CW, FMCW, and pulsed Doppler radar
• Discusses nonlinear demodulation methods, explaining dc offset, dc information, center tracking, and demodulation enabled by dc cancellation
• Reviews advanced system architectures that address issues of dc offset, spectrum folding, motion interference, and range resolution
• Covers Doppler radar physiological measurements demonstrated to date, from basic cardiopulmonary rate extractions to more involved volume assessments

Doppler Radar Physiological Sensing serves as a fundamental reference for radar, biomedical, and microwave engineers as well as healthcare professionals interested in remote physiological monitoring methods.

Author Information
• Olga Boric-Lubecke, PhD, is a Professor of Electrical Engineering at the University of Hawaii at Manoa, and an IEEE Fellow. She is widely recognized as a pioneer and leader in microwave radar technologies for non-contact cardiopulmonary monitoring, and in the design of integrated circuits for biomedical applications.
• Victor M. Lubecke, PhD, is a Professor of Electrical Engineering at the University of Hawaii at Manoa. He is an emeritus IEEE Distinguished Microwave Lecturer and has over 25 years of experience in research and development of devices and methods for radio-based remote sensing systems.
• Amy Droitcour, PhD, has spent ten years developing radar-based vital signs measurement technology through her dissertation research and leading product development as CTO of Kai Medical. She currently serves as Senior Vice President of R&D at Wave 80 Biosciences.
• Byung-Kwon-Park, PhD, is a senior research engineer at the Mechatronics R&D Center in Korea.
• Aditya Singh, PhD, is currently a postdoctoral researcher at the University of Hawaii Neuroscience and MRI research Program.