Ultra Low-Power Biomedical Signal Processing (eBook)

Foreword 6
Contents 8
Introduction 12
Biomedical signal processing 12
Biomedical applications of the wavelet transform 13
Cardiac signal analysis 14
Analog versus digital circuitry - a power consumption challenge for biomedical front-ends 15
Power consumption in analog sense amplifiers 16
Power per pole for analog filters 17
Power consumption in digital sense amplifiers 17
Power consumption in A/D converters 17
Power consumption in digital filters 19
Objective and scope of this book 20
Outline 21
References 22
The Evolution of Pacemakers: An Electronics Perspective 24
The heart 25
Excitation and conduction system 26
Cardiac signals 27
Surface electrocardiogram 27
Intracardiac electrogram (IECG) 28
Cardiac diseases - arrythmias 28
The history and development of cardiac pacing 29
What is an artificial pacemaker? 29
Hyman's pacemaker 30
Dawn of a modern era - implantable pacemakers 30
Demand pacemaker 33
Dual-chamber pacemaker 36
Rate-responsive pacemaker 37
New features in modern pacemakers 37
Morphological analysis 39
Summary and conclusions 40
References 40
Wavelet versus Fourier Analysis 43
Introduction 43
Fourier transform 43
Windowing function 44
Wavelet transform 45
Continuous-time wavelet bases 49
Complex continuous-time wavelet bases 51
Signal processing with the wavelet transform 52
Singularity detection - wavelet zoom 52
Modulus maxima 53
Lipschitz exponent - regularity 53
Wavelet vanishing moments 55
Regularity measurements with wavelets 55
Denoising 57
Compression 57
Low-power analog wavelet filter design 58
Conclusions 59
References 59
Analog Wavelet Filters: The Need for Approximation 61
Introduction 61
Complex first order filters 61
Padé approximation in the Laplace domain 66
Oscillatory wavelet bases approximation 70
L2 approximation 73
Other approaches to wavelet base approximation 76
Bessel-Thomson filters - a quasi-Gaussian impulse response 76
Filanovsky's filter approach Filanovsky 77
Fourier-series method 78
Discussion 81
Conclusions 83
References 83
Optimal State Space Descriptions 85
State space description 85
Dynamic range 87
Dynamic range optimization 88
Sparsity 90
Orthogonal transformations 90
Hessenberg decomposition 90
Schur decomposition 91
Canonical form representations 92
Biquad structure 94
Diagonal controllability gramian - an orthonormal ladder structure 95
Sparsity versus dynamic range comparison 98
New Sparsity Figure-of-Merit (SFOM) 99
Sensitivity 100
New Dynamic Range-Sparsity-Sensitivity (DRSS) figure-of-merit 103
Conclusion 104
References 104
Ultra Low-Power Integrator Designs 105
Gm-C filters 105
nA/V CMOS triode transconductor 106
A pA/V Delta-Gm (Delta-Gm) transconductor 109
Translinear (log-domain) filters 111
Static and dynamic translinear principle 111
Log-domain integrator 113
Class-A log-domain filter design examples 115
Bipolar multiple-input log-domain integrator 115
CMOS multiple-input log-domain integrator 116
High-frequency log-domain integrator in CMOS technology 117
Voltage follower 118
Simulation results 120
Low-power class-AB sinh integrators 121
A state-space formulation for class-AB log-domain integrators 121
Class-AB sinh integrator based on state-space formulation using single transistors 123
Companding sinh integrator 125
Circuit design 126
Ultra low-power class-AB sinh integrator 128
CMOS integrator implementation 130
Conclusions 137
Discussion 137
Conclusions 138
References 138
Ultra Low-Power Biomedical System Designs 141
Dynamic translinear cardiac sense amplifier for pacemakers 142
Differential voltage to single-ended current converter 143
Bandpass filter 144
Absolute value and RMS-DC converter circuits 146
Detection (Sign function) circuit 147
QRS-complex wavelet detection using CFOS 150
Filtering stage - CFOS wavelet filter 151
Decision stage - absolute value and peak detector circuits 153
Measurement results 154
Wavelet filter designs 159
Gaussian filters 159
Optimized Padé implementation using DTL circuits ISCAS2004Haddad 160
L2 approximation employing CMOS triode transconductors 164
Complex wavelet filter implementation 166
Circuit design 168
Morlet wavelet filter 170
Circuit design 173
Measurement results of the Morlet wavelet filter 176
Conclusions 179
References 181
Conclusions and Future Research 183
Future research 185
Biomedical applications of wavelets 186
Ultra Wideband Applications 187
High-Performance Analog Delays 188
Bessel-Thomson approximation 188
Padé approximation 189
Comparison of Bessel-Thomson and Padé approximation delay filters 192
Gaussian time-domain impulse-response method 192
Model Reduction - The Balanced Truncation Method 197
Reduced model and optimal dynamic transformations comparison 200
Switched-Capacitor Wavelet Filters 201
Non-inverting and inverting SC integrators 203
Ultra-Wideband Circuit Designs 207
Impulse generator for pulse position modulation 207
A delay filter for an UWB front-end 209
A FCC compliant pulse generator for UWB communications 211
Summary 213
About the Authors 217
Index 219