EBOOK - Wakeup Receiver Based Ultra Low Power WBAN - Analog Circuits and Signal Processing (Maarten Lont & Dusan Milosevic & Arthur van Roermund)
10 thg 11, 2016 | 14:10

EBOOK - Wakeup Receiver Based Ultra Low Power WBAN - Analog Circuits and Signal Processing (Maarten Lont & Dusan Milosevic & Arthur van Roermund)


Wireless body area networks (WBAN) need to operate on small batteries or energy harvesters for a long time. At the same time it is impossible to replace the batteries on a regular basis.
Therefore, the sensors need to have very low power consumption. The overall power consumption is reduced by placing the sensor node in sleep mode as often and long as possible. It listens for a wake-up call transmitted by the network coordinator, and wakes up the rest of the node when needed. The book targets the design of the wake-up receiver. To minimize the power consumption it needs to be optimized for the WBAN applications.
A lot of research is done in the areas of network and system design of wireless body area networks on one hand and low-power receiver circuit design on the other hand. This book presents the cross-layer design and optimization of wake-up receivers for wireless body area networks (WBAN), with an emphasis on lowpower circuit design. This includes the analysis of medium access control (MAC)
protocols, mixer-first receiver design, and implications of receiver impairments on wideband frequency-shift-keying (FSK) receivers.

The overall power consumption is reduced by exploiting the characteristics of body area networks. Specifically, the power consumption of FSK wake-up receivers is reduced by exploiting wideband FSK modulation, removing the LNA from the receiver chain and exchanging the ubiquitous PLL for the low-power automatic frequency control (AFC) loop.
Within this book these effects are analyzed in-depth and validated by CMOS implementations. The reader will get an overview of wireless body area network design from the network layer to the circuit implementation, and an overview of the cross-layer design trade-offs. Furthermore, the mixer-first receiver topology is analyzed and the implications of receiver impairments are analyzed. The theory is validated by two different receiver implementations, one in 90 nm and one in 40 nm CMOS technology. Moreover, the book gives a good overview of state-of-the-art wakeup-receiver research.

1 Introduction ........................................ 1
1.1 Wake-Up Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Wake-Up Receiver Challenges . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Scope of the Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4 Book Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Wireless Body Area Networks........................... 7
2.1 Wireless Sensor Network Properties . . . . . . . . . . . . . . . . . . . . 7
2.2 MAC Layer Energy Consumption Model . . . . . . . . . . . . . . . . . 8
2.2.1 Address Coding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.2 Radio Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2.3 Network Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.4 WURx-Enhanced Asynchronous Network . . . . . . . . . . . 16
2.2.5 WURx-Less Asynchronous Network . . . . . . . . . . . . . . . 18
2.2.6 Synchronous Network . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2.7 Application Example . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.3 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.4 Solution Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3 Wake-up Receiver System Level Design.................... 29
3.1 State of the Art . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.2 Modulation Complexity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.3 Zero-IF Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.4 FSK Receiver Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.4.1 Non-ideal Receiver Front-End . . . . . . . . . . . . . . . . . . . 34
3.4.2 Receiver Phase Noise and Jitter . . . . . . . . . . . . . . . . . . 35
3.4.3 Limiter Discriminator Model . . . . . . . . . . . . . . . . . . . . 37
3.5 Effects of Receiver Imperfections on FSK BER . . . . . . . . . . . . 38
3.5.1 Bit Error Rate Analysis . . . . . . . . . . . . . . . . . . . . . . . . 39
3.5.2 Simulation and Model Results . . . . . . . . . . . . . . . . . . . 50
3.6 Wake-up Receiver Specifications. . . . . . . . . . . . . . . . . . . . . . . 54
3.6.1 Interferer Robustness . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.6.2 Sensitivity and Noise Figure. . . . . . . . . . . . . . . . . . . . . 55
3.6.3 Phase Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4 Low-Power Zero-IF Receiver Design ...................... 61
4.1 Passive Mixer-First Design . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.1.1 Time-Domain Passive Mixer Model . . . . . . . . . . . . . . . 62
4.1.2 Voltage Conversion Gain . . . . . . . . . . . . . . . . . . . . . . . 66
4.1.3 Input Impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.1.4 Transducer Power Gain . . . . . . . . . . . . . . . . . . . . . . . . 71
4.1.5 Maximal Transducer Power Gain . . . . . . . . . . . . . . . . . 71
4.1.6 Noise Figure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
4.1.7 Optimal Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
4.2 Low-Power Local Oscillator Design . . . . . . . . . . . . . . . . . . . . 77
4.2.1 Oscillator Design Considerations for Minimum Power. . . 77
4.2.2 LC Oscillator Design. . . . . . . . . . . . . . . . . . . . . . . . . . 78
4.2.3 Ring Oscillator Design . . . . . . . . . . . . . . . . . . . . . . . . 79
4.2.4 LC and Ring Oscillator Design Approach . . . . . . . . . . . 81
4.2.5 LC Versus Ring Oscillators . . . . . . . . . . . . . . . . . . . . . 82
4.3 FSK Demodulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
4.4 Automatic Frequency Control Loop . . . . . . . . . . . . . . . . . . . . . 86
4.4.1 Closed Loop Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 87
4.4.2 System Level Implications . . . . . . . . . . . . . . . . . . . . . . 89
4.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
5 Receiver Front-End Version 1........................... 93
5.1 Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
5.1.1 Mixer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
5.1.2 Local Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
5.1.3 IF Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
5.2 Measurement Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
5.2.1 LO Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
5.2.2 Amplifier Measurements . . . . . . . . . . . . . . . . . . . . . . . 101
5.2.3 Receiver Front-End Measurements . . . . . . . . . . . . . . . . 102
5.3 Comparison with Literature . . . . . . . . . . . . . . . . . . . . . . . . . . 103
5.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
6 Receiver Front-End Version 2........................... 109
6.1 Design Targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
6.2 Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
6.2.1 Passive Mixer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
6.2.2 Local Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
6.2.3 Variable Gain Amplifier . . . . . . . . . . . . . . . . . . . . . . . 113
6.2.4 Demodulator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
6.2.5 Automatic Frequency Control Loop . . . . . . . . . . . . . . . 116
6.3 Receiver Front-End Measurements. . . . . . . . . . . . . . . . . . . . . . 120
6.3.1 DCDM Demodulator . . . . . . . . . . . . . . . . . . . . . . . . . . 122
6.3.2 DCO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
6.3.3 Bit Error Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
6.3.4 Blocker Rejection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
6.3.5 AFC Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
6.4 Comparison with Literature . . . . . . . . . . . . . . . . . . . . . . . . . . 130
6.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

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Wireless body area networks (WBAN) need to operate on small batteries or energy harvesters for a long time. At the same time it is impossible to replace the batteries on a regular basis.
Therefore, the sensors need to have very low power consumption. The overall power consumption is reduced by placing the sensor node in sleep mode as often and long as possible. It listens for a wake-up call transmitted by the network coordinator, and wakes up the rest of the node when needed. The book targets the design of the wake-up receiver. To minimize the power consumption it needs to be optimized for the WBAN applications.
A lot of research is done in the areas of network and system design of wireless body area networks on one hand and low-power receiver circuit design on the other hand. This book presents the cross-layer design and optimization of wake-up receivers for wireless body area networks (WBAN), with an emphasis on lowpower circuit design. This includes the analysis of medium access control (MAC)
protocols, mixer-first receiver design, and implications of receiver impairments on wideband frequency-shift-keying (FSK) receivers.

The overall power consumption is reduced by exploiting the characteristics of body area networks. Specifically, the power consumption of FSK wake-up receivers is reduced by exploiting wideband FSK modulation, removing the LNA from the receiver chain and exchanging the ubiquitous PLL for the low-power automatic frequency control (AFC) loop.
Within this book these effects are analyzed in-depth and validated by CMOS implementations. The reader will get an overview of wireless body area network design from the network layer to the circuit implementation, and an overview of the cross-layer design trade-offs. Furthermore, the mixer-first receiver topology is analyzed and the implications of receiver impairments are analyzed. The theory is validated by two different receiver implementations, one in 90 nm and one in 40 nm CMOS technology. Moreover, the book gives a good overview of state-of-the-art wakeup-receiver research.

1 Introduction ........................................ 1
1.1 Wake-Up Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Wake-Up Receiver Challenges . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Scope of the Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4 Book Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Wireless Body Area Networks........................... 7
2.1 Wireless Sensor Network Properties . . . . . . . . . . . . . . . . . . . . 7
2.2 MAC Layer Energy Consumption Model . . . . . . . . . . . . . . . . . 8
2.2.1 Address Coding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.2 Radio Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2.3 Network Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.4 WURx-Enhanced Asynchronous Network . . . . . . . . . . . 16
2.2.5 WURx-Less Asynchronous Network . . . . . . . . . . . . . . . 18
2.2.6 Synchronous Network . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2.7 Application Example . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.3 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.4 Solution Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3 Wake-up Receiver System Level Design.................... 29
3.1 State of the Art . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.2 Modulation Complexity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.3 Zero-IF Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.4 FSK Receiver Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.4.1 Non-ideal Receiver Front-End . . . . . . . . . . . . . . . . . . . 34
3.4.2 Receiver Phase Noise and Jitter . . . . . . . . . . . . . . . . . . 35
3.4.3 Limiter Discriminator Model . . . . . . . . . . . . . . . . . . . . 37
3.5 Effects of Receiver Imperfections on FSK BER . . . . . . . . . . . . 38
3.5.1 Bit Error Rate Analysis . . . . . . . . . . . . . . . . . . . . . . . . 39
3.5.2 Simulation and Model Results . . . . . . . . . . . . . . . . . . . 50
3.6 Wake-up Receiver Specifications. . . . . . . . . . . . . . . . . . . . . . . 54
3.6.1 Interferer Robustness . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.6.2 Sensitivity and Noise Figure. . . . . . . . . . . . . . . . . . . . . 55
3.6.3 Phase Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4 Low-Power Zero-IF Receiver Design ...................... 61
4.1 Passive Mixer-First Design . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.1.1 Time-Domain Passive Mixer Model . . . . . . . . . . . . . . . 62
4.1.2 Voltage Conversion Gain . . . . . . . . . . . . . . . . . . . . . . . 66
4.1.3 Input Impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.1.4 Transducer Power Gain . . . . . . . . . . . . . . . . . . . . . . . . 71
4.1.5 Maximal Transducer Power Gain . . . . . . . . . . . . . . . . . 71
4.1.6 Noise Figure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
4.1.7 Optimal Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
4.2 Low-Power Local Oscillator Design . . . . . . . . . . . . . . . . . . . . 77
4.2.1 Oscillator Design Considerations for Minimum Power. . . 77
4.2.2 LC Oscillator Design. . . . . . . . . . . . . . . . . . . . . . . . . . 78
4.2.3 Ring Oscillator Design . . . . . . . . . . . . . . . . . . . . . . . . 79
4.2.4 LC and Ring Oscillator Design Approach . . . . . . . . . . . 81
4.2.5 LC Versus Ring Oscillators . . . . . . . . . . . . . . . . . . . . . 82
4.3 FSK Demodulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
4.4 Automatic Frequency Control Loop . . . . . . . . . . . . . . . . . . . . . 86
4.4.1 Closed Loop Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 87
4.4.2 System Level Implications . . . . . . . . . . . . . . . . . . . . . . 89
4.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
5 Receiver Front-End Version 1........................... 93
5.1 Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
5.1.1 Mixer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
5.1.2 Local Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
5.1.3 IF Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
5.2 Measurement Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
5.2.1 LO Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
5.2.2 Amplifier Measurements . . . . . . . . . . . . . . . . . . . . . . . 101
5.2.3 Receiver Front-End Measurements . . . . . . . . . . . . . . . . 102
5.3 Comparison with Literature . . . . . . . . . . . . . . . . . . . . . . . . . . 103
5.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
6 Receiver Front-End Version 2........................... 109
6.1 Design Targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
6.2 Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
6.2.1 Passive Mixer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
6.2.2 Local Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
6.2.3 Variable Gain Amplifier . . . . . . . . . . . . . . . . . . . . . . . 113
6.2.4 Demodulator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
6.2.5 Automatic Frequency Control Loop . . . . . . . . . . . . . . . 116
6.3 Receiver Front-End Measurements. . . . . . . . . . . . . . . . . . . . . . 120
6.3.1 DCDM Demodulator . . . . . . . . . . . . . . . . . . . . . . . . . . 122
6.3.2 DCO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
6.3.3 Bit Error Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
6.3.4 Blocker Rejection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
6.3.5 AFC Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
6.4 Comparison with Literature . . . . . . . . . . . . . . . . . . . . . . . . . . 130
6.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

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