小體積、低功率與可穿戴式的生理訊號量測系統中，其前端放大器需要有相當高的共模斥拒比來消除雜訊的干擾，並且也需要有可以調整增益的功能，使訊號有適當準位大小給類比對數位轉換器去做轉換。本篇論文實現了由微控制器控制的雙差動放大器記錄系統，其具有增益與平衡方面自動調整控制的兩種功能，這兩種功能可以調整被量測到的生理電位來達到符合適當大小的準位，在不需要使用濾波器的情況下，也有全頻段上的雜訊消除功能。藉由微控制器來實現增益與平衡上的控制方法，經由偵測、運算與改變參數來設定時脈訊號的時間，時脈訊號能決定增益大小與平衡的情況。自動平衡控制功能解決了由輸入電極介面阻抗所造成的不匹配效應。雙差動放大器由兩個可變增益的放大器與一個加法器所實現，其中可變增益放大器製作封裝在台積電0.35微米製程裡，其量測結果顯示雜訊大小為169 nV/√Hz與NEF低於10,面積為0.017 mm2，功率為1.44 μW。在±10%不匹配的輸入情況下，雙差動放大器記錄系統的量測結果其具有25.7 dB的雜訊抑制能力，39.6 dB的可調增益範圍，239 nV/√Hz的輸入雜訊，在實際的量測中包含了ECG與EMG的實際量測，在此量測下顯示其具有雜訊抑制效果，也適合用在生理電位量測上。

Low size, low power, and wearable bio-signal recording systems require acquisition front-ends with high common-mode rejection for interference suppression and adjustable gain to provide an optimum signal level to a cascading analog-to-digital stage. This thesis presents the realization of microcontroller operated double-differential (DD) recording setup with automatic gain control (AGC) and automatic balance control, which can adjust the magnitude of recorded bio-potential signal to a target level and reject common-mode interference for full-bandwidth recording without filtering. Microcontroller code realizes the automatic control method of gain and balance adjustment by detecting, computing, and varying parameters to set timing clock pulses, which determine the gain magnitude and balance state. The automatic balance control compensates for imbalance in electrode interface impedance. The double-differential amplifier is implemented using two integrated variable gain amplifiers (ASIC) and one adder. Measured results of the variable gain amplifiers fabricated in 0.35 μm CMOS technology show an input spot noise of 169 nV/√Hz, a NEF below 10, and a circuit active area of 0.017 mm2 with a power consumption of 1.44 μW. Measured results of the double-differential amplifier setup confirm interference suppression of 25.7 dB, tunable gain range of 39.6 dB, and 239 nV/√Hz noise assuming ±10% interface mismatch. Practical measured examples incorporating the chips confirm gain control suitable for bio-potential recording and interference suppression in a balanced DD arrangement for electrocardiogram and electromyogram recording.

致謝............................................................................................................................... i
摘要............................................................................................................................... ii
Abstract......................................................................................................................... iii
Contents........................................................................................................................ v
List of Figures................................................................................................................ viii
List of Table................................................................................................................... xiii
Chapter 1 Introduction................................................................................................... 1
1.1 Motivation ....................................................................................................... 1
1.2 Thesis organization.......................................................................................... 4
Chapter 2 Bio-signal recording system.......................................................................... 5
2.1 Typical bio-signals........................................................................................... 5
2.2 Bio-signal recording system............................................................................ 6
2.3 Architecture of single amplifier and double-differential amplifier.................. 8
2.4 Interference analysis of single amplifier and double-differential amplifier..... 9
Chapter 3 Implementation of double-differential recording with gain and balance control………………………………………………………………….......... 15
3.1 Variable gain amplifier (VGA) ....................................................................... 15
3.2 Summation circuit............................................................................................ 18
3.3 Generation of control signals for double-differential amplifier using a microcontroller............................................................................................... 19
3.4 Automatic gain control (AGC) implementation.............................................. 21
3.5 Automatic balance control implementation..................................................... 24
3.6 Simultaneous gain and balance control………………………………………27
Chapter 4 Simulated results........................................................................................... 31
4.1 Simulation of double-differential amplifier and single amplifier…………… 31
4.2 Simulation of automatic gain control (AGC)……………………………….. 36
4.3 Simulation of automatic balance control……………………………………. 38
4.4 Simulation of double-differential amplifier with simultaneous gain and balance control…………..………………………………………………………….. 40
Chapter 5 Measured results........................................................................................... 43
5.1 Testing circuit board………………………………………………………… 43
5.2 Measurement of variable gain control (VGA)……………………………… 43
5.3 Integrated clock generator…………………………………………………... 44
5.4 Measurement of double-differential amplifier and single amplifier………… 49
5.5 Measurement of automatic gain control (AGC)…………………………….. 54
5.6 Measurement of automatic balance control…………………………………. 57
5.7 Measurement of double-differential amplifier with simultaneous gain and balance control....………………………………..…………………………... 59
5.8 Performance comparison of double-differential amplifier and single amplifier.. ……..………………………………………………………………………... 61
Chapter 6 Conclusion and future work……………………………………………….. 63
6.1 Conclusion…………………………………………………………………... 63
6.2 Future work………………………………………………………………….. 64
Reference……………………………………………………………………………... 65

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