在量測生醫訊號過程中容易產生難以避免的60赫茲的雜訊，通常來自於傳輸線受到外界電磁波的干擾以及電極貼片因接觸媒介不同、老舊或鬆脫等因素。我們因而提出了一種架構是藉由偵測雜訊大小來調整電位器並消除兩電極貼片匹配不平衡的問題。使用一顆放大器晶片以及自製的三個電極貼片來量測生醫訊號，電極貼片的製作是使用銅箔貼片包覆一元硬幣並與單芯導線焊接。在偵測部分，使用格策爾演算法針對60赫茲的雜訊進行偵測，而這個演算法屬於針對單一頻率做計算，相較於快速傅立葉轉換需要計算所有頻率顯得更有效率，並利用欠採樣技巧，使採樣頻率低於奈奎斯定理，降低運算的時間與功耗。使用雙邊數位電位器，直接以微控制器進行控制調整。量測的波形圖透過LabVIEW 紀錄並使用Matlab重新繪製。透過演算法在微控制器的計算結果先將雜訊分成不同等級，我們以實驗結果定義合理的範圍區間解決因相位偏移所造成的不穩定，並以此為依據調整數位電位器以達到自動偵測與調整至匹配平衡的目的。此設計包含一顆放大器、兩顆微控制器及數位電位器的總功耗為18.36mW。

To solve one of the major problems in recording biopotentials, which is the unwanted 60Hz interference produced by power line, an automatically adjusting resistors design is proposed. Three custom made electrodes composed of three copper coins covered by copper sheet, and a custom-design amplifier (ASIC) are used as a part of the recording setup. Goertzel algorithm and undersampling are implemented to detect interference. They save power compared to Fast Fourier Transform (FFT) for interference detection and a reduced sample rate from 121Hz to 80Hz. Off-the-shelf dual SPI digital potentiometers with 0 to 10kΩ tuning range are used to offset the imbalance of impedance from electrodes. A microcontroller operates the Goertzel algorithm and the dual potentiometers. Continuously detecting the interference level by Goertzel algorithm, the dual potentiometers keep adjusting the value until the impedance balance is achieved. A demonstrator setup is produced and tested on the bench. The testing waveform is recorded by Labview and evaluated by Matlab. The prototype consumes 18.36mW, including amplifiers, two microcontrollers, and dual digital dual potentiometers.

Contents
摘要 i
Abstract ii
Contents iii
List of Figure v
List of Tables viii
Chapter 1. Introduction 1
1.1 Motivation 1
1.2 Double Differential Model 3
1.3 Goertzel Algorithm 7
Chapter 2. Algorithm Design 11
2.1 Selection of fs and N 11
2.2 Coding Structure in Software 16
2.3 Overflow Problem 20
2.4 Phase Shift Problem 24
Chapter 3. Microcontroller Implementation 26
3.1 ADC 26
3.2 DAC 27
3.3 Goertzel Algorithm 28
3.4 Dual Potentiometers 32
3.5 Automatic Interference Detection 40
Chapter 4. Measurement and Result 49
4.1 Testing Equipment 49
4.2 Measurement 52
4.3 Result 56
Chapter 5. Conclusion and Future Work 59
References 60
Similarity report 62

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