心電圖儀中電流式濾波電路之改良

Improvement of Current-Mode Filter Structures in Cardiograph

林峰守(Feng-Shou Lin)

指導教授 ： 張俊明

中原大學/工學院/電機工程研究所/碩士(2010年)

https://doi.org/10.6840/cycu201000355

摘要

摘 要

本論文的研究方向主要是利用運算轉導放大器(Operational Transconductance Amplifier , OTA)與電容器(C)所設計類比濾波電路，改良目前在心電圖儀中，以運算放大器(Operational Amplifier , OA)為主動元件所設計的濾波電路，以提供更好的濾波效果。主要因為在類比電路設計領域中，由於分析合成法(Analytical Synthesis Method)的提出，使得以運算轉導放大器與電容器(OTA-C)為主要架構之濾波電路同時具備了以下優點：(1)所有的OTA元件均為單端點接地輸入(可免除寄生電容的Feed-through效應)，(2)使用接地電容(可直接吸收寄生電容)，(3)使用最少的主動、被動元件，而將電路的寄生效應減至最低，進而大幅提高電路輸出訊號的精準度。
在第二章、第三章中分別介紹目前心電圖儀中，以運算放大器為主動元件之低通濾波器(Lowpass Filter)、高通濾波器(Highpass Filiter)及帶拒濾波器(Notch filter)架構，並在第四章提出以OTA為主動元件所提出相對應之電流式橢圓濾波器的改良。在OA模擬方面，是以Sallen-key 低通與高通濾波電路，-3dB頻率點分別為155.952Hz 與 52.8mHz；在Twin-T帶拒濾波電路部分，截止頻率介於24.4Hz~142.4Hz，寬度為118Hz。而在OTA改良是以電流式橢圓濾波電路實現低通、高通及帶拒濾波器。在低通濾波電路模擬中，截止頻率為149.9788Hz，誤差百分比為0.01%；在高通濾波電路模擬中，截止頻率為50.0069mHz，誤差百分比為0.01%；在帶拒濾波電路模擬中，截止頻率介於55.7Hz~64.8Hz，寬度為9.1Hz。根據美國心臟學會建議心電頻率介於50mHz~150Hz，以及市電所造成干擾介於59.41Hz~60.51Hz，改良後的濾波電路確實可得到較佳的效果。最後在第五章中做信號精準度與電路敏感度之比較。
本論文所提出的電路均以HSPICE軟體做為實際驗證的模擬工具，所使用製程參數均為TSMC035μm，並於實際模擬結果與理論之間相互得到驗證。未來在實際運用上均有很大的發展空間。

關鍵字

運算轉導放大器 ； 心電圖儀 ； 濾波器

並列摘要

Abstract

The design of active filter circuit by Operational Transconductance Amplifier (OTA) and Capacitor (Cs) has better performance than Operation Amplifier (OA) , in filter circuit of Cardiograph . That’s because the appearance of “Analytical Synthesis Method” has enhanced the function of OTA and Capacitor as (i) all of OTAs are single-end-input (ii) all capacitors are grounded and (iii) least main and passive components are involved to reduce the parasitic effect of circuit and enhance the accuracy of circuit output by a wide margin .
Introducing the Lowpass filter (LPF) , Highpass filter (HPF) and Notch filter by OA in cardiograph in Chapter 3 and Chapter 4 , and describing the improvement of current-mode elliptic filter by OTA in Chapter 5 . About Sallen-key high-pass and low-pass filter simulation by OA . -3dB points in frequency are 155.952Hz in low-pass filter and 52.8mHz in high-pass filter , the stop band between 24.4Hz and 142.4Hz in Twin-T notch filter . About the simulation of current-mode elliptic filter by OTA , the cutoff points in frequency of low-pass is 149.9788Hz and 50.0069mHz in high-pass filter . The stop band between 55.7Hz and 64.8Hz in notch filter . According to “American Heart Association” proposes , the frequency range of electrocardiogram(ECG) is 50mHz~150Hz , and according to the noise range from power line is 59.49Hz~60.51Hz in Taiwan . The performance of filter by OTA is better than OA .
Comparing the accuracy of signals and the sensitivity of circuits in Chapter 6 .Finally , the H-spice simulation with TSMC035μm process verifies the theoretical accuracy .

並列關鍵字

ECG ； filter ； OTA

參考文獻

[28] 基本心電圖圖例簡介，達楷生醫科技股份有限公司。

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[2] C. M. Chang; Al-Hashimi, B. M. “Analytical Synthesis of Current

[3] C. M. Chang; Al-Hashimi, B.M. “Analytical Synthesis of voltage mode OTA-C all-pass filters for high frequency operation”, ISCAS Circuits and Systems, 25-28 pp. I-461 - I-464 vol. 1 May 2003.

[4] C. M. Chang; Al-Hashimi, B.M. “New high-order filter structures using only single-ended-input OTAs and grounded capacitors”, IEEE transactions on circuit and systems-II, vol. 51, pp. 458-463, Sept. 2004.