心電圖儀中的Chebyshev帶拒濾波電路之設計

本論文旨在提出一個在心電圖儀當中去除在60赫茲附近雜訊的四階Chebyshev帶拒濾波電路。這個Chebyshev濾波電路的設計特色是採用將一個二階Chebyshev低通濾波電路的轉移函數經由頻率轉換，s→1/(Q(s+1/s))，得到一個四階Chebyshev帶拒濾波電路的轉移函數。所設計的電路為電壓式的電路，電路的設計使用了八個單端接地的運算轉導放大器(OTAs)及四個電容器。TSMC 0.35um level-49 H-spice的模擬結果得到所設計的Chebyshev帶拒濾波信號的頻帶寬從59.614赫茲到60.875赫茲(即1.261赫茲的頻帶寬)，中心頻率增益最小值為0.48423。以靈敏度調整的方式使輸出信號更接近理論值，調整後的模擬結果得到的Chebyshev帶拒濾波信號的頻帶寬相當窄，只從59.266赫茲到61.232赫茲(即1.966赫茲的頻帶寬)，中心頻率增益最小值也相當低，只有0.021627。並且完成雜訊模擬，模擬結果在60.256Hz時，雜訊落在2.9888毫伏特。功率耗損模擬得到耗損相當低，只有84.200863503u瓦特。

關鍵字

帶拒濾波電路；低通濾波電路； Chebyshev濾波電路；濾波電路的頻率轉換； ECG

並列摘要

In this paper, a Chebyshev fourth-order band-reject filter used for eliminating the noise near around 60Hz in ECG is proposed. The design scheme is obtained applying the frequency transformation, s→1/(Q(s+1/s)), from a second-order low-pass to a fourth-order band-reject filter transfer function. Only employing 8 single-ended-input OTAs and 4 capacitors, a Chebyshev voltage-mode fourth-order band-reject filter is innovated. TSMC 0.35μm level-49 H-spice simulation results exhibit that the bandwidth of the band-reject signal is located from 59.614Hz to 60.875Hz (only 1.261Hz width) and the voltage gain value at center frequency is 0.48423. we analyzed the sensitivity of the passive elements and made finer output by using passive elements. After adjusting, the bandwidth of the band-reject signal is located from 59.266Hz to 61.232Hz (only 1.966Hz width) and voltage gain the lowest value at center frequency is 0.021627. we done the noise simulation that the result is 2.9888m volts at 60.256Hz. we can get the total voltage source power disspation is 84.200863503u watts that is very low.