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橢圓帶拒濾波電路。這個橢圓濾波電路的設計特色是採用將一個二階橢圓濾波電路的轉移函數經由頻率轉換,s→1/Q(s+1/s) ,得到一個四階橢圓帶拒濾波電路的轉移函數。所設計的電路採用電流式的電路,電路的設計使用了六個單端接地的運算轉導放大器(OTAs)及四顆接地電容器。TSMC 0.35μm level-49 H-spice模擬結果得到所設計的橢圓帶拒濾波信號的頻帶寬相當窄,只從58.727赫茲到61.816赫茲 (即3.089赫茲的頻帶寬),中心頻率的最小值也相當低,只有0.0357。
In this paper, an elliptic 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 6 single-ended-input OTAs and 4 grounded capacitors, an elliptic current-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 58.727Hz to 61.816Hz (only 3.089Hz width) and the lowest value at center frequency is only 0.0357.