- 學位論文
應用於心電圖儀中60赫茲並聯式帶拒橢圓濾波器
Design of a 60Hz Parallel-type Band-reject Elliptic Filter in ECG
摘要
近年心臟病已成為國人常見十大死因之第二名，而記錄心臟活動的心電圖在擷取訊號時最常見被電源雜訊干擾，為了讓醫療人員能夠確切的診斷出心臟疾病，必須降低雜訊的影響。 本論文主要實現一個電流式四階橢圓帶拒濾波電路，電路設計以減少寄生效應提升精準度為目標。採用「分析合成法(Analytical synthesis methods ; ASM)」，先將橢圓轉移函數以矩陣模式表示，並使用主動元件特性完成矩陣關係式，可精簡電路節點數。電路中的主動元件使用運算轉導放大器(Operational Transconductance Amplifier 簡稱OTA)，由於其輸入點虛接地之特性，可有效減低寄生效應，且具備轉導增益的Gm值為電子可調，設計完成的電路又不需使用電阻器的優點，是目前類比電路設計公認最佳的主動元件之一。 本文所設計的帶拒濾波器是將低通濾波電路聯集高通濾波電路為基礎架構，設計完成的電路以60Hz為操作頻率，並藉由H-SPICE及LM13700製程參數進行模擬與理論驗證。其模擬輸出結果具有四階橢圓帶拒濾波器之特性，並以元件靈敏度傾向，進行電路最佳化情況模擬，使輸出更符合特性且趨於精準。 最後，期待本論文所設計的橢圓帶拒濾波電路能下線實際做成積體電路，以便在實際心電圖儀中使用。
並列摘要
Abstract The ECG signals are easy to be interfered with by the power noises. The power line interference needs to be minimized in order to obtain a clean ECG signal for accurate diagnosis of a heart condition. This brief discusses a current-mode fourth-order elliptic filter, The goal is to reduce the parasitic effects and to obtain an accurate output signal. The experiment used the Analytical Synthesis Method (ASM) for fourth-order elliptic transfer function to design the circuit. It can reduce circuit node numbers, so the parasitic effects can be reduced. The Notch filter can be composed of the Low-pass filter and high-pass filter operated in parallel. We can get the expected result from the designed circuit after the simulation. This experiment used H-spice with LM13700 process to obtain the results. By using MATLAB to document the predictions, we analyzed the sensitivity of the passive elements and made finer output by using passive elements. Finally, we can observe the differences between theoretical parts and simulation parts. For the future research direction, the circuit does well to make an integrated circuit to substantiate 60Hz Notch filter that can be used in the ECG.