- 學位論文
交流耦合平衡增益之腦波量測系統
Design and Implementation of the AC-coupled EEG Measurement System
摘要
大腦是我們人體重要的思想中樞，裡頭蘊藏許多未知的訊息，而腦部神經活動的綜合變化所產生之電訊號就稱作腦電波。 腦波訊號非常微弱，一般在大腦皮層振幅約為10mV，再經過頭顱等衰減後，其振幅更是小到約0.5～100uV，而且非常容易受到外來因素，如量測環境、周邊電器用品以及人體本身生理訊號的干擾所影響，因此在量測上十分不易。 一般使用腦波擷取電路，容易因為電路元件的誤差或是老化使其濾波效果不盡理想，尤其是針對電源60Hz干擾所設計之陷波濾波器，一旦元件誤差過大其衰減效果就大打折扣。 本研究設計一個雙通道的腦波擷取電路，其中包含交流耦合式前端處理電路，類比放大電路、濾波電路以及陷波濾波器，具有低雜訊、低失真及高增益等特性，對於電路元件誤差所造成之截止頻率的偏移，也可作微調來回到原先的理想設計值，並經由電路模擬與實際量測比較中得到驗證，可有效量得腦波訊號。另外搭配9V電池供應電源，使其攜帶上更方便，並且降低電源干擾。
並列摘要
As a thinking center, the cerebrum plays an important part for human and it’s also abundant with many unknown information. Besides, The signal, the compositive changes produced by cerebration, are called electroencephalogram (EEG). On average, the signal of the EEG is very weak and it’s amplitude is around 10 mV under the cerebrum cortex. After flowing through the skull, the amplitude is reduced to 0.5~100uV. Moreover, it’s easily interfered by external factors such as the environment, the electrical appliance and the physical signal of the body. Hence, it’s extremely hard to measure. Due to the error or the aging of components, EEG access to circuits always leads to unideal filter results. Once the aging of components is overgreat, the decreasing effects will be diminished, notch filter designed by the power 60Hz interference, especially. The study proposes a two-channel EEG measurement, including ac-coupled front-end, amplifier, three order low pass filter and notch filter that possess low noise, low distortion and high gain. With regard to the departure of cut-off frequency cause by the aging, which can be revised to original ideal design by fine-tuning. By the way to compare simulation and measurement, we can get the verification and measure EEG signals efficiently. Conjugation with battery, it’s much easy to carry and decrease power interference.