使用穿戴式紡織感測器量測呼吸訊號之一新電路設計

Abstract

本論文提出一新的電路設計以使用穿戴式紡織電極(Wearable Sensor)設計一量測呼吸訊號電路。基本觀念是呼吸時會造成胸部的起伏而這胸腔起伏的變化，就造成感測器與身體之間的電容變化，所以只要設計電路量測到電容的變化，即可量測到呼吸訊號。傳統的量測方法是基於AM(Amplitude Modulation)的觀念設計電路，即使用振幅的變化去對應呼吸的變化。本論文提出一新的設計是使用FM(Frequency Modulation)的觀念去設計電路，即使用頻率的變化去對應呼吸的變化。 本論文在實現上，我們使用了IC 555振盪電路，其振盪頻率隨兩個感測器電極與身體之間的電容變化而變，然後利用PLL鎖相迴路去判斷頻率的變化。最後，全部的電路將以數位的方式呈現，因此很容易實現。更值得注意的是，測量呼吸信號可以很容易地進一步用於測量呼吸頻率。

This thesis presents a new circuit design for measuring the respiratory signal via wearable textile sensor electrodes. The basic idea is that the capacitance value between two sensor electrodes varies in corresponding with the respiratory signals because breathing causes the ups and downs of the thorax. Hence, a circuit which can measure capacitance variations can indirectly measure the respiratory signals. Conventional respiratory circuit design is based on the concept of AM (Amplitude Modulation) such that the amplitude varies in corresponding with the breathing. This thesis presents a new design which is based on the concept of FM (Frequency Modulation) such that the frequency varies in corresponding with the breathing. For realization, in this thesis, we use an IC 555’s oscillator circuit whose oscillation frequency varies with the capacitor between two sensor electrodes. Then a PLL (phase-locked loop) circuit is designed to estimate the frequency variations. The whole circuits are operated in a digital manner and hence it is simple for implementation. Note that the measured respiratory signals can be easily further used for measuring the respiratory rate.