近年來，由於健康照護逐漸受到重視，生醫訊號感測系統也蓬勃發展。從生醫訊號的擷取到後端的訊號分析都有可觀的人員投入其研究。良好的生醫訊號擷取系統有助於病症的早期檢測、日常健康狀況監測、緊急情況的辨識等。血氧飽和度(SpO2)為使用者血液中帶氧血紅素與不帶氧血紅素所佔有之比例，反映呼吸系統與循環系統的運作，已被廣泛運用於心肺功能與循環系統功能之檢視與監測。
計算血氧飽和度必須取得人體之血液光容積變化波形，此訊號乃是藉由光電二極體(photodiode)接收發光二極體(LED)所發射之光線，由於血液光容積變化波形是基於光感測器所產生之訊號，因此其極易受到動作雜訊(motion artifact)影響，而在接收到的訊號上產生極大的擾動，然而在計算血氧飽和度時血液光容積變化之實際波形並非其重點，訊號的振幅(amplitude)才是關鍵，因此本研究提出了利用傅立葉分析搭配心電訊號以減少動作雜訊干擾血氧飽和度計算之演算法。本研究並開發了血氧飽和度感測系統，包含了血液光容積變化波形感測器、類比訊號處理單元與控制訊號產生單元。而動作雜訊消除以及血氧飽和度計算則是將資料蒐集並數位化後送至電腦中進行。
實驗結果證明了本論文所提出之血氧飽和度感測系統與動作雜訊消除驗算法之可行性與可靠度，於論文最後則提出了未來可改進之方向與發展。

Nowadays, mobile health care has been greatly emphasized. Biomedical signal acquisition techniques developed rapidly over this decade. Blood oxygen saturation (SpO2) is the percentage of oxygenated hemoglobin among total hemoglobin. It reflects the situation of cardio-pulmonary function and is widely used is hospitals.
In this study, a system that records photoplethysmography (PPG) and performs motion artifact reduction is introduced. In order to calculate SpO2, accurate amplitude of PPG is essential. As a matter of fact that the PPG signal is acquired through an optical sensor, it is prone to be affected by motion artifact. As a result, noise cancellation is a major issue in the calculation of SpO2. When computing SpO2, the exact waveform is not the key point, whereas the amplitude plays the important role. Therefore, Fourier analysis with ECG signal is adopted to perform the noise cancellation. In the proposed system, data acquisition and analog filtering is done on a printed circuit board (PCB) controlled by an FPGA. The acquired data are sent to a computer, where Fourier analysis is done to cancel motion artifact. Experiments have been done to demonstrate the performance of the proposed algorithm. The proposed system performs PPG signal acquisition, motion artifact reduction and SpO2 calculation.

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