A preliminary study on photoplethysmogram (PPG) signal analysis for reduction of motion artifact in frequency domain

In this study, we analyzed frequency characteristics of photoplethysmogram (PPG) signal to improve the accuracy of SpO₂ by reducing the motion artifacts. 23 kinds of different signals generated by SpO₂ test equipment were used for this analysis. The results of analysis showed that most of PPG signals analyzed in this study consisted of the fundamental, 2^nd and 3^rd harmonic components caused by arterial blood flow and component caused by motion artifact. The result also showed the relative magnitudes of its three frequency components. The signals could be divided into four groups based on the relative locations of these frequency components. But four different algorithms would be required to discriminate the signal and motion artifact frequency components.