Zero Phase Filter Design and System Study for Improved Handling of ankle PPG Signals

ABSTRACT

One of the areas of steady interest in modern society is health. In addition, in order to keep the individual's health at its best, the healthcare device market is undergoing many trials and developments. The latest threat to COVID-19 is a major threat to heart disease patients, and it is time for continuous monitoring technology to be needed to prevent it. In particular, PPG sensor technology is relatively commercialized amid various attempts to analyze cardiovascular conditions. In general, we prefer to measure signals from fingers and wrists, which have a stable advantage in obtaining signals. However, there are cases where it is not suitable for the user's lifestyle, which creates inconvenience. In this study, signal is measured from the ankles to minimize the inconvenience that users may experience when wearing them. And IIR Filter is applied for stable signal acquisition and analysis. Phase Delay, one of the disadvantages of this, is an unnecessary factor in real-time analysis. Zero Phase Filter is designed and applied to the system for further signal analysis. The results of the study compared three types of raw data, IIR Filter data, and Zero Phase Filter data acquired from PPG sensors, and were able to confirm the tendency of Zero Phase Filter data to match the peak points of raw data relative to IIR Filter data. The above results indicate the tendency for in-depth analysis of signals free from Phase Delay in the real-time acquisition of ankle PPG signals. Through peak-to-peak analysis and deep development of algorithms, various applications are expected to be possible by designing stress estimation and fatigue estimation systems that do not constrain users' upper bodies. © 2021 Korean Institute of Electrical Engineers. All rights reserved.