Monitoring heart activity using continuous wave radar and short-time chirp Z-transform

Abstract

Recently, as smart watches and wristbands have gained popularity, it has become easier to monitor individual physical activities. In particular, as applications have emerged to measure heart rate or an electrocardiogram (ECG) to alert users when cardiovascular disease symptoms occur, their usefulness is gradually being recognized. In general, measuring heart rate or ECG requires a process of acquiring optical or electrical signals through close skin contact. However, if heart activity can be monitored in a non-contact manner, then the discomfort caused by sweating when using the conventional technique can be eliminated. In this study, we propose a method that can measure the heart rate in a non-contact manner using electromagnetic waves. Specifically, heart rate measurement with high accuracy by using a continuous-wave (CW) radar with a small form factor, low power consumption, and low cost is proposed. The one-dimensional CW radar signal is processed into two-dimensional data on the time-frequency plane through short-time chirp Z-transform, and the heart rate is estimated by determining the phase change shape of the radar signal caused by heartbeats. In short, the proposed method can extract the human heart rate in a non-contact manner.