Improved Contactless Heartbeat Estimation in FMCW Radar via Kalman Filter Tracking

Radar systems enable a contactless, noninvasive method to simultaneously monitor the respiration and heart rate of a human target. To enhance the stability and accuracy of the detected heart rate, this letter introduces a Kalman filter-based tracking of the heartbeat signal. After providing a first rough estimation, the bandwidth of the applied band-pass filter is successively narrowed down, and the filter limits are steadily updated with respect to the current heart rate of the target. Measurement segments with random body movements are automatically identified and consequentially ignored for the Kalman filter update. The functionality of the proposed algorithm is proven by various verification measurements using a 60-GHz frequency-modulated continuous-wave radar system. The determined heart rates are compared to the output of a commercial chest belt. Measurement data with common breathing, as well as during breath-holding, were recorded for 14 different subjects.