Heart Rate Variability Monitoring Using a Chord-Based Algorithms in Low-If Cw Radar Systems

This paper presents a method for accurate noncontact heart rate variability (HRV) monitoring using low-IF continuous wave radar under low SNR conditions. The approach integrates a noise-immune motion sensing (NIMS) technique to enhance SNR by segmenting IF signals, extracting phase information, and reconstructing phase evolution for displacement motion. While effective, NIMS faces challenges with small-amplitude cardiac signals due to limitations of traditional phase demodulation. To overcome this, a chord-based phase demodulation method is introduced, offering dc offset immunity and robust noise resistance. Experimental results demonstrate strong agreement with reference ECG, achieving a 6.45 % average error rate, highlighting its effectiveness in challenging conditions.