Multi-person Heartbeat Sensing Using Millimeter-Wave Sensor

This paper presents a millimeter-wave heartbeat sensing technique that enables simultaneous, non-contact measurement of cardiac activity in multiple individuals. The proposed method addresses key challenges for practical implementation—namely, achieving high-precision measurements and expanding the applicability. In previous studies, chest micro-vibrations induced by heartbeats were accurately extracted using a millimeter-wave sensor, and both heart rate and R–R intervals (RRI) were estimated by analyzing these waveforms. However, this approach was primarily limited to single-person monitoring, restricting its applicability in real-world environments. To overcome this limitation, angular separation processing was applied to the intermediate frequency (IF) signals captured by the sensor. This enabled the system to isolate and extract heartbeat signals corresponding to each individual. The proposed method was validated through five-minute experiments involving two participants, demonstrating high-accuracy estimation of heart rates (maximum error below ±6 bpm for both individuals) and RMSSD—an important index for autonomic nervous system analysis (maximum error below ±6.7 ms). These results highlight the potential of this technique for non-contact, high-precision heartbeat sensing in a wide range of healthcare and safety monitoring scenarios.