Monitoring Long-term Cardiac Activity with Contactless Radio Frequency Signals

Cardiovascular diseases claim over 10 million lives annually, highlighting the critical need for long-term monitoring and early detection of cardiac abnormalities. Existing techniques like electrocardiograms (ECG) and Holter are accurate but suffer from discomfort caused by body-attached electrodes. While wearable devices using photoplethysmography offer more convenience, they sacrifice accuracy and are susceptible to environmental interference. Here we present a radio frequency (RF)-based sensing system that monitors long-term heart rate variability (HRV) with clinical-grade accuracy. For the first time, our system successfully overcomes the orders-larger interference from respiration motion by overturning the conventional signal processing framework. By identifying previously undiscovered frequency ranges where heartbeat information predominates over other motions, we generate prominent heartbeat patterns with harmonics typically considered detrimental. Extensive evaluations, including a large-scale clinical setting involving 7,090 participants and a long-term daily scenario spanning two months, demonstrate that our system can monitor HRV and diagnose abnormalities with comparable performance to clinical-grade ECG-based systems. This RF-based HRV sensing system has the potential to support active self-assessment and revolutionize medical prevention with long-term and precise health monitoring.