Noncontact Vital Sign Monitoring Using Radar Technologies

Noncontact vital sign monitoring using radar leverages the reflection of electromagnetic waves to detect minute physiological movements associated with respiration, heartbeat and cardiac acoustic phenomena. Typical systems employ Doppler or ultra-wideband architectures, including continuous-wave, frequency-modulated continuous-wave (FMCW) and impulse-radio ultra-wideband designs, to capture phase and amplitude variations induced by chest-wall displacement. Advances in antenna design and front-end integration have enabled compact, low-power sensors suitable for in-home, clinical and automotive environments. Cutting-edge signal-processing techniques, ranging from adaptive clutter cancellation to machine-learning-based feature extraction, address challenges of motion artefacts, multipath interference and multi-subject discrimination. The resulting modalities permit unobtrusive, long-term tracking of respiratory rate, heart rate and even heart sounds, offering significant potential for telemedicine, sleep monitoring and early detection of cardiopulmonary disorders.

Research from Nature Portfolio

Recent studies have demonstrated radar-based heart sound detection via continuous-wave radars, enabling touch-free phonocardiography with high correlation to acoustic measures and F1 scores exceeding 90 %. Semi-Markov models coupled with template matching have refined the identification of S1 and S2 heart sounds, reducing timing errors below 50 ms. Additional work using impulse-radio ultra-wideband radar has validated noncontact assessment of heart rate and rhythm even in arrhythmias, achieving intraclass correlations above 0.85 for rate and R-R interval metrics. These foundational demonstrations have confirmed the precision and clinical feasibility of radar sensors for comprehensive cardiac monitoring.

Noncontact Vital Sign Monitoring Using Radar Technologies publication trend

The graph below shows the total number of articles in noncontact vital sign monitoring using radar technologies across all publications each year (not limited to Nature Index journals).

Technical terms

Doppler radar: Radar that detects motion by measuring frequency shifts induced by target movement.

Frequency-Modulated Continuous-Wave (FMCW) radar: Radar that sweeps frequency to determine range and velocity simultaneously.

Impulse-Radio Ultra-Wideband (IR-UWB) radar: Radar transmitting short, low-power pulses across a wide spectrum for fine resolution.

Micro-Doppler signature: Subtle time-varying frequency shifts caused by small periodic motions of a target.

Compressive sensing: Reconstruction of sparse signals from limited measurements using optimisation algorithms.

Parametric spectral estimation: Model-based technique for estimating frequency content with high resolution from observed data.

Auto-regressive algorithm: Method that models each data point as a linear combination of its predecessors.

References

1. Short-Range Noncontact Sensors for Healthcare and Other Emerging Applications: A Review. Sensors (2016).
2. Radar-Based Heart Sound Detection. Scientific Reports (2018).
3. A Novel Non-contact Heart Rate Monitor Using Impulse-Radio Ultra-Wideband (IR-UWB) Radar Technology. Scientific Reports (2018).
4. Radar-Based Monitoring of Vital Signs: A Tutorial Overview. Proceedings of the IEEE (2023).
5. Remote Monitoring of Human Vital Signs Based on 77-GHz mm-Wave FMCW Radar. Sensors (2020).
6. A Novel Vital-Sign Sensing Algorithm for Multiple Subjects Based on 24-GHz FMCW Doppler Radar. Remote Sensing (2019).