Vital Signs Detection Based on High-Resolution 3-D mmWave Radar Imaging

In this paper, a novel low-power millimeter wave (mmWave) multiple-input multiple-output (MIMO) radar with 20 transmitters (Tx) and 20 receivers (Rx) successfully demonstrates short-range high resolution human body imaging and accurate vital signs detection, including heart rate and breathing rate estimation of multiple subjects at one time. This mmWave MIMO radar system synthesizes wide band signal with stepped-frequency-modulated-continuous-wave (SFCW). Due to the increased degrees of freedom, 3-D high resolution images of the environment can be formed. With this image precise body part locations can be obtained. The human chest is chosen from the image and isolated as the target for beamforming. Vital signs parameters are estimated from the recovered phase variation at the maximum range response after beamforming. Coherently combining spatial channels significantly enhance the vital signs detection performance compared that of using a single Tx/Rx pair (single channel). Experiment demonstration on human subjects shows that the estimated breathing rate and heart rate from the mmWave MIMO system match the ground truth from the contact sensors.