Moving Person Vital Sign Detection Using Four-Channel Phase- and Quadrature Self-Injection-Locked Radar and MPCA Method for Dynamic Clutter Immunity

This study used a 2.4 GHz four-channel phase- and quadrature self-injection-locked radar to detect vital signs of a moving person. A modified principal component analysis (MPCA) method was applied to the four-channel data for achieving dynamic clutter immunity. In conventional Doppler-radar-based two-channel IQ demodulation, the subject should be stationary to prevent dynamic clutter from distorting the demodulated signal. By contrast, four-channel data processing together with the MPCA method can be used to obtain two sets of IQ data, which can help suppress dynamic clutter, and the chest motion of a moving person can be accurately recovered for vital sign detection. A two-actuator experiment involving the movement of a metal plate with simultaneous large and small displacements was performed to verify the phase recovery ability of the proposed technique. The vital signs of a person walking for a distance of 1 m toward the radar from a distance of 2 m from the radar could be detected with an error less than 3%.