Appropriate reflected power control for vital signal radar adopting phase shifting method

A study of noncontact vital signal radar adopting the phase shift technique for detecting the target located at the different locations in the detection path is reported. A theoretical analysis for determining the appropriate conversion gain of the radar to detect the vital signal of the target with adopting only two phase states will be described. With choosing the appropriate down-conversion gain and fast switching two phase states, the heartbeat and respiration of a human target can be determined using data acquisition model by analyzing the down-converted signal. A 2.4 GHz experimental prototype was fabricated on a PCB substrate to verify the proposed vital signal detection method. Measurements show good agreement with the theoretical prediction that the radar can clearly detect heartbeat and respiration signals at any point within the detectable range of the radar.