A low cost simple RF front end using time-domain multiplexing for direction of arrival estimation of physiological signals

Doppler radar has been used for vital signs monitoring. Multiple subject monitoring and direction of arrival estimation is possible by using multiple antennas and receivers. The homodyne receiver requires a quadrature demodulator for each antenna. The complexity of the system and the number of baseband channels will increase with the number of antennas. In this paper we propose time-domain multiplexing of the RF outputs of a four element antenna array and down-conversion using a single IQ demodulator. We de-multiplex the outputs in baseband and estimate the DOA for mechanical targets and a human subject breathing in front of the radar.