Direction of Arrival Estimation of Physiological Signals of Multiple Subjects Using Phase Comparison Monopulse Radar

While non-contact respiration monitoring using microwave Doppler radar has shown great promises over the last four decades, the isolation of one subject when multiple subjects are in view remains a challenge. In this paper, we employed anew, cost effective and scalable approach for estimating Direction of Arrival (DOA) to separate well-spaced multiple subjects by introducing a 24-GHz phase comparison monopulse radar in our system. Experimental results demonstrated that phase comparison technique can separate two subjects 1.5 meters apart from each other at a distance of 3 meters from the sensor and it can estimate the angular position of single subject with respect to the radar. It also illustrates that the phase-comparison technique is computationally faster and requires fewer snapshots or samples than the well-established MUSIC algorithm. Our experimental results also demonstrate that the monopulse technique for multiple subject measurement has estimation accuracy of almost 80%. This paper demonstrates the efficacy of using a phase-comparison monopulse technique to separate well-spaced subjects based on estimation of the angle of physiological signals, which will lead to practical adoption of this technology in our daily life.