Self-injection-locked radar sensor with active-integrated-antenna and differentiator-based demodulator for noncontact vital sign detection

This paper presents a new self-injection-locked (SIL) radar sensor with an active-integrated-antenna (AIA) and a differentiator-based demodulator for noncontact vital sign detection. The AIA is designed to play both roles of radiating the radio-frequency signal and received the scattered-back signal, which is phase-modulated by the human chest movement. Moreover, a novel differentiator-based demodulator is proposed to acquire the vital signs from the modulated signal. The developed radar sensor has been successfully verified as the human subject is located at the distances of 1.5 m and 2.8 m away from the radar. Except for the compactness and low cost, the developed SIL AIA sensor has a frequency-scalable advantage to be realized in the millimeter-wave range for the sensitivity improvement.