Super-Regenerative Oscillator-Based High-Sensitivity Radar Architecture for Motion Sensing and Vital Sign Detection

Abstract

A radar sensor architecture based on a super-regenerative oscillator (SRO) with very high sensitivity is presented for vital sign detection and motion sensing. As a proof of concept, the proposed SRO-based radar sensor architecture, operating in its logarithmic mode, incorporates a patch antenna as a frequency-selective network to transmit and receive radio frequency (RF) signals at 2.32 GHz to conduct target sensing. In this prototype, a common source heterojunction (HJ)-FET is adopted as a variable-gain amplifier in the positive feedback loop of SRO, where two quench signals, 200 Hz and 10 KHz, are employed respectively at the gate of the transistor to periodically modulate the oscillation condition. Furthermore, the theoretical analysis for the radar signal gain of the proposed SRO radar sensor is carried out, demonstrating a 20 dB/decade voltage gain with respect to the input signal reflected from the target. Thanks to the intrinsic automatic gain control characteristic of SRO, the voltage gain of radar signal can go beyond 100 dB in theory. To this end, the measured voltage gain of radar signals with different quench frequencies of the SRO is compared with the theoretical values in the logarithmic mode, exhibiting a maximum gain of 70 dB in the experiment. In addition, compared with the self-injection-locked (SIL) architecture, the experimental results show that the proposed SRO-based radar sensor can exhibit 34–39 dB voltage gain improvement, thereby detecting the actuator movement and vital sign signals of human target accurately at a longer distance with higher sensitivity and reduced circuit complexity.