A D-Band GaAs pHEMT 2T1R Super-Regenerative Oscillator-Based Sensor Array Using Quench-Controlled Phase-Shifting Technique for Multi-Target Vital Sign Detection

This work presents the first super-regenerative oscillator (SRO)-based sensor array capable of beam-null controlled vital sign detection, extending beyond previously reported single-element SRO implementations. A D-band 2T1R SRO sensor array is implemented in a 70-nm GaAs pHEMT technology, where two externally quenched SRO transmitters operate with a shared harmonic-mixer receiver. By introducing a controlled phase difference between synchronized quench waveforms, the effective excitation phase between the two radiating elements can be precisely adjusted, enabling two-element array factors with main-beam directions at -1° and 28° despite an inherent 108° geometric phase offset due to chip geometry. The prototype reliably detects 0.5-Hz actuator vibrations at a distance of 1.3 m, recovers human respiration (0.30–0.40 Hz) and heartbeat (1.30–1.60 Hz) at a distance of 1 m, and demonstrates angular selectivity by enhancing the intended subject while suppressing off-axis targets. These results confirm that quench-controlled phase-shifting SRO arrays provide a compact and high-sensitivity platform for spatially selective multi-target vital sign sensing in D-band radar systems.