A 4.6mW 232GHz Autodyne Complementary Self-Injection-Locked Radar for Micrometer-Level Displacement Sensing and Imaging

This paper presents a novel complementary self-injection-locked (CSIL) radar architecture for low-power, high-accuracy THz phase sensing. The CSIL radar employs a self-injection mechanism within a coupled oscillator system, where a portion of the transmitted signal reflects off the target and is reinjected into the radar. This self-injection process induces an amplitude imbalance between the oscillators as a function of the target distance. By measuring this amplitude imbalance, the system can estimate relative displacements within an unambiguous range of λ/4. Unlike conventional phase-sensing radars, CSIL eliminates the need for complex, power-hungry frequency synthesis. It also operates in autodyne mode and is inherently immune to self-interference. The proposed radar is fabricated using the TSMC 65nm process. Operating at 232 GHz, it achieves a static range accuracy of 20 μm while consuming only 4.6 mW of DC power. Imaging measurements are also presented, highlighting the potential of CSIL in low-power 3D imaging.