A 360 GHz Wideband CMOS Autodyne FMCW Radar: Theory and Implementation

A fully integrated wideband THz autodyne frequency-modulated continuous-wave (FMCW) radar is reported in this work. The core of the transmitter is a five-stage voltage-controlled ring oscillator (VCRO). Wideband operation is achieved through the radiation of the fifth harmonic ( $5{f}_{o}$ ) of the proposed VCRO. Additionally, an on-chip folded slot antenna is designed for radiation and reception of voltage-controlled oscillator (VCO)’s signal while providing the optimum matching condition at $5{f}_{o}$ . The radar is fabricated in a 55-nm BiCMOS process using only CMOS transistors with ${f}_{T}/{f}_{\max }=255$ /290 GHz. The radar achieves a peak equivalent-isotropically radiated power (EIRP) of 6.2 dBm using a hyper-hemispherical silicon lens and a 57 GHz bandwidth with an in-band power variation of 5.8 dB. It consumes 152 mW of dc power and occupies an area of 0.16 mm2. The autodyne radar topology utilizes the oscillator transistors as the mixing element, generating an intermediate frequency (IF) signal that is extracted from the $V_{\mathrm { DD}}$ line. Simulation results of the autodyne operation and IF generation mechanism are provided, verifying the dual operation of VCO as a transmitter and receiver. At last, the radar is tested in a focal imaging setup to take images of human teeth and capture the cavities and root canals inside the teeth. To the best of our knowledge, this radar achieves the highest bandwidth and smallest area among the VCO-based CMOS radars in the 100–500 GHz range.