A 140-GHz FMCW TX/RX-Antenna-Sharing Transceiver With Low-Inherent-Loss Duplexing and Adaptive Self-Interference Cancellation

This article presents a 140-GHz frequency-modulated continuous-wave (FMCW) radar transceiver featuring transmit/receive (TX/RX) antenna sharing that address a TX/RX beam misalignment problem when large-aperture lenses/mirrors/reflectarrays are used for pencil beam forming. A full-duplexing technique based on circular polarization and geometrical symmetry is applied to mitigate the 3 dB + 3 dB insertion loss inherent to conventionally adopted directional couplers, while still maintaining high TX-to-RX isolation. In addition, a self-adaptive self-interference cancellation (SIC) is implemented to suppress extra leakage due to antenna mismatch from a desired frontside radiation scheme. The TX/RX antenna sharing enables the pairing with a large 3-D printed planar lens and boosts the measured effective isotropic radiated power (EIRP) to 25.2 dBm. The measured total radiated power and minimum single-sideband noise figure (SSB NF) including antenna and duplexer losses are 6.2 dBm and 20.2 dB, respectively. The measured total TX-RX isolation is 33.3 dB under 14-GHz wide FMCW chirps. Based on a 65-nm complimentary metal–oxide–semiconductor (CMOS) technology, the chip has a die area of 3.1 mm2 and consumes 405 mW of dc power. Among all reported sub-THz transceivers with TX/RX antenna sharing, this work demonstrates the highest total radiated power and is the only work that has >30 dB of TX-RX isolation while mitigating the inherent 6 dB coupler loss.