A W-band RTWO-Based Digital Transmitter for PMCW Radar Achieving 14.9% Efficiency

This work presents a compact and highly efficient W-band digital transmitter for phase-modulated continuous wave (PMCW) radar applications. A rotary traveling-wave oscillator (RTWO) with an embedded edge-combining upconverter simultaneously performs frequency quadrupling and BPSK modulation, thereby eliminating the need for mm-wave LO buffers. Phase shifting is implemented in the charge domain using a CDAC within a charge-steering sampling (CSS) ADPLL, providing a convenient and power-efficient mechanism for phased-array operation. Fabricated in 22-nm CMOS, the transmitter occupies 0.144 mm2 and delivers 18 dBm peak output power with a maximum efficiency of 14.9%. The phase shifting (PS) is measured under both single- and dual-channel configurations, demonstrating a 409.7 fs (2.8◦) step size and an RMS phase error of 55.6 fs (0.38◦) The architecture achieves state-of-the-art TX efficiency and integration density among W-band radar transmitters, while offering intrinsic phase-shifting capability for scalable PMCW radar systems.