A D-Band Low-Power and High-Efficiency Frequency Multiply-by-9 FMCW Radar Transmitter in 28-nm CMOS

This article presents a 135-155-GHz low-power and high-efficiency frequency multiply-by-9 (x9) frequency-modulated continuous-wave (FMCW) radar transmitter (TX). Starting from a 16-GHz frequency-chirping input signal, cascaded frequency triplers at V-band (40-75 GHz) and D-band (110-170 GHz) bring the signal to the D-band, subsequently amplified and radiated via a power amplifier (PA) and an on-chip antenna at D-band. The D-band PA with a reduced gain of transistors at f $_{max}$ /2 proposes a broadband gain-boosting technique, achieving a maximum achievable gain (G $_{max}$ ) for broad frequency range with high-order embedding passives. The x9 chain proposes phase-controlled frequency triplers that align the phase of each harmonic contribution and boost the third harmonic output power, conversion gain, and dc-to-RF efficiency. Implemented in a 28-nm CMOS process, the TX achieves a measured effective isotropic radiated power (EIRP) of 9.4 dBm, a dc-EIRP efficiency of 16.6% while exhibiting an antenna gain de-embedded output power of 7.1 dBm, and a dc-to-RF efficiency of 9.7% with less than 77-mW dc power consumption.