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 <tex-math notation="LaTeX">V </tex-math> -band (40–75 GHz) and <tex-math notation="LaTeX">D </tex-math> -band (110–170 GHz) bring the signal to the <tex-math notation="LaTeX">D </tex-math> -band, subsequently amplified and radiated via a power amplifier (PA) and an on-chip antenna at <tex-math notation="LaTeX">D </tex-math> -band. The <tex-math notation="LaTeX">D </tex-math> -band PA with a reduced gain of transistors at <tex-math notation="LaTeX">fₘₐₓ </tex-math> /2 proposes a broadband gain-boosting technique, achieving a maximum achievable gain ( <tex-math notation="LaTeX">Gₘₐₓ </tex-math> ) 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.