A CMOS 76–81-GHz 2-TX 3-RX FMCW Radar Transceiver Based on Mixed-Mode PLL Chirp Generator Taikun Ma ,W e iD e n g , Senior Member , IEEE,Z i p e n gC h e n, Jianxi Wu , Wei Zheng, Shufu Wang

Abstract

A fully integrated 76–81-GHz frequency-modulated, continuous-wave (FMCW) radar transceiver (TRX) in a 65-nm CMOS is presented. Two transmitters (TXs) and three receivers (RXs) are integrated for multiple-input multiple-output (MIMO) processing. A 38.5-GHz mixed-mode phase-locked loop (PLL) with reconfigurable loop bandwidth and a frequency doubling scheme are employed to generate the reconfigurable FMCW chirp waveforms. The coarse-to-fine-segmented current DAC is utilized to support sawtooth FMCW chirps with fast frequency ramping-down capability, and the delay lock loop (DLL)-based delay time calibration is used to improve the linearity of the embedded 2-D Vernier time-to-digital converter (TDC). Pas- sive voltage-mode down-conversion is utilized to improve the RX linearity against TX leakage and short-range interference. A bottom-switching Gilbert-type modulator in the TX is proposed to realize the bi-phase modulation, and the magnetically coupled resonator technique is used to effectively expand the link band- width. The measurement results show that the FMCW TRX could generate reconfigurable chirps with the bandwidth from 250 MHz to 4 GHz and the period from 30 µs to 10 ms. The root-mean- square (rms) frequency error is 110 kHz for a sawtooth chirp with 4-GHz bandwidth and 300- µs period. The TX maximum output power is 13.4 dBm and is adjustable within 3 dB by reconfiguring its low dropout regulator (LDO) voltage. The RX achieves a 15.3-dB noise figure at 600-kHz IF and a −8.5-