A 77-GHz Mixed-Mode FMCW Signal Generator Based on Bang-Bang Phase Detector

A 77-GHz mixed-mode frequency-modulated continuous-wave (FMCW) signal generator is proposed based on the bang-bang phase detector (BBPD). Instead of employing a linear digital-to-time converter (DTC), a 1-bit 3rd-order single-loop Delta Sigma modulator (SLDSM3) and a hybrid finite-impulse response (FIR) filter are utilized to suppress the quantization noise induced by the BBPD. Two-stage infinite-impulse response (IIR) filters are inserted into the digital loop filter (DLF) to reduce the instant variation at output, smoothing the chirp waveform during its generation. To improve the linearity around the turning-around points (TAPs) of the chirp, a type-III slope estimator with switchable polarity is employed. The prototype is implemented in 65-nm CMOS technology, with the total power consumption of 43.1 mW. Measurement results show a 77-GHz carrier with -81.7-dBc/Hz phase noise at 1-MHz offset, as well as a generated triangle chirp that features 1-ms repetition period, 1.827-GHz bandwidth and 336-kHz root-mean-square (RMS) frequency error.