A 77-GHz Mixed-Mode FMCW Generator Based on a Vernier TDC With Dual Rising-Edge Fractional-Phase Detector

A 77-GHz frequency-modulated continuous-wave (FMCW) generator is presented for millimeter-wave (mm-wave) radar applications. The FMCW chirp is provided by a mixedmode phase-locked loop (PLL). A dual rising-edge fractionalphase detector based on time-to-digital converter (TDC) is proposed to overcome the problem caused by the rising and falling time mismatch. A 2.3 ns detection range, 10 ps resolution Vernier TDC is employed in the detector to cover the two consecutive rising edges with less power consumption. A self-calibrated delay chain is employed in the Vernier TDC to overcome process, voltage and temperature (PVT) variations. Furthermore, sampling-edge selection technique is utilized to avoid the glitch during phase detection. A divider-less frequency error estimator is presented to save area and power. By employing a coarsefine segmented digital-to-analog converter (DAC), the generator supports triangular and sawtooth-like FMCW chirp with reconfigurable period and bandwidth. An LC voltagecontrolled oscillator (VCO) with split varactor is proposed to improve the linear tuning range. Implemented in 65 nm CMOS, the FMCW generator consumes 99 mW power and 0.7 mm × 0.8 mm chip area. The measurement results show that the phase noise from 78.7 GHz carrier is -87.4-dBc/Hz at 1 MHz offset. The measured rootmean-square (RMS) frequency error of a sawtooth-like FMCW chirp with 4 GHz bandwidth and 0.1 ms period is 205 kHz.