A mm-Wave FMCW Radar Transmitter Based on a Multirate ADPLL

We present a 60-GHz FMCW radar transmitter based on an all-digital phase-locked loop (ADPLL) with ultra-wide linear frequency modulation. Multirate, two-point modulation generates an ultra-linear programmable frequency ramp. A novel, closed-loop DCO gain linearization method employing 24kb of SRAM realizes a GHz-level triangular chirp with high sweep linearity, and enables hitless modulation through multiple DCO tuning banks. Measured frequency error (i.e., nonlinearity) in the FMCW ramp is only 117-kHz(rms) for a 62-GHz carrier with 1.22-GHz bandwidth. The synthesizer is transformer-coupled to a 3-stage neutralized power amplifier that delivers +5 dBm to a 50-Omega load. Implemented in 65-nm CMOS, the transmitter prototype consumes 89 mW from a 1.2-V supply.