A 28.8 GHz Fractional-N Phase-Locked Loop for Millimeter-Wave Application

Abstract

A 28.8 GHz fractional-N phase-locked loop (PLL) for millimeter-wave application, particularly for the frequency-modulated continuous-wave (FMCW) modulation, is presented in this paper. The PLL directly generates millimeter-wave signals using high-performance millimeter-wave voltage-controlled oscillator (VCO). The VCO provides a wide continuous tuning range for FMCW modulation, with optimizations to mitigate parasitic effects in the millimeter-wave band. The PLL is fabricated in a 65 nm CMOS technology with an area of 0.212 mm². The measurement results show that the PLL achieves a tuning range from 24.08 to 29.6 GHz, an integrated jitter of 253.1 fs at 28.8 GHz, and a power consumption of 32 mW. In fractional-N mode, the PLL achieves an integrated jitter of 328.4 fs at 29.2 GHz with a fractional division ratio of 0.5. Using the off-chip Serial Peripheral Interface (SPI) master device, the PLL generates FMCW signals in two frequency ranges: 28–28.8 GHz and 28.8–29.6 GHz. The measured FMCW sawtooth chirp, with a 142 MHz (divide-by-4) chirp bandwidth, achieves an rms-frequency modulation (rms-FM) error of 1.4 MHz.