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 mm 2 . 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.