An 18.8-to-20.3-GHz Wide-Ramping-Range Cascaded- PLL-Based FMCW Generator with 44.1-kHz RMS Frequency Error and -105.6-dBc/Hz Phase Noise in 40-nm CMOS

Millimeter-wave (mm-Wave) frequency-modulated continuous wave (FMCW) radars become popular among automotive, security and gesture recognition applications [1–4]. To achieve high signal-to-noise ratio (SNR) and frequency modulation (FM) accuracy, these systems require frequency synthesizers to generate fast-chirp FMCW signal with both low phase noise (PN) and small frequency error. Conventional phase-locked loop (PLL) based chirp generators designed with narrow bandwidth can offer low PN but result in low modulation speed and frequency distortion. Recent works employ the two-point-modulation (TPM) scheme [2–4] to overcome the trade-off between PN and chirp linearity. By adding a high-pass tuning path to the voltage-controlled oscillator (VCO), the fast modulation can be achieved without impact on PN performance. However, the gain mismatch between the two tuning paths could produce modulation error. Besides, the additional high-pass path and related calibration blocks may introduce extra noise.