An Ultra-Low-Power C-Band FMCW Transmitter Using a Fast Settling Fractional-N DPLL and Ring-Based Pulse Injection Locking Oscillator
Abstract
Frequency-modulated continuous-wave (FMCW) signals-based radar systems can outrun the optical and ultrasound sensors in dark and severe weather conditions. FMCW radar systems require a fast settling frequency synthesizer to reduce the chirp signal’s inactive and modulation times. This work proposes a new C-B and FMCW Transmitter based on Fast Settling Fractional-N DPLL (FS-FNDPLL) and ring-based pulse injection locking oscillator (R-PILO). The proposed FS-FNDPLL generates an ultra-fast low-noise smooth narrowband chirp by introducing an automatic controller-based TDC switching (AC-TDCSw) scheme in the forward loop of FNDPLL. Also, the proposed FS-FNDPLL employs a new background gain calibrated digital-to-time converter (BGC-DTC) as a fractional divider in the feedback path for the quantization noise cancellation (QNC). The proposed FMCW transmitter uses an R-PILO to produce fast switching adjacent carriers after generating a narrowband chirp using FS-FNDPLL. The main features of the proposed FMCW to accelerate settling time with AC-TDCSw, BGC-DTC and the integration of spur suppressing pulse generator (SSPG) in R-PILO enable ultra-fast chirps with less phase noise and spur levels. The proposed transmitter up-converts the 500MHz narrowband chirp signal onto four adjacent carriers for obtaining a 2GHz chirp at the C-band. The simulation results prove that the proposed FMCW Transmitter consumes 79mW power. Furthermore, the phase noise of the proposed FS-FNDPLL is reduced to dBc/Hz at 1MHz. The proposed FS-FNDPLL reduces the settling time to 1s with the introduced AC-TDCSw scheme.
This paper was recommended by Regional Editor Zoran Stamenkovic.
