Technique for fast triangular chirp modulation in FMCW PLL

Abstract

Frequency-modulated continuous-wave (FMCW) radars necessitate fast frequency modulation. However, finite loop bandwidth of a phase-locked loop (PLL) limits the accuracy of fast frequency modulation. This paper proposes a phase compensation (PC) technique to address this limitation. The synthesizer PLL with the PC technique realizes fast and precise triangular chirp modulation by adding a compensating square wave phase before the integral path of the loop filter. The synthesizer is designed in 130-nm SiGe BiCMOS technology. Simulation results show rms frequency error improvement of 18 times over conventional PLL with a chirp bandwidth of 2.56GHz and 20 mu s chirp period at 94GHz.