Fast-Switching Technique for Fractional-N Digital Bang-Bang PLL-Based Frequency Synthesizers

This brief proposes a novel fast-switching technique based on an asymmetrical tuning mechanism and a changeable convergence factor for fractional-N digital Bang-Bang (BB) phase-locked loops (PLLs). Advantage of the proposed technique in boosting speed of frequency-locking and calibration-gain convergence is clarified by a comprehensive analysis of the BB-PLL non-linear behavior. Simulated switching-time of the PLL models for use in wireless applications show significant improvement of the proposed technique over the conventional one.