A novel fractional-order charge-pump PLL with the fractional-order loop filter

In this paper, a novel fractional-order charge-pump-phase-locked-loop (FO-CPPLL) using a fractional-order loop filter (FO-LF) is proposed to improve the overall system performance. The FO-CPPLL is obtained by extending the traditional CPPLL order from integer domain to real domain by using the FO-LF. Specifically, a fractional-order capacitor is applied to replace the integer-order capacitor in the traditional second-order LF, and the constructed FO-LF is inserted between PFD/CP and VCO to form the FO-CPPLL. The FO-LF actualizes fine tuning accuracy in seeking the orders between [0,1] for FO-CPPLL to improve the tracking speed and reducing the system phase loss. Also, the proposed FO-CPPLL can obtain lower jitter and better stability. Finally, simulation results verify the analysis and effectiveness of the proposed FO-CPPLL.