Studies on the performance of phase-locked loops incorporating modified loop filters

Abstract

The behaviour of a phase-locked loop (PLL) is highly dependent on the structure of the loop filter. In the present paper, the filter structure has been modified by incorporating a high-pass filter connected in parallel to the conventional low-pass filter. Numerical results show that a proper choice of design parameters of the filters can enhance the transient response of a PLL as well as improve its noise rejection capability in some specific cases. The filter modification algorithm has been verified by means of a software experiment using MAT-LAB, and through a hardware experiment.