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

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