Analysis of Loop Filters in Different PLLs for Frequency and Phase Acquisition

The Phase Locked Loop (PLL) is an important component of many electronic devices; it can be employed as a frequency synthesizer, for clock data recovery, and as amplitude and frequency demodulators. It is inherently nonlinear closed loop feedback system .The pervasiveness and popularity of the PLL is due to the robust nature and spectral purity of the PLL output signal, which are impossible to realize without the use of the PLL loop. The performance of the PLL loop depends, in particular, on the loop filter characteristics. The concept of in-loop filters in phase-locked loop (PLL) systems has been addressed. Modeling and simulations are done using MATLAB/SIMULINK software. Filters can also be selected as conventional window functions and they can be tuned to reject certain frequency components similar to the discrete Fourier transform. This method enables smoother estimation of the signal parameters such as phase angle, frequency, and amplitude in the presence of noise and harmonics. The in-loop filters can be adjusted to completely remove specific harmonics. The method is developed for an enhanced PLL system. The same method is applied to other types of PLLs. In the EPLL system, the three variables amplitude, frequency, and phase angle are being estimated.