Adaptively enhanced phase locked loops

A method that enhances the performance of a phase locked loop is proposed. The method is based on integrating an adaptive frequency estimator into a standard phase locked loop. This integration significantly improves the performance of the resulting phase locked loop and eliminates some design tradeoffs that are inherent in a standard phase locked loop. The proposed enhanced phase locked loop is analyzed and a nonlinear model that accurately predicts its performance is developed. This developed model is subsequently linearized to obtain a linear time-invariant model that facilitates both analysis and design of the enhanced phase locked loop. Based on the developed linear time-invariant model, guidelines for designing the enhanced phase locked loop are also provided. The results are illustrated by several examples.