A Digital Implementation of a Frequency Steered Phase Locked Loop

A digital implementation of a new technique that delivers an extremely accurate and stable phase locked loop system (PLL) is presented. The new technique uses competing phase and frequency loops to incorporate an accurate local reference frequency into the phase locked loop structure. Disturbances on the phase loop caused by the digital frequency loop are identified and a method to mitigate the disturbances is developed. The implementation is primarily designed for high-speed clock and data recovery and experimental results from a clock recovery system for nonreturn to zero data streams at 155.52 MHz are presented.