Phase locked loop input signal monitoring circuit - prevents phase errors caused by phase jumps or frequency shifts using phase detector and filter

摘要

A circuit for monitoring phase control circuit input signals is designed to detect phase jumps and frequency shifts in order to prevent them from causing a phase shift between the output signal and the desired input signal phase. A phase detector (PD) determines the phase difference between the input signals and an output signal generated by an oscillator and produces an error signal which is returned to the oscillator by a filter arrangement. A switching stage determines the phase and/or frequency difference between the input and output signals and generates a blocking signal which controls the filter so as to halt the control process whent he phase and/or frequency difference exceeds defined limits.