Filtering circuit for a phase-locked loop

摘要

The invention relates to a novel filtering circuit whereby a phase detected output control signal is filtered and utilized to provide greater stability in a phase-locked loop. The filtering circuit is placed in the connecting path between a phase detector and an oscillator; the oscillator supplies output signals, having a repetition rate which depends on the instantaneous values of the filtered control signal. The filtering circuit comprises an adder which adds the phase detected control signal to a signal corresponding to the preceding filtered control signal multiplied by a constant factor which is less than unity (<1).