Synchronisation of controllable oscillator reference signal with input - uses signals proportional to difference between two frequencies for oscillator control

摘要

A phase control circuit with two phase discriminators generates two control signals with a 90 deg. phase difference, whose frequency is equal to the difference between the frequencies of the reference and input signals. A signal is derived, whose amplitude is proportional to this difference frequency. It is used for the oscillator control. Pulses are generated at each second zero crossing by the first control signal, and amplitudes proportional to the pulse frequency are applied to the other control signal. Thus an additional control signal is applied to the oscillator, whose polarity and amplitude correspond to those of the difference frequency.