On the discrimination of a synchronized oscillator against interference accompanying the synchronizing signal

An oscillator may be synchronized by an injected signal if the frequency of the signal is close enough to the natural frequency of the oscillator, and if its amplitude is sufficiently large. The output of the oscillator then contains only the frequency of the injected synchronizing signal. In practice an interfering signal is usually present in the input to the oscillator together with the synchronizing signal, and an important property of the synchronized oscillator is its discrimination against the interfering signal even when the difference between the interfering and synchronizing frequencies is infinitesimal. The response of the oscillator to the interfering signal is investigated under conditions where the interference component of the oscillator output is small; the response is found to be linear, and the discrimination is expressed analytically. Good agreement between theory and experiment is obtained.