Synchronizing circuit

Claim 1

Apparatus for synchronizing an oscillator with a reference signal of known frequency, which comprises: a voltage-controlled oscillator having a free-running output frequency which is close to a desired output frequency; a trigger circuit, connected to said reference signal source, for generating a square wave signal in phase-synchronism with said reference signal; a one-shot multivibrator, connected to and triggered by said trigger circuit, for generating a train of pulses in phase-synchronism with said square wave signal, said pulse train having a predetermined duty cycle; a burst oscillator periodically enabled by the pulse train from said one-shot multivibrator, said burst oscillator having a predetermined output frequency and a comb-like frequency spectrum comprising discrete harmonics of said reference signal; means, operatively associated with said generating means, for altering the envelope of said comb-like frequency spectrum such that the particular reference frequency harmonic contained therein which has the same frequency as the desired output frequency has a non-zero amplitude, said envelope altering means comprising: means for adjusting the duty cycle of the pulse train from said one-shot multivibrator; and means for adjusting the output frequency of said burst oscillator, said apparatus further comprising: means, connected to said voltage-controlled oscillator and to said burst oscillator for causing said free-running frequency to coincide with the frequency of said particular reference frequency harmonic.