Frequency synthesizer

Claim 2

A frequency synthesizer comprising a variable frequency oscillator to be operated at a desired accurate frequency; standard generating means for providing a multiline spectrum with said spectral lines being spaced apart by a known frequency; means for providing a reference frequency lying within said spectrum; means for sweeping the frequency of said variable frequency oscillator across said frequency spectrum in the direction of said desired frequency starting from said reference frequency; circuit means for phase locking said variable frequency oscillator to said spectral lines encountered during said sweep and providing a pulse whenever the frequency of said variable frequency oscillator coincides with a given one of said spectral lines; said means for providing a reference frequency being coupled to said phase -locking circuit means; counting means responsive to said pulses for counting the number of spectral lines crossed during said sweep; said counting means having a predetermined count preset therein equal to the ratio of the frequency departure of said desired frequency from said reference frequency and the frequency spacing of said multiline spectrum; and means coupled to said counting means responsive to attainment in said counter of said predetermined count for disabling said sweeping means.

Claim 3

A frequency synthesizer according to claim 1 wherein said means for providing a reference frequency comprises means for generating a series of harmonics spaced apart in frequency by a multiple of said known frequency and including a particular harmonic of frequency nearest to the frequency to which said variable frequency oscillator initially is set; means for presetting said variable frequency oscillator to a preset frequency displaced from the particular frequency of said variable frequency oscillator by less than half of said multiple; and means for decoupling said series of harmonics from said circuit means and coupling said multiline spectrum to said circuit means in response to locking of said variable frequency oscillator to said particular harmonic.

Claim 4

A frequency synthesizer as recited in claim 1 wherein said sweep means for sweeping includes means for varying the frequency of said oscillator in either direction.

Claim 5

A frequency synthesizer as recited in claim 1 wherein said means for sweeping includes a capacitor across which a voltage ramp is generated, and a diode interconnecting said capacitor and a point on said control loop, said diode being reverse biased as each of said harmonics is swept over.

Claim 6

A frequency synthesizer comprising reference generator means for providing a spectrum of harmonics spaced apart by a known frequency; a variable frequency oscillator to be operated at a desired accurate frequency and tuned to an initial frequency approximating said desired frequency within an accuracy of slightly less than half said known frequency; said variable frequency oscillator and said generator means forming part of a continuously closed phase lock loop comprising means for locking said variable frequency oscillator to various ones of said harmonics; means for presetting said variable frequency oscillator to a preset frequency differing from said initial frequency by said known frequency; sweep means activated subsequent to attainment of said preset frequency for sweeping the frequency of said variable frequency oscillator across said harmonic spectrum in the direction of said desired frequency; said phase lock loop including means for deriving a distinctive control lock signal each time said variable frequency oscillator frequency coincides with one of said harmonics during said frequency sweeping; means coupled to said phase lock loop for providing an unlock pulse during that portion of the sweeping interval that said variable frequency oscillator is first pulled out of lock with the first harmonic swept through; transfer means responsive to said unlock pulse for decreasing the spacing of the harmonics of the harmonic spectrum from said generator means across which said variable frequency oscillator is swept by a desired factor; trigger means producing a trigger pulse in response to each control lock signal as said variable frequency oscillator is swept past said harmonic spectrum; counting means receptive of said trigger pulses and preset to count a predetermined number of pulses equal to the frequency departure of the desired frequency from the initial frequency and the frequency spacing of the harmonic spectrum; and means for disabling said sweeping means in response to counting of said predetermined number of trigger pulses by said counter means.

Claim 7

A frequency synthesizer comprising reference generator means for providing a spectrum of harmonics spaced apart by a known frequency; a variable frequency oscillator to be operated at a desired accurate frequency and tuned to an initial frequency approximating said desired frequency within an accuracy of slightly less than half said known frequency; said variable frequency oscillator and said generator means forming part of a continuously closed phase lock loop comprising means for locking said variable frequency oscillator to various ones of said harmonics; means for presetting said variable frequency oscillator to a preset frequency differing from said initial frequency by said known frequency; sweep means activated subsequent to attainment of said preset frequency for sweeping the frequency of said variable frequency oscillator across said harmonic spectrum in the direction of said desired frequency; said phase lock loop including means for deriving a distinctive control lock signal each time said variable frequency oscillator frequency coincides with one of said harmonics during said frequency sweeping; means coupled to said phase lock loop for providing an unlock pulse during that portion of the sweeping interval that said variable frequency oscillator is first pulled out of lock with the first harmonic swept through; transfer means responsive to said unlock pulse for decreasing the spacing of the harmonics of the harmonic spectrum from said generator means across which said variable frequency oscillator is swept by a desired factor; trigger means producing a trigger pulse in response to each control lock signal as said variable frequency oscillator is swept past said harmonic spectrum; counting means receptive of said trigger pulses and preset to count a predetermined number of pulses equal to the frequency departure of the desired frequency from the initial frequency and the frequency spacing of the harmonic spectrum; and means for disabling said sweeping means in response to counting of said predetermined number of trigger pulses by said counter means.