Frequency synthesizer

Claim 1

A frequency synthesizer including: a. signal producing means for generating a reference signal having a precise predetermined frequency; b. a voltage controlled oscillator tunable in discrete frequency steps over a predetermined frequency range and producing an output signal; c. means for tuning said oscillator to a predetermined output frequency value; d. encoding means for converting said frequency value into its equivalent nine''s complement and formating said last number into binary coded decimal form; e. a shift register having a plurality of stages, f. a presettable counter, having a maximum count equal to the upper frequency limit of said synthesizer less the number of stages in the shift register, said binary coded decimal equivalent nine''s complement number being applied to said counter to fix the beginning counting number, and said counter counting said output pulses from said voltage controlled oscillator; g. coincidence means for providing a signal at the occurrence of the maximum count in said counters, said signal activating said shift registers to shift at the occurrence of each subsequent output pulse from said voltage controlled oscillator until all said stages have shifted; h. gate means for producing a feedback signal when all said stages have shifted; i. resetting means for presetting said presettable counter to its initial conditions during the operation of said shift register; j. a phase detector coupled to said signal producing means and said gate means, said phase detector responding to said reference signal and to said feedback signal for producing an error signal related to the difference between said reference signal and said feedback signal; and k. network means for applying said error signal to said voltage controlled oscillator to adjust the frequency of said oscillator to eliminate said phase displacement.