Phase comparator for use in frequency synthesizer phase locked loop

Claim 1

A DIGITAL FREQUENCY SYNTHESIZER OF THE TYPE EMPLOYING A VOLTAGE CONTROLLED OSCILLATOR CONTROLLABLE IN DISCREET FREQUENCY STEPS, THE OUTPUT OF THE VOLTAGE CONTROLLED OSCILLATOR BEING APPLIED TO A DECADE DIGITAL DIVIDER AND DIVIDED DOWN TO A PREDETERMINED OUTPUT FEEDBACK FREQUENCY EQUAL THAT OF SAID OUTPUT STEPS, A REFERENCE FREQUENCY SOURCE, PHASE COMPARISON MEANS TO WHICH SAID REFERENCE FREQUENCY SOURCE AND DIVIDER FEEDBACK SIGNALS ARE APPLIED FOR PHASE COMPARISON, THE OUTPUT FROM SAID PHASE COMPARISON MEANS BEING APPLIED TO SAID VOLTAGE CONTROLLED OSCILLATOR TO COMPLETE A CONTROL LOOP FOR CONTROLLING THE FREQUENCY OF SAID OSCILLATOR; MEANS FOR GENERATING VOLTAGE CONTROLLED OSCILLATOR OUTPUT FREQUENCIES IN CONTROLLABLE STEPS OF PREDETERMINED FREQUENCY SEPARATION AND PHASE COMPARING IN SAID PHASE COMPARISON MEANS AT A FREQUENCY TWICE THAT OF SAID OUTPUT STEPS, COMPRISING SAID REFERENCE FREQUENCY SOURCE PROVIDING A FREQUENCY TWICE THAT OF THE OUTPUT OF SAID DIVIDER, FREQUENCY MULTIPLYING MEANS RECEIVING THE OUTPUT OF SAID DIVIDER AND MULTIPLYING SAID OUTPUT FREQUENCY BY A FACTOR OF TWO, SAID PHASE COMPARISON MEANS RECEIVING SAID REFERENCE FREQUENCY AND THE OUTPUT OF SAID FREQUENCY MULTIPLYING MEANS, SAID PHASE COMPARISON MEANS DEVELOPING A DIRECT VOLTAGE OUTPUT SIGNAL THE AVERAGE OF WHICH IS PROPORTIONAL TO THE PHASE DISCREPANCY BETWEEN THE INPUT SIGNALS THERETO, WHEREBY THE LEVEL OF SPURIOUS SIGNALS AT THE FREQUENCY CORRESPONDING TO SAID OUTPUT STEPS IS REDUCED AT THE OUTPUT OF SAID PHASE COMPARISON MEANS AND GAIN IN SAID CONTROL LOOP IS INCREASED TWOFOLD.