Frequency synthesis using fractional division by digital techniques within a phase-locked loop

Claim 1

A SYSTEM FOR GENERATING AN OUTPUT SIGNAL STABILIZED AT A SELECTED FREQUENCY, COMPRISING: (A) A GENERATOR FOR GENERATING A SIGNAL HAVING A FIXED FREQUENCY LOWER THAN SAID SELECTED FREQUENCY BY A FACTOR N EQUAL TO A FRACTIONAL NUMBER GREATER THAN UNITY, (B) A VARIABLE FREQUENCY OSCILLATOR FOR GENERATING AN OUTPUT SIGNAL THE FREQUENCY OF WHICH IS DETERMINED BY A CONTROL SIGNAL APPLIED THERETO, (C) A FREQUENCY DIVIDER COUPLED TO SAID OSCILLATOR FOR PERFORMING A SEQUENCE OF DIVISIONS OF SAID OSCILLATOR OUTPUT FREQUENCY BY A SERIES OF WHOLE NUMBERS FACTORS SELECTED TO PRODUCE AN AVERAGE DIVISON BY SAID FACTOR N WHEN AVERAGED OVER SAID SEQUENCE OF DIVISION AND FOR PRODUCING A SIGNAL IN RESPONSE THERETO, (D) A PHASE COMPARATOR COUPLED TO SAID DIVIDER AND SAID GENERATOR FOR COMPARING THE PHASE BETWEEN SAID DIVIDER SIGNAL AND SAID GENERATOR SIGNAL OF FIXED FREQUENCY AND PROVIDING A SIGNAL REPRESENTATIVE OF THE PHASE DIFFERENCE THEREBETWEEN, AND (E) MEANS COUPLED TO SAID PHASE COMPARATOR AND SAID OSCILLATOR FOR PROVIDING A CONTROL SIGNAL PROPORTIONAL TO SAID PHASE DIFFERENCE APPLIED TO SAID OSCILLATOR TO LOCK SAID OSCILLATOR OUTPUT SIGNAL AT SAID SELECTED FREQUENCY.

Claim 2

A SYSTEM FOR GENERATING AN OUTPUT SIGNAL STABILIZED AT A SELECTED FREQUENCY, COMPRISING: (A) A GENERATOR FOR GENERATING A SIGNAL HAVING A FIXED FREQUENCY LOWER THAN SAID SELECTED FREQUENCY BY A FACTOR N EQUAL TO A FRACTIONAL NUMBER GREATER THAN UNITY, (B) A VARIABLE FREQUENCY OSCILLATOR FOR GENERATING AN OUTPUT SIGNAL THE FREQUENCY OF WHICH IS DETERMINED BY A CONTROL SIGNAL APPLIED THERETO, (C) A FREQUENCY DIVIDER COUPLED TO SAID OSCILLATOR FOR PERFORMING A SEQUENCE OF DIVISIONS OF SAID OSCILLATOR OUTPUT FREQUENCY BY A SERIES OF WHOLE NUMBERS FACTORS SELECTED TO PRODUCE AN AVERAGE DIVISON BY SAID FACTOR N WHEN AVERAGED OVER SAID SEQUENCE OF DIVISION AND FOR PRODUCING A SIGNAL IN RESPONSE THERETO, (D) A PHASE COMPARATOR COUPLED TO SAID DIVIDER AND SAID GENERATOR FOR COMPARING THE PHASE BETWEEN SAID DIVIDER SIGNAL AND SAID GENERATOR SIGNAL OF FIXED FREQUENCY AND PROVIDING A SIGNAL REPRESENTATIVE OF THE PHASE DIFFERENCE THEREBETWEEN, AND (E) MEANS COUPLED TO SAID PHASE COMPARATOR AND SAID OSCILLATOR FOR PROVIDING A CONTROL SIGNAL PROPORTIONAL TO SAID PHASE DIFFERENCE APPLIED TO SAID OSCILLATOR TO LOCK SAID OSCILLATOR OUTPUT SIGNAL AT SAID SELECTED FREQUENCY.