Two-part synthesizer modulation system using a reference phase modulator

Claim 2

Frequency modulation apparatus for modulating the output of a phase-locked loop frequency synthesizer providing an essentially flat modulating frequency response independent of the loop bandwidth, said apparatus comprising: reference signal source means (12) for producing a high stability unmodulated reference signal at a desired frequency; voltage controlled oscillator means (18) for generating an output signal whose frequency is proportional to a D.C. input voltage; phase-locked loop means for feeding back a portion of said output signal (20) to included phase detector means (16), the latter detecting the phase difference between said reference signal and said output feedback signal and producing an output correction signal for maintaining said voltage controlled oscillator means (18) at a desired frequency; and two-port modulation means for introducing modulation at an input (26) of said voltage controlled oscillator means (18) and at an input (24) of said phase detector means (16) with a balanced amplitude and polarity whereby the resultant modulation effected by said two-port modulation means is nulled at the output of said phase detector means (16).

Claim 3

The apparatus of claim 1 wherein said means for modulating the frequency of said high stability unmodulated reference signal includes a frequency modulator (14).

Claim 4

The apparatus of claim 1 and 2 wherein said frequency modulator (14) includes a phase modulator (36) and an integrator (42).

Claim 5

A circuit for frequency modulating the output of a phase-locked loop frequency synthesizer providing an essentially flat modulating frequency response independent of the loop bandwidth, said circuit comprising in combination: a phase-locked loop frequency synthesizer having a high stability, unmodulated reference signal source (12), a phase detector (16), a voltage controlled oscillator (18), and a feedback path between said voltage controlled oscillator (18) and said phase detector (16); a frequency modulator (14) interposed between said high stability, unmodulated reference signal source (12) and said phase detector (16); and a direct frequency modulation port (26) included at said voltage controlled oscillator (18), said frequency modulator (14) and said direct frequency modulation port (26) being adapted for simultaneous feed in synchronism with a balanced amplitude and polarity so as to effect cancellation of the modulation at the output of said phase detector (16) and thereby provide an essentially flat modulating frequency response independent of the bandwidth of said phase-locked loop frequency synthesizer.

Claim 6

A circuit for frequency modulating the output of a phase-locked loop frequency synthesizer providing an essentially flat modulating frequency response independent of the loop bandwidth, said circuit comprising in combination: a phase-locked loop frequency synthesizer having a high stability, unmodulated reference signal source (12), a phase detector (16), a voltage controlled oscillator (18), and a feedback path between said voltage controlled oscillator (18) and said phase detector (16); a frequency modulator (14) interposed between said high stability, unmodulated reference signal source (12) and said phase detector (16); and a direct frequency modulation port (26) included at said voltage controlled oscillator (18), said frequency modulator (14) and said direct frequency modulation port (26) being adapted for simultaneous feed in synchronism with a balanced amplitude and polarity so as to effect cancellation of the modulation at the output of said phase detector (16) and thereby provide an essentially flat modulating frequency response independent of the bandwidth of said phase-locked loop frequency synthesizer.

Claim 7

The circuit of claim 4 wherein said frequency modulator (14) includes a phase modulator (36) and an integrator (42).

Claim 8

The circuit of claim 5 wherein said phase modulator (36) includes a serrasoid phase modulator (60).

Claim 9

The circuit of claim 6, wherein said serrasoid phase modulator (60) comprises at least a voltage ramp generator (48,68,70,72), a voltage comparator (74a,74b) having an input coupled to said voltage ramp generator, and a transistor switch (62a,62b) for modulating a given input signal by modulating the trip voltage of said voltage comparator and thereby affecting the critical edge of the output waveform of said voltage comparator.

Claim 10

The circuit of claim 6, wherein said serrasoid phase modulator (60) comprises at least a voltage ramp generator, a voltage comparator having an input coupled to said voltage ramp generator, and a transistor switch for modulating a given input signal by modulating the slope of said voltage ramp generator and thereby affecting the critical edge of the output waveform of said voltage comparator.

Claim 11

9 . The circuit of claim 4 wherein said phase-locked loop frequency synthesizer further comprises an offset mixer (98) having a first input electrically connected to the output (20) of said phase-locked loop, a second input (96) fed from a multiplier (94) interposed between said high stability, unmodulated reference signal source.(32) and said offset mixer (98), and an output (100) whose frequency falls suitably within the range of operation desired.

Claim 12

A circuit for frequency modulating the output of a phase-locked loop frequency synthesizer providing an essentially flat modulating frequency response independent of the loop bandwidth, said circuit comprising in combination: a phase-locked loop frequency synthesizer having a high stability, unmodulated reference oscillator (32) with a fixed-integer divider (34) as the reference signal source (12), a phase detector (16), a voltage controlled oscillator (18) having a loop filter (38), and a feedback path between said voltage controlled oscillator (1 8 ) and said phase detector (16) and including a selectable-integer divider (40); a frequency modulator (36,42) interposed between said reference signal source (32,34) and said phase detector (16); and a direct frequency modulation port (26) included at said voltage controlled oscillator (18), said frequency modulator (36,42) and said direct frequency modulation port (26) being adapted for simultaneous feed in synchronism with a balanced amplitude and polarity so as to effect cancellation of the modulation at the output of said phase detector (16) and thereby provide an essentially flat modulating frequency response independent of the bandwidth of said phase-locked loop frequency synthesizer.

Claim 13

A circuit for frequency modulating the output of a phase-locked loop frequency synthesizer providing an essentially flat modulating frequency response independent of the loop bandwidth, said circuit comprising in combination: a phase-locked loop frequency synthesizer having a high stability, unmodulated reference oscillator (32) with a fixed-integer divider (34) as the reference signal source (12), a phase detector (16), a voltage controlled oscillator (18) having a loop filter (38), and a feedback path between said voltage controlled oscillator (1 8 ) and said phase detector (16) and including a selectable-integer divider (40); a frequency modulator (36,42) interposed between said reference signal source (32,34) and said phase detector (16); and a direct frequency modulation port (26) included at said voltage controlled oscillator (18), said frequency modulator (36,42) and said direct frequency modulation port (26) being adapted for simultaneous feed in synchronism with a balanced amplitude and polarity so as to effect cancellation of the modulation at the output of said phase detector (16) and thereby provide an essentially flat modulating frequency response independent of the bandwidth of said phase-locked loop frequency synthesizer.

Claim 14

A circuit for frequency modulating the output of a phase-locked loop frequency synthesizer providing an essentially flat modulating frequency response independent of the loop bandwidth, said circuit comprising in combination: a phase-locked loop frequency synthesizer having a high stability, unmodulated reference oscillator (32) with a fixed-integer divider (34), a phase detector (16), a voltage controlled oscillator (18), and a feedback path between said voltage controlled oscillator (18) and said phase detector (16) and including a selectable-integer divider (40); a frequency modulator (12',14') interposed between said selectable-integer divider (40) and said phase detector (16) in said feedback path (114); and a direct frequency modulation port included at said voltage controlled oscillator (18), said frequency modulator (12',14') and said direct frequency modulation port being adapted for simultaneous feed in synchronism with a balanced amplitude and polarity so as to effect cancellation of the modulation before being input to said phase detector (16) and thereby provide an essentially flat modulating frequency response independent of the bandwidth of said phase-locked loop frequency synthesizer.

Claim 15

A circuit for frequency modulating the output of a phase-locked loop frequency synthesizer providing an essentially flat modulating frequency response independent of the loop bandwidth, said circuit comprising in combination: a phase-locked loop frequency synthesizer having a high stability, unmodulated reference oscillator (32) with a fixed-integer divider (34), a phase detector (16), a voltage controlled oscillator (18), and a feedback path between said voltage controlled oscillator (18) and said phase detector (16) and including a selectable-integer divider (40); a frequency modulator (12',14') interposed between said selectable-integer divider (40) and said phase detector (16) in said feedback path (114); and a direct frequency modulation port included at said voltage controlled oscillator (18), said frequency modulator (12',14') and said direct frequency modulation port being adapted for simultaneous feed in synchronism with a balanced amplitude and polarity so as to effect cancellation of the modulation before being input to said phase detector (16) and thereby provide an essentially flat modulating frequency response independent of the bandwidth of said phase-locked loop frequency synthesizer.