Frequency synthesizer incorporating vernier phase adjuster
AssigneePairgain Technologies, Inc.
InventorBenedict A. Itri
Life of this patent
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Abstract
A frequency synthesizer for producing an output whose phase and/or frequency can be finely adjusted under digital control. The synthesizer utilizes a phase lock loop including a phase detector responsive to a prescale divide-by-N frequency divider and a feedback divide-by-M frequency divider to product an output signal F.sub.OUT. The phase of F.sub.OUT can be shifted by a small increment by slightly adjusting the values of the divisors M and N.
Claims15
A frequency synthesizer including means for previously adjusting the phase of a periodic output signal of frequency F.sub.OUT, said synthesizer comprising:
- source means providing a periodic input signal of frequency F.sub.IN ;
- first divider means responsive to said input signal F.sub.IN for producing a signal of frequency F1 where F1=F.sub.IN /N;
- second divider means responsive to said output signal F.sub.OUT for producing a signal of frequency F2 where F2=F.sub.OUT /M;
- phase detector means responsive to said signals F1 and F2 for producing a control signal V.sub.c ;
- oscillator means for producing said output signal F.sub.OUT as a function of said signal Vd;
- and
- phase adjusting means for selectively temporarily simultaneously incrementing the values of M and N to shift the phase of said output signal in one direction or decrementing the values of M and N to shift the phase of said output signal in an opposite direction, while maintaining said output signal frequency F.sub.OUT fixed.
In a phase lock loop frequency synthesizer including controllable oscillator means for providing an output signal of frequency F.sub.OUT, phase detector means for producing an oscillator control signal Vc, prescale divide-by-N means responsive to a periodic reference signal of frequency F.sub.IN for producing a first phase detector input signal of frequency F1 wherein F1=F.sub.IN /N, and feedback divide-by-M means responsive to said output signal for producing a second phase detector input signal of frequency F2 where F2=F.sub.OUT /M, an improvement for finely shifting the phase of said output signal in steps equal to 1/F.sub.IN- 1/F.sub.OUT while maintaining the frequency of said output signal fixed said improvement comprising:
- phase adjusting means for selectively temporarily simultaneously setting the values of N and M to either (1) n and m, to maintain the phase of said output signal, (2) n-1, and m-1 to advance the phase of said output signal, or (3) n+1 and m+1 to retard the phase of said output signal, respectively.
A method of shifting the phase of an output signal of frequency F.sub.OUT, produced in response to a reference signal of frequency F.sub.IN, by an oscillator controlled y a phase detector responsive to first and second input signals of frequency F1 and F2, respectively, where F1=F.sub.IN /N and F2=F.sub.OUT /M, comprising the steps of:
- defining nominal values of N and M, respectively;
- and
- concurrently incrementing or decrementing said nominal values of N and M to respectively retard or advance the phase of said output signal while maintaining the frequency of said output signal fixed.
Dependencies are inferred from the claim text.