Controllable oscillator with output oscillation adjustment and method for producing an output oscillation for use therewith
A controllable oscillator includes an output oscillation adjust module operably coupled to an oscillator for producing an effective output oscillation based on an oscillation control signal. The output oscillation adjust module includes an output select block that produces the effective output oscillation from a sequence of selected taps from the plurality of taps of the oscillator. A tap adjust control generator, responsive to the oscillation control signal generates a sequence of tap adjust control signals that command the output select block to select the sequence of selected taps from the plurality of taps. The tap adjust control generator includes an integrator having an integrator output, responsive to the oscillation control signal and a modulo(x) module for producing the sequence of tap adjust control signals based on the integrator output.
1. A phase locked loop comprising:
a difference detection module operably coupled to determine a difference signal based on at least one of a phase difference and a frequency difference between a reference oscillation and a feedback oscillation;
a loop filter module operably coupled to convert the difference signal into a control signal;
an oscillator having a plurality of taps for producing a plurality of outputs, the oscillator operably coupled to convert the control signal into an output oscillation;
an output oscillation adjust module operably coupled to the oscillator for producing an effective output oscillation based on an oscillation control signal, wherein the output oscillation adjust module includes:
an output select block, operably coupled to the plurality of taps, for producing the effective output oscillation from a sequence of selected taps from the plurality of taps based on a sequence of tap adjust control signals; and
a tap adjust control generator, responsive to the oscillation control signal that includes an integrator having an integrator output, responsive to the oscillation control signal and a modulo(x) module that produces the sequence of tap adjust control signals based on the integrator output; and
a divider module operably coupled to convert the effective output oscillation into the feedback oscillation.
2. The phase locked loop of claim 1 wherein the value of x is equal to the number of the plurality of taps.
3. The phase locked loop of claim 1 wherein the divider module is responsive to the oscillation control signal to produce the feedback oscillation by dividing the frequency of the effective output oscillation F eo by a selected divisor.
4. The phase locked loop of claim 3 wherein the divider module includes a fractional divider.
5. The phase locked loop of claim 1 wherein the effective output oscillation has a frequency F eo and the output oscillation has a frequency F o and wherein F eo >F o .
6. A method for producing an output oscillation, the method comprising the steps of:
generating a difference signal based on at least one of phase a difference and a frequency difference between a reference oscillation and a feedback oscillation;
filtering the difference signal to produce a control signal;
converting the control signal into an output oscillation using a controlled oscillation module;
adjusting the output oscillation to produce an effective output oscillation based on an oscillation control signal; and
dividing the effective output oscillation by a selected divisor to produce the feedback oscillation;
wherein the effective output oscillation has a frequency F eo and the output oscillation has a frequency F o and wherein |F eo −F o |/F o <0.5.
7. The method of claim 6 wherein the step of adjusting the output oscillation further comprises, producing the effective output oscillation from one of the plurality of taps.
8. The method of claim 7 wherein the step of adjusting the output oscillation further comprises, selecting a corresponding sequence of selected taps from the plurality of taps based on a sequence of tap adjust control signals.
9. The method of claim 8 wherein the step of adjusting the output oscillation further comprises, generating the sequence of tap adjust control signals using an integrator having an integrator output, responsive to the oscillation control signal and the reference oscillation, and a modulo(x) module for producing the sequence of tap adjust control signals based on the integrator output.
10. The method of claim 9 wherein the value of x is equal to the number of the plurality of taps.
11. The method of claim 6 wherein the selected divisor is an integer.
12. The method of claim 6 wherein the selected divisor is a fraction.
13. A controlled oscillator comprising:
an oscillator a plurality of taps coupled to a corresponding plurality of outputs, the oscillator operably coupled to convert a control signal into an output oscillation; and
an output oscillation adjust module operably coupled to the oscillator for producing an effective output oscillation based on an oscillation control signal, wherein the output oscillation adjust module includes an output select block, operably coupled to the plurality of taps, for producing the effective output oscillation from a sequence of selected taps from the plurality of taps, and a tap adjust control generator, responsive to the oscillation control signal for generating a sequence of tap adjust control signals that command the output select block to select the sequence of selected taps from the plurality of taps, wherein the tap adjust control generator includes an integrator having an integrator output, responsive to the oscillation control signal and a modulo(x) module for producing the sequence of tap adjust control signals based on the integrator output.
14. The controlled oscillator of claim 13 wherein the value of x is equal to the number of the plurality of taps.