VCO feedback loop to reduce phase noise
First Claim
1. A phase-locked loop (PLL) for producing a phase-locked oscillation, the PLL comprising:
- a phase detection module for producing a current representing a phase difference between a feedback signal and a reference signal;
a loop filter operably coupled to receive the current and for converting the current into a control voltage; and
a voltage controlled oscillator (VCO) operably coupled to receive the control voltage at a VCO input and to produce an oscillation signal responsive to the control voltage wherein the oscillation signal is provided to the phase detection module in a first feedback loop, wherein;
the VCO further comprises a phase adjustment module for reducing phase noise in the oscillation signal, the phase adjustment module operably coupled to receive the oscillation signal and to produce a correction voltage to counteract a phase shift resulting from phase noise in the oscillation signal; and
wherein the correction voltage is provided to adjust the oscillation signal frequency in a second feedback loop; and
wherein the phase adjustment module further includes a plurality of sampling modules coupled to receive the oscillation signal, wherein each sampling module of the plurality of sampling modules samples the oscillation signal over a different time interval to produce a sampled voltage corresponding to a change in the period of the oscillation signal.
1 Assignment
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Accused Products
Abstract
A phase adjustment module in a voltage controlled oscillator (VCO) samples a VCO oscillation to detect changes in the oscillation frequency and produces a corresponding correction voltage that is feedback to the VCO input to correct the frequency change. A plurality of sampling modules, each formed to start sampling at a different point on the oscillation cycle, charge a sampling module capacitor over the period of a full oscillation cycle. The samples are coupled to a low pass filter to produce a running average of all the samples. The charge on each capacitor is coupled to a first input of a plurality of operational amplifiers and the running average is coupled to a second input. The summed output of the operational amplifiers is substantially equal to a difference between the running average and a voltage representing the instantaneous time change or phase change of the oscillation frequency.
16 Citations
26 Claims
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1. A phase-locked loop (PLL) for producing a phase-locked oscillation, the PLL comprising:
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a phase detection module for producing a current representing a phase difference between a feedback signal and a reference signal; a loop filter operably coupled to receive the current and for converting the current into a control voltage; and a voltage controlled oscillator (VCO) operably coupled to receive the control voltage at a VCO input and to produce an oscillation signal responsive to the control voltage wherein the oscillation signal is provided to the phase detection module in a first feedback loop, wherein; the VCO further comprises a phase adjustment module for reducing phase noise in the oscillation signal, the phase adjustment module operably coupled to receive the oscillation signal and to produce a correction voltage to counteract a phase shift resulting from phase noise in the oscillation signal; and wherein the correction voltage is provided to adjust the oscillation signal frequency in a second feedback loop; and wherein the phase adjustment module further includes a plurality of sampling modules coupled to receive the oscillation signal, wherein each sampling module of the plurality of sampling modules samples the oscillation signal over a different time interval to produce a sampled voltage corresponding to a change in the period of the oscillation signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A VCO, comprising:
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oscillation circuitry operably coupled to receive a control voltage at a VCO input and to produce an oscillation signal responsive to the control voltage; a phase adjustment module for reducing phase noise in the oscillation signal, the phase adjustment module operably coupled to receive the oscillation signal and to produce a correction voltage to counteract a phase shift resulting from phase noise in the oscillation signal; and wherein the correction voltage is provided to adjust the oscillation signal frequency; and wherein the phase adjustment module further includes a plurality of sampling modules coupled to receive the oscillation signal, wherein each sampling module of the plurality of sampling modules samples the oscillation signal over a different time interval to produce a sampled voltage corresponding to a change in the period of the oscillation signal. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A method for producing an oscillation, comprising:
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receiving a control voltage and producing an oscillation signal responsive to the control voltage; sampling the oscillation signal over a plurality of different time intervals to produce a sampled voltage corresponding to a change in the period of the oscillation signal; filtering the sampled voltage from the plurality of sampling modules and producing a filtered voltage representing a running average of the received sampled voltage; reducing phase noise in the oscillation signal by producing a correction voltage to counteract a phase shift resulting from phase noise in the oscillation signal; and producing the correction voltage to adjust the oscillation signal. - View Dependent Claims (26)
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Specification