Phase locked loop with switched-component loop filter
First Claim
1. A locked-loop circuit comprising:
- a voltage-controlled oscillator to generate an oscillator output signal having a frequency according to an oscillator control voltage;
phase detector circuitry to determine a time-varying phase difference between the oscillator output signal and a reference signal and to generate a resistance control signal having pulsing properties that vary in accordance with the time-varying phase difference; and
loop filter circuitry having;
a switched resistor network, including at least one resistor and at least one capacitor, to generate an effective resistance according to the pulsing properties of the resistance control signal; and
circuitry to generate the oscillator control voltage in accordance with the effective resistance of the switched resistor network.
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Accused Products
Abstract
Phase-locked loop circuitry to generate an output signal, the phase-locked loop circuitry comprising oscillator circuitry, switched resistor loop filter, coupled to the input of the oscillator circuitry (which, in one embodiment, includes a voltage-controlled oscillator), including a switched resistor network including at least one resistor and at least one capacitor, wherein an effective resistance of the switched resistor network is responsive to and increases as a function of one or more pulsing properties of a control signal (wherein pulse width and frequency (or period) are pulsing properties of the control signal), phase detector circuitry, having an output which is coupled to the switched resistor loop filter, to generate the control signal (which may be periodic or non-periodic). The phase-locked loop circuitry may also include frequency detection circuitry to provide a lock condition of the phase-locked loop circuitry.
39 Citations
20 Claims
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1. A locked-loop circuit comprising:
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a voltage-controlled oscillator to generate an oscillator output signal having a frequency according to an oscillator control voltage; phase detector circuitry to determine a time-varying phase difference between the oscillator output signal and a reference signal and to generate a resistance control signal having pulsing properties that vary in accordance with the time-varying phase difference; and loop filter circuitry having; a switched resistor network, including at least one resistor and at least one capacitor, to generate an effective resistance according to the pulsing properties of the resistance control signal; and circuitry to generate the oscillator control voltage in accordance with the effective resistance of the switched resistor network. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A locked-loop circuit comprising:
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a voltage-controlled oscillator to generate a clock signal having a frequency according to a control voltage; a phase detector to generate (i) a phase-compare pulse train having a pulse frequency according to a frequency of the clock signal and a pulse width substantially less than a half-cycle of the clock signal, and (ii) respective frequency-up and frequency-down pulse trains based on the phase-compare pulse train and a reference signal such that pulses within the frequency-up pulse train have pulse widths according to a phase lead between rising edges of respective pulses within the phase-compare signal and corresponding rising edges within the reference signal, and pulses within the frequency-down pulse train have pulse widths according to a phase lag between falling edges of the respective pulses within the phase-compare signal and the corresponding rising edges within the reference signal; and a loop filter to generate the control voltage based on the frequency-up and frequency-down pulse trains. - View Dependent Claims (15, 16, 17, 18, 19)
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20. A locked-loop circuit comprising:
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means for generating an output signal that oscillates at a frequency according to a control voltage; means for determining a time-varying phase difference between the output signal and a reference signal; means for generating a resistance control signal having pulsing properties that vary in accordance with the time-varying phase difference; and means, including at least one resistor and at least one capacitor, for generating (i) an effective resistance according to the pulsing properties of the resistance control signal, and (ii) the oscillator control voltage in accordance with the effective resistance of the switched resistor network.
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Specification