Phase lock loops and methods for their operation
First Claim
1. A phase lock loop, comprising:
- a voltage controlled oscillator for generating an output signal having a frequency which is responsive to a control voltage;
a phase detector responsive to the output signal and to a reference signal to generate a control signal indicative of a phase difference of the output signal and the reference signal; and
a loop filter comprising a charge pump and a filter network, the charge pump being responsive to the control signal and to the control voltage to apply a charge indicative of both the phase difference and the control voltage to the filter network to develop the control voltage.
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Accused Products
Abstract
A phase lock loop comprises a voltage controlled oscillator, a phase detector and a loop filter comprising a charge pump and a filter network. The voltage controlled oscillator generates an output signal having a frequency which is responsive to a control voltage. The phase detector is responsive to the output signal and to a reference signal to generate a control signal indicative of a phase difference of the output signal and the reference signal. The charge pump is responsive to the control signal and to the control voltage to apply a charge indicative of both the phase difference and the control voltage to the filter network to develop the control voltage. Because the charge supplied by the charge pump depends on the control voltage as well as the phase difference of the output signal and the reference signal, the rate of adjustment of the output signal frequency depends on the present output signal frequency. Consequently, there is a normalization of performance with respect to operating frequency which provides more stable and predictable performance characteristics over a given range of operating frequencies.
42 Citations
25 Claims
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1. A phase lock loop, comprising:
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a voltage controlled oscillator for generating an output signal having a frequency which is responsive to a control voltage; a phase detector responsive to the output signal and to a reference signal to generate a control signal indicative of a phase difference of the output signal and the reference signal; and a loop filter comprising a charge pump and a filter network, the charge pump being responsive to the control signal and to the control voltage to apply a charge indicative of both the phase difference and the control voltage to the filter network to develop the control voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A method for operating a phase lock loop, comprising:
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generating an output signal having a frequency which is responsive to a control voltage; detecting a phase difference of the output signal and a reference signal; and applying a charge indicative of both the phase difference and the control voltage to a filter network to develop the control voltage. - View Dependent Claims (21, 22, 23, 24, 25)
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Specification