Digital clock recovery loop
First Claim
1. A clock recovery method for extracting a clock signal from an input digital signal in a phase lock loop, the method comprising:
- producing, with a voltage controlled oscillator having a control node, an output wave having a frequency that varies in response to a voltage applied to the control node;
controlling, with charge pump and loop filter circuitry, the rate of change of the voltage on the control node of the voltage controlled oscillator;
performing, with start-up circuitry, frequency discrimination and, in conjunction with the charge pump and loop filter circuitry, adjusting the voltage on the control node of the voltage controlled oscillator;
performing phase control and adjusting the voltage on the control node of the voltage controlled oscillator using a state machine;
applying, with bias circuitry, an offset voltage to the voltage controlled oscillator such that, in the absence of any voltage applied to the control node, the frequency of the output wave produced by the voltage controlled oscillator is at least half and not greater than the final frequency of the voltage controlled oscillator when frequency lock is established.
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Accused Products
Abstract
A communications system including a clock recovery circuit that extracts a clock signal from incoming digital data, the clock recovery circuit comprising: a voltage controlled oscillator having a control node and an output producing an output wave having a frequency that varies in response to a voltage applied to the control node; charge pump and loop filter circuitry that controls the rate of change of the voltage on the control node of the voltage controlled oscillator; a start-up circuit that performs frequency detection and, in conjunction with the charge pump and loop filter circuitry, adjusts the voltage on the control node of the voltage controlled oscillator; and a state machine that performs phase detection and adjusts the voltage on the control node of the voltage controlled oscillator.
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Citations
14 Claims
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1. A clock recovery method for extracting a clock signal from an input digital signal in a phase lock loop, the method comprising:
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producing, with a voltage controlled oscillator having a control node, an output wave having a frequency that varies in response to a voltage applied to the control node; controlling, with charge pump and loop filter circuitry, the rate of change of the voltage on the control node of the voltage controlled oscillator; performing, with start-up circuitry, frequency discrimination and, in conjunction with the charge pump and loop filter circuitry, adjusting the voltage on the control node of the voltage controlled oscillator; performing phase control and adjusting the voltage on the control node of the voltage controlled oscillator using a state machine; applying, with bias circuitry, an offset voltage to the voltage controlled oscillator such that, in the absence of any voltage applied to the control node, the frequency of the output wave produced by the voltage controlled oscillator is at least half and not greater than the final frequency of the voltage controlled oscillator when frequency lock is established. - View Dependent Claims (2, 3, 4, 5)
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6. A method of using a phase lock loop to receive an oscillating input signal and produce an output signal, the phase lock loop comprising a plurality of flip-flops which are chained together, the plurality of flip-flops including a first flip-flop having a first output, including a second flip-flop having an input coupled to the first output and having a second output, and including a third flip-flop having an input coupled to the second output, the phase lock loop further comprising a control node, the method comprising:
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using the flip-flops to determine time spacing between transitions to perform a frequency comparison of the output signal relative to the input signal; extracting a clock from an input digital signal; and performing phase control and adjusting the voltage on the control node of the voltage controlled oscillator. - View Dependent Claims (7)
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8. A method for receiving an oscillating input signal and producing an output signal using a phase lock loop, the phase lock loop comprising a plurality of flip-flops which are chained together and used to determine time spacing between transitions to perform a frequency comparison of the output signal relative to the input signal, the phase lock loop further comprising a control node, the method comprising:
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receiving a digital input signal; extracting a clock from the digital input signal; performing phase control and adjusting the voltage on the control node of the voltage controlled oscillator; and applying an offset voltage to the voltage controlled oscillator such that, in the absence of any voltage applied to the control node, the frequency of the output wave produced by the voltage controlled oscillator is at least half and not greater than the final frequency of the voltage controlled oscillator when frequency lock is established.
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9. A communications method for extracting a clock signal from incoming digital data using a clock recovery circuit configured as a phase lock loop, the method comprising:
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producing an output wave using a voltage controlled oscillator having a control node and having an output, wherein the output wave has a frequency that varies in response to a voltage applied to the control node; controlling the rate of change of the voltage on the control node of the voltage controlled oscillator; performing frequency discrimination and adjusting the voltage on the control node of the voltage controlled oscillator; performing phase control and adjusting the voltage on the control node of the voltage controlled oscillator; applying an offset voltage to the voltage controlled oscillator such that, in operation, in the absence of any voltage applied to the control node, the frequency of the output wave produced by the voltage controlled oscillator is at least half and not greater than the final frequency of the voltage controlled oscillator when frequency lock is established.
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10. A clock recovery method for extracting a clock signal from an input digital signal in a phase lock loop, the method comprising:
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producing, with a voltage controlled oscillator having a control node, an output wave having a frequency that varies in response to a voltage applied to the control node; controlling, with charge pump and loop filter circuitry, the rate of change of the voltage on the control node of the voltage controlled oscillator; performing, with start-up circuitry, frequency discrimination and, in conjunction with the charge pump and loop filter circuitry, adjusting the voltage on the control node of the voltage controlled oscillator; performing phase control and adjusting the voltage on the control node of the voltage controlled oscillator.
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11. A communications method for extracting a clock signal from incoming digital data, the method comprising:
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a step for producing a wave at an output of a voltage controlled oscillator having a frequency that varies in response to a voltage applied to a control node of the voltage controlled oscillator; a step for controlling the rate of change of the voltage on the control node of the voltage controlled oscillator; a step for performing frequency discrimination and for adjusting the voltage on the control node of the voltage controlled oscillator; a step for performing phase control and for adjusting the voltage on the control node of the voltage controlled oscillator; and a step for varying the output of the voltage controlled oscillator until a predetermined number of transitions of the output fit within a time interval of an identifiable discrete segment of the incoming data. - View Dependent Claims (12, 13)
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14. A communications method for extracting a clock signal from incoming digital data, the method comprising:
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a step for producing a wave at an output of a voltage controlled oscillator having a frequency that varies in response to a voltage applied to a control node of the voltage controlled oscillator; a step for controlling the rate of change of the voltage on the control node of the voltage controlled oscillator; a step for performing frequency discrimination and for adjusting the voltage on the control node of the voltage controlled oscillator; a step for performing phase control and for adjusting the voltage on the control node of the voltage controlled oscillator; a step for varying the output of the voltage controlled oscillator until a predetermined number of transitions of the output fit within a time interval of an identifiable discrete segment of the incoming data; and a step for applying an offset voltage to the voltage controlled oscillator such that, in operation, in the absence of any voltage applied to the control node, the frequency of the output wave produced by the voltage controlled oscillator is at least half and not greater than the final frequency of the voltage controlled oscillator when frequency lock is established.
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Specification