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US 4,791,386 AGranted
Digital phase-locked loop with random walk filter
AssigneeSumitomo Electric Industries, Ltd.
InventorNobuo Shiga
Life of this patent
Estimating the term…
Abstract
A digital phase-locked loop in which the lead or lag of the phase of the input is compared to the phase of the output of the loop and the occurrences of the advance or retardation are filtered in a random walk filter in order to phase control the output. According to the invention, the time trend of the advance or retardation is determined. If there is a significant run of either advance or retardation, the random walk filter is adjusted so as to more quickly provide correcting output.
Claims7
A digital phase-locked loop circuit, comprising:
- means for determining a phase of an input signal relative to an output signal to selectively supply one of a lead output and a lag output;
- a random walk filter receiving said lead and lag outputs to thereby supply one of a phase advance output and a phase retard output;
- phase control means receiving said phase advance and retard outputs and a stable oscillation signal for providing a phase compensated signal being said output signal;
- phase deviation trend detection means receiving said lead and lag outputs for detecting a trend of a deviation of said phase to thereby produce a phase trend indication signal;
- and
- a reference value control means for altering a reference value supplied to said random walk filter responsive to said phase trend indication signal.
3 more elements
A method of synchronizing a phase locked loop, comprising the steps of:
- determining a phase of an input signal relative to an output signal;
- selecting a lead output or a lag output responsive to said determining step;
- determining occurrences of said lead output and said lag output relative to each other and to a reference value to thereby select a phase advance condition or a phase retard condition;
- providing a phase compensated signal related to said input signal responsive to said selected phase advance and retard conditions, said phase compensated signal being said output signal;
- detecting a trend of a deviation of said phase;
- and
- varying said reference value in response to said detected trend.
4 more elements
Dependencies are inferred from the claim text.