Phase/frequency comparator for timing recovering circuit

Details Phase/frequency comparator for timing recovering circuit Phase/frequency comparator for timing recovering circuit

1992-02-19

1994-03-22

Chin, Stephen

Pulse or digital communications

Spread spectrum

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331 11, 331 25, H04L 7033

Patent

active

052971732

ABSTRACT:
The phase/frequency comparator comprises a known phase comparator for comparing the phases of an digital input signal with a clock signal of which the period varies to within one time interval with respect to the period of the input signal. Such a phase comparator produces a first error signal whose sign, and preferably magnitude, vary as a function of the difference between the phases. The phase/frequency comparator is intended to produce a second error signal which replaces the first error signal and whose sign, and preferably magnitude, vary as a function of the difference between the periods. According to a preferred embodiment, a phase shift assessing circuit detects a predetermined phase shift, e.g. substantially equal to 0, between the clock signal and the input signal during a clock period. A sign detecting circuit detects the sign of the difference between the periods for the predetermined phase shift, and a logic circuit derives two signals having pulse widths as a function of said periods thereby deriving the second error signal by differentiation. The phase/frequency comparator is particularly intended for a phase locked loop for recovering the timing of the input signal.

REFERENCES:
patent: 4605908 (1986-08-01), Broughton
patent: 4672329 (1987-06-01), Hikawa
patent: 4803705 (1989-02-01), Gillingham et al.
patent: 5015970 (1991-05-01), Williams et al.
"A Self Correcting Clock Recovery Circuit" by Charles R. Hogge, Jr. Journal of Lightwave Technology, vol. LT-3, No. 6, Dec., 1985 pp. 1312-1314.

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