Phase and frequency comparator
AssigneeThomson-CSF
InventorJean-Jacques Thiebaut
Life of this patent
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Abstract
The comparator comprises a circuit for detecting the sign of the phase-shift of the reference signal relatively to the second signal for a predetermined phase of the latter. It delivers a corresponding binary phase difference signal. A second circuit selects those changes in values of the phase difference signal which occur for a phase of the reference signal comprised in a predetermined phase interval, and are thus surely representative of a change in the sign of the frequency difference.
Claims3
A phase and frequency comparator having first and second inputs for respectively receiving a reference signal of period T and a second signal, and comprising:
- a comparison circuit coupled to said first and second inputs, and comprising means for, each time said second signal has a predetermined phase .phi..sub.o for which the amplitude of said second signal is zero, determining the sign of the phase-shift, measured between - .pi. and + .pi. , of said reference signal relatively to said second signal, and delivering to said output a phase-shift digital signal having one or the other of two values depending upon the sign of this phase-shift;
- and a second circuit coupled to said first input, and to said output of said comparison circuit, comprising comparison means and gating means for detecting those particular phase-shift digital signals which simultaneously fulfill the two following conditions (i) they differ in value from the preceding phase-shift digital signal and (ii) they occur while the phase of the reference signal is included in a limited phase interval comprising one and only one value for which the amplitude of the reference signal is zero, and delivering to said output of said second circuit a frequency difference signal, the value of which is equal to the value of the last detected one of said particular phase-shift signals.
Dependencies are inferred from the claim text.