Patent ID: 6028927
Filing Date: 2000-02-22
Classification: H04N,H04Q

Abstract:
A method for detecting the presence of a periodic signal corresponding to a state of a communication process from amongst a set of signals, said periodic signal having a period of occurrence T during at least a predetermined duration T.sub.ON, the method comprising:a) a discrimination step during which said periodic signal is discriminated from the set of signals and an output signal is delivered, the level of the output signal being representative of the result of the discrimination of said periodic signal in said set of signals,b) a sampling step during which the level obtained in said discrimination step is sampled in ln samples over a duration greater than one repetition period T;c) a correlation step during which there is made correspondence for the samples obtained in said sampling step for each sample of ranking i varying from 1 to ln, of a state value B(i) representative of a level of each sample, and, over at least a first part of the sampling duration, a true correlation value SR is calculated, by cumulating, for each pair of samples of ranking i and i+Z, the instantaneous value of correlation between the state value B(i) and the state value B(i+Z), the samples of ranking i and i+Z being located at instants shifted by a period T, Z being the number of samples taken during a period T of the signal to be detected,d) a rate calculation step during which the rate r of samples representative of the presence of said periodic signal is measured over at least a second part of the sampling duration, this rate r being the ratio of the number of samples for which level is representative of the presence of the signal to be detected, over the total number of samples in the second part of the sampling duration,e) a theoretical evaluation step during which the determination of at least one theoretical correlation average value is carried out, andf) a decision step during which the true correlation value SR is compared with each theoretical correlation average value and the presence or absence of the periodic signal to be detected, and the corresponding state of the communication process, is deduced according to the result of this comparison.