Method and apparatus for measuring distant echo delay in an echo cancelling arrangement

摘要

Method and apparatus for measuring the delay of the distant echo in an echo cancelling arrangement comprising a near echo canceller, a delay line and a distant echo canceller using the steps of transmitting, by modulation of a carrier, a data sequence having a periodic autocorrelation function with sidelobes of negative or zero value, this sequence having a duration at least equal to the maximum value of the delay to be measured and a number of elements determined by the accuracy desired for measurement of the delay; calculating the correlation function between the data of a next transmitted sequence and the data formed by demodulating the received signal and storing calculated samples of the correlation function in a memory; and determining, among the samples stored, the sample corresponding to the maximum of the correlation function and the rank of that sample.