Echo cancelling device with frequency sub-band filtering

Claim 1

An echo cancelling device for use between a line receiving an incoming echo-affected signal and a line transmitting an outgoing signal, for cancelling out echo, comprising a plurality of processing channels connected in parallel relation and assigned to successive mutually adjacent sub-bands of the spectral band of the outgoing signal, each of said channels comprising; a subtractor circuit having an additive input and a subtractive input for delivering an output signal at an output; an adaptive filter having an input and an output connected to the subtractive input of said subtractor circuit; a first analysis band-pass filter receiving the incoming echo-affected signal, the output of said first band-pass filter being connected to the additive input of said subtractor circuit; a second analysis band-pass filter, identical to the first band-pass filter, receiving the incoming echo-affected signal and feeding the input of said adaptive filter for delivering an estimated echo value in the sub-band of the corresponding channel to the subtractive input of the subtractor; and a synthesis filter connected to the output of said subtractor circuit for rebuilding the full band of said incoming echo-affected signal and whose output feeds the line transmitting the output signal, means for extracting through filtering for a particular sub-band, the aliasing component originating from another sub-band and for eliminating the aliasing component by adding it to the signal originating from the filter analyzing the incoming echo-affected signal corresponding to said particular sub-band.