Compagnie Industrielle Des Telecommunications Cit-alcatel

Jean-Philippe Haag

Michel Levy

An echo canceller for a full-duplex carrier modulation transmission system terminal. The echo canceller includes a digital time-domain complex transversal filter with controlled weighting coefficients and an offset equal to a submultiple l of a Baud period .DELTA. related to a rate at which a stream of complex symbols is received at the input of the filter. These complex symbols include complex symbols outputted by a coder of a transmitter of the terminal at the rate l/.DELTA. interleaved with l-1 null symbols. The transversal filter output is connected to a digital modulator operated at the transmitter carrier frequency with instantaneous values updated at intervals equal to the Baud period to generate a passband echo copy signal. The invention is of particular benefit in transmission systems in which the product of the transmission carrier frequency and the Baud period is an integral multiple of l/4, as digital implementation of the modulator is then extremely simple.

Growing community of inventors

Paris, France

Jean-Philippe Haag