Self-adapting equalizer

A self-adapting equaliser for connection to the reception end of a transmission channel, said transmission channel receiving at the transmission end a useful signal y(t) and a control signal x(t) of period T superposed on the useful signal and of a form which is known at the reception end, the transmission channel supplying at the reception end a distorted signal with a component y'(t) corresponding to the useful signal y(t) and a component x'(t) corresponding to the control signal x(t), said equaliser being characterized in that it comprises:

• a local generator supplying a control signal identical to the control signal x(t) applied to the transmission channel at the transmission end and received in the distorted form x'(t) mixed with the distorted form y'(t) of the useful signal, said control signal being synchronised with said signal x'(t);
• a filter circuit receiving the signal y'(t)+x'(t) from the reception end of the transmission channel and providing at its output the mean value of this input signal and an integer number, (n-1) previous input signals sampled at intervals spaced by the period T of the control signal x(t);
• a first non-recursive transversal filter comprising a cascade-connected impedance array with intermediate taps, with its input connected to receive the signal x"(t) provided by the filter circuit and having its weighting coefficients controlled so as to minimise the correlation functions of the signals at the intermediate taps and the signal which is the difference between its output signal x(t) and the control signal x(t) supplied by the local generator;
• a subtractor circuit receiving on an additive first input signal y'(t)+x'(t) obtained at the reception end of the transmission channel and on a subtractive second input the signal x"(t) supplied by the filter circuit, and providing at its output a signal equal to the difference between the two signals applied to its inputs;
• and
• a second transversal filter with the same cascade-connected impedance array and the same weighting coefficients as the first transversal filter, receiving on its input the output signal of the subtractor circuit and providing at its output the equalised useful signal y(t).