PHN 12180 1988-04-20 Digital echo canceller A digital echo canceller ¢1! with a good protection against double-talk comprises a first filter ¢9! for the echo cancellation proper, a second adaptive filter ¢11! for making continuously adapted filter coefficients available to the first filter ¢9! and gate means ¢15! which will only apply the adapted filter coefficients to the first filter ¢9! if certain conditions are satisfied. In the echo canceller ¢1! a specific filter combination is used, in which the first filter ¢9! is a time-domain programmable filter (TDPF) and the second filter ¢11! is a frequency-domain block-adaptive (FDAF), and further means ¢20,20(1)! are provided that are arranged in cascade with the gate means ¢15! for transforming the frequency-domain filter coefficients ¢W(p;m)! of the FDAF ¢11! into time-domain filter coefficients ¢W(i;m)! for the TDPF ¢9!. These measures result in the advantages of a negligible delay in the echo cancellation by the TDPF ¢9!, and of the possibility to improve in a simple manner the convergence behaviour of the FDAF ¢11! and considerably reduce its computational complexity. ¢Figure 3!
DIGITAL ECHO CANCELLER