Echo canceller utilizing pseudo-logarithmic encoding law

Details Echo canceller utilizing pseudo-logarithmic encoding law Echo canceller utilizing pseudo-logarithmic encoding law

1981-12-16

1984-08-21

Rubinson, G. Z.

H04B 320

Patent

active

044671466

ABSTRACT:
A digital echo canceller is arranged in a digital telephone circuit for PCM-signals in accordance with a pseudo-logarithmic encoding law, for example the A-law of the CCITT, in the proximity of a subscriber line interface circuit having a codec in order to cancel in the near-end speech signals S supplied by the codec to the send path the echo effect Y of the far-end speech signals X conveyed to the codec by the receive path. The echo canceller has circulating shift registers for the signals X and the coefficients C, digital correlation calculation means for obtaining the coefficients C, digital convolution calculation means for obtaining an echo cancellation signal y and digital subtraction calculation means for obtaining near-end speech signals R in which the echo effect Y has been substantially cancelled. Each of the digital correlation, convolution and subtraction calculation means incorporates only one pseudo-logarithmic-to-linear code converter, and furthermore the digital subtraction calculation means incorporates only one linear-to-pseudo-logarithmic code converter.

REFERENCES:
patent: 4113997 (1978-09-01), Horna

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