H - Electricity – 04 – M
Patent
H - Electricity
04
M
363/12, 379/64,
H04M 1/74 (2006.01) H04B 3/23 (2006.01) H04B 15/00 (2006.01) H04M 3/18 (2006.01)
Patent
CA 1181149
33 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 con- veyed to the codec by the receive path. The echo can- celler comprises circulating shift registers for the sig- nals X and the coefficients C, digital correlation cal- culation means for obtaining the coefficients C, digital convolution calculation means for obtaining an echo can- cellation signal ? and digital subtraction calculation means for obtaining near-end speech signals R in which the echo effect Y has been subtantially cancelled. Com- plexity and cost are reduced and performance is improved in that the echo canceller is arranged such that each of the digital correlation, convolution and subtraction cal- culation means incorporates only one pseudo-logarithmic- to-linear code converter, and furthermore the digital sub- traction calculation means incorporates only one linear to-pseudo-logarithmic code converter.
391919
Lucent Technologies Inc.
Van Steinburg C.e.
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