×

Adaptive digital echo cancellation circuit

  • US 4,268,727 A
  • Filed: 03/14/1979
  • Issued: 05/19/1981
  • Est. Priority Date: 03/14/1979
  • Status: Expired due to Term
First Claim
Patent Images

1. An adaptive digital echo cancellation circuit for a telephone line circuit comprising:

  • finite impulse response digital filter means having a plurality of delay stages and having coupled thereto a plurality of received digital words, for obtaining for each sample interval of N words the product of N of said digital words and a plurality of updated coefficients each associated with one of said digital filter stages to derive an output representative of the value of an undesired signal portion of a plurality of transmitted digital words;

    summation circuit means having coupled thereto a plurality of transmitted digital words having superimposed thereon an undesired signal portion, and the output of said digital filter representative of the value of said undesired signal portion, and having an output comprised substantially of said transmitted digital words;

    correlator means coupled to said digital filter means for obtaining an N term average correlation for each sample interval of N words of digital signals representative of N of said transmitted digital words and N of said received digital words to derive a control output representative of the instantaneous undesired signal present in said received transmitted digital words to vary said coefficients each N word sample interval in accordance with said control output; and

    nonlinear circuit means for deriving said digital signals respectively representative of said transmitted and received digital words, such that said representative digital signals are of a bit length less than the bit length of said respective transmitted and received digital words.

View all claims
  • 5 Assignments
Timeline View
Assignment View
    ×
    ×