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Adjustable echo canceller

  • US 4,862,449 A
  • Filed: 11/16/1987
  • Issued: 08/29/1989
  • Est. Priority Date: 11/17/1986
  • Status: Expired due to Fees
First Claim
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1. An echo canceller including an echo canceller circuit adapted to be coupled between a receive path and a transmit path in a communications system, said echo canceller comprisinga digital filter responsive to a digital input signal for producing a replica signal comprising a plurality of digitized replica samples,said digital filter having an associated plurality of filter coefficients,said digital input signal comprising a plurality of digitized input samples applied to said receive path,each digitized sample of said replica signal being equal to the sum of a plurality of terms, each term being equal to the product of a respective one of said filter coefficients and of a respective factor which is a function of said digital input signal,a subtracter circuit, responsive to said replica signal and to the output signal which appears on said transmit path in response to said input signal being applied to said receive path, for subtracting said replica signal from said output signal,first processing means for first determining each of said respective factors from replica signal samples which are output by the digital filter when all the filter coefficients, except the filter coefficient by which said each factor is multiplied, are equal to zero, andsecond processing means responsive to the factors determined by said first processing means for thereafter determining said filter coefficients from a plurality of output signal samples.

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