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Echo canceller

  • US 4,998,241 A
  • Filed: 12/01/1989
  • Issued: 03/05/1991
  • Est. Priority Date: 12/01/1988
  • Status: Expired due to Fees
First Claim
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1. An echo canceller comprising(a) an adaptive filter having first input means, control input means, and an adaptation rate controllable in response to a control signal received at the control input means;

  • (b) a control unit for producing the control signal for the adaptive filter and including;

    (i) a plurality of input means for receiving respective input signals having respective signal powers;

    (ii) means for determining respective mean values of the respective input signals based on the respective signal powers, which input signals include a signal received at the first input means and an echo cancelled signal;

    (iii) a decision circuit for(A) establishing whether the mean value of the signal received at the first input means exceeds a first threshold value; and

    (B) supplying an output signal for setting the adaptation rate to zero when the mean value of the signal received at the first input means is below the first threshold value;

    (c) means for supplying a second threshold value which is a function of the mean value of an echo cancelled signal, which second threshold value controls the adaptation rate according to the function in the case in which the adaptation rate is not set to zero by the decision circuit.

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