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Self-adaptive trans-hybrid balance filter

  • US 5,828,589 A
  • Filed: 02/23/1996
  • Issued: 10/27/1998
  • Est. Priority Date: 02/23/1995
  • Status: Expired due to Fees
First Claim
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1. An adaptive balance filter, comprising:

  • a transmission path;

    a reception path;

    an adaptive filter having a signal output, a coefficient output for outputting filter coefficients, an error signal input, and a signal input coupled to said transmission path;

    a main filter having a signal output, a signal input coupled to said transmission path, and a coefficient input for loading filter coefficients;

    a first subtractor having one input coupled to said reception path, another input coupled to the signal output of said main filter, and an output forming a further course of said reception path;

    a second subtractor having one input coupled to said reception path, another input coupled to the signal output of the adaptive filter, and an output coupled to the error signal input of said adaptive filter;

    a transfer device being connected between the coefficient output of said adaptive filter and the coefficient input of said main filter and having a control input for loading the filter coefficients of said adaptive filter into said main filter upon an appearance of a corresponding copy signal; and

    a transfer control device having first, second and third inputs, the first input being coupled to the output of said second subtractor, the second input being coupled to the one input of said second subtractor, and the third input being coupled to the output of said main filter;

    said transfer control device ascertaining echo attenuations of said adaptive filter and said main filter from signals at the first, second and third inputs, comparing two echo attenuations with one another, and sending a corresponding copy signal to said transfer device in the event that the echo attenuation of said adaptive filter is higher than the echo attenuation of said main filter; and

    said transfer control device having a quality comparison device and a copy control device;

    said transfer control device including;

    a third subtractor having one input forming the second input and another input forming the third input of said transfer control device;

    a first absolute value former having an input forming the first input of said transfer control device;

    a second absolute value former having an input being connected to the one input of said third subtractor;

    a third absolute value former connected downstream of said third subtractor;

    first, second and third logarithm modules each being connected downstream of a respective one of said first, second and third absolute value formers and each having an output;

    a fourth subtractor having inputs each being connected to the output of a respective one of said first and second logarithm modules;

    a fifth subtractor having inputs each being connected to the output of a respective one of said second and third logarithm modules;

    first and second low-pass filters each being connected downstream of a respective one of said fourth and fifth subtractors and each having an output; and

    a sixth subtractor having inputs being connected to the outputs of said first and second low-pass filters, and an output supplying a quality difference signal;

    said copy control device having an input being coupled to the output of said sixth subtractor, for comparing the quality difference signal with a first comparison value and generating a copy signal for said transfer device if the quality difference signal and the first comparison value differ in a certain direction, the first comparison value being set equal to a current value of the quality difference signal.

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