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Device and method for linear listener echo cancellation

  • US 5,319,636 A
  • Filed: 11/14/1991
  • Issued: 06/07/1994
  • Est. Priority Date: 11/14/1991
  • Status: Expired due to Term
First Claim
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1. A listener echo canceller (LECR) for reducing a listener echo interference in a digital communication system having a selected sampling interval, and having an input and an output, said input comprising a sum of a desired signal and a listener echo interference, and said output being free of listener echo interference, said listener echo canceller comprising:

  • a bulk delay line means, operably coupled to receive and store at least one sample of one of;

    the input and the output of said listener echo canceller, to provide a bulk delay line output;

    an adaptive listener echo interference estimator means, operably coupled to receive the bulk delay line output for utilizing a listener echo bulk delay relative to the received data signal in place of a talker far echo bulk delay relative to the near echo to generate an estimate of the listener echo interference; and

    an interference cancelling means, operably coupled to receive the input of the listener echo canceller and the estimate of the listener echo interference, for producing said output by subtracting said estimate of the listener echo interference from said input of the listener echo canceller,wherein said adaptive listener echo interference estimator means further includes compensating means, operably coupled to receive the input of the LECR and to receive a phase-corrected listener echo estimate, for compensating a frequency offset in the said estimate of the listener echo interference utilizing a talker far echo frequency offset as an estimate of far echo cancellation, andwherein the means for compensating the frequency offset includes;

    a phase-error estimating means, operably coupled to receive the input of the LECR and to receive a phase-corrected listener echo estimate, for generating a phase error that is a phase difference between the estimate of the listener echo estimate and the said input of the LECR; and

    a phase-locked loop, operably coupled to receive the said phase error, for generating a phase correction estimate; and

    a phase-correction means, operably coupled to receive the phase correction estimate, for generating a phase-corrected listener echo estimate.

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