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Frequency domain signal reconstruction compensating for phase adjustments to a sampling signal

  • US 5,793,801 A
  • Filed: 07/09/1996
  • Issued: 08/11/1998
  • Est. Priority Date: 07/09/1996
  • Status: Expired due to Term
First Claim
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1. In a digital communications system where transceivers communicate over a communications channel, each transceiver sampling a signal received over the communications channel in accordance with a sampling signal and including an echo canceller for canceling an echo implemented as a digital filter, a method comprising the steps of:

  • inputting to the digital filter a signal transmitted from the transceiver and delaying the input signal through a plurality of delay stages to generate a series of input signals;

    transforming the series of input signals into spectral components to create series of input spectral components;

    multiplying each of the spectral components by a corresponding spectral filter coefficient to generate a corresponding product, the spectral filter coefficients representing an echo transfer function;

    summing the products corresponding to each of the spectral components to generate an output signal from the digital filter corresponding to an expected echo;

    subtracting the filter output signal from the received signal to cancel echo from the received signal;

    determining an error based on an uncancelled echo;

    adapting the spectral filter coefficients of the adaptive filter to minimize the error;

    detecting that the phase of the sampling signal will be adjusted;

    predicting new values of the spectral filter coefficients in the frequency domain to compensate for the sampling signal adjustment including analyzing each spectral filter coefficient as having at least two spectral components with a first spectral component including baseband frequency components and a second spectral component including aliased frequency components;

    adjusting the phase of the sampling signal; and

    using the predicted values of the spectral filter coefficients so that the digital filter output signal accurately models the received signal when the phase of the sampling signal is adjusted.

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