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Adaptive digital filter including low-pass filter

  • US 5,146,470 A
  • Filed: 09/28/1990
  • Issued: 09/08/1992
  • Est. Priority Date: 09/28/1989
  • Status: Expired due to Term
First Claim
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1. An adaptive digital filter for estimating a response characteristic of a signal path by monitoring a sampled output signal of said signal path, estimating a predetermined number of filter coefficients which represent the response characteristic of the signal path, and generating an estimated output signal of said signal path using a plurality of successive sampled input signals of the signal path and estimated filter coefficients, wherein an estimation is carried out so that a difference between said output signal and said estimated output signal is reduced, the filter comprising:

  • an input signal register for holding a plurality of sampled input signals which have been sampled since a predetermined number of cycles before the current time;

    a filter coefficient register for holding said predetermined number of filter coefficients which respectively correspond to the plurality of sampled input signals;

    a convolution calculating means for calculating a convolution between said input signal and said estimated response characteristic using said plurality of successive sampled input signals which are held in said input signal register, and said estimated filter coefficients which are held in said filter coefficient register;

    an error obtaining means for obtaining a difference between said sampled output signal of said signal path and said convolution as an error in said estimation; and

    a filter coefficient estimating means for estimating said predetermined number of filter coefficients so that said error is reduced;

    said filter coefficient estimating means comprising a filter coefficient renewing means for each of said predetermined number of filter coefficients, for renewing the corresponding filter coefficient in each cycle of sampling, and whereinsaid filter coefficient renewing means comprisesa multiplier for obtaining a product of one of said sampled output signals corresponding to the filter coefficient renewing means, and said sampled input signal,an integrating means for integrating an output of said multiplier to extract a component of said filter coefficient corresponding to the filter coefficient renewing means,a power calculating means for calculating a power of said one of said sampled output signals corresponding to the filter coefficient renewing means, anda divider for dividing an output of the integrating means by an output of the power calculating means.

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