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ROM-based finite impulse response filter for use in mobile telephone

  • US 5,870,431 A
  • Filed: 06/27/1996
  • Issued: 02/09/1999
  • Est. Priority Date: 06/27/1996
  • Status: Expired due to Term
First Claim
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1. A finite impulse response (FIR) filter apparatus comprising:

  • means for receiving an input signal stream having groups of consecutive non-null signals bracketed by groups of consecutive null signals;

    means for storing FIR filter output values, wherein the means for storing stores only FIR filter output values for each of a predetermined set of unique permissible input stream patterns, with the set of permissible input stream patterns including only patterns containing either leading non-null signals followed by trailing null signals, leading null signals followed by trailing non-null signals, all non-null signals or all null signals; and

    means for successively applying sequences of consecutive signals from the input signal stream to the means for storing to read out a sequence of output values corresponding to a filtered version of at least a portion of the input stream.

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