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Adaptive signal discrimination circuit and a method for discriminating high and low level of data signals

  • US 4,939,750 A
  • Filed: 03/14/1989
  • Issued: 07/03/1990
  • Est. Priority Date: 03/17/1988
  • Status: Expired due to Term
First Claim
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1. An adaptive signal discrimination circuit for discriminating high and low levels of data signals, comprising:

  • means for generating a reference signal having a reference level;

    means for receiving data signals having values which vary between high and low levels;

    a first sampling means for sampling the data signals at first discrete times and outputting a first sample signal having a level indicative of the level of the data signals at the first discrete time;

    a second means for sampling the data signals at second discrete times and outputting a second sample signal having a level indicative of the level of the data signals at the second discrete time;

    means for generating a discrimination signal having a discrimination level which varies in proportion to the reference level;

    means for generating timing signals;

    means, responsive to each of the timing signals for discriminating between the high and low levels of the data signals in relation to the discrimination level of the discrimination signal, the first discrete times substantially coinciding with the times of detecting the high level, the second discrete time substantially coinciding with the times of detecting the low level; and

    means for generating an average signal having a value indicative of an average of an absolute value of the level of the first sample signal and that of the second sample signal, and for generating an inversion signal having a value indicative of the inversion of the value of the average signal;

    the reference signal generating means including a low-pass filter having input and output terminals and further including means for selectively applying one of the average signal and the inversion signal to said low-pass filter, said applying means applying the average signal to the input terminal of said low-pass filter when said discriminating means detects the low level of the data signal, said applying means applying the inversion signal to the input terminal of said low-pass filter when said discriminating means detects the high level of the data signal, the reference signal being generated from the output terminal of the said low-pass filter, whereby the discrimination signal adapts to variations of the data signals.

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