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METHOD AND APPARATUS FOR MEASURING MULTIPATH DISTORTION

  • US 3,869,673 A
  • Filed: 05/21/1973
  • Issued: 03/04/1975
  • Est. Priority Date: 05/21/1973
  • Status: Expired due to Term
First Claim
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1. In an FM receiver having a sequentially coupled radio frequency amplifier, mixer, intermediate frequency amplifier, limiter, frequency modulation detector and audio output stages;

  • a circuit for providing a quantitative measure of the distortion present in a received signal due to propagation of that signal along paths of dissimilar lengths comprising;

    an amplitude modulation detector having an input coupled to the receiver prior to the limiter and having an output;

    multiple input amplifier means for providing an output signal the magnitude of which varies directly as a function of the magnitude of each input signal;

    means coupling the output of the amplitude modulation detector to at least one of the amplifier means multiple inputs;

    means coupling the output of the frequency modulation detector to at least another of the amplifier means multiple inputs;

    indicator means coupled to the output of said amplifier means output to indicate the quantitative measure of said distortion present in a received signal; and

    wherein the amplifier means comprises a multiplier circuit for forming the instantaneous product of the signals presented to the multiple inputs.

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