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Spread spectrum multipath receiver apparatus and method

  • US 5,081,643 A
  • Filed: 11/16/1990
  • Issued: 01/14/1992
  • Est. Priority Date: 11/16/1990
  • Status: Expired due to Term
First Claim
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1. An apparatus having an input, for adapting to receive a particular path, having the greatest amplitude, of a spread-spectrum signal with multipath, said spread-spectrum signal modulated by a chip-code signal, comprising:

  • a chip-code generator for generating the chip-code signal having the same chip code as the spread-spectrum signal;

    a plurality of shift registers operatively coupled to said chip-code generator for shifting said chip-code signal by a plurality of time delays, each time delay having a duration equal to a time period of one chip of said chip-code signal, said plurality of shift registers having a plurality of taps corresponding to each of said time delays;

    a first ring counter responsive to a second comparator signal for generating a first sequencing signal;

    a first switching device operatively coupled to said first ring counter and to the plurality of taps of said plurality of shift registers, said first switching device responsive to said first sequencing signal for successively switching between said plurality of taps for changing a delay of the chip-code signal with a first time delay;

    a second ring counter responsive to a first comparator signal for generating a second sequencing signal;

    a second switching device operatively coupled to said second ring counter and to the plurality of taps of said plurality of shift registers, said second switching device responsive to said second sequencing signal for successively switching between said plurality of taps for changing a delay of the chip-code signal with a second time delay;

    a first correlator operatively coupled to said input and to said first switching device for generating a first correlation signal by correlating said spread-spectrum signal received at said input with said chip-code signal having the first time delay;

    a second correlator operatively coupled to said input and to said second switching device for generating a second correlation signal by correlating said spread-spectrum signal received at said input with said chip-code signal having the second time delay;

    a difference amplifier for subtracting the second correlation signal from the first correlation signal;

    a first comparator operatively coupled to said difference amplifier for generating the first comparator signal when said difference signal is greater than a first threshold; and

    a second comparator operatively coupled to said difference amplifier for generating the second comparator signal when said difference signal is less than a second threshold.

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