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Surface acoustic wave unique word detector and coherent demodulator

  • US 4,169,286 A
  • Filed: 06/09/1978
  • Issued: 09/25/1979
  • Est. Priority Date: 06/09/1978
  • Status: Expired due to Term
First Claim
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1. A coherent unique word detector and differential demodulator for a digital code differential phase-shift signal comprising:

  • a piezoelectric crystal substrate having a planar surface;

    an interdigital input transducer on the planar surface of said substrate for launching onto said substrate surface acoustic waves;

    a first interdigital output transducer on the planar surface of said substrate positioned to intercept surface acoustic waves launched by said input transducer, and having a first group of fingers arranged to provide a maximum output in response to surface acoustic waves representing a predetermined unique word or its inverse, and a second group of fingers arranged in a predetermined alternating sequence, said second group of fingers being further from said input transducer than said first group of fingers;

    a second interdigital output transducer on the planar surface of said substrate positioned to intercept surface acoustic waves launched by said input transducer, and having a group of fingers arranged in said predetermined alternating sequence and positioned with respect to said input transducer to provide a maximum output in response to surface acoustic waves representing a coherent reference at the same instant in time as a maximum output is provided by said first interdigital output transducer in response to surface acoustic waves representing said predetermined unique word; and

    threshold means connected to said first and second interdigital output transducers for detecting the auto-correlation peak of said predetermined unique word as represented by a maximum output from said first interdigital output transducer using the maximum output of said second interdigital output transducer as a coherent reference.

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