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Identification system using coded passive transponders

  • US 4,096,477 A
  • Filed: 04/22/1977
  • Issued: 06/20/1978
  • Est. Priority Date: 10/06/1975
  • Status: Expired due to Term
First Claim
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1. An identification system comprisingtransmitter means for transmitting an electromagnetic signal;

  • a passive surface acoustic wave identifier adapted to produce a coded electronic reply in response to an electromagnetic signal, comprising a piezoelectric substrate, an input transducer carried by the piezoelectric substrate, a plurality of output transducers carried by the substrate and spaced from said input transducer at preselected intervals, and programming means for programming said output transducers to emit an electronic reply having a preselected sequential time order in response to a surface acoustic wave propogated by said input transducer, said programming means comprising pad means overlying said substrate in a zone intermediate said input transducer and an output transducer, whereby pressure applied to said substrate through said pad means renders said substrate non-conductive to a surface acoustic wave in said zone, thereby rendering any output transducer spaced distally of said pad means unresponsive to a surface acoustic wave propagated by said input transducer, and producing a preselectable variation in the coded electronic reply of said output transducers responsive to an electromagnetic signal;

    receiver means for receiving said coded electronic reply; and

    decoder means for matching the coded electronic reply of said identifier with stored coded pulse patterns.

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