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System for interrogating a passive transponder carrying phase-encoded information

  • US 4,725,841 A
  • Filed: 06/30/1983
  • Issued: 02/16/1988
  • Est. Priority Date: 06/30/1983
  • Status: Expired due to Term
First Claim
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1. System for interrogating a transponder carrying encoded information, said system comprising:

  • (a) at least one transponder means for receiving a first signal and for transmitting a second signal in reply thereto, said transponder means including signal transforming means, coupled to receive said first signal as an input, for producing said second signal as an output, said signal transforming means including;

    (1) a plurality of signal conditioning means coupled to receive said first signal, each signal conditioning means providing an intermediate signal having a known delay and a known amplitude modification to said first signal; and

    (2) signal combining means coupled to all of said signal conditioning means, for combining said intermediate signals to produce said second signal, said signal conditioning means and said signal combining means imparting a known informational code to said second signal associated with said transponder means;

    (b) means for transmitting said first signal having a first frequency, said first frequency successively assuming a plurality of frequency values across a prescribed frequency range which is sufficiently wide to resolve the differences in time between the known delays of different ones of said signal conditioning means;

    (c) means for receiving said second signal from said transponder means;

    (d) means, coupled to said transmitting means, for producing a third signal derived from said first signal;

    (e) means, coupled to said receiving means, for producing a fourth signal derived from said second signal;

    (f) means, arranged to receive said third signal and said fourth signal for mixing together said third signal and said fourth signal, thereby to produce a fifth signal; and

    (g) signal processing means, responsive to said fifth signal, for detecting at least some of the frequencies contained in said fifth signal, thereby to determine said informational code associated with said transponder means.

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