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Passive identification system

  • US 3,878,528 A
  • Filed: 10/12/1973
  • Issued: 04/15/1975
  • Est. Priority Date: 10/12/1973
  • Status: Expired due to Term
First Claim
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1. A passive identification system using a given range of frequencies for communication between a transceiver and at least one passive responder, comprising:

  • signal generating means in said transceiver for generatinG a frequency spectrum signal within said given frequency range, which frequency spectrum signal comprises a series of successive discrete frequencies;

    means for transmitting said frequency spectrum to a passive responder, which responder retransmits to said transceiver selected frequencies from said series of successive discrete frequencies;

    means in said transceiver and said responder for changing the frequency of each of said successive discrete frequencies by a given factor;

    means in said transceiver for comparing said frequency spectrum with said retransmitted selected frequencies so as to determine coincidence between each of said frequency changed successive discrete frequencies transmitted to said responder, and the selected frequencies retransmitted from said responder to said transceiver; and

    , means responsive to said comparing means for generating an identification code indicative of said coincidence with respect to each successive discrete frequency in said frequency spectrum signal.

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