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Electromagnetic identification and location system

  • US 5,072,222 A
  • Filed: 06/26/1990
  • Issued: 12/10/1991
  • Est. Priority Date: 08/08/1986
  • Status: Expired due to Fees
First Claim
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1. An electromagnetic identification and locations system, comprising:

  • at least one interrogator having means for generating an interrogation signal and a position-sensitive antenna arrangement with a primary antenna coil for generating an electromagnetic interrogation field from said interrogation signal and a secondary antenna coil arranged substantially concentrically and being approximately coplanar with said primary antenna coil; and

    at least one responder, having means for absorbing energy of said electromagnetic interrogation field and providing a transmission signal, generator means for generating a pilot signal and a clock from said transmission signal, a code circuit for receiving said clock signal and generating a code signal, and pilot transmission means for generating an AC field from said pilot signal and inducing an AC voltage, having a frequency the same as that of said AC field, in said primary and secondary antennas to produce a first output signal from said primary antenna coil and a second output signal from said secondary antenna coil;

    said interrogator further including identification means for receiving and identifying said code signal from said responder when said responder is present in said interrogation field in order to identify said responder, and a detector for receiving said first output signal and said second output signal to produce a pilot output voltage indicative of a position of said responder relative to said secondary antenna coil.

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