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Highly accurate RF-ID positioning system

  • US 5,594,448 A
  • Filed: 12/15/1994
  • Issued: 01/14/1997
  • Est. Priority Date: 10/22/1993
  • Status: Expired due to Term
First Claim
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1. An antenna configuration for accurately determining the position of a transponder in an RF-ID system comprising:

  • a first and a second balanced receive antenna for receiving a fieldstrength voltage and a phase measurement of a response telegram wherein said first and second receive antennas are physically rotated 90 degrees relative to one another;

    a third reference antenna for receiving a fieldstrength voltage RF signal and a phase measurement of said response telegram and for providing a phase measurement of said response telegram;

    a transmitter antenna for transmitting a charge-up signal to said transponder wherein said transponder is charged to a maximum allowable voltage;

    a first, a second and a third receiver for narrowband filtering said receive fieldstrength voltages of said response telegram;

    a synchronous detector circuitry for rectifying said filtered response signal via phase information of said response telegram provided by said reference antenna;

    a first, a second and a third sample and hold circuit for sampling said synchronized signals for a first portion of said response telegram; and

    a processing circuit for generating a position coordinate relating to a position of said transponder from said sampled signals.

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