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Proximity identification system with flux concentration in operating region

  • US 5,159,332 A
  • Filed: 03/14/1991
  • Issued: 10/27/1992
  • Est. Priority Date: 06/05/1989
  • Status: Expired due to Fees
First Claim
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1. A proximity identification system comprising:

  • a reader antenna comprising at least one coil wound around each of a group of four ferrite rods in a diamond-shaped pattern and polarized and placed so as to generate strong diagonal and lateral flux lines within said diamond-shaped pattern;

    a reader section having a reader circuit means connected to the reader antenna for simultaneously supplying a power signal to the reader antenna and detecting an identifier signal, said reader circuit means comprising;

    (a) an oscillator connected to a power amplifier connected to the reader antenna for generating said power signal, (b) a detector means connected to the reader antenna for detecting said identifier signal, and (c) an amplifier to convert said detected signals to pulses; and

    an identifier tag section having an identifier antenna formed of a ferrite rod with a winding, and an identifier circuit means connected to the winding for generating an identifier signal for modulating the impedance of the tag winding with the modulation changing the flux field around the tag antenna and the changing flux field also changing the flux in the reader antenna when said identifier antenna is disposed within said diagonal flux lines generated by the reader antenna.

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