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Station, a passive portable object and apparatus for the remote exchange of information between the passive portable object and the station

  • US 5,838,235 A
  • Filed: 09/05/1996
  • Issued: 11/17/1998
  • Est. Priority Date: 09/06/1995
  • Status: Expired due to Fees
First Claim
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1. An apparatus for the exchange of information by electromagnetic coupling between a portable object and a station, in which said station comprises:

  • a first generator of a first alternating voltage with a first selected frequency,a first resistive station element with a first terminal linked to the first generator and a second terminal,a series arrangement linked to the second terminal and having at least a first inductive station element, a first capacitive station element and a second resistive station element, said arrangement having a pair of terminals and being able to create a second alternating voltage at said terminals,station processing means connected to the first and second terminals of the first resistive station element and able to process phase variations between the first and second alternating voltages, andin which said portable object comprises;

    an electronic circuit comprising a first inductive object element and a first capacitive object element, said circuit being switchable between an inactive state and an active state in which it forms a resonant circuit with the first inductive station element,object processing means able to switch the electronic circuit as a function of information to be transmitted to the station, the phase variation between the first and second alternating voltages induced by this switching enabling the station processing means to deduce therefrom said information,wherein said station further comprises;

    a second generator of a third alternating voltage of a second selected frequency different from the first frequency,wherein the portable object also comprises;

    a second inductive object element independent of the first inductive object element and having terminals,a second capacitive object element linked to the terminals of the second inductive object element, said second inductive object element being able to form a tuned loop with the second inductive station element in order to generate at the terminals of the second inductive object element an inducted alternating supply voltage in the presence of the magnetic field created by the second inductive station element, andwherein the station also comprises a filtering circuit of dipole type interposed between one of the electrodes of the first capacitive station element and one of the terminals of the first inductive station element, said filtering circuit being able to behave essentially as an inductance at the first frequency and an impedance of high value at the second frequency.

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