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Protection of communication between an electromagnetic transponder and a terminal

  • US 9,507,975 B2
  • Filed: 04/18/2012
  • Issued: 11/29/2016
  • Est. Priority Date: 06/03/2011
  • Status: Active Grant
First Claim
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1. A method to protect communication between an electromagnetic transponder and a terminal, comprising:

  • attempting to transmit a polling request by the terminal; and

    allowing transmission of the polling request only when the electromagnetic transponder is in mechanical contact or in quasi-mechanical contact with a terminal package, the package including a communication antenna wherein the allowing includes;

    storing a no-load value of current in an oscillating circuit of the terminal when no transponder is in a field of the terminal;

    periodically measuring a first value of current in the oscillating circuit of the terminal;

    based on a first comparison, while the first value is determined to equal the no-load value, repeating the periodically measuring;

    based on the first comparison, when the first value is determined not to equal the no-load value;

    calculating a ratio between the no-load value of current and the first value of current;

    storing the calculated ratio in a second value;

    performing a second comparison between said second value to a third value of said calculated ratio, said third value calculated in a previous iteration; and

    when the second value is determined to be different from the third value, repeating the periodically measuring, the calculating the ratio, the storing the calculated ratio, and the performing the second comparison.

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