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Contact/contactless smart card having customizable antenna interface

  • US 6,161,762 A
  • Filed: 12/28/1998
  • Issued: 12/19/2000
  • Est. Priority Date: 12/31/1997
  • Status: Expired due to Term
First Claim
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1. A data transaction device having a contactless mode of operation and comprising:

  • an antenna coil coupled to a processing unit via an antenna interface for allowing contactless data transmission between the data transaction device and a remote transceiver, anda circuit within the antenna interface including a variable loading means for modulating a signal transmitted by the remote transceiver and received by said antenna coil with outgoing data generated by the processing unit for transmitting via the antenna coil to the remote transceiver;

    the variable loading means being connected in series with a load seen by the antenna coil and having a capacitance connected across said load so as to effect a change in impedance of the load seen by the antenna coil thus allowing amplitude and/or phase modulation of said signal without complete interruption thereof and regardless of the magnitude of an external capacitance connected across or forming part of said load.

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