Patent ID: 6161762
Filing Date: 2000-12-19
Classification: G06K

Abstract:
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.