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Radio IC card system

  • US 6,018,641 A
  • Filed: 04/10/1997
  • Issued: 01/25/2000
  • Est. Priority Date: 04/15/1996
  • Status: Expired due to Fees
First Claim
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1. An IC card for use with a radio data transmitter/receiver device that transmits a first signal comprising a predetermined pattern and a second radio signal comprising predetermined carrier-modulated data from a transmitting antenna, the IC card comprising:

  • a radio switching means, activated by the predetermined pattern in said first radio signal, comprising;

    a receiving antenna for receiving said first radio signal;

    a surface acoustic wave (SAW) matched filter for extracting said predetermined pattern from said received first radio signal;

    an accumulation circuit for generating an output power accumulated from said SAW matched filter; and

    a switching circuit, activated when said output power from said accumulation circuit exceeds a predetermined threshold value; and

    a data communication unit for receiving said second radio signal from and transmitting a third radio signal comprising data to said transmitter/receiver device, for processing said data, and for transmitting a control signal to said radio switching means after terminating transmission or reception and processing of said data;

    wherein said data communications unit is connected to a battery via said switching circuit for supplying power to said data communication unit in response to activation of said radio switching means.

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