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Tag communication device and tag communication method

  • US 8,334,754 B2
  • Filed: 03/17/2008
  • Issued: 12/18/2012
  • Est. Priority Date: 06/01/2007
  • Status: Active Grant
First Claim
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1. A tag communication device for performing wireless communication with an RFID tag by transmitting an interrogating wave from an antenna to a mobile object with the RFID tag attached in a predetermined communication range, the tag communication device comprising:

  • Doppler measurement means for obtaining a Doppler signal for every frequency from transmission waves with a plurality of frequencies and reflected waves thereof;

    phase difference detection means for detecting a phase difference of the Doppler signals of two frequencies of the Doppler signals for every frequency; and

    communication control means for controlling the transmission of the interrogating wave so as to transmit the interrogating wave when the phase difference is detected by the phase difference detection means, and so as not to transmit the interrogating wave when the phase difference is not detected by the phase difference detection means.

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