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RFID-tag communication device

  • US 8,135,360 B2
  • Filed: 07/31/2006
  • Issued: 03/13/2012
  • Est. Priority Date: 02/04/2004
  • Status: Active Grant
First Claim
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1. An RFID-tag communication device including an antenna from which a transmission signal is transmitted toward an RFID tag and through which a reply signal transmitted from the RFID tag in response to the transmission signal is received, for radio communication with the RFID tag, said RFID-tag communication device comprising:

  • a first-cancel-signal output portion operable to generate a digital first cancel signal for suppressing a leakage signal from a received signal which is received through said antenna and which contains said leakage signal as well as said reply signal, said leakage signal being a part of said transmission signal which is transmitted from said antenna and which is returned to and received by said antenna;

    a first-cancel-signal control portion operable to control an amplitude and/or a phase of said first cancel signal generated by said first-cancel-signal output portion;

    a first-cancel-signal D/A converting portion operable to convert said first cancel signal, after said first cancel signal is generated by said first-cancel-signal output portion and controlled by said first-cancel-signal control portion, into an analog signal;

    a first signal combining portion operable to combine together the analog first cancel signal generated by said first-cancel-signal D/A converting portion, and said received signal, to obtain a first composite signal;

    a second-cancel-signal output portion operable to generate a digital second cancel signal for suppressing said leakage signal from said received signal;

    a second-cancel-signal control portion operable to control an amplitude and/or a phase of said second cancel signal generated by said second-cancel-signal output portion;

    a second-cancel-signal D/A converting portion operable to convert said second cancel signal generated by said second-cancel-signal output portion, into an analog signal;

    a second signal combining portion operable to combine together the analog second cancel signal generated by said second-cancel-signal D/A converting portion, and said first composite signal, to obtain a second composite signal;

    a demodulating portion operable to demodulate said second composite signal generated by said second signal combining portion; and

    a direct-current-component detecting portion operable to detect a direct current component of the second composite signal demodulated by said demodulating portion, andwherein said second-cancel-signal control portion controls a phase of said second cancel signal on the basis of the direct current component of the demodulated second composite signal detected by said direct-current-component detecting portion.

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