Patent ID: 8135360
Filing Date: 2012-03-13
Classification: G06K

Abstract:
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, and wherein 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.