RFID-tag communication device

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 digital-transmission-signal output portion operable to generate said transmission signal in the form of a digital signal;
• and
• a table storing a sine-wave or cosine-wave table which represents predetermined sampling values corresponding to respective phases at predetermined sampling points,
• wherein said digital-transmission-signal output portion generates said transmission signal on the basis of said sine-wave or cosine-wave table;
• further comprising a second-cancel-signal output portion operable to generate said second cancel signal on the basis of said sine-wave or cosine-wave table, and a second-cancel-signal control portion operable to control a phase of said second cancel signal, by changing positions of said sine-wave or cosine-wave table from which said sampling values are read out.

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 sine-wave-signal generating portion operable to generate a first sine-wave signal and a second sine-wave signal which have respective different phases;
• an amplitude control portion operable to control amplitudes of said first and second sine-wave signals generated by said sine-wave-signal generating portion;
• and
• a sine-wave synthesizing portion operable to combine together said first and second sine-wave signals the amplitudes of which have been controlled by said amplitude control portion, to synthesize a composite sine-wave signal for radio communication.