Patent ID: 8089360

Claim:
A radio-frequency tag communication device configured to transmit a transmitted signal toward a radio-frequency tag, and to receive a reply signal transmitted from the radio-frequency tag in response to the transmitted signal, for thereby effecting radio communication with the radio-frequency tag, said radio-frequency tag communication system comprising: a receiver array antenna device consisting of a plurality of antenna elements each provided for receiving said reply signal; a cancel-signal generating portion configured to generate a cancel signal for eliminating a leakage signal that is a part of said transmitted signal, which part is received by said receiver array antenna device; a cancel-signal control portion configured to control a phase and/or an amplitude of said cancel signal generated by said cancel-signal generating portion; a received-signal combining portion configured to combine together received signals received by said plurality of antenna elements, to obtain a composite signal; and a directivity control portion configured to control a directivity of reception of said reply signal, said radio-frequency tag communication device being configured to concurrently control the transmission of said transmitted signal and the reception of said received signals, and to apply said cancel signal generated by said cancel-signal generating portion to said received-signal combining portion, for combining together the received signals and the cancel signal, and said cancel-signal control portion sets an initial value of the phase or the amplitude, or both, of said cancel signal, on the basis of the directivity of reception of said reply signal controlled by said directivity control portion.