Patent ID: 7573389

Claim:
A radio-frequency identification tag communication device for radio communication with a radio-frequency identification tag, by transmitting a transmission signal from a transmitter antenna toward the radio-frequency identification tag, and receiving a reply signal transmitted from the radio frequency identification tag in response to the transmission signal, through a receiver antenna comprising a plurality of antenna elements, said radio-frequency identification tag communication device comprising: a directivity control portion configured to control a directivity of said transmitter antenna comprising a plurality of antenna elements; and an adaptive weight control portion configured to implement an adaptive control of a weight given to a received signal received by each of said plurality of antenna elements of said receiver antenna comprising a plurality of antenna elements, and a weight given to said transmission signal transmitted from each of said plurality of antenna elements of said transmission antenna; wherein said directivity control portion is configured to control at least one of a phase and an amplitude of a transmission signal transmitted from each of said plurality of antenna elements, for thereby controlling the directivity of the transmitter antenna and wherein the transmission signals respectively transmitted from said plurality of antenna elements of said transmitter antenna and the received signals respectively received by said plurality of antenna elements of said receiver antenna have a same frequency, said adaptive weight control portion controls the weight given to the said received signals, such that the weight given to said received signals is different from the weight given to the said transmission signals.