Patent ID: 8040222

Claim:
A radio-frequency tag communication system comprising: a radio-frequency tag; a radio-frequency tag communication device configured to transmit a transmitted signal toward the radio-frequency tag, and to receive a reply signal transmitted from the radio-frequency tag in response to said transmitted signal, for thereby effecting radio communication with said radio-frequency tag; and at least one reference tag disposed fixedly in an area of communication of the radio-frequency tag communication system and configured to transmit a reply signal in response to said transmitted signal, for thereby effecting radio communication with said radio-frequency tag communication device, wherein said radio-frequency tag communication device includes a directivity control portion configured to control a directivity of communication with said radio-frequency tag, on the basis of a result of the radio communication of the radio-frequency tag communication device with said at least one reference tag, wherein said radio-frequency tag communication device further includes an effective-communication-range determining portion configured to determine an effective range of communication of the radio-frequency tag communication device with said radio-frequency tag, by detecting a position of each of said at least one reference tag while the directivity of communication is changed by said directivity control portion, and said directivity control portion controls the directivity of communication with said radio-frequency tag on the basis of a result of determination by said effective-communication-range determining portion, and wherein said radio-frequency tag communication device determines said effective range of communication, such that the position of said radio-frequency tag determined by said effective-communication-range determining portion forms a boundary condition of said radio-frequency tag.