Radio-Frequency Tag Communication System

• US 20080278291A1
• Filed: 11/12/2007
• Published: 11/13/2008
• Est. Priority Date: 05/13/2005
• Status: Active Grant

• Current Assignee: Brother Kogyo Kabushiki Kaisha (Brother Industries Limited)
• Original Assignee: Brother Kogyo Kabushiki Kaisha (Brother Industries Limited)
• Inventors: Yamada, Shiro, Kuramoto, Katsuyuki
• Granted Patent: US 8,040,222 B2
• Time in Patent Office: Days
• US Class Current: 340/10.3
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10079 the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions
• CPC Class Codes: G06K 7/10316 using at least one antenna particularly designed for interrogating the wireless record carriers antennas in general H01Q1/22
• CPC Class Codes: H01Q 1/2208 associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems methods or arrangements for sensing record carriers, e.g. for reading patterns G06K7/00; record carrier for use with machines and with at least a part designed to carry digital markings G06K19/00
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H01Q 25/00 Antennas or antenna systems providing at least two radiating patterns arrangements for changing or varying the orientation or the shape of the directional pattern H01Q3/00
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence
• CPC Class Codes: H01Q 3/30 varying the relative phase between the radiating elements of an array H01Q3/2605, H01Q3/2658, H01Q3/2682, H01Q3/44 take precedence
• CPC Class Codes: H04L 1/1607 Details of the supervisory signal

Abstract

A radio-frequency tag communication system including (a) a radio-frequency tag, (b) 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 the transmitted signal, for thereby effecting radio communication with the radio-frequency tag, and (c) 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 the transmitted signal, for thereby effecting radio communication with the radio-frequency tag communication device, and wherein the radio-frequency tag communication device includes a directivity control portion configured to control a directivity of communication with the radio-frequency tag, on the basis of a result of the radio communication of the radio-frequency tag communication device with the at least one reference tag.

Claims

1. 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,

and 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.

2. The radio-frequency tag communication system according to claim 1, 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.

3. The radio-frequency tag communication system according to claim 1, wherein said at least one reference tag consists of a plurality of reference tags disposed fixedly at respective edges defining said effective range of communication, and said effective-communication-range determining portion determines a range between said plurality of reference tags, as said effective range of communication.

4. The radio-frequency tag communication system according to claim 2, wherein each of said at least one reference tag has a memory which stores boundary condition information indicative of a condition for determining said effective range of communication.

5. The radio-frequency tag communication system according to claim 1, wherein said radio-frequency tag communication device further includes a transmitted-signal-strength determining portion configured to determine a minimum strength of said transmitted signal, which minimum strength permits the radio communication of the radio-frequency tag communication device with said at least one reference tag.

6. The radio-frequency tag communication system according to claim 5, wherein said transmitted-signal-strength determining portion is configured to determine a minimum strength of said transmitted signal, which minimum strength permits the radio communication of the radio-frequency tag communication device with said radio-frequency tag.

7. The radio-frequency tag communication system according to claim 5, wherein said radio-frequency tag communication device further includes a transmission-output changing portion configured to change the strength of said transmitted signal, and said transmitted-signal-strength determining portion commands said transmission-output changing portion to control the strength of the transmitted signal to be transmitted toward said radio-frequency tag and said at least one reference tag.

8. The radio-frequency tag communication system according to claim 1, wherein said radio-frequency tag communication device further includes a memory portion for storing a result of the radio communication with said at least one reference tag.

9. The radio-frequency tag communication system according to claim 8, 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 a determination by said effective-communication-range determining portion, said memory portion being configured to store the result of determination by said effective-communication-range determining portion.

10. The radio-frequency tag communication system according to claim 9, wherein said at least one reference tag consists of a plurality of reference tags, and said memory portion is configured to store a plurality of results of determinations which are made by said effective-communication-range determining portion on the basis of information received from the respective reference tags.

11. The radio-frequency tag communication system according to claim 8, wherein said radio-frequency tag communication device further includes a transmitted-signal-strength determining portion configured to determine a minimum strength of said transmitted signal, which minimum strength permits the radio communication of the radio-frequency tag communication device with said at least one reference tag, and said memory portion is configured to store a result of determination by said transmitted-signal-strength determining portion.

12. The radio-frequency tag communication system according to claim 11, wherein said radio-frequency tag communication device further includes an array antenna device having a plurality of antenna elements.

13. The radio-frequency tag communication system according to claim 12, wherein said array antenna device has a plurality of circular polarization antenna units each of which consists of a pair of mutually intersecting rod-like antenna elements.