RFID interrogator and data communication method thereof

• US 20070046436A1
• Filed: 05/01/2006
• Published: 03/01/2007
• Est. Priority Date: 08/30/2005
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Tanaka, Yoshinori
• Granted Patent: US 7,764,164 B2
• Time in Patent Office: Days
• US Class Current: 340/10.200
• 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 7/10039 interrogator driven, i.e. synchronous
• CPC Class Codes: G06K 7/10069 the collision being resolved in the frequency domain, e.g. by hopping from one frequency to the other frequency hopping or spread spectrum techniques H04B7/00
• CPC Class Codes: G06K 7/10326 the antenna being of the very-near field type, e.g. capacitive
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles
• CPC Class Codes: G06K 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas

Abstract

An interrogator autonomously reduces interference of receiving radio waves in a wireless tag. The interrogator transmitting and receiving a signal to and from a wireless tag, comprises a carrier sense unit detecting an idle channel in a plurality of channels used for communications with the wireless tags, a transmitting unit transmitting the signal to the wireless tag by use of the detected idle channel, an abnormality detecting unit detecting communication abnormality in the communications with the wireless tag, and a control unit controlling so as to interrupt, when detecting the communication abnormality, the transmission to the wireless tag, re-detect an idle channel after an elapse of a predetermined transmission halt period, and resume the signal transmission to the wireless tag by using the re-detected idle channel.

Claims

1. An interrogator transmitting and receiving a signal to and from a wireless tag, comprising:

a carrier sense unit detecting an idle channel in a plurality of channels used for communications with the wireless tag;

a transmitting unit transmitting the signal to the wireless tag by use of the detected idle channel;

an abnormality detecting unit detecting communication abnormality in the communications with the wireless tag; and

a control unit controlling so as to interrupt, when detecting the communication abnormality, the transmission to the wireless tag, re-detect an idle channel after an elapse of a predetermined transmission halt period, and resume the signal transmission to the wireless tag by using the re-detected idle channel.

2. An interrogator according to claim 1, wherein the abnormality detecting unit detects the communication abnormality within a predetermined timeout observation period from a point of time when starting the transmission of the signal to the wireless tag.

3. An interrogator according to claim 1, wherein the control unit further includes a changing unit changing the timeout period according to a priority level of the transmission to the wireless tag, and

the abnormality detecting unit detects the communication abnormality if the abnormality in the communications with the wireless tag continues for the timeout period.

4. An interrogator according to claim 3, wherein the changing unit determines the priority level of the transmission according to the number of interrupting the transmission due to the detection of the communication abnormality.

5. An interrogator according to claim 4, wherein the changing unit makes the priority level of the transmission higher as the number of interrupting the transmission in the case of detecting the communication abnormality becomes larger, and makes the timeout period longer as the priority level of the transmission becomes higher.

6. An interrogator according to claim 1, wherein the control unit, if a period of a consecutive transmission to the wireless tag exceeds a predetermined maximum consecutive transmission period, controls so as to stop the transmission to the wireless tag, and makes the transmission halt period the equivalent length of time as the maximum consecutive transmission period.

7. A data communication method in an interrogator transmitting and receiving a signal to and from a wireless tag, comprising:

a step of detecting an idle channel in a plurality of channels used for communications with the wireless tag;

a step of transmitting the signal to the wireless tag by use of the detected idle channel;

an abnormality detecting step of detecting communication abnormality in the communications with the wireless tag; and

a control step of controlling so as to interrupt, when detecting the communication abnormality, the transmission to the wireless tag, re-detect an idle channel after an elapse of a predetermined transmission halt period, and resume the signal transmission to the wireless tag by employing the re-detected idle channel.

8. A data communication method according to claim 7, wherein the abnormality detecting step detects the communication abnormality within a predetermined timeout observation period from a point of time when starting the transmission of the signal to the wireless tag.

9. A data communication method according to claim 7, wherein the control step further includes a changing step of changing the timeout period according to a priority level of the transmission to the wireless tag,

wherein the abnormality detecting step detects the communication abnormality if the abnormality in the communications with the wireless tag continues for the timeout period.

10. A data communication method according to claim 9, wherein the changing step determines the priority level of the transmission according to the number of interrupting the transmission in the case of detecting the communication abnormality.

11. A data communication method according to claim 10, wherein the changing step makes the priority level of the transmission higher as the number of interrupting the transmission in the case of detecting the communication abnormality becomes larger, and makes the timeout period longer as the priority level of the transmission becomes higher.

12. A data communication method according to claim 7, wherein the control step, if a period of a consecutive transmission to the wireless tag exceeds a predetermined maximum consecutive transmission period, controls so as to stop the transmission to the wireless tag, and makes the transmission halt period the equivalent length of time as the maximum consecutive transmission period.