Optimizing RFID Reader Duty Cycle Or Power To Preserve Battery Life

• US 20090079571A1
• Filed: 09/25/2007
• Published: 03/26/2009
• Est. Priority Date: 09/25/2007
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: CALVARESE, Russell
• Granted Patent: US 7,825,806 B2
• Time in Patent Office: Days
• US Class Current: 340/572.400
• 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 7/10207 parameter settings related to power consumption of the interrogator
• CPC Class Codes: G06K 7/10217 parameter settings controlling the transmission power of the interrogator
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles

Abstract

The duty cycle of a portable battery-powered RFID tag reader is reduced during time periods when it is less likely to produce a “read” in order to preserve battery life. The reader operates with an aggressive duty cycle during periods of a high probability of a tag read and reduces duty cycle during periods of a low probability of a tag read. In this manner a user does not perceive the reader to be sluggish. An alternative embodiment reduces peak operating power during time periods when a tag is less likely to produce a “read” in order to preserve battery life.

Claims

1. A method for operating an RFID reader, comprising:

first operating the RFID reader at a first duty cycle during a first period of time; and

second operating the RFID reader at a second duty cycle less than the first duty cycle during a second period of time characterized by a probability of obtaining a read being less than the probability of obtaining a read during the first period of time.

2. A method according to claim 1, wherein the second operating comprises operating the RFID reader at a decreasing duty cycle until a predetermined minimum duty cycle is reached.

3. An RFID reader, comprising:

first means for operating the RFID reader at a first duty cycle during a first period of time; and

second means for second operating the RFID reader at a second duty cycle less than the first duty cycle during a second period of time characterized by a probability of obtaining a read being less than the probability of obtaining a read during the first period of time.

4. A reader according to claim 3, wherein the second operating means comprises means for operating the RFID reader at a decreasing duty cycle until a predetermined minimum duty cycle is reached.

5. A method for operating an RFID tag reader, comprising:

first operating the RFID tag reader at a first duty cycle;

in the event of a failure to detect RFID tag activity, reducing the duty cycle to a second duty cycle less than the first duty cycle; and

in the event of continued failure to detect RFID tag activity, reducing the duty cycle to a third duty cycle less than the second duty cycle.

6. A method according to claim 5 wherein the first operating occurs following a trigger event.

7. A method according to claim 5 wherein the first operating comprising operating the RFID tag reader in an autonomous mode without any trigger.

8. A method according to claim 5 further comprising:

operating the RFID tag reader at an increased duty cycle in response to a detection of some RFID tag activity.

9. A method according to claim 5 further comprising:

stepping down the duty cycle at predetermined points in time related to an occurrence of an event.

10. A method according to claim 9 wherein the event is a detection of RFID tag activity.

11. A method according to claim 9 wherein the event is a successful RFID tag read.

12. An RFID tag reader, comprising:

first means for operating the RFID tag reader at a first duty cycle;

second means for, in the event of a failure to detect RFID tag activity, reducing the duty cycle to a second duty cycle less than the first duty cycle;

third means for, in the event of continued failure to detect RFID tag activity, reducing the duty cycle to a third duty cycle less than the second duty cycle;

13. An RFID tag reader according to claim 12 wherein the first means operates in response to a trigger.

14. An RFID tag reader according to claim 12 further comprising means for operating the RFID tag reader in an autonomous mode.

15. An RFID tag reader according to claim 12 further comprising:

means for operating the RFID tag reader at an increased duty cycle in response to a detection of some RFID tag activity.

16. An RFID tag reader according to claim 12 further comprising:

means for stepping down the duty cycle at predetermined points in time related to an event.

17. An RFID tag reader according to claim 12 wherein the event is a detection of RFID tag activity.

18. An RFID tag reader according to claim 12 wherein the event is a successful RFID tag read.

19. A method for operating an RFID reader, comprising:

first operating the RFID reader at a first peak power during a first period of time; and

second operating the RFID reader at a second peak power that is less than the first peak power during a second period of time characterized by a probability of obtaining a read being less than the probability of obtaining a read during the first period of time.

20. A method according to claim 19, wherein the second operating comprises operating the RFID reader at a decreasing power until a predetermined minimum power is reached.

21. An RFID reader, comprising:

first means for operating the RFID reader at a first peak power during a first period of time; and

second means for second operating the RFID reader at a second peak power less than the first peak power during a second period of time characterized by a probability of obtaining a read being less than the probability of obtaining a read during the first period of time.

22. A reader according to claim 21, wherein the second operating means comprises means for operating the RFID reader at a decreasing power until a predetermined minimum power is reached.