SYSTEMS AND METHODS FOR SYNCHRONIZING A PLURALITY OF RFID INTERROGATORS IN A THEATRE OF OPERATION

• US 20080018489A1
• Filed: 06/21/2007
• Published: 01/24/2008
• Est. Priority Date: 06/21/2006
• Status: Active Grant

• Current Assignee: Smartrac Technology Fletcher, Inc. (Avery Dennison Corporation)
• Original Assignee: Neology Incorporated (OEP Technologie BV)
• Inventors: Bann, Gary, Kruest, James
• Granted Patent: US 8,680,973 B2
• Time in Patent Office: Days
• US Class Current: 340/825.2
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 19/07796 arrangements on the record carrier to allow stacking of a plurality of similar record carriers, e.g. to avoid interference between the non-contact communication of the plurality of record carriers
• CPC Class Codes: G06K 19/07798 part of the antenna or the integrated circuit being adapted for rupturing or breaking, e.g. record carriers functioning as sealing devices for detecting not-authenticated opening of containers electronic seals G09F3/03
• 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 7/10029 the collision being resolved in the time domain, e.g. using binary tree search or RFID responses allocated to a random time slot
• CPC Class Codes: G06K 7/10039 interrogator driven, i.e. synchronous
• CPC Class Codes: G06K 7/10475 arrangements to facilitate interaction with further interrogation devices, e.g. such that at least two interrogation devices may function and cooperate in a network of such devices
• CPC Class Codes: G06Q 10/08 Logistics, e.g. warehousing, loading or distribution; Inventory or stock management
• CPC Class Codes: H04J 3/0641 Change of the master or reference, e.g. take-over or failure of the master
• CPC Class Codes: H05K 1/02 Details
• CPC Class Codes: H05K 1/0266 Marks, test patterns or identification means
• CPC Class Codes: H05K 1/0268 for electrical inspection or testing
• CPC Class Codes: H05K 1/142 Arrangements of planar printed circuit boards in the same plane, e.g. auxiliary printed circuit insert mounted in a main printed circuit
• CPC Class Codes: H05K 2201/0909 Preformed cutting or breaking line
• CPC Class Codes: H05K 2201/09127 PCB or component having an integral separable or breakable part
• CPC Class Codes: H05K 3/30 Assembling printed circuits with electric components, e.g. with resistor

Abstract

RFID tags are used for many purpose including tracking. RFID interrogators are used to retrieve information from tags. In many applications, a plurality of RFID interrogators are required. Synchronization between interrogators in the same theatre of operation is critical to ensure that their broadcasts do not interfere with each other. In fixed RFID interrogator applications, RFID interrogators can be wired together allowing a channel to synchronize the transmissions of the RFID interrogators. Methods described herein can ensure that synchronization is maintained in the event of the failure of a synchronizing master. Furthermore, additional methods for synchronizing RFID interrogators in wireless applications are described allowing synchronization in the absence of wired connections between interrogators.

Claims

1. A synchronized RFID interrogation system, comprising:

a first RFID interrogator configured to promote itself to a synchronization master when no synchronization master is detected;

a second RFID interrogator;

a communications channel coupled to the first RFID interrogator and the second RFID interrogator; and

a synchronization master coupled to the communications channel, configured to send a synchronization signal at the start of each interrogation frame.

2. The synchronized RFID interrogation system of claim 1, wherein the synchronization master is a pulse generator.

3. The synchronized RFID interrogation system of claim 1, wherein the synchronization master is part of the second RFID interrogator:

4. The synchronized RFID interrogation system of claim 1, wherein the communications channel is a wired connection.

5. The synchronized RFID interrogation system of claim 1, wherein the first RFID interrogator is configured to:

wait a predetermined period of time for a synchronization pulse; and

transmit a synchronization pulse over the communications channel and become a synchronization master if no pulse is detected.

6. The synchronized RFID interrogator system of claim 5, wherein the first RFID interrogator is further configured to:

listen for a synchronization pulse over the communications channel while waiting for a frame period to elapsed; and

cease becoming a synchronization master if a synchronization pulse is detected.

7. The synchronized RFID interrogation system of claim 1, wherein the predetermined period of time comprises a random component.

8. The synchronized RFID interrogation system of claim 1, wherein the predetermined period of time comprises a fixed component.

9. A method for an RFID interrogator to become a synchronization master comprising, the RFID interrogator:

waiting a predetermined period of time;

detecting synchronization pulses over a communications channel; and

becoming a synchronization master if no pulse is detected before the predetermined period of time has expired.

10. The method of claim 9, wherein the predetermined period of time comprises a random component.

11. The method of claim 9, wherein the predetermined period of time comprises a fixed component.

12. A method for an RFID interrogator functioning as a synchronization master to terminate being a synchronization master comprising:

waiting for a frame period since the interrogator last transmitted a synchronization pulse over a communications channel;

detecting a synchronization pulse over the communications channel; and

stopping future transmissions of synchronization pulses if a synchronization pulse is detected before the frame period expires.

13. A method of synchronization operation of a self-promotion enabled RFID interrogator comprising:

determining whether the RFID interrogator currently has a master status;

waiting for the next start of frame if the RFID interrogator has master status;

detecting a synchronization pulse over a communications channel if the RFID interrogator has master status;

transmitting a frame synchronization pulse, if the RFID interrogator has master status and no pulse is detected;

changing the RFID interrogator to a slave status, if the RFID interrogator has master status and a pulse is detected;

waiting for a predetermined period of time if the RFID interrogator has slave status;

detecting a synchronization pulse over a communications channel if the RFID interrogator has slave status; and

changing the RFID interrogator to master status if the RFID interrogator has slave status and the predetermined period of time has expired.

14. The method of claim 13, wherein the predetermined period of time comprises a random component.

15. The method of claim 13, wherein the predetermined period of time comprises a predetermined fixed component.

16. The method of claim 13, wherein waiting for the predetermined period of time comprises:

waiting a predetermined fixed period of time;

selecting a random wait period within a predetermine range of values; and

waiting the random wait period.

17. An RFID interrogator configured for self-promotion in a synchronized environment comprising:

a master state configured to track whether the interrogator is a synchronization master having a master status and a slave status;

a detector configured to detect synchronization pulses over a communication channel and configured to reset the master state back to slave status if the master state has the master status;

a timer configured to wait a predetermined period of time, configured to be reset if the detector detects a synchronization pulse and configured to set the master state to master status if the timer expires;

a transmitter configured to transmit synchronization pulses over the communications channel, if the timer expires before being reset or if a frame timer expires and the master state has the master status; and

a frame timer configured to wait for a frame period since the transmitter last transmitted synchronization pulses.

18. The RFID interrogator of claim 17, further comprising a random number generator used to select a random component of the predetermined period of time.

19. The RFID interrogator of claim 17, where the predetermined period of time comprises a predetermined fixed component.