Systems and methods for synchronizing a plurality of RFID interrogators in a theatre of operation

• US 8,680,973 B2
• Filed: 06/21/2007
• Issued: 03/25/2014
• 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: Kruest, James Robert, Bann, Gary
• Primary Examiner(s): Zimmerman, Brian
• Assistant Examiner(s): SAMSON, SARA B
• Application Number:
  US11/766,749
• Publication Number:
  US 20080018489A1
• Time in Patent Office: 2,469 Days
• Field of Search: 340/10.3, 340/825, 340/10.1
• US Class Current: 340/12.31
• 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 communications channel;

a synchronization master communicably coupled to the communications channel, the synchronization master configured to send synchronization signals via the communications channel;

a first RFID interrogator communicably coupled to the communications channel, the first RFID interrogator configured to;

(1) select a first time out period based at least in part upon an output from a first random number generator, wherein said output from the first random number generator is independent of any other RFID interrogator in the synchronized environment, (2) register a synchronization failure upon waiting a first predetermined period of time without receiving synchronization signals, and (3) become a new synchronization master if no synchronization signals are detected after registering the synchronization failure and after the first time out period, wherein becoming the new synchronization master comprises sending synchronization signals via the communications channel; and

,

a second RFID interrogator communicably coupled to the communications channel, the second RFID interrogator configured to;

(1) select a second time out period based at least in part upon an output from a second random number generator, wherein said output from the second random number generator is independent of any other RFID interrogator in the synchronized environment, (2) register a synchronization failure upon waiting a second predetermined period of time without receiving synchronization signals, and (3) become the new synchronization master if no synchronization signals are detected after registering the synchronization failure and after the second time out period, wherein becoming the new synchronization master comprises sending synchronization signals via the communications channel,

wherein the first predetermined period of time and the second predetermined period of time are the same.

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 communications channel is a wired connection.

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

listen for synchronization signals over the communications channel while waiting for a frame period to elapse; and

cease becoming the new synchronization master if synchronization signals are detected.

5. The synchronized RFID interrogation system of claim 1, wherein the first and second predetermined period of time comprises a fixed component.

6. The synchronized RFID interrogation system of claim 1,

wherein the first RFID interrogator selects the first time out period after registering the synchronization failure;

and,

wherein the second RFID interrogator selects the second time out period after registering the synchronization failure.

7. The synchronized RFID interrogation system of claim 1, wherein the first RFID interrogator is further configured to (4) detect and then avoid conflicts in becoming the new synchronization master;

and,

wherein the second RFID interrogator is configured to (4) detect and then avoid conflicts in becoming the new synchronization master.