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

• US 20160162776A1
• Filed: 01/26/2016
• Published: 06/09/2016
• 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
• Granted Patent: US 9,626,619 B2
• Time in Patent Office: Days
• 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 radio frequency identification (RFID) interrogation system, comprising:

multiple RFID interrogators, wherein each of the multiple RFID interrogators is configured to transmit a plurality of synchronization pulses to surrounding RFID tags, and wherein the multiple RFID interrogators includes a first RFID interrogator, which is configured to;

transmit a synchronization pulse to nearby RFID tags;

while listening for RFID tag transmissions in response to the synchronization pulse, attempt to detect any interference from another RFID interrogator among the multiple RFID interrogators; and

if an interference is detected from a second RFID interrogator among the multiple RFID interrogators, determine if data is expected from a nearby RFID tag, and

if no data is expected, synchronize a transmission of the next synchronization pulse with the next synchronization pulse of the second RFID interrogator;

otherwise, wait for the expected data from the nearby RFID tag.

2. The RFID interrogation system of claim 1, wherein while detecting interference from another RFID interrogator, the first RFID interrogator is further configured to:

wait for the second half of the synchronization pulse;

if a pulse is detected in the second half of the synchronization pulse, determine if another pulse was detected in the second half of a synchronization pulse transmitted by the first RFID interrogator immediately before the synchronization pulse; and

if so, determine that an interference with the second RFID interrogator is detected.

3. The RFID interrogation system of claim 1, wherein if no interference is detected, the first RFID interrogator is configured to process any RFID tag transmission received during the second half of the synchronization pulse.

4. The RFID interrogation system of claim 1, wherein while synchronizing the transmission of the next synchronization pulse, the first RFID interrogator is configured to delay the transmission of the next synchronization pulse so that the start of the next synchronization pulse of the first RFID interrogator coincides with the start of the next synchronization pulse of the second RFID interrogator.

5. The RFID interrogation system of claim 1, wherein while waiting for the expected data from the nearby RFID tag, the first RFID interrogator is configured to wait a random number of synchronization pulse periods.

6. The RFID interrogation system of claim 1, wherein the first and the second RFID interrogators are wireless coupled to each other.

7. The RFID interrogation system of claim 1, wherein the second RFID interrogator moves into a wireless detection range of the first RFID interrogator.

8. The RFID interrogation system of claim 1, wherein at least one of the first RFID interrogator and the second RFID interrogator is a mobile RFID interrogator.

9. The RFID interrogation system of claim 1, wherein the first RFID interrogator is a mobile RFID interrogator mounted on a forklift for warehouse tracking.

10. The RFID interrogation system of claim 1, wherein the first RFID interrogator is configured in form of a hand-held scanner for shipment tracking.

11. A method for operating a first radio frequency identification (RFID) interrogator among multiple RFID interrogators while avoiding interferences with other RFID interrogators among the multiple RFID interrogators, comprising:

transmitting a synchronization pulse by the first RFID interrogator to surrounding RFID tags;

while listening for RFID tag transmissions in response to the synchronization pulse, attempting to detect any interference from another RFID interrogator among the multiple RFID interrogators;

if an interference is detected from a second RFID interrogator among the multiple RFID interrogators, determining if data is expected from a nearby RFID tag, and

if no data is expected, synchronizing a transmission of the next synchronization pulse of the first RFID interrogator with the next synchronization pulse of the second RFID interrogator;

otherwise, waiting for the expected data from the nearby RFID tag.

12. The method of claim 11, wherein detecting interference from another RFID interrogator includes:

waiting for the second half of the synchronization pulse;

if a pulse is detected in the second half of the synchronization pulse, determining if another pulse was detected in the second half of a synchronization pulse transmitted by the first RFID interrogator immediately before the synchronization pulse; and

if so, determining that an interference with the second RFID interrogator is detected.

13. The method of claim 11, wherein if no interference is detected, the method further comprises processing any RFID tag transmission received during the second half of the synchronization pulse.

14. The method of claim 11, wherein synchronizing the transmission of the next synchronization pulse of the first RFID interrogator with the next synchronization pulse of the second RFID interrogator includes delaying the transmission of the next synchronization pulse of the first RFID interrogator so that the start of the next synchronization pulse of the first RFID interrogator coincides with the start of the next synchronization pulse of the second RFID interrogator.

15. The method of claim 11, wherein waiting for the expected data from the nearby RFID tag includes waiting for a random number of synchronization pulse periods.

16. The method of claim 11, wherein the first and the second RFID interrogators are wireless coupled to each other.

17. The method of claim 11, wherein the second RFID interrogator moves into a wireless detection range of the first RFID interrogator.

18. The method of claim 11, wherein at least one of the first RFID interrogator and the second RFID interrogator is a mobile RFID interrogator.

19. The method of claim 11, wherein the first RFID interrogator is a mobile RFID interrogator mounted on a forklift for warehouse tracking.

20. The method of claim 11, wherein the first RFID interrogator is used as a hand-held scanner for shipment tracking.