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

• US 9,247,634 B2
• Filed: 03/25/2014
• Issued: 01/26/2016
• 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
• Primary Examiner(s): ZIMMERMAN, BRIAN A
• Assistant Examiner(s): Samson, Sara
• Application Number:
  US14/225,359
• Publication Number:
  US 20150022323A1
• Time in Patent Office: 672 Days
• US Class Current: 1/1
• 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 theater 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 radio frequency identification (RFID) interrogation system, comprising:

a synchronization master configured to transmit a plurality of synchronization signals;

a first RFID interrogator configured to;

detect an a synchronization master outage;

in response to detecting the synchronization master outage, attempt to become the synchronization master after a first wait period comprising a random period of time;

determine whether another RFID interrogator is attempting to become the synchronization master; and

in response to determining that another RFID interrogator is not attempting to become the synchronization master, become the synchronization master;

a second RFID interrogator configured to;

detect the synchronization master outage;

in response to detecting synchronization master outage, attempt to become the synchronization master after a second wait period comprising the same random period of time as the first wait period;

detect that the first RFID interrogator is attempting to become the synchronization master; and

in response to detecting that the first RFID interrogator is attempting to become the synchronization master, remain a slave RFID interrogator; and

a communications channel coupled to the synchronization master, the first RFID interrogator and the second RFID interrogator.

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 an 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 to attempt to become the synchronization master, the first RFID interrogator and the second RFID interrogator are each configured to transmit a synchronization pulse over the communications channel.

6. The synchronized RFID interrogation system of claim 5, wherein to detect the outage at the synchronization master, at least one of the first RFID interrogator and the second RFID interrogator is configured to:

listen for a synchronization pulse from the synchronization master over the communication channel during a predetermined period of time; and

detect the outage at the synchronization master when the synchronization pulse is not received from the synchronization master at an expiration of the predetermined period of time.

7. The system of claim 5, wherein the second RFID interrogator is configured to listen for the synchronization pulse from the first RFID interrogator over the communications channel, and determine that the first RFID interrogator is attempting to become the synchronization master in response to detecting the synchronization pulse from the first RFID interrogator.

8. The system of claim 5, wherein the respective synchronization pulses from the first RFID interrogator and the second RFID interrogator are dispersed.

9. The system of claim 8, wherein the synchronization pulses are dispersed as a result of a skew between a clock of each of the first RFID interrogator and the second RFID interrogator.

10. A method for a first radio frequency identification (RFID) interrogator to become a synchronization master, comprising:

a first RFID interrogator;

detecting a synchronization master outage;

in response to detecting the synchronization master outage, attempting to become the synchronization master after a first wait period comprising a random period of time;

determine whether another RFID interrogator is attempting to become the synchronization master; and

in response to determining that another RFID interrogator is not attempting to become the synchronization master, becoming a synchronization master;

a second RFID interrogator;

detecting the synchronization master outage;

in response to detecting the synchronization master outage, attempting to become the synchronization master after a second wait period comprising the same random period of time as the first wait period;

detecting that the first RFID interrogator is attempting to become the synchronization master;

in response to detecting that the first RFID interrogator is attempting to become the synchronization master, remain a slave RFID interrogator.

11. The method of claim 10, wherein attempting to become the synchronization master includes transmitting a a synchronization pulse over a communications channel after the first wait period, and wherein the second RFID interrogator is configured to listen for the synchronization pulse over the communications channel, and determine that the first RFID interrogator is attempting to become the synchronization master in response to detecting the synchronization pulse.