Systems and methods for stirring electromagnetic fields and interrogating stationary RFID tags

• US 10,133,894 B2
• Filed: 12/30/2010
• Issued: 11/20/2018
• Est. Priority Date: 06/21/2006
• Status: Active Grant

• Current Assignee: Smartrac Technology Fletcher, Inc. (Avery Dennison Corporation), Novatel Wireless, Inc. (Inseego Corp.)
• Original Assignee: Smartrac Technology Fletcher, Inc. (Avery Dennison Corporation)
• Inventors: Kruest, James Robert, Bann, Gary
• Primary Examiner(s): Lim, Steven
• Assistant Examiner(s): Adnan, Muhammad
• Application Number:
  US12/982,398
• Publication Number:
  US 20110163849A1
• Time in Patent Office: 2,882 Days
• Field of Search: 3405721-5729
• 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, RFID interrogators and RFID tags remain stationary during interrogation. Regions of low energy due to interference from either additional antenna or reflections from RFID tags and objects can impede or prohibit the reading of RFID tags residing in such regions. Stirring of the generated electromagnetic field is a method of moving around the regions of low energy, where tags can not be read, during the interrogation process. Mechanical stirring is accomplished by introducing a conductor into the electromagnetic field and moving it about in the field. Solid state stirring is accomplished by introducing a variable conductor into the field and varying the conductivity of the variable conductor. Mathematical stirring is accomplished by use of a plurality of antenna and controlling the phase difference between the antenna in a configuration known as phased antenna arrays.

Claims

1. A method for interrogating one or more stationary RFID tags in a static interrogation environment, the method comprising:

providing a stationary antenna for transmitting and receiving RF signals to and from the one or more stationary RFID tags;

generating, by the stationary antenna, an electromagnetic interrogation field of a predetermined frequency in the interrogation environment; and

moving a first conductor positioned inside the electromagnetic interrogation field while both the stationary antenna and the one or more stationary RFID tags are stationary, wherein moving the first conductor varies a position of at least one low energy region present within the electromagnetic interrogation field.

2. The method of claim 1, wherein the first conductor is moved continuously with respect to the one or more stationary RFID tags in the interrogation environment.

3. The method of claim 1, wherein the first conductor is rotated with respect to the one or more stationary RFID tags in the interrogation environment.

4. The method of claim 1, wherein the conductor comprises a piece of metal having a length greater than a wavelength of the electromagnetic field.

5. The method of claim 1, wherein the interrogation environment comprises an enclosed structure.

6. The method of claim 1, wherein the stationary antenna and the first conductor are coupled to an interrogator, and wherein the interrogator is coupled to a network that is further coupled to a central server.

7. The method of claim 1, the first conductor is oscillated with respect to the one or more stationary RFID tags in the interrogation environment.

8. The method of claim 1, wherein the position of the at least one low energy region present within the electromagnetic interrogation field is further varied by moving a second conductor separate from the stationary antenna.

9. The method of claim 8, wherein a motion of the first conductor is independent of a motion of the second conductor.

10. The method of claim 8, wherein a motion of at least one of the first conductor and the second conductor is arbitrary.

11. The method of claim 8, wherein one of the first conductor and the second conductor is rotated and the other of the first conductor and the second conductor is oscillated with respect to the one or more stationary RFID tags in the interrogation environment.

12. The method of claim 5, wherein the first conductor is external to the enclosed structure.

13. The method of claim 1, wherein the first conductor is in motion only when the one or more stationary RFID tags are being interrogated.

14. The method of claim 1, wherein the first conductor is in motion entire time when an RFID interrogation system including the stationary antenna, the one or more stationary RFID tags, and a RFID interrogator is active.