RFID tag reading system and method

• US 7,187,288 B2
• Filed: 10/06/2004
• Issued: 03/06/2007
• Est. Priority Date: 03/18/2002
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Paratek Microwave Incorporated (Blackberry Limited)
• Inventors: Mendolia, Greg, Kvarnstrand, John, du Toit, Nicolaas, Foo, Bing, du Toit, Cornelius
• Primary Examiner(s): Wu; Daniel
• Assistant Examiner(s): Mehmood; Jennifer
• Application Number:
  US10/959,633
• Publication Number:
  US 20050110641A1
• Time in Patent Office: 881 Days
• Field of Search: 343/911.R, 343866-872, 343/726, 343/748, 343/855, 340/572.1, 340/572.9, 340/505, 340/506, 340/539.13, 700213-244, 705/22, 235375-385
• US Class Current: 340/572.1
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 5/04 Position of source determined by a plurality of spaced direction-finders
• CPC Class Codes: G01S 5/12 by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial
• CPC Class Codes: G06K 7/10079 the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions
• CPC Class Codes: G06K 7/10336 the antenna being of the near field type, inductive coil
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles
• CPC Class Codes: H01Q 1/42 Housings not intimately mechanically associated with radiating elements, e.g. radome
• CPC Class Codes: H01Q 21/205 providing an omnidirectional coverage turnstile aerials H01Q21/26
• CPC Class Codes: H01Q 25/00 Antennas or antenna systems providing at least two radiating patterns arrangements for changing or varying the orientation or the shape of the directional pattern H01Q3/00
• CPC Class Codes: H01Q 3/36 with variable phase-shifters
• CPC Class Codes: H01Q 9/0407 Substantially flat resonant element parallel to ground plane, e.g. patch antenna dipole H01Q9/285; monopole H01Q9/40

Abstract

An embodiment of the present invention provides an RFID tag reading system, comprising an antenna system associated with a portal through which said RFID tag may pass, said antenna system comprising: a plurality of non-uniformly spaced antenna elements arranged substantially linearly; a power divider for dividing transmit power thereby coupling signals to said plurality of antenna elements; and a beamforming network capable of phase shifting the signals between the power divider and the plurality of antenna elements such that radiated signals from each antenna element add coherently such that the radiated electromagnetic energy is focused at a focal point in the near field region or in the Fresnel region of said antenna system.

Claims

1. a RFID tag reading system, comprising:

an antenna system associated with a portal through which a RFID tag may pass, said antenna system comprising;

a plurality of non-uniformly spaced antenna elements arranged substantially linearly;

a power divider for dividing transmit power thereby coupling signals to said plurality of antenna elements; and

a beamforming network adapted to phase shift the signals between the power divider and the plurality of antenna elements such that radiated signals from each antenna element add coherently such that the radiated electromagnetic energy is focused at a focal point in the near field region or in the Fresnel region of said antenna system.

2. The RFID tag reading system of claim 1, further comprising at least one additional receive antenna element adapted to receive signals backscattered from at least one RFID tag located in the near field of said antenna system.

3. The RFID tag reading system of claim 1, wherein said portal is a doorway and said antenna system is installed at the sides or the top said doorway.

4. The RFID tag reading system of claim 1, wherein said antenna elements are arranged in a linear array along an axis, and where the axis is vertically oriented thereby allowing the near field beam to be broad in the horizontal direction which in turn allows greater dwell times for said RFID tags to be interrogated as it passes through said portal.

5. a RFID tag reading system, comprising:

an antenna system associated with a conveyor on which an RFID tag may pass, said antenna system comprising;

a plurality of antenna elements arranged in essentially an arc where the main beam of each element is directed toward the interior side of the arc;

a power divider for dividing transmit power thereby coupling signals to said plurality of antenna elements; and

a beamforming network adapted to phase shifte the signals between the power divider and the plurality of antenna elements such that radiated signals from each antenna element add coherently such that the radiated electromagnetic energy is focused at a focal point in the near field region or in the Fresnel region of said antenna system.

6. The RFID tag reading system of claim 5, further comprising at least one additional receive antenna element adapted to receive signals backscattered from at least one RFID tag located in the near field of said focused array.

7. The RFID tag reading system of claim 6, wherein said an antenna system is adapted to produce M fixed beams where each of N radiating elements is fed by an M-way power combiner, and M separate beamforming networks connect M RF input ports to each of said N M-way power combiners.

8. a RFID tag reading system, comprising:

at least one RFID tag reader;

at least one RFID tag with one or more electrically reflective surfaces placed around a volume where said at least one RFID tag is to be interrogate;

a plurality of antenna elements arranged in essentially an arc where the main beam of each element is directed toward the interior side of the arc

a power divider for dividing transmit power thereby coupling signals to said plurality of antenna elements; and

a beamforming network adapted to phase shift the signals between the power divider and the plurality of antenna elements such that radiated signals from each antenna element add coherently such that the radiated electromagnetic energy is focused at a focal point in the near field region or in the Fresnel region of said antenna system.

9. The RFID tag reading system of claim 8, further comprising at least one additional receive antenna element adapted to receive signals backscattered from at least one RFID tag located in the near field region or Fresnel region of said antenna system.

10. The RFID tag reading system of claim 8, wherein said antenna system is adapted to produce M fixed beams where each of N radiating elements is fed by an M-way power combiner, and M separate beamforming networks connect M RF input ports to each of said N M-way power combiners.

11. The RFID tag reading system of claim 8, further comprising an antenna system, said antenna system comprising:

a plurality of non-uniformly spaced antenna elements arranged substantially linearly;

a power divider for dividing transmit power thereby coupling signals to said plurality of antenna elements; and

a beamforming network adapted to phase shift the signals between the power divider and the plurality of antenna elements such that radiated signals from each antenna element add coherently such that the radiated electromagnetic energy is focused at a focal point in the near field region or in the Fresnel region of said antenna system.

12. The RFID tag reading system of claim 11, further comprising at least one additional receive antenna element adapted to receiveing signals backscattered from at least one RFID tag located in the near field of said antenna system.

13. The RFID tag reading system of claim 8 wherein said reflective surface comprises a substantially flat surface covered by conductive foil.

14. The RFID tag reading system of claim 8, wherein said reflective surface comprises a substantially flat surface covered by conductive paint.

15. The RFID tag reading system of claim 8, wherein said reflective surface comprises a conductive polymer material.

16. The RFID tag reading system of claim 8, further comprising a beam scanning antenna system for interrogation of tags.

17. A method of reading a RFID tag, comprising:

passing said RFID tag through a portal associated with an antenna system, said antenna system comprising;

a plurality of non-uniformly spaced antenna elements arranged substantially linearly;

a power divider for dividing transmit power thereby coupling signals to said plurality of antenna elements; and

a phase shifter adapted to phase shift the signals between the power divider and the plurality of antenna elements such that radiated signals from each antenna element add coherently such that the radiated electromagnetic energy is focused at a focal point in the near field region or in the Fresnel region of said antenna system.

18. The method of claim 17, further comprising receiving signals backscattered from said at least one RFID tag located in the near field of said antenna system by at least one additional receive antenna element.

19. A method of reading a RFID tag, comprising:

passing said RFID tag through a portal associated with an antenna system, said antenna system comprising;

a plurality of antenna elements arranged in essentially an arc where the main beam of each element is directed toward the interior side of the arc;

a power divider for dividing transmit power thereby coupling signals to said plurality of antenna elements; and

a beamforming network adapted to phase shift the signals between the power divider and the plurality of antenna elements such that radiated signals from each antenna element add coherently such that the radiated electromagnetic energy is focused at a focal point in the near field region or in the Fresnel region of said antenna system.

20. The method of claim 19, further comprising receiving signals backscattered from said at least one RFID tag located in the near field of said antenna system by at least one additional receive antenna element.

21. A method of reading a RFID tag, comprising providing at least one RFID tag reader;

placing one or more electrically reflective surfaces around a volume where at least one RFID tag is to be interrogated; and

using an antenna system that comprises;

a plurality of antenna elements arranged in essentially an arc where the main beam of each element is directed toward the interior side of the arc;

a power divider for dividing transmit power thereby coupling signals to said plurality of antenna elements; and

a phase shifter adapted to shift the signals between the power divider and the plurality of antenna elements such that radiated signals from each antenna element add coherently such that the radiated electromagnetic energy is focused at a focal point in the near field region or in the Fresnel region of said antenna system.