RFID tag test antenna with two ports that excite perpendicular modes

• US 7,538,679 B2
• Filed: 11/07/2006
• Issued: 05/26/2009
• Est. Priority Date: 11/07/2006
• Status: Expired due to Fees

• Current Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Shanks, Wayne E.
• Primary Examiner(s): Pham; Toan N
• Assistant Examiner(s): Mehmood; Jennifer
• Application Number:
  US11/593,587
• Publication Number:
  US 20080106378A1
• Time in Patent Office: 931 Days
• Field of Search: 340 101- 106, 3405721-5729, 324/513, 324519-527, 324/529, 324/530, 343/703, 343/720, 343/760, 343/824
• US Class Current: 340/572.1
• CPC Class Codes: G01R 31/2822 of microwave or radiofrequency circuits of attenuation, gain, e.g. using network analyzers G01R27/28
• CPC Class Codes: H04B 5/77 for interrogation

Abstract

Methods, systems, and apparatuses for RFID devices, such as tag test methods, are described. A tag of a strip of tags is positioned adjacent to an opening in an electrically conductive sheet, the tag having first and second orthogonally polarized antennas. A first RF test signal is transmitted through the opening to test the first antenna of the tag. The tag is positioned such that the first RF test signal has a polarization substantially the same as the first antenna and substantially orthogonal to a polarization of the second antenna. A second RF test signal is transmitted through the opening to test the second antenna of the tag. The tag is positioned such that the second RF test signal has a polarization substantially the same as the second antenna and substantially orthogonal to the polarization of the first antenna. If proper responses to both of the first and second RF test signals are received, the tag has passed the test. This test may be repeated for further tags in the strip of tags as desired.

Claims

1. A method of testing a strip of radio frequency identification (RFID) tags comprising:

(1) positioning a tag of a strip of tags adjacent to an opening in an electrically conductive sheet, wherein the tag has orthogonally polarized first and second antennas;

(2) transmitting a first RF test signal through the opening, wherein the tag is positioned such that the first RF test signal has a polarization that is substantially the same as a polarization of the first antenna and is substantially orthogonal to a polarization of the second antenna;

(3) determining whether a response to the first RF test signal is received using a central logic structure;

(4) transmitting a second RF test signal through the opening, wherein each tag positioned adjacent to the opening is positioned such that the second RF test signal has a polarization that is substantially the same as the polarization of the second antenna and is substantially orthogonal to the polarization of the first antenna; and

(5) determining whether a response to the second RF test signal is received using the central logic structure.

2. The method of claim 1, further comprising:

(6) positioning a second tag of the strip of RFID tags positioned adjacent the opening; and

(7) repeating steps (2)-(

     5).

3. The method of claim 1, further comprising:

(6) exposing a second tag of the strip not positioned adjacent to the opening to electromagnetic radiation, whereby the second tag is disabled from responding to the first RF test signal and the second RF test signal.

4. The method of claim 3, where step (6) further comprises:

using a Halogen bulb

to provide the electromagnetic radiation.

5. The method of claim 3, where step (6) further comprises:

exposing a sensor of the second tag of the strip of tags to the electromagnetic radiation, whereby the second tag is disabled from responding to the first RF test signal and the second RF test signal.

6. The method of claim 3, further comprising:

(7) shielding the first tag from the electromagnetic radiation by using a shielding element.

7. The method of claim 1, wherein the first antenna and the second antenna of each tag of the tags positioned adjacent to the opening are dipole antennas positioned such that the polarization of the first antenna is orthogonal to the polarization of the second antenna.

8. The method of claim 1, wherein step (3) further comprises:

marking the tag if it is determined that a response to the first RF test signal is not received.

9. The method of claim 1, wherein step (5) further comprises:

marking the tag if it is determined that a response to the second RF test signal is not received.

10. A radio frequency identification (RFID) tag testing apparatus comprising:

a conductive sheet having an opening through a center portion, wherein the conductive sheet is configured to accommodate a strip of tags, wherein the opening is configured to accommodate a tag of the strip; and

an antenna positioned adjacent to the opening, wherein the antenna transmits at least a first electromagnetic wave toward the opening and a second electromagnetic wave toward the opening, wherein a polarization of the first electromagnetic wave is orthogonal to a polarization of the second electromagnetic wave.

11. The testing apparatus of claim 10, wherein the conductive sheet shields tags in the strip not positioned in the opening from electromagnetic waves transmitted from the antenna.

12. The testing apparatus of claim 10, wherein the antenna comprises:

a substrate having opposing first and second surfaces, wherein the first surface of the substrate includes a patch of a conductive material;

a first port coupled to the second surface at a first location, wherein an input signal received at the first port is transmitted as the first electromagnetic wave from the antenna; and

a second port coupled to the second surface at a second location, wherein an input signal received at the second port is transmitted as the second electromagnetic wave from the antenna.

13. The testing apparatus of claim 12, wherein the first port and the second port are substantially isolated.

14. The testing apparatus of claim 12, wherein a coupling factor between the first port and the second port is less than −

20 dB.

15. The testing apparatus of claim 12, wherein the patch is rectangular shaped, wherein the patch is located in a center of the first surface of the substrate.

16. The testing apparatus of claim 12, wherein the rectangular patch has at least one edge that has a length equal to half of a wavelength of the input signal.

17. The testing apparatus of claim 12, wherein at least one terminating load is coupled to an edge of the patch.

18. The testing apparatus of claim 12, wherein the conductive material is copper or aluminum.

19. The testing apparatus of claim 10, wherein the antenna is configured to transmit the first and second electromagnetic waves in a near-field range of the antenna.

20. The testing apparatus of claim 19, wherein the antenna is configured to transmit the first and second electromagnetic waves such that tags in a far-field range of the antenna do not respond.

21. The testing apparatus of claim 10, wherein the antenna is configured to transmit the first electromagnetic wave to cause a first antenna of a tag positioned in the opening to receive the first electromagnetic wave and a second antenna of the tag positioned in the opening to not substantially receive the first electromagnetic wave.

22. The testing apparatus of claim 12, wherein the substrate comprises FR4.

23. The testing apparatus of claim 12, wherein the first and second ports are positioned symmetrically on the second surface of the substrate.

24. The testing apparatus of claim 12, wherein the second surface of the substrate is substantially covered in the conductive material, wherein the first port and the second port each have a first portion electrically coupled to the second surface of the substrate and a second portion electrically coupled to the patch on the first surface of the substrate.

25. The testing apparatus of claim 24, wherein the first portions of the first and second ports are grounded.

26. The testing apparatus of claim 10, wherein only a first antenna of a tag positioned adjacent to the opening is excited by the first electromagnetic wave transmitted by the antenna, and only a second antenna of the tag positioned adjacent to the opening is excited by the second electromagnetic wave transmitted by the antenna.

27. The testing apparatus of claim 10, further comprising an electromagnetic radiation source configured such that a second tag of the strip of tags not positioned adjacent to the opening is exposed to radiation radiated by the source, whereby the second tag of the strip of tags is disabled from responding to the electromagnetic waves transmitted by the antenna.

28. The testing apparatus of claim 27, wherein the source is a halogen bulb.

29. The testing apparatus of claim 27, wherein the source is configured such that radiation radiated by the source is incident on a radiation sensor of the second tag of the strip of tags, whereby the second tag of the strip of tags is disabled from responding to electromagnetic waves transmitted by the antenna.

30. The testing apparatus of claim 27, further comprising a shielding element, wherein the shielding element shields the tag of the strip of tags adjacent to the opening from radiation radiated from the source.

31. A system for testing a strip of radio frequency identification (RFID) tags comprising:

means for positioning a tag of a strip of tags adjacent to an opening in an electrically conductive sheet, wherein the tag has orthogonally polarized first and second antennas;

means for transmitting a first RF test signal through the opening, wherein the tag is positioned such that the first RF test signal has a polarization that is substantially the same as a polarization of the first antenna and is substantially orthogonal to a polarization of the second antenna;

means for determining whether a response to the first RF test signal is received;

means for transmitting a second RF test signal through the opening, wherein each tag positioned adjacent to the opening is positioned such that the second RF test signal has a polarization that is substantially the same as the polarization of the second antenna and is substantially orthogonal to the polarization of the first antenna; and

means for determining whether a response to the second RF test signal is received.