LARGE SCALE FOLDED DIPOLE ANTENNA FOR NEAR-FIELD RFID APPLICATIONS

• US 20090079573A1
• Filed: 09/02/2008
• Published: 03/26/2009
• Est. Priority Date: 08/31/2007
• Status: Active Grant

• Current Assignee: Sensormatic Electronics LLC (Johnson Controls International plc)
• Original Assignee: Tyco Fire & Security GmbH (Johnson Controls International plc)
• Inventors: Jiang, Bing, Trivelpiece, Steve Edward, Campero, Richard John
• Granted Patent: US 8,730,121 B2
• Time in Patent Office: Days
• US Class Current: 340/572.700
• 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 7/10316 using at least one antenna particularly designed for interrogating the wireless record carriers antennas in general H01Q1/22
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 11/14 with parts bent, folded, shaped or screened or with phasing impedances, to obtain desired phase relation of radiation from selected sections of the antenna or to obtain desired polarisation effect H01Q11/20 takes precedence
• 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 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
• CPC Class Codes: H01Q 9/265 Open ring dipoles; Circular dipoles

Abstract

In accordance with a preferred embodiment of the invention, reader antennas are provided within storage fixtures or supporting fixtures for transporting RF signals between, for example, an RFID reader and an RFID tag. In a preferred embodiment, the RFID-enabled fixtures are implemented using an intelligent network, which may allow enhanced flexibility in controlling systems for interrogation of RFID antennas.

Claims

1. An antenna assembly for use with a predetermined carrier signal having a predetermined frequency and wavelength associated therewith, comprising:

a dipole antenna, the dipole antenna including two electrically conductive elements of unequal lengths that are also not simple multiples of each other so that when transmitting at the wavelength of the carrier signal, at least one moving null is created within the dipole antenna, wherein each of the two electrically conductive elements is connected at one end to a common feed-point and has another end, wherein the two electrically conductive elements form a loop-like shape with a small gap between the another end of each of the two electrically conductive elements.

2. The antenna assembly of claim 1 wherein the loop-like shape is regular.

3. The antenna assembly of claim 2 wherein the regular shape is one of rectangular, circular, elliptical, and triangular.

4. The antenna assembly of claim 3, wherein the common feed-point can be anywhere along the shape.

5. The antenna assembly of claim 3 wherein a longer one of the two electrically conductive elements is longer than the wavelength of the predetermined carrier signal.

6. The antenna assembly of claim 1 wherein the loop-like shape is irregular.

7. The antenna assembly of claim 6, wherein the common feed-point can be anywhere along the shape.

8. The antenna assembly of claim 6 wherein a longer one of the two electrically conductive elements is longer than the wavelength of the predetermined carrier signal.

9. An antenna assembly of claim 1 wherein the carrier signal has another wavelength, and further including:

another dipole antenna, the another dipole antenna comprising another two electrically conductive elements of unequal lengths that are also not simple multiples of each other so that when transmitting at the another wavelength of the carrier signal, at least one moving null is created within the another dipole antenna, wherein each of the another two electrically conductive elements is connected at a first end to another common feed-point and has a second end, wherein the another two electrically conductive elements form a loop-like shape with another small gap between the second end of each of the another two electrically conductive elements.

10. The antenna assembly of claim 9 wherein the wavelength and the another wavelength are the same.

11. The antenna assembly of claim 9 wherein the wavelength and the another wavelength are different.

12. The antenna assembly of claim 9 wherein the two electrically conductive elements are disposed within a cover and the another two electrically conductive elements are disposed within another cover.

13. The antenna assembly of claim 12 wherein RFID tagged items monitored by a host system are placed in the vicinity of at least one of the cover and the another cover.

14. The antenna system of claim 13 wherein the host system comprises:

a host computer;

a switch control unit;

an RFID reader coupled to each of the dipole antenna and the another dipole antenna through the switch control unit and coupled to the host computer, wherein the RFID reader and the switch control unit are controlled by the host computer.

15. The antenna system of claim 9 wherein the loop-like shape of the dipole antenna is different from the loop-like shape of the another dipole antenna and the at least one null in the dipole antenna is different from the at least one null in the another dipole antenna.

16. The antenna assembly of claim 1 wherein the two electrically conductive elements are disposed within a cover.

17. The antenna assembly of claim 1 wherein RFID tagged items monitored by a host system are placed in the vicinity of the dipole antenna.

18. The antenna system of claim 17 wherein the host system comprises:

a host computer;

an RFID reader coupled to the dipole antenna and coupled to the host computer, wherein the RFID reader is controlled by the host computer.

19. A method of eliminating reception dead-spaces for a plurality of stationery RFID tagged items using a stationery RFID reader dipole antenna associated therewith that transmits at a predetermined carrier signal having a predetermined frequency and wavelength associated therewith to each of the plurality of stationery RFID tagged items, the method comprising the steps of:

providing the stationery RFID reader dipole antenna with two electrically conductive elements of unequal lengths that are also not simple multiples of each other so that when transmitting at the wavelength of the carrier signal, at least one moving null is created within the stationery RFID reader dipole antenna, wherein each of the two electrically conductive elements is connected at one end to a common feed-point and has another end, wherein the two electrically conductive elements form a loop-like shape with a small gap between the another end of each of the two electrically conductive elements; and

causing the stationery RFID reader dipole antenna to transmit the carrier signal to the plurality of stationery RFID tagged items so that the carrier signal within the stationery RFID reader dipole antenna will have at least one moving null created therein, wherein the moving null substantially eliminates the reception dead spaces that could otherwise occur between the stationery RFID reader dipole antenna and the plurality of stationery RFID tagged items.

20. The method according to claim 19 wherein during the step of causing at least two moving nulls are created within the stationery RFID reader dipole antenna.

21. The method according to claim 19 wherein the carrier signal has another wavelength, and

wherein the step of providing provides another stationery RFID reader dipole antenna that includes another two electrically conductive elements of unequal lengths that are also not simple multiples of each other so that when transmitting at the another wavelength of the carrier signal, at least one moving null is created within the another stationery RFID reader dipole antenna, wherein each of the another two electrically conductive elements is connected at a first end to another common feed-point and has a second end, wherein the another two electrically conductive elements form a loop-like shape with another small gap between the second end of each of the another two electrically conductive elements;

and

wherein the step of causing causes each of the plurality of RFID tagged items to receive at least one of the carrier signal at the wavelength and the carrier signal at the another wavelength.

22. The method according to claim 21 wherein during the step of causing at least two moving nulls are created within each of the RFID reader dipole antenna and the another RFID reader dipole antenna.

23. The method according to claim 22 wherein step of causing causes at least some of the plurality of RFID tagged items to receive both the carrier signal at the wavelength and the carrier signal at the another wavelength at different periods of time.

24. The method according to claim 23 wherein the wavelength and the another wavelength are the same.

25. The method according to claim 21 wherein during the step of causing the at least one moving null created within each of the RFID reader dipole antenna and the another RFID reader dipole antenna are different from each other.