WIDE BANDWIDTH HYBRID ANTENNA FOR COMBINATION EAS AND RFID LABEL OR TAG

• US 20120001814A1
• Filed: 06/29/2011
• Published: 01/05/2012
• Est. Priority Date: 07/01/2010
• Status: Active Grant

• Current Assignee: Sensormatic Electronics LLC (Johnson Controls International plc)
• Original Assignee: Sensormatic Electronics LLC (Johnson Controls International plc)
• Inventors: COPELAND, Richard L., DAY, Edward
• Granted Patent: US 8,711,046 B2
• Time in Patent Office: Days
• US Class Current: 343/726
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H01Q 21/30 Combinations of separate antenna units operating in different wavebands and connected to a common feeder system
• CPC Class Codes: H01Q 5/357 using a single feed point
• 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 9/28 Conical, cylindrical, cage, strip, gauze, or like elements having an extended radiating surface; Elements comprising two conical surfaces having collinear axes and adjacent apices and fed by two-conductor transmission lines waveguide horns or mouths H01Q13/00; slot antennas H01Q13/00
• CPC Class Codes: Y10T 29/49016 Antenna or wave energy "plumbing" making

Abstract

A radio frequency identification (RFID) antenna exhibiting a multiple resonance is disclosed. In one exemplary embodiment, a dipole antenna and a loop antenna are disposed upon a substrate and have dimensions and orientation to exhibit the multiple resonance. The dipole antenna may exhibit a first dipole section having a first length and second dipole section having a second length. The loop antenna may be disposed in a region of the dipole antenna. The ratio of the perimeter of the loop antenna to the sum of the lengths of the dipole sections may be selected to exhibit the multiple resonance.

Claims

1. A Radio Frequency Identification (RFID) antenna, comprising:

a dipole antenna including a first dipole section having a first length and a second dipole section having a second length; and

a loop antenna having a perimeter, the loop antenna being electrically coupled to the first dipole section and electrically coupled to the second dipole section, the length of the first and second dipole sections and the perimeter of the loop selected to achieve a multiple resonance in a predetermined frequency band.

2. The RFID antenna of claim 1, wherein the electrical coupling is achieved by direct connection of conductors forming the dipole antenna and the loop.

3. The RFID antenna of claim 2, wherein the RFID antenna further includes a plurality of feed tabs, the first dipole section electrically connects to the loop antenna at a first location and the second dipole section electrically connects to the loop antenna via the feed tabs at locations separate from the first location.

4. The RFID antenna of claim 3, wherein the loop antenna has a width and wherein the feed tab locations are no further than substantially a midpoint of the loop antenna width.

5. The RFID antenna of claim 1, wherein the loop antenna is substantially rectangular and is oriented at an acute angle with respect to the first dipole section of the dipole antenna.

6. The RFID antenna of claim 1, wherein the predetermined frequency band is from substantially 850 Megahertz (MHz) to substantially 960 MHz.

7. The RFID antenna of claim 1, wherein a ratio of the loop perimeter to the sum of the lengths of the first and second dipole sections is between about 0.22 to about 0.35.

8. The RFID antenna of claim 1, wherein the loop perimeter is substantially between 15 millimeters to 50 millimeters.

9. The RFID antenna of claim 8, wherein the sum of the lengths of the first and second dipole sections is substantially between 40 millimeters and 230 millimeters.

10. The RFID antenna of claim 1, further including a substrate, wherein the dipole antenna and the loop are disposed upon the substrate.

11. A combination Electronic Article Surveillance (EAS)/Radio Frequency Identification (RFID) security tag, comprising:

an EAS component;

an RFID component, comprising;

a dipole antenna having a first section having a first length and a second section having a second length;

a loop antenna in electrical communication with the dipole antenna, the loop antenna having a perimeter, the first length and the second length of the dipole antenna and the loop antenna being selected to exhibit a multiple resonance in a predetermined frequency band.

12. The security tag of claim 11, further comprising an RFID integrated circuit coupled to the loop antenna.

13. The security tag of claim 11, wherein the second section is coupled to the loop antenna by conductive coupling at a plurality of locations along the loop antenna.

14. The security tag of claim 13, wherein the number and position of the locations causes a broadening of a resonance exhibited by the security tag.

15. A method of providing an RFID antenna, comprising:

determining dimensions and orientation of a dipole antenna and a loop antenna to exhibit a multiple resonance in a selected frequency band by selecting a ratio of an overall length of the dipole antenna to a perimeter of the loop antenna to be within a predetermined range;

determining positions of a quantity of feed tabs at which a branch of the dipole antenna and the loop antenna are electrically connected, the positions and number selected to control a breadth of a resonance exhibited by the RFID antenna;

disposing on a substrate a conductor patterned to exhibit a dipole antenna and a loop antenna of the chosen dimensions and orientation, the conductor patterned to connect the dipole antenna and the loop antenna at the chosen positions.

16. The method of claim 15, wherein the loop antenna is chosen to be oriented with respect to the dipole antenna so that the RFID antenna exhibits a predetermined near field radiation pattern and a predetermined far field radiation pattern.

17. The method of claim 15, wherein the loop antenna is rectangular and is oriented at an acute angle with respect to a branch of the dipole antenna.

18. The method of claim 17, wherein the acute angle is substantially between 45 and 60 degrees.

19. The method of claim 15, wherein the dipole antenna has a first branch of a first length and a second branch of a second length different from the first length.

20. The method of claim 15, wherein a first branch of the dipole connects to the loop antenna at a first location, and a second branch of the dipole connects to the loop antenna at multiple feed tab locations, the first branch being longer than the second branch.