Directional wire antennas for radio frequency identification tag system

• US 7,250,917 B1
• Filed: 01/13/2005
• Issued: 07/31/2007
• Est. Priority Date: 01/14/2004
• Status: Expired due to Fees

• Current Assignee: Louis H. Thompson, Sheree Hagan
• Original Assignee: Louis H. Thompson, Sheree Hagan
• Inventors: Hagan, Sheree, Thompson, Louis H.
• Primary Examiner(s): Wimer; Michael C.
• Application Number:
  US11/033,888
• Time in Patent Office: 929 Days
• Field of Search: 343/789, 343/795, 343/700.MS, 343/828, 340/572.7
• US Class Current: 343/828
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles
• CPC Class Codes: H01Q 1/007 specially adapted for indoor communication
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 1/36 Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewithH01Q1/08, H01Q1/14 take precedence
• CPC Class Codes: H01Q 19/106 using two or more intersecting plane surfaces, e.g. corner reflector antennas
• CPC Class Codes: H01Q 9/26 with folded element or elements, the folded parts being spaced apart a small fraction of operating wavelength resonant loop antennas H01Q7/00
• CPC Class Codes: H01Q 9/42 with folded element, the folded parts being spaced apart a small fraction of the operating wavelength

Abstract

Directional wire antennas for use in article or personal tracking and/or inventory monitoring or control systems wherein the antennas are specifically configured to provide a tunable vertical beam angle which is less than their horizontal beam angle. The antennas are modified or non-balanced dipole or monopole structures having non-symmetrical wire legs wherein at least one leg has segments extending angularly in a linear manner in two separate planes. In preferred embodiments the antennas are designed to receive signals from active RFID (radio frequency identification) tags placed on objects to be monitored within confined or defined structures without bleed over of signals from tags placed on objects at different vertical levels of the structure.

Claims

1. A directional wire antenna for radio frequency identification tag systems, the antenna including a wire body having first and second legs extending angularly outwardly from opposite ends of a generally central member, said second leg having inner and outer segments which are angularly oriented relative to one another such that a portion of said central member and said second leg are in somewhat of a u-shaped configuration with said portion of said central member and said outer segment of said second leg being connected by said inner segment of said second leg and said outer segment of said second leg extending at a compound angle relative to a longitudinal axis of said portion of said central member and terminating in a free end.

2. The directional wire antenna of claim 1 wherein an elongated axis of said outer segment of said second leg traverses an elongated axis of said inner segment of said second leg at approximately a 45 degree angle.

3. The directional wire antenna of claim 1 wherein said first leg includes an inner segment extending outwardly from said central member such that said central member, said inner segment of said first leg and said inner segment of said second leg form a generally u-shaped configuration.

4. The directional wire antenna of claim 3 wherein a free end of said first leg is connected to an electrical tap for the antenna.

5. The directional wire antenna of claim 3 wherein an electrical tap for the antenna is provided along said central member.

6. The directional wire antenna of claim 3 wherein said inner and outer segments of said second leg define a plane which extends transversely with respect to a plane defined by said inner segment of said first leg and said central member.

7. The directional wire antenna of claim 3 wherein said inner segment of said first leg and said inner segment of said second leg are not parallel with one another.

8. The directional wire antenna of claim 6 wherein said inner segment of said second leg is oriented at approximately 20 degrees relative to said plane defined by said inner segment of said first leg and said central member.

9. The directional wire antenna of claim 3 wherein said first leg includes an outer segment extending from said inner segment of said first leg and terminating in a free end.

10. The directional wire antenna of claim 9 wherein said free end of said outer segment of said first leg is oriented generally towards said second leg and such that said first leg and a second portion of said central member are generally unshaped in configuration.

11. The directional wire antenna of claim 10 wherein an electrical tap for the antenna is provided along said central member.

12. The directional wire antenna of claim 1 wherein said first leg extends from one of said opposite ends of said central member in a direction generally opposite to a direction at which said second leg extends from the other of said opposite end of said central member.

13. The directional wire antenna of claim 12 in which said first leg includes at least two segments including an inner segment extending from said one of said opposite ends of said central member and an outer segment angularly oriented relative to said inner segment and terminating in a free end.

14. The directional wire antenna of claim 13 wherein said free end of said first leg and said free end of said second leg are oriented in generally opposite directions on opposite sides of said central member.

15. The directional wire antenna of claim 1 including a housing, and means for mounting said antenna within said housing.

16. The directional wire antenna of claim 1 wherein said antenna is adapted to be operable in energy ranges of approximately 1 MHz to 1 GHz.

17. The directional wire antenna of claim 1 wherein a relative configuration of said first and second legs and said central member is such that a beam angle defined by the antenna is wider in a horizontal direction than a vertical direction.

18. A method for reading radio frequency identification tags within a structure having multiple vertically spaced levels wherein objects on the multiple levels have radio frequency tags applied thereto, the method comprising the steps of:

a) providing a directional wire antenna for a radio frequency identification tag system wherein the antenna includes a wire body having first and second leas extending angularly outwardly from opposite ends of a generally central member and wherein the second lea has inner and outer segments which are angularly oriented relative to one another such that a portion of the central member and said second leg are in somewhat of a u-shaped configuration with the portion of said central member and the outer segment of the second leg being connected by the inner segment of the second leg and the outer segment of the second leg extending at a compound angle relative to a longitudinal axis of the portion of said central member and terminating in a free end and placing the directional antenna along one of the plurality of levels and orienting the antenna to receive RF signals from tags on the one of the plurality of levels, and

b) communicating the directional antenna with means for reading signals received by the antenna to identify objects only located on the one of the plurality of levels whereby the directional antenna effectively receives radio frequency signals from the tags on the one of the plurality of levels without bleed-over from signals from tags on other levels.

19. A method for reading radio frequency identification tags within a structure having multiple vertically spaced levels wherein objects on the multiple levels have radio frequency identification tags applied thereto, the method comprising the steps of:

a) placing at least one antenna having a limited vertical beam bandwidth which is generally less than a distance between floors of adjacent vertical levels on one of the plurality of levels and orienting the at least one antenna to receive RF signals from tags on the one of the plurality of levels, and

b) communicating the at least one antenna with means for reading signals received by the at least one antenna to identify objects only located on the one level whereby the at least one antenna effectively receives radio frequency signals from the tags on the one level without bleed-over from signals from tags on other levels.