Radio frequency identification tag

• US 7,336,243 B2
• Filed: 05/28/2004
• Issued: 02/26/2008
• Est. Priority Date: 05/29/2003
• Status: Expired due to Fees

• Current Assignee: SkyCross Co., Ltd.
• Original Assignee: SkyCross, Inc.
• Inventors: Farrar, John Charles, Caimi, Frank M., Jo, Young-Min, Tornatta, Jr., Paul A.
• Primary Examiner(s): Ho, Tan
• Application Number:
  US10/856,354
• Publication Number:
  US 20050024287A1
• Time in Patent Office: 1,369 Days
• Field of Search: 343/700.MS, 343/895, 343/767, 343/770, 340/572.1, 340/572.7
• US Class Current: 343/895
• CPC Class Codes: G06K 19/0726 the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G06K 19/07786 the antenna being of the HF type, such as a dipole
• 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 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 9/16 with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole H01Q9/44 takes precedence
• CPC Class Codes: H01Q 9/285 Planar dipole H01Q9/065 takes precedence; patch antenna H01Q9/0407

Abstract

A radio frequency identification tag attached to an object and comprising an antenna and an integrated circuit for providing object information to a separate reader. The antenna further comprises a pair of meanderline transmission lines each terminated at a first end for conductive connection to the integrated circuit. A shorting bar connected between the pair of meanderline transmission lines at the first ends is operative to match an antenna impedance with an integrated circuit impedance.

Claims

1. A U-shaped antenna comprising:

first and second conductive pads;

a first slow wave conductor a electrical communication with the first conductive pad forming a first leg of the U-shaped antenna;

a second slow wave conductor in electrical communication with the second conductive pad forming a second leg of the U-shaped antenna;

where current flow through the first and second conductive pads is in a same direction such that the first and second conductive pad comprise primary radiating regions of the antenna; and

a bridging conductor disposed between the first and the second slow wave conductors for completing the U-shaped antenna.

2. The antenna of claim 1 wherein a material of the first and the second slow wave conductors and a material of the first and the second conductive pads comprises conductive material further comprising one or more abrupt transitions formed therein.

3. The antenna of claim 1 wherein a effective aperture of the antenna is increased by the abrupt transitions.

4. The antenna of claim 1 wherein the first and the second conductive pads comprise a generally rectangular shape.

5. The antenna of claim 1 wherein the first and the second slow wave conductors comprise first and second meanderline transmission lines.

6. The antenna of claim 5 wherein each of the first and the second meanderline transmission lines comprises a plurality of undulating conductive segments, and wherein current flow in certain ones of the plurality of undulating segments of the first meanderline transmission line is in the same direction as current flow in certain ones of the plurality of undulating segments of the second meanderline transmission line.

7. The antenna of claim 6 wherein current flow in the plurality of undulating segments of the first and the second meanderline transmission lines comprises axial current flow in a direction of the first and the second legs of the U-shaped antenna or radial current flow perpendicular to the first and the second legs of the U-shaped antenna, and wherein the axial current flow produces a polarized signal in a first direction and the radial current flow produces a polarized signal in a second direction.

8. The antenna of claim 7 wherein current flow is in a same direction in the first and the second conductive pads.

9. The antenna of claim 1 wherein each one of the first and the second slow wave conductors exhibits an electrical length greater than a physical length.

10. An antenna comprising a slow wave section and a radiating section, wherein the slow wave section is located at or near a current minimum at or near a resonant frequency so as to reduce heating losses and improve radiation efficiency of the antenna and wherein the radiating section includes one or more conductive pads in which current flows in the same direction such that the one or more conductive pads comprise the primary radiating regions of the radiating section.

11. An antenna responsive to a transmitting/receiving component, comprising:

first and second spaced-apart slow wave conductors each including first and second terminal ends thereof;

first pad connected to the fin terminal end of the first slow wave conductor;

a second pad connected to the first terminal end of the second slow wave conductor;

wherein the transmitting/receiving component is electrically connected between the first and the second pads; and

a conductive segment electrically connected between the first and the pads.

12. The antenna of claim 11 wherein the first and the second slow wave conductors are disposed in a substantially parallel orientation.

13. The antenna of claim 11 for transmitting and receiving electromagnetic energy, wherein current flow is in a substantially same direction in the first and the second pads, and wherein the first and the second pads comprise the primary radiating elements of the antenna.

14. The antenna of claim 11 further comprising a third pad connected to the second terminal end of the first slow wave conductor and a fourth pad connected to the second terminal end of the second slow wave conductor.

15. The antenna of claim 11 wherein the conductive segment is disposed in an electrically parallel relation to the transmitting/receiving component.

16. The antenna of claim 15 wherein an impedance of the transmitting/receiving component impedance includes a real component and a reactive component, and wherein the conductive segment transforms the real component to substantially match a real impedance of the antenna and substantially cancels the reactive component at or near an antenna operating frequency.

17. The antenna of claim 11 wherein the conductive segment provides a low impedance electrical path around the transmitting/receiving component for limiting electrostatic discharge into the transmitting/receiving component.

18. The antenna of claim 11 wherein the conductive segment and the transmitting/receiving component each exhibit an impedance, and wherein the electrical properties of the conductive segment are determined to substantially match the transmitting/receiving component impedance to the impedance seen by the transmitting/receiving component at or near an antenna operating frequency.

19. The antenna of claim 11 wherein the first and the second slow wave conductors and the first and second pads comprise one or more linear edges.

20. The antenna of claim 11 wherein the first and the second slow wave conductors and the first and second pads comprise abrupt structural transitions for increasing an effective antenna aperture.

21. The antenna of claim 11 wherein the first and the second pads each comprise a rectangular shaped pad.

22. The antenna of claim 11 wherein the first slow wave conductor comprises a first meanderline transmission line and the second slow wave conductor comprises a second meanderline transmission line.

23. The antenna of claim 22 wherein each one of the first and the second meanderline transmission lines comprises a plurality of undulating conductive segments, and wherein current flow in certain ones of the plurality of undulating conductive segments of the first meanderline transmission line is in the same direction as current flow in certain ones of the plurality of undulating conductive segments of the second meanderline transmission line.

24. The antenna of claim 11 wherein the antenna comprises an electrical length greater than a physical length.

25. The antenna of claim 11 wherein the transmitting/receiving component is physically disposed between the first and the second pads.

26. An antenna having a resonant frequency and responsive to a transmitting/receiving component, comprising:

first and second spaced-apart slow wave conductors each including first and second terminal ends thereof, at least one of the first and the second slow wave conductors including a conductive tuning region disposed serially along a length thereof, the resonant frequency responsive to a current path length through the at least one of the first and the second slow wave conductors and further responsive to a change in current path length as determined by the conductive tuning region;

a first pad connected to the first terminal end of die first slow wave conductor;

a second pad connected to the first terminal end of the second slow wave conductor; and

wherein the transmitting/receiving component is electrically connected between the first and the second pads.

27. The antenna of claim 26 wherein the first and second slow wave conductors each further comprise undulating segments, and wherein the first slow wave conductor comprises a first conductive tuning region and the second slow wave conductor comprises a second conductive tuning region, and wherein the first and the second tuning regions are each disposed between two successive segments of the first slow wave conductor, and wherein the second conductive tuning region is disposed between two successive segments of the second slow wave conductor.

28. The antenna of claim 26 wherein the first and second slow wave conductors each further comprise undulating segments and wherein the first slow wave conductor comprises a first conductive tuning region and the second slow wave conductor comprises a second conductive tuning region, arid wherein the first conductive tuning region is disposed between the first pad and an adjacent undulating segment of the first slow wave conductor, and wherein the second conductive tuning region is disposed between the second pad and an adjacent undulating segment of the second slow wave conductor.

29. The antenna of claim 26 further comprising a third pad connected to the first terminal end of the first slow wave conductor and a fourth pad connected to the first terminal end of the second slow wave conductor, and wherein the first and second slow wave conductors each further comprising undulating segments, and wherein the first slow wave conductor comprises a first conductive tuning region disposed between the third pad and an adjacent undulating segment of the first slow wave conductor, and wherein the second slow wave conductor comprises a second conductive tuning region disposed between the fourth pad and an adjacent undulating segment of the second slow wave conductor.

30. An antenna comprising:

a conductive sheet having a plurality of shaped openings formed therein, wherein the openings form first and second parallel spaced-apart meanderline transmission lines, first and second apertures disposed at first terminal ends of the first and the second meanderline transmission lines, respectively, and third sad fourth apertures disposed at second terminal end of the first and the second meanderline transmission line, respectively, and a bridging opening connecting the first and the second apertures.