Electromagnetic field generation antenna for a transponder

• US 7,023,391 B2
• Filed: 05/17/2001
• Issued: 04/04/2006
• Est. Priority Date: 05/17/2000
• Status: Expired due to Term

• Current Assignee: STMicroelectronics SA (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SA (STMicroelectronics NV)
• Inventors: Wuidart, Luc, Bardouillet, Michel
• Primary Examiner(s): Ho, Tan
• Application Number:
  US09/860,029
• Publication Number:
  US 20020003498A1
• Time in Patent Office: 1,783 Days
• Field of Search: 343/741, 343/742, 343/745, 343/749, 343/860, 343/866, 343/867, 343/895, 342/42, 342/43, 340/505, 340/572, 340/825.34, 235/380, 235/385, 235/439, 235/440, 235/492
• US Class Current: 343/749
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 7/005 with variable reactance for tuning the antenna

Abstract

An antenna for generating an electromagnetic field including several planar inductive cells parallel connected in an array and forming, in association with at least one capacitor, an oscillating circuit adapted to being excited by a high-frequency signal.

Claims

1. An antenna for generating an electromagnetic field, including a plurality of inductive cells parallel connected in a planar array and forming, in association with at least one capacitor, an oscillating circuit adapted to connect to a high-frequency excitation signal.

2. The antenna of claim 1, wherein all cells have identical inductance values.

3. The antenna of claim 2, wherein a natural resonance frequency of the oscillating circuit is chosen to approximately correspond to a frequency of the excitation signal.

4. The antenna of claim 1, connected in series with the at least one capacitor.

5. The antenna of claim 1, connected in parallel with the at least one capacitor.

6. The antenna of claim 1, wherein each cell includes a winding having a number of turns, the number of turns selected based on a surface area of the planar array of cells.

7. A terminal for generating a high-frequency electromagnetic field for at least one transponder, including the antenna of claim 1.

8. The terminal of claim 7, wherein the oscillating circuit has a natural resonance frequency and the at least one capacitor has a greater capacitance than would a capacitor included as part of an antenna of a same size and having a same natural resonance frequency but formed of a single inductive cell.

9. The antenna of claim 1, each inductive cell being formed by one or more coplanar and concentric turns.

10. The antenna of claim 9, the coplanar and concentric turns being of a hexagonal geometry.

11. The antenna of claim 10, the inductive cells of the antenna being of a hexagonal geometry and forming groups of seven inductive cells that share the at least one capacitor.

12. The antenna of claim 11, wherein the inductive cells of a group of seven inductive cells form connections with the terminals of the shared at least one capacitor on the back side of a printed circuit upon which the inductive cells are formed.

13. The antenna of claim 12, wherein each side of one inductive cell of the group of seven inductive cells is adjacent to a side of each of the other six inductive cells of the group of seven inductive cells.

14. The antenna of claim 11, the at least one capacitor being formed across a thickness of a printed circuit upon which the inductive cells are formed.

15. The antenna of claim 1, the antenna being part of an integrated circuit.

16. The antenna of claim 1, wherein the plurality of inductive cells includes at least three inductive cells.

17. The antenna of claim 1, wherein the planar array includes at least two columns of inductive cells and at least two rows of inductive cells.

18. An antenna for generating an electromagnetic field, comprising a plurality of inductive cells electrically connected in parallel and arranged in a planar array;

wherein the plurality of inductive cells are operative to connect to a high frequency excitation signal.

19. The antenna of claim 18, further comprising at least one capacitor, such that the at least one capacitor and the plurality of inductive cells form, in combination, an oscillating circuit.

20. The antenna of claim 19, the at least one capacitor being formed across a thickness of a printed circuit upon which the inductive cells are formed.

21. The antenna of claim 18, each inductive cell being formed by one or more coplanar and concentric turns.

22. The antenna of claim 21, the coplanar and concentric turns being of a hexagonal geometry.

23. The antenna of claim 22, the inductive cells of the antenna being of a hexagonal geometry and forming groups of seven inductive cells that share the at least one capacitor.

24. The antenna of claim 23, wherein the inductive cells of a group of seven inductive cells form connections with the terminals of the shared at least one capacitor on the back side of a printed circuit upon which the inductive cells are formed.

25. The antenna of claim 24, wherein each side of a one inductive cell of a group of seven inductive cells is adjacent to a single side of each of the other six inductive cells of the group of seven inductive cells.

26. The antenna of claim 18, the antenna being part of an integrated circuit.

27. The antenna of claim 18, wherein the plurality of inductive cells includes at least three inductive cells.

28. The antenna of claim 18, wherein the planar array includes at least two columns of inductive cells and at least two rows of inductive cells.