Multilevel Ground-Plane for a Mobile Device

• US 20080074332A1
• Filed: 09/20/2005
• Published: 03/27/2008
• Est. Priority Date: 09/21/2004
• Status: Active Grant

• Current Assignee: Fractus SA
• Original Assignee: Fractus SA
• Inventors: Gala, David, Arronte, Alfonso, Martinez, Antonio, Baliarda, Carles
• Granted Patent: US 7,928,915 B2
• Time in Patent Office: Days
• US Class Current: 343/702
• CPC Class Codes: H01Q 1/243 with built-in antennas
• CPC Class Codes: H01Q 1/48 Earthing means; Earth screens; Counterpoises

Abstract

In accordance with the teachings described herein, a multilevel ground-plane for a mobile device is provided. The multilevel ground-plane includes a first conductive surface, a second conductive surface, and a conducting strip that couples the first conducting surface to the second conducting surface. A mobile device having a multilevel ground-plane may include a printed circuit board, an antenna radiating element attached to a surface of the printed circuit board, and the multilevel ground plane integral with the printed circuit board and electromagnetically coupled to the antenna radiating element.

Claims

1. A mobile device, comprising:

a printed circuit board;

an antenna radiating element attached to a surface of the printed circuit board; and

a multilevel ground plane integral with the printed circuit board and electromagnetically coupled to the antenna radiating element;

the multilevel ground plane comprising;

a first conducting surface;

a second conducting surface; and

a conducting strip that couples the first conducting surface to the second conducting surface;

wherein at least a portion of the multilevel ground plane defines a space-filling curve; and

wherein at least one edge of the antenna radiating element is aligned with a slot defined between the first conducting surface and the second conducting surface.

2. An antenna system, comprising a radiating element placed over a ground plane, the radiating element having at least one edge and the ground plane having at least one slot, wherein at least a part of one edge of the radiating element is positioned over a part of one slot of the ground plane.

3. Antenna system according to claim 2 wherein at least one slot is in contact at one of its ends with the perimetric edge of the ground plane.

4. Antenna system according to claim 2 or 3 wherein it comprises two aligned slots which are substantially parallel to one side of the perimetric edge of the ground plane.

5. Antenna system according to claim 4 wherein one edge of the radiating element extends over the two slots.

6. Antenna system according to any of the claims 2 to 5 wherein the slots and the edge of the radiating element placed over said slots, are substantially straight.

7. Antenna system according to any of the claims 2 to 6 wherein a part of at least one of the slot has a constant width, wherein said width is within the range 0.3 mm and 3 mm.

8. Antenna system according to any of the claims 2 to 7 wherein at least one slot has a slot segment at one of its ends, wherein said slot segment defines an angle with respect to said slot.

9. Antenna system according to claim 8 wherein said slot segment is placed below the radiating element.

10. Antenna system according to any of the claims 2 to 9, wherein at least a portion of the radiating element that operates within a determined band is positioned over a part of at least one slot of the ground plane.

11. Antenna system according to any of the claims 2 to 10 wherein it comprises a printed circuit board having at least one conducting layer, and wherein the radiating element is attached to the printed circuit board, and the ground plane is formed on said conducting layers and it is electromagnetically coupled to said radiating element.

12. Antenna system according to claim 11 wherein the ground plane is embedded within the printed circuit board and it is formed in one of its inner conducting layers.

13. Antenna system according to claim 11 or claim 12 wherein the printed circuit board is provided with a conducting layer on its upper and lower faces, wherein a ground plane is formed in each conducting layer.

14. Antenna system according to any of the claims 2 to 13 wherein at least one ground plane comprises two slots which define in the ground plane a first conducting surface, a second conducting surface, and a conducting strip that couples the first conducting surface to the second conducting surface.

15. Antenna system according to claims 13 and 14 wherein the ground planes have the same shape.

16. Antenna system according to claims 13 and 14 wherein the width of the slots of at least one ground plane is greater than the width of the slots of the other ground planes.

17. Antenna system according to claim 16, wherein the width of at least one of the slots of at least one ground plane is greater than 3 mm.

18. Antenna system according to the claims 15 to 17 wherein the at least one ground plane comprising the two slots, further comprises at least one via in the surface located between the said two slots to ground any other ground planes.

19. Antenna system according to any of the claims 16 to 18, wherein no grounded pad and/or grounded track comprised in the said printed circuit board is placed over the slots.

20. Antenna system according to any of the claims 2 to 19, wherein the radiating element comprises at least one hole defining an empty area on said radiating element, wherein the shape of said empty area is formed by polygonal shapes connected or overlapping at a contact region of their perimeter, wherein the contact region between directly connected polygonal shapes is narrower than 50% of the perimeter of said polygonal shapes, and wherein the polygonal shapes have the same number of sides but not all the polygonal shapes have the same shape.

21. Antenna system according to claims 20 wherein the polygonal shapes are rectangles.

22. Antenna system according to claims 20 or claim 21 wherein one of the polygonal shapes is connected to the perimetric edge of the radiating element.

23. Antenna system according to any of the claims 2 to 22 wherein the radiating element is substantially rectangular.

24. Antenna system according to any of the claims 2 to 23, wherein at least one of the corners of the radiating element is cut off in order to facilitate its integration into a communication device.

25. Antenna system according to any of the claims 2 to 24 wherein at least a part of one slot and/or at least a part of the conducting strips connecting two of said conducting surfaces is shaped as a space-filling curve.

26. Antenna system according to any of the claims 2 to 25 wherein at least one of the strips connecting two of said conducting surfaces is shaped as a zigzag or meandering curve.

27. Antenna system according to claim 26 wherein said space-filling curve is composed by at least ten connected segments, wherein said segments are smaller than a tenth of the operating free-space wave length and they are spatially arranged in such a way that none of said adjacent and connected segments form another longer straight segment.

28. Antenna system according to claim 26 or 27 wherein said space-filling features a box-counting dimension larger than one.

29. Antenna system according to any of the claims 2 to 28 wherein at least a portion of the geometry of said ground-plane is a multilevel structure, said multilevel structure including a set of conducting polygons, all of said polygons featuring the same number of sides, wherein said polygons are electromagnetically coupled either by means of a capacitive coupling or ohmic contact, wherein the contact region between directly connected polygons is narrower than 50% of the perimeter of said polygons.

30. Antenna system according to any of the claims 2 to 29 wherein the antenna is a multiband antenna.

31. A mobile communications device comprising an antenna system according to any of the claims 2 to 30.

32. A mobile communications device according to claim 31, wherein the antenna system conserves space inside the said mobile communication device enabling at least one component to be mounted on the printed circuit board opposite to the antenna structure.

33. A mobile communications device according to claim 32, wherein the said at least one component comprises a speaker or a vibration mechanism.

34. A mobile communication device according to any of the claims 31 to 33, wherein the communication device is selected from the group comprising:

a cellular telephone, a PDA, a pager.

35. A mobile communications device according to any of the claims 31 to 34, wherein the said mobile communications device operates in at least one typical cellular frequency band between 800 MHz and 3000 MHz.