Antenna and array antenna

1. An antenna, comprising:

a radiating element, with a shape substantially conforming to a quadrilateral, having a first side, a second side, a third side and a fourth side, wherein the first side and the third side are substantially parallel, the second side and the fourth side are substantially parallel, and the first side is substantially perpendicular to the second side;

a grounding element, surrounding the radiating element, and having an opening formed near the fourth side of the radiating element;

an extending bar, having a terminal electrically connected to the fourth side of the radiating element, and another terminal extended toward the opening of the grounding element;

a first connection element, having a terminal electrically connected to the first side and the fourth side of the radiating element, and another terminal electrically connected to the grounding element; and

a second connection element, having a terminal electrically connected to the third side and the fourth side of the radiating element, and another terminal electrically connected to the grounding element.

2. The antenna of claim 1 , wherein the first connection element and the second connection element are symmetrical with regard to a centerline of the radiating element.

3. The antenna of claim 1 , wherein the first connection element comprises a plurality of branches, and each branch is perpendicular to a neighboring branch.

4. The antenna of claim 1 , wherein the first connection element and the grounding element form an open slot, and a width of the open slot is related to a plurality of antenna characteristics.

5. The antenna of claim 1 , wherein the second connection element comprises a plurality of branches, and each branch is perpendicular to a neighboring branch.

6. The antenna of claim 1 , wherein the second connection element and the grounding element form an open slot, and a width of the open slot is related to a plurality of antenna characteristics.

7. The antenna of claim 1 , wherein lengths of the first connection element and the second connection element are substantially equal to a quarter-wavelength of a wireless signal transmitted or received by the antenna.

8. The antenna of claim 3 , wherein a first branch of the first connection element is parallel with a current direction on the radiating element.

9. The antenna of claim 5 , wherein a first branch of the second connection element is parallel with a current direction on the radiating element.

10. The antenna of claim 1 , wherein the grounding element surrounds the radiating element by forming an area such that the radiating element is disposed in the area.

11. An array antenna, comprising:

a plurality of radiating elements, each with a shape substantially conforming to a quadrilateral, having a first side, a second side, a third side and a fourth side, wherein the first side and the third side are substantially parallel, the second side and the fourth side are substantially parallel, and the first side is substantially perpendicular to the second side;

a plurality of extending bars, each electrically connected to a fourth side of a radiating element and a second side of another radiating element among the plurality of radiating elements, such that the plurality of radiating elements are concatenated in a series;

a grounding element, surrounding the plurality of radiating elements, and having an opening formed near a fourth side of a radiating element among the plurality of radiating elements;

a plurality of first connection elements, each having a terminal electrically connected to a first side and a fourth side of a radiating element among the plurality of radiating elements, and another terminal electrically connected to the grounding element; and

a plurality of second connection elements, each having a terminal electrically connected to a third side and a fourth side of a radiating element among the plurality of radiating elements, and another terminal electrically connected to the grounding element.

12. The array antenna of claim 11 , wherein the plurality of first connection elements and the plurality of second connection elements are symmetrical with regard to a centerline of the plurality of radiating elements.

13. The array antenna of claim 11 , wherein each of the plurality of first connection elements comprises a plurality of branches, and each branch is perpendicular to a neighboring branch.

14. The array antenna of claim 11 , wherein each first connection element of the plurality of first connection elements and the grounding element form an open slot, and a width of the open slot is related to a plurality of antenna characteristics.

15. The array antenna of claim 11 , wherein each of the plurality of second connection elements comprises a plurality of branches, and each branch is perpendicular to a neighboring branch.

16. The array antenna of claim 11 , wherein each second connection element of the plurality of second connection elements and the grounding element form an open slot, and a width of the open slot is related to a plurality of antenna characteristics.

17. The array antenna of claim 11 , wherein lengths of each of the plurality of first connection elements and each of the plurality of second connection elements are substantially equal to a quarter-wavelength of a wireless signal transmitted or received by the array antenna.

18. The array antenna of claim 13 , wherein a first branch of each first connection element is parallel with a current direction on the radiating element.

19. The array antenna of claim 15 , wherein a first branch of each second connection element is parallel with a current direction on the radiating element.

20. The array antenna of claim 11 , wherein the grounding element surrounds the plurality of radiating elements by forming a plurality of areas such that the plurality of radiating elements are disposed in the plurality of areas.