Antenna structure

1. An antenna structure, comprising:

a ground plane;

a feeding connection element, connected to a signal source;

a first radiation element, connected to the feeding connection element;

a second radiation element, connected to the feeding connection element, wherein the second radiation element and the first radiation element substantially extend in opposite directions;

a third radiation element, connected to the ground plane, and partially surrounding the second radiation element, wherein the third radiation element further comprises a widening portion; and

a shorting radiation element, wherein a first end of the shorting radiation element is connected to the feeding connection element, and a second end of the shorting radiation element is connected to the widening portion of the third radiation element;

wherein the antenna structure covers a first low-frequency band and a second low-frequency band;

wherein a coupling is induced between the third radiation element and each of the second radiation element, the feeding connection element, and the first radiation element.

2. The antenna structure as claimed in claim 1 , wherein the third radiation element is spaced apart from the second radiation element, the feeding connection element, and the first radiation element.

3. The antenna structure as claimed in claim 1 , wherein the feeding connection element, the first radiation element, and the second radiation element together form a T-shape.

4. The antenna structure as claimed in claim 1 , wherein the third radiation element is substantially in an L-shape.

5. The antenna structure as claimed in claim 1 , wherein a coupling is induced between an open end of the second radiation element and the widening portion of the third radiation element.

6. The antenna structure as claimed in claim 1 , further comprising:

a fourth radiation element, connected to the ground plane, wherein the fourth radiation element is substantially parallel to a part of the first radiation element, and wherein the antenna structure further covers a first high-frequency band, a second high-frequency band, and a third high-frequency band.

7. The antenna structure as claimed in claim 6 , wherein the fourth radiation element substantially has a straight-line shape.

8. The antenna structure as claimed in claim 6 , further comprising:

a fifth radiation element, connected to the first radiation element, wherein the fifth radiation element and the first radiation element substantially extend in the same direction.

9. The antenna structure as claimed in claim 8 , wherein a width of the fifth radiation element is larger than a width of a connection portion coupled between the fifth radiation element and the first radiation element.

10. The antenna structure as claimed in claim 8 , wherein the first radiation element and the fifth radiation element substantially form a Y-shape.

11. The antenna structure as claimed in claim 6 , wherein the first low-frequency band is from about 699 MHz to about 787 MHz, the second low-frequency band is from about 787 MHz to about 960 MHz, the first high-frequency band is from about 1710 MHz to about 1930 MHz, the second high-frequency band is from about 1930 MHz to about 2300 MHz, and the third high-frequency band is from about 2300 MHz to about 2900 MHz.

12. The antenna structure as claimed in claim 1 , wherein a length of the third radiation element is substantially equal to 0.25 wavelength of the first low-frequency band.

13. The antenna structure as claimed in claim 6 , wherein a total length of the feeding connection element and the second radiation element is substantially equal to 0.25 wavelength of the first high-frequency band.

14. The antenna structure as claimed in claim 6 , wherein a length of the fourth radiation element is substantially equal to 0.25 wavelength of the second high-frequency band.

15. The antenna structure as claimed in claim 6 , wherein a length of the shorting radiation element is substantially equal to 0.5 wavelength of the third high-frequency band.

16. The antenna structure as claimed in claim 6 , wherein a first coupling gap is formed between the second radiation element and the third radiation element, a second coupling gap is formed between the first radiation element and the fourth radiation element, and a third coupling gap is formed between an open end of the second radiation element and the widening portion of the third radiation element.

17. The antenna structure as claimed in claim 16 , wherein a width of the first coupling gap is smaller than 3 mm, a width of the second coupling gap is smaller than 5 mm, and a width of the third coupling gap is smaller than 3 mm.

18. The antenna structure as claimed in claim 1 , wherein a total length of the feeding connection element and the first radiation element is substantially equal to 0.25 wavelength of the second low-frequency band.

19. An antenna structure, comprising:

a ground plane;

a feeding connection element, connected to a signal source;

a first radiation element, connected to the feeding connection element;

a second radiation element, connected to the feeding connection element, wherein the second radiation element and the first radiation element substantially extend in opposite directions;

a third radiation element, connected to the ground plane, and partially surrounding the second radiation element, wherein the third radiation element further comprises a widening portion; and

a shorting radiation element, wherein a first end of the shorting radiation element is connected to the feeding connection element, and a second end of the shorting radiation element is connected to the widening portion of the third radiation element;

wherein the antenna structure covers a first low-frequency band and a second low-frequency band;

wherein a coupling is induced between an open end of the second radiation element and the widening portion of the third radiation element.