Flat panel antenna including liquid crystal

1. A flat panel antenna, comprising:

a first substrate on which a radiation patch and a ground plane are provided;

a second substrate;

a liquid crystal layer between the first substrate and the second substrate; and

a feed portion adjacent to the second substrate,

wherein the ground plane includes a slot,

wherein the feed portion includes a first spacing part, a second spacing part and a feed line between the first spacing part and the second spacing part,

wherein a thickness of the first substrate is greater than a thickness of the second substrate,

wherein the second substrate is disposed between the liquid crystal layer and the feed portion, and

wherein the liquid crystal layer includes liquid crystal molecules, and an arrangement of the liquid crystal molecules is changed according to a voltage applied to the ground plane and the feed line, thereby changing a dielectric constant of the liquid crystal layer.

2. The flat panel antenna of claim 1 , wherein the first substrate and the second substrate are formed of glass and have a same dielectric constant.

3. The flat panel antenna of claim 1 , wherein the thickness of the first substrate is 0.5 mm.

4. The flat panel antenna of claim 3 , wherein the thickness of the second substrate is 0.2 mm.

5. The flat panel antenna of claim 1 , wherein the thickness of the second substrate is 0.008 times to 0.018 times a wavelength corresponding to a resonance frequency of the antenna.

6. The flat panel antenna of claim 1 , wherein the first substrate includes glass and the second substrate includes polyimide.

7. The flat panel antenna of claim 1 , wherein the slot is formed in a first direction, and

wherein the feed line, the first spacing part and the second spacing part are arranged in a second direction crossing the first direction.

8. The flat panel antenna of claim 1 , wherein a width of the first spacing part and the second spacing part is twice or more of a width of the feed line.

9. The flat panel antenna of claim 1 , wherein the feed portion includes a first portion extending in a first direction and second and third portions extending from both ends of the first portion in a second direction crossing the first direction, and

wherein the first, second, and third portions and the feed line form a three-teeth comb shape.

10. The flat panel antenna of claim 1 , wherein the first and second substrates have a length along a first direction perpendicular to the feed line longer than a length along a second direction parallel to the feed line.

11. The flat panel antenna of claim 1 , wherein each of the first and second substrates is a single substrate.

12. A flat panel antenna, comprising:

first and second substrates facing each other and having different thicknesses;

a radiation patch disposed on a first side of the first substrate;

a ground plane provided on a second side of the first substrate and having a slot extended to a first direction;

a liquid crystal layer between the first and second substrates;

a feed portion attached to the second substrate and including a first spacing part, a second spacing part and a feed line located between the first spacing part and the second spacing part,

wherein the feed line and the radiation patch are electrically coupled with a voltage supplied to the feed line and transferred to the radiation patch,

wherein the second substrate is disposed between the liquid crystal layer and the feed portion, and

wherein the liquid crystal layer includes liquid crystal molecules, and an arrangement of the liquid crystal molecules is changed according to a voltage applied to the ground plane and the feed line, thereby changing a dielectric constant of the liquid crystal layer.

13. The flat panel antenna of claim 12 , wherein the first substrate and the second substrate have a same dielectric constant.

14. The flat panel antenna of claim 12 , wherein the first substrate has a thickness greater than a thickness of the second substrate.

15. The flat panel antenna of claim 14 , wherein the thickness of the first substrate is 0.5 mm.

16. The flat panel antenna of claim 14 , wherein the thickness of the second substrate is 0.2 mm.

17. The flat panel antenna of claim 12 , wherein the thickness of the second substrate is 0.008 times to 0.018 times a wavelength corresponding to a resonance frequency of the antenna.

18. The flat panel antenna of claim 12 , wherein the first substrate includes glass and the second substrate includes polyimide.

19. The flat panel antenna of claim 12 , wherein the feed line, the first spacing part and the second spacing part are arranged in a second direction perpendicular to the first direction.

20. The flat panel antenna of claim 12 , wherein the radiation patch is extended to the first direction.

21. The flat panel antenna of claim 12 , wherein a width of the first spacing part and the second spacing part is twice or more of a width of the feed line.

22. The flat panel antenna of claim 12 , wherein the feed portion includes a first portion extending in a first direction and second and third portions extending from both ends of the first portion in a second direction crossing the first direction, and

wherein the first, second, and third portions and the feed line form a three-teeth comb shape.