Antenna device and IC card having the same

1 . An antenna device comprising:

a metal plate having a first slit extending in a long side direction thereof and a second slit extending in a short side direction thereof;

a first coil disposed so as to overlap with the metal plate in a plan view and circling along an outer edge of the metal plate; and

a second coil electrically connected to the first coil, disposed so as to be surrounded by the first coil, and disposed so as to overlap with the first slit,

wherein the first slit has a first end that is open to divide the outer edge of the metal plate and a second end terminating without reaching the outer edge of the metal plate,

wherein the second slit has a third end that is open to divide the outer edge of the metal plate and a fourth end terminating without reaching the outer edge of the metal plate, and

wherein a length of the first slit in the long side direction is equal to or longer than half a length of the metal plate in the long side direction, or a length of the second slit in the short side direction is equal to or longer than half a length of the metal plate in the short side direction.

2 . The antenna device as claimed in claim 1 , wherein the first slit includes a first section overlapping with the second coil, a second section located between the first section and the first end, and a third section located between the first section and the second end.

3 . The antenna device as claimed in claim 1 , wherein the second slit is longer than the first slit.

4 . The antenna device as claimed in claim 3 , wherein the fourth end of the second slit is positioned inside an innermost turn of the first coil.

5 . The antenna device as claimed in claim 3 , wherein a first distance between the fourth end of the second slit and the outer edge of the metal plate in the short side direction is smaller than a second distance between the second end of the first slit and the second slit in the long side direction.

6 . The antenna device as claimed in claim 3 , wherein a virtual line on the metal plate extending in the long side direction from the second end of the first slit to the outer edge of the metal plate intersects with the second slit.

7 . The antenna device as claimed in claim 6 , wherein a third distance between the second end of the first slit and the second slit along the virtual line is smaller than a length of the first slit in the long side direction.

8 . The antenna device as claimed in claim 1 , wherein the first slit is longer than the second slit.

9 . The antenna device as claimed in claim 8 , wherein the second end of the first slit is positioned inside an innermost turn of the first coil.

10 . The antenna device as claimed in claim 8 ,

wherein the outer edge of the metal plate includes first and second outer edge extending in the long side direction,

wherein the first slit is located closer to the first outer edge than the second outer edge, and

wherein the third end of the second slit divides the second outer edge.

11 . The antenna device as claimed in claim 8 , wherein a virtual line on the metal plate extending in the short side direction from the fourth end of the second slit to the outer edge of the metal plate intersects with the first slit.

12 . The antenna device as claimed in claim 11 , wherein a distance between the fourth end of the second slit and the first slit along the virtual line is smaller than a length of the second slit in the short side direction.

13 . The antenna device as claimed in claim 1 , further comprising a capacitor electrically connected to the first and second coils,

wherein the capacitor overlaps with the metal plate in a plan view so as not to overlap with the first and second slits.

14 . The antenna device as claimed in claim 13 , wherein the capacitor is electrically connected in series to the first and second coils.

15 . The antenna device as claimed in claim 13 ,

wherein the capacitor is electrically connected in parallel with the first and second coils, and

wherein the first coil is shorter in line length than the second coil.

16 . An IC card comprising:

an antenna device comprising:

a first metal plate having a first slit extending in a long side direction thereof and a second slit extending in a short side direction thereof;

a first coil disposed so as to overlap with the first metal plate in a plan view and circling along an outer edge of the first metal plate; and

a second coil electrically connected to the first coil, disposed so as to be surrounded by the first coil, and disposed so as to overlap with the first slit;

a second metal plate having an opening; and

an IC module disposed in the opening of the second metal plate,

wherein the first slit has a first end that is open to divide the outer edge of the first metal plate and a second end terminating without reaching the outer edge of the first metal plate,

wherein the second slit has a third end that is open to divide the outer edge of the first metal plate and a fourth end terminating without reaching the outer edge of the first metal plate,

wherein a length of the first slit in the long side direction is longer than half a length of the metal plate in the long side direction, or a length of the second slit in the short side direction is longer than half a length of the metal plate in the short side direction, and

wherein the first and second coils are sandwiched between the first and second metal plates such that the IC module overlaps with the second coil.

17 . An antenna device comprising:

a metal plate having first and second outer edges extending in a first direction, third and fourth outer edges extending in a second direction perpendicular to the first direction, a first slit extending in the second direction, and a second slit extending in the first direction;

a first coil disposed so as to overlap with the metal plate in a third direction perpendicular to the first and second directions and circling along the first, third, second, and fourth outer edges of the metal plate; and

a second coil electrically connected to the first coil, disposed so as to be surrounded by the first coil, and disposed so as to overlap with the first slit in the third direction,

wherein the first slit has a first end in the second direction that is open to divide the first outer edge of the metal plate and a second end in the second direction terminating without reaching the second outer edge of the metal plate,

wherein the second slit has a third end in the first direction that is open to divide the third outer edge of the metal plate and a fourth end in the first direction terminating without reaching the fourth outer edge of the metal plate, and

wherein a virtual line on the metal plate extending in the second direction from the second end of the first slit to the second outer edge of the metal plate intersects with the second slit.

18 . The antenna device as claimed in claim 17 , wherein a distance between the second end of the first slit and the second slit along the virtual line is smaller than a length of the first slit in the second direction.

19 . The antenna device as claimed in claim 17 , wherein a length of the second slit in the first direction is longer than half a length of the first outer edge of the metal plate.

20 . The antenna device as claimed in claim 17 , wherein a length of each of the first and second outer edges of the metal plate in the first direction is shorter than a length of each of the third and fourth outer edges of the metal plate in the second direction.