Antenna device having radiation characteristics suitable for ultrawideband communications

1. An antenna device comprising:

a plate-shaped conductor;

a radiating conductor that extends outward from an end portion of the plate-shaped conductor and has a length corresponding to a quarter wavelength of a first frequency;

a strip-shaped slot portion that is formed by removing a part of the plate-shaped conductor extending inward from the vicinity of the end portion from which the radiating conductor extends and has a length corresponding to a quarter wavelength of a second frequency, the second frequency being different from the first frequency; and

a feed portion that is disposed to be perpendicular to the slot portion and to cross over the slot portion and that feeds the same signals to the slot portion and the radiating conductor,

wherein a polarization plane of a radiating electric field radiating from the radiating conductor and a polarization plane of a radiating electric field radiating from the slot portion are disposed to be perpendicular to each other.

2. The antenna device according to claim 1 ,

wherein the radiating conductor is formed in a meandering shape.

3. The antenna device according to claim 2 ,

wherein the first frequency radiating from the radiating conductor is lower than the second frequency radiating from the slot portion.

4. The antenna device according to claim 1 ,

wherein the radiating conductor is bent along a longitudinal direction of the slot portion with the end portion of the plate-shaped conductor as a reference line in a state in which the radiating conductor and the plate-shaped conductor are on the same plane, and

the radiating conductor is disposed between the plate-shaped conductor and a location closest to the plate-shaped conductor.

5. The antenna device according to claim 4 ,

wherein the radiating conductor extends from the plate-shaped conductor on the same plane as the plate-shaped conductor.

6. The antenna device according to claim 4 ,

wherein the radiating conductor is disposed vertically with respect to the plate-shaped conductor.

7. The antenna device according to claim 1 ,

wherein the plate-shaped conductor and the radiating conductor are formed by using one metal plate.

8. The antenna device according to claim 7 ,

wherein the feed portion is formed by using the one metal plate formed with the plate-shaped conductor and the radiating conductor.

9. The antenna device according to claim 7 ,

wherein the plate-shaped conductor is mounted with a circuit board formed with at least an amplifying circuit,

one end of the feed portion is connected to the amplifying circuit, and

another end of the feed portion is connected to the plate-shaped conductor in the vicinity of the slot portion.

10. The antenna device according to claim 1 , further comprising:

a dielectric substrate, one surface of which being formed with a conductive pattern,

wherein the plate-shaped conductor and the radiating conductor are formed by the conductive pattern.

11. The antenna device according to claim 10 ,

wherein the dielectric substrate is formed by using a flexible substrate that can be bent.

12. The antenna device according to claim 10 ,

wherein a wiring pattern and at least an amplifying circuit are provided at an opposing surface side of the dielectric substrate,

the feed portion is formed by the wiring pattern, and

one end of the feed portion is connected to the amplifying circuit and another end of the feed portion is connected to the plate-shaped conductor through a through hole.