Antenna device and wireless terminal
An antenna device includes a metal layer for forming an antenna element in a predetermined planar shape and a ground arranged on a lower side of the metal layer. The metal layer forms a first metal forming the planar shape, a notch portion formed at the first metal, and cutting out a part of an edge of the planar shape, a second metal being an electromagnetic field coupling element arranged with a predetermined distance spaced from the first metal inside the notch portion, and a feeder line formed outside the planar shape, and to be connected with the second metal via an opening portion of the notch portion. For the second metal, a width at the opening portion is smaller than a maximum width at a portion more inside the notch portion than the opening portion.
1 . An antenna device, comprising:
a metal layer for forming an antenna element in a predetermined planar shape; and
a ground arranged on a lower side of the metal layer,
wherein the metal layer forms:
a first metal forming the planar shape,
a notch portion formed at the first metal, and cutting out a part of an edge of the planar shape,
a second metal being an electromagnetic field coupling element arranged with a predetermined distance spaced from the first metal inside the notch portion, and
a feeder line formed outside the planar shape, and to be connected with the second metal via an opening portion of the notch portion, and
for the second metal, a width at the opening portion is smaller than a maximum width at a portion more inside the notch portion than the opening portion,
wherein the second metal is a metal in a shape of a trapezoid in which a top side of the trapezoid is situated at a portion in a width direction of the opening portion.
2 . The antenna device according to claim 1 ,
wherein for the second metal, a width W1 (mm) at the opening portion satisfies an expression (1):
W 1≤0.0125×λ (1)
where λ(mm) represents a wavelength at a design frequency of the antenna element.
3 . The antenna device according to claim 1 ,
wherein for the second metal, a maximum width W2 (mm) at the portion more inside the notch portion than the opening portion satisfies an expression (2):
W 2≤0.125× (2)
where λ(mm) represents a wavelength at a design frequency of the antenna element.
4 . The antenna device according to claim 1 ,
wherein for the second metal, a length L2 (mm) from the opening portion to an opposite side to the opening portion satisfies an expression (3):
L 2≤0.0625×λ (3)
where λ(mm) represents a wavelength at a design frequency of the antenna element.
5 . The antenna device according to claim 1 ,
wherein the first metal has a slit at an edge of the planar shape.
6 . The antenna device according to claim 1 ,
wherein the first metal has a slit at a portion inside the planar shape.
7 . The antenna device according to claim 1 ,
wherein for the feeder line, a width of a portion to be connected with the second metal is constant or gradually thins toward the second metal.
8 . The antenna device according to claim 1 , further comprising a dielectric layer arranged between the metal layer and the ground.
9 . The antenna device according to claim 1 ,
wherein a matching circuit is provided in the feeder line.
10 . A wireless terminal comprising the antenna device according to claim 1 .