Antenna device and communication device equipped therewith
An antenna device includes a base body, a flat plate-like radiating element placed in the base body, a flat plate-like ground electrode arranged substantially parallel to the radiating element, and high-dielectric layers placed on side surfaces of the base body, the dielectric constants of the high-dielectric layers being higher than that of the base body. At least part of one of the high-dielectric layers is located between the radiating element and the ground electrode when seen from an X-axis direction that is the normal direction of the side surfaces and is located outside the ground electrode when seen from a Z-axis direction that is the normal direction of a top surface.
1 . An antenna device comprising:
a base body having a top surface, a bottom surface, and a plurality of side surfaces that connect the top surface and the bottom surface, the top surface and the bottom surface having polygonal shapes, the top surface facing the bottom surface;
a first radiating element placed in the base body, the first radiating element having a plate-like shape and being arranged substantially parallel to the top surface;
a ground electrode placed at a position that is closer to the bottom surface than the first radiating element, the ground electrode having a plate-like shape and being arranged substantially parallel to the first radiating element; and
a first high-dielectric portion whose dielectric constant is higher than that of the base body, wherein
at least part of the first high-dielectric portion:
is located between the first radiating element and the ground electrode when the first high-dielectric portion is seen from a first direction that is a normal direction of a side surface of the plurality of side surfaces on which the first high-dielectric portion is placed,
is located outside the ground electrode when the first high-dielectric portion is seen from a second direction that is a normal direction of the top surface,
the first high-dielectric portion is placed on each of a first side surface and a second side surface of the plurality of side surfaces, and
a bottom surface of the first high-dielectric portion placed on each of the first side surface and the second side surface is higher than a bottom surface of the base body.
2 . The antenna device according to claim 1 , wherein
at least part of the first high-dielectric portion is located at an area that overlaps the first radiating element when the first high-dielectric portion is seen from the first direction.
3 . The antenna device according to claim 2 , wherein
at least part of the first high-dielectric portion extends from the area that overlaps the first radiating element to an area that overlaps the ground electrode when the first high-dielectric portion is seen from the first direction.
4 . The antenna device according to claim 1 , wherein
the first side surface and the second side surface face one another.
5 . The antenna device according to claim 1 , wherein
the top surface has a rectangular shape having a shorter side and a longer side,
the first side surface and the second side surface face one another with the shorter side interposed therebetween, and
the plurality of side surfaces include a third side surface and a fourth side surface that face one another with the longer side interposed therebetween, and
the first high-dielectric portion:
is not placed on either the third side surface or the fourth side surface.
6 . The antenna device according to claim 1 , further comprising:
a second high-dielectric portion placed on the top surface, a dielectric constant of the second high-dielectric portion being higher than that of the base body.
7 . The antenna device according to claim 6 , wherein
the second high-dielectric portion is in contact with the first high-dielectric portion.
8 . The antenna device according to claim 1 , wherein
the first radiating element has a feed point placed at a position shifted in the first direction from a center of a plane of the first radiating element.
9 . The antenna device according to claim 8 , wherein
the first radiating element has:
a first feed point placed at a position shifted in the first direction from the center of the plane of the first radiating element, and
a second feed point placed at a position shifted in a direction orthogonal to the first direction from the center of the plane of the first radiating element.
10 . The antenna device according to claim 1 , further comprising:
a second radiating element placed between the first radiating element and the ground electrode, the second radiating element having a plate-like shape and being arranged substantially parallel to the first radiating element and the ground electrode.
11 . The antenna device according to claim 10 , wherein
at least part of the first high-dielectric portion is located between the first radiating element and the second radiating element and between the second radiating element and the ground electrode when the first high-dielectric portion is seen from the first direction.
12 . The antenna device according to claim 1 , wherein
a shortest distance in the first direction from an end part of the first radiating element to an end part of the ground electrode is less than 0.8 times a dimension of the first radiating element in the first direction.
13 . The antenna device according to claim 1 , further comprising:
a third radiating element placed in the base body, the third radiating element being arranged in such a way that the third radiating element and the first radiating element are lined up in a direction orthogonal to the first direction and the second direction.
14 . A communication device equipped with the antenna device according to claim 1 .
15 . The antenna device according to claim 1 , wherein the first high-dielectric portion is embedded into the first side surface and the second side surface, at least in part.
16 . The antenna device according to claim 1 , wherein the base body is formed of a low temperature co-fired ceramic (LTCC).
17 . The antenna device according to claim 1 , wherein the base body is formed of a liquid crystal polymer (LCP).
18 . The antenna device according to claim 1 , wherein the base body includes a multilayer structure.
19 . The antenna device according to claim 18 , wherein each layer of the multilayer structure is formed of polyethylene terephthalate (PET).
20 . The antenna device according to claim 1 , wherein a size of the ground electrode is larger than a size of the first radiating element.