Antenna device having a capacitive loading element
An antenna device includes a case, a first antenna and a second antenna including a capacitance loading element. The capacitance loading element includes a turning-around area turning around in a front-rear direction on at least one of a front side and a rear side thereof. When the turning-around area is provided on the front side, at least part of the first antenna is situated in front of the turning-around area. When the turning-around area is provided on the rear side, at least part of the first antenna is situated behind the turning-around area. When the turning-around area is provided on the front side and on the rear side, at least part of the first antenna is situated at least one of in front of the turning-around area on the front side and behind the turning-around area on the rear side.
1. An antenna device comprising:
a case; and
a first antenna and a second antenna provided in the case, wherein
the second antenna includes a capacitance loading element,
the capacitance loading element includes a turning-around area turning around in a front-rear direction on at least one of a front side and a rear side thereof,
when the turning-around area is provided on the front side, at least part of a transmitting portion and/or a receiving portion of the first antenna is situated in front of the turning-around area of the capacitance loading element,
when the turning-around area is provided on the rear side, at least part of the transmitting portion and/or the receiving portion of the first antenna is situated behind the turning-around area of the capacitance loading element, and
when the turning-around area is provided on the front side and on the rear side, at least part of the transmitting portion and/or the receiving portion of the first antenna is situated at least one of in front of the turning-around area on the front side of the capacitance loading element and behind the turning-around area on the rear side of the capacitance loading element.
2. The antenna device according to claim 1 , wherein
in the capacitance loading element, a voltage maximum point of a standing wave generated therein in a frequency band of the first antenna is shifted from an end portion of the capacitance loading element on the side of the first antenna, by the turning-around area in the front-rear direction.
3. The antenna device according to claim 1 , wherein
in the capacitance loading element, an end portion of a current path of the capacitance loading element is shifted from an end portion of the capacitance loading element on the side of the first antenna, by the turning-around area in the front-rear direction.
4. The antenna device according to claim 1 , further comprising:
an inner case provided in the case, wherein
the capacitance loading element is held outside the inner case, and
the first antenna is held inside the inner case.
5. The antenna device according to claim 1 , further comprising:
an inner case provided in the case, wherein
the second antenna includes a helical element,
the capacitance loading element is held outside the inner case, and
the helical element is held inside the inner case.
6. The antenna device according to claim 5 , wherein
the helical element is situated below the capacitance loading element,
when the turning-around area is provided on the front side, the helical element is situated behind the first antenna,
when the turning-around area is provided on the rear side, the helical element is situated in front of the first antenna, and
when the turning-around area is provided on the front side and on the rear side, the helical element is situated at least one of behind the first antenna and in front of the first antenna.
7. The antenna device according to claim 1 , wherein
the capacitance loading element includes a turning-around area turning around in the front-rear direction from a starting point inside the capacitance loading element.
8. The antenna device according to claim 7 , further comprising:
an inner case provided in the case, wherein
the capacitance loading element is attached to an outside of the inner case through a connection portion provided adjacent to the starting point.
9. The antenna device according to claim 1 , wherein
an edge of the capacitance loading element facing a side of the first antenna is obliquely inclined when viewed from a direction vertical to a direction in which the first antenna and the second antenna are aligned and a top-bottom direction.
10. The antenna device according to claim 1 , wherein
the capacitance loading element has a turning-around area turning around in a top-bottom direction.
11. The antenna device according to claim 1 , wherein
a third antenna is provided on a side opposite to the side where the first antenna is provided with respect to the capacitance loading element, and
in the capacitance loading element, an area of the capacitance loading element on a side of the third antenna is partially extended to the side of the third antenna.
12. The antenna device according to claim 1 , further comprising:
an inner case provided in the case, wherein
the capacitance loading element includes a right plate-like portion and a left plate-like portion,
the right plate-like portion and the left plate-like portion are separate portions, and
the right plate-like portion and the left plate-like portion are held outside the inner case so that an upper end of the right plate-like portion and an upper end of the left plate-like portion are lower than an upper end of the inner case.
13. The antenna device according to claim 1 , wherein
the first antenna and the second antenna are aligned in a front-rear direction, and
the capacitance loading element is divided in a right-left direction into a first portion and a second portion, and at least parts of the first and second portions are coupled.
14. The antenna device according to claim 1 , wherein
the first antenna and the second antenna are aligned in a front-rear direction, and
in the first antenna, an area of a flat surface vertical to the front-rear direction is the largest.
15. The antenna device according to claim 1 , wherein the capacitance loading element including a right plate-like portion and a left plate-like portion that are separate portions.