Antenna device
An antenna device ( 100 ) for a vehicle includes an antenna case ( 101 ), an antenna base ( 102 ) forming an accommodation space together with the antenna case ( 101 ), a first antenna element ( 108 ) that is accommodated in the accommodation space and that at least transmits or receives a circularly polarized wave; a second antenna element ( 110 ) that is arranged close to the first antenna element ( 108 ) and that at least transmits or receives a linearly polarized wave; and at least one parasitic element ( 111 ), ( 112 a ), ( 112 b ), or ( 112 c ) serving as a reflector or a waveguide for the second antenna element ( 110 ).
1 . An antenna device comprising:
a case;
a base forming an accommodation space together with the case;
a first antenna element that is accommodated in the accommodation space and that at least transmits or receives a circularly polarized wave;
a second antenna element that is arranged close to the first antenna element and that at least transmits or receives a linearly polarized wave; and
at least two parasitic elements serving as a reflector or a waveguide for the second antenna element, wherein
the at least two parasitic elements include at least one first parasitic element and at least one second parasitic element,
the at least one first parasitic element is arranged on a side opposite to the first antenna element with the second antenna element interposed therebetween and functions as a waveguide for the second antenna element, and
the at least one second parasitic element is arranged between the first antenna element and the second antenna element and functions as a reflector for the second antenna element.
2 . The antenna device according to claim 1 , wherein at least one parasitic element among the at least two parasitic elements is arranged within a range of ½ of a wavelength of the linearly polarized wave from an installation position of the second antenna element.
3 . The antenna device according to claim 1 , wherein a number of the at least one second parasitic element is greater than a number of the at least one first parasitic element.
4 . The antenna device according to claim 1 , wherein at least one parasitic element among the at least two parasitic elements includes a bent or curved portion.
5 . The antenna device according to claim 1 , wherein at least one parasitic element among the at least two parasitic elements is a linear conductor.
6 . The antenna device according to claim 1 , further comprising:
a resin holder configured to hold at least one parasitic element among the at least two parasitic elements.
7 . An antenna device comprising:
a case;
a base forming an accommodation space together with the case;
a first antenna element that is accommodated in the accommodation space and that at least transmits or receives a circularly polarized wave;
a second antenna element that is arranged close to the first antenna element and that at least transmits or receives a linearly polarized wave; and
at least one parasitic element serving as a reflector or a waveguide for the second antenna element,
wherein a length of the at least one parasitic element is ½ or less of a wavelength of the circularly polarized wave when ungrounded, and ¼ or less of the wavelength of the circularly polarized wave when grounded.
8 . The antenna device according to claim 7 , wherein the at least one parasitic element is arranged between the first antenna element and the second antenna element.
9 . The antenna device according to claim 7 , wherein the at least one parasitic element is arranged within a range of ½ of a wavelength of the linearly polarized wave from an installation position of the second antenna element.
10 . The antenna device according to claim 7 , wherein the length of the at least one parasitic element is 3/10 or less of the wavelength of the circularly polarized wave when ungrounded, and 3/20 or less of the wavelength of the circularly polarized wave when grounded.
11 . The antenna device according to claim 7 , wherein the at least one parasitic element includes a bent or curved portion.
12 . The antenna device according to claim 7 , wherein the at least one parasitic element is a linear conductor.
13 . The antenna device according to claim 7 , further comprising:
a resin holder configured to hold the at least one parasitic element.
14 . An antenna device comprising:
a case;
a base forming an accommodation space together with the case;
a first antenna element that is accommodated in the accommodation space and that at least transmits or receives a circularly polarized wave;
a second antenna element that is arranged close to the first antenna element and that at least transmits or receives a linearly polarized wave; and
at least one parasitic element serving as a reflector or a waveguide for the second antenna element,
wherein the at least one parasitic element is a linear conductor and includes a bent or curved portion.
15 . The antenna device according to claim 14 , wherein the at least one parasitic element is arranged between the first antenna element and the second antenna element.
16 . The antenna device according to claim 14 , wherein the at least one parasitic element is arranged within a range of ½ of a wavelength of the linearly polarized wave from an installation position of the second antenna element.
17 . The antenna device according to claim 14 , further comprising:
a resin holder configured to hold the at least one parasitic element.