Patch antenna and antenna device for vehicle

1. A patch antenna comprising:

an antenna main body having a dielectric body, a radiating element having a flat-plate shape provided on a first surface of the dielectric body, and a ground plate provided on a second surface of the dielectric body opposite to the first surface of the dielectric body in a first direction perpendicular to a plate surface of the radiating element;

a parasitic element provided at a position on the first surface of the dielectric body and spaced away from the radiating element in planar view in which the radiating element is seen from the first direction; and

a protrusion that extends along the first direction,

wherein the antenna main body has a first outer surface closer to the radiating element than to the ground plate and a second outer surface opposite to the first outer surface along the first direction, the second outer surface being closer to the ground plate than to the radiating element, and

wherein the protrusion is configured to directly contact the second outer surface of the antenna main body.

2. The patch antenna according to claim 1 , wherein a longitudinal direction of the parasitic element is oriented along a direction of a line segment connecting a center of the radiating element and a feeding point in the planar view.

3. The patch antenna according to claim 1 , wherein a longitudinal length of the parasitic element is 0.52 times or more than a maximum length of the radiating element in the planar view.

4. The patch antenna according to claim 1 , wherein a longitudinal length of the parasitic element is 0.89 times or less than a maximum length of the radiating element in the planar view.

5. The patch antenna according to claim 1 , wherein a difference between a height Hp of a top face of the parasitic element and a height Hr of a top face of the radiating element satisfies 0≤Hp−Hr<α×0.05, where α is a maximum length of the radiating element in the planar view.

6. The patch antenna according to claim 1 , wherein a pair of the parasitic elements is provided on opposite sides of the radiating element.

7. The patch antenna according to claim 6 , wherein the pair of parasitic elements includes a first parasitic element, and a second parasitic element which length in a longitudinal direction is longer than the first parasitic element.

8. An antenna device for a vehicle equipped with the patch antenna according to claim 1 , the antenna device for the vehicle comprising:

a housing installed in a predetermined orientation at a predetermined position of the vehicle; and

a support adapted to support the patch antenna such that the patch antenna is used for vertically polarized waves when the housing is installed in the predetermined orientation at the predetermined position.

9. The patch antenna according to claim 3 , wherein a longitudinal length of the parasitic element is 0.89 times or less than a maximum length of the radiating element in the planar view.

10. The patch antenna according to claim 9 , wherein a difference between a height Hp of a top face of the parasitic element and a height Hr of a top face of the radiating element satisfies 0≤Hp−Hr<α×0.05, where α is a maximum length of the radiating element in the planar view.

11. The patch antenna according to claim 5 , wherein a pair of the parasitic elements is provided on opposite sides of the radiating element.

12. The patch antenna according to claim 6 , wherein the pair of the parasitic element has the same length in a longitudinal direction.

13. The patch antenna according to claim 1 , wherein the protrusion is conductive.

14. The patch antenna according to claim 1 , wherein the protrusion overlaps spacing between the radiating element and the parasitic element in the planar view.

15. The patch antenna according to claim 1 , further comprising a housing forming an accommodation space in which the antenna main body and the parasitic element are accommodated,

wherein the protrusion is configured to contact an inner surface of the housing.

16. The patch antenna according to claim 15 , wherein

a pair of the parasitic elements is provided on opposite sides of the radiating element, the pair of parasitic elements includes a first parasitic element and a second parasitic element having a length in a longitudinal direction longer than a length of the first parasitic element.

17. The patch antenna according to claim 1 , wherein the parasitic element is spaced away from the radiating element between 0.25 to 0.51 times a maximum length of the radiating element in the planar view.

18. The patch antenna according to claim 1 , wherein the second outer surface of the antenna main body is a surface of the ground plate opposite to the dielectric body along the first direction.

19. A patch antenna comprising:

an antenna main body having a dielectric body, a radiating element having a flat-plate shape provided on a first surface of the dielectric body, and a ground plate provided on a second surface of the dielectric body opposite to the first surface of the dielectric body in a first direction perpendicular to a plate surface of the radiating element;

a parasitic element provided at a position spaced away from the radiating element in planar view in which the radiating element is seen from the first direction;

a protrusion that extends along the first direction; and

a housing, wherein

the antenna main body has a first outer surface closer to the radiating element than to the ground plate and a second outer surface opposite to the first outer surface along the first direction, the second outer surface being closer to the ground plate than to the radiating element,

the protrusion is configured to directly contact the second outer surface of the antenna main body, and

the parasitic element is provided on an inner surface of the housing.

20. A patch antenna comprising:

an antenna main body having a dielectric body, a radiating element having a flat-plate shape provided on a first surface of the dielectric body, and a ground plate provided on a second surface of the dielectric body opposite to the first surface of the dielectric body in a first direction perpendicular to a plate surface of the radiating element;

a parasitic element provided at a position on the first surface of the dielectric body and spaced away from the radiating element in planar view in which the radiating element is seen from the first direction; and

a protrusion that extends along the first direction,

wherein the antenna main body has a first side closer to the radiating element than to the ground plate and a second side opposite to the first side along the first direction, the second side being closer to the ground plate than to the radiating element, and

wherein the protrusion is made of resin, and is configured to contact the second side of the antenna main body.