Antenna device, communication device, and mobile body

Abstract

To provide a simply-structured antenna device, a communication apparatus and a mobile object, in which communication quality deterioration or communication interruption hardly occurs when being applied to communication between the mobile objects.SOLUTION: An antenna device comprises: a plurality of antennas 11 and 12 that respectively have directional characteristics including a plurality of second directional beams oriented in an opposite direction with respect to a side of first directional beams 111H and 121H and a communication target, and are arranged such that directions of the first directional beams are different from each other; and a reflection member 30 that has reflection surfaces 310 and 320 corresponding to the plurality of second directional beams. There may be included in a desired directional angular range: directions of the first directional beams; and directions of reflection directional beams 112HR and 122HR generated through reflection, on reflection surfaces of the reflection member, of the second directional beams. The reflection surfaces may respectively have incidence angles of the second directional beams of antennas corresponding to the reflection surfaces, the incidence angles being equal to each other, and further may have reflection coefficients of a specified value or more with respect to the second directional beams of antennas corresponding to the reflection surfaces.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to an antenna device, a communication device, and a moving body suitable for vehicle-to-vehicle communication.

Background Art

[0002] Conventionally, a communication device having an antenna device that can be mounted on a moving body such as a vehicle that performs inter-mobile body communication such as vehicle-to-vehicle communication is known. For example, in Cited Document 1, a communication device is provided on a first moving body (vehicle) that can move along a moving route, and performs inter-mobile body communication (vehicle-to-vehicle communication) with another second moving body (vehicle) when the first moving body moves along the moving route. According to this communication device, a directional beam toward the second moving body is formed by a directional antenna, and when the second moving body is predicted to be out of the range of the directional beam and communication disconnection is predicted, the tracking of the directional beam with respect to the second moving body is started, so that inter-mobile body communication can be continued even in lane changes on the moving route, right and left turns at intersections, curve driving, etc.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a conventional communication device that performs inter-mobile body communication such as vehicle-to-vehicle communication, an antenna device with a simple configuration in which communication quality deterioration and communication disconnection are less likely to occur when applied to inter-mobile body communication is desired.

Means for Solving the Problems

[0005] An antenna device according to one aspect of the present invention includes a plurality of antennas each having a directivity characteristic including a first directivity beam and a second directivity beam facing each other, and the directions of the first directivity beams are arranged so as to be different from each other, and a reflection member having a plurality of reflecting surfaces corresponding to the plurality of second directivity beams of the plurality of antennas. The directions of the plurality of first directivity beams of the plurality of antennas and the directions of the plurality of reflected directivity beams obtained by reflecting the plurality of second directivity beams by the plurality of reflecting surfaces of the reflection member are included in a desired directivity angle range.

[0006] In the antenna device, the plurality of reflecting surfaces of the reflection member may each have the same incident angle of the second directivity beam of the antenna corresponding to the reflecting surface.

[0007] In the antenna device, the plurality of reflecting surfaces of the reflection member may each have a reflection coefficient equal to or greater than a predetermined value with respect to the second directivity beam of the antenna corresponding to the reflecting surface.

[0008] In the antenna device, the distance between each of the plurality of reflecting surfaces of the reflection member and the antenna corresponding to the reflecting surface may be λ / 2π (λ: wavelength of radio wave) or more.

[0009] In the antenna device, when the number of antennas is n, and the desired directivity angle range and its adjustment value are α and Δα, respectively, the directions φn of the first directivity beam and the reflected directivity beam of each of the plurality of antennas may satisfy the following formula (1).

Equation

[0010] In the antenna device, for each of the plurality of reflecting surfaces of the reflection member, the inclination angle of the reflecting surface may be corrected so that the reflected directivity beam formed by the reflecting surface passes through a target point on a virtual concentric circle having a radius equal to the reception distance with the reference point of the antenna device as the center.

[0011] A communication device according to another aspect of the present invention includes the antenna device and a wireless communication unit connected to the antenna of the antenna device.

[0012] A moving body according to still another aspect of the present invention includes the communication device and performs inter-vehicle communication with another moving body located at least on one of the front and rear in the moving direction.

[0013] In the moving body, a plurality of the antenna devices may be provided at least on one of the front and rear in the moving direction of the moving body, and the same radio wave may be transmitted or received via the plurality of antenna devices.

[0014] In the antenna device, the communication device, and the moving body, the symmetric radio waves for transmission, reception, or both may be microwaves, millimeter waves, or sub-millimeter waves.

Advantages of the Invention

[0015] According to the present invention, it is possible to provide an antenna device with a simple configuration in which communication quality deterioration and communication interruption are less likely to occur when applied to inter-vehicle communication.

Brief Description of the Drawings

[0016]

Figure 1

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Figure 15

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Figure 18

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Figure 20

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The device according to the embodiment described in this document is an antenna device including a plurality of antennas suitable for inter-vehicle communication such as vehicle-to-vehicle communication, a communication device including the antenna device and a wireless communication unit, and a moving body including the communication device. The antenna device according to the embodiment has directivity characteristics including a first directivity beam and a second directivity beam facing each other, and includes a plurality of antennas arranged such that the directions of the first directivity beams are different from each other, and a reflecting member having a plurality of reflecting surfaces corresponding to the plurality of second directivity beams of the plurality of antennas. By doing so, it is possible to realize an antenna device with a simple configuration in which communication quality degradation and communication interruption are less likely to occur when applied to inter-vehicle communication. In particular, the antenna device of the present embodiment is an antenna device suitable for realizing vehicle-to-vehicle communication using fifth-generation or later-generation mobile communication.

[0018] In addition, in this embodiment, a case where the moving body is a vehicle traveling on a road which is a ground moving route will be described, but there are no particular restrictions on the type of the moving body and the type of the moving route. For example, the vehicle may be a car, a truck, a bus, a motorcycle, or the like. The vehicle may be a vehicle having an automatic driving function or a manually driven vehicle without an automatic driving function. Further, the moving body to be determined for the collision possibility may be, in addition to the ground vehicle, a moving body such as an aircraft capable of moving by flying on a moving route at a predetermined altitude. Further, the moving body may be an underground moving body moving on an underground moving route, a water moving body such as a ship capable of moving on a moving route on water (for example, on the sea), or an underwater moving body such as a submersible robot moving on an underwater moving route (for example, in the sea).

[0019] Further, the vehicle of this embodiment may be an electric vehicle, a fuel cell vehicle, or a hybrid vehicle having both an internal combustion engine and an electric motor. Further, when the vehicle has a plurality of seats for passengers or riders, the vehicle may be one in which the foremost and leftmost seat is not the driver's seat. That is, the vehicle may be one in which only the foremost and rightmost seat is the driver's seat, or may be an autonomous vehicle that does not have a driver's seat in the first place.

[0020] In addition, the configuration and communication method of the mobile communication network in this embodiment are not limited to those conforming to the standard specifications of a specific generation. The configuration and communication method of the mobile communication network in this embodiment may conform to the standard specifications of, for example, LTE, LTE-Advanced, the fifth generation, or subsequent generations.

[0021] FIG. 1(a) is a diagram showing an example of the horizontal plane directivity characteristic 100H of the antenna according to the reference example, and FIG. 1(b) is a diagram showing an example of the vertical plane directivity characteristic 100V of the same antenna. As an antenna for mobile communication such as vehicle-to-vehicle communication, ideally, an antenna having directivity in the vertical plane as shown by the directivity characteristic 100V in FIG. 1(b) and having completely non-directional in the horizontal plane as shown by the directivity characteristic 100H in FIG. 1(a) is desirable. However, an actual antenna for mobile communication has directivity in the horizontal plane as shown by the directivity characteristic 100H' in FIG. 2(a), and nulls 100N exist.

[0022] FIGS. 3(a) and 3(b) are explanatory diagrams of problems when a plurality of vehicles (mobile bodies) 41 and 42 each provided with an antenna device having beam directivity travel while performing vehicle-to-vehicle communication. In FIG. 3, the preceding vehicle 41 is provided with an antenna device having a rearward horizontal plane directivity characteristic 141HR and a lateral horizontal plane directivity characteristic 141HS with respect to the traveling direction. The following vehicle 42 is provided with an antenna device having a forward horizontal plane directivity characteristic 141HF with respect to the rear of travel.

[0023] On the straight road (travel route) shown in FIG. 3(a), vehicle-to-vehicle communication can be performed in a state where the rearward horizontal plane directivity characteristic 141HR of the preceding vehicle 41 and the forward horizontal plane directivity characteristic 141HF of the following vehicle 42 are substantially opposed, and deterioration of communication quality and disconnection are less likely to occur.

[0024] However, on the curved road (travel route) shown in FIG. 3(b), since the rearward horizontal plane directivity characteristic 141HR and the lateral horizontal plane directivity characteristic 141HS of the preceding vehicle 41 and the forward horizontal plane directivity characteristic 141HF of the following vehicle 42 are no longer opposed, deterioration of communication quality and disconnection of vehicle-to-vehicle communication may occur. In particular, when traveling on a curve or the like with a large inter-vehicle distance while performing vehicle-to-vehicle communication, if the gain decreases at the null of the horizontal plane directivity of the antenna, communication quality deterioration and disconnection are likely to occur.

[0025] As one of the countermeasures against the above-mentioned communication quality degradation and disconnection, beam tracking can be considered as in the above-mentioned Patent Document 1, but a device for controlling the beam is required.

[0026] In the present embodiment, by combining a plurality of antennas having directivity in the front-rear direction in the horizontal plane and a reflecting member having a predetermined reflecting surface described later, an antenna device 100 with a simple configuration in which communication quality degradation and communication disconnection are less likely to occur when applied to vehicle-to-vehicle communication (communication between moving bodies) is provided.

[0027] FIGS. 4(a) and 4(b) are diagrams each showing an example of the horizontal plane directivity characteristics 111H, 112H, 121H, 122H of a plurality of antennas 11, 12 constituting the antenna device of the embodiment. The antenna 11 in FIG. 4(a) is, for example, a half-wavelength dipole antenna and has a directivity characteristic including a first directivity beam 111H and a second directivity beam 112H facing each other in opposite directions. Similarly, the antenna 12 in FIG. 4(b) is, for example, a half-wavelength dipole antenna and has a directivity characteristic including a first directivity beam 121H and a second directivity beam 122H facing each other in opposite directions. Note that the illustrated example is an example in the case where the number of antennas is two, but the antenna device may include three antennas, four antennas, or five or more antennas (the same applies in the following embodiments).

[0028] FIG. 5 is an explanatory diagram of an antenna device 100' including a reflecting member 30' according to a reference example. In FIG. 5, the angle φ0 in the reference direction is 0°, and the desired directivity angle range (desired radiation range) α is 90°. The plurality of antennas 11, 12 of the antenna device 100' are arranged such that the directions (φ1, φ2) of the first directivity beams 111H, 121H facing the direction of the communication target side (hereinafter also referred to as the "front direction") are different from each other by a predetermined angle (2α / 3). In the example of FIG. 5, the angle φ1 in the direction of the first directivity beam 111H of the antenna 11 is minus 10° with respect to the reference direction (10° counterclockwise in the figure), and the angle φ2 in the direction of the first directivity beam 121H of the antenna 12 is plus 50° with respect to the reference direction (50° clockwise in the figure).

[0029] Also, in FIG. 5, on the side opposite to the communication targets of the plurality of antennas 11 and 12, a reflecting member 30' having a single reflecting surface 300 is arranged. By the reflecting surface 300 of the reflecting member 30', a second directivity beam 112H facing the direction opposite to the communication target side of the antenna 11 (hereinafter also referred to as the "rear direction") is reflected, and a reflected directivity beam 112HR is formed in a predetermined direction φ1' = φ1 + α (in the illustrated example, φ1' = 80°) in the forward direction. The angular difference Δφ1 between the direction φ1 of the first directivity beam 111H of the antenna 11 and the direction φ1' of the reflected directivity beam 112HR is 90° (= α). Also, by the reflecting surface 300 of the reflecting member 30', a second directivity beam 122H facing the rear direction of the antenna 12 is reflected, and a reflected directivity beam 122HR is formed in a predetermined direction φ2' = φ1 + α / 3 (in the illustrated example, φ2' = 20°) in the forward direction. The angular difference Δφ2 between the direction φ2 of the first directivity beam 121H of the antenna 12 and the direction φ2' of the reflected directivity beam 122HR is 30°.

[0030] In FIG. 5, the distance between the reflecting surface 300 of the reflecting member 30' and each of the antennas 11 and 12 may be λ / 2π (λ: wavelength of the radio wave) or more where the position of the reflecting surface 300 is in the far field as viewed from each antenna. For example, when the frequency of the radio wave is 29 GHz, since the wavelength λ of the radio wave is 1 cm, the distance between the reflecting surface 300 of the reflecting member 30' and each of the antennas 11 and 12 may be set to 1.6 mm or more. Here, for example, if the distance d2 between the antennas 11 and 12 and the receiving antenna is 15 m and the distance d1 between the antennas 11 and 12 and the reflecting surface 300 of the reflecting member 30' is 5 cm, the radius r of the first Fresnel zone on the reflecting surface 300 calculated by the following formula (2) f becomes 2.3 cm. Therefore, in order to reduce the loss by allowing the first Fresnel zone to enter the reflecting surface 300, a reflecting member (reflecting plate) 30' having a reflecting surface 300 of 4.6 cm square or more may be used.

Equation

[0031] In the antenna device 100' of FIG. 5, the reflection directivity beams 112HR and 122HR formed by the reflection member 30' can interpolate the nulls in the horizontal plane directivity characteristics of the antenna device 100'. However, in the case of a single reflecting surface 300, when radio waves of the second directivity beams 112H and 122H in the backward direction are incident on the reflecting surface 300 of the reflection member 30' from each of the plurality of antennas 11 and 12, the incident angles are different from each other. When the incident angles are different in this way, the reflection coefficient may decrease significantly as shown in the reflection characteristics of the vertical polarization in FIG. 6(a) and the reflection characteristics of the horizontal polarization in FIG. 6(b). Therefore, depending on the arrangement of the antennas, the reflection coefficient at the reflecting surface 300 of the reflection member 30' becomes small, the reflection efficiency deteriorates, and the communication quality may deteriorate.

[0032] Therefore, in the antenna device of the embodiment, by using a reflection member (reflector) having a plurality of reflecting surfaces, a desired directivity angle range (desired angle range) α is covered, and the incident angles of radio waves from each of the plurality (n) of antennas are the same (Δφ1 / 2 = Δφ2 / 2 = ··· = Δφn / 2) and a desired reflection coefficient (for example, 0.4 or more) can be obtained. Thereby, the nulls in the horizontal plane directivity characteristics can be interpolated, and by making the reflection efficiencies of all the antennas the same, deterioration of the communication quality can be suppressed.

[0033] In the antenna device of the embodiment, the plurality (n) of reflecting surfaces of the reflection member may each have a distance of λ / 2π (λ: wavelength of radio wave) or more from the antenna corresponding to the reflecting surface.

[0034] Also, in the antenna device of the embodiment, when the desired directivity angle range (desired angle range) and its adjustment value are α and Δα, respectively, the directions φn of the first directivity beams and the reflection directivity beams of each of the plurality (n) of antennas may satisfy the following formula (3).

Equation

[0035] Further, in the antenna device of the embodiment, for each of the plurality (n) of reflecting surfaces of the reflecting member, the inclination angle of the reflecting surface may be corrected so that the reflection directivity beam formed by the reflecting surface passes through a target point on a virtual concentric circle having a radius equal to the reception distance with the reference point of the antenna device as the center.

[0036] FIG. 7 is a diagram showing an antenna device 100 including a reflecting member 30 according to the first embodiment and an example of a directivity beam. FIG. 8 is a diagram showing an example of a vehicle 42 including the antenna device 100 of FIG. 7. The antenna device 100 of the present embodiment includes two antennas 11 and 12 and a reflecting member 30, and is attached to the front end (for example, the stay member at the right end) in the moving direction of the vehicle 42.

[0037] In FIG. 7, the two antennas 11 and 12 each have a directivity characteristic including first directivity beams 111H and 121H and second directivity beams 112H and 122H that are opposite to each other (see FIGS. 4(a) and 4(b)). The reflecting member 30 of the present embodiment is a multi-plane reflector having a reflecting surface 310 corresponding to the second directivity beam 112H of the antenna 11 and a reflecting surface 320 corresponding to the second directivity beam 122H of the antenna 12.

[0038] The directions of the first directivity beams 111H and 121H of the two antennas 11 and 12 and the directions of the two reflection directivity beams 112HR and 122HR obtained by reflecting the second directivity beams 112H and 122H by the two reflecting surfaces 310 and 320 of the reflecting member 30 are included in a desired directivity angle range (desired angle range) α or an adjustment range α + Δα thereof.

[0039] In the present embodiment, the desired directivity angle range (desired angle range) α is covered by the four directivity beams, namely, the first directivity beams 111H and 121H and the reflection directivity beams 112HR and 122HR, and the desired radiation range α may be adjusted by Δα so that the incident angles of radio waves from each of the antennas 11 and 12 are the same (Δφ1 / 2 = Δφ2 / 2) and a desired reflection coefficient (for example, 0.4 or more) is obtained.

[0040] Further, in order to reduce losses, the reflecting member 30 of the present embodiment may be a multi-plane reflector in which a plurality of reflecting surfaces 310 and 320 having an area equal to or greater than the range of the first Fresnel zone are combined at a distance of λ / 2π or more (a distance in the far-field) from each of the antennas 11 and 12. When allowing losses, the area of each of the reflecting surfaces 310 and 320 of the reflecting member 30 does not necessarily have to be equal to or greater than the range of the first Fresnel zone.

[0041] Also, in the antenna device 100 of the present embodiment, the directions φ1, φ1' of the first directive beam 111 and the reflected directive beam 112HR of the antenna 11 and the directions φ2, φ2' of the first directive beam 121 and the reflected directive beam 122HR of the antenna 12 may be directions that satisfy the following equations (4) to (7) so as to equally interpolate the nulls in the desired directivity angle range (desired angle range) α+Δα for each beam.

Equation

[0042] According to the antenna device 100 of FIGS. 7 and 8, it is possible to interpolate the nulls in the horizontal plane directivity characteristics, and by making the reflection efficiencies of all the antennas 11 and 12 the same, it is possible to suppress the deterioration of the communication quality.

[0043] FIG. 9 is a diagram showing an example of an antenna device 100 including a reflecting member 30 according to the second embodiment and a directive beam. FIG. 10 is a diagram showing an example of a vehicle 42 including the antenna device 100 of FIG. 9. The antenna device 100 of the present embodiment includes three antennas 11, 12, and 13 and a reflecting member 30, and is attached to the front end (for example, the stay member at the right end) in the moving direction of the vehicle 42.

[0044] In FIG. 9, the three antennas 11, 12, and 13 each have a directivity characteristic including first directivity beams 111H, 121H, 131H and second directivity beams 112H, 122H, 132H that are opposite to each other (see FIGS. 4(a) and 4(b)). The reflecting member 30 of the present embodiment is a multi-plane reflector having a reflecting surface 310 corresponding to the second directivity beam 112H of the antenna 11, a reflecting surface 320 corresponding to the second directivity beam 122H of the antenna 12, and a reflecting surface 330 corresponding to the second directivity beam 132H of the antenna 13.

[0045] The directions of the first directivity beams 111H, 121H, 131H of the three antennas 11, 12, 13 and the directions of the three reflected directivity beams 112HR, 122HR, 132HR obtained by reflecting the second directivity beams 112H, 122H, 132H by the three reflecting surfaces 310, 320, 330 of the reflecting member 30 are included in a desired directivity angle range (desired angle range) α or its adjustment range α + Δα.

[0046] In the present embodiment, the desired directivity angle range (desired angle range) α is covered by the six directivity beams, i.e., the first directivity beams 111H, 121H, 131H and the reflected directivity beams 112HR, 122HR, 132HR, and the desired radiation range α may be adjusted by Δα so that the incident angles of the radio waves from each of the antennas 11, 12, 13 are the same (Δφ1 / 2 = Δφ2 / 2 = Δφ3 / 2) and a desired reflection coefficient (for example, 0.4 or more) can be obtained.

[0047] Further, in order to reduce loss, the reflecting member 30 of the present embodiment may be a multi-plane reflector in which a plurality of reflecting surfaces 310, 320, 330 having an area equal to or larger than the range of the first Fresnel zone are combined at a distance of λ / 2π or more (a distance in the far-field region) from each of the antennas 11, 12, 13. When loss is allowed, the area of each of the reflecting surfaces 310, 320, 330 of the reflecting member 30 does not have to be equal to or larger than the range of the first Fresnel zone.

[0048] Further, in the antenna device 100 of the present embodiment, the directions φ1, φ1' of the first directivity beam 111 and the reflected directivity beam 112HR of the antenna 11, the directions φ2, φ2' of the first directivity beam 121 and the reflected directivity beam 122HR of the antenna 12, and the directions φ3, φ3' of the first directivity beam 131 and the reflected directivity beam 132HR of the antenna 13 may be directions that satisfy the following equations (8) to (13) so as to equally interpolate the nulls in the desired directivity angle range (desired angle range) α + Δα with each beam.

Equation

[0049] According to the antenna device 100 of FIGS. 9 and 10, it is possible to interpolate the nulls in the horizontal plane directivity characteristics, and by making the reflection efficiencies of all the antennas 11, 12, and 13 the same, it is possible to suppress the deterioration of communication quality.

[0050] FIG. 11 is a diagram showing an example of the positional relationship among the antennas 11 and 12 and the reflecting member 30 in the ray tracing simulation of the antenna device 100 according to the embodiment. FIG. 12 is a graph showing an example of the result of the ray tracing simulation of FIG. 11. In the computer ray tracing simulation of this example, in the antenna device 100 including the two antennas 11 and 12 shown in FIG. 7 described above, when the directivity angle range (desired angle range) α + Δα is 90°, for each azimuth angle from the reference point of the antenna device 100, the relative received power [dB] on a concentric circle where the distance (received distance) r from the reference point of the antenna device 100 is 10 m was calculated. The directions φ1, φ1' of the first directivity beam 111 and the reflected directivity beam 112HR of the antenna 11 and the directions φ2, φ2' of the first directivity beam 121 and the reflected directivity beam 122HR of the antenna 12 were set to directions that satisfy the above-described equations (4) to (7). As a result, as shown in FIG. 12, it can be seen that the nulls in the desired directivity angle range (desired angle range) α + Δα can be equally interpolated with the beams 111H, 122HR, 112HR, and 121H having different directions by 30° each.

[0051] FIG. 13 is a diagram showing another example of the positional relationship among antennas 11 and 12 and a reflecting member 30 in the ray tracing simulation of the antenna device 100 according to the embodiment. FIG. 14 is a graph showing an example of the result of the ray tracing simulation of FIG. 13. In the computer ray tracing simulation of this example, in the antenna device 100 including the two antennas 11 and 12 shown in FIG. 7 described above, when the directivity angle range (desired angle range) α+Δα is 120°, for each azimuth angle from the reference point of the antenna device 100, the relative received power [dB] on a concentric circle where the distance (received distance) r from the reference point of the antenna device 100 is 10 m was calculated. The directions φ1, φ1' of the first directivity beam 111 and the reflected directivity beam 112HR of the antenna 11 and the directions φ2, φ2' of the first directivity beam 121 and the reflected directivity beam 122HR of the antenna 12 were set to directions that satisfy the above-described formulas (4) to (7). As a result, as shown in FIG. 14, it can be seen that the nulls in the desired directivity angle range (desired angle range) α+Δα can be evenly interpolated by the beams 111H, 122HR, 112HR, and 121H each having a different orientation by 40°.

[0052] Note that the level of the symbol Pth in FIG. 14 is the allowable degradation value (3 dB in the illustrated example) with respect to the maximum gain of the antenna device 100. The number of antennas in the antenna device 100 of the present embodiment may be set so that the received power with respect to the maximum gain of the antenna device 100 satisfies (does not fall below) the allowable degradation value Pth.

[0053] FIG. 15 is a diagram showing an example of the positional relationship among the origin P0, the reflection point P1, and the reception point P3 within the desired directivity angle range (desired angle range) in the ray tracing simulation of the antenna device 100 according to the embodiment. FIG. 16 is an explanatory diagram of the correction angle β in the ray tracing simulation of FIG. 15. The reception point P3 is a point on a concentric circle that is separated from the origin P0 of the antenna device 100 by a predetermined reception distance (distance to the target reception position) r. The aforementioned desired directivity angle range (desired angle range) is considered in terms of reflection at the origin P0. That is, in FIG. 15, the inclination angles of the respective reflecting surfaces 310, 320 of the reflecting member 30 are set such that the point where the second directivity beam 122H facing the rear of the antenna 12 is reflected at the origin P0 and reaches the concentric circle at the reception distance r coincides with the reception point P2. However, since the reflection point P1 on the reflecting surface 310 is different from the origin P0, the direction of the reflected directivity beam 122HR where the second directivity beam 122H facing the rear of the antenna 12 is reflected at the actual reflection point P1 is shifted by an angle β. Therefore, the inclination angles of the respective reflecting surfaces 310, 320 of the reflecting member 30 may be corrected according to the reception distance r.

[0054] For example, the correction angle β in FIG. 16 is calculated by the following equation (14) based on the reception distance r, and as shown in FIG. 17, the inclination of each of the reflecting surfaces 310, 320 of the reflecting member 30 is corrected by the correction angle β. Here, n in equation (14) is the number of antennas.

Equation

[0055] FIG. 18 is a graph showing an example of the result of a ray tracing simulation of the antenna device 100 before correcting the tilt angles of the reflecting surfaces 310 and 320 using the correction angle β. FIG. 19 is a graph showing an example of the result of a ray tracing simulation of the antenna device 100 after correcting the tilt angles of the reflecting surfaces 310 and 320 using the correction angle β. In the computer ray tracing simulation of this example, in the antenna device 100 including the two antennas 11 and 12 shown in FIG. 7 above, when the directivity angle range (desired angle range) α + Δα is 90°, for each azimuth angle from the reference point of the antenna device 100, the relative received power [dB] on a concentric circle where the distance (received distance) r from the reference point of the antenna device 100 is 2 m was calculated. In the result before correction in FIG. 18, the azimuth angles (45°) of the reflected directivity beams 112HR of the antenna 11 and the azimuth angles (25°) of the reflected directivity beams 122HR of the antenna 12 are shifted. On the other hand, in the result after correction in FIG. 19, the shift in the azimuth angles of the reflected directivity beams 112HR and the reflected directivity beams 122HR is corrected, and it can be seen that the nulls in the desired directivity angle range (desired angle range) α + Δα can be evenly interpolated among the beams 111H, 122HR, 112HR, and 121H with different orientations by 30° each.

[0056] Note that when the received distance r is separated by a certain distance (for example, when it is separated by 10 m or more), the correction angle β becomes sufficiently small, so the correction of the tilt angle of the reflecting surface using the correction angle β may not be performed.

[0057] FIG. 20 is a perspective view showing an example of the configuration of an antenna device 100 including a reflecting member 30 according to an embodiment. The antenna device 100 includes two antennas 11 and 12 and a reflecting member 30 having two reflecting surfaces 310 and 320. The reflecting member 30 is a two-plane reflector having a reflecting surface 310 corresponding to the antenna 11 and a reflecting surface 320 corresponding to the antenna 12. The distance D1 between the antenna 11 and the reflecting surface 310 and the distance D2 between the antenna 12 and the reflecting surface 320 are each set to be λ / 2π or more. Thereby, the range Z1 of the first Fresnel zone on the reflecting surface 310 with respect to the antenna 11 has an area smaller than the entire area of the reflecting surface 310 and is located inside the reflecting surface 310, and the range Z2 of the first Fresnel zone on the reflecting surface 320 with respect to the antenna 12 has an area smaller than the entire area of the reflecting surface 320 and is located inside the reflecting surface 320. Thereby, the loss due to the reflecting surfaces 310 and 320 can be reduced.

[0058] The antenna device 100 of the embodiment can be attached, for example, to a stay member for attaching an auxiliary mirror located on an outer frame located on a side portion of a front glass of a vehicle (large vehicle) as a moving body. Further, in order to obtain a diversity effect of the antenna in vehicle-to-vehicle communication, a plurality (for example, two sets) of antenna devices 100 may be attached to the stay member. Further, a moving body such as a vehicle including the antenna device 100 of the embodiment and a communication device having a wireless communication unit may perform vehicle-to-vehicle communication with another moving body such as a vehicle located at least one of the front and the rear in the moving direction of the moving body. The antenna device of the moving body may have a predetermined gain within a desired directivity angle range (for example, an angle range of 90 degrees or more and 120 degrees or less) in the horizontal plane in vehicle-to-vehicle communication with another moving body. Further, a moving body such as a vehicle may include a plurality of antenna devices at least one of the front and the rear in the moving direction of the moving body, and may transmit or receive the same radio wave via the plurality of antenna devices, for example, to obtain a diversity effect.

[0059] As described above, according to the present embodiment, it is possible to provide an antenna device 100 with a simple configuration that is less likely to cause communication quality degradation or communication interruption when applied to inter-mobile body communication such as vehicle-to-vehicle communication.

[0060] In addition, since the present invention can provide inter-mobile body communication such as vehicle-to-vehicle communication in which communication quality degradation and communication interruption are less likely to occur over a long period of time, it can contribute to the achievement of Sustainable Development Goal (SDG) 9, "Build the infrastructure for industry and innovation."

[0061] Also, the description of the embodiments disclosed in this specification is provided to enable those skilled in the art to manufacture or use the present disclosure. Various modifications to the present disclosure will be readily apparent to those skilled in the art, and the general principles defined in this specification can be applied to other variations without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure should not be limited to the examples and designs described in this specification, but should be recognized in the broadest scope consistent with the principles and novel features disclosed in this specification.

Description of Reference Numerals

[0062] 11, 12, 13: Antenna 30: Reflective member 41, 42: Vehicle 100: Antenna device 310, 320, 330: Reflective surface

Claims

1. An antenna device, comprising: a plurality of antennas each having a directivity characteristic including a first directivity beam and a second directivity beam in opposite directions, and arranged such that the directions of the first directivity beams are different from each other; a reflecting member having a plurality of reflecting surfaces corresponding to the plurality of second directivity beams of the plurality of antennas; an antenna device, wherein the directions of the plurality of first directivity beams of the plurality of antennas and the directions of the plurality of reflected directivity beams obtained by reflecting the plurality of second directivity beams by the plurality of reflecting surfaces of the reflecting member are included in a desired directivity angle range.

2. The antenna device according to Claim 1, wherein the plurality of reflecting surfaces of the reflecting member each have the same incident angle of the second directivity beam of the antenna corresponding to the reflecting surface. Antenna device.

3. The antenna device according to Claim 2, wherein the plurality of reflecting surfaces of the reflecting member each have a reflection coefficient of a predetermined value or more with respect to the second directivity beam of the antenna corresponding to the reflecting surface. Antenna device.

4. The antenna device according to Claim 1, wherein the distance between each of the plurality of reflecting surfaces of the reflecting member and the corresponding antenna is λ / 2π (λ: wavelength of radio wave) or more. Antenna device.

5. The antenna device according to Claim 1, wherein when the number of the antennas is n, and the desired directivity angle range and its adjustment value are α and Δα, respectively, the directions φn of the first directivity beam and the reflected directivity beam of each of the plurality of antennas satisfy the following formula (1). Antenna device. 【Equation 1】

6. The antenna device according to Claim 1, For each of the plurality of reflecting surfaces of the reflecting member, the inclination angle of the reflecting surface is corrected so that the reflection directivity beam formed by the reflecting surface passes through a target point on a virtual concentric circle having a radius equal to the reception distance and centered on the origin of the desired directivity angle of the antenna device. Antenna device. **Claim 7** An antenna device according to any one of claims 1 to 6, and A wireless communication unit connected to the antenna of the antenna device, and A communication device comprising the same. **Claim 8** A moving body that includes the communication device of claim 7 and performs vehicle-to-vehicle communication with another moving body located at least on one of the front and rear in the moving direction. **Claim 9** In the moving body of claim 8, A plurality of the antenna devices are provided at least on one of the front and rear in the moving direction of the moving body, and The same radio wave is transmitted or received via the plurality of antenna devices. Moving body.

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