Antenna module and vehicle

Abstract

This antenna module comprises an antenna that is mounted on a mounting surface, and a plate-shaped artificial magnetic conductor that is disposed adjacent to the antenna and that has a first surface on which a plurality of first unit cells are regularly arranged. The artificial magnetic conductor has a base end portion adjacent to the antenna, and the first surface extends along the mounting surface from the base end portion.

Description

[Technical Field]

[0001] The present disclosure relates to an antenna module and a vehicle. This application claims priority to Japanese Application No. 2022-001041, filed January 6, 2022, and incorporates by reference all of the contents of said Japanese application. [Background technology]

[0002] Patent Document 1 discloses an antenna for a mobile communication system that is mounted on a moving object such as a vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020-189033 Summary of the Invention

[0004] (1) An embodiment of an antenna module comprises an antenna mounted on a mounting surface, and a plate-shaped artificial magnetic conductor arranged adjacent to the antenna and having a first surface on which a plurality of first unit cells are regularly arranged, wherein the artificial magnetic conductor has a base end adjacent to the antenna, and the first surface extends from the base end along the mounting surface.

[0005] (9) A vehicle according to another embodiment of the present invention comprises a vehicle body, an antenna mounted on the upper surface of the vehicle body, and a plate-shaped artificial magnetic conductor mounted on the upper surface adjacent to the antenna and having a first surface on which a plurality of first unit cells are regularly arranged, wherein the artificial magnetic conductor has a base end adjacent to the antenna, and the first surface extends from the base end along the upper surface. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a perspective view showing an example of an antenna module according to the first embodiment. [Figure 2] FIG. 2 is a plan view of an artificial magnetic conductor. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a diagram showing an antenna substrate according to the second embodiment. [Figure 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6A] FIG. 6A is a perspective view showing an antenna module according to a modified example. [Figure 6B] FIG. 6B is a perspective view showing an antenna module according to another modified example. [Figure 7A] FIG. 7A is a perspective view showing the model used in the verification test. [Figure 7B] FIG. 7B is a view of the model used in the verification test as viewed along the Y direction. [Figure 8] Figure 8 is an enlarged view of the top surface of the artificial magnetic conductor. [Figure 9] FIG. 9 is a perspective view showing a model provided with an electromagnetic bandgap structure. [Figure 10] FIG. 10 is a diagram showing the directivity patterns of the first, second, and third embodiments. [Figure 11] FIG. 11 is a diagram showing the directivity patterns of the fourth, fifth, and sixth embodiments. [Figure 12] FIG. 12 is a diagram showing a directivity pattern of a comparative example. [Figure 13] FIG. 13 is a diagram for explaining the relationship between the antenna and the roof. DETAILED DESCRIPTION OF THE INVENTION

[0007] [Problem to be solved by this disclosure] The antenna is sometimes mounted on the roof of a vehicle, and receives radio waves from surrounding base stations and emits radio waves toward the base station. In this case, a partial drop may occur in the direction of a relatively low elevation angle in the directivity pattern of vertically polarized waves.

[0008] Base stations are installed at heights of 10 meters or more. For this reason, the antennas mounted on vehicles must radiate radio waves over an elevation angle range of several degrees to approximately 60 degrees. Therefore, partial dips in the directivity pattern that occur in directions with relatively low elevation angles can lead to a decrease in communication sensitivity with the base station. Therefore, it is necessary to suppress such partial drops in the directivity pattern of vertically polarized waves as much as possible.

[0009] [Effects of this disclosure] According to the present disclosure, it is possible to suppress partial drops in the directivity pattern of vertically polarized waves.

[0010] [Description of the embodiments of the present disclosure] First, the contents of the embodiment will be listed and explained. [Outline of the embodiment] The partial drop in the directivity pattern of vertically polarized waves mentioned above is thought to be due to the influence of the vehicle roof. FIG. 13 is a diagram for explaining the relationship between the antenna and the roof. 13, antenna 100 is mounted on roof 102. Antenna 100 has patch antenna element 104. Patch antenna element 104 is installed facing obliquely upward at a predetermined elevation angle.

[0011] If the roof 102 is made of a conductive material such as a steel plate, when radio waves are emitted from the patch antenna element 104, a component (radiated wave) due to the radiation path is generated as well as a component (reflected wave) due to the reflection path. The radio waves (transmitted waves) that are radiated into space and received by the base station are a composite component (composite wave) of the radiated wave and the reflected wave.

[0012] Here, the phase of the reflected wave is inverted at the reflection point in the reflection path. Depending on the radiation angle, the radiated wave and reflected wave of the transmitted wave from patch antenna element 104 may have opposite phases due to the path length difference between the radiation path and the reflected path and the phase inversion described above, and the radiated wave and reflected wave may cancel each other out. As a result, partial attenuation occurs in the direction of a particular elevation angle, and it is conceivable that a partial drop occurs in the directivity pattern of the vertically polarized waves of the antenna 100.

[0013] (1) In contrast, an embodiment of an antenna module includes an antenna mounted on a mounting surface, and a plate-shaped artificial magnetic conductor arranged adjacent to the antenna and having a first surface on which a plurality of first unit cells are regularly arranged. The artificial magnetic conductor has a base end adjacent to the antenna, and the first surface extends from the base end along the mounting surface.

[0014] The artificial magnetic conductor has the reflection characteristics of a perfect magnetic conductor for incident waves within a specific frequency band. In other words, if the frequency of the radio waves radiated from the antenna is within the specific frequency band, the phase of the reflected wave generated when the radio waves radiated from the antenna are reflected by the first surface of the artificial magnetic conductor will not be inverted. In other words, phase inversion at the reflection point in the reflection path is suppressed. Therefore, according to the above configuration, by providing an artificial magnetic conductor adjacent to the antenna, it is possible to prevent the reflected wave from the reflection path with a point adjacent to the antenna as the reflection point from being out of phase with the radiated wave. As a result, partial attenuation of the radio wave radiated from the antenna is suppressed, and partial drops occurring in the directivity pattern of the vertically polarized wave at the antenna can be suppressed.

[0015] (2) Furthermore, in the antenna module of (1) above, when the artificial magnetic conductor includes a first ground conductor layer and a first dielectric layer interposed between the plurality of first unit cells and the first ground conductor layer, it is preferable that the electrical length from the boundary between the plurality of first unit cells and the first dielectric layer to the boundary between the first ground conductor layer and the first dielectric layer is 0.03 or more. In this case, the first unit cells can be made smaller without changing the specific frequency band in which the artificial magnetic conductor has the reflection characteristics of a perfect magnetic conductor, and the first unit cells can be arranged at a higher density.

[0016] (3) Furthermore, in the antenna module of (1) or (2) above, when the artificial magnetic conductor has an outer end opposite the base end and the first surface extends from the base end to the outer end, it is preferable that the ratio of the distance from the base end to the outer end to the vacuum wavelength of the radio waves emitted from the antenna is 1 or more. In this case, the distance from the base end to the outer end can be set to at least one wavelength of the radio wave radiated from the antenna, which allows the range of the artificial magnetic conductor to be appropriately set with respect to the reflection point of the reflection path when the radio wave is radiated from the antenna, and more effectively suppresses partial drops that occur in the directivity pattern of vertically polarized waves.

[0017] (4) Furthermore, in the antenna module of (1) or (2) above, when the artificial magnetic conductor has an outer end opposite the base end and the first surface extends from the base end to the outer end, it is preferable that the distance from the base end to the outer end is 10.7 mm or more. In this case too, the range of the artificial magnetic conductor can be appropriately set relative to the reflection point of the reflection path when radio waves are emitted from the antenna, and partial drops that occur in the directional pattern of vertically polarized waves can be more effectively suppressed.

[0018] (5) In any one of the antenna modules (1) to (4) above, when the antenna includes one or more patch antenna elements, it is preferable that, when the first surface is viewed in a plane, a virtual vertical line extending from the radiation surface of the one or more patch antenna elements passes through the first surface. In this case, the artificial magnetic conductor can be placed in a position corresponding to the radiation direction of the radio waves emitted by one or more patch antenna elements. Therefore, the position of the artificial magnetic conductor can be appropriately set with respect to the reflection point of the reflection path. This makes it possible to suppress partial drops in the directivity pattern of vertically polarized waves in the radiation direction.

[0019] (6) In the antenna module of (5) above, the antenna may further include a second ground conductor layer, a second dielectric layer interposed between the one or more patch antenna elements and the second ground conductor layer, and an electromagnetic bandgap structure arranged to surround the one or more patch antenna elements. In this case, by configuring the shielding band of the electromagnetic bandgap structure to include the frequency of the radio waves emitted from the antenna, it is possible to more effectively suppress partial drops that occur in the directional pattern of vertically polarized waves.

[0020] (7) In the antenna module of any one of (1) to (6) above, it is preferable that the frequency of the radio waves transmitted and received by the antenna is 20 GHz or higher. In this case, the artificial magnetic conductor can effectively suppress phase inversion at the reflection point.

[0021] (8) In the antenna module of any one of (1) to (7) above, the mounting surface may be a roof surface of a vehicle. The roof of a vehicle is generally made of a conductive material such as a steel plate. Therefore, by providing an artificial magnetic conductor covering the roof, it is possible to effectively suppress phase inversion at the reflection point in the reflection path. As a result, partial attenuation of the radio waves radiated from the antenna is suppressed, and partial drops that occur in the directivity pattern of vertically polarized waves at the antenna can be suppressed.

[0022] (9) A vehicle according to another embodiment of the present invention comprises a vehicle body, an antenna mounted on the upper surface of the vehicle body, and a plate-shaped artificial magnetic conductor mounted on the upper surface adjacent to the antenna and having a first surface on which a plurality of first unit cells are regularly arranged, wherein the artificial magnetic conductor has a base end adjacent to the antenna, and the first surface extends from the base end along the upper surface. The above configuration also makes it possible to suppress partial drops that occur in the directivity pattern of vertically polarized waves in the antenna.

[0023] (10) In the vehicle of (9) above, the artificial magnetic conductor may be a separate body separated from the antenna. In this case as well, it is possible to suppress the partial drop that occurs in the directivity pattern of vertically polarized waves in the antenna.

[0024] [Details of the embodiment] Preferred embodiments will now be described with reference to the drawings. At least some of the embodiments described below may be combined in any manner. [Regarding the first embodiment] FIG. 1 is a perspective view showing an example of an antenna module according to the first embodiment. The antenna module 1 is an antenna module used in, for example, a mobile terminal of a fifth generation mobile communication system. 1, the X, Y, and Z directions are perpendicular to each other, and the Z direction is parallel to the vertical direction, so the XY plane is a horizontal plane.

[0025] The antenna module 1 is mounted on the upper surface of a vehicle (vehicle body) for use. The upper surface of a vehicle includes the roof surface (ceiling surface), as well as the upper surface of the trunk, the upper surface of the hood, and the like. In FIG. 1, the antenna module 1 is shown mounted on the roof surface R of a vehicle. The antenna module 1 has the function of transmitting and receiving radio waves from a base station outside the vehicle. The antenna module 1 is used to establish a communication connection between a communication device mounted on the vehicle and a mobile terminal inside the vehicle and the base station. Vehicles on which the antenna module 1 is mounted include passenger cars, buses, railroad cars, and the like.

[0026] The antenna module 1 includes a base substrate 2, an antenna 4, and a plurality of artificial magnetic conductors 6. The base substrate 2 is a rectangular substrate mounted on the roof surface R of the vehicle, and has the antenna 4 and multiple artificial magnetic conductors 6 attached to it. The base substrate 2 is a mounting member for mounting the antenna 4 upright on the roof surface R of the vehicle.

[0027] The antenna 4 is erected on the roof surface R, which is the mounting surface. The antenna 4 includes a plurality of (four in the illustrated example) antenna substrates 10. Each of the four antenna substrates 10 has a plurality of (four in the illustrated example) patch antenna elements 12. The four antenna substrates 10 are erected and fixed to the base substrate 2 along the four sides of the base substrate 2. The four antenna substrates 10 are arranged so that the four patch antenna elements 12 on each substrate face outward. Here, "outward" refers to a direction away from the center S of the base substrate 2, and "inward" refers to a direction approaching the center S of the base substrate 2.

[0028] The four patch antenna elements 12 of each of the four antenna substrates 10 are arranged at equal intervals along the horizontal direction. The four patch antenna elements 12 form an array antenna. Therefore, each antenna substrate 10 is capable of horizontal beamforming directed outward. For example, each antenna substrate 10 can change the direction of the beam within a range of approximately 100 degrees in the azimuth direction. Each antenna substrate 10 is responsible for beamforming by dividing the entire circumference in the azimuth direction into four equal parts. This allows the antenna 4 to direct beams all around the circumference in the azimuth direction. Furthermore, each antenna substrate 10 is inclined with respect to the base substrate 2 so that the front direction of the plurality of patch antenna elements 12 faces diagonally upward. The azimuthal direction is the direction of rotation around an axis parallel to the Z direction (vertical direction).

[0029] In the fifth generation mobile communication system, radio waves in the frequency band of 3 to 10 GHz, quasi-millimeter waves in the frequency band of 27 to 30 GHz, or millimeter waves in a higher frequency band are used. More specifically, the radio waves emitted from the antenna substrate 10 are preferably 3 GHz or higher, more preferably 5 GHz or higher, and even more preferably 20 GHz or higher. The upper limit of the frequency of the radio waves emitted from the antenna substrate 10 is not particularly limited, but is, for example, 300 GHz, preferably 200 GHz, more preferably 100 GHz, and even more preferably 50 GHz.

[0030] The multiple (four in the illustrated example) artificial magnetic conductors 6 are rectangular plate-shaped members. The four artificial magnetic conductors 6 are provided along the four sides of the base substrate 2. Therefore, the four artificial magnetic conductors 6 are provided from the base end 4a of the antenna 4 to the periphery of the antenna 4. The four artificial magnetic conductors 6 are arranged adjacent to the antenna 4. The four artificial magnetic conductors 6 extend in a direction away from the antenna 4. More specifically, the four artificial magnetic conductors 6 extend outward from the base ends 10a of the four antenna substrates 10. The base ends 10a of the antenna substrates 10 constitute the base ends 4a of the antenna 4. The base ends 6a of the four artificial magnetic conductors 6 are connected to the base ends 10a of the four antenna substrates 10. Therefore, the four artificial magnetic conductors 6 and the four antenna substrates 10 are provided integrally. Note that the four artificial magnetic conductors 6 and the four antenna substrates 10 may be integral or separate. The four artificial magnetic conductors 6 are mounted on the roof surface R. The four artificial magnetic conductors 6 are arranged so as to cover the periphery of the antenna 4 on the roof surface R. More specifically, the four artificial magnetic conductors 6 are arranged so as to cover the area outside the base ends 10a of the four antenna substrates 10. The four artificial magnetic conductors 6 extend from the antenna 4 along the radiation direction of the antenna 4, as will be described later. The base end 4a of the antenna 4 refers to the root portion of the antenna 4 when the antenna 4 is erected against the roof surface R, which is the installation surface, or a surface facing in the same direction as the roof surface R. More specifically, the base end 4a of the antenna 4 refers to the root portion of the antenna substrate 10 when the antenna substrate 10 is erected against the upper surface of the artificial magnetic conductor 6 or the roof surface R, or the portion where the plane along the radiation surface of the patch antenna element 12 of the antenna substrate 10 intersects with the upper surface of the artificial magnetic conductor 6 or the roof surface R.

[0031] The four artificial magnetic conductors 6 (hereinafter referred to as AMC6) are components configured as so-called metamaterials. A metamaterial is a structure made up of a regular arrangement of multiple components, and has electromagnetic properties that cannot be realized with conventional materials. The AMC6 has the reflection characteristics of a perfect magnetic conductor with respect to radio waves incident on the AMC6 from space. When the frequency of the incident wave is within a specific frequency band, the AMC6 has the reflection characteristics of a substantially perfect magnetic conductor. Therefore, when radio waves within a specific frequency band are incident on the AMC 6, the phase of the incident wave and the phase of the reflected wave are substantially the same. Hereinafter, in this specification, the term "specific frequency band" refers to a frequency band of an incident wave in which AMC6 functions as a substantially perfect magnetic conductor.

[0032] 1 is exposed to the outside, the AMC 6 may be covered with a cover made of resin, etc. In this case, the AMC 6 is protected from the external environment.

[0033] Fig. 2 is a plan view of the AMC 6, and Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2. Note that Fig. 3 shows a cross section of the antenna substrate 10 in addition to the cross section of the AMC 6.

[0034] As shown in FIGS. 2 and 3, the AMC 6 includes a plurality of first unit cells 20, a first ground conductor layer 22, a first dielectric layer 24, and a plurality of first vias 26. The first dielectric layer 24 is interposed between the plurality of first unit cells 20 and the first ground conductor layer 22. The first dielectric layer 24 is a rectangular dielectric substrate. The plurality of first unit cells 20 are provided on an upper surface 24a of the first dielectric layer 24. The first ground conductor layer 22 is provided on a lower surface 24b of the first dielectric layer 24.

[0035] The first ground conductor layer 22 is a plate-shaped member made of a conductor such as copper, etc. The first ground conductor layer 22 is provided over almost the entire area of ​​the lower surface 24b. The plurality of first unit cells 20 are plate-shaped members made of a conductor such as copper, etc. The outer shape of the first unit cells 20 is hexagonal when viewed from the Z direction. 2, the plurality of first unit cells 20 are regularly arranged on the upper surface 24a. The plurality of first unit cells 20 are arranged with gaps g1 between them. The gaps g1 are preferably uniform. The plurality of first unit cells 20 are provided over the entire upper surface 24a. Therefore, the first surface 6c of the AMC6 is configured to include the upper surface 24a of the first dielectric layer 24 and the plurality of first unit cells 20. In other words, the plurality of first unit cells 20 are regularly arranged on the first surface 6c. The AMC6 is disposed on the roof surface R. Therefore, the first surface 6c faces upward, just like the roof surface R. Furthermore, the first surface 6c extends from the base end 6a of the artificial magnetic conductor 6 (the base end 10a of the antenna substrate 10) along the roof surface R. Here, being regularly arranged means that there is regularity in the positional relationship and gaps between the multiple first unit cells 20, and refers to a state in which the first unit cells 20 are aligned with a certain gap as described above.

[0036] The AMC 6 has the base end 6a and outer edge 6b (outer end) described above. The base end 6a is a side or edge adjacent to the antenna 4 (antenna substrate 10). The outer edge 6b is an edge (or side) opposite the base end 6a. The base end 6a is connected to the base end 10a of the antenna substrate 10 as described above. The first surface 6c extends from the base end 6a of the AMC 6 to the outer edge 6b. In addition, the base end 6a being adjacent to the antenna 4 includes not only the case where the base end 6a is in direct contact with and connected to the antenna substrate 10, but also the case where the base end 6a is connected to the antenna substrate 10 via a bent portion 16, as described below, or the case where the base end 6a is not directly or indirectly connected but is positioned close to the antenna substrate 10 within a range where it can be connected to the antenna substrate 10 via a bent portion 16 or the like.

[0037] The outer shape of the first unit cell 20 is preferably a regular hexagon, but may also be a square or other polygon. When the outer shape of the first unit cell 20 is a regular hexagon, the first unit cells 20 can be arranged at a higher density than when the outer shape is a square. Furthermore, the outer shape of the first unit cell 20 may include curved portions or uneven shapes.

[0038] The multiple first vias 26 are columnar members made of a conductor such as copper. Each of the multiple first vias 26 connects the first unit cell 20 and the first ground conductor layer 22. Therefore, the first vias 26 penetrate between the upper surface 24a and the lower surface 24b of the first dielectric layer 24. The first vias 26 may be provided as through holes. A structure having a plurality of first unit cells 20 and a plurality of first vias 26 as shown in FIGS. 2 and 3 is called a mushroom structure.

[0039] As described above, the AMC 6 functions as a perfect magnetic conductor when the frequency of the incident wave incident on the first surface 6c is within a specific frequency band. Therefore, in this case, if the frequency of the radio wave radiated from the antenna substrate 10 (antenna 4) is within the specific frequency band, the phase of the reflected wave generated when the radio wave radiated from the patch antenna element 12 is reflected by the artificial magnetic conductor is not inverted. Therefore, the specific frequency band of the AMC 6 in this embodiment is set to include the frequency of the radio waves emitted from the antenna substrate 10.

[0040] As shown in FIG. 3, the antenna substrate 10 includes four patch antenna elements 12, a second ground conductor layer 30, and a second dielectric layer 32. The second dielectric layer 32 is interposed between the four patch antenna elements 12 and the second ground conductor layer 30. The second dielectric layer 32 is a rectangular dielectric substrate. The four patch antenna elements 12 are provided on a second surface 32a of the second dielectric layer 32. The second ground conductor layer 30 is provided on a third surface 32b of the second dielectric layer 32. The third surface 32b is the surface opposite to the second surface 32a.

[0041] The second ground conductor layer 30 is a plate-shaped member made of a conductor such as copper, etc. The second ground conductor layer 30 is provided over almost the entire area of ​​the third surface 32b. The patch antenna element 12 is a plate-shaped member made of a conductor such as copper, etc. In other words, the patch antenna element 12 is a planar antenna element. The patch antenna element 12 has a feed point (not shown) for horizontal polarization and a feed point (not shown) for vertical polarization. A signal is supplied to both feed points from the outside via a via (not shown) that penetrates the second dielectric layer 32 and the second ground conductor layer 30, for example. When a signal is applied to the feed point for vertical polarization, the patch antenna element 12 radiates radio waves having vertical polarization. When a signal is applied to the feed point for horizontal polarization, the patch antenna element 12 radiates radio waves having horizontal polarization.

[0042] As described above, the antenna substrate 10 is provided on the base substrate 2 in a state inclined with respect to the Z direction so that the patch antenna element 12 faces diagonally upward. An imaginary vertical line B extending from the radiation surface 12a of the patch antenna element 12 passes through the AMC6. Each of the imaginary vertical lines B extending from the radiation surfaces of the four patch antenna elements 12 passes through the AMC6. In other words, as shown in FIG. 2, when the first surface 6c of the AMC6 is viewed in plan, the imaginary vertical line B passes through the first surface 6c. The imaginary vertical line B indicates the radiation direction of the radio waves emitted from the radiation surface 12a. Therefore, the AMC6 extends along the radiation direction of the patch antenna element 12.

[0043] 3, an imaginary vertical line B extending in the radiation direction from the radiation surface 12a of the patch antenna element 12 is inclined at an angle θ with respect to the horizontal plane. In other words, the angle θ indicates the elevation angle of the radiation direction of the patch antenna element 12 (the angle with respect to the horizontal plane). The antenna module 1 of this embodiment is intended to transmit and receive radio waves to and from base stations located at elevation angles in the range of 3 to 60 degrees. Therefore, the angle θ is preferably 15 degrees or more and 50 degrees or less, and more preferably 25 degrees or more and 35 degrees or less. The angle θ in the patch antenna element 12 of this embodiment is, for example, 30 degrees.

[0044] The antenna substrate 10 and the AMC 6 are connected via a bent portion 16 . The bent portion 16 connects the base end portion 10 a of the antenna substrate 10 and the base end portion 6 a of the artificial magnetic conductor 6 . In this embodiment, the first dielectric layer 24, the first ground conductor layer 22, the second dielectric layer 32, and the second ground conductor layer 30 are formed by bending a single dielectric substrate on which a ground conductor layer is formed. Therefore, the first dielectric layer 24 and the second dielectric layer 32 are connected to each other. Furthermore, the first ground conductor layer 22 and the second ground conductor layer 30 are connected to each other.

[0045] The artificial magnetic conductor 6 and the antenna substrate 10 can be formed using a rigid substrate or a flexible substrate. When the artificial magnetic conductor 6 and the antenna substrate 10 are integrally formed using a flexible substrate, the flexibility of the artificial magnetic conductor 6 and the antenna substrate 10 can be increased. In addition, it becomes easier to form the bent portion 16. The first dielectric layer 24 and the second dielectric layer 32 are formed using polyimide, liquid crystal polymer, PPE resin, fluororesin, or the like.

[0046] Here, when radio waves are emitted from the patch antenna element 12 of the antenna substrate 10, as described above, components due to the radiation path (radiated waves) as well as components due to the reflection path (reflected waves) are generated. The radio waves emitted into space and received by the base station are components (composite waves) that are a combination of the radiation wave and the reflected wave. The phase of the reflected wave is inverted at the reflection point in the reflection path, so that the radiated wave and the reflected wave in the transmission wave radiated from the patch antenna element 12 may cancel each other out. As a result, partial attenuation occurs in the direction of a specific elevation angle, causing a partial drop in the directivity pattern of vertically polarized waves on the antenna substrate 10.

[0047] In this embodiment, as described above, there is no phase inversion of the reflected wave generated when the radio wave radiated from the antenna substrate 10 is reflected by the first surface 6c of the AMC 6. In other words, phase inversion at the reflection point in the reflection path is suppressed. Therefore, with the above configuration, by providing the AMC 6 adjacent to the periphery of the antenna 4, it is possible to prevent the reflected wave from being out of phase with the radiated wave due to the reflection path having the points around the antenna 4 as reflection points. As a result, partial attenuation of the radio wave (transmitted wave) radiated from the antenna substrate 10 is suppressed, and partial drops occurring in the directivity pattern of the vertically polarized wave on the antenna substrate 10 can be suppressed.

[0048] Furthermore, in this embodiment, as described above, when the first surface 6c of the AMC6 is viewed in a planar view, the imaginary vertical line B extending in the radiation direction from the radiation surface 12a of the patch antenna element 12 passes through the first surface 6c of the AMC6. Therefore, the AMC 6 can be placed at a position corresponding to the radiation direction of the radio waves emitted by the patch antenna element 12. Therefore, the position of the AMC 6 can be appropriately set with respect to the reflection point of the reflection path. As a result, it is possible to suppress partial drops that occur in the directivity pattern of vertically polarized waves in the radiation direction.

[0049] Here, it is preferable to appropriately set the dimension from the base end 6a to the outer edge 6b of the AMC 6 so that the position of the reflection point of the reflection path when radio waves are emitted from the antenna substrate 10 is included in the range of the AMC. The outer edge 6b of the AMC 6 is also the outer edge of the first surface 6c. In FIG. 2, the ratio P of the distance L from the base end 6a of the AMC 6 (base end 10a of the antenna substrate 10) to the outer edge 6b of the AMC 6 (first surface 6c) to the vacuum wavelength λ0 is preferably 1 or greater. In this case, the distance L from the base end 6a to the outer edge 6b can be set to be equal to or greater than one wavelength of the radio wave radiated from the antenna substrate 10. This makes it possible to appropriately set the range of the AMC6 with respect to the reflection point of the reflection path when the radio wave is radiated from the antenna substrate 10, and more effectively suppress partial drops that occur in the directivity pattern of the vertically polarized wave in the patch antenna element 12.

[0050] Moreover, the ratio P is more preferably 1.5 or more, and even more preferably 1.8 or more. This makes it possible to more effectively suppress the partial drop in the directivity of patch antenna element 12. The ratio P is expressed by the following formula (1).

[0051] Proportion P = distance L / λ0 (1)

[0052] The distance L is the distance from the base end 6a of the AMC 6 (the base end 10a of the antenna substrate 10) to the outer edge 6b of the AMC 6. The vacuum wavelength λ0 is determined according to the wavelength of the radio waves emitted from the antenna substrate 10 (antenna 4). For example, when the frequency of the radio wave radiated from the antenna substrate 10 is 28 GHz, the vacuum wavelength λ0 is 10.7 mm, and the distance L is 10.7 mm, the proportion P is 1. Therefore, when the frequency of the radio waves emitted from the antenna substrate 10 is 28 GHz, the distance L is preferably 10.7 mm or more. Furthermore, when the frequency of the radio waves emitted from the antenna substrate 10 is 28 GHz, the distance L is more preferably 16 mm or more, and even more preferably 19 mm or more. The upper limit of the ratio P is not particularly limited, but is preferably, for example, 20 or less, and more preferably 10 or less. Furthermore, when the frequency of the radio waves emitted from the antenna substrate 10 is 28 GHz, the upper limit of the distance L is preferably 214 mm or less, and more preferably 107 mm or less.

[0053] Furthermore, it is preferable that the thickness t1 of the first dielectric layer 24, i.e., the electrical length from the boundary between the plurality of first unit cells 20 and the first dielectric layer 24 to the boundary between the first ground conductor layer 22 and the first dielectric layer 24, is 0.03 or more. In this case, it is possible to make the plurality of first unit cells 20 smaller without changing the specific frequency band of the AMC 6, and the plurality of first unit cells 20 can be arranged at a higher density. The lower limit of the electrical length from the plurality of first unit cells 20 to the first ground conductor layer 22 is preferably 0.05, more preferably 0.1, and even more preferably 0.15.

[0054] The upper limit of the electrical length between the plurality of first unit cells 20 and the first ground conductor layer 22 is preferably 1, more preferably 0.7, even more preferably 0.5, even more preferably 0.3, and even more preferably 0.2. The electrical length is preferably selected within a range that is equal to or less than one upper limit selected from the plurality of upper limit values ​​described above and equal to or greater than one lower limit selected from the plurality of lower limit values ​​described above.

[0055] Here, the electrical length is defined by the thickness (physical length) t1 of the first dielectric layer 24, the vacuum wavelength λ0, and the relative dielectric constant εr. The electrical length is expressed by the following formula (2).

[0056] Electrical length = (t1 / λ0)×(εr) 1 / 2 ···(2)

[0057] For example, when the frequency of the radio waves radiated from the antenna substrate 10 is 28 GHz, the vacuum wavelength λ0 is 10.7 mm, the thickness t1 of the first dielectric layer 24 is 0.5 mm, and the relative dielectric constant εr of the first dielectric layer 24 is 3.7, the electrical length from the plurality of first unit cells 20 to the first ground conductor layer 22 is 0.899. In this case, the electrical length is 0.03 or more.

[0058] Therefore, when the frequency of the radio waves radiated from the antenna substrate 10 is 28 GHz and the relative dielectric constant εr of the first dielectric layer 24 is 3.7, it is preferable that the thickness t1 of the first dielectric layer 24 is 0.17 mm or more. In this case, the electrical length is 0.03 mm or more.

[0059] The specific frequency band is determined by the structure of the AMC 6. The length of the diagonal of the first unit cell 20 (diameter of the circumscribed circle), the gap g1, the diameter of the first via 26, etc. are appropriately adjusted in consideration of the thickness t1 of the first dielectric layer 24 and the relative dielectric constant so that the specific frequency band includes the frequency of the radio waves radiated from the antenna substrate 10.

[0060] [Regarding the second embodiment] FIG. 4 is a diagram showing an antenna substrate 10 according to the second embodiment, and FIG. 5 is a cross-sectional view taken along line VV in FIG. The antenna module 1 of this embodiment differs from the first embodiment in that an electromagnetic bandgap structure 40 is provided on the antenna substrate 10.

[0061] 4 and 5, the electromagnetic bandgap structure 40 is provided so as to surround the four patch antenna elements 12. Electromagnetic bandgap structure 40(E l The Electromagnetic Band Gap Structure (hereinafter also referred to as the EBG structure 40) includes a plurality of second unit cells 42 and a plurality of second vias 44. The second unit cells 42 are provided on the second surface 32a of the second dielectric layer 32. The second unit cells 42 are plate-shaped members made of a conductor such as copper. The outer shape of the second unit cells 42 is hexagonal when viewed from the front. As shown in Figure 4, multiple Second unit cell 42 are regularly arranged on the second surface 32a. The second unit cells 42 are arranged with gaps g2 between them. The gaps g2 are preferably uniform.

[0062] The outer shape of the second unit cell 42 is preferably a regular hexagon, but may also be a square or other polygon. When the outer shape of the second unit cell 42 is a regular hexagon, the second unit cells 42 can be arranged at a higher density than when the outer shape is a square. Furthermore, the outer shape of the second unit cell 42 may include curved portions or uneven shapes.

[0063] The second vias 44 are columnar members made of a conductor such as copper. Each of the second vias 44 connects the second unit cell 42 and the second ground conductor layer 30. Thus, the second vias 44 penetrate between the second surface 32a and the third surface 32b of the second dielectric layer 32. The second vias 44 may be provided as through holes.

[0064] This EBG structure 40 also has a mushroom structure, similar to AMC6. The EBG structure 40 has the property of blocking radio waves in a certain frequency band. That is, the EBG structure 40 has a frequency band (blocking band) in which it can block radio waves. The shielding band of the EBG structure 40 of this embodiment is set to include the frequency of the radio waves emitted from the antenna substrate 10. Therefore, the specific frequency band of the AMC 6 and the shielding band of the EBG structure 40 both include the frequency of the radio waves emitted from the antenna substrate 10.

[0065] The antenna surface 10b of the antenna substrate 10 is provided with areas 46 where the plurality of second unit cells 42 are not arranged. The non-placement region 46 refers to a region on the antenna surface 10b that is created by not placing the second unit cells 42 in places where the second unit cells 42 should be placed. The non-placement region 46 in FIG. 4 is created by not placing seven unit cells 42. Therefore, on the antenna surface 10b, the non-placement region 46 is outside the placement range of the EBG structure 40. The four patch antenna elements 12 are arranged in the non-arrangement area 46. As a result, the EBG structure 40 surrounds the entire periphery of each of the four patch antenna elements 12. As a result, the EBG structure 40 is provided between the four patch antenna elements 12.

[0066] In a planar antenna such as a patch antenna, a surface wave mode occurs, in which radio waves radiated from the patch antenna element 12 propagate along the ground. In this embodiment, the shielding band of the EBG structure 40 includes the frequency of the radio waves radiated from the antenna 4, so the EBG structure 40 suppresses the propagation of the surface waves radiated from the four patch antenna elements 12. Furthermore, by providing the EBG structure 40 to the antenna substrate 10, partial drops occurring in the directivity pattern of vertically polarized waves in the patch antenna element 12 can be more effectively suppressed.

[0067] In addition, the thickness t2 of the second dielectric layer 32, i.e., Second unit cell 42 from Second ground conductor layer 30 It is preferable that the electrical length between the terminals is 0.03 or more. In this case, the plurality of second unit cells 42 can be made smaller without changing the shielding band of the EBG structure 40, and the plurality of second unit cells 42 can be arranged at a higher density.

[0068] [Other Modifications] In each of the above embodiments, an example has been given in which four rectangular plate-shaped AMC6s are used. However, for example, as shown in FIG. 6A, if the antenna module 1 has two antenna substrates 10, it is not necessary to provide AMC6 around the entire periphery of the antenna 4 as long as AMC6 is provided around a portion of the periphery of the antenna 4 to correspond to the antenna substrates 10 (patch antenna elements 12). Alternatively, as shown in FIG. 6B, the antenna 4 may be provided on the upper surface 50a of the disk-shaped substrate 50, and one AMC 6 may be provided around the antenna 4 on the upper surface 50a.

[0069] In addition, in each of the above embodiments, the AMC6 includes a plurality of first unit cells 20, a first ground conductor layer 22, a first dielectric layer 24, and a plurality of first vias 26. However, the AMC6 may also be configured such that a plurality of first unit cells 20 are regularly arranged in the first dielectric layer 24 without providing a plurality of first vias 26.

[0070] Furthermore, in each of the above embodiments, a case where a plurality of patch antenna elements 12 are provided on each antenna substrate 10 has been exemplified, but it is sufficient that at least one patch antenna element 12 is provided on each antenna substrate 10. In addition, in each of the above embodiments, the antenna 4 includes four antenna substrates 10, but for example, five or more antenna substrates 10 may be arranged facing outward. Furthermore, it is sufficient that the antenna 4 includes at least one antenna substrate 10. Furthermore, in each of the above embodiments, the antenna 4 includes the patch antenna element 12, which is a planar antenna (patch antenna). However, the antenna 4 may include other types of antennas, such as a dipole. Furthermore, the antenna 4 may be a pillar-shaped antenna.

[0071] Furthermore, in each of the above embodiments, the antenna substrate 10 and the AMC 6 are connected by the bent portion 16, but the antenna substrate 10 and the AMC 6 may be configured separately. In this case, the AMC 6 and the antenna 4 are not included in a single module, and the AMC 6 can be configured as a separate entity separated from the antenna 4. In this case, the vehicle is equipped with an antenna 4 mounted on the roof surface R, and an AMC 6 mounted on the roof surface R adjacent to the antenna 4. The AMC 6 is configured as a separate entity separated from the antenna 4, without forming a module between the AMC 6 and the antenna 4.

[0072] [About verification testing] Next, we will explain the verification tests conducted to examine the effects of AMC. As a test method, a model of the patch antenna element and AMC was constructed, and the directivity pattern of vertically polarized waves and the directivity pattern of horizontally polarized waves when radio waves were emitted from the patch antenna element using this model were determined by computer simulation. The effectiveness of AMC was verified by comparing the obtained directional patterns.

[0073] FIG. 7A is a perspective view showing the model used in the verification test. As a model for the verification test, an antenna substrate 10 equipped with one patch antenna element 12 and one AMC6 were used, and the directional patterns of horizontally polarized waves and vertically polarized waves when radio waves were emitted from the patch antenna element 12 were determined by simulation. In FIG. 7A, the AMC 6 is placed on a ground plane G that is parallel to the XY plane and has an infinite size. The width dimension W of the side of the AMC6 parallel to the Y direction was set to 50 mm. Five values ​​were set for the distance L of the side of the AMC6 parallel to the X direction by moving the position of the outer edge 6b along the X direction. Five values ​​were set for the distance L in the range of approximately 10 mm to 50 mm, and each was verified. The center position of the antenna substrate 10 (patch antenna element 12) in the Y direction coincides with the center position of the AMC 6 in the Y direction.

[0074] FIG. 7B is a view of the model used in the verification test as viewed along the Y direction. As shown in Figure 7B, the antenna substrate 10 is placed above the ground plane G, tilted with respect to the Z direction. The antenna substrate 10 is placed along a line P2 that is tilted at an angle γ with respect to the line P1. The lines P1 and P2 pass through point C on the ground plane G. Point C coincides with the base end 6a of the AMC 6. In this test, point C, where the ground plane G intersects with line P2, was defined as the base end of the antenna substrate 10. The line P1 is parallel to the Z direction. The angle γ was set to 30 degrees. In other words, the elevation angle of the radiation direction of the patch antenna element 12 was set to 30 degrees. The height H from the ground plane G to the center of the patch antenna element 12 in the Z direction was set to 8.1 mm. The patch antenna element 12 was shaped like a square with each side measuring 2.5 mm. The frequency of the radio waves radiated from the patch antenna element 12 was set to 28 GHz.

[0075] FIG. 8 is an enlarged view of the first surface 6c of the AMC 6. As shown in FIG. The specific frequency band of AMC6 used in the model was a frequency band including 28 GHz. More specifically, the diameter D1 of the circumscribing circle of the first unit cell 20 of the AMC6 was set to 1.65 mm, the gap g1 was set to 0.2 mm, and the diameter D2 of the first via 26 was set to 0.3 mm. The relative permittivity εr of the first dielectric layer 24 of AMC6 was set to 3.7, the dielectric loss tangent was set to 0.005, and the thickness t1 of the first dielectric layer 24 was set to 0.5 mm. The thickness of the first unit cell 20 and the first ground conductor layer 22 was set to 30 μm.

[0076] Furthermore, a model in which an EBG structure 40 is provided around the patch antenna element 12, as shown in FIG. 9, was also used. 9, the settings are the same as those of the above-mentioned model except that the EBG structure 40 is provided around the patch antenna element 12. The shielding band of the EBG structure 40 is a band including 28 GHz, and the settings of the second unit cell, second via, second dielectric layer, etc. of the EBG structure 40 are the same as those of AMC6.

[0077] Using the above model, the directivity patterns were determined for the six examples and one comparative example shown below. Example 1: Seven rows of first unit cells 20 were arranged in the X direction from the base end portion 6a. In this case, the distance L was 10.1 mm (proportion P0.94). Example 2: Nine rows of first unit cells 20 were arranged in the X direction from the base end 6a. In this case, the distance L was 12.9 mm (proportion P1.2). Example 3: Eleven rows of first unit cells 20 were arranged in the X direction from the base end portion 6a. In this case, the distance L was 15.8 mm (proportion P1.48). Example 4: Thirteen rows of first unit cells 20 were arranged in the X direction from the base end 6a. In this case, the distance L was 18.6 mm (proportion P1.73). Example 5: 33 rows of first unit cells 20 were arranged in the X direction from the base end 6a. In this case, the distance L was 47.4 mm (proportion P4.43). Example 6: 33 rows of first unit cells 20 were arranged in the X direction from the base end 6a. In this case, the distance L was 47.4 mm (proportion P4.43). In addition, an EBG structure 40 was provided around the patch antenna element 12. Comparative example: AMC6 was not placed.

[0078] FIG. 10 is a diagram showing the directivity patterns of the first, second, and third embodiments. FIG. 11 is a diagram showing the directivity patterns of the fourth, fifth, and sixth embodiments. FIG. 12 is a diagram showing a directivity pattern of a comparative example.

[0079] 10, 11 and 12, in the directivity pattern of horizontally polarized waves, the 0 degree direction is the X direction (the direction indicated by the X arrow in FIG. 7), and the 90 degree and −90 degree directions are the Y direction. 10, 11, and 12, the directivity pattern of vertically polarized waves indicates the directivity pattern in the XZ plane that passes through the center of the radiation surface of patch antenna element 12. In other words, this directivity pattern of vertically polarized waves indicates the directivity pattern of vertically polarized waves in the radiation direction. In this directivity pattern of vertically polarized waves, the 0-degree direction is the Z direction (the direction indicated by the Z-direction arrow in FIG. 7), and the 90-degree direction is the X direction (the direction indicated by the X-direction arrow in FIG. 7).

[0080] Looking at the directivity pattern of vertically polarized waves in the comparative example (FIG. 12), the maximum gain is achieved at an angle of approximately 60 degrees. This is because the elevation angle of patch antenna element 12 is set to 30 degrees. 12, it can be seen that a dip (null) occurs at a portion where the elevation angle is lower than the maximum gain portion. A dip is a portion where the gain is significantly reduced despite being close to the maximum gain portion.

[0081] Looking at the directivity patterns of vertically polarized waves in Examples 1 to 5 (FIGS. 10 and 11), the maximum gain is achieved at an angle of approximately 60 degrees (corresponding to an elevation angle of approximately 30 degrees in the radiation direction). The dips in the directivity patterns of vertically polarized waves in Examples 1 to 5 are smaller in degree than the dips in the comparative example, and improvements are seen. Remarkable improvements are seen in Examples 2 to 5. Furthermore, the degree of the drop in the drop portion decreases as the distance L increases (as the number of columns increases). In particular, it can be seen that the drop portion in Example 5 is only slightly depressed, and is not significantly different from the maximum gain portion. There is no significant difference between the directivity patterns of horizontally polarized waves of Examples 1 to 5 and the directivity pattern of horizontally polarized waves of the comparative example.

[0082] These results show that the provision of AMC6 can suppress the partial drop that occurs in the directivity pattern of vertically polarized waves in the antenna. It is also understood that the degree of depression of the depression portion is improved by setting the ratio P of the distance L to 1 or more.

[0083] Furthermore, the directivity pattern of vertically polarized waves in the fifth embodiment was compared with the directivity pattern of vertically polarized waves in the sixth embodiment. As a result, a slight drop is observed in the directivity pattern of vertically polarized waves of Example 5, whereas almost no drop is observed in the directivity pattern of vertically polarized waves of Example 6. This shows that by arranging the EBG structure 40 around the patch antenna element 12, it is possible to more effectively suppress the partial drop that occurs in the directivity pattern of vertically polarized waves. In Example 6, only the surface where the AMC6 included in the model is arranged and in contact with the AMC6 is used as the ground plane G, and the area around the AMC6 is left as space, so that gain leakage occurs on the underside of the AMC6. As a result, differences are observed in the shape of the underside of the ground plane G between the pattern of Example 5 and the pattern of Example 6. However, it has been confirmed that similar results are obtained when the model of Example 6 is arranged on a ground plane G of infinite size, as in Example 5.

[0084] 〔others〕 It should be noted that the embodiments disclosed herein are to be considered as illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the meaning described above, and is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0085] 1 Antenna Module 2 Base board 4 Antennas 4a Proximal end 6. Artificial Magnetic Conductors 6a Proximal end 6b Outer edge (outer edge) 6c page 1 10 Antenna board 10a Proximal end 10b Antenna surface 12 patch antenna elements 12a Radiation surface 16 Bending part 20 First unit cell 22 First ground conductor layer 24 First dielectric layer 24a Top side 24b Bottom side 26 First Via 30 Second ground conductor layer 32 Second dielectric layer 32a 2nd side 32b 3rd page 40 Electromagnetic bandgap structure 42 Second unit cell 44 Second Via 46 Non-placement area 50 boards 50a top 100 Antennas 102 Roof surface 104 patch antenna element B Imaginary vertical line D1 diameter D2 diameter G Ground plane H Height L distance P1 straight line P2 straight line Rear roof S center W width dimension g1 gap g2 gap t1 thickness t2 thickness γ angle θ angle

Claims

1. an antenna mounted on the mounting surface; a plurality of plate-shaped conductor members disposed adjacent to the antenna and having a first surface on which a plurality of first unit cells made of a conductor are regularly arranged, each of the plurality of conductor members has a base end adjacent to the antenna; the first surface extends from the base end along the mounting surface, the antenna has one or more patch antenna elements on an antenna surface, and a plurality of antenna substrates erected on the mounting surface; At least one pair of the antenna substrates among the plurality of antenna substrates are erected so that the surfaces opposite to the antenna surfaces of the pair of antenna substrates face each other, The plurality of conductor members are disposed around the plurality of antenna substrates that are erected. Antenna module.

2. Each of the plurality of conductor members is a first ground conductor layer; a first dielectric layer interposed between the plurality of first unit cells and the first ground conductor layer; an electrical length from a boundary between the plurality of first unit cells and the first dielectric layer to a boundary between the first ground conductor layer and the first dielectric layer is 0.03 or more; The antenna module according to claim 1 .

3. Each of the plurality of conductor members has an outer end opposite the base end, the first surface extends from the base end to the outer end, The ratio of the distance from the base end to the outer end to the vacuum wavelength of the radio wave radiated from the antenna is 1 or more. The antenna module according to claim 1 .

4. Each of the plurality of conductor members has an outer end opposite the base end, the first surface extends from the base end to the outer end, The distance from the base end to the outer end is 10.7 mm or more. The antenna module according to claim 1 .

5. each of the plurality of antenna substrates includes one or more patch antenna elements; When the first surface is viewed in plan, a virtual vertical line extending from a radiation surface of the one or more patch antenna elements passes through the first surface. The antenna module according to any one of claims 1 to 4.

6. Each of the plurality of antenna substrates includes: a second ground conductor layer; a second dielectric layer interposed between the one or more patch antenna elements and the second ground conductor layer; an electromagnetic bandgap structure provided to surround the one or more patch antenna elements; The antenna module according to claim 5 .

7. The frequency of the radio waves transmitted and received by the antenna is 20 GHz or higher. The antenna module according to any one of claims 1 to 4.

8. The mounting surface is a roof surface of a vehicle. The antenna module according to any one of claims 1 to 4.

9. The conductive member includes an artificial magnetic conductor. The antenna module according to any one of claims 1 to 4.

10. The car body and an antenna mounted on the top surface of the vehicle body; a plurality of plate-shaped conductor members mounted on the upper surface adjacent to the antenna, the plate-shaped conductor members having a first surface on which a plurality of first unit cells are regularly arranged, each of the plurality of conductor members has a base end adjacent to the antenna; the first surface extends from the base end along the upper surface; the antenna has one or more patch antenna elements on an antenna surface and a plurality of antenna substrates erected on the top surface; At least one pair of the antenna substrates among the plurality of antenna substrates are erected so that the surfaces opposite to the antenna surfaces of the pair of antenna substrates face each other, The plurality of conductor members are disposed around the plurality of antenna substrates that are erected. vehicle.

11. The conductor member is a separate body from the antenna.

11. The vehicle of claim 10.

12. An antenna mounted on a mounting surface; a plate-shaped conductor member disposed adjacent to the antenna and having a first surface on which a plurality of first unit cells made of a conductor are regularly arranged, the conductive member has a base end adjacent the antenna; the first surface extends from the base end along the mounting surface, The antenna is one or more patch antenna elements; a ground conductor layer; a dielectric layer interposed between the one or more patch antenna elements and the ground conductor layer; an electromagnetic bandgap structure provided on the dielectric layer so as to surround the one or more patch antenna elements; Antenna module.

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