Antenna device and antenna housing

Abstract

To provide an antenna device including a housing in which a function as a housing is maintained and moldability is ensured while suppressing a decrease in an antenna gain, and provide an antenna housing as the housing.SOLUTION: An antenna device 1 includes: a housing 10 formed of a material having radio wave transparency; and an antenna element 2 housed in the housing 10 and having a main radiation direction set at a position of a corner part 10A of the housing 10. The housing 10 includes: a curved surface part 10C configuring the corner part 10A; and an upper surface part 10U and a side surface part 10S connected to the curved surface part 10C. A thickness of the housing 10 gradually increases from the upper surface part 10U and the side surface part 10S to a center of the curved surface part 10C, and an inner surface of the housing 10 continuously connects from the upper surface part 10U and the side surface part 10S to the center of the curved surface part 10C with no step.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an antenna device and an antenna housing. [Background technology]

[0002] As an antenna device in which a patch array antenna is housed in a radome, there is known one in which the inner wall of the radome is formed so that the thickness of the radome changes in a step shape at angles of -45° and +45° relative to the radiation vertical plane as viewed from the center of the patch array antenna (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 136927 Summary of the Invention [Problem to be solved by the invention]

[0004] In the antenna device described in Patent Document 1, the inner wall surface of the radome, on which the radio waves radiated from the antenna element hit, has a stepped shape, which may cause diffuse reflection of the radio waves, which may cause side lobes to appear in positions other than the main radiation direction of the antenna element, thereby disrupting the radiation pattern of the antenna element and reducing the antenna gain.

[0005] In addition, since the radome, which is a resin molded product, has points where the thickness changes suddenly, warping may occur near those points during resin molding, resulting in molding defects.Furthermore, it is known that the thickness of a radome that maximizes antenna gain is 1 / 2 the wavelength of the radio waves that it transmits, but it is thought that the thickness of a radome that maximizes antenna gain in the high frequency band may become so large that it may result in molding defects.

[0006] In view of the above circumstances, the present invention aims to provide an antenna device including a housing that suppresses a decrease in antenna gain while maintaining the functionality of the housing and ensuring moldability, and an antenna housing as such a housing. [Means for solving the problem]

[0007] The antenna device of the present invention comprises a housing made of a radio wave transparent material, and an antenna element housed in the housing and having a main radiation direction set at a corner of the housing, the housing having a curved surface portion that forms the corner and a flat surface portion connected to the curved surface portion, the thickness of the housing gradually increasing from the flat surface portion to the center of the curved surface portion, and the inner surface of the housing is continuously connected without any steps from the flat surface portion to the center of the curved surface portion.

[0008] The antenna housing of the present invention is a housing made of a material that is radio wave transparent, and houses an antenna element whose main radiation direction is set at the position of a corner of the housing, and includes a curved surface portion that forms the corner and a flat surface portion connected to the curved surface portion, the thickness of the housing gradually increases from the flat surface portion to the center of the curved surface portion, and the inner surface of the housing is continuously connected without any steps from the flat surface portion to the center of the curved surface portion. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an antenna device including a housing that suppresses a decrease in antenna gain while maintaining the functionality of the housing and ensuring moldability, and an antenna housing as the housing. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing an antenna device according to one embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing the antenna element shown in FIG. [Figure 3] FIG. 3 is a diagram showing a radiation pattern of the antenna element shown in FIG. [Figure 4]FIG. 4 is an enlarged cross-sectional view of a part of the antenna device shown in FIG. [Figure 5] FIG. 5 is a diagram showing the relationship between the antenna element and the housing. [Figure 6] FIG. 6 is a graph showing the results of a simulation of the relationship between the distance between the antenna element and the housing and the antenna gain. [Figure 7] FIG. 7 is a graph showing the results of a simulation of the relationship between the distance between the antenna element and the housing and the antenna gain when the thickness of the housing is uniform and λ. [Figure 8] FIG. 8 is a graph showing the results of a simulation of the relationship between the thickness of the antenna element and the antenna gain when the distance between the antenna element and the housing is λ. [Figure 9] FIG. 9 is a graph showing the results of a simulation of the relationship between the thickness of the housing in the main radiation direction of the antenna element and the antenna gain when the distance between the antenna element and the housing is λ and the thickness of the housing in any direction other than the main radiation direction of the antenna element is 2 mm. [Figure 10] FIG. 10 is an enlarged cross-sectional view showing a part of an antenna device according to a comparative example. [Figure 11] FIG. 11 is a diagram showing a radiation pattern of the antenna device shown in FIG. [Figure 12] FIG. 12 is a diagram illustrating a radiation pattern of the antenna device shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described below in accordance with preferred embodiments. Note that the present invention is not limited to the embodiments described below, and the embodiments described below can be modified as appropriate without departing from the spirit of the present invention. In addition, in the embodiments described below, some components are omitted from illustration and description, but for the details of the omitted technologies, publicly known or well-known technologies are applied as appropriate within the scope of not causing any contradictions with the content described below.

[0012] Fig. 1 is a cross-sectional view showing an antenna device 1 according to one embodiment of the present invention. The antenna device 1 shown in this figure is an antenna for external vehicle communication that uses millimeter-wave radio waves, such as those in the 28 GHz or 60 GHz band. The antenna device 1 includes an antenna element 2 that transmits and receives millimeter-wave radio waves, a substrate 3 on which the antenna element 2 is mounted, electronic components 4 mounted on the substrate 3, a bottom plate 5, a spacer 6 for fixing the substrate 3 to the bottom plate 5, and a housing 10.

[0013] The antenna element 2 is a patch antenna (microstrip antenna) mounted near the end 3A of the substrate 3. As will be described in detail later, the antenna element 2 has directivity in a direction inclined relative to the direction perpendicular to the radiation surface (hereinafter referred to as the oblique direction). In other words, the radiation direction in which the antenna gain of the antenna element 2 is maximum (hereinafter referred to as the main radiation direction) is the oblique direction of the antenna element 2.

[0014] The substrate 3 is a dielectric substrate on one side of which the antenna element 2 is formed and on the other side of which a ground conductor plate is formed. The electronic component 4 is a connector or the like mounted on the other side of the substrate 3. The bottom plate 5 is a plate material that forms the bottom of the antenna device 1. The spacer 6 is a cylinder placed between the substrate 3 and the bottom plate 5 and has a threaded inner surface. The substrate 3 is fastened to one axial end of the spacer 6, and the bottom plate 5 is fastened to the other axial end of the spacer 6.

[0015] Housing 10 is a rectangular housing made of a radio wave-transmitting material that allows millimeter-wave band radio waves to pass through, and includes top surface 10U, side surface 10S, and corner 10A. Corner 10A is the boundary between top surface 10U and side surface 10S, and both the outer and inner surfaces form arc-shaped curved surface 10C. The bottom of housing 10 is open and is closed by bottom plate 5. Housing 10 and bottom plate 5 house and protect antenna element 2, substrate 3, electronic component 4, and spacer 6.

[0016] Antenna element 2 is disposed near corner 10A of housing 10, and corner 10A is located in the main radiation direction of antenna element 2. As will be described in detail later, the thickness of corner 10A gradually increases from the boundary between corner 10A and top surface 10U toward the center of corner 10A, and gradually increases from the boundary between corner 10A and side surface 10S toward the center of corner 10A.

[0017] 2 is a perspective view showing the antenna element 2 shown in FIG. 1. As shown in this figure, the antenna element 2 is a patch array antenna in which a plurality of rectangular patch antennas 2A are arranged along an edge 3A of a substrate 3, and is mounted near the edge 3A of the substrate 3. The width direction of the patch antennas 2A is parallel to the arrangement direction of the patch antennas 2A (the X direction in FIG. 3), and the longitudinal direction of the patch antennas 2A is perpendicular to the arrangement direction of the patch antennas 2A. A corner 10A of the housing 10 is located diagonally above the antenna element 2 (in a direction inclined relative to the vertical direction and the longitudinal direction of the patch antennas 2A).

[0018] Fig. 3 is a diagram showing the radiation pattern of the antenna element 2 shown in Fig. 2. As shown in this figure, the main radiation direction of the antenna element 2 is set in a direction inclined with respect to the vertical direction (Z direction in the figure) and the longitudinal direction of the patch antenna 2A (Y direction in the figure). A corner 10A of the housing 10 is located in the main radiation direction of the antenna element 2.

[0019] Fig. 4 is an enlarged cross-sectional view of a portion of the antenna device 1 shown in Fig. 1. As shown in this figure, the thickness of the top surface 10U and the side surface 10S of the housing 10 is d1, while the thickness (maximum thickness) of the center of the corner 10A is d0 (>d1). Note that it is not essential that the thicknesses of the top surface 10U and the side surface 10S be the same, and there may be a difference between the thicknesses of the two.

[0020] The thickness of corner 10A gradually increases from d1 to d0 from the boundary between corner 10A and top surface 10U to the center of corner 10A, and gradually increases from d1 to d0 from the boundary between corner 10A and side surface 10S to the center of corner 10A. Specifically, the dimensions of housing 10 are set according to the following formula (1) so that corner 10A (curved surface portion 10C) of housing 10 is continuously connected to top surface 10U and side surface 10S as linear portions without any steps.

number

[0021] 5 is a diagram showing the relationship between the antenna element 2 and the housing 10. Factors of the housing 10 that affect the radio waves radiated by the antenna element 2 include the electrical characteristics of the material of the housing 10, the thickness d of the housing 10, and the distance l between the antenna element 2 and the housing 10.

[0022] Fig. 6 is a graph showing the results of a simulation of the relationship between the antenna gain and the distance l between the antenna element 2 and the housing 10. In this simulation, a resin flat plate representing the housing 10 was placed above the antenna element 2, and it was confirmed how the antenna gain would change when the distance l between the antenna element 2 and the flat plate was changed.

[0023] 6, this simulation confirmed that the antenna gain is maximized when the distance l between the antenna element 2 and the flat plate is an integral multiple of 1 / 2 the wavelength λ of the radio wave radiated by the antenna element 2. Therefore, in the antenna device 1 according to this embodiment, the distance in the main radiation direction between the center of the radiation surface of the antenna element 2 and the inner surface of the corner 10A is set to an integral multiple (1 / 2, 1, 1.5, 2, etc.) of 1 / 2 the wavelength λ of the radio wave radiated by the antenna element 2.

[0024] FIG. 7 is a graph showing the results of a simulation of the relationship between the distance l between the antenna element 2 and the housing 10 and the antenna gain when the thickness of the housing 10 is uniform at λ. In this simulation, an antenna device with no protrusions on the housing 10 was assumed as the antenna device on the roof of the vehicle, and capable of communicating in four directions (front, rear, left, and right) of the vehicle. In addition, the thickness d of the housing 10 was kept uniform, and it was confirmed how the antenna gain changed when the distance l between the antenna element 2 and the housing 10 was changed. Here, the thickness d of the housing 10 was determined by taking into account the wavelength shortening of radio waves inside the resin, and was expressed as d=wavelength λ×1 / 2×1 / √ε r It was set to ≒0.3λ. r is the dielectric constant of the resin, and ε r =2.7.

[0025] As shown in the graph of Fig. 7, this simulation confirmed that the antenna gain is maximized when the distance l between the antenna element 2 and the housing 10 is r = wavelength λ × 1 / 2 × 2 = λ. It was also confirmed that the antenna gain is 11.8 dB when the housing 10 is not present.

[0026] 8 is a graph showing the results of a simulation of the relationship between the thickness d of the antenna element 2 and the antenna gain when the distance l between the antenna element 2 and the housing 10 is λ. In this simulation, we confirmed how the antenna gain changes when the thickness d of the housing 10 is changed while the distance l between the antenna element 2 and the housing 10 is kept constant.

[0027] As shown in the graph of Fig. 8, this simulation confirmed that the antenna gain is maximized when the thickness d is d ≈ 0.3λ. Here, the effective wavelength λ inside the housing 10 is eff is λ eff =λ / √ε r Since it is calculated as 0.3λ=0.49λ eff ≒λ eff / 2. It is known that the optimal relationship between the thickness d of the housing 10 and the wavelength λ of the radio waves emitted by the antenna element 2 is d = λ / 2, and therefore simulations confirmed that the optimal value for thickness d is as theoretically determined. It was also confirmed that the antenna gain without the housing 10 is 11.8 dB.

[0028] When molding a plastic housing using injection molding, the recommended housing thickness is 1 to 3 mm to minimize molding defects. In contrast, when the millimeter-wave radio wave frequency is 77 GHz, which is the frequency used in antennas for external vehicle communications, the wavelength λ of the radio waves is λ = 3.9 mm, and the optimal housing thickness d is 1.95 mm, within the recommended range. However, when the millimeter-wave radio wave frequency is 28 GHz, which is the frequency used in 5G, the wavelength λ of the radio waves is λ = 10.7 mm, and the optimal housing thickness d is 5.3 mm, outside the recommended range, if wavelength shortening within the housing is not considered, and 3.3 mm, outside the recommended range, even if wavelength shortening within the housing is considered. Therefore, if the housing thickness d is made uniform, the frequency band of millimeter-wave radio waves that can be used is limited.

[0029] Therefore, in the antenna device 1 according to this embodiment, as shown in FIG. 4, the thickness d1 of the housing 10 in a direction other than the main radiation direction of the antenna element 2 is set to a thickness within the range recommended from the viewpoint of suppressing molding defects during injection molding (for example, 1 to 3 mm), and the thickness d0 of the housing 10 in the main radiation direction of the antenna element 2 is set to a thickness recommended from the viewpoint of maximizing the antenna gain.

[0030] 9 is a graph showing the results of a simulation of the relationship between the thickness d0 of the housing 10 in the main radiation direction of the antenna element 2 and the antenna gain when the distance l between the antenna element 2 and the housing 10 is λ and the thickness d1 of the housing 10 in directions other than the main radiation direction of the antenna element 2 is 2 mm. In this simulation, the distance l between the antenna element 2 and the housing 10 was kept constant at l = λ, the thickness d1 of the housing 10 in directions other than the main radiation direction of the antenna element 2 was set to 2 mm, and it was confirmed how the antenna gain changed when the thickness d0 of the housing 10 in the main radiation direction of the antenna element 2 was changed.

[0031] As shown in the graph in Figure 9, in this simulation, the thickness d0 is d0 = 3.3 mm ≒ 0.3λ ≒ 0.49λ eff It was confirmed that the antenna gain is maximized when the thickness d of the housing 10 gradually changes from d1 to d0, as expressed by the above formula (1), compared to when the thickness d of the housing 10 is uniform (see the graph in FIG. 8). The cause of this phenomenon is thought to be that the corners 10A of the housing 10 are configured like convex lenses, which focus the radio waves radiated from the antenna element 2. Therefore, in the antenna device 1 according to this embodiment, the thickness d of the housing 10 is configured to gradually increase from d1 to d0 from the top surface 10U and side surface 10S to the center of the corners 10A, as expressed by the above formula (1), and the thickness d0 of the housing 10 in the main radiation direction of the antenna element 2 is set to a value equal to the effective wavelength λ inside the housing 10. eff It was set to 1 / 2 of that.

[0032] 10 is an enlarged cross-sectional view of a portion of an antenna device 100 according to a comparative example. The antenna device 100 shown in this figure includes a housing 110 instead of the housing 10 described above. Note that the same components as those in the antenna device 1 according to the above embodiment are denoted by the same reference numerals, and the description of the above embodiment is incorporated herein.

[0033] Housing 110 has step portions 110B where the thickness changes suddenly at the boundaries between corner portions 110A and top surface portion 110U. In housing 110 according to this comparative example, the thickness of top surface portion 110U is greater than the thickness of corner portions 110A, so that the inner wall surface of top surface portion 110U protrudes toward antenna element 2.

[0034] Fig. 11 is a diagram showing the radiation pattern of the antenna device 100 shown in Fig. 10. As shown in this figure, when a step 110B is present on the inner surface of the housing 110, the radio waves radiated from the antenna element 2 hit the step 110B, disrupting the radiation pattern, and it can be seen that the radio waves are reflected in the -180° direction.

[0035] Fig. 12 is a diagram showing the radiation pattern of the antenna device 1 shown in Fig. 1. As shown in this figure, when there are no steps on the inner surface of the housing 10 and the shape of the inner surface of the housing 10 changes continuously from the top surface 10U and side surface 10S to the center of the corner 10A, it can be confirmed that the disturbance of the radiation pattern of the radio waves radiated from the antenna element 2 is suppressed and the generation of side lobes at positions other than the main radiation direction is suppressed. It can also be confirmed that in this case, the antenna gain is larger than when the housing 10 is not present.

[0036] As described above, in antenna device 1 according to this embodiment, the main radiation direction of antenna element 2 is set at the position of corner 10A of housing 10, which is made of a radio wave transparent material, and housing 10 has curved surface portion 10C that forms corner 10A, and top surface portion 10U and side surface portion 10S that are flat portions connected to curved surface portion 10C. Here, thickness d of housing 10 gradually increases from top surface portion 10U and side surface portion 10S toward the center of corner 10A, and the inner surface of housing 10 is continuously connected without step from top surface portion 10U and side surface portion 10S to the center of corner 10A.

[0037] This allows the thickness d0 of the housing 10 at a position in the main radiation direction of the antenna element 2 to be greater than the thickness d1 of the housing 10 at a position other than the main radiation direction of the antenna element 2. Therefore, for the thickness d0 of the housing 10 at a position in the main radiation direction of the antenna element 2, the effective wavelength λ of the radio wave radiated by the antenna element 2 inside the housing 10 is eff The thickness d1 of the housing 10 at positions other than the main radiation direction of the antenna element 2 can be set to 1 to 3 mm, which is suitable for injection molding.

[0038] In addition, since there are no stepped portions on the inner surface of the housing 10 that would disturb the radiation pattern of the radio waves emitted from the antenna element 2, it is possible to suppress disturbance of the radiation pattern of the radio waves emitted by the antenna element 2 and to suppress a decrease in the gain of the antenna element 2. Furthermore, since there are no stepped portions in the housing 10 where the thickness changes suddenly, it is possible to prevent molding defects caused by warping that occurs during injection molding.

[0039] In the antenna device 1 according to this embodiment, the thickness d0 at the center of the corner 10A of the housing 10 is set to be equal to the effective wavelength λ of the radio wave radiated from the antenna element 2 inside the housing 10. eff Therefore, the gain of the radio wave radiated from the antenna element 2 in the main radiation direction can be increased.

[0040] Furthermore, in the antenna device 1 according to this embodiment, the thickness d0 at the center of the corner 10A satisfies the above formula (1). This allows the inner surface of the housing 10 to be configured so that it is continuous and seamless from the top surface 10U and the side surface 10S to the center of the corner 10A.

[0041] Furthermore, in the antenna device 1 according to this embodiment, the distance 1 between the antenna element 2 and the corner 10A is an integral multiple of 1 / 2 the wavelength λ of the radio wave radiated from the antenna element 2. Therefore, it is possible to increase the gain of the radio wave radiated from the antenna element 2 in the main radiation direction.

[0042] The present invention has been described above based on the above embodiment, but the present invention is not limited to the above embodiment, and modifications may be made to the above embodiment within the scope of the spirit of the present invention, or publicly known or well-known technologies may be combined as appropriate.

[0043] For example, in the above embodiment, the thickness d0 at the center of the corner 10A is set to the effective wavelength λ of the radio wave radiated from the antenna element 2 inside the housing 10. eff However, the thickness d0 at the center of the corner 10A is set to 1 / 2 of the effective wavelength λ eff 1, 1.5, 2.0 times, etc., of the effective wavelength λ eff It may be an integer multiple of 1 / 2 of the above.

[0044] Furthermore, in the above embodiment, the antenna element 2 is a patch antenna, but the antenna element 2 may be a three-dimensional antenna element such as a horn antenna, or a linear antenna element such as a dipole antenna.

[0045] In addition, in the above embodiment, the antenna device 1 is an antenna for communication outside the vehicle, but the antenna device 1 may also be applied to a base station, other communication equipment, etc. Furthermore, the present invention can also be applied to a millimeter wave radar device for a vehicle that measures the distance, angle, speed, etc. of an object using radio waves in the millimeter wave band. [Explanation of symbols]

[0046] 1: Antenna device 2: Antenna element 10: Housing (antenna housing) 10A: Corner 10C: Curved part 10U:Top part (flat part) 10S: Side part (flat part) d: thickness d0: thickness d1: thickness l :distance λ :wavelength λ eff : Effective wavelength

Claims

1. a housing formed of a radio wave transparent material; an antenna element housed in the housing and having a main radiation direction set at a corner of the housing; Equipped with The housing includes: a curved surface portion that constitutes the corner portion; a flat surface portion connected to the curved surface portion; Equipped with the thickness of the housing gradually increases from the flat surface portion to the center of the curved surface portion; The inner surface of the housing is continuously connected without any steps from the flat surface portion to the center of the curved surface portion. Antenna device.

2. 2. The antenna device according to claim 1, wherein the thickness of the curved portion at the center is an integral multiple of 1 / 2 of the effective wavelength of the radio wave radiated from the antenna element inside the housing.

3. 3. The antenna device according to claim 1, wherein the distance between the antenna element and the center of the curved surface portion is an integral multiple of half the wavelength of the radio wave radiated from the antenna element.

4. 3. The antenna device according to claim 1, wherein the thickness of the curved portion at the center thereof satisfies the following formula (1): [Equation 1] However, r ０ is the radius of curvature of the outer surface of the curved surface portion, and r ｉ is the radius of curvature of the inner surface of the curved surface portion, and d ０ is the thickness at the center of the curved surface portion, and d １ is the thickness of the planar portion, and θ is the angle between the main radiation direction of the antenna element and the radiation surface of the antenna element.

5. An antenna housing is a housing formed of a material having radio wave transparency, and houses an antenna element whose main radiation direction is set at a corner position of the housing, a curved surface portion that constitutes the corner portion; a flat surface portion connected to the curved surface portion; Equipped with the thickness of the housing gradually increases from the flat surface portion to the center of the curved surface portion; The inner surface of the housing is continuously connected without any steps from the flat surface portion to the center of the curved surface portion. Antenna housing.

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