antenna device

Abstract

Antenna device (1) with an array antenna having several antenna elements (4) configured to detect an arrival direction of a radio wave, and comprising: a recess (3) formed in a part of a means of transport or building, an antenna element (4) arranged in the recess (3) and a cover (6) or insulating material (7) that closes an opening (3b) of the recess (3), wherein the recess (3) has a base (3a), the opening (3b) and a side wall (3c) connecting the base (3a) and the opening (3b), the recess (3) widens from the base (3a) to the opening (3b) and the base (3a) and the side wall (3c) are made of a ladder, furthermore with an inner cover that covers a surface of the floor (3a) and the side wall (3c) on the opposite side to the opening (3b).

Description

Technical field

[0001] The invention relates to an antenna device. Background of the technology

[0002] If an antenna device is mounted on means of transport, e.g., vehicles, or buildings, there is a risk that it will impair their external appearance, since antenna elements protrude from a surface of the means of transport or building. Therefore, patent references 1 and 2 disclose a configuration in which a recess is formed on a surface of a means of transport or building and antenna elements are arranged in the recess.

[0003] For monitoring a radio wave environment, etc., there is a need for a device to detect the direction of arrival of radio waves over a wide frequency band with high accuracy. Therefore, a method exists using an array antenna in which several antenna elements are arranged, utilizing information about the phase, etc., of radio waves received by each of the multiple antenna elements. Patent citation 3 discloses an antenna device that detects the direction of arrival of radio waves. List of citations from patent literature Patent citation 1: JP 2 692 253 B2 Patent citation 2: JP 2003 - 309 409 A Patent citation 3: JP 2002 - 071 776 A

[0004] German patent application DE 10 2009 038 150 A1 relates to a scalable multiband antenna module with several antenna elements for a vehicle, arranged within a metallic or non-conductive cavity. The metallic cavity can be implemented directly in the vehicle's outer body or be designed as a separate metallic housing or as a metallized plastic housing for fixing in a corresponding slot within the outer body, in which the antenna elements are placed. If the cavity is implemented in the vehicle's outer body, it can be made of a non-conductive plastic material. The cavity forms part of an electrically conductive base that is connected to the vehicle's outer body. The radiation pattern of the antennas can be adjusted by the depth and shape of the cavity.Furthermore, shielding chambers can be implemented within the cavity to protect the corresponding electronic circuits. Summary of the invention: Technical problem

[0005] An embedded antenna for vehicles disclosed in patent citation 1 is a specific frequency band antenna with a relative bandwidth of approximately 20%, and no amplification is taken into account. Therefore, it is difficult to apply this embedded antenna to applications where amplification over a wide band is required (e.g., detecting an arrival direction when monitoring the radio wave environment).

[0006] In a configuration disclosed in patent citation 2, several antenna elements are encapsulated with a molded resin, and the resin encapsulating the antenna elements is fixed in a recess with an adhesive, double-sided tape, or a screw, etc. This complicates the task of mounting an antenna device on a means of transport or building, in particular the task of attaching antenna elements. Furthermore, patent citation 2 does not include a method for maintaining stable characteristics over a wide frequency band, nor does it include a measure against fluctuations in the characteristics caused by the approach of persons or objects.

[0007] It is possible that an antenna device that detects a radio direction (the direction of arrival of radio waves) using multiple antenna elements, as described in patent citation 3, could significantly impair the external appearance of a means of transport or building. An array antenna for accurately detecting the direction of arrival of radio waves must have stable frequency characteristics over a wide band, be less sensitive to fluctuations in these characteristics caused by people or objects present inside a means of transport or building, and optimize the spacing between antenna elements according to the frequency band in which detection takes place. Therefore, certain limitations apply to the size and / or position of the antenna elements, making it difficult to arrange them in an unobtrusive manner. For example, according to Fig. 22 of patent citation 3 significantly impairs the external appearance, as a large mounting space is necessary to mount several antenna elements for detecting a radio direction on a vehicle.

[0008] To reduce the likelihood of the external appearance of a vehicle or building being affected, a disc antenna, embedded in or printed onto a window pane, was used in practice. However, a problem arises because the performance characteristics of a disc antenna can fluctuate easily due to the approach of people or objects. Furthermore, since there are significant limitations on the available installation space, it was difficult to arrange multiple disc antennas at arbitrary intervals.

[0009] Therefore, the invention aims to solve the problem described above and to provide an antenna device that can be easily mounted on a means of transport or building and can detect the direction of arrival of radio waves with high accuracy without significantly affecting the external appearance. Problem solving

[0010] The invention is defined in independent claim 1. Dependent claims describe preferred embodiments.

[0011] An antenna device according to the invention has an array antenna comprising several antenna elements and configured to detect an arrival direction of a radio wave, and comprises: a recess formed in a part of a means of transport or building, an antenna element arranged in the recess, and a cover or insulating material that closes an opening of the recess, wherein the recess has a bottom, the opening, and a side wall connecting the bottom and the opening, and the shape of the recess widens from the bottom to the opening, and the bottom and side wall are made of a conductor. Advantageous effects of the invention

[0012] According to the invention, an antenna can be easily mounted on a means of transport or building, and the direction of arrival of radio waves can be accurately detected without significantly affecting the external appearance. Brief description of the drawings Fig. Figure 1 is a schematic cross-sectional view of the antenna device according to one embodiment of the invention; Fig. Figure 2 is a perspective view of the antenna device with conical antenna elements according to other embodiments of the invention; Fig. Figure 3 is a schematic cross-sectional view of a comparative example of the antenna device according to Fig. 2; Fig. Figure 4 is a schematic cross-sectional view of an example of the antenna device according to Fig. 2; Fig. Figure 5 is a schematic cross-sectional view of further examples of the antenna device according to Fig. 2; Fig. Figure 6 is a diagram of a calculation result of a horizontal gain at each frequency of the antenna devices according to Fig. 3, Fig. 4 to Fig. 5; Fig. Figure 7 is a perspective view of an example of a vehicle with the antenna device according to the invention mounted on it; Fig. Figure 8 is a schematic cross-sectional view of the antenna device according to other embodiments of the invention; Fig. Figure 9 is a schematic cross-sectional view of a modified example of the antenna device according to Fig. 1; Fig. Figure 10 is a schematic cross-sectional view of other modified examples of the antenna device according to Fig. 1; Fig. Figure 11 is a perspective view of an example of a vehicle with other antenna devices according to the invention mounted on it; Fig. Figure 12 is a schematic view of the interior of a vehicle with the attached antenna device according to Fig. 11; Fig. Figure 13A is a cross-sectional view of an example of the antenna devices according to other embodiments of the invention; and Fig. Figure 13B is a cross-sectional view of other examples of the antenna devices according to other embodiments of the invention. Description of embodiments

[0013] The embodiments of the invention are explained below with reference to the drawings. Fig. Figure 1 shows a basic configuration of an antenna device 1 according to the invention. In this example, the antenna device 1 is mounted on a roof section made of a conductor, which serves as a mounting surface 2, of a means of transport, e.g., a vehicle. In other words, a recess 3 is formed on a part of the roof section. The shape of this recess 3 widens from a base 3a to an opening 3b, and a side wall 3c connecting the base 3a to the opening 3b is inclined at an angle of at least 120°, preferably at an angle of at least 135°, with respect to the base 3a. The base 3a and the side wall 3c are electrically connected to each other and form a ground plane (embedded ground plate). The ground plane is made of a conductor and is electrically connected to the mounting surface 2 in which the recess 3 is formed. An antenna element 4 (e.g., a monopole antenna) is positioned in the recess 3.A connection point 5 is provided on the ground part and connected to the antenna element 4. The opening 3b is closed by a cover 6.

[0014] The side wall 3c of this antenna device 1 is inclined, which is why a reflected wave generated on the side wall 3c travels towards the upper opening 3b. Therefore, one benefit is that the horizontal gain is stabilized. Furthermore, since the antenna element 4 is separated from the space below the grounding element by the grounding element, the antenna element 4 is less likely to be affected by a person or object in the space below the grounding element. Therefore, an advantageous benefit is that the antenna characteristics are stabilized. Furthermore, since the mounting surface 2 is made of a conductor and electrically connected to the grounding element, the grounding element is essentially very large. Therefore, it is less likely to be affected by a person or object inside it.

[0015] Fig. Figure 2 shows an antenna device 1 with a conical antenna element 4 with broadband capability as an application example of the antenna device 1 according to Fig. 1. For illustration, cover 6 is shown in this Fig. 2 and the one described later Fig. Numbers 3 to 5, 7, 8 and 11 have been omitted. Fig. 3, Fig. 4 to Fig. Figure 5 shows three examples of the antenna device 1, each consisting of a conical antenna element 4 and a grounding element. In these antenna devices 1, the angles of inclination of the side wall 3b with respect to a horizontal direction (which in these examples is parallel to the ground 3a) are 90°, 130° and 160° respectively. Fig. Figure 6 shows a result of horizontal gains in these antenna devices 1, calculated by performing electromagnetic field simulations. One height of the side wall 3b is half a wavelength at a calculated upper cutoff frequency f1. Based on Fig. 6 can be shown that with a greater increase in the angle of inclination when the side wall 3b is tilted, the fluctuations caused by changes in frequencies become smaller, which is why these characteristic values ​​can be designed to be more stable.

[0016] The number of antenna elements 4 arranged in a recess 3 is not limited to one, and several antenna elements 4 can be arranged in the recess 3. Fig. Figure 7 shows a configuration in which a circular array antenna with several antenna elements 4 arranged in a recess 3 is embedded in a roof section of a means of transport. The installation location of a disc antenna is limited to a single disc section, which is why there is little flexibility in the construction of an array antenna. In contrast, in the invention, several antenna elements 4 are arranged at arbitrary intervals, which makes it possible to provide an array antenna that is less conspicuous.

[0017] The shape of antenna element 4 is not based on the straight shape according to Fig. 1 or the conical shape according to Fig. 2. This means that the antenna element 4 can have a variety of arbitrary shapes, e.g., a folded cable, a flat shape, and a three-dimensional shape. Furthermore, a matching element can be attached at the connection point 5. Additionally, a shorting element can be provided between the antenna element 4 and the ground, as in an inverted F-antenna. When power is supplied via a coaxial cable, the influence of the cable can also be reduced by providing a ferrite core around the coaxial cable.

[0018] The mass component, consisting of the base 3a and the side wall 3c of the recess 3, can be a variety of conductors, e.g., a plate conductor, a thin-film conductor, a stamped metal, or a network conductor. Furthermore, it can have a structure in which the conductor is held by an insulator. In addition, the shape of the mass component is not limited to a truncated cone shape according to Fig. 2 is restricted and can instead be any shape in which the side wall 3c is inclined. The angle of inclination of the side wall 3c need not be constant, and the base 3a can also be inclined. The recess 3 can also have such a shape that the base 3a and the side wall 3c are seamlessly formed as one piece. For example, the recess 3 has an inverted conical shape. Furthermore, the side wall 3c can have a stepped shape according to Fig. 8 or, although not shown, have a shape with a curved surface.

[0019] The cover 6, which covers the recess, is not limited to a plate or similar object placed only over the mass part. That is, the cover 6 can be a plate or similar object positioned to cover a wider area than the mass part, including the mounting area 2 as per [reference]. Fig. 9. A support structure can be provided between the mass part and the cover 6 to support the cover 6. Alternatively, instead of using the cover 6, it can have a structure in which the recess 3 is filled with an insulating material 7 according to Fig. 10 is filled. In addition, both the cover 6 and the insulating material 7 can be used in combination.

[0020] The number of antenna elements 4 arranged in the recess 3 is not limited to one, and several antenna elements can be arranged in the recess 3. According to the invention, several antenna elements 4 can be arranged in a recess 3 as shown. Fig. 7 arranged to form an array antenna for detecting an arrival direction of radio waves. However, the antenna array may instead have a configuration in which several recesses 3 according to Fig. 11 are formed, each containing an antenna element 4. Furthermore, any number of recesses 3 can be formed, each containing an antenna element 4. For the electrical connection between the side wall 3c and the mounting surface 2, and between the side wall 3c and the base 3, a method can be used in which they are electrically connected to each other over their entire circumference, a method in which they are connected to each other at several points, or a method in which they are connected to each other via high-frequency capacitive coupling. Furthermore, depending on the desired power output, they can be disconnected. The antenna device according to this embodiment detects the direction of arrival of radio waves using a known MUSIC method, etc., in which a direction is determined by processing the amplitudes and phases of radio waves received via several antenna elements 4. However, the direction of arrival of radio waves can be detected by other methods. In this embodiment, according to the preceding description, several antenna elements 4 form an array antenna that detects the direction of arrival of radio waves.

[0021] The antenna element 4 can be a ground-type antenna element 4, e.g., a monopole type, or other types of antenna elements 4, e.g., a dipole antenna element 4, etc. When using a dipole antenna element 4, the base 3a and the side wall 3b are also preferably made of a conductor. By arranging the dipole antenna element 4 described above between the base 3a and the side wall 3b, as well as the cover 6, the advantageous effect is achieved that this antenna element 4 is less susceptible to reflections in the side wall 3b than the monopole antenna element 4. In the antenna device 1 according to this embodiment, the entire recess 3 can be removed. Therefore, maintenance can be easily performed, and the antenna device can be easily installed and replaced if necessary.

[0022] The functions and effects of the antenna device 1 according to the invention are described below. The antenna device 1, which detects the direction of arrival of radio waves, often needs to cover a wide frequency band, e.g., when monitoring a radio wave environment. If an object or similar is present that causes a reflection around the antenna device 1, a false image is tended to be generated at a specific frequency according to the distance between the antenna device 1 and the object. Therefore, it was difficult to mount the antenna device on a means of transport or similar in such a way that it appeared inconspicuous. In contrast, the antenna device 1 according to the invention can reduce the influence of reflections over a wide frequency range and detect a direction over a broad band by providing the recess 3 in the mounting surface 2, e.g., a roof section of a means of transport, and arranging the antenna element 4 in the recess 3.The angle of inclination of the side wall 3c with respect to the floor 3a (horizontal surface) is at least 120° or more, preferably at least about 135°.

[0023] Furthermore, it is possible to obtain stable amplification over a broad band by shaping the antenna element 4 into a three-dimensional form, e.g., a cone. This allows good performance characteristics to be obtained for the antenna device 1, which detects the direction of arrival of radio waves by combining the inclined side wall 3c and the base 3a with the three-dimensionally shaped antenna element 4.

[0024] The configuration, in which several small recesses 3 according to Fig. The formation of 11 is particularly effective when mechanical strength is weakened by the formation of a large recess 3. For example, the recesses 3 can be formed in gaps between frames 8 of a roof section of a means of transport, while the frames 8 are formed according to Fig. 12 remain, which shows a state in which an inner sheet in a means of transport is removed, which is why an array antenna can be formed to detect a direction while maintaining the strength of the means of transport.

[0025] The antenna device 1 according to the invention has the characteristic that its parameters hardly change even when persons or objects approach the antenna device, since the antenna element 4 is separated from the space below it by the base 3a and the side wall 3c, which are made of a conductor. Additionally, according to Fig. 13A It is possible to make the characteristics even more resistant to changes by adding an inner cover 9 made of an insulator, which covers the base 3a and the side wall 3c to isolate them from the space below (space within the means of transport or building). The inner cover 9 covers the surface of the base 3a and the side wall 3c on the side opposite the opening 3b. The reason for this cover is explained below. If the base 3a and the side wall 3c, which are made of a conductor, come into contact with a human body or the like, a high-frequency current flows into them, and their characteristics change. However, it is possible to prevent this change by preventing contact between them. Furthermore, capacitive coupling has a slightly negative effect even without such contact. Therefore, the aforementioned change can be prevented more effectively by, according to Fig.13B the inner cover 9 is moved away from the base 3a and the side wall 3c, which are made of a conductor. This allows an arrangement to be provided in which the inner cover 9 covers the surface of the base 3a and the side wall 3c on the side opposite the opening 3b with a gap between them. Furthermore, a similar effect can be obtained by increasing the thickness of the inner cover 9 instead of moving it away. It is effective to form the inner cover 9 using a material with a low relative dielectric constant in order to reduce its capacitance.

[0026] Although the invention has been previously explained with reference to embodiments, the invention is not limited to the embodiments described above. Various modifications will be apparent to those skilled in the art, which can be made to the configuration and details of the invention within the scope of protection of the invention.

[0027] This application is based on and claims priority from the Japanese patent application JP 2016 - 068 848 A, filed on March 30, 2016. List of reference symbols 1 antenna device 2 Cultivated area 3 recesses 3a Ground 3b Opening 3c side wall 4 antenna elements 5 connection point 6 Cover 7 Insulation material 8 frames 9 Inner cover

Claims

Antenna device (1) with an array antenna having several antenna elements (4) configured to detect the direction of arrival of a radio wave, and comprising: a recess (3) formed in a part of a means of transport or building, an antenna element (4) arranged in the recess (3), and a cover (6) or insulating material (7) closing an opening (3b) of the recess (3), wherein the recess (3) has a base (3a), the opening (3b), and a side wall (3c) connecting the base (3a) and the opening (3b), the recess (3) widening from the base (3a) to the opening (3b), and the base (3a) and the side wall (3c) being made of a conductor, further comprising an inner cover that provides a surface of the base (3a) and the side wall (3c) opposite the opening (3b) covers. Antenna device (1) according to claim 1, wherein the base (3a) and the side wall (3c) form a ground part of a ground antenna. Antenna device (1) according to claim 1 or 2, wherein the side wall (3c) has a shape with an inclined surface or a stepped shape. Antenna device (1) according to one of claims 1 to 3, wherein a connection point is provided on the floor (3a) or the side wall (3c) and the connection point is connected to the antenna element (4). Antenna device (1) according to one of claims 1 to 4, wherein an angle between the side wall (3c) and the bottom (3a) is at least 120°. Antenna device (1) according to claim 5, wherein the angle between the side wall (3c) and the bottom (3a) is at least 135°. Antenna device (1) according to one of claims 1 to 6, wherein several antenna elements (4) are arranged in a recess (3).

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