Antenna device and vehicle

Abstract

To improve the performance of an antenna provided on the roof of a vehicle. [Solution] An antenna device installed on the roof of a vehicle, comprising an antenna element at least a portion of which extends along the roof, and an opening is provided in the metal plate constituting the roof along the antenna element so as to surround the antenna element when viewed from above in the normal direction of the roof surface.

Description

[Technical Field]

[0001] The present invention relates to an antenna device mounted on a vehicle and the vehicle. [Background technology]

[0002] One type of vehicle antenna is the so-called shark fin antenna. Shark fin antennas are designed to reduce air resistance and have a refined appearance, and are shaped like a shark's dorsal fin. For example, a mounting structure for a vehicle antenna device has been proposed in which a vehicle antenna device including an antenna main body and an antenna cover is mounted on the roof of a vehicle (Patent Document 1). The mounting structure for a vehicle antenna device includes a metal base to which the antenna main body is attached, and a plastic roof to which the antenna cover is attached so as to cover the antenna main body. The plastic roof also has an opening inside the outer periphery of the antenna cover through which the base or the antenna main body is inserted. The outer periphery of the antenna cover is bonded to the plastic roof around the opening with an adhesive. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2023 / 223795 Summary of the Invention [Problem to be solved by the invention]

[0004] Shark fin antennas sometimes use an inverted-L antenna, a type of quarter-wavelength monopole antenna, or a modified inverted-F antenna as their antenna element. Shark fin antennas are installed on the roof of a vehicle, and the size of the cover is limited and tapered to reduce air resistance. That is, the farther away from the roof, the smaller the cross-sectional area of ​​the cover cut in a plane parallel to the roof, and the smaller the size of the object that can be accommodated inside the cover. Therefore, to ensure a certain horizontal length of the antenna element as described above, the antenna element must be located close to the roof, where its cross-sectional area is relatively large. However, because the vehicle's roof sheet metal acts as a ground plane, placing the antenna element close to the vehicle roof reduces the antenna gain. Therefore, this technology aims to improve the performance of antennas installed on vehicle roofs. [Means for solving the problem]

[0005] The antenna device according to the present disclosure is installed on the roof of a vehicle. The antenna device includes an antenna element at least partially extending along the roof, and an opening is provided in the sheet metal constituting the roof along the antenna element so as to surround the antenna element in a top view of the roof viewed from above in the normal direction of the roof surface. [Effects of the Invention]

[0006] According to the present technology, it is possible to improve the performance of an antenna provided on the roof of a vehicle. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic perspective view of the antenna device according to the first embodiment. [Figure 2] FIG. 2 is a schematic side view of an antenna device for explaining a comparative example. [Figure 3]FIG. 3 is a diagram showing the relationship between the height of the element and the antenna sensitivity. [Figure 4] FIG. 4 is a diagram illustrating the antenna sensitivity of the antenna device. [Figure 5] FIG. 5 is a schematic perspective view of the antenna device according to the second embodiment. [Figure 6] FIG. 6 is a schematic perspective view of the antenna device according to the third embodiment. [Figure 7] FIG. 7 is a schematic perspective view of the antenna device according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] <Embodiment 1> Hereinafter, an embodiment will be described with reference to the drawings. Fig. 1 is a schematic perspective view of an antenna device. Fig. 1 mainly shows the arrangement of antenna elements and the mounting structure of the antenna to the roof. For convenience, Fig. 1 also shows up-down, front-rear, left-right directions.

[0009] An antenna device 3 is attached to the roof 2 of a vehicle 1 shown in FIG. 1. The vehicle 1 is a typical automobile. The roof 2 is an outer panel of the roof portion of the vehicle 1, and is a metal outer panel (also called "sheet metal"). At least a portion of the roof 2 may be curved. The antenna device 3 is a shark fin antenna that has an antenna element (also called simply "element") 4 inside a cover that looks like a shark's dorsal fin. The antenna device 3 may further include a substrate that includes an amplifier and the like. The cover of the antenna device 3 is adhered to the roof 2. The element 4 is, for example, a linear conductor. The element 4 may be an inverted L-shaped antenna in which the element of a quarter-wavelength monopole antenna is bent 90 degrees, or an inverted F-shaped antenna that is fed from the midpoint, a helical coil, a plate antenna, or the like.

[0010] An opening 21 is formed in the roof 2 along the direction in which the element 4 extends. That is, a portion of the metal sheet of the roof 2 is hollowed out. The opening 21 is provided along the element 4 so as to surround the element 4 in a top view of the roof 2, looking from above ("above" in FIG. 1) to below ("below" in FIG. 1) in the normal direction of the surface of the roof 2. That is, the opening 21 is formed in and around the orthogonal projection of the element 4 on the roof 2. The position and size of the opening 21 are preferably such that the portion directly below the element 4 is at the center and includes the surrounding area, but it is sufficient if 90% or more of the orthogonal projection of the element 4 in the top view is included in the opening 21. For example, the end of the element 4 on the ground side or the end on the tip side may be located outside the opening 21. In FIG. 1, the shape of the opening 21 is rectangular, and its long sides are along the direction in which the linear element 4 extends. The shape of opening 21 is not limited to a rectangle, and may be an oval shape such as an ellipse or an oval, and opening 21 is oriented such that its longitudinal direction is aligned with element 4. If element 4 is an inverted-L antenna or an inverted-F antenna, the ground side end of element 4 is positioned around the edge of opening 21. Furthermore, if element 4 is an inverted-F antenna, a feeder line can be connected to the middle part of element 4 by passing through opening 21.

[0011] By providing the opening 21 in the roof 2 directly below the element 4 as in this embodiment, it is possible to suppress a decrease in antenna gain even if the element 4 is disposed relatively close to the roof 2. In other words, it is possible to improve the performance of the antenna device 3 provided on the roof 2 of the vehicle 1. It is also possible to reduce the weight of the roof 2 (and therefore the weight of the vehicle 1).

[0012] <Comparative Example> Fig. 2 is a schematic side view of an antenna device for explaining a comparative example. Vehicle 10 according to the comparative example is provided with antenna device 30 on roof 20. In the comparative example, no opening is formed in roof 20. Antenna device 30 also includes an inverted-L-shaped antenna element 40 therein. The relationship between the height H of the tip portion of element 40 that is formed parallel or nearly parallel to roof 20 and the antenna sensitivity is as shown in Fig. 3.

[0013] FIG. 3 is a diagram showing the relationship between height H and antenna sensitivity. In the graph of FIG. 3, the horizontal axis represents frequency (MHz) and the vertical axis represents antenna sensitivity (dB). The short dashed line represents the antenna sensitivity based on simulation results when the height H of the element 40 is 50 mm, the long dashed line represents the antenna sensitivity when the height H of the element 40 is 40 mm, the dashed line represents the antenna sensitivity when the height H of the element 40 is 30 mm, the dashed line represents the antenna sensitivity when the height H of the element 40 is 20 mm, and the straight line represents the antenna sensitivity when the height of the element 40 is 10 mm. As shown in FIG. 3, the sensitivity improves as the height of the element 40 increases from the roof 20.

[0014] Fig. 4 is a diagram illustrating the antenna sensitivity of the antenna device according to the embodiment. In the graph of Fig. 4, the horizontal axis also represents frequency (MHz) and the vertical axis represents antenna sensitivity (dB). The broken line represents the antenna sensitivity when an opening 21 is provided in the roof 2. On the other hand, the solid line represents the antenna sensitivity when a roof 20 according to a comparative example has no opening. Note that the height H is the same in all cases. As shown in Fig. 4, by providing the opening 21, the antenna sensitivity can be improved even when the height H is the same.

[0015] <Embodiment 2> 5 is a schematic perspective view of an antenna device according to a second embodiment. Note that the same components as those in the above-described embodiments are given the corresponding reference numerals, and description thereof will be omitted. In this embodiment, the roof 2 has two openings 21A and 21B, and a connecting piece 22 is provided between them. In other words, the openings 21 (21A and 21B) are connected at the middle portions of their two long sides by the connecting piece 22. Furthermore, the openings 21A and 21B are arranged side by side in the direction in which the element 4 extends.

[0016] Depending on the relationship between the size of the opening 21 in the roof 2 and the wavelength (frequency) of electromagnetic waves, which are noise generated from equipment inside the vehicle 1, the opening may function as a slot antenna, for example. That is, the longitudinal length of the opening 21 may resonate with noise having a frequency equal to half the wavelength, thereby exciting the noise. In this embodiment, the longitudinal length of the opening 21 is changed by the connecting piece 22, and the intermediate portions of the long sides of the opening 21 are electrically connected to each other to achieve the same potential, thereby suppressing the excitation of noise in unnecessary frequency bands and reducing the impact on the antenna device 3. Note that the location of the connecting piece 22 can be appropriately changed depending on, for example, the frequency used by the equipment installed in the vehicle 1. That is, the longitudinal length of the opening 21 is divided into two lengths that are different from half the wavelength of the electromagnetic waves generated from the equipment installed in the vehicle 1. That is, the longitudinal length of the opening 21A and the opening 21B, which are parts of the opening 21 divided by the connecting piece 22, each have a length in the longitudinal direction (direction along the element 4) that is different from half the wavelength of the noise. In other words, by providing the connecting piece 22 at a position where the length of the longitudinal direction of the opening is not equal to half the wavelength of the noise emitted by the device, it is possible to avoid excitation of noise.

[0017] <Embodiment 3> FIG. 6 is a schematic perspective view of an antenna device according to a third embodiment. Note that the same components as those in the above-described embodiments are denoted by the corresponding reference numerals, and their description will be omitted. In this embodiment, the longitudinal length L2 of the opening 21 in the roof 2 is twice or approximately twice the length L1 of the element 4. For example, the length L1 of the element 4 is ¼ wavelength (λ / 4) of the frequency band transmitted or received by the element 4, and the longitudinal length L2 of the opening 21 is ½ wavelength (λ / 2). Note that the length L2 does not have to be exactly doubled, and may include an error of about ±10%. That is, the longitudinal length L2 of the opening 21 may be 1.8 to 2.2 times the length L1 of the element 4. Furthermore, the length L1 may be the length of the horizontally extending portion of the element 4, as shown in FIG. 6, or may be a length that further includes the portion bent toward the ground.

[0018] By setting the size relationship between the element 4 and the opening 21 as in this embodiment, the opening 21 can function as a slot antenna with a slot. That is, the opening 21 excites radio waves to be transmitted and received, and the sensitivity of the element 4 can be improved.

[0019] <Embodiment 4> 7 is a schematic perspective view of an antenna device according to a fourth embodiment. Note that the same components as those in the above-described embodiments are given the corresponding reference numerals, and their description will be omitted. In this embodiment, the opening 21 in the roof 2 is closed by a cover 23. The cover 23 is made of a filler that is easily permeable to radio waves, and is formed flush with the surface of the roof 2, for example. The material of the cover 23 is preferably a dielectric material that is permeable to radio waves, such as a resin.

[0020] According to this embodiment, it is possible to improve the sensitivity of the element 4 while also ensuring the waterproof function of the roof 2.

[0021] <Other> Although the embodiments have been described above, the present disclosure is not limited to these, and various modifications based on the knowledge of a person skilled in the art are possible without departing from the spirit of the embodiments. The configurations shown in embodiments 1 to 4 can be implemented in appropriate combinations. Furthermore, the present technology may be implemented not only in an antenna device, but also in a roof of a vehicle equipped with an antenna device, or a vehicle equipped with an antenna device and a roof. The antenna device can also be considered to include an opening provided in the roof. [Explanation of symbols]

[0022] 1: vehicle, 2: roof, 21 (21A, 21B): opening, 22: connecting piece, 23: cover 3: Antenna device, 4: Antenna element

Claims

1. An antenna device to be installed on the roof of a vehicle, an antenna element extending at least partially along the roof; An opening is provided in the sheet metal constituting the roof along the antenna element so as to surround the antenna element in a top view of the roof seen from above in a normal direction of the surface of the roof. Antenna device.

2. the antenna element is a linear conductor, The metal plate is provided with the rectangular opening along the linear conductor. The antenna device according to claim 1 .

3. the opening has one or more connecting pieces that electrically connect the intermediate portions of the two long sides; The opening is divided into two or more sections in the longitudinal direction by the connecting piece. The antenna device according to claim 2 .

4. The length in the longitudinal direction of each of the two or more portions of the opening divided by the connecting piece is set to a length different from the wavelength of the electromagnetic waves of noise generated from the equipment provided in the vehicle. The antenna device according to claim 3 .

5. the antenna element is a linear conductor, The length of the opening in the direction in which the conductor extends is twice the length of the antenna element. The antenna device according to claim 1 .

6. The opening is closed by a cover made of a dielectric material having radio wave transparency. The antenna device according to claim 1 .

7. A vehicle comprising the antenna device according to any one of claims 1 to 6.

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