Antenna system for vehicle

Abstract

Provided is a vehicle antenna system with high transceiving efficiency. A vehicle antenna system (100) includes an antenna (40) installed on a vehicle (20) and capable of transceiving a prescribed frequency band. The antenna (40) is installed so that an elevation angle with respect to a horizontal plane increases within a prescribed angle range according to a height of a communication frequency band.

Description

Technical Field

[0001] This invention relates to an antenna system for vehicles. Background Technology

[0002] In recent years, there has been a trend to expand high-speed and high-capacity communication infrastructure by using radio waves in frequency bands ranging from 4G LTE (Long Term Evolution) (700MHz band) to 5G (sub-6GHz, quasi-millimeter wave (20GHz-30GHz), and millimeter wave (30GHz-300GHz)). Furthermore, V2X (Vehicle to Everything), anticipated as a vehicle-to-everything (V2X) communication technology based on 5G for both vehicle-to-everything and road-to-road communication, is expected to have multiple applications.

[0003] The deployment of wireless communication systems for vehicles is rapidly progressing, and research is underway on vehicles equipped with such systems, as well as antennas mounted on these vehicles capable of transmitting and receiving radio waves in the aforementioned frequency bands (e.g., Patent Documents 1 and 2). For example, Patent Document 1 discloses a vehicle in which RF modules with multiple antennas are mounted on the front and rear bumpers, and a wireless communication system capable of transmitting and receiving radio waves across the entire horizontal plane is installed. Patent Document 2 discloses a vehicle antenna capable of transmitting and receiving high-frequency radio waves such as microwaves and millimeter waves.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: US Patent No. 10,516,429

[0007] Patent Document 2: International Publication No. 2019 / 208453 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] The frequency bands of radio waves transmitted and received by antennas mounted on vehicles are becoming increasingly wider. Therefore, vehicle-mounted antennas are required to perform efficient transmission and reception across the entire corresponding frequency band. In particular, vehicles equipped with such antennas sometimes face limitations in antenna installation location due to their construction, necessitating the installation of antennas with high transmit power and high receive sensitivity.

[0010] In view of the above problems, the purpose of this invention is to provide a vehicle antenna system with high transmission and reception efficiency.

[0011] Technical solutions for solving the problem

[0012] One aspect of the present invention relates to a vehicle antenna system comprising a first antenna mounted on a vehicle and capable of transmitting and receiving radio waves in a specified frequency band, the first antenna being mounted such that its elevation angle relative to the horizontal plane increases within a specified angular range depending on the height of the communication frequency band.

[0013] In the aforementioned vehicle antenna system, the first antenna may be mounted on a first part of the vehicle, and the vehicle antenna system may also include a second antenna mounted on a second part of the vehicle. The first antenna may be mounted at a first elevation angle relative to the horizontal plane within a predetermined angle range. The communication band of the second antenna may be higher than that of the first antenna. The second antenna may be mounted at a second elevation angle relative to the horizontal plane within the predetermined angle range and greater than the first elevation angle.

[0014] In the aforementioned vehicle antenna system, the communication band of the first antenna may partially overlap with the communication band of the second antenna, the first elevation angle may be determined based on the frequency at which the first antenna achieves its maximum gain, and the second elevation angle may be determined based on the frequency at which the second antenna achieves its maximum gain.

[0015] In the aforementioned vehicle antenna system, the first antenna and the second antenna may also be antennas of the same shape.

[0016] In the above-described vehicle antenna system, the antenna conductor of at least one of the first antenna and the second antenna may also be three-dimensional.

[0017] In the aforementioned vehicle antenna system, at least one of the first antenna and the second antenna may be installed with its radiating surface facing the interior glass of the vehicle.

[0018] In the aforementioned vehicle antenna system, at least one of the first antenna and the second antenna may be mounted with its radiating surface substantially parallel to the plane of the glass.

[0019] In the aforementioned vehicle antenna system, the glass may also include at least one of a front windshield, a rear windshield, and side window glass.

[0020] In the above-described vehicle antenna system, the angle difference between the radiation direction of the first antenna and the radiation direction of the second antenna, as observed from the vertical direction of the vehicle, may be 150° to 180°.

[0021] In the aforementioned vehicle antenna system, the first part and the second part may also be a combination of the inner surface side of the front windshield and the inner surface side of the rear windshield.

[0022] In the aforementioned vehicle antenna system, the specified angle range may also be 0° to 45°.

[0023] In the aforementioned vehicle antenna system, the specified frequency band may also be 700MHz to 6GHz.

[0024] Invention Effects

[0025] According to one aspect of the present invention, a vehicle antenna system with high transmission and reception efficiency can be provided. Attached Figure Description

[0026] Figure 1 This is a perspective view of a vehicle equipped with the vehicle antenna system according to the first embodiment.

[0027] Figure 2 This is an enlarged view of the antenna according to the first embodiment.

[0028] Figure 3 This is a graph showing the measurement results for the characteristics of the antenna.

[0029] Figure 4 This is a diagram used to illustrate an example of the antenna according to the first embodiment being installed in a vehicle.

[0030] Figure 5 This is a diagram used to illustrate an example of the antenna according to the first embodiment being installed in a vehicle.

[0031] Figure 6 This is a diagram showing an example of a section where an antenna is installed.

[0032] Figure 7 This is a diagram illustrating an example of the antenna involved in Variation 2.

[0033] Figure 8 This is a perspective view of a vehicle equipped with the vehicle antenna system according to the second embodiment.

[0034] Figure 9 This is a diagram used to illustrate an example of the antenna according to the second embodiment being installed in a vehicle. Detailed Implementation

[0035] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments. Furthermore, for clarity, the following descriptions and drawings have been appropriately omitted and simplified. In addition, in each drawing, the same elements are labeled with the same reference numerals, and repeated descriptions are omitted as necessary. Furthermore, in each embodiment, deviations in parallel, horizontal, vertical, and other directions are permitted to a degree that does not impair the effects of the present invention. Figure 1The right-handed xyz rectangular coordinate system shown in other figures is a convenient coordinate system for illustrating the positional relationships of constituent elements. Typically, the positive z-axis is vertically upward, and the xy plane is horizontal; this is common across the figures.

[0036] (First Implementation)

[0037] <Structure Example of an Antenna System for Vehicles>

[0038] use Figure 1 Here, a structural example of the vehicle antenna system 100 according to the first embodiment will be described. Figure 1 This is a perspective view of a vehicle equipped with the vehicle antenna system according to the first embodiment.

[0039] The vehicle antenna system 100 is an antenna system installed on the vehicle 20. The vehicle antenna system 100 includes an antenna 40. The antenna 40 is installed as part of the vehicle 20. The antenna 40 is installed, for example, near a glass panel 30 installed on the vehicle 20, with its radiating surface facing the glass panel 30. However, as long as it is a dielectric material, it is not limited to the vicinity of glass; it can also be near resin. Examples of resin in the vehicle 20 include aerodynamic components such as resin doors (not shown) and rear spoilers. The glass panel 30 is, for example, the windshield of the vehicle 20. The glass panel 30 is installed relative to the horizontal plane at a predetermined setting angle θ1 to the window frame (not shown) of the vehicle 20. Alternatively, the glass panel 30 can also be a rear windshield or a side window. In the following description, "glass panel 30" will sometimes be referred to simply as "glass 30".

[0040] Antenna 40 is, for example, an antenna module capable of transmitting and receiving radio waves in a specified frequency band. Alternatively, antenna 40 can also be a glass-printed antenna with a planar conductor pattern formed on the main surface of the glass plate 30. The specified frequency band is the frequency band corresponding to antenna 40. The specified frequency band can be a band from 4G LTE to 5G, for example, a band from 700MHz to 6GHz.

[0041] <Example of antenna structure>

[0042] Next, use Figure 2 An example of the structure of the antenna 40 used in the vehicle antenna system 100 according to the first embodiment will be described. Figure 2 This is an enlarged view of the antenna used in the vehicle antenna system according to the first embodiment. For example... Figure 2 As shown, antenna 40 is an antenna with a three-dimensional antenna conductor. Antenna 40 includes conductor plate 50, conductor plate 60, and conductor plate 70.

[0043] The conductor plate 50 is provided with a power supply section 81 with the conductor plate 50 as a ground reference. The power supply section 81 represents the power supply point of the antenna 40. The power supply section 81 is provided between end 53 and end 54 in the long side direction of the conductor plate 50. The conductor plate 50 has: a first plate surface 52 extending from the power supply section 81 toward end 53; and a second plate surface 51 extending from the power supply section 81 toward end 54.

[0044] The conductor plate 60 has: an end 63 connected to the power supply section 81; and an end 64 located on the opposite side of the end 63 and in a direction away from the conductor plate 50. The conductor plate 60 has a surface 61 configured to increase in width from the end 63 toward the end 64. The surface 61 is preferably inclined in a direction less than ±90° relative to a direction parallel to the conductor plate 50. In particular, the direction parallel to the conductor plate 50 is preferably within ±45° relative to the short side direction of the conductor plate 50, more preferably within ±20°, further preferably within ±5°, and most preferably aligned with the short side direction. Furthermore, the conductor plate 60 may have a portion where its width increases from the end 63 toward the end 64, or it may have a portion where the width remains constant from the end 63 toward the end 64, or a portion where the width narrows. Additionally, the conductor plate 60 preferably does not have a portion where its width narrows from the end 63 toward the end 64. Moreover, the conductor plate 60 may be a flat shape without bends, but it may also be a three-dimensional shape with bends, as shown in the figure.

[0045] The conductor plate 60 has a plate surface 61 including an end 63 and a plate surface 62 including an end 64. The plate surface 62 is a portion that is bent at a bend 65 relative to the plate surface 61. By providing the bent plate surface 61, the distance (height) in the z-axis direction relative to the conductor plate 50 can be shortened compared to the unbent form.

[0046] The conductor plate 70 has an end 73, capacitively coupled to an end 64 of the conductor plate 60; and an end 74, connected to the conductor plate 50 on the end 53 side relative to the power supply section 81. The end 73 is capacitively coupled to the end 64 via a gap 80 having a spacing capable of capacitive coupling. The direction of the gap 80 forming the capacitive coupling can be parallel to the end 73 or any other direction. Furthermore, the capacitive coupling between the end 64 and the end 73 can also be achieved through other forms such as a comb-shaped structure or dielectric loading.

[0047] The conductor plate 70 has: an opposing portion 71, which is opposed to the surface 61 of the conductor plate 50 along the long side of the conductor plate 50; and an opposing portion 72, which is opposed to the first surface 52 of the conductor plate 50 in a parallel direction. The opposing portion 72 is a portion bent at a bend 75 relative to the opposing portion 71. The opposing portion 72 includes an end 73, and the opposing portion 71 includes an end 74.

[0048] The conductor plate 60 of the antenna 40 is connected at its end 63 to a power supply section 81 grounded based on the conductor plate 50. The width of the plate surface 61 is formed to expand as it moves away from the conductor plate 50. By setting the length of the outer edge portion of the plate surface 61 (e.g., the curved portion extending from the end 63), the conductor plate 60 is made to have an electrical length that operates within the desired frequency range, thereby enabling the conductor plate 60 to function as a radiating element of a UWB (Ultra Wide Band) antenna capable of receiving radio waves over a wide frequency range.

[0049] On the other hand, conductor plate 60 is connected at end 63 to power supply unit 81 with conductor plate 50 as ground reference, and end 64 of conductor plate 60 is capacitively coupled to end 73 of conductor plate 70. Therefore, conductor plate 60 also functions as a power supply element that supplies power to conductor plate 70 via capacitive coupling. Furthermore, conductor plate 70 is connected to conductor plate 50 at end 74. Therefore, through capacitive coupling between conductor plate 60 and conductor plate 70, conductor plates 50 and 70, which are combined, are excited as a radiating element powered by conductor plate 60 via capacitive coupling. Therefore, by setting the length of each conductor of conductor plate 70 and conductor plate 50, conductor plates 50 and 70 can have electrical lengths that operate within a desired frequency range, thereby enabling conductor plates 50 and 70 to function as radiating elements that operate at a resonant frequency different from that of conductor plate 60.

[0050] Thus, antenna 40 has a first antenna that operates not only in a first operating mode where conductor plate 60 acts as a radiating element, but also in a second operating mode where conductor plate 60 acts as a power supply element and conductor plates 50 and 70 act as radiating elements. That is, conductor plates 50 and 70 can resonate at a resonant frequency different from the resonant frequency of conductor plate 60, thus easily achieving a wideband of transmit and receive frequencies for antenna 40. In the first operating mode, antenna 40 resonates with the current ib flowing through conductor plate 60 and the current ic flowing through conductor plate 70; in the second operating mode, it resonates with the current ia flowing through conductor plates 50 and 70.

[0051] For example, conductor plate 60 has a first electrical length Le1 that resonates at a first operating frequency f1, and conductor plates 50 and 70 have a second electrical length Le2 that resonates at a second operating frequency f2 that is lower than the first operating frequency f1. Thus, conductor plates 50 and 70 can resonate at a resonant frequency lower than the lowest-order resonant frequency of conductor plate 60.

[0052] For example, by setting the first electrical length Le1 to a quarter wavelength of the first operating frequency f1, the conductor plate 60 can be miniaturized, and the conductor plate 60 can be made to resonate at the first operating frequency f1. Additionally, for example, by setting the second electrical length Le2 to a quarter wavelength of the second operating frequency f2, the conductor plates 50 and 70 can be miniaturized, and the conductor plates 50 and 70 can be made to resonate at the second operating frequency f2.

[0053] The first electrical length Le1 is equivalent to the length obtained by taking into account the dielectric constant, thickness, etc. of the substrate that is in contact with or close to the conductor plate 60, along the shortest conductor length from end 63 to end 64. The second electrical length Le2 is equivalent to the length obtained by taking into account the dielectric constant, thickness, etc. of the substrate that is in contact with or close to the conductor plates 50 and 70, along the shortest conductor length from end 73 through end 74 to end 54.

[0054] Furthermore, the opposing portion 71 of the conductor plate 70 and the surface 61 of the conductor plate 60 are preferably separated by a quarter wavelength of electrical length from the first operating frequency f1. Thus, the antenna 40 has a structure in which the surface 61 through which the current ib flows and the opposing portion 71 through which the current ic (which has a phase opposite to the current ib) flows are separated by a quarter wavelength and grounded to the conductor plate 50. Therefore, like an array antenna or a Yagi antenna, the directivity of the antenna 40 is directed towards the end 54 side in the long side direction of the conductor plate 50. When the opposing portion 71 of the conductor plate 70 is parallel to the surface 61 of the conductor plate 60, it is more preferable that the directivity of the antenna 40 is directed towards the end 54 side in the long side direction of the conductor plate 50.

[0055] Furthermore, the conductor plate 70 has an opposing portion 72 opposite to the first plate surface 52 of the conductor plate 50. By providing the opposing portion 72, the directional adjustment of the antenna 40 becomes easier. It is more preferable that the directional adjustment becomes easier when the opposing portion 72 is parallel to the first plate surface 52 of the conductor plate 50. In addition, by bending the conductor plate 70, the height of the antenna 40 can be suppressed compared to the unbent method.

[0056] When the shape of the surface 61 of the conductor plate 60 is symmetrical about an imaginary line passing through the power supply section 81 in a direction perpendicular to the plane of the conductor plate 50, it is preferable to make the directivity of the antenna 40 nearly symmetrical about a direction perpendicular to the plane of the conductor plate 50. Furthermore, the conductor plate 60 may have a semi-circular surface 61, for example. However, the shape of the surface 61 is not limited to a semi-circular shape; it may also be other shapes such as an inverted triangle or a semi-ellipse. Additionally, slots may be formed in the conductor plate 60.

[0057] The conductor plate 60 can also be bent so that end 64 is close to end 63, thereby suppressing the height of the antenna 40. It is preferable that the conductor length from end 63 to end 64 is 100 mm or less, and more preferably 70 mm or less, in order to suppress the height of the antenna 40.

[0058] The end 63 located at the bottom of the plate 61 is connected to the power supply unit 81. The end 63 can be directly connected to the power supply unit 81, or it can be connected to the power supply unit 81 via capacitive coupling or the like.

[0059] When the power supply unit 81 is located at the center of the conductor plate 50 in a direction parallel to the plate surface 61, it is preferable to make the directivity of the antenna 40 nearly symmetrical about the normal direction of the plate surface 61. Here, "center" refers to a range of ±10% from the center of the width of the conductor plate 50. Furthermore, the center is preferably within ±5% of the width, and more preferably at the center of the width.

[0060] One end of the coaxial cable is connected to the power supply unit 81 directly or indirectly via solder or a connector. The other end of the coaxial cable is connected, for example, to a device having at least one of a transmitting or receiving function.

[0061] exist Figure 2 In this configuration, the opposing portion 71 of the conductor plate 70 may also have an opening 76. By having an opening 76, the material of the opposing portion 71 can be reduced, thus suppressing the weight of the antenna 40. By providing the opening 76 in the opposing portion 71, the opposing portion 71 thus has walls 71a, 71b, and 71c surrounding the opening 76. Walls 71a and 71b are located on both sides of the opening 76. Wall 71a is connected to the end 53 of the conductor plate 50 at its end 74a, and wall 71b is connected to the end 53 of the conductor plate 50 at its end 74b. Furthermore, wall 71c is connected to the bend 75 and also to walls 71a and 71b.

[0062] In addition, Figure 2 In this configuration, antenna 40 can also be a structure in which the second antenna 82 is disposed on the second plate surface 51 of conductor plate 50. By allowing the power supply line 83, which is connected to the power supply section of the second antenna 82, to pass through the opening 76, the influence of high-frequency current near the power supply line 83 on the impedance and radiation characteristics of antenna 40 can be suppressed. A duplexer can also be provided that connects to the power supply section 81 of conductor plate 60 and the power supply section of the second antenna 82.

[0063] <Antenna Installation Example>

[0064] Next, before describing the installation example of antenna 40 in vehicle 20, the characteristics of antenna 40 will be explained. First, as a premise, Patent Document 2 discloses that the radiating surface of the antenna is preferably set within a range of 90° ± 15° relative to the horizontal plane. However, as mentioned above, the frequency band of radio waves transmitted and received by antennas mounted on vehicles is becoming increasingly wider. In other words, there is a tendency to install one or more antennas (groups) corresponding to broadband frequencies in vehicles. Therefore, it is necessary to configure the antenna in the vehicle to correspond to the communication frequency band used for communication in the frequency band corresponding to the antenna. Therefore, in order to understand the characteristics of the antenna, the inventors of this application measured the characteristics of the antenna installed in the vehicle and studied an antenna installation example corresponding to the characteristics of the antenna.

[0065] Furthermore, the communication frequency band is the frequency band used for communication between the antenna 40 and a wireless communication device such as a wireless base station that communicates by transmitting and receiving waves. In the case where the wireless communication device communicating with the antenna 40 is, for example, an LTE wireless base station, the communication frequency band is the 700MHz to 3500MHz band. Moreover, when the antenna 40 communicates with, for example, an LTE wireless base station in the 700MHz band, the communication frequency band is the 700MHz band. Additionally, when the wireless communication device communicating with the antenna 40 is, for example, a 5G (sub-6) wireless base station, the communication frequency band is the 3600MHz to 4600MHz band. Thus, the communication frequency band is the frequency band supported by the antenna 40 used for communication between the antenna 40 and the corresponding wireless communication device.

[0066] The inventors of this application are described below. Figure 6 The antenna was installed at locations such as antenna 40 or antenna 90 (described later), and the RSRP (Reference Signal Received Power) was measured through driving tests. Furthermore, the inventors of this application measured the directivity of the antenna and calculated the average gain in the azimuth direction at various elevation angles (0°, 10°, 20°, 30°) (hereinafter referred to as "average gain"). The results showed that as the frequency increased, the correlation between the average gain at high elevation angles and the RSRP measurement results strengthened. Based on this result, it is anticipated that the higher the frequency, the better the transmit / receive performance of the antenna with the maximum gain at high elevation angles. Moreover, it is anticipated that the antenna shape is not limited to antenna 40 or antenna 90; as long as the antenna is capable of transmitting and receiving within the specified frequency band, the same performance can be obtained.

[0067] Figure 3 Is towards Figure 6 The average gain at each elevation angle and frequency is calculated when the antenna is installed at position Rr_R with a range of 40°. From Figure 3It is understood that antenna 40 is equivalent to the antenna described above that has the maximum gain at high elevation angles as the frequency increases. Therefore, the inventors of this application conclude that optimal transmission and reception performance can be obtained by mounting antenna 40 at the Rr_R position. Furthermore, in this specification, "elevation angle of antenna 40" is described as the angle between the horizontal plane and the radiating surface of antenna 40. For example, when the radiating surface of antenna 40 is parallel to the horizontal plane, the elevation angle of antenna 40 is 0°; when the direction of the radiating surface of antenna 40 is the zenith direction, the elevation angle of antenna 40 is 90°. "Elevation angle of antenna 40" means "elevation angle of antenna 40 relative to the horizontal plane" or "elevation angle of the radiating surface of antenna 40 relative to the horizontal plane," and this will also be the case in the following description. Additionally, in the following description, "elevation angle of antenna 40 relative to the horizontal plane" or "elevation angle of the radiating surface of antenna 40 relative to the horizontal plane" will sometimes be described as "elevation angle of antenna 40." Here, measurements were performed by changing the installation angle at four points: 0°, 10°, 20°, and 30°, for the elevation angle of the radiating surface of antenna 40. Furthermore, antenna 40 is designed to transmit and receive radio waves in a wide bandwidth from at least 900MHz to 3500MHz.

[0068] Figure 3 The first column from the left in the table represents the frequency at which antenna 40 is used for communication. Figure 3 The first row from the top and the second to fifth columns from the left in the diagram represent the antenna's elevation angle of 40°. Figure 3 The second to fifth rows from the top and the second to fifth columns from the left in the diagram represent the antenna gain of antenna 40. Figure 3 The first column from the right in the table represents the elevation angle (peak EL) that yields the highest antenna gain for antenna 40 at the four points of 0°, 10°, 20°, and 30° for each communication frequency of antenna 40.

[0069] Next, use Figure 4 A structural example of the vehicle antenna system 100 and an example of the installation of the antenna 40 onto the vehicle 20 will be described. Figure 4 This is an explanatory diagram of an example of antenna installation in a vehicle antenna system according to the first embodiment, and is a partial enlarged view of the vehicle from the side.

[0070] like Figure 4 As shown, antenna 40 is mounted on the interior side of the glass panel 30 of vehicle 20. Antenna 40 is mounted, for example, at the upper center of glass panel 30. Alternatively, antenna 40 can be mounted at the lower center of glass panel 30, or at any location near either the left or right end of glass panel 30.

[0071] Antenna 40 is mounted facing the interior side of the glass panel 30 of vehicle 20. Antenna 40 can also be mounted with its radiating surface approximately parallel to the plane of the glass panel 30. "Approximately parallel" means not only that the radiating surface of antenna 40 is parallel to the glass panel 30, but also that the angle between the radiating surface of antenna 40 and the glass panel 30 is, for example, less than 5°. Antenna 40 is configured to adjust its elevation angle relative to the horizontal plane and is mounted at the height of the communication band indicated in the specified frequency band, with the elevation angle of antenna 40 relative to the horizontal plane increasing within a specified angle range. In other words, antenna 40 is mounted such that, within a specified angle range, the elevation angle of the radiating surface of antenna 40 relative to the horizontal plane increases according to the height of the communication band. The specified frequency band can be, for example, a band from 4G LTE to 5G, or a band from 700MHz to less than 6GHz (the so-called "5G-sub6"). In addition, the specified angle range can be 0° to 45°, 0° to 35°, or 0° to 30°.

[0072] Figure 4 The arrow pointing from antenna 40 toward the outside of the vehicle indicates the direction of transmission of radio waves from antenna 40 (the direction of radiation from the radiating surface). Conversely, the opposite direction of the arrow indicates the direction of reception of radio waves toward antenna 40. Figure 4 The region R1, indicated by the dashed line, roughly represents the radiation pattern (main lobe) of the antenna 40. Additionally, Figure 4 The arrow shown corresponds to the center direction of the main lobe. The dashed line represents a plane parallel to the horizontal plane. The angle θ3 formed by the dashed line and the arrow pointing from antenna 40 outwards from the vehicle corresponds to the elevation angle of antenna 40. In the case of a relatively low communication frequency band, such as 900MHz, antenna 40 is mounted such that the elevation angle (angle θ3) of antenna 40 is smaller. On the other hand, in the case of a relatively high communication frequency band, such as several GHz used in 5G, antenna 40 is mounted such that the elevation angle (angle θ3) of antenna 40 is higher within a specified angle range.

[0073] Next, use Figure 5 The details of the installation example of antenna 40 in vehicle 20 are explained. Figure 5 This is an explanatory diagram illustrating an example of antenna installation in a vehicle antenna system according to the first embodiment.

[0074] Antenna 40 is mounted on glass plate 30 via mounting components such as antenna brackets (not shown). Antenna 40 is mounted such that at least one of conductor plate 60 and conductor plate 70 is close to glass plate 30 at a distance D1. Antenna 40 is mounted such that conductor plate 50 is close to glass plate 30 at a distance D2. Thus, by bringing at least one of conductor plate 60 and conductor plate 70 close to glass plate 30 at a distance D1, a shortening effect due to glass plate 30 as a dielectric is achieved, enabling miniaturization of antenna 40. Furthermore, by bringing conductor plate 50 close to glass plate 30 at a distance D2, a shortening effect due to glass plate 30 as a dielectric is achieved, enabling miniaturization of antenna 40. By making distances D1 and D2 different, antenna 40 can be formed as a three-dimensional antenna having elements including components in a direction perpendicular to the plane of glass plate 30.

[0075] exist Figure 5 In the illustration, the opposing portion 72 of the conductor plate 70 is mounted parallel to the glass plate 30. However, the antenna 40 can also be configured to adjust the distance between the opposing portion 72 of the conductor plate 70 and the glass plate 30. If the distance between the opposing portion 72 of the conductor plate 70 and the glass plate 30 can be adjusted, the elevation angle (direction of the radiating surface of the antenna 40) can also be adjusted. For example, if the antenna 40 is mounted by rotating it with the power supply unit 81 as a reference, such that the distance between the opposing portion 72 and the glass plate 30 is closer and the second plate surface 51 is farther away from the glass plate 30, the elevation angle of the antenna 40 can be reduced compared to the state where the antenna 40 and the glass plate 30 are approximately parallel. Alternatively, if the antenna 40 can be rotated with the power supply unit 81 as a reference, such that the distance between the opposing portion 72 and the glass plate 30 is farther and the second plate surface 51 is closer to the glass plate 30, the elevation angle of the antenna 40 can be increased compared to the state where the antenna 40 and the glass plate 30 are approximately parallel. In this way, the antenna 40 can also be mounted to rotate with the power supply unit 81 as a reference, and by adjusting the elevation angle to correspond to the communication frequency band, the optimal antenna gain can be achieved.

[0076] Furthermore, the directivity of a planar (two-dimensional) antenna that does not have a component in the direction perpendicular to the plane of the glass plate 30 is easily enhanced in the normal direction of the glass plate 30. In contrast, the antenna 40 includes elements having a component in the direction perpendicular to the plane of the glass plate 30, so the direction of enhanced directivity of the antenna 40 is easily tilted closer to the horizontal plane relative to the normal direction of the glass plate 30. Therefore, in the vehicle antenna system according to the first embodiment, the directivity of the antenna 40 in the direction parallel to the horizontal plane (horizontal direction) is improved, thus further increasing the antenna gain (operating gain) in the horizontal direction.

[0077] Furthermore, the antenna 40 has a bent element. When comparing antennas of the same length, the element with more bends is better able to suppress height compared to an unbent antenna. By bending the element in two or more places, the height (D2-D1) can be easily reduced while ensuring the specified antenna length. Therefore, the antenna 40 in the vehicle antenna system according to the first embodiment can prevent large protrusions from the interior surface of the glass panel 30, and is less likely to become an obstruction for occupants.

[0078] In antenna 40, the opposing portion 72 of conductor plate 70 and the second plate portion 51 of conductor plate 50 are connected via relatively strong capacitive coupling through a conductor plate 60 having a plate surface 61 formed in a direction perpendicular to the plane of glass plate 30. With this connection, the opposing portion 72 and the second plate portion 51 are not opposed, or the opposing conductor portions are relatively small (narrow), thus the capacitive coupling between the opposing portion 72 and the second plate portion 51 is less likely to be strengthened. Therefore, the antenna 40 in the vehicle antenna system according to the first embodiment can achieve good impedance matching.

[0079] In addition, regarding improving horizontal directionality, such as Figure 5 As shown, distance D1 is preferably shorter than distance D2. Alternatively, distance D1 can also be 0. When distance D1 is 0, at least one of conductor plate 60 and conductor plate 70 is in contact with the inner surface of glass plate 30.

[0080] Antenna 40 is mounted above the interior side of the vehicle relative to glass plate 30. Angle α represents the angle between the opposing portion 72 and the plate surface 61, and angle β represents the angle between the plate surface 61 and the conductor plate 50. Angle α is an angle greater than 0° and less than 180° (e.g., 90°), and angle β is also an angle greater than 0° and less than 180° (e.g., 90°). Angles α and β are preferably right angles, but can also be angles other than right angles (e.g., 45°). Angles α and β can be the same angle or different angles.

[0081] Antenna 40 is suitable for transmitting and receiving radio waves in the UHF (Ultra High Frequency) and SHF (Super High Frequency) bands. For example, antenna 40 is suitable for transmitting and receiving radio waves in three of the multiple frequency bands used by LTE (Long Term Evolution) (0.698GHz–0.96GHz, 971GHz–2.97GHz, and 2.4GHz–2.69GHz). Additionally, antenna 40 is suitable for transmitting and receiving radio waves in the 5G (sub-6GHz) band. Furthermore, antenna 40 is also suitable for transmitting and receiving radio waves in the ISM (Industry Science Medical) band. The ISM band includes 0.863GHz–0.870GHz (Europe), 0.902GHz–0.928GHz (USA), and 2.4GHz–2.5GHz (globally used). As a communication standard that uses the 2.4GHz frequency band, which is one of the ISM frequency bands, there are wireless LANs (Local Area Networks) based on the DSSS (Direct Sequence Spread Spectrum) method of IEEE 802.91b, Bluetooth (registered trademark), and some FWA (Fixed Wireless Access) systems.

[0082] As explained above, the antenna 40 of the vehicle antenna system 100 is mounted such that the elevation angle of the radiating surface relative to the horizontal plane increases within a specified angle range depending on the height of the communication frequency band. Thus, by mounting the antenna 40 at an elevation angle corresponding to the communication frequency band, optimal antenna gain can be achieved. Therefore, the vehicle antenna system 100 according to the first embodiment can provide a vehicle antenna system with high transmit / receive efficiency corresponding to the frequency band of the communication target.

[0083] (Variation Example 1)

[0084] In the vehicle antenna system according to the first embodiment, the case where the antenna 40 is installed close to the glass panel 30 that serves as the windshield has been described. However, the part where the antenna 40 is installed may also be a part other than the windshield. Figure 6 An example of the part where antenna 40 is installed will be described.

[0085] In addition to being configured near the upper Fr_R and Fr_L of the front windshield, antenna 40 can also be configured near the side window RQ_R, side window RQ_L, the upper right side Rr_R of the rear windshield, or the upper left side Rr_L of the rear windshield. Furthermore, antenna 40 can also be mounted on the instrument panel IP, spoiler SP, roof of the vehicle 20, or on the shark fin antenna on the roof of the vehicle 20. Additionally, although in Figure 6 Although not shown in the figure, the antenna 40 can also be installed on the front bumper or the rear bumper of the vehicle 20.

[0086] (Variation Example 2)

[0087] In the first embodiment described above, the antenna provided by the vehicle antenna system 100 is described as an antenna module, but the antenna provided by the vehicle antenna system 100 may also be replaced with a planar (two-dimensional) printed antenna.

[0088] use Figure 7 The structure of the antenna 90 in the vehicle antenna system 100 involved in Modification Example 2 will be described. Figure 7 This is an enlarged top view showing an example of an antenna in the vehicle antenna system 100 according to Modified Example 2. The antenna 90 is an antenna assembled to the glass plate 30 by printing, embedding, pasting, etc. The antenna 90 is configured to include electrodes and antenna conductors provided on the glass plate 30 as planar conductor patterns.

[0089] Antenna 90 includes a power supply electrode 91, a grounding electrode 92, and antenna elements 93-97. The power supply electrode 91 is a power supply point (positive-side power supply section) electrically connected to the internal conductor of a coaxial cable connected to antenna 90. The power supply electrode 91 can be, for example, rectangular in shape, with a length of 30 mm in the long side and a length of 20 mm in the short side. However, the shape of the power supply electrode 91 is not limited to a rectangular shape; it can also be circular or a polygon other than a rectangle. Furthermore, the lengths of the long and short sides of the power supply electrode 91 are not limited to the aforementioned lengths and can be appropriately adjusted.

[0090] The power supply electrode 91 is connected to the grounding electrode 92 via a resistor module element (not shown) and a connector (not shown). The antenna 90 forms a closed circuit through the power supply electrode 91, the grounding electrode 92, the resistor module element (not shown), and the connector (not shown).

[0091] The grounding electrode 92 is the negative-side power supply section and is installed separately from the power supply electrode 91. The grounding electrode 92 can be, for example, rectangular in shape, with a length of 40 mm in the long side and a length of 30 mm in the short side. However, the shape of the grounding electrode 92 is not limited to a rectangle; it can also be circular or a polygon other than a rectangle. Furthermore, the lengths of the long and short sides of the grounding electrode 92 are not limited to the aforementioned lengths and can be appropriately adjusted.

[0092] The grounding electrode 92 has a cutout 92N. The cutout 92N is formed in a location where no resistor module (not shown) or connector (not shown) is configured. The antenna 90 is configured to have a large area by widening the power supply electrode 91 and the grounding electrode 92, thus enabling it to transmit and receive wideband radio waves.

[0093] Furthermore, if the areas of the power supply electrode 91 and the grounding electrode 92 are too large, the strength of the glass plate 30 on which the antenna 90 is mounted will be insufficient, or deformation may occur due to the difference in heat absorption and stress between the glass and the metal. Therefore, the grounding electrode 92 is provided with a cutout 92N, which is configured to increase the width of the electrode while maintaining the strength of the glass plate 30.

[0094] Antenna element 93 is connected to power supply electrode 91 at connection point a and extends from connection point a in the negative z-axis direction to endpoint b. Antenna element 93 can be, for example, 4 mm long. Antenna element 93 constitutes antenna conductor α. Antenna element 94 is connected to power supply electrode 91 at connection point c and extends from connection point c in the negative z-axis direction to endpoint d. The distance from connection point c to endpoint d is longer than the distance from connection point a to endpoint b, for example, 82 mm. Antenna element 94 constitutes antenna conductor β. Figure 7 As shown, antenna elements 93 and 94 extend in a direction perpendicular to the xy plane, which is the horizontal plane. Therefore, antenna 90 has a structure that easily receives vertically polarized waves transmitted and received by antenna 90.

[0095] Antenna element 95 is connected to power supply electrode 91 at connection point e and extends from connection point e in the negative x-axis direction to connection point f. The length of antenna element 95 can be, for example, 96.8 mm. Antenna element 96 is connected to antenna elements 95 and 97 at connection point f. Antenna element 96 extends from connection point f to endpoint g, with connection point f as a reference, in the opposite direction to the extending direction of antenna element 97. When the angle between antenna elements 95 and 97 is angle θ2, it extends in the positive z-axis and negative x-axis direction such that the angle between antenna elements 95 and 96 is the angle obtained by subtracting angle θ2 from 180°. The length of antenna element 96 can be, for example, 28.1 mm. Antenna element 97 is connected to antenna elements 95 and 96 at connection point f and extends from connection point f to endpoint h in the negative z-axis and positive x-axis direction relative to antenna element 95 at an angle θ2. Angle θ2 can be, for example, 69°. The length of antenna element 97 can be, for example, 49.8 mm. Antenna elements 95-97 constitute the antenna conductor γ.

[0096] The antenna 90 has a pair of electrodes (power supply electrode 91 and ground side electrode 92) and multiple antenna elements 93 to 97, thereby enabling communication in multiple frequency bands within the frequency band of 700 MHz to 6 GHz.

[0097] Thus, even if the structure of the vehicle antenna system 100 is modified by replacing the antenna 40 of the first embodiment with the antenna 90 of Modified Example 2, the same effect as the first embodiment can be obtained. That is, by mounting the antenna 90 at an elevation angle corresponding to the communication frequency band, optimal antenna gain can be achieved. Therefore, the vehicle antenna system 100 of Modified Example 2, like the first embodiment, can be configured as a vehicle antenna system with high transmit and receive efficiency corresponding to the corresponding frequency band.

[0098] (Second Implementation)

[0099] Next, the second embodiment will be described. In the first embodiment, the vehicle antenna system 100 has a structure with one antenna 40. In the second embodiment, the vehicle antenna system 200 has a structure with two antennas. In addition, in this embodiment, the vehicle antenna system 200 has a structure with two antennas, but it may also have a structure with three or more antennas.

[0100] <Structure Example of an Antenna System for Vehicles>

[0101] use Figure 8 Here, a structural example of the vehicle antenna system 200 according to the second embodiment will be described. Figure 8 This is a perspective view of a vehicle equipped with the vehicle antenna system according to the second embodiment.

[0102] The vehicle antenna system 200 is an antenna system installed on a vehicle 20. The vehicle antenna system 200 includes an antenna 110 and an antenna 120. Antenna 110 is installed on a portion (first portion) of the vehicle 20, with its radiating surface facing the glass panel 30 installed on the vehicle 20. Antenna 120 is installed on a portion (second portion) of the vehicle, with its radiating surface facing the glass panel 30 installed on the vehicle 20. The first portion and the second portion can be located at the upper center of the glass panel 30. Alternatively, the first portion can be located to the left of the upper center of the windshield, and the second portion can be located to the right of the upper center of the windshield. In this embodiment, the glass panel 30 is described as the windshield of the vehicle 20, but it could also be the rear windshield or a side window. Furthermore, the first portion and the second portion can be any of the portions described in the variation 1 of the first embodiment, in addition to the windshield. Furthermore, the first and second parts can be located in the lower center of the windshield, or they can be located near either the left or right end of the windshield.

[0103] Antennas 110 and 120 can be Figure 2 The antenna module shown has a three-dimensional antenna conductor, but it can also be as follows: Figure 7 The image shows a printed antenna mounted on a glass surface. Antennas 110 and 120 can be the same antenna or different antennas. In other words, antennas 110 and 120 can be antennas of the same shape or antennas of different shapes. Furthermore, as a combination of multiple antennas of different shapes, the transmit and receive frequency bands of each antenna can be of the same specification or different specifications.

[0104] Antennas 110 and 120 are antennas capable of transmitting and receiving radio waves within a specified frequency band. The specified frequency band refers to the frequency band corresponding to antennas 110 and 120. This specified frequency band can be a band ranging from 4G LTE to 5G, or a band from 700MHz to less than 6GHz (the so-called "5G-sub6"). Antennas 110 and 120 are designed so that the frequencies at which they achieve maximum antenna gain are known during the design phase. The frequencies at which antennas 110 and 120 achieve maximum gain are designed to be included within the communication frequency band used by the communication employing antennas 110 and 120, respectively. Furthermore, in this embodiment, the frequency at which the antenna gain of antenna 110 is maximized is defined as frequency f5, and the frequency at which the antenna gain of antenna 120 is maximized is defined as frequency f6, and frequency f6 is described as a frequency higher than frequency f5.

[0105] <Antenna Installation Example>

[0106] Next, use Figure 9 An example of the installation of antennas 110 and 120 in vehicle 20 will be described. Figure 9 This is an explanatory diagram illustrating an example of antenna installation in a vehicle according to the second embodiment, and is related to... Figure 4 A magnified view of the corresponding vehicle from the side. Additionally, in Figure 8 In the diagram, antennas 110 and 120 are shown mounted at the same height, but... Figure 9 For convenience, the description assumes that the installation heights of antennas 110 and 120 are different.

[0107] At least one of antennas 110 and 120 can be mounted facing the interior side of the glass panel 30 of the vehicle 20. Furthermore, in the following description, antennas 110 and 120 will be described as being mounted facing the interior side of the glass panel 30 of the vehicle 20.

[0108] Antennas 110 and 120 are mounted at an elevation angle relative to the horizontal plane within a specified range. Figure 9 The arrows pointing from antennas 110 and 120 toward the outside of the vehicle indicate the direction of radio wave transmission from antennas 110 and 120. Conversely, the opposite direction of these arrows indicates the direction of radio wave reception from antennas 110 and 120. Figure 9 The dashed line indicates that region R3 roughly represents the radiation state of the radio waves from antenna 110, and region R4 roughly represents the radiation state of the radio waves from antenna 120. Additionally, Figure 9 The arrows shown correspond to the center directions of each main lobe. A dashed line, illustrated as a through-antenna 110, represents a plane parallel to the horizontal plane. The angle θ4 formed by this dashed line and the arrow pointing outwards from antenna 110 corresponds to the elevation angle of antenna 110. Similarly, the angle θ5 formed by the dashed line, illustrated as a through-antenna 120, and the arrow pointing outwards from antenna 120 corresponds to the elevation angle of antenna 120.

[0109] The following describes an example of the installation of antennas 110 and 120, but in this embodiment, two installation examples based on the communication frequency band of antennas 110 and 120 will be described.

[0110] <Antenna Installation Example 1>

[0111] Installation Example 1 is an example where the communication bands of antenna 110 and antenna 120 do not overlap. Antenna 110 is installed with an elevation angle θ4 relative to the horizontal plane within a specified range. Furthermore, when the communication band of antenna 120 is higher than that of antenna 110, the elevation angle of antenna 120 relative to the horizontal plane is greater than angle θ4, and it is installed at an angle θ5 within a specified range. Figure 3As shown, the higher the frequency, the greater the elevation angle of the antenna relative to the horizontal plane, thereby increasing the antenna gain. Therefore, when the communication band of antenna 120 is higher than that of antenna 110 and the communication bands do not overlap, antenna 120 is installed on vehicle 20 with an elevation angle greater than that of antenna 110, based on the communication bands. In this way, without overlapping communication bands, by adjusting the elevation angles of antennas 110 and 120 to angles corresponding to the communication bands, a vehicle antenna system 200 with high transmission and reception efficiency can be achieved.

[0112] <Antenna Installation Example 2>

[0113] Installation Example 2 is an installation example where the communication band of antenna 110 overlaps with the communication band of antenna 120. Additionally, Installation Example 2 is an installation example where at least a portion of the communication bands of antenna 110 and antenna 120 overlap.

[0114] In this case, the elevation angles of antennas 110 and 120 are determined based on the frequency at which the antenna gain is maximized. Specifically, the elevation angle θ4 of antenna 110 is determined based on the frequency f5, which is the frequency at which the maximum gain of antenna 110 is achieved. Similarly, the elevation angle θ5 of antenna 120 is determined based on the frequency f6, which is the frequency at which the maximum gain of antenna 120 is achieved. Figure 3 As shown, the higher the frequency, the greater the elevation angle of the antenna relative to the horizontal plane, thereby increasing the antenna gain. Therefore, in Installation Example 2, the elevation angles of antennas 110 and 120 are adjusted to angles determined based on the frequency at which maximum gain is achieved, and antennas 110 and 120 are mounted on vehicle 20. In this way, even in cases of overlapping communication bands, by adjusting the elevation angles of antennas 110 and 120 to angles corresponding to the frequency at which maximum gain is achieved, a vehicle antenna system 200 with high transmission and reception efficiency can be realized.

[0115] <Antenna Installation Example 3>

[0116] Installation Example 3 illustrates the installation of antennas 110 and 120 of the vehicle antenna system 200 at different azimuth angles on the vehicle 20. For instance, by installing antennas 110 and 120 one by one on the inner surface of the front windshield and the inner surface of the rear windshield, the vehicle antenna system 200 can achieve the following: Figure 6 As shown, it transmits and receives radio waves in a specified frequency band within an azimuth angle of 0° to 360° centered on vehicle 20. That is, the first part and the second part mentioned here correspond to the combination of the inner surface side of the front windshield and the inner surface side of the rear windshield. In addition, the antennas 110 and 120 installed in the vehicle antenna system 200 can also be installed separately on the inner surface side of the two side windows.

[0117] Thus, if the vehicle antenna system 200 is installed on the vehicle 20 with antennas 110 and 120 facing different azimuth angles, and the difference in their azimuth angles is 150° to 180°, then it can transmit and receive radio waves in a specified frequency band within an azimuth angle range of 0° to 360° centered on the vehicle 20. In particular, it is common for the radiation directions of antennas 110 and 120 to be approximately equal to the normal direction of the radiation surface of each antenna. Furthermore, in the vehicle antenna system 200, the difference in azimuth angle that corresponds to the angle difference between the radiation directions of antenna 110 and antenna 120 when viewed from the vertical direction (Z-axis direction) is preferably 160° to 180°, more preferably 170° to 180°, and even more preferably 175° to 180°. Thus, the installation positions of antennas 110 and 120 can be determined by, for example, referring to... Figure 6 The antenna installation location.

[0118] Furthermore, the vehicle antenna system 200 can be equipped with four antennas, which are distributed one by one (a total of four) on the inner surface of the windshield, the inner surface of the rear windshield, and the inner surface of the two side windows. In this case, the elevation angle of each antenna installed at each location is adjusted to an angle corresponding to the frequency at which maximum gain is achieved, thereby enabling the vehicle antenna system 200 to achieve high transmission and reception efficiency.

[0119] As explained above, the antennas 110 and 120 of the vehicle antenna system 200 are mounted at elevation angles corresponding to the communication band or the frequency at which maximum gain is achieved, thus enabling the attainment of optimal antenna gain. Therefore, the vehicle antenna system 200 according to the second embodiment provides a vehicle antenna system with high transmit and receive efficiency.

[0120] The present invention has been described above based on the above embodiments, but the present invention is not limited to the structure of the above embodiments, and of course includes various modifications, alterations and combinations that can be made by those skilled in the art within the scope of the claims of this application.

[0121] This application claims priority based on Japanese Patent Application 2020-163395, filed on September 29, 2020, the entire disclosure of which is incorporated herein by reference.

[0122] Label Explanation

[0123] 20 vehicles;

[0124] 30 glass plates;

[0125] 40, 90, 110, 120 antennas;

[0126] 50, 60, 70 conductor plates;

[0127] 51. Second panel face;

[0128] 52 First panel face;

[0129] Ends of 53, 54, 63, 64, 73, 74, 74a, and 74b;

[0130] 61 and 62 panel surfaces;

[0131] 65° and 75° bends;

[0132] 71 and 72 are opposite parts;

[0133] 76. Opening section;

[0134] 71a, 71b, 71c wall sections;

[0135] 80 gap;

[0136] 81 Power Supply Department;

[0137] 82 Second antenna;

[0138] 83 Power supply line;

[0139] 91. Electrode for power supply;

[0140] 92. Grounding side electrode;

[0141] 92N incision site;

[0142] 93-97 antenna elements;

[0143] Antenna systems for 100 and 200 vehicles.

Claims

1. An antenna system for a vehicle, wherein, have: A first antenna, which is installed on a first part of the vehicle and is capable of transmitting and receiving radio waves in a specified frequency band; and A second antenna, which is installed in a second part of the vehicle and is capable of transmitting and receiving radio waves in a specified frequency band, The higher the communication frequency band of the first antenna, which is configured to transmit and receive in the range of 700MHz to 6GHz, the greater the elevation angle of the radiating surface of the first antenna relative to the horizontal plane, within a specified angle range of 0° to 45°. The first antenna is mounted at a first elevation angle relative to the horizontal plane within the specified angular range. The communication bandwidth of the second antenna is higher than that of the first antenna. The second antenna is installed at a second elevation angle relative to the horizontal plane within the specified angle range and greater than the first elevation angle.

2. The vehicle antenna system according to claim 1, wherein, The communication frequency band of the first antenna partially overlaps with the communication frequency band of the second antenna. The first elevation angle is determined based on the frequency at which the first antenna achieves its maximum gain. The second elevation angle is determined based on the frequency at which the second antenna achieves maximum gain.

3. The vehicle antenna system according to claim 1 or 2, wherein, The first antenna and the second antenna are antennas of the same shape.

4. The vehicle antenna system according to claim 1 or 2, wherein, The antenna conductor of at least one of the first antenna and the second antenna has a three-dimensional shape.

5. The vehicle antenna system according to claim 1 or 2, wherein, At least one of the first antenna and the second antenna is mounted with its radiating surface facing the interior glass of the vehicle.

6. The vehicle antenna system according to claim 5, wherein, At least one of the first antenna and the second antenna is mounted such that its radiating surface is substantially parallel to the plane of the glass.

7. The vehicle antenna system according to claim 5, wherein, The glass includes at least one of a front windshield, a rear windshield, and side window glass.

8. The vehicle antenna system according to claim 1 or 2, wherein, The angular difference between the radiation direction of the first antenna and the radiation direction of the second antenna, as observed from the vertical direction of the vehicle, is 150° to 180°.

9. The vehicle antenna system according to claim 8, wherein, The first part and the second part are a combination of the inner surface side of the front windshield and the inner surface side of the rear windshield.

Images