Vehicle-mounted antenna device

Abstract

An on-vehicle antenna device comprising a base, a case that, together with the base, forms accommodation space, and a first antenna that is accommodated in the accommodation space and that handles radio waves of a desired frequency band, wherein at least a portion of the first antenna is disposed in a position that is proximal to the case.

Description

Technical Field

[0001] The present invention relates to an in-vehicle antenna device.

Background Art

[0002] In recent years, development of an in-vehicle antenna device including an antenna corresponding to V2X (Vehicle to Everything: vehicle-to-vehicle communication, vehicle-to-roadside communication) has been carried out (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the antenna device disclosed in Patent Document 1, the antenna for V2X is disposed at a predetermined position behind in the antenna device. In such a case, the gain in the forward direction of the antenna for V2X may be significantly lower than the gain in the rear direction. Therefore, since the directivity of the antenna of Patent Document 1 deteriorates, the antenna device cannot appropriately respond to radio waves in a desired frequency band.

[0005] An example of an object of the present invention is to provide an in-vehicle antenna device that can appropriately respond to radio waves in a desired frequency band. Other objects of the present invention will become apparent from the description herein.

Means for Solving the Problems

[0006] One aspect of the present invention includes a base, a case that forms an accommodation space together with the base, and a first antenna accommodated in the accommodation space and corresponding to radio waves in a desired frequency band, and at least a part of the first antenna is disposed at a position close to the case. The in-vehicle antenna device is as described above. [Effects of the Invention]

[0007] According to one aspect of the present invention, an in-vehicle antenna device capable of appropriately responding to radio waves in a desired frequency band can be provided. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view of the vehicle-mounted antenna device 10. [Figure 2] Figure 2A shows an example of case 300 and ground plate 320. Figure 2B is a diagram illustrating the position of antenna 310 inside case 300. [Figure 3] This figure shows the directivity in the horizontal plane at a distance Da = 20 mm. [Figure 4] This figure shows the directivity in the horizontal plane at a distance Da = 50 mm. [Figure 5] This figure shows the relationship between distance Da and gain deviation. [Figure 6] Figure 6A shows an example of case 400 and base plate 420. Figure 6B is a diagram illustrating the position of antenna 410 inside case 400. [Figure 7] This figure shows the relationship between distance Db and gain deviation. [Figure 8] This is a diagram illustrating the position of antenna 30. [Figure 9] This is a diagram illustrating the position of antenna 31. [Figure 10] This figure shows the horizontal directivity of antennas 30 and 31. [Figure 11] This is a perspective view of the vehicle-mounted antenna device 11. [Figure 12] This is a diagram illustrating the position of antenna 34. [Figure 13] This figure shows the horizontal directivity of antennas 31 and 34. [Figure 14] This figure shows the horizontal directivity of the antenna 34 in the vehicle-mounted antenna device 11,X. [Figure 15]It is a diagram showing the directivity of the antenna 31 in the horizontal plane of the in-vehicle antenna device 11,X. [Figure 16] It is a perspective view of the in-vehicle antenna device 12. [Figure 17] It is a diagram for explaining the position of the antenna 37. [Figure 18] It is a perspective view of the in-vehicle antenna device 13. [Figure 19] It is a diagram for explaining the position of the antenna 512a. [Figure 20] It is a perspective view of the in-vehicle antenna device 14. [Figure 21] It is a diagram showing the directivity of the antenna 30 in the horizontal plane. [Figure 22] It is a perspective view showing the periphery of the substrate 41 of the in-vehicle antenna device 10. [Figure 23] It is a plan view showing the periphery of the substrate 41 of the in-vehicle antenna device 10. [Figure 24] It is a diagram for explaining another example of the antenna 31 and the case 22. [Figure 25] It is a diagram for explaining another example of the antenna 34. [Figure 26] It is a perspective view showing the periphery of the substrate 40 of the in-vehicle antenna device 11. [Figure 27] It is a plan view showing the periphery of the substrate 40 of the in-vehicle antenna device 11. [Figure 28] [[ID=)39]]It is a perspective view of the in-vehicle antenna device 15. [Figure 29] It is an explanatory diagram of the separation distance Dgv between the antenna 31 and the antenna 32. [Figure 30] It is a graph showing an example of the maximum axial ratio at an elevation angle of 90° when the separation distance Dgv is changed. [Figure 31] It is a graph showing an example of the maximum axial ratio at an elevation angle of 10° when the separation distance Dgv is changed. [Figure 32] It is a perspective view of the in-vehicle antenna devices 16, 17. [Figure 33] It is a perspective view of the in-vehicle antenna devices 18, 19. [Modes for carrying out the invention]

[0009] The following matters become clear from this specification and the accompanying drawings:

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The same or equivalent components, members, etc. shown in each drawing are denoted by the same reference numerals, and redundant explanations will be omitted as appropriate.

[0011] =====Execution===== <<<Overview of the vehicle-mounted antenna device 10 (first embodiment)>>> Figure 1 shows the configuration of an in-vehicle antenna device 10, which is a first embodiment of the present invention. Figure 1 is a perspective view of the in-vehicle antenna device 10 with the case 22 removed in the zenith direction (upward). The in-vehicle antenna device 10 is a device that is mounted on the roof of the upper surface of a vehicle (not shown), and consists of an antenna base 20, a case 22, antennas 30-33, and substrates 40-42.

[0012] In Figure 1, the front-to-back direction of the vehicle to which the vehicle-mounted antenna device 10 is attached is defined as the x-direction, the left-to-right direction perpendicular to the x-direction is defined as the y-direction, and the vertical direction perpendicular to both the x-direction and the y-direction is defined as the z-direction. Furthermore, the direction from the driver's seat of the vehicle towards the front is defined as the +x-direction, the direction to the left is defined as the +y-direction, and the direction towards the zenith (upward) is defined as the +z-direction. In addition, the azimuth angle φ = 0° in the +x-direction (forward direction), the azimuth angle φ = 90° in the +y-direction (left direction), and the zenith angle θ = 0° in the +z-direction. In this embodiment, the front-to-back, left-to-right, and up-and-down directions of the vehicle-mounted antenna device 10 will be described as being the same as the front-to-back, left-to-right, and up-and-down directions of the vehicle.

[0013] The antenna base 20 is a plate-shaped member that forms the bottom surface of the vehicle-mounted antenna device 10. The antenna base 20 includes, for example, a resin insulating base and a metal base 21, with the metal base 21 attached to the insulating base by a number of screws (not shown). The metal base 21 is a plate-shaped member that functions as the ground for the vehicle-mounted antenna device 10 when the vehicle-mounted antenna device 10 is mounted on the roof (not shown) of the vehicle. Although the antenna base 20 is shown as having the metal base 21 directly attached to the insulating base, it is not limited to this. For example, the antenna base 20 may consist only of a metal base or a metal plate, or it may have an insulating base or other members such as a metal plate attached. The antenna base 20 may also include an insulating base and a metal plate, or it may include an insulating base, a metal base and a metal plate. Alternatively, instead of using an insulating base, a waterproof pad may be used to surround the metal base.

[0014] The metal base 21 is formed as a single metal base to which the substrates 40-42 are attached, as shown in Figure 1. However, the metal base to which the substrates 40-42 are attached does not have to be a single metal base. For example, the substrates 40-42 may each be attached to separate metal bases, or the metal base to which substrates 40 and 42 are attached may be separate from the metal base to which substrate 41 is attached. In this case, the separate (divided) metal bases may be electrically connected by another metal base or another metal plate, and may also be held by a resin insulating base. Alternatively, a metal plate may be used instead of a metal base, or a combination of a metal base and a metal plate may be used.

[0015] Case 22 is a component (a so-called radome) that covers the antenna base 20 and, together with the antenna base 20, forms a housing space in which the antennas 30-33 are housed. Case 22 is made of a synthetic resin (e.g., ABS resin) that is transparent to electromagnetic waves and has a shark fin shape, which is lower at the front and gets higher towards the rear.

[0016] The case 22 is then attached to the antenna base 20 such that the lower opening of the case 22 is closed by the antenna base 20. The external dimensions of the case 23 in this embodiment are, for example, approximately 190mm to 200mm in the front-to-back direction, approximately 60mm to 65mm in the up-to-down direction, and approximately 70mm to 75mm in the left-to-right direction. An elastic pad may also be provided between the antenna base 20 and the case 22.

[0017] <<Overview of Antennas 30 and 31>> Antennas 30 and 31 are antennas that correspond to radio waves in the V2X frequency band (vertical polarization, which is linear polarization). Specifically, antennas 30 and 31 are used when the vehicle-mounted antenna device 10 transmits radio waves for V2X (for example, in the 5.9 GHz band) and receives radio waves for V2X using a spatial diversity method.

[0018] Antenna 30 is mounted on a circuit board 40 attached to the front portion of the metal base 21. As will be described in detail later, antenna 30 is mainly located in front of the vehicle-mounted antenna device 10 and communicates with other V2X antennas (not shown).

[0019] Meanwhile, antenna 31 is mounted on a circuit board 41 attached to the rear portion of the metal base 21. Antenna 31 is primarily located behind the vehicle-mounted antenna device 10 and communicates with other V2X antennas (not shown).

[0020] <<Details of Antenna 30>> Antenna 30 is a vertically polarized monopole antenna used for V2X communication. Antenna 30 is a metal rod-shaped member that operates as a grounded monopole antenna, and a feed point (not shown) is provided at one end on the substrate 40 side. Therefore, antenna 30 can exchange signals with a signal processing circuit (not shown) via the feed point and the substrate 40.

[0021] In this embodiment, the length of the antenna 30 from one end to the other is one-quarter of the wavelength of the V2X frequency band. Hereafter, assuming that the wavelength of the V2X frequency band is λ (approximately 50 mm), the length of the antenna 30 will be λ / 4 (approximately 12.5 mm). Furthermore, since the antenna 30 is mounted approximately vertically on the front surface of the substrate 40, the height of the antenna 30 from the front surface of the substrate 40 will also be λ / 4 (approximately 12.5 mm).

[0022] In this embodiment, the length (physical length) or distance of the antenna may be expressed in terms of so-called electrical length, using one wavelength λ in the V2X frequency band, for example, λ / 4. In this case, the electrical length includes not only a single value but also values ​​that are shifted by a predetermined value (for example, 1 / 32 of λ). This is because wavelengths are not always expressed as integers that are divisible evenly, and the electrical length changes due to various factors such as the material of the object and the environment. For this reason, in this embodiment, for example, λ / 4 means approximately λ / 4. Hereafter, for example, a predetermined electrical length (for example, λ / 4) may be written as λ / 4 or approximately λ / 4, but even if it is simply written as λ / 4 without "approximately", it will include approximately λ / 4.

[0023] <<Details of Antenna 31>> Antenna 31 is a collinear antenna array for vertical polarization used in V2X communication. Antenna 31 is a metal rod-shaped member attached to the substrate 41, and has a straight section 60, an annular section 61, a straight section 62a, and a bent section 62b.

[0024] The straight section 60 has a length of λ / 2, and a feed point (not shown) is provided at one end on the substrate side 41. A straight section 62a is provided at the other end of the straight section 60 via the annular section 61. Furthermore, the straight section 62a extends from the annular section 61 to prevent the antenna 31 from coming into contact with the case 22. Specifically, the straight section 62a extends from the annular section 61 so as to be inclined by a predetermined angle in the +x direction from the vertical.

[0025] In this embodiment, a bent portion 62b is provided at the tip of the straight portion 62a to reliably prevent contact between the antenna 31 and the case 22. However, if the height of the case 22 is sufficiently high, for example, so that the antenna 31 does not come into contact with the case 22, the straight portion 62a may extend vertically from the annular portion 61, and it is not necessary to provide the bent portion 62b.

[0026] Here, the length of the tip from the end of the straight section 62a on the annular section 61 side to the bent section 62b in this embodiment is λ / 2. Therefore, in the antenna 31, a straight section 60 with a length of λ / 2 and a straight section 62a and a bent section 62b with a length of λ / 2 are provided on both sides of the annular section 61. However, for example, if the phase of vertical polarization in the straight section 60 and the phase of vertical polarization in the straight section 62a and the bent section 62b are inverted, the gain of the antenna 31 will decrease.

[0027] Therefore, in this embodiment, a spirally wound annular section 61 is provided to adjust the phase of vertical polarization in the straight section 60 and the phase of vertical polarization in the straight section 62a and the bent section 62b, so that the gain of the antenna 31 in the desired frequency band is increased. Consequently, an antenna 31 with such a configuration can increase the gain of radio waves in the frequency band used for V2X, for example.

[0028] Here, antenna 30 is assumed to be a rod-shaped monopole antenna and antenna 31 is assumed to be a collinear antenna array, but it is not limited to these. As will be explained in detail later, antennas 30 and 31 can be any antenna (including grounded and ungrounded types) that supports vertical polarization in the desired frequency band, such as a dipole antenna or a patch antenna. Also, while antennas 30 and 31 are assumed to be antennas that support V2X, they can be other communication standards (for example, Wi-Fi® or Bluetooth®).

[0029] <<Antenna 32>> Antenna 32 is, for example, a patch antenna for receiving 1.5 GHz band radio waves for a Global Navigation Satellite System (GNSS). The antenna 32 in this embodiment is mounted on a substrate 42 attached to a metal base 21 and comprises a dielectric member 70 and a radiating element 71.

[0030] The substrate 42 is located on the metal base 21, between the substrate 40 located at the very front and the substrate 41 located at the very rear, on the substrate 40 side. Therefore, the antenna 32 is located between the antenna 30 and the antenna 31, on the antenna 30 side.

[0031] The dielectric member 70 is made of a dielectric material such as ceramic and is a plate-shaped or box-shaped member that is approximately square in plan view in the xy plane as seen from the +z direction. A conductor that functions as a ground conductor film (or ground conductor plate) is formed on the back surface of the dielectric member 70. The back surface of the dielectric member 70 is attached to the substrate 42 by, for example, an adhesive (not shown).

[0032] A conductive radiating element 71, which is approximately square in shape with equal length and width, is formed on the front surface of the dielectric member 70. Here, "approximately square" includes shapes in which at least some corners are cut diagonally to the sides, or shapes in which some of the sides have notches (recesses) or protrusions (convex parts). Note that the shape of the dielectric member 70 is not limited to approximately square, and may be a quadrilateral such as an approximately rectangular, or it may be an approximately circular or approximately elliptical shape.

[0033] The radiating element 71 is provided with two feed points (not shown). Although not shown for convenience, two feed lines are connected to each of the two feed points via two through holes (not shown) that penetrate the substrate 42 and the dielectric member 70. By distributing power through these feed lines with a phase difference, it operates as a circularly polarized antenna. Although the antenna 32 is assumed to be a GNSS antenna, it may also be an antenna that receives radio waves of other standards, such as Satellite Digital Audio Radio Service (SDARS).

[0034] <<Antenna 33>> Antenna 33 is an antenna for receiving radio waves in the DAB (Digital Audio Broadcast) band, for example. Specifically, antenna 33 receives radio waves in Band-III (174MHz~240MHz), for example. Antenna 33 is composed of a holder 80, a helical element (hereinafter simply referred to as "coil") 81, and a capacitively charged element 82. In this embodiment, antenna 33 receives radio waves in Band-III (174MHz~240MHz), but it may also receive other bands in the DAB (Digital Audio Broadcast) band, such as L-Band (1452MHz~1492MHz).

[0035] The holder 80 is a resin component that holds the coil 81 and the capacitive loading element 82, and is attached to the metal base 21. The coil 81 is attached to the cylindrical portion of the holder 80. One end of the coil 81 is electrically connected to a circuit board (not shown) provided on the metal base 21, and the other end of the coil 81 is electrically connected to the capacitive loading element 82.

[0036] The capacitive loading element 82 is an element that resonates with the coil 81 in a desired frequency band, and is a metal body formed by connecting two quadrilateral shapes attached to each of the left and right side surfaces of the upper part of the holder 80 at the lower part. In FIG. 1, for the sake of convenience, only the metal body on the right side of the upper part of the holder 80 is shown, but a metal body similar to the metal body on the right side is also attached to the holder 80 on the left side. Also, the capacitive loading element 82 includes a lower metal body (not shown) that connects the left and right metal bodies.

[0037] Here, the "metal body" is formed by processing a metal member, and includes, for example, a plate-shaped metal member such as a metal plate, as well as a three-dimensional metal member having a shape other than plate-shaped. For example, the metal body on the right side and the metal body on the left side may be connected at the top or integrally formed, and may have a three-dimensional shape such as an inverted V shape, an inverted U shape, a mountain shape, or a shape excluding the base of a trapezoid when viewed from the front or the rear.

[0038] By the way, in the present embodiment, the holder 80 is installed so that the distance between the rear end of the capacitive loading element 82 and, for example, the tip of the bent portion 62b in the antenna 31 is shorter than λ, which is one wavelength in the V2X frequency band. Also, in the present embodiment, the length of the rear side of the capacitive loading element 82 is, for example, λ / 2, but it may be designed to be slightly longer than λ / 2. In such a case, since the capacitive loading element 82 operates as a reflector for the antenna 31, the gain of the antenna 31 can be improved.

[0039] Thus, in the present embodiment, since the antenna 33 is used as a reflector, the antenna 33 is provided on the antenna 31 side between the antenna 30 and the antenna 31.

[0040] <<Relationship between the V2X antenna and the case 22>> As described above, the in-vehicle antenna device 10 is equipped with antennas 30 and 31 for V2X, an antenna 32 for GNSS, and an antenna 33 for DAB. Of these antennas, the V2X antennas 30 and 31 have the highest operating frequency band at 5 GHz and a short wavelength λ of approximately 50 mm. For this reason, case 22 may affect the directivity of antennas 30 and 31.

[0041] Therefore, this section uses a model that simulates an in-vehicle antenna device 10 to examine the effect of the case on the antenna's directivity. First, referring to the model in Figure 2, we examine the relationship between the position of the antenna of the in-vehicle antenna device and the case.

[0042] <<Regarding Case 300 and Antenna 310>> Figure 2A shows an example of case 300 and base plate 320. Figure 2B is a diagram illustrating the position of antenna 310. In Figure 2B, case 300 is shown cut along line AA in Figure 2A to show the antenna 310 inside case 300. Also in Figure 2B, the longitudinal axis (axis on the major axis) passing through the geometric center of the elliptical base of case 300 is shown with a dotted line.

[0043] The case 300 is composed of an elliptical top surface 300a in a plan view of the xy plane from the +z direction, and a cylindrical member 300b extending in the -z direction (downward) from the outer circumference of the top surface 300a. In this embodiment, when the case 300 is installed on a base plate 320 placed on the xy plane, the base plate 320 and the top surface 300a are parallel, and the cylindrical member 300b is formed such that the angle between the base plate and the cylindrical member 300b is 90°. The major axis of the top surface 300a is 220 mm, and the minor axis is 110 mm. The height of the cylindrical member 300b (distance from the base plate 320 to the top surface 300a) is 55 mm.

[0044] Antenna 310 is a monopole antenna capable of handling vertical polarization in the V2X frequency band. Since antenna 310 is grounded to the ground plate 320, the length of antenna 310 is λ / 4 (approximately 12.5 mm). In this embodiment, distance Da is defined as the distance from the inside of the cylindrical member 300b on the +x side to antenna 310, along the longitudinal axis (axis on the major axis) passing through the center (geometric center) of the top surface 300a shown by the dotted line in Figure 2B.

[0045] Figure 3 shows the horizontal directivity of antenna 310 at a distance Da = 20 mm, and Figure 4 shows the horizontal directivity of antenna 310 at a distance Da = 50 mm. Specifically, Figures 3 and 4 are calculation results showing how the horizontal gain (dBi) of antenna 310 changes over all directions with respect to vertical change. In this embodiment, an azimuth angle of 0° corresponds to the +x direction (forward direction), and an azimuth angle of 90° corresponds to the +y direction (left direction).

[0046] As is clear from comparing Figure 3 and Figure 4, as the distance Da increases, the gain at an azimuth angle of 0° decreases, and for example, the gain of antenna 310 becomes very large around azimuth angles of 120° and 240°. Therefore, as will be explained in detail later, as the distance Da increases, the forward directivity of antenna 310 tends to deteriorate.

[0047] Figure 5 shows the relationship between the gain deviation and the distance Da in the range φ = ±45° to 120°. Here, the range ±φ (hereinafter referred to as the "specified angle range") is the range from 0° azimuth counterclockwise (+ direction) to φ° and the range from 0° azimuth clockwise (- direction) to φ°. For example, the range φ = ±120° includes the range from 0° azimuth to 120° (i.e., azimuth angle 120°) and the range from 0° azimuth clockwise (- direction) to 120° (i.e., azimuth angle 240°). The "gain deviation" is the difference between the maximum gain and the minimum gain within the specified angle range.

[0048] As shown in Figure 5, even when the distance Da increases, the gain deviations for φ = ±45°, ±60°, and ±90° generally remain within a range of 5 dBi, with some exceptions. On the other hand, the gain deviation for φ = ±120°, shown by the solid line in Figure 5, increases to approximately 10 dBi when the distance Da is around 50 mm, and then decreases. The gain deviation then gradually increases from around 75 mm when the distance Da is around 82 mm, reaching approximately 31 dBi. Furthermore, beyond 82 mm when the distance Da exceeds 82 mm, it fluctuates significantly in the range of approximately 20 dBi to 40 dBi.

[0049] As mentioned above, in the vehicle-mounted antenna device 10, antennas 30 and 31 receive vertical polarization using a so-called diversity method. In such a case, even the front antenna 30 preferably has good directivity within a certain angular range centered on the front (for example, a range of φ = ±120° with 0° as the reference). Similarly, even the rear antenna 31 preferably has good directivity within a certain angular range centered on the rear (for example, a range of φ = ±120° with 180° as the reference). For this reason, it is preferable that both antennas 30 and 31 have small gain deviations over a wide angular range (for example, a range of φ = ±120°).

[0050] Therefore, when installing the antenna 310 inside the case 300, it is preferable to set the distance Da to be less than or equal to the distance (75 mm) at which the gain deviation at φ = ±120° begins to rise significantly toward 30 dBi, as shown in Figure 5. Furthermore, in order to further reduce the gain deviation at φ = ±120°, it is even more preferable to set the distance Da to be less than or equal to the distance (50 mm) at which the gain deviation peaks at approximately 10 dBi. Note that 75 mm, which is a preferred distance for reducing the gain deviation, corresponds to 3 / 2 of one wavelength λ in the V2X frequency band ((3 × λ) / 2), and 50 mm corresponds to one wavelength λ.

[0051] <<Regarding Case 400 and Antenna 410>> The shape of the +x end of case 300 shown in Figure 2 is similar to, for example, the shape of the rear side (-x side) of the shark fin type case 22 in Figure 1. Therefore, next, we will use a case that is similar in shape to the front side (+x side) of the shark fin type case 22 and perform the same verification as in Figure 2.

[0052] Figure 6A shows an example of case 400 and base plate 420. Figure 6B is a diagram illustrating the position of antenna 410. In Figure 6B, case 400 is shown cut along line AA in Figure 6A to show the antenna 410 inside case 400. Also in Figure 6B, the longitudinal axis (axis on the major axis) passing through the geometric center of the elliptical base of case 400 is shown with a dotted line.

[0053] The case 400 is composed of an elliptical top surface 400a in a plan view of the xy plane as seen from the +z direction, and a cylindrical member 400b extending from the outer circumference of the top surface 400a in the -z direction (downward). In this embodiment, when the case 400 is placed on a base plate 420 on the xy plane, the height of the storage space in the front part of the case 400 gradually increases, and the cylindrical member 400b is formed so that the base plate 420 and the top surface 400a are parallel.

[0054] Specifically, the cylindrical member 400b is formed such that the angle between the straight line extending from the furthest point (the furthest +x direction) of the case 400 on the base plate 420 to the top surface 400a and the base plate 420 is angle α (for example, 40°). Furthermore, the cylindrical member 400b is formed such that the angle between the straight line extending from the furthest point (the furthest -x direction) of the case 400 on the base plate 420 to the top surface 400a and the base plate 420 is 90°.

[0055] In this case 400, the major axis of the top surface 400a is 161 mm, and the minor axis is 20 mm. The height of the cylindrical member 400b (distance from the base plate 420 to the top surface 400a) is 55 mm. Furthermore, the major and minor axes of the elliptical base of case 400 are 220 mm and 45 mm, respectively.

[0056] Antenna 410 is a monopole antenna capable of handling vertical polarization in the V2X frequency band, similar to antenna 310 shown in Figure 2. Therefore, a detailed explanation is omitted here. Here, distance Db is defined as the distance from the inner tip of the cylindrical member 400b on the +x side to antenna 410, along the longitudinal axis passing through the geometric center of the elliptical base of case 400.

[0057] The height of the case 400 gradually increases from the front to the rear until it reaches a predetermined height (55 mm). However, the antenna 410 cannot be installed in the front part of the case 400 where the height of the case 400 is lower than the height of the antenna 410. As described above, in this embodiment, the length of the antenna 410 is λ / 4 (approximately 12.5 mm), and the angle α is 40°. Therefore, within the case 400, the antenna 410 must be positioned at a distance Db of at least approximately 14 mm. Note that a distance of Db = 14 mm is the distance at which the antenna 410 can be positioned while in contact with the case 400. Hereinafter, in this embodiment, the position at a distance of Db = 14 mm will be referred to as the "reference position".

[0058] Figure 7 shows the relationship between distance Db and gain deviation. In all cases of φ = ±45°, ±60°, ±90°, and ±120°, the gain deviation tends to decrease as the distance Db decreases, and especially when the distance Db is 80 mm or more, the gain deviation tends to gradually increase. However, as mentioned above, it is preferable for antenna 410 to have good directivity over a wide angular range (for example, φ = ±120°).

[0059] The gain deviation for φ = ±120°, shown by the solid line in Figure 7, increases as the distance Db increases from 14 mm (reference position), and then decreases to approximately 2.7 dBi around 44 mm (reference position + 30 mm). Furthermore, the gain deviation for φ = ±120° gradually increases from around 44 mm (reference position + 30 mm) of distance Db, reaching a peak value (4.3 dBi) around 64 mm (reference position + 50 mm).

[0060] Subsequently, as the distance Db increases, the gain deviation for φ = ±120° decreases initially, then increases again, reaching a peak value (7.3 dBi) again around 90 mm (reference position + 76 mm). Furthermore, as the distance Db exceeds 90 mm (reference position + 76 mm), the gain deviations for φ = ±45°, ±60°, and ±90° also gradually increase.

[0061] Therefore, in order to place the antenna 410 inside the case 400 while suppressing a large gain deviation, it is preferable to set the distance Db to at least 90 mm (reference position + 76 mm) or less. In practice, setting the distance Db to 64 mm (reference position + 50 mm) or less is even preferable, as it makes it possible to suppress the gain deviation of φ = ±45° to ±120° to a predetermined value (approximately 4 dBi) or less.

[0062] <<Regarding the desired antenna position>> Incidentally, setting the distance Db to 90 mm or less, or 64 mm or less, is equivalent to setting the distance from the reference position where the antenna contacts the case to 76 mm or less, or 50 mm or less. These distances are approximately the same as the preferred distances (75 mm or 50 mm) for distance Da in the case of Figure 2. Therefore, in either the case of Figure 2 or Figure 6, when placing a V2X antenna inside the case, directivity can be improved by installing the contact portion within approximately 75 mm (3 / 2 wavelength: (3 × λ) / 2), more preferably within approximately 50 mm (1 wavelength: λ), from the position where the antenna contacts the case.

[0063] In this embodiment, the "desired position" is defined as a position where a portion of the antenna in contact with the case is moved horizontally by a distance of, for example, less than 3 / 2 wavelength (3λ / 2) of V2X. As will be explained in more detail later, the "part of the antenna in contact with the case" refers to the portion that virtually comes into contact with the case when the antenna is moved horizontally from its actual installation position.

[0064] <<Installation location of antenna 30>> Figure 8 is a diagram illustrating the position of the front antenna 30 in the vehicle-mounted antenna device 10. For ease of understanding, Figure 8 shows a cross-section of the case 22 along a line passing through the center point of the case 22 in the left-right direction and along the x-axis direction.

[0065] In this embodiment, the position of the antenna 30 is determined such that a portion of the antenna 30 is in the desired position described above. Specifically, in this embodiment, the antenna 30 (tip P1) is positioned at a distance D1 backward from the position where the tip P1 of the antenna 30 contacts the case 22. Here, the distance D1 is shorter than approximately 75 mm, which is 3 / 2 wavelength (3λ / 2) of V2X (for example, 5 mm). Ideally, the antenna 30 should be closer to the case 22, but if it were to touch, the vibration of the vehicle would put a load on the antenna 30, so it is kept at a small distance. Note that in Figure 8, the state in which the tip P1 of the antenna 30 is in contact with the case 22 is shown by a dotted line for convenience, but this is a hypothetical state.

[0066] <<Installation location of antenna 31>> Figure 9 is a diagram illustrating the position of the rear antenna 31 in the vehicle-mounted antenna device 10. Note that, as with Figure 8, Figure 9 also shows a cross-section of the case 22.

[0067] In this embodiment, the position of the antenna 31 is determined such that a portion of the antenna 31 is in the desired position described above. Specifically, in this embodiment, for example, the antenna 31 (end P2) is positioned at a distance D2 forward from the position where the end P2 of the straight section 60 on the annular section 61 side contacts the case 22. Here, the distance D2 is shorter than approximately 75 mm, which is 3 / 2 wavelength (3λ / 2) of V2X (for example, 5 mm). Ideally, the antenna 31 should be closer to the case 22, but if it were to come into contact, the vibration of the vehicle would put a load on the antenna 31, so it is kept at a small distance. In Figure 9, the dotted line shows a hypothetical state where the end P2 of the straight section 60 is in contact with the case 22.

[0068] <<Directivity of antennas 30 and 31 in the horizontal plane>> Figure 10 shows the horizontal directivity of antennas 30 and 31 installed in the vehicle-mounted antenna device 10. In Figure 10, the solid line shows the directivity of antenna 30, and the dotted line shows the directivity of antenna 31. As mentioned above, an azimuth angle of 0° corresponds to the +x direction (forward direction), and an azimuth angle of 90° corresponds to the +y direction (left direction).

[0069] Figure 10 shows the simulation results illustrating the horizontal directivity of antennas 30 and 31 when using an infinite ground plane. As shown in Figure 10, in this embodiment, with some exceptions, a gain of slightly less than 10 dBi can be obtained for vertical polarization in the V2X frequency band in the front, rear, left, and right directions of the vehicle-mounted antenna device 10 on an infinite ground plane. Thus, good directivity can be obtained in the horizontal plane when using antennas 30 and 31.

[0070] Incidentally, the vehicle-mounted antenna device 10 shown in Figure 1 is a so-called composite antenna device, and in addition to the antennas 30 and 31 for V2X, it is equipped with an antenna 32 for GNSS and an antenna 33 for DAB. In such a composite antenna device, the individual antennas need to be arranged so that no unnecessary electrical interference occurs between them.

[0071] In this embodiment, as shown in Figure 8, antenna 30 is positioned close to the front portion of case 22 (for example, at a distance D1 = 5 mm). Antenna 31 is positioned close to the rear portion of case 22 (for example, at a distance D2 = 5 mm), as shown in Figure 9. Therefore, in the vehicle-mounted antenna device 10, it is possible to have a long distance between the front antenna 30 and the rear antenna 31. For this reason, in this embodiment, the GNSS antenna 32 and the DAB antenna 33 can be positioned in the long distance between antenna 30 and antenna 31.

[0072] Furthermore, in this embodiment, antennas 30 and 31 perform at least one of receiving and transmitting signals in the same frequency band. Between antennas 30 and 31, antennas with lower frequency bands than those corresponding to antennas 30 and 31 (in this case, antennas 32 and 33) are positioned. Antennas corresponding to higher frequency bands are more susceptible to the influence of case 22, while antennas corresponding to lower frequency bands are less susceptible to the influence of case 22. For this reason, in this embodiment, antennas 30 and 31 are positioned further out in the vehicle-mounted antenna device 10, while antennas 32 and 33 are positioned further inward. By arranging the antennas in this way, the performance of each antenna can be improved.

[0073] Furthermore, the height of antenna 30 is lower than the height of antenna 31. Therefore, by setting the antenna configuration of antennas 30 and 31 according to the front and rear positions in which the antennas are placed in the vehicle-mounted antenna device 10, and the internal space of the case 22, the vehicle-mounted antenna device 10 can be miniaturized while ensuring the directivity and gain of antennas 30 and 31.

[0074] In this embodiment, antennas 30 and 31 corresponding to the same frequency band have different antenna configurations. However, antennas 30 and 31 are not limited to having different configurations; they may have the same configuration depending on the design requirements. Thus, when multiple antennas are arranged in the vehicle-mounted antenna device 10, the combination may include antennas with the same configuration, or it may consist entirely of antennas with different configurations.

[0075] Furthermore, antennas 30 and 31 are positioned approximately in the center of the vehicle-mounted antenna device 10 in the width direction (Y direction). Therefore, the directivity of antennas 30 and 31 can be made symmetrical with respect to the X axis, and adjustments and control to give directivity in the front-to-back direction (X direction) become easier.

[0076] In this embodiment, antenna 32 is positioned such that the height of its upper surface is lower than the upper end of antenna 30. In this case, the electrical characteristics of antenna 30 are improved. However, antenna 32 may also be positioned such that the height of its upper surface is higher than the upper end of antenna 30. In this case, the electrical characteristics of antenna 32 are also improved. In other words, in this embodiment, the heights of the antennas arranged in the vehicle-mounted antenna device 10 can be selected depending on the design application. This ensures that the design of the vehicle-mounted antenna device 10 is not compromised, the characteristics of the antennas arranged in the vehicle-mounted antenna device 10 are ensured, and miniaturization is also possible.

[0077] Furthermore, in this embodiment, antennas 30, 31, and 32 are each mounted on different substrates. However, at least two of the antennas 30, 31, and 32 are... They can be installed on the same circuit board. This improves the ease of assembling the antenna.

[0078] <<Correspondence>> In the vehicle-mounted antenna device 10 shown in Figure 1, antenna 30 corresponds to the "first antenna," and antenna 31 corresponds to the "second antenna." Also, for example, antenna 32 corresponds to the "third antenna."

[0079] Furthermore, for example, the tip P1 of antenna 30 corresponds to "at least a part of the first antenna," and the distance D1 corresponds to "a predetermined distance." The +x direction corresponds to "the first direction," and the -x direction corresponds to "the second direction opposite to the first direction."

[0080] Furthermore, for example, the end P2 of the straight section 60 in antenna 31 corresponds to "at least a part of the second antenna," and the distance D2 corresponds to "a predetermined distance."

[0081] Furthermore, for example, a position at a distance D1 away from the position where the tip P1 of the antenna 30 contacts the case 22 (i.e., the position of the tip P1 of the installed antenna 30) corresponds to the "first position". Similarly, a position at a distance D2 away from the position where the end P2 of the antenna 31 contacts the case 22 (i.e., the position of the end P2 of the installed antenna 31) corresponds to the "second position".

[0082] <<<Vehicle-mounted antenna device 11 (second embodiment)>>> Figure 11 is a diagram illustrating the configuration of the vehicle-mounted antenna device 11 of the second embodiment. In Figure 11, the case 22 is shown removed in the zenith direction (upward). The vehicle-mounted antenna device 11 is composed of an antenna 34 and passive elements 35, 36a to 36c instead of the antenna 30 of the vehicle-mounted antenna device 10 in Figure 1. Therefore, here we will describe the antenna 34 and the passive elements 35, 36a to 36c. Hereafter, the three passive elements 36a to 36c may be collectively referred to as passive element 36.

[0083] Antenna 34, like antenna 30, is a vertically polarized monopole antenna used for V2X communication. Antenna 34 is a metal rod-shaped member that operates as a grounded monopole antenna, and a feed point (not shown) is provided at one end on the substrate 40 side. Therefore, antenna 30 can exchange signals with a signal processing circuit (not shown) via the feed point and the substrate 40.

[0084] In this embodiment, the length of the antenna 34 from one end to the other is half the wavelength of the V2X frequency band. Therefore, the length of the antenna 34 is λ / 2 (approximately 25 mm). Furthermore, since the antenna 34 is mounted approximately vertically on the front surface of the substrate 40, the height of the antenna 34 from the front surface of the substrate 40 is also λ / 2 (approximately 25 mm).

[0085] Furthermore, in this embodiment, the position of the antenna 34 is determined such that a portion of the antenna 34 is at the desired position described above. Specifically, as shown in Figure 12, the antenna 34 (tip P3) is positioned at a distance D3 backward from the position where the tip P3 of the antenna 34 contacts the case 22. Here, the distance D3 is shorter than approximately 75 mm, which is 3 / 2 wavelength (3λ / 2) of V2X (for example, 5 mm). By installing the antenna 34 at such a position, the influence of the case 22 can be suppressed while improving the directivity of the antenna 34.

[0086] The parasitic elements 35 and 36 are elements that increase the gain in the forward direction (+x direction) of the antenna 34 while improving its directivity. Specifically, the parasitic element 35 is a rod-shaped metal body that functions as a so-called director relative to the antenna 34 and is installed in front of the antenna 34. The parasitic element 35 is installed on the substrate 40 in an ungrounded state. The length of the parasitic element 35 is less than or equal to the length of the antenna 34 (λ / 2).

[0087] Each of the parasitic elements 36a to 36c is a rod-shaped metal body that functions as a so-called reflector relative to the antenna 34, and is installed behind the antenna 34. Therefore, the parasitic elements 36a to 36c are installed between the antenna 30 and the antenna 32. Furthermore, the parasitic elements 36a to 36c are installed in an ungrounded state relative to the metal base 21. The length of each of the parasitic elements 36a to 36c is greater than or equal to the length of the antenna 34 (approximately λ / 2).

[0088] In this embodiment, the tips of each of the passive elements 36a to 36c are bent to prevent them from coming into contact with the case 22. Therefore, for example, if the height of the housing space in the case 22 is sufficiently high, the passive elements 36a to 36c may be straight members.

[0089] Furthermore, the manner in which the parasitic elements 36a to 36c are bent may be other than that shown in Figure 11. In the parasitic elements 36a to 36c shown in Figure 11, the tips of parasitic elements 36a and 36c are bent in the -x direction (rearward direction), and the tip of parasitic element 36b is bent in the +x direction (forward direction). In other words, in the vehicle-mounted antenna device 11 shown in Figure 11, there is a mixture of parasitic elements 36 that are bent in different directions. However, for example, all of the parasitic elements 36a to 36c may be bent in the same direction.

[0090] Furthermore, in the vehicle-mounted antenna device 11 shown in Figure 11, each of the passive elements 36a to 36c is bent at only one point, at the tip (upwards). However, for example, each of the passive elements 36a to 36c may be bent downwards, or they may be bent at multiple points. Moreover, the bending angle of each of the passive elements 36a to 36c does not have to be in the 90° direction as shown in Figure 11; for example, it may be an angle away from the case 22. This makes it possible to further prevent the passive elements 36a to 36c from coming into contact with the case 22, and the vehicle-mounted antenna device 11 can be made smaller.

[0091] Furthermore, in this embodiment, the parasitic elements 35 and 36 are preferably installed within a hypothetical circle (hereinafter referred to as "circle C") with radius λ / 2 centered on the position where the antenna 34 is installed, in order to improve the gain in front of the antenna 34. Specifically, the parasitic element 35 is preferably installed in the +x half of the interior of circle C, and the parasitic element 36 is preferably installed in the -x half of the interior of circle C. By installing the parasitic elements 35 and 36 in such ranges, the horizontal directivity of the antenna 30 can be improved.

[0092] In the vehicle-mounted antenna device 11, both parasitic elements 35 and 36 are provided, but it is also acceptable to provide only one of them. Furthermore, although three parasitic elements 36 that act as reflectors are provided, if parasitic elements 36 are provided, it is sufficient to provide at least one.

[0093] Furthermore, when the parasitic element 35 is grounded, the length of the parasitic element 35 is λ / 4 or less, and when the parasitic element 36 is grounded, the length of the parasitic element 36 is λ / 4 or more. In other words, in this embodiment, the lengths of the parasitic elements 35 and 36 should be set so that they function appropriately as directors and reflectors with respect to the antenna 34.

[0094] <<Horizontal plane directivity of antennas 31 and 34>> Figure 13 shows the simulation results of the horizontal plane directivity of antennas 31 and 34 installed on an infinite ground-mounted vehicle antenna device 11. In Figure 13, the solid line shows the directivity of antenna 34, and the dotted line shows the directivity of antenna 31. As mentioned above, an azimuth angle of 0° corresponds to the +x direction (forward direction), and an azimuth angle of 90° corresponds to the +y direction (left direction).

[0095] As shown in Figure 13, by using antennas 31 and 34, a gain of approximately 10 dBi can be obtained for vertical polarization in the V2X frequency band in the front, rear, left, and right directions of the vehicle-mounted antenna device 10 on an infinite ground plane.

[0096] In particular, comparing the directivity of antenna 30 in Figure 10 (solid line) with the directivity of antenna 34 in Figure 13 (solid line), antenna 34 shows improved gain in the forward and left-right directions compared to antenna 30. Therefore, when using antennas 31 and 34, very good directivity can be obtained in the horizontal plane. Note that the directivity of antenna 31 in Figures 10 and 13 is approximately the same.

[0097] Thus, the vehicle-mounted antenna device 11 includes a parasitic element 35 that operates as a director and a parasitic element 36 that operates as a reflector. Therefore, the vehicle-mounted antenna device 11 improves directivity, particularly because the gain in the forward direction (+x direction) of the antenna 34 is increased.

[0098] <<Regarding the directivity of the vehicle-mounted antenna device X used for comparison>> Figure 14 shows the horizontal plane gain of antenna 34 in each of the vehicle-mounted antenna devices 11 and X (described later). Figure 15 shows the horizontal plane gain of antenna 31 in each of the vehicle-mounted antenna devices 11 and X. Here, "vehicle-mounted antenna device X" is a comparison device that lacks the GNSS antenna 32 and DAB antenna 33 from the configuration of vehicle-mounted antenna device 11 in Figure 11. Note that the only difference between vehicle-mounted antenna device 11 and vehicle-mounted antenna device X is the GNSS antenna 32 and DAB antenna 33, so for convenience, vehicle-mounted antenna device X is not specifically shown here.

[0099] As shown in Figure 14, there is no significant difference between the directivity of antenna 34 of vehicle-mounted antenna device 11 (solid line) and the directivity of antenna 34 of vehicle-mounted antenna device X (dotted line). Also, as shown in Figure 15, there is no significant difference between the directivity of antenna 31 of vehicle-mounted antenna device 11 (solid line) and the directivity of antenna 31 of vehicle-mounted antenna device X (dotted line), except for a certain range (azimuth angle range of 30° to 330°). Antenna 31 is primarily an antenna that corresponds to vertical polarization in the -x direction (a range of ±120° centered on an azimuth angle of 180°). Therefore, even if the gain of antenna 31 decreases in the azimuth angle range of 30° to 330°, it does not pose a problem in terms of the characteristics of antenna 31.

[0100] Thus, in the in-vehicle antenna device 11 of this embodiment, by positioning each of the antennas 31 and 34 in close proximity to the case 22, good directivity can be obtained while preventing the antennas 31 and 34 from being affected by other antennas.

[0101] Furthermore, in this embodiment, antennas 34 and 31 perform at least one of receiving and transmitting signals in the same frequency band. Between antennas 34 and 31, antennas with lower frequency bands than those corresponding to antennas 34 and 31 (in this case, antennas 32 and 33) are positioned. Antennas corresponding to higher frequency bands are more susceptible to the influence of case 22, while antennas corresponding to lower frequency bands are less susceptible to the influence of case 22. For this reason, in this embodiment, antennas 34 and 31 are positioned further out in the vehicle-mounted antenna device 11, and antennas 32 and 33 are positioned further inward in the vehicle-mounted antenna device 11. By arranging the antennas in this way, the performance of each antenna can be improved.

[0102] Furthermore, the height of antenna 34 is lower than the height of antenna 31. Therefore, by setting the antenna configuration of antennas 34 and 31 according to the front and rear positions in which the antennas are placed in the vehicle-mounted antenna device 11, and the internal space of the case 22, the vehicle-mounted antenna device 11 can be miniaturized while ensuring the directivity and gain of antennas 34 and 31.

[0103] In this embodiment, antennas 34 and 31 corresponding to the same frequency band have different antenna configurations. However, antennas 34 and 31 are not limited to having different configurations; they may have the same configuration depending on the design requirements. Thus, when multiple antennas are arranged in the vehicle-mounted antenna device 11, the combination may include antennas with the same configuration, or it may consist entirely of antennas with different configurations.

[0104] Furthermore, antennas 34 and 31 are positioned approximately in the center of the vehicle-mounted antenna device 11 in the width direction (Y direction). Therefore, the directivity of antennas 34 and 31 can be made symmetrical with respect to the X axis, making it easy to adjust and control them to have directivity in the front-to-back direction (X direction).

[0105] In this embodiment, antenna 32 is positioned such that the height of its upper surface is lower than the upper end of antenna 34. In this case, the electrical characteristics of antenna 34 are improved. However, antenna 32 may also be positioned such that the height of its upper surface is higher than the upper end of antenna 34. In this case, the electrical characteristics of antenna 32 are improved. In other words, in this embodiment, the heights of the antennas arranged in the vehicle-mounted antenna device 11 can be selected depending on the design application. This ensures that the design of the vehicle-mounted antenna device 11 is not compromised, the characteristics of the antennas arranged in the vehicle-mounted antenna device 11 are ensured, and miniaturization is also possible.

[0106] Furthermore, in this embodiment, antennas 34, 31, and 32 are each mounted on different substrates. However, at least two of the antennas 34, 31, and 32 are... They can be installed on the same circuit board. This improves the ease of assembling the antenna.

[0107] <<Correspondence>> In the vehicle-mounted antenna device 11 shown in Figure 11, antenna 34 corresponds to the "first antenna". Furthermore, for example, the corner P3 of antenna 34 corresponds to "at least a part of the first antenna", and the distance D3 corresponds to the "predetermined distance".

[0108] Furthermore, for example, the position at a distance D3 away from the point where the corner P3 of the antenna 34 contacts the case 22 (i.e., the position of the corner P3 of the installed antenna 34) corresponds to the "first position".

[0109] <<<Vehicle-mounted antenna device 12 (third embodiment)>>> Figure 16 is a diagram illustrating the configuration of the vehicle-mounted antenna device 12 according to the third embodiment. In the vehicle-mounted antenna device 12, an antenna 37 is provided instead of the antenna 30 in the vehicle-mounted antenna device 10 of Figure 1. Since the configuration of the vehicle-mounted antenna device 12 is the same as that of the vehicle-mounted antenna device 10 except for the antenna 37, the antenna 37 will be described here.

[0110] <<Antenna 37>> Antenna 37 is a patch antenna corresponding to vertical polarization in the V2X frequency band, and comprises a patch element 37a and a ground conductor plate 37b. The patch element 37a is a member formed by bending a metal plate so that it is convex in the +x direction. Specifically, the patch element 37a has a top portion 38 on the +x side having a predetermined width (length in the y-axis direction), and two inclined portions 39 bent in the -x direction from each of the left and right sides of the top portion 38.

[0111] The distance L from each of the left and right sides of the top portion 38 to the end of the inclined portion 39 which is parallel to the left and right sides of the top portion 38 is, for example, 12 mm. This distance L is approximately one-quarter of the wavelength λ of the V2X frequency band (λ / 4 = 12.5 mm). The patch element 37a is also provided with a feed point, which is not shown.

[0112] The ground conductor plate 37b, like the patch element 37a, is a metal plate bent so as to be convex in the +x direction. Furthermore, the ground conductor plate 37b in this embodiment is electrically connected to the metal base 21 so as to function as a ground.

[0113] Furthermore, in this embodiment, a dielectric material (not shown), for example made of synthetic resin, is sandwiched between the patch element 37a and the ground conductor plate 37b to fill the gap between them. The dielectric material is also bonded to both the patch element 37a and the ground conductor plate 37b with insulating tape (not shown). As a result, the patch element 37a is fixed to the ground conductor plate 37b via the dielectric material. Even when using such an antenna 37, it is possible to receive vertically polarized waves in the V2X frequency band.

[0114] <<Installation location of Antenna 37>> Figure 17 is a diagram illustrating the position of the front antenna 37 in the vehicle-mounted antenna device 12. Note that, as with Figure 8 mentioned above, Figure 17 also depicts a cross-section of the case 22.

[0115] In this embodiment, the position of the antenna 37 is determined such that a portion of the antenna 37 is in the desired position described above. Specifically, in this embodiment, for example, the antenna 37 (corner P4) is positioned at a distance D4 backward from the position where the upper corner P4 of the ground conductor plate 37b of the antenna 37 contacts the case 22. Here, the distance D4 is shorter than approximately 75 mm, which is 3 / 2 wavelength (3λ / 2) of V2X (for example, 5 mm). In Figure 17, the dotted line shows a hypothetical state where the corner P3 of the ground conductor plate 37b of the antenna 37 is in contact with the case 22.

[0116] By installing the antenna 37 in this position, the vehicle-mounted antenna device 12 can achieve good directivity (especially forward directivity) in the V2X frequency band.

[0117] <<Correspondence>> In the vehicle-mounted antenna device 12 shown in Figure 16, antenna 37 corresponds to the "first antenna." Furthermore, for example, the corner P4 of antenna 37 corresponds to "at least a part of the first antenna," and the distance D4 corresponds to the "predetermined distance."

[0118] Furthermore, for example, the position at a distance D4 away from the point where the corner P4 of the antenna 37 contacts the case 22 (i.e., the position of the corner P4 of the installed antenna 37) corresponds to the "first position".

[0119] <<<Vehicle-mounted antenna device 13 (fourth embodiment)>>> Figure 18 is a diagram illustrating the configuration of the vehicle-mounted antenna device 13 according to the fourth embodiment. The vehicle-mounted antenna device 13 is housed, for example, in a cavity between the roof panel of a vehicle (not shown) and the roof lining of the ceiling surface inside the vehicle. The vehicle-mounted antenna device 13 is a composite antenna device including multiple antennas that operate in different frequency bands, and comprises a metal base 500, a case 501, and antennas 510 to 514.

[0120] As will be explained in more detail later, antenna 512 is a collective term for antennas 512a to 512d, and antenna 513 is a collective term for antennas 513a and 513b. Also, antenna 514 is a collective term for antennas 514a and 514b.

[0121] The metal base 500 is a roughly quadrilateral metal plate used as a common ground for antennas 510-514 and is installed on the roof lining of the vehicle. The metal base 500 is also a thin plate that extends in all directions (front, back, left, and right).

[0122] Case 501 is a box-shaped component with an opening on its lower side. Since Case 501 is made of insulating resin, radio waves can pass through it. Case 501 is attached to a metal base 500 such that the lower opening of Case 501 is closed by the metal base 500. Therefore, antennas 510-514 are housed in the internal space (housing space) of Case 501.

[0123] Antenna 510 is, for example, a patch antenna compatible with the SDARS system and receives left-hand circularly polarized waves in the 2.3 GHz band. Antenna 510 is installed near the center of the metal base 500.

[0124] Antenna 511 is, for example, a planar antenna compatible with GNSS, and receives radio waves in the 1.5 GHz band from artificial satellites. Antenna 511 is installed behind (-x direction) antenna 510.

[0125] Antenna 512 is an antenna that corresponds to vertical polarization in the V2X frequency band and is similar to antenna 30 of the vehicle-mounted antenna device 10 in Figure 1. Antennas 512a to 512d are each arranged around antenna 510. Specifically, antennas 512a and 512b are arranged in front of and behind antenna 510, respectively. Antennas 512c and 512d are arranged to the left and right of antenna 510, respectively.

[0126] In this embodiment, antenna 512a primarily corresponds to vertical polarization from the front (+x direction), antenna 512b primarily corresponds to vertical polarization from the rear (-x direction), antenna 512c primarily corresponds to vertical polarization from the left (+y direction), and antenna 512d primarily corresponds to vertical polarization from the right (-y direction). Since the vehicle-mounted antenna device 13 is equipped with multiple antennas 512a to 512d with different directivity, it can receive desired radio waves using a diversity method. Details of the installation positions of antennas 510a to 510d will be described later.

[0127] Antennas 513a and 513b are, for example, antennas for telematics compatible with fifth-generation mobile communication systems. Antennas 513a and 513b transmit and receive Sub-6 band radio waves as defined by the fifth-generation mobile communication system standards.

[0128] Antennas 514a and 514b are, for example, telematics antennas compatible with LTE (Long Term Evolution) and 5th generation mobile communication systems. Antenna 514 transmits and receives radio waves in the 700 MHz frequency band to the 2.7 GHz band as defined by the LTE standard. Furthermore, antenna 514 also transmits and receives radio waves in the Sub-6 band, i.e., the frequency band from 3.6 GHz to less than 6 GHz, as defined by the 5th generation mobile communication system standard.

[0129] The applicable communication standards and frequency bands for antennas 510-514 are not limited to those described above, but may include other communication standards and frequency bands.

[0130] <<Installation location of antenna 512>> Figure 19 is a diagram illustrating the installation position of antenna 512a. Specifically, Figure 19 is an enlarged view of the area around the installation position of antenna 512a in the cross-section of the vehicle-mounted antenna device 13 of line AA in Figure 18.

[0131] In this embodiment, the position of the antenna 512a is determined such that a portion of the antenna 512a is in the desired position described above. Specifically, in this embodiment, for example, the antenna 512a (tip P5) is positioned at a distance D5 backward from the position where the tip P5 of the rod-shaped antenna 512a contacts the case 501. Here, the distance D5 is shorter than approximately 75 mm, which is 3 / 2 wavelength (3λ / 2) of V2X (for example, 5 mm). In Figure 19, the dotted line also shows a hypothetical state where the tip P5 of the antenna 512a is in contact with the case 501.

[0132] By installing antenna 512a in this position, the forward directivity in the V2X frequency band can be improved. Although antenna 512a has been described here, the other antennas 512b to 512d for V2X are also installed in the same desired positions as antenna 512a. Therefore, the vehicle-mounted antenna device 13 can improve directivity in four directions: front, back, left, and right, in the V2X frequency band.

[0133] In Figure 18, the vehicle-mounted antenna device 13 is shown to have four V2X antennas 512a to 512d, but it is not limited to this. For example, only two antennas, 512a and 512b, for the front-to-back direction may be provided as V2X antennas, or only two antennas, 512c and 512d, for the left-to-right direction may be provided. Even in such cases, the directivity of the provided antennas can be improved.

[0134] <<Correspondence>> In the vehicle-mounted antenna device 13 shown in Figure 18, for example, antenna 512a corresponds to the "first antenna," and antenna 512b corresponds to the "second antenna." Also, for example, antenna 510 corresponds to the "third antenna."

[0135] Furthermore, for example, the tip P4 of antenna 512a corresponds to "at least a part of the first antenna," and the distance D4 corresponds to "a predetermined distance." The +x direction corresponds to "the first direction," and the -x direction corresponds to "the second direction opposite to the first direction."

[0136] Furthermore, for example, the position at a distance D4 away from the point where the tip P4 of antenna 512a contacts case 501 (i.e., the position of the tip P4 of the installed antenna 512a) corresponds to the "first position". In this case, the position corresponding to the tip of antenna 512b corresponds to the "second position".

[0137] <<<Vehicle-mounted antenna device 14 (5th embodiment)>>> Figure 20 shows the configuration of an in-vehicle antenna device 14, which is a fifth embodiment of the present invention. Compared to the in-vehicle antenna device 10 (Figure 1), which is the first embodiment described above, the in-vehicle antenna device 14 is equipped only with antenna 30 with respect to the antenna corresponding to the V2X frequency band. In other words, the in-vehicle antenna device 14 is not equipped with antenna 31 and circuit board 41 compared to the in-vehicle antenna device 10, which is the first embodiment. Note that the in-vehicle antenna device 14 has the same configuration as the in-vehicle antenna device 10 except for the absence of antenna 31 and circuit board 41. Also, in the in-vehicle antenna device 14 shown in Figure 20, components that are the same as those in the in-vehicle antenna device 10 are denoted by the same reference numerals as those in the in-vehicle antenna device 10. Also, Figure 20 is a perspective view of the in-vehicle antenna device 14 with the case 22 removed in the zenith direction (upward direction), similar to Figure 1.

[0138] Incidentally, in the vehicle-mounted antenna device 14, it is preferable that the antenna 30 has good directivity within a certain angular range centered on the front (for example, a range of φ = ±120° with 0° as the reference). That is, it is preferable that the antenna 30 has a small gain deviation over a wide angular range (for example, a range of φ = ±120°). In this case as well, as in the case shown in Figure 8 above, the gain deviation over a wide angular range can be reduced and the directivity can be improved by setting the position of the antenna 30 to a desired position.

[0139] Figure 21 shows the horizontal directivity of the antenna 30 installed on the vehicle-mounted antenna device 14. As mentioned above, an azimuth angle of 0° corresponds to the +x direction (forward direction), and an azimuth angle of 90° corresponds to the +y direction (left direction). Figure 21 shows the simulation results of the horizontal directivity of the antenna 30 when using an infinite ground plane. As shown in Figure 21, in this embodiment, with some exceptions, a gain of slightly less than 10 dBi can be obtained for vertical polarization in the V2X frequency band in the front, back, left, and right directions of the vehicle-mounted antenna device 10 on an infinite ground plane. Thus, good directivity can be obtained in the horizontal plane when using the antenna 30.

[0140] In the fifth embodiment of the vehicle-mounted antenna device 14 described above, only the front antenna 30 was provided with respect to the radio waves in the V2X frequency band. However, although not shown in the illustrations and verification, the vehicle-mounted antenna device may also be provided with only the rear antenna 31 with respect to the radio waves in the V2X frequency band. Even in this case, by setting the position of the antenna 31 to a desired position, the gain deviation over a wide range of angles can be reduced, and the directivity can be improved.

[0141] <<>> The following describes other features of the vehicle-mounted antenna device of the embodiment described above, as well as vehicle-mounted antenna devices of embodiments other than the embodiment described above.

[0142] <<Around the circuit board 41 of the vehicle-mounted antenna device 10 (first embodiment)>> Figure 22 is a perspective view showing the area around the circuit board 41 of the vehicle-mounted antenna device 10. Figure 22A shows a perspective view with the circuit board 41 and other components mounted on the metal base 21, and Figure 22B shows an exploded perspective view with the circuit board 41 and other components removed from the metal base 21. Figure 23 is a plan view showing the area around the circuit board 41 of the vehicle-mounted antenna device 10.

[0143] The antenna 31 of the above-described in-vehicle antenna device 10 is mounted on a circuit board 41 attached to the rear portion of the metal base 21. Here, the antenna 31 is electrically connected to the circuit board 41 at a power supply section (not shown). The antenna 31 is then connected to the coaxial cable 44 shown in Figure 22B via a matching circuit (not shown) mounted on the circuit board 41. Note that circuit elements and electronic components other than the matching circuit may be mounted on the circuit board 41.

[0144] Here, the outer perimeter of the matching circuit side (lower side) of the circuit board 41 is electrically connected to the ground on the antenna 31 side through through-holes, via holes, etc. In addition, the outer perimeter of the matching circuit side of the circuit board 41 is treated with a conductive surface treatment such as solder rivet or gold plating.

[0145] Furthermore, the metal base 21 has a receiving portion 49 and a cable housing portion 51 formed therein, as shown in Figures 22A to 23.

[0146] The receiving portion 49 is a receiving structure (recess) for the substrate 41, formed to contact the outer circumference of the matching circuit side (lower side) of the substrate 41, as shown in Figure 22B. As shown in Figures 22A and 22B, the substrate 41 is held under pressure by being assembled to the metal base 21 using screws 43. In addition, the receiving portion 49 of the metal base 21 and the outer circumference of the matching circuit side of the substrate 41 are in contact. This allows the entire outer circumference of the matching circuit side of the substrate 41 to be electrically connected to the ground on the antenna 31 side and the metal base 21.

[0147] Furthermore, the receiving portion 49 is formed so that when the substrate 41 is assembled to the metal base 21, the height of the substrate 41 and the height of the metal base 21 are the same. This suppresses the generation of radiation sources at the edges of the substrate 41 and reduces the influence of the shape of the substrate 41 on the electrical characteristics of the antenna 31.

[0148] Furthermore, by applying a conductive surface treatment to the contact portion between the substrate 41 and the substrate 41 side of the screw 43, electrical conductivity can be established between the contact portion and the metal base 21. In this case, it is preferable that the distance between the screws 43 is less than or equal to half the wavelength of the operating frequency of the antenna 31.

[0149] Furthermore, as shown in Figures 22B and 23, the cable housing section 51 is a recess in which the coaxial cable 44 connected to the substrate 41 is housed. The coaxial cable 44 is held by the metal base 21 by being housed in the cable housing section 51. This improves the retention of the coaxial cable 44. The coaxial cable 44 is also located below the substrate 41. Alternatively, by embedding a portion of the coaxial cable 44 (for example, two-thirds of the diameter of the coaxial cable 44) in the cable housing section 51 or the conductive wall of the metal base 21, the coaxial cable 44 may be located below the upper surface of the metal base 21 or the substrate 41. This suppresses the reduction in the gain of the antenna 31 and the impact on its directivity due to leakage current from the coaxial cable 44.

[0150] <<Antenna 31 and case 22 of the vehicle-mounted antenna device 10 (first embodiment)>> Figure 24 illustrates other examples of antenna 31 and case 22. Figures 24A to 24C show examples of combining antennas 31 of the first to third antenna shapes with case 22 of the first case shape. Figures 24D to 24F show examples of combining antennas 31 of the first to third antenna shapes with case 22 of the second case shape. Figures 24G to 24I show examples of combining antennas 31 of the first to third antenna shapes with case 22 of the third case shape.

[0151] Regarding the above-described in-vehicle antenna device 10, the shapes of the antenna 31 and the case 22 are not limited to those shown in Figure 9. The antenna 31 shown in Figure 9 has a shape having a straight section 62a that slopes towards the +x direction as it goes upward (+z direction) from the annular section 61 (hereinafter referred to as the "first antenna shape"). However, the antenna 31 may also have a straight shape along the z direction (hereinafter referred to as the "second antenna shape").

[0152] Furthermore, the antenna 31 may have a shape (hereinafter referred to as the "third antenna shape") that includes a straight section 60 that slopes toward the +x direction as it goes downward (-z direction) and a straight section 62a that slopes toward the +x direction as it goes upward (+z direction), with the annular section 61 as the boundary. In other words, the straight section 62a connected to one end of the annular section 61 slopes toward the +x direction as it goes upward (+z direction) from the connection point with the annular section 61. Also, the straight section 60 connected to the other end of the annular section 61 slopes toward the +x direction as it goes downward (-z direction) from the connection point with the annular section 61. Note that in the third antenna shape, one end and the other end of the annular section 61 are closest to the case 22.

[0153] Furthermore, Case 22 shown in Figure 9 has a shape with an inner wall aligned along the z direction (hereinafter referred to as the "first case shape"). However, Case 22 may also have a shape with an inner wall that slopes towards the -x direction as it goes upwards (+z direction), as shown in Figures 24D to 24F (hereinafter referred to as the "second case shape"). Also, Case 22 shown in Figure 9 had a shape in which the wall on the antenna base 20 side had a bulge that was convex inwards (towards the antenna 31 side). However, the shape of the wall of Case 22 may be more linear than the first case shape, as shown in Figures 24G to 24I.

[0154] Figures 24A to 24I show examples of combinations of the antenna 31 with the first to third antenna shapes described above and the case 22 with the first to third case shapes. Note that the antenna 31 is not limited to the cases shown in Figures 24A to 24I, and may have a shape that, for example, has a straight section 62a that slopes toward the -x direction as it goes upward (+z direction) from the annular section 61. Alternatively, the antenna 31 may have a shape that has a straight section 62a that slopes toward the -x direction as it goes upward (+z direction) and a straight section 60 that slopes toward the -x direction as it goes downward (-z direction), with the annular section 61 as the boundary.

[0155] <<Antenna 34 of the vehicle-mounted antenna device 11 (second embodiment)>> Figure 25 is a diagram illustrating other examples of antenna 34. Figure 25A shows an example of antenna 34 with a first antenna shape, Figure 25B shows an example of antenna 34 with a second antenna shape, and Figure 25C shows an example of antenna 34 with a third antenna shape.

[0156] The antenna 34 shown in Figures 11 and 12 was mounted on the front surface of the substrate 40 so as to be approximately vertical. However, the shape of the antenna 34 may be other than that shown in Figures 11 and 12.

[0157] The antenna 34 may be bent at the tip to conform to the case 22, as shown in Figures 25A and 25B. In the first antenna shape shown in Figure 25A, the tip of the antenna 34 is bent towards the +x direction, while in the second antenna shape shown in Figure 25B, the tip of the antenna 34 is bent towards the -x direction.

[0158] Furthermore, the angle at which the antenna 34 is bent does not have to be an angle that follows the case 22 as shown in Figures 25A and 25B, and may be 90°, as in the third antenna shape of the antenna 34 shown in Figure 25C. Note that the angle at which the antenna 34 is bent does not have to be acute, right, or obtuse, as long as the antenna 34 does not come into contact with the case 22 or other antennas.

[0159] <<Periphery of the circuit board 40 of the vehicle-mounted antenna device 11 (second embodiment)>> Figure 26 is a perspective view showing the area around the circuit board 40 of the vehicle-mounted antenna device 11. Figure 26A is a perspective view showing the circuit board 40 and other components mounted on the metal base 21, and Figure 26B is an exploded perspective view showing the circuit board 40 and other components removed from the metal base 21. Figure 27 is a plan view showing the area around the circuit board 40 of the vehicle-mounted antenna device 11.

[0160] The antenna 34 of the above-described in-vehicle antenna device 11 is mounted on a circuit board 40 attached to the front portion of the metal base 21. Here, the antenna 34 is electrically connected to the circuit board 40 at a power supply section (not shown). The antenna 34 is then connected to the coaxial cable 46 shown in Figure 26B via a matching circuit (not shown) mounted on the circuit board 40. Note that circuit elements and electronic components other than the matching circuit may be mounted on the circuit board 40.

[0161] Here, the outer circumference of the matching circuit side (lower side) of the circuit board 40 is electrically connected to the ground on the antenna 34 side via through-holes, via holes, etc. In addition, the outer circumference of the matching circuit side of the circuit board 40 is treated with a conductive surface treatment such as solder rivet or gold plating.

[0162] Furthermore, the metal base 21 has a receiving portion 50 and a cable housing portion 52 formed therein, as shown in Figures 26B and 27.

[0163] The receiving portion 50 is a receiving structure (recess) for the substrate 40, formed to contact the outer circumference of the matching circuit side (lower side) of the substrate 40, as shown in Figure 26B. As shown in Figures 26A and 26B, the substrate 40 is held under pressure by being assembled to the metal base 21 using screws 45. In addition, the receiving portion 50 of the metal base 21 and the outer circumference of the matching circuit side of the substrate 40 are in contact. This allows the entire outer circumference of the matching circuit side of the substrate 40 to be electrically connected to the ground on the antenna 34 side and the metal base 21.

[0164] Furthermore, the receiving portion 50 is formed so that when the substrate 40 is assembled to the metal base 21, the height of the substrate 40 and the height of the metal base 21 are the same. This suppresses the generation of radiation sources at the edges of the substrate 40 and reduces the influence of the shape of the substrate 40 on the electrical characteristics of the antenna 34.

[0165] Furthermore, by applying a conductive surface treatment to the contact portion between the substrate 40 and the substrate 40 side of the screw 45, electrical conductivity can be established between the contact portion and the metal base 21. In this case, it is preferable that the distance between the screws 45 is less than or equal to half the wavelength of the operating frequency of the antenna 34.

[0166] Furthermore, the cable housing section 52 is a recess in which the coaxial cable 46 connected to the substrate 40 is housed, as shown in Figures 26B and 27. The coaxial cable 46 is held by the metal base 21 by being housed in the cable housing section 52. This improves the retention of the coaxial cable 46. The coaxial cable 46 is also located below the substrate 40. Alternatively, by embedding a portion of the coaxial cable 46 (for example, two-thirds of the diameter of the coaxial cable 46) in the cable housing section 52 or the conductive wall of the metal base 21, the coaxial cable 46 may be located below the upper surface of the metal base 21 or the substrate 40. This suppresses the reduction in the gain of the antenna 34 and the impact on its directivity due to leakage current from the coaxial cable 46.

[0167] <<Holder 47 for unpowered elements 35, 36>> In the above-described in-vehicle antenna device 11, the parasitic elements 35 and 36 may be held by a holder 47, as shown in Figures 26A and 26B. The holder 47 that holds the parasitic elements 35 and 36 is, for example, made of resin and assembled to the metal base 21 by screws 48. This allows the parasitic elements 35 and 36 to be placed in a hollow space. In this embodiment of the in-vehicle antenna device 11, the integrally formed holder 47 holds both the parasitic elements 35 and 36. This improves the ease of assembly of the in-vehicle antenna device 11. However, the holder that holds the parasitic element 35 and the holder that holds the parasitic element 36 may be formed separately.

[0168] Furthermore, as shown in Figures 26A and 26B, the holder 47 does not cover all of the parasitic elements 35 and 36, but holds them in a manner that covers at least a portion of them. This reduces the contact area between the conductive parts of the parasitic elements 35 and 36 and the resin of the holder 47, thereby suppressing a decrease in the gain of the antenna 34 and changes in its directivity. In addition, by not covering all of the parasitic elements 35 and 36, the amount of resin material used in the holder 47 can be reduced, thereby lowering costs.

[0169] Although not shown, the passive elements 35 and 36 are held in the holder 47 so that their lower ends abut against the holder 47. This allows the passive elements 35 and 36 to be positioned in a hollow space. In other words, contact between the passive elements 35 and 36 and the metal base 21 or the substrate 40 can be avoided. Furthermore, the passive elements 35 and 36 can be inserted into the holder 47 from above, which improves the ease of assembly of the vehicle-mounted antenna device 11.

[0170] At least a portion of the holder 47 is positioned between the antenna 34 and the case 22. The dielectric constants of the holder 47 and the case 22 may be the same or different. For example, if the holder 47 is made of a material with a lower dielectric constant than the case 22, it is possible to suppress the decrease in the gain of the antenna 34 and the impact on its directivity.

[0171] <<Vehicle-mounted antenna device 15 (6th embodiment)>> Figure 28 is a perspective view of the vehicle-mounted antenna device 15. Figure 28A is a perspective view showing the external appearance of the vehicle-mounted antenna device 15 with the case 22 attached, and Figure 28B is a cross-sectional perspective view showing the inside of the vehicle-mounted antenna device 15 with part of the case 22 removed.

[0172] The vehicle-mounted antenna device 14 shown in Figure 20 above had only an antenna 30 located in front of the vehicle-mounted antenna device 14, with respect to the radio waves in the V2X frequency band. However, the vehicle-mounted antenna device 15 shown in Figures 28A and 28B may have only an antenna 31 located behind the vehicle-mounted antenna device 15, with respect to the radio waves in the V2X frequency band. Below, we will describe the features of the vehicle-mounted antenna device 15 that differ from those of the vehicle-mounted antenna device 14.

[0173] The in-vehicle antenna device 14 shown in Figure 20 above had, in addition to antenna 30, an antenna 32 corresponding to GNSS band radio waves and an antenna 33 corresponding to DAB band radio waves. However, in the in-vehicle antenna device 15, as shown in Figure 28B, in addition to antenna 31, two antennas 32 are arranged vertically. For example, a configuration in which two antennas 32 are arranged vertically is sometimes called a multi-stage patch antenna, multilayer patch antenna, or stacked patch antenna. In this case, the frequency band that the first patch antenna corresponds to and the frequency band that the second patch antenna corresponds to can be different. Furthermore, by providing slots or the like in the patch antenna, one patch antenna can correspond to multiple frequency bands. Therefore, by using a multi-stage patch antenna that corresponds to multiple frequency bands, it is possible to correspond to multiple frequency bands. In the in-vehicle antenna device 14 shown in Figure 20, antenna 32 can also correspond to radio waves in frequency bands other than the 1.5GHz band within the GNSS band.

[0174] Furthermore, unlike the vehicle-mounted antenna device 14, the vehicle-mounted antenna device 15 may have a parasitic element in the antenna 32. In the antenna 32 of this embodiment, as shown in Figure 28B, two parasitic elements 72 are arranged above the radiating element 71 of the upper antenna 32. The parasitic elements 72 may be held by a holding member (not shown) surrounding the radiating element 71. By having the parasitic elements 72, the antenna 32 can improve the axial ratio, especially at low elevation angles.

[0175] Furthermore, in the in-vehicle antenna device 15, the case 22 can be designed to be close to the antenna 31, as shown in Figures 28A and 28B. In other words, in the in-vehicle antenna device 15, the case 22 can be designed to conform to the shape of the antenna 31. This further reduces the influence of the case 22 on the antenna 31.

[0176] Furthermore, as shown in Figure 29, which will be described later, antenna 31 has a circuit 63 that suppresses signals in the frequency band corresponding to antenna 32. In this embodiment, circuit 63 is a filter that suppresses signals in the GNSS band corresponding to antenna 32. In other words, circuit 63 suppresses signals in unwanted frequency bands within the radio wave frequency band corresponding to antenna 31.

[0177] This reduces the impact on the performance of the axial ratio of the antenna 32 that corresponds to GNSS band radio waves, and makes it possible to place the antenna 31 in close proximity to the antenna 32. However, the circuit 63 is not limited to a filter, and may be a substrate pattern or the like that has frequency characteristics that suppress GNSS band signals. The circuit 63 may be a lumped-parameter circuit, a distributed-parameter circuit, or a hybrid circuit of lumped-parameter and distributed-parameter circuits. Also, the antenna 31 does not have to have the circuit 63.

[0178] The effects of the circuit 63 of antenna 31 will be described in detail below, using the calculation results of the maximum axial ratio of antenna 32.

[0179] Figure 29 is an explanatory diagram of the distance Dgv between antenna 31 and antenna 32.

[0180] The separation distance Dgv is the horizontal separation distance between antenna 31 and antenna 32 in a side view of the model as shown in Figure 29. Here, we calculate the maximum axial ratio of antenna 32 when the separation distance Dgv is varied for both a model in which antenna 31 does not have circuit 63 and a model in which antenna 31 has circuit 63.

[0181] Figure 30 is a graph showing an example of the maximum axis ratio at an elevation angle of 90° when the separation distance Dgv is varied. Figure 30A is a graph when antenna 31 does not have circuit 63, and Figure 30B is a graph when antenna 31 has circuit 63.

[0182] Figure 31 is a graph showing an example of the maximum axis ratio at an elevation angle of 10° when the separation distance Dgv is varied. Figure 31A is a graph when the antenna 31 does not have circuit 63, and Figure 31B is a graph when the antenna 31 has circuit 63.

[0183] In Figures 30 and 31, the calculation results of the maximum axial ratio of antenna 32 are shown using ▲ and ■ marks on the line when the separation distance Dgv between antennas 31 and 32 is varied to 10 mm, 30 mm, 50 mm, 70 mm, and 90 mm. These ▲ and ■ marks on the line indicate the position of the value on the vertical axis relative to the value on the horizontal axis, and are shown as ▲ and ■ marks for convenience to distinguish them. In addition, Figures 30 and 31 also show the calculation results for a model with only antenna 32 (a model without antenna 31) as reference values.

[0184] As shown in Figures 30A and 31A, if antenna 31 does not have circuit 63, the axial ratio of antenna 32 deteriorates as the separation distance Dgv decreases. In contrast, as shown in Figures 30B and 31B, by having circuit 63 in antenna 31, the axial ratio of antenna 32 is improved even when the separation distance Dgv is small. In other words, by having circuit 63 in antenna 31, the impact on the performance of antenna 32's axial ratio is mitigated, and antenna 31 can be positioned closer to antenna 32. <<Correspondence>> In the vehicle-mounted antenna device 15 shown in Figure 28, antenna 31 corresponds to the "first antenna," and antenna 32 corresponds to the "second antenna."

[0185] <<Vehicle-mounted antenna device 16 (7th embodiment), and vehicle-mounted antenna device 17 (8th embodiment)>> Figure 32 is a perspective view of the vehicle-mounted antenna devices 16 and 17. Figure 32A is a perspective view of the vehicle-mounted antenna device 16, and Figure 32B is a perspective view of the vehicle-mounted antenna device 17.

[0186] The vehicle-mounted antenna device 11 shown in Figure 11 above was equipped with an antenna 33 that corresponds to DAB wave band radio waves. However, the vehicle-mounted antenna device 16 shown in Figure 32A may be equipped with an antenna 90 that corresponds to AM / FM radio radio waves instead of antenna 33. Below, we will describe the features of the vehicle-mounted antenna device 16 that differ from those of the vehicle-mounted antenna device 11.

[0187] The antenna 90 has a helical element 91 and a capacitively charged element 92.

[0188] The helical element 91, together with the capacitively charged element 92, is an element that resonates in the frequency band for AM / FM radio. The capacitively charged element 92, together with the helical element 91, is an element that resonates in the frequency band for AM / FM radio. A slit 93 is formed in the capacitively charged element 92.

[0189] Furthermore, the vehicle-mounted antenna device 17 shown in Figure 32B, like the vehicle-mounted antenna device 16, is equipped with an antenna 94 that corresponds to AM / FM radio waves instead of an antenna 33 that corresponds to DAB wave band radio waves. The antenna 94 has a helical element 91 similar to that of the antenna 90 and a capacitive loading element 92 composed of multiple metal bodies 95.

[0190] The multiple metal bodies 95 are electrically connected at their bottoms on the left and right sides, and connected in the front-to-back direction by a structure such as a filter that electrically blocks the operating frequency band of the antenna 32. Each component of the metal body 95 is flat or curved, but may be changed to an appropriate shape, and may also include meander shapes. Furthermore, each component may be connected at the top, bottom, or between them.

[0191] In addition, in the vehicle-mounted antenna devices 16 and 17, a parasitic element 35a is installed near the antenna 31, as shown in Figures 32A and 32B. This makes it possible to improve the directivity of the rearward-positioned antenna 31.

[0192] Furthermore, in the vehicle-mounted antenna device 15 shown in Figure 28B above, two antennas 32 were arranged vertically. Two parasitic elements 72 were positioned above the radiating element 71 of the upper antenna 32. However, as in the vehicle-mounted antenna device 16 shown in Figure 32A, one antenna 32 may be arranged, and one parasitic element 72 may be positioned above the radiating element 71. Moreover, as in the vehicle-mounted antenna device 17 shown in Figure 32B, one antenna 32 may be arranged, and two parasitic elements 72 may be positioned above the radiating element 71.

[0193] <<Vehicle-mounted antenna device 18 (9th embodiment), and vehicle-mounted antenna device 19 (10th embodiment)>> Figure 33 is a perspective view of the vehicle-mounted antenna devices 18 and 19. Figure 33A is a perspective view of the vehicle-mounted antenna device 18, and Figure 33B is a perspective view of the vehicle-mounted antenna device 19.

[0194] In the vehicle-mounted antenna device 10 shown in Figure 1 above, a monopole antenna 30 was positioned at the front, and a collinear antenna array 31 was positioned at the rear. In the vehicle-mounted antenna device 11 shown in Figure 11 above, a monopole antenna 34 and passive elements 35 and 36 were positioned at the front, and a collinear antenna array 31 was positioned at the rear.

[0195] However, the placement of the antenna at the front and the antenna at the rear are not limited to the cases described above. As shown in the vehicle-mounted antenna device 18 in Figure 33A, both the front and rear may have a monopole antenna 34 and parasitic elements 35 and 36. Also, as shown in the vehicle-mounted antenna device 19 in Figure 33B, the front may have a monopole antenna 34 and parasitic elements 35 and 36, and the rear may have a monopole antenna 30. Furthermore, although not shown, the vehicle-mounted antenna devices 18 and 19 described above are not the only possibilities; for example, patch antennas may be placed both at the front and rear.

[0196] Furthermore, in the vehicle-mounted antenna device 15 shown in Figure 28B above, two antennas 32 were arranged vertically. Two parasitic elements 72 were positioned above the radiating element 71 of the upper antenna 32. However, as in the vehicle-mounted antenna device 18 shown in Figure 33A, two antennas 32 may be arranged vertically, with one parasitic element 72 positioned above the radiating element 71.

[0197] <<<<Summary>>>>> The vehicle-mounted antenna devices 10 to 19 of this embodiment have been described above. For example, in the vehicle-mounted antenna device 14, the antenna 30 corresponding to the V2X frequency band is located in close proximity to the case 22. Therefore, the vehicle-mounted antenna device 14 can appropriately respond to radio waves of a desired frequency band (for example, V2X radio waves).

[0198] Furthermore, in this embodiment, the in-vehicle antenna device 14 is positioned at a distance of approximately 75 mm or less (for example, 5 mm) from the position where the antenna 30 contacts the case 22, which is 3 / 2 of the wavelength λ of the V2X frequency band. For example, as shown in Figures 5 and 7, the directivity can be improved by positioning the antenna 30 at a distance of 3 / 2 of the wavelength λ of the V2X frequency band from the case 22. As mentioned above, in Figure 7, the position where Db = 90 mm is 76 mm away from the position where it contacts the case 22.

[0199] Furthermore, in this embodiment, the in-vehicle antenna device 14 is positioned at a distance of approximately 50 mm or less (for example, 5 mm) from the position where the antenna 30 contacts the case 22, which is one wavelength λ of the V2X frequency band. For example, as shown in Figures 5 and 7, the directivity can be further improved by positioning the antenna 30 at a distance of one wavelength λ or less from the case 22. As mentioned above, in Figure 7, the position where Db = 64 mm is 50 mm away from the position where it contacts the case 22.

[0200] Furthermore, in the in-vehicle antenna device 10, for example, each of the antennas 30 and 31 corresponding to the V2X frequency band is positioned close to the case 22. Therefore, the in-vehicle antenna device 10 can appropriately respond to radio waves of a desired frequency band (for example, V2X radio waves).

[0201] Incidentally, it is also possible to install an antenna corresponding to the front V2X near the vehicle's windshield, and an antenna corresponding to the rear V2X on a shark fin-type in-vehicle antenna device. However, in such a configuration, it is necessary to connect a long transmission cable from near the vehicle's windshield to the in-vehicle antenna device. In this embodiment, antennas 30 and 31 with good directivity can be housed in the in-vehicle antenna device 10 with a simple configuration.

[0202] Furthermore, in this embodiment, antennas 30 and 31 are positioned at a distance of approximately 75 mm or less (for example, 5 mm) from the position where each antenna 30 and 31 contact the case 22, which is 3 / 2 of the wavelength λ of the V2X frequency band. For example, as shown in Figures 5 and 7, the directivity can be improved by positioning antennas 30 and 31 at a distance of 3 / 2 of the wavelength λ of the V2X frequency band from the case 22. As mentioned above, in Figure 7, the position where Db = 90 mm is 76 mm away from the position where it contacts the case 22.

[0203] Furthermore, in this embodiment, antennas 30 and 31 are positioned at a distance of approximately 50 mm or less (for example, 5 mm) from the position where each antenna 30 and 31 contact the case 22, which is one wavelength λ of the V2X frequency band. For example, as shown in Figures 5 and 7, the directivity can be further improved by positioning antennas 30 and 31 at a distance of one wavelength λ or less from the case 22. As mentioned above, in Figure 7, the position where Db = 64 mm is 50 mm away from the position where it contacts the case 22.

[0204] Furthermore, as shown in Figure 10, for example, the antennas 30 and 31 have different directions in which their gain increases. By using such antennas 30 and 31, the vehicle-mounted antenna device 10 can receive a wider range of radio waves in the desired frequency band.

[0205] Furthermore, antenna 30 is installed on the front substrate 40 of the metal base 21, and antenna 31 is installed on the rear substrate 41. By arranging antennas 30 and 31 separately in this way, it becomes possible to install other antennas 32 and 33 between antennas 30 and 31, thereby suppressing interference between antennas.

[0206] Furthermore, antennas 32 and 33 are provided between antennas 30 and 31 to correspond to radio waves in a frequency band different from the V2X frequency band.

[0207] Furthermore, in this embodiment, as shown in Figure 8, the front antenna 30 is positioned with its tip P1 separated to the rear by a distance D1. In addition, as shown in Figure 9, the rear antenna 31 is positioned with its end P2 of the straight section 60 separated to the front by a distance D2. By separating the front antenna 30 to the rear and the rear antenna 31 to the front of the case 22 in this way, the directivity of the vehicle-mounted antenna device 10 can be improved.

[0208] Furthermore, antenna 30 has a higher gain in the forward direction (+x direction), while antenna 31 has a higher gain in the backward direction (-x direction), so the directions in which the gains of the two antennas are higher are different. By using such antennas 30 and 31, the vehicle-mounted antenna device 10 can obtain near-ideal directivity (omnidirectional) in the desired frequency band.

[0209] Furthermore, since case 22 has a so-called shark fin shape, its front height is lower than its rear height. When housing two V2X antennas in such case 22, in this embodiment, the height of the front antenna 30 is lower than the height of the rear antenna 31. By combining antennas of different heights and shapes in this way, the directivity of radio waves in the V2X frequency band can be improved.

[0210] Furthermore, in the in-vehicle antenna device 15, as shown in Figure 28B, an antenna 31 corresponding to radio waves in the V2X frequency band is housed in a housing space formed by the antenna base 20 and the case 22. At least a portion of the antenna 31 is positioned close to the case 22.

[0211] Furthermore, as shown in Figure 28B, the vehicle-mounted antenna device 15 is housed in a housing space formed by the antenna base 20 and the case 22, and further includes an antenna 32 that corresponds to GNSS band radio waves. Antenna 31 has a circuit 63 that suppresses the GNSS band signals corresponding to antenna 32, as shown in Figure 29. This mitigates the impact on the axial ratio performance of antenna 32 that corresponds to GNSS band radio waves, and makes it possible to position antenna 31 in close proximity to antenna 32.

[0212] Furthermore, the following matters become clear from the description and drawings mentioned above.

[0213] One aspect of the present invention is an in-vehicle antenna device comprising a base, a case that together with the base forms a housing space, a first antenna and a second antenna housed in the housing space and corresponding to radio waves of a desired same frequency band, and a third antenna located between the first antenna and the second antenna, wherein at least a portion of the first antenna and at least a portion of the second antenna are positioned in close proximity to the case.

[0214] In this embodiment, "vehicle-mounted" means that it can be placed on a vehicle, and therefore it is not limited to devices attached to a vehicle, but also includes devices that are brought into a vehicle and used inside the vehicle. Furthermore, although the antenna device in this embodiment is intended to be used on a "vehicle," which is a wheeled vehicle, it is not limited to this, and may also be used on other mobile devices such as drones and other flying objects, probes, construction machinery without wheels, agricultural machinery, ships, etc.

[0215] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. Furthermore, the present invention may be modified or improved without departing from its spirit, and it goes without saying that equivalents thereof are included. [Explanation of symbols]

[0216] 10-19 Vehicle-mounted antenna devices 20 Antenna base 21,500 Metal base 22,300,400,501 cases Antennas 30-34, 37, 310, 410, 510-513, 90, 94 35, 35a, 36, 72 Unpowered element 37a Patch element 37b Ground Conductor Plate 38 Top 39 Slope 40-42 circuit boards 43, 45, 48 screws 44,46 Coaxial Cable 47 Holder 49, 50 Receiving part 51, 52 Cable housing section 60,62a Straight section 61 Ring section 62b Folded section 63 circuits 70 Dielectric material 71 Radiating element 80 Holder 81,91 Helical element (coil) 82,92 Capacitive Loading Elements 93 Slits 95 Metal body 320,420 Main plate 300a, 400a Top surface 300b, 400b Cylindrical member P1,P3,P5 Tip P2 end P4 Corner

Claims

1. Bass and, A case that forms a housing space together with the aforementioned base, A first antenna, housed in the aforementioned housing space and corresponding to radio waves in a desired frequency band, Equipped with, The first antenna corresponds to linear polarization, At least a portion of the first antenna is positioned in close proximity to the case. The aforementioned proximity position is a position where at least a portion of the first antenna is separated by a predetermined distance horizontally from the position where at least a portion of the first antenna is in contact with the case. The predetermined distance is the distance between at least a part of the first antenna and the case, and is less than or equal to 3 / 2 of the wavelength of the desired frequency band. Vehicle-mounted antenna device.

2. The antenna device according to claim 1, The predetermined distance is a distance of one wavelength or less of the desired frequency band. Vehicle-mounted antenna device.

3. An antenna device according to either claim 1 or 2, A second antenna housed in the aforementioned housing space and corresponding to radio waves in the same frequency band as the desired frequency band, A third antenna located between the first antenna and the second antenna, Equipped with, At least a portion of the second antenna is positioned in close proximity to the case. Vehicle-mounted antenna device.

4. The antenna device according to claim 3, The aforementioned close proximity is a position where at least a portion of the first antenna and at least a portion of the second antenna are separated by a predetermined distance horizontally from the position where at least a portion of the first antenna and at least a portion of the second antenna are in contact with the case. The predetermined distance is a distance of 2 / 3 or less of the wavelength of the desired frequency band. Vehicle-mounted antenna device.

5. The antenna device according to claim 4, The predetermined distance is a distance of one wavelength or less of the desired frequency band. Vehicle-mounted antenna device.

6. An antenna device according to any one of claims 3 to 5, The first antenna and the second antenna are arranged such that the direction in which their respective gains increase is different. Vehicle-mounted antenna device.

7. An antenna device according to any one of claims 3 to 6, The base further comprises a plurality of substrates on which the first antenna and the second antenna are each arranged. Vehicle-mounted antenna device.

8. An antenna device according to any one of claims 3 to 7, The third antenna corresponds to radio waves in a frequency band different from the desired frequency band. Vehicle-mounted antenna device.

9. An antenna device according to claim 4 or claim 5, The position in which at least a part of the first antenna is in close proximity is a first position located a predetermined distance away from the position where at least a part of the first antenna contacts the case on the first direction side of a predetermined horizontal axis, in the second direction opposite to the first direction. The position in which at least a portion of the second antenna is in close proximity is a second position located a predetermined distance away in the first direction from the position where the case on the second direction side and at least a portion of the second antenna come into contact. Vehicle-mounted antenna device.

10. The antenna device according to claim 9, The first antenna has a larger gain in the first direction than in the first and second directions. The second antenna has a larger gain in the second direction than in the first direction. Vehicle-mounted antenna device.

11. An antenna device according to claim 9 or claim 10, The height of the first antenna from the base is lower than the height of the second antenna from the base. The height of the case from the base at the first position is lower than the height of the case from the base at the second position. Vehicle-mounted antenna device.

12. An antenna device according to either claim 1 or 2, The aforementioned housing space is further equipped with a second antenna that is compatible with radio waves in a frequency band different from the desired frequency band, The first antenna has a circuit to suppress signals in the corresponding frequency band of the second antenna. Vehicle-mounted antenna device.

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