Antenna device, dipole antenna, and vehicle

Abstract

This antenna device is compatible with linearly polarized waves and comprises: an antenna element extending from a feed unit in a first direction; and a ground element extending from the feed unit in a second direction intersecting the first direction. The ground element is a conductor frame of a vehicle. The angle between the first direction and the second direction is less than 90 degrees and equal to or greater than 15 degrees.

Description

Antenna device, dipole antenna and vehicle

[0001] The present invention relates to an antenna device, a dipole antenna and a vehicle.

[0002] Patent Document 1 describes an antenna device in which an antenna element is installed in a spoiler of a vehicle.

[0003] Japanese Unexamined Patent Application Publication No. 2003-309414

[0004] In the antenna device of Patent Document 1, a wide conductor surface serving as a ground (for example, the roof of a vehicle) is required to operate as a monopole antenna. It is also necessary to install the antenna element as far away as possible from other conductors (for example, the vehicle body). That is, when installing the antenna device in a vehicle, it has been difficult to freely lay out the antenna device due to constraints on electrical performance, installation location, and the like.

[0005] An example of an object of the present invention is to improve the layout flexibility of an antenna device in a vehicle. Other objects of the present invention will become apparent from the description of the present specification.

[0006] One aspect of the present invention is an antenna device compatible with linearly polarized waves, comprising: an antenna element extending from a feeding part in a first direction; and a ground element extending from the feeding part in a second direction intersecting the first direction, wherein the ground element is a conductor frame of a vehicle, and an angle formed by the first direction and the second direction is smaller than 90 degrees and not smaller than 15 degrees.

[0007] One aspect of the present invention is an antenna device compatible with linearly polarized waves, comprising: an antenna element extending from a feeding part in a first direction; a first ground element extending from the feeding part in a second direction intersecting the first direction; a second ground element extending from the feeding part in a direction substantially opposite to the second direction; and a third ground element extending from the feeding part in a third direction intersecting the first direction and the second direction, wherein at least one of the first ground element, the second ground element, and the third ground element is a conductor frame of a vehicle.

[0008] One aspect of the present invention is an antenna device for linear polarization, comprising: an antenna element extending in a first direction from a feed point; a first ground element extending in a second direction intersecting the first direction from the feed point; and a second ground element positioned at a predetermined distance from the feed point on the first ground element and extending in a third direction intersecting the second direction, wherein at least one of the first ground element and the second ground element is a conductor frame of a vehicle.

[0009] One aspect of the present invention is an antenna device for linear polarization, comprising: an antenna element extending in a first direction from a feed point; a first ground element extending in a second direction intersecting the first direction from the feed point; and a second ground element extending in a third direction substantially opposite to the first direction from the feed point, wherein at least one of the first ground element and the second ground element is a conductor frame of a vehicle, and the length of the second ground element is shorter than the length of the first ground element.

[0010] According to the above-described aspect of the present invention, the degree of freedom in the layout of the antenna device in a vehicle can be improved.

[0011] This is a perspective view of a vehicle 1 on which the antenna device 10 of this embodiment is installed. This is an exploded perspective view of the antenna device 10 of this embodiment. This is an explanatory diagram showing an overview of how the outer conductor 182 of the coaxial cable 18 is electrically connected to the conductor frame 2 of the vehicle 1. This is an explanatory diagram showing details of how the outer conductor 182 of the coaxial cable 18 is electrically connected to the conductor frame 2 of the vehicle 1. This is a diagram showing an example of the frequency characteristics of the gain in the vertical polarization component of the dipole antenna 20. This is a diagram showing an example of the frequency characteristics of the gain in the horizontal polarization component of the dipole antenna 20. This is a diagram showing an example of the average gain of the antenna device 10 at different installation locations. This is an explanatory diagram of modified antenna device 10A and dipole antenna 20A. This is an explanatory diagram of the antenna device 210. This is a diagram showing an example of the characteristics of the antenna device 210. This is an explanatory diagram of the antenna device 310. This is a diagram showing an example of the characteristics of the antenna device 310. This is an explanatory diagram of the antenna device 410. This is a diagram showing an example of the relationship between the current value flowing through the second ground element 432 and the distance d1. This is a diagram showing an example of the characteristics of the antenna device 410. This is a diagram showing an example of the characteristics of the antenna device 410 at different lengths L9. This figure shows an example of the characteristics of the antenna device 410 with and without a coil. This is an explanatory diagram of the antenna device 510. This figure shows an example of the characteristics of the antenna device 510 with a length difference of L12.

[0012] The following matters become clear from this specification and the accompanying drawings:

[0013] 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.

[0014] ==This Embodiment== Figure 1 is a perspective view of a vehicle 1 on which the antenna device 10 of this embodiment is installed.

[0015] <<Definition of Direction, etc.>> First, with reference to Figure 1, we define the direction, etc. in the antenna device 10 of this embodiment.

[0016] As shown in Figure 1, the direction forward as viewed from the driver's seat of the vehicle 1 on which the antenna device 10 is installed is defined as the +X direction (forward direction) of the antenna device 10, the direction left as viewed from the driver's seat of the vehicle 1 is defined as the +Y direction (left direction) of the antenna device 10, and the direction upward as viewed from the driver's seat of the vehicle 1 is defined as the +Z direction (upward direction) of the antenna device 10. The opposite directions of the +X direction, +Y direction, and +Z direction are defined as the -X direction (rear direction), -Y direction (right direction), and -Z direction (downward direction), respectively.

[0017] The +X, -X, +Y, -Y, +Z, and -Z directions are all unidirectional (directions with a fixed orientation). Furthermore, directions that are not unidirectional, such as both the +X and -X directions, are sometimes simply referred to as the "X direction." Similarly, directions that are both the +Y and -Y directions are sometimes simply referred to as the "Y direction." Also, directions that are both the +Z and -Z directions are sometimes simply referred to as the "Z direction."

[0018] In Figure 1, the +X, +Y, and +Z directions are represented by line segments with arrows to facilitate understanding of the direction of the antenna device 10. Note that the intersection of these line segments with arrows does not represent the coordinate origin.

[0019] Unless otherwise specified, the definitions of directions and other terms described above are common to other embodiments of this specification.

[0020] <<Overview of Antenna Device 10>> Next, an overview of the antenna device 10 of this embodiment will be described, referring again to Figure 1 described above.

[0021] As shown in Figure 1, the antenna device 10 is an antenna device installed on the vehicle 1. The body of the vehicle 1 has a frame (hereinafter sometimes referred to as "conductor frame 2") formed of a conductor (for example, metal) as a structural element. Examples of conductor frame 2 on the side of the vehicle body include the A-pillar (front pillar) 2A, the B-pillar (center pillar) 2B, and the C-pillar (rear pillar) 2C. Examples of conductor frame 2 on the roof of the vehicle body include the front roof 2D, the center reinforcement 2E, the rear roof 2F, and the side roof 2G.

[0022] In the conductor frame 2 of the vehicle 1 illustrated above, a lattice structure is formed by combining conductor portions extending in predetermined directions. Specifically, the conductor frame 2 has a lattice structure formed by conductor portions extending in the vertical direction (here, the Z direction) and conductor portions extending in the horizontal direction (here, the direction perpendicular to the Z direction). In the following explanation, the conductor portion extending in the vertical direction (Z direction) may be called the "first conductor portion," and the conductor portion extending in the horizontal direction (the direction perpendicular to the Z direction) may be called the "second conductor portion." However, the direction in which the first conductor portion extends does not have to be strictly vertical; it is sufficient that it has a predetermined angle of 0 degrees or more with respect to the horizontal plane (a direction rising at a predetermined angle). Similarly, the direction in which the second conductor portion extends does not have to be strictly horizontal; it is sufficient that the angle with respect to the horizontal plane is smaller than the angle of the first conductor portion with respect to the horizontal plane (the predetermined angle mentioned above).

[0023] In the conductor frame 2 of the vehicle 1 illustrated above, as shown in Figure 3, the A-pillar 2A, B-pillar 2B, and C-pillar 2C correspond to the first conductor portion, and the front roof 2D, center reinforcement 2E, rear roof 2F, and side roof 2G correspond to the second conductor portion. The antenna device 10 of this embodiment is installed at the intersection of the first conductor portion and the second conductor portion, specifically at the intersection 3 between the B-pillar 2B and the center reinforcement 2E. However, the antenna device 10 may also be installed at a predetermined location on the conductor frame 2 other than the intersection 3 shown in Figure 1, such as the intersection of the A-pillar 2A and the front roof 2D.

[0024] Furthermore, the antenna device 10 may be installed in various locations other than the conductor frame 2 of the vehicle 1, as long as the ground-side conductor 32, described later, is electrically connected to the conductor frame 2. For example, the antenna device 10 may be installed on the roof panel, windshield, rear window, glass roof, side mirrors, inside the instrument panel, the top of the dashboard, the overhead console, the bumper, the license plate mounting area, the spoiler, etc. of the vehicle 1. In this way, the antenna device 10 can be freely laid out in various locations on the vehicle.

[0025] As shown in Figure 1, the antenna device 10 of this embodiment is arranged along the back surface of the conductor frame 2 (specifically, the center reinforcement 2E) of the vehicle 1, and is arranged so that the antenna device 10 and the conductor frame 2 overlap when viewed from outside the conductor frame 2. In this embodiment, even when the antenna device 10 is arranged so that it overlaps with the conductor frame 2, the effects of deterioration of gain and other such issues can be reduced, as will be described later. Furthermore, deterioration of the aesthetic appearance of the vehicle 1 due to the antenna device 10 being visible from the outside can also be suppressed. However, the antenna device 10 does not have to be arranged so that the entire antenna device 10 and the conductor frame 2 overlap when viewed from outside the conductor frame 2. The antenna device 10 may be arranged so that a part of the antenna device 10 and the conductor frame 2 overlap, or the antenna device 10 and the conductor frame 2 may be arranged so that they do not overlap.

[0026] In this example, the vehicle 1 shown in Figure 1 is equipped with one antenna device 10. However, the vehicle 1 is not limited to having only one antenna device 10; multiple antenna devices 10 may be installed on the vehicle 1. Furthermore, the multiple antenna devices 10 installed on the vehicle 1 may support diversity communication methods or MIMO (Multiple-Input Multiple-Output) communication. In addition, the antenna device 10 may be arranged in the same enclosure in combination with other antennas (monopole antennas or planar antennas). In that case, it may be installed on the vehicle 1 as a system unit consisting of multiple antennas.

[0027] The configuration in which the antenna device 10 is installed on the vehicle 1 is not limited to the configuration in which it is attached to the vehicle 1, but also includes the configuration in which it is brought into the vehicle 1 and used within the vehicle 1. Furthermore, "vehicle" means a vehicle with wheels, and examples include ordinary automobiles such as passenger cars, buses, and trucks, motorcycles and other two-wheeled vehicles, and special vehicles (industrial vehicles) such as tractors, bulldozers, and other specialized vehicles.

[0028] The antenna device 10 of this embodiment is compatible with radio broadcasts, for example, radio waves in the frequency band for AM / FM radio. That is, the antenna device 10 is compatible with both radio waves in the frequency band for AM broadcasting from 522 kHz to 1710 kHz and radio waves in the frequency band for FM broadcasting from 76 MHz to 108 MHz. However, the antenna device 10 may be compatible with only one of the frequency bands, either the AM broadcasting frequency band or the FM broadcasting frequency band.

[0029] The communication standards and frequency bands supported by the antenna device 10 are not limited to those described above, and other communication standards may also be supported. For example, the antenna device 10 may support radio waves in frequency bands for TEL (Telephone), telematics, and V2X (Vehicle to Everything: vehicle-to-vehicle communication, vehicle-to-infrastructure communication), such as 4G, 5G, and LTE. Furthermore, the antenna device 10 may support radio waves in frequency bands for GNSS (Global Navigation Satellite System), SXM (Sirius XM), ETC (Electronic Toll Collection system), Wi-Fi, Bluetooth, DAB, DTV, and KEYLESS.

[0030] <<Basic Configuration of Antenna Device 10>> Next, the basic configuration of the antenna device 10 of this embodiment will be described with reference to Figure 2.

[0031] Figure 2 is an exploded perspective view of the antenna device 10 of this embodiment.

[0032] The antenna device 10 includes a case 11A and a base 11B, a pad 12, a plate-shaped element 13, a bobbin 14, a helical element 15, a substrate 16, and cables 17A and 17B. Figure 2 shows an exploded perspective view of the antenna device 10 with only the case 11A moved in the +Z direction.

[0033] Case 11A and base 11B are components that constitute the exterior of the antenna device 10. Case 11A is located on the +Z direction side of the antenna device 10 and is formed in the shape of a plate. Similarly, base 11B is located on the -Z direction side of the antenna device 10 and is formed in the shape of a plate. The antenna device 10 is installed on the vehicle 1 by attaching base 11B to a predetermined location on the vehicle 1. However, the orientation in which the antenna device 10 is installed relative to the vehicle 1 is not limited to the orientation shown in Figure 2 (i.e., the orientation in which the antenna device 10 is installed with case 11A on the +Z direction side and base 11B on the -Z direction side), and may be any orientation.

[0034] Case 11A and base 11B are formed from an insulating resin such as PC resin, ASA resin, PC / ASA resin composition, or ABS resin. However, case 11A and base 11B may be formed from a material other than an insulating resin that transmits radio waves. Furthermore, case 11A and base 11B may consist of an insulating resin portion and a portion made of a material other than an insulating resin that transmits radio waves. In addition, parts of case 11A and base 11B may be made of a conductive material or a material that does not transmit radio waves. That is, case 11A and base 11B may be formed by freely combining desired materials, and case 11A and base 11B may be made of different materials.

[0035] The case 11A and the base 11B form a housing space for accommodating the plate-shaped element 13, bobbin 14, helical element 15, substrate 16, cable 17A, and cable 17B. The case 11A and the base 11B are attached to each other by a desired mounting means such as screw fastening, snap fitting, welding, or adhesive.

[0036] The pad 12 is a component positioned between the case 11A and the base 11B. The pad 12 is compressed by being sandwiched between the case 11A and the base 11B, thereby ensuring the waterproofness of the housing space of the antenna device 10. The pad 12 is formed of an elastic material such as TPE or rubber (such as NBR or EPDM). However, the pad 12 may be formed of other elastic materials.

[0037] The plate-shaped element 13, together with the helical element 15, is an element that corresponds to radio waves in the frequency band for AM / FM radio. The plate-shaped element 13 is a capacitive element in an antenna for AM / FM radio, and is sometimes called a capacitively charged element. The -Y end of the plate-shaped element 13 is electrically connected to the +X end of the helical element 15. Here, "electrically connected" is not limited to physical (direct) connections, such as joining objects with a conductor such as solder, but also includes indirect connections, such as connecting via electronic circuits or electronic components. The same applies to the following explanation of "electrically connected".

[0038] In the antenna device 10 of this embodiment, the plate-shaped element 13 is built into the housing (i.e., the housing space formed by the case 11A and the base 11B), but the plate-shaped element 13 may be located outside the housing. Also, if the antenna device 10 does not support radio waves in the frequency band for AM broadcasting (for example, if it only supports radio waves in the frequency band for FM broadcasting), the plate-shaped element 13 may not be necessary. This makes it possible to miniaturize the antenna device 10.

[0039] The bobbin 14 is a member that supports the helical element 15. The helical element 15 is wound around the outer surface of the bobbin 14, except for both ends in the X direction. The bobbin 14 is made of an insulating resin such as PC resin, ASA resin, PC / ASA resin composition, or ABS resin. However, the bobbin 14 may be made of a material other than an insulating resin. However, the antenna device 10 does not have to have a bobbin 14. In this case, the helical element 15 may be supported on the substrate 16, or it may be supported on a support member made of a different resin than the bobbin 14.

[0040] The helical element 15, together with the plate-shaped element 13, is an element that corresponds to radio waves in the frequency band for AM / FM radio. However, the antenna device 10 does not have to have the helical element 15. In this case, only the plate-shaped element 13 is the element that corresponds to radio waves in the frequency band for AM / FM radio. The helical element 15 is an inductive element in an antenna for AM / FM radio and is sometimes called a helical element (or simply a "coil"). The +X end of the helical element 15 is electrically connected to the -Y end of the plate-shaped element 13, and the -X end of the helical element 15 is electrically connected to the substrate 16. As a result, the plate-shaped element 13, the helical element 15, and the substrate 16 are electrically connected in series.

[0041] The substrate 16 is a plate-shaped member on which conductor patterns and electronic components such as antenna impedance matching circuits and amplification circuits are arranged. In this embodiment, the substrate 16 is a printed circuit board (PCB), formed from a resin material such as glass epoxy resin, and on which conductor patterns and electronic components are arranged. However, the substrate 16 may be formed from a resin material other than glass epoxy resin, such as phenolic resin, and on which conductor patterns and electronic components are arranged.

[0042] Cable 17A is a cable having a conductor portion (hereinafter sometimes referred to as the "signal line side conductor") through which the signal of the antenna (in this case, the dipole antenna 20 described later) in the antenna device 10 is transmitted. Cable 17B is a cable having a conductor (hereinafter sometimes referred to as the "ground side conductor") that serves as the ground for the antenna (dipole antenna 20) in the antenna device 10. One end of cable 17A on the circuit board 16 side and the circuit board 16 are electrically connected to each other by a joint such as soldering. Similarly, one end of cable 17B on the circuit board 16 side and the circuit board 16 are electrically connected to each other by a joint such as soldering. Cables 17A and 17B are led outwards from the antenna device 10 via a grommet 19.

[0043] The antenna device 10 of this embodiment further includes a coaxial cable 18 (not shown in Figure 2; see Figures 3 and 4 described later). Outside the antenna device 10, cable 17A is electrically connected to the internal conductor 181 of the coaxial cable 18, and cable 17B is electrically connected to the external conductor 182 of the coaxial cable 18. Therefore, in the following description, both cable 17A and the internal conductor 181 of the coaxial cable 18 may be referred to as the "signal line side conductor," and both cable 17B and the external conductor 182 of the coaxial cable 18 may be referred to as the "ground side conductor."

[0044] However, the antenna device 10 does not have to have a coaxial cable 18, nor does it have to have cables 17A and 17B. In other words, the antenna device 10 does not have to be connected by cable. For example, a connector may be attached to the circuit board 16, and the antenna device 10 may be electrically connected to the outside of the antenna device 10 (in this case, the vehicle 1) via this connector. In this case, the circuit board 16 may have a conductor pattern that will be the signal line conductor and a ground pattern that will be the ground conductor. Also, if the antenna device 10 has a coaxial cable 19, the signal line conductor may be made of the internal conductor 181 of the coaxial cable 18, and the ground conductor may be electrically connected directly from the circuit board 16 to the vehicle 1 with a metal terminal.

[0045] <<Overview of Dipole Antenna 20>> Next, an overview of the dipole antenna 20 configured in the present embodiment will be described while referring again to FIG. 2 and additionally referring to FIG. 3 and FIG. 4.

[0046] FIG. 3 is an explanatory diagram illustrating an outline of how an outer conductor 182 of a coaxial cable 18 is electrically connected to a conductor frame 2 of a vehicle 1. FIG. 4 is an explanatory diagram illustrating details of how the outer conductor 182 of the coaxial cable 18 is electrically connected to the conductor frame 2 of the vehicle 1.

[0047] By the way, when a structure that prevents the antenna device from protruding beyond the outer shape of the vehicle body is required, it is particularly necessary to reduce the size of the antenna device. Furthermore, when a glass roof or a resin roof is employed as the vehicle roof, it may become difficult to use the roof as a ground for the antenna device. For an antenna in an antenna device to operate as a monopole antenna, a large conductive surface such as a vehicle roof is required, which consequently limits the locations where the antenna device can be arranged.

[0048] However, the antenna in the antenna device 10 of the present embodiment operates as a dipole antenna. An internal element of the antenna device 10 (the plate-like element 13 and the helical element 15) is used as the element on one side of the dipole antenna, and the conductor frame 2 of the vehicle 1 is used as the element on the other side of the dipole antenna.

[0049] In the present embodiment, the internal elements of the antenna device 10 (the plate-like element 13 and the helical element 15) to which the signal line-side conductor 31 (the inner conductor 181 of the coaxial cable 18) is electrically connected serve as the aforementioned one-side element of the dipole antenna 20. Furthermore, at least a part of the conductor frame 2 of the vehicle 1 to which the ground-side conductor 32 (the outer conductor 182 of the coaxial cable 18) is electrically connected serves as the aforementioned other-side element of the dipole antenna 20. Accordingly, in the antenna device 10 of the present embodiment, the conductor frame 2 of the vehicle 1 can be used as a part of an element of the dipole antenna 20.

[0050] In the following explanation, the elements to which the signal line conductor 31 is electrically connected (here, the plate-shaped element 13 and the helical element 15) will be referred to as the "signal line antenna element," and the conductor frame 2 of the vehicle 1 to which the ground conductor 32 is electrically connected will be referred to as the "ground antenna element."

[0051] When a monopole antenna is placed close to the vehicle body, the current flowing through the antenna element of the monopole antenna is canceled out by the mirror effect with the vehicle body, resulting in a decrease in gain. However, in the antenna device 10 of this embodiment, by using a dipole antenna 20 made from the conductor frame 2 of the vehicle 1, it is possible to place it close to the vehicle body 1. Furthermore, since the conductor frame 2 acts as the opposite antenna of the dipole antenna 20, gain can be ensured. Therefore, in this embodiment, the degree of freedom in the layout of the antenna device 10 on the vehicle 1 can be improved.

[0052] Furthermore, it becomes possible to secure gain even if the antenna element on the antenna device 10 side (signal line side antenna element) is made smaller, allowing the antenna device 10 to be miniaturized. The antenna element on the antenna device 10 side (signal line side antenna element) is sufficiently small relative to the wavelength of the radio wave that the dipole antenna 20 corresponds to (for example, less than one-quarter of the wavelength), thereby ensuring sufficient distance from, for example, noise sources. In addition, the conductor frame 2 of the vehicle 1, which is the antenna on the opposite side of the dipole antenna 10, also functions as a ground by the vehicle body and has low impedance, making it less susceptible to noise. Therefore, the antenna device 10 can also suppress the effects of noise.

[0053] The length of the signal line side antenna element on the antenna device 10 side may be, for example, one-tenth or less of the actual length (physical length) of the ground side antenna element on the conductor frame 2 side. However, if the wavelength of the radio waves that the dipole antenna 20 corresponds to is shorter than the wavelength for AM / FM radio, such as the wavelength of radio waves for telephone, the length of the signal line side antenna element on the antenna device 10 side can be made sufficiently small, so the length of the signal line side antenna element on the antenna device 10 side does not need to be miniaturized to one-quarter of the wavelength of the radio waves that the dipole antenna 20 corresponds to.

[0054] As explained above, the conductor frame 2 of the vehicle 1 is used as the ground-side antenna element of the dipole antenna 20. However, this is not the only option, and a portion of the outer conductor 182 of the coaxial cable 18 may also be used as the ground-side antenna element.

[0055] As shown in Figure 3, the outer conductor 182 of the coaxial cable 18 is electrically connected to the intersection 3 of the B pillar 2B, which is the first conductor portion extending vertically, and the center reinforcement 2E, which is the second conductor portion extending horizontally. In other words, the outer conductor 182 is electrically connected to both the first conductor portion and the second conductor portion. This allows more current to flow in the dipole antenna 20, thereby improving the gain. Furthermore, the dipole antenna 20 can handle both vertically polarized and horizontally polarized signals. However, the outer conductor 182 only needs to be electrically connected to at least one of the ends of the first conductor portion on the second conductor portion side (hereinafter sometimes referred to as the "first end") and the ends of the second conductor portion on the first conductor portion side (hereinafter sometimes referred to as the "second end").

[0056] In this embodiment, the dipole antenna 20 is an antenna for linear polarization. This allows the dipole antenna 20 to improve the gain in both the vertical and horizontal components of the corresponding linear polarization. However, the dipole antenna 20 may be an antenna other than one for linear polarization.

[0057] Furthermore, as shown in Figure 3, the outer conductor 182 is electrically connected to at least one of its first end and second end on the side where the interior angle formed by the first axis X1 and the second axis X2 intersects at the point where the first axis X1, which is along the direction in which the first conductor portion, the B pillar 2B, extends, and the second axis X2, which is along the direction in which the second conductor portion, the center reinforcement 2E, extends. This further improves the gain. However, the outer conductor 182 may also be electrically connected to at least one of its first end and second end on a side other than the side where the interior angle formed by the first axis X1 and the second axis X2 is located.

[0058] The electrical connection between the outer conductor 182 of the coaxial cable 18 and the intersection portion 3 is made, for example, by using a connecting wire 4 made of conductor, in the manner shown in Figure 4. At one end of the connecting wire 4, the outer conductor 182 and the connecting wire 4 are crimped together by a crimping component 4A. At the other end of the connecting wire 4, a fitting 4B is attached and fastened to the hole 3A of the intersection portion 3 with a fastening component 5 such as a bolt. This electrically connects the outer conductor 182 and the intersection portion 3 via the connecting wire 4. However, the electrical connection between the outer conductor 182 of the coaxial cable 18 and the intersection portion 3 is not limited to the method shown in Figure 4. For example, the other end of the connecting wire 4 may be formed in a film-like (planar) shape and placed at the intersection portion 3, thereby connecting the outer conductor 182 and the intersection portion 3 by capacitive coupling. Alternatively, the base 11 may have a metal fixing bracket and be directly fastened to the vehicle body 1.

[0059] <<Characteristics of the Dipole Antenna 20>> Next, the characteristics of the dipole antenna 20 according to this embodiment will be explained using a comparison with a shark fin antenna.

[0060] Figure 5 shows an example of the frequency characteristics of the gain in the vertical polarization component of the dipole antenna 20. Figure 6 shows an example of the frequency characteristics of the gain in the horizontal polarization component of the dipole antenna 20.

[0061] In Figures 5 and 6, the horizontal axis represents frequency, and the vertical axis represents gain. Furthermore, in Figures 5 and 6, the results for the dipole antenna 20 of this embodiment described above are shown with a solid line, and the results for the comparative antenna (shark fin antenna) are shown with a dashed line. Here, the results are shown for the FM broadcast frequency band from 76 MHz to 108 MHz.

[0062] In both the case of the vertical polarization component shown in Figure 5 and the case of the horizontal polarization component shown in Figure 6, the dipole antenna 20 of this embodiment shows better gain results than the antenna of the comparative example. Furthermore, in the case of the comparative example antenna, in both the case of the vertical polarization component and the horizontal polarization component, the gain peaks around 85 MHz, and drops off below that point and to the wider frequency range. However, in the case of the dipole antenna 20 of this embodiment, in the case of the vertical polarization component shown in Figure 5, the gain fluctuations are small across the entire frequency band for FM broadcasting (76 MHz to 108 MHz). Also, in the case of the horizontal polarization component shown in Figure 6, the gain fluctuations relative to the peak are small compared to the comparative example.

[0063] From the above, these results show that the dipole antenna 20 of this embodiment can achieve higher gain and wider bandwidth compared to the shark fin antenna of the comparative example. Therefore, in this embodiment, not only is it possible to miniaturize the antenna device 10, but it is also possible to achieve higher gain and wider bandwidth.

[0064] <<Installation Location of Antenna Device 10>> Figure 7 shows an example of the average gain for different installation locations of the antenna device 10.

[0065] In Figure 7, in vehicle 1, position A is the rear roof 2F, position B is the center reinforcement 2E, position C is the side roof 2G, and position D is the B pillar 2B. As shown in Figure 7, it can be seen that the dipole antenna 20 can secure a stable gain regardless of the installation location.

[0066] <<Modified Version>> Figure 8 is an explanatory diagram of a modified antenna device 10A and dipole antenna 20A.

[0067] In the antenna device 10 of this embodiment described above, one element of the dipole antenna 20 was an element inside the antenna device 10 (a plate-shaped element 13 and a helical element 15), and the other element of the dipole antenna 20 was a conductor frame 2 of the vehicle 1.

[0068] As shown in Figure 8, in the conductor frame 2 of the vehicle 1, some conductor parts (in this case, for example, part of the center reinforcement 2E) may not be electrically connected to other conductor parts by being connected with a resin member or the like. Hereinafter, the conductor parts of the conductor frame 2 that are not electrically connected to other conductor parts may be referred to as "floating conductor parts". In this case, this floating conductor part (part of the center reinforcement 2E) can be used as one element of the dipole antenna 20A, instead of an element inside the antenna device 10A. Alternatively, a conductor part that is electrically connected to other conductor parts and can be used as ground (in this case, the B pillar 2B and the side roof 2G) can be used as the other element of the dipole antenna 20A.

[0069] In other words, in this modified dipole antenna 20, both elements of the dipole antenna 20A use the conductor frame 2 of the vehicle 1, making the antenna device 10A more compact.

[0070] <<Antenna Device 210>> Figure 9 is an explanatory diagram of the antenna device 210. The antenna device 210 has an antenna element 221, a ground element 231 and a feed point 241. In this embodiment, the antenna element 221 and the ground element 231 function as elements of a dipole antenna corresponding to linear polarization.

[0071] The antenna element 221 is a metal member having a length approximately equal to one-quarter of the wavelength of the radio waves in the frequency band corresponding to the antenna device 210. In this embodiment, the antenna element 221 is a rod-shaped member with a length L1. The antenna element 221 extends in the -Y direction from the feed point 241 on the YZ plane.

[0072] The ground element 231 is a metal member having a length of at least one-quarter of the wavelength of the radio waves in the frequency band corresponding to the antenna device 210. In this embodiment, the ground element 231 is a rod-shaped member with a length of L2. The ground element 231 extends from the feed point 241 at an angle θ1 with respect to the -Y direction in the YZ plane. Therefore, the direction in which the ground element 231 extends and the direction in which the antenna element 221 extends intersect at an angle θ1.

[0073] The feeding section 241 is a portion that includes a feeding point where the feed line (not shown) of the antenna device 210 is electrically connected to the antenna element 221 and the ground element 231. The feeding section 241 includes a portion where the inner conductor (not shown) of the feed line of the antenna device 210 is connected to the antenna element 221, and a portion where the outer conductor (not shown) of the feed line of the antenna device 210 is connected to the ground element 231.

[0074] Next, the characteristics of the antenna device 210 in this embodiment will be described. Figure 10 is a graph showing an example of the characteristics of the antenna device 210 when the angle θ1 between the antenna element 221 and the ground element 231 is changed from 0 degrees to 180 degrees. In Figure 10, the solid line represents the vertical polarization gain of the antenna device 210, the dashed line represents the horizontal polarization gain of the antenna device 210, and the dotted line represents the combined value of the vertical polarization gain and horizontal polarization gain of the antenna device 210 (hereinafter referred to as the combined gain value).

[0075] As shown in Figure 10, the vertical polarization gain of the antenna device 210 improves as the angle θ1 decreases in the region from 180 degrees to 75 degrees. Therefore, the vertical polarization gain of the antenna device 210 is better at an angle θ1 of 75 degrees than at an angle θ1 of 90 degrees. Furthermore, the vertical polarization gain of the antenna device 210 remains approximately constant in the region from an angle θ1 of 75 degrees to 15 degrees.

[0076] Generally, it is considered effective to pass a current perpendicular to the antenna element in order to receive or radiate vertical polarization well. However, in this embodiment, vertical polarization can be obtained more effectively by making the angle θ1 between the antenna element 221 and the ground element 231 smaller than 90 degrees.

[0077] Specifically, when the ground element 231 is positioned diagonally (intersecting) with respect to the antenna element 221, the current vector flowing through the ground element 231 can be considered as being decomposed into a horizontal component and a vertical component. In this case, the horizontal component of the current in the ground element 231 is in the same direction as the horizontal current flowing through the antenna element 221, and therefore is not strongly radiated as a horizontal polarization component. As a result, the vertical polarization component is relatively emphasized, and the vertical polarization gain in the antenna device 210 can be improved.

[0078] Therefore, when the primary polarization of the signal targeted by the antenna device 210 is vertical polarization, good vertical polarization characteristics can be obtained by setting the angle θ1 between the antenna element 221 and the ground element 231 to a range of 75 to 15 degrees.

[0079] Furthermore, by making the angle θ1 between the antenna element 221 and the ground element 231 less than 90 degrees, it becomes possible to keep the overall height of the antenna device 210 low while ensuring good vertical polarization gain. This makes it possible to reduce the height of the antenna device 210.

[0080] On the other hand, the horizontal polarization gain of the antenna device 210 decreases as the angle θ1 decreases in the region where the angle θ1 is between 180 degrees and 30 degrees. Also, the horizontal polarization gain of the antenna device 210 tends to improve as the angle θ1 decreases in the region where the angle θ1 is between 30 degrees and 10 degrees.

[0081] When the angle θ1 between the antenna element 221 and the ground element 231 is reduced, the gain of the horizontal polarization component tends to decrease. On the other hand, when the angle θ1 falls below approximately 20 degrees, the vertical current component flowing through the ground element 231 decreases, and consequently, the gain of the vertical polarization component may decrease.

[0082] As a result, in the region where the angle θ1 is around 20 degrees or less, the horizontal polarization component becomes relatively dominant over the vertical polarization component for the antenna device 210 as a whole, and the gain of the horizontal polarization can be improved.

[0083] In other words, in this embodiment, the dominant component in the antenna device 210, horizontal or vertical polarization, changes depending on the angle θ1 formed by the antenna element 221 and the ground element 231. Therefore, when the primary polarization of the signal targeted by the antenna device 210 is horizontal polarization, good horizontal polarization characteristics can be obtained by setting the angle θ1 to a range of 10 to 15 degrees.

[0084] Furthermore, by setting the angle θ1 between the antenna element 221 and the ground element 231 to less than 180 degrees, it becomes possible to reduce the area where the antenna element 221 and the ground element 231 are placed while maintaining the gain characteristics of the antenna device 210. As a result, the overall size of the antenna device 210 can be kept small.

[0085] Furthermore, the combined gain of the antenna device 210 tends to improve as the angle θ1 decreases in the range of 180 degrees to 75 degrees. The combined gain of the antenna device 210 remains approximately constant in the range of 75 degrees to 15 degrees. Therefore, it is preferable to arrange the antenna element 221 and the ground element 231 of the antenna device 210 so that the angle θ1 is less than 90 degrees and 15 degrees or more. In this case, the height of the antenna device 210 can be reduced compared to when the angle θ1 is 90 degrees, thus enabling miniaturization. Moreover, when the primary polarization of the signal targeted by the antenna device 210 is combined, setting the angle θ1 between the antenna element 221 and the ground element 231 to a range of 75 degrees to 15 degrees results in a good combined gain of the antenna device 210.

[0086] The antenna device 210 may be installed on the vehicle 1. In this case, for example, the C-pillar 2C, which is the conductor frame 2 of the vehicle 1, may be used as the ground element 231 of the antenna device 210. By using the conductor frame 2 of the vehicle 1 as the ground element 231, the freedom of layout when mounting the antenna device 210, which is a dipole antenna, on the vehicle 1 is improved.

[0087] In this embodiment, the -Y direction corresponds to the "first direction". The direction that intersects the -Y direction and to which the ground element 231 extends corresponds to the "second direction". The angle θ1 corresponds to the "angle formed by the first direction and the second direction".

[0088] Furthermore, in this embodiment, the main polarization direction can be rotated by approximately 90 degrees by arranging the entire antenna device 210 with respect to the direction in which the antenna element 221 and the ground element 231 extend. For example, by arranging the antenna device 210 with a 90-degree rotation, it is possible to use it as a configuration in which the vertical polarization component is dominant or as a configuration in which the horizontal polarization component is dominant.

[0089] <<Antenna Device 310>> Figure 11 is an explanatory diagram of the antenna device 310 of this embodiment. The antenna device 310 includes an antenna element 321, a first ground element 331, a second ground element 332, a third ground element 333, a feed unit 341, and an electronic component 351. The antenna element 321, the first ground element 331, the second ground element 332, and the third ground element 333 of this embodiment function as elements of a dipole antenna corresponding to linear polarization. Note that the XY plane drawn with a dashed line in Figure 11 is drawn for convenience in explanation and does not represent any planar members.

[0090] The antenna element 321 is a metal component having a length approximately equal to one-quarter of the wavelength of the radio waves in the frequency band corresponding to the antenna device 310. In this embodiment, the antenna element 321 is a rod-shaped component with a length of L3. The antenna element 321 extends in the +X direction from the feed point 341 on the XY plane.

[0091] The first ground element 331, the second ground element 332, and the third ground element 333 are metallic members having a length of at least one-quarter of the wavelength of the radio waves in the frequency band corresponding to the antenna device 310. The first ground element 331, the second ground element 332, and the third ground element 333 extend from the feed point 341 in a direction intersecting the antenna element 321.

[0092] In this embodiment, the first ground element 331 is a rod-shaped metal member with a length of L4. The first ground element 331 extends from the feed point 341 at an angle θ2 with respect to the +X direction in the XY plane. Therefore, the direction in which the first ground element 331 extends and the direction in which the antenna element 321 extends intersect at an angle θ2. In this embodiment, an example is shown where the angle θ2 is 90 degrees, but the angle θ2 is not limited to this. Also, since the antenna element 321 extends in the +X direction, the first ground element 331 extends parallel to the Y direction. The first ground element 331 extends from the feed point 341 in the -Y direction.

[0093] In this embodiment, the second ground element 332 is a rod-shaped metal member with a length of L5. The second ground element 332 extends from the power supply unit 341 in the +Y direction, which is approximately opposite to the -Y direction in which the first ground element 331 extends, on the XY plane.

[0094] In this embodiment, the third ground element 333 is a rod-shaped metal member with a length of L6. The third ground element 333 extends from the power supply unit 341 at an angle θ3 with respect to the XY plane. Therefore, the direction in which the first ground element 331 extends and the direction in which the third ground element 333 extends intersect at an angle θ3. In this embodiment, the angle θ3 is 90 degrees. For this reason, the third ground element 333 extends parallel to the Z direction. The third ground element 333 extends from the power supply unit 341 in the -Z direction.

[0095] The feeding section 341 is a portion that includes a feeding point where the feed line (not shown) of the antenna device 310 is electrically connected to the antenna element 321, the first ground element 331, the second ground element 332, and the third ground element 333. The feeding section 341 includes a portion where the inner conductor (not shown) of the feed line of the antenna device 310 is connected to the antenna element 321, and a portion where the outer conductor (not shown) of the feed line of the antenna device 310 is connected to the first ground element 331, the second ground element 332, and the third ground element 333.

[0096] The electronic component 351 is a component attached to the antenna device 310. The electronic component 351 is, for example, an electronic circuit or electronic device that generates electromagnetic noise, and includes, but is not limited to, an amplification circuit used for purposes other than antennas, a power converter, a microcontroller, a communication module, an in-vehicle ECU, etc. In this embodiment, the electronic component 351 is attached to the vicinity of the -Z side end of the third ground element 333 via mounting parts not shown.

[0097] The electronic component 351 may be electrically grounded to one or more of the first ground element 331, the second ground element 332, and the third ground element 333, or it may not be electrically grounded.

[0098] If the electronic component 351 is electrically grounded to these ground elements, noise generated from the electronic component 351 may affect the antenna device 310 as conducted noise through the ground elements to which the electronic component 351 is electrically grounded.

[0099] On the other hand, if the electronic component 351 is not electrically grounded to these ground elements, noise generated from the electronic component 351 may affect the antenna device 310 as radiated noise via electromagnetic radiation or capacitive coupling.

[0100] In this embodiment, in any of these cases, the influence on the antenna characteristics can be suppressed by placing the electronic component 351 on the ground element side where the antenna current is relatively small.

[0101] Next, the characteristics of the antenna device 310 in this embodiment will be described. Figure 12(a) shows the simulation results of the vertical polarization directivity of the antenna device 310, and Figure 12(b) shows the simulation results of the horizontal polarization directivity of the antenna device 310. The numbers around the graphs shown in Figures 12(a) and (b) indicate the direction (unit: °) in the vertical or horizontal plane. The numbers from the center of the graphs shown in Figures 12(a) and (b) to the direction 0° indicate the gain (unit: dBi).

[0102] In the graph shown in Figure 12(a), an azimuth of 0° corresponds to the +Z direction (upward). An azimuth of 90° corresponds to the +X direction. An azimuth of 180° corresponds to the -Z direction (downward). An azimuth of 270° corresponds to the -X direction. On the other hand, in the graph shown in Figure 4(b), an azimuth of 0° corresponds to the +X direction. An azimuth of 90° corresponds to the -Y direction. An azimuth of 180° corresponds to the -X direction. An azimuth of 270° corresponds to the +Y direction.

[0103] From the graphs in Figures 12(a) and 12(b), it can be seen that the antenna device 310 has a greater gain for horizontal polarization than for vertical polarization. From this, it can be inferred that the magnitude of the current flowing through the first ground element 331 and the second ground element 332, which receive horizontal polarization, is greater than the magnitude of the current flowing through the third ground element 333, which receives vertical polarization. In other words, by providing current paths for multiple ground elements on the same plane, the current paths can be made wider, and the current flowing through the ground elements can be intentionally concentrated.

[0104] Here, the antenna device 310 has an electronic component 351 attached to the third ground element 333. As described above, the magnitude of the current flowing through the third ground element 333 is smaller than the magnitude of the current flowing through the first ground element 331 and the second ground element 332. Therefore, compared to the case where the electronic component 351 is attached to the first ground element 331 or the second ground element 332, when the electronic component 351 is attached to the third ground element 333, the influence of noise generated from the electronic component 351 flowing into the antenna device 310 can be suppressed.

[0105] The antenna device 310 may be installed on the vehicle 1. In this case, at least one of the first ground element 331, the second ground element 332, and the third ground element 333 may be the conductor frame 2 of the vehicle 1.

[0106] For example, the side roof 2G, which is the conductor frame 2 of the vehicle 1, may be used as the first ground element 331 and the second ground element 332 of the antenna device 310, and the B pillar 2B may be used as the third ground element 333. An electronic component 351 is attached to the B pillar 2B used as the third ground element 333. In this case, by arranging the antenna element 321 and the power supply unit 341 in appropriate positions, an antenna device 310 using the conductor frame 2 can be constructed.

[0107] In addition, the antenna device 310 may have a second ground element 332 that is a conductive member electrically connected to the conductor frame 2 as a separate component from the conductor frame 2. With this configuration, it becomes possible to add a conductive member to the antenna device afterwards, and it becomes less constrained by the vehicle structure and the mounting position of the antenna device. As a result, the layout flexibility of the antenna device can be improved. In the antenna device 310 of this embodiment, in order to broaden the current path, for example, by configuring the second ground element 332 to extend from the power supply section 341 in the opposite direction to the direction in which the first ground element 331 extends, the influence of noise from the electronic component 351 arranged on the third ground element 333 can be suppressed.

[0108] In this embodiment, the +X direction corresponds to the "first direction." The direction in which the first ground element 331 extends corresponds to the "second direction." The direction in which the third ground element 333 extends corresponds to the "third direction."

[0109] <<Antenna Device 410>> Figure 13 is an explanatory diagram of the antenna device 410. The antenna device 410 has an antenna element 421, a first ground element 431, a second ground element 432, and a feed unit 441. In this embodiment, the antenna element 421, the first ground element 431, and the second ground element 432 function as elements of a dipole antenna corresponding to linear polarization.

[0110] The antenna element 421 is a metal member having a length approximately equal to one-quarter of the wavelength of the radio waves in the frequency band corresponding to the antenna device 410. In this embodiment, the antenna element 421 is a rod-shaped member with a length of L7. The antenna element 421 extends in the +Y direction from the feed point 441 on the XY plane.

[0111] The first ground element 431 is a metallic member having a length of at least one-quarter of the wavelength of the radio waves in the frequency band corresponding to the antenna device 410. In this embodiment, the first ground element 431 is a rod-shaped member with a length of L8. The first ground element 431 extends from the feed point 441 at an angle θ4 with respect to the antenna element 421 in the XY plane. Therefore, the direction in which the first ground element 431 extends and the direction in which the antenna element 421 extends intersect at an angle θ4. Here, the first ground element 431 extends in the -X direction. Therefore, the angle θ4 is 90 degrees.

[0112] The second ground element 432 is a metallic member having a length of at least one-quarter of the wavelength of the radio waves in the frequency band corresponding to the antenna device 410. In this embodiment, the second ground element 432 is a rod-shaped member with a length of L9. The second ground element 432 extends from the first ground element 431 at an angle θ5 with respect to the direction in which the first ground element extends (in this case, the X direction). Therefore, the direction in which the second ground element 432 extends and the direction in which the first ground element 431 extends intersect at an angle θ5. Here, the second ground element 432 extends in the +Y direction. Therefore, the angle θ5 is 90 degrees. The second ground element 432 is positioned on the first ground element 431 at a distance d1 from the feed point 441.

[0113] The feeding section 441 is a portion that includes a feeding point where the feed line (not shown) of the antenna device 410 is electrically connected to the antenna element 421 and the first ground element 431. The feeding section 441 includes a portion where the inner conductor (not shown) of the feed line of the antenna device 410 is connected to the antenna element 421, and a portion where the outer conductor (not shown) of the feed line of the antenna device 410 is connected to the first ground element 431.

[0114] Next, the characteristics of the antenna device 410 in this embodiment will be described. Figure 14 is a graph showing an example of the relationship between the magnitude of the current flowing through the second ground element 432 and the distance d1 from the feed point 441 to the second ground element 432 in the first ground element 431.

[0115] From the graph in Figure 14, it can be seen that the magnitude of the current flowing through the second ground element 432 of the antenna device 410 increases as the distance d1 decreases. In this case, the magnitude of the current flowing through the first ground element 431 decreases as the magnitude of the current flowing through the second ground element 432 increases, towards the tip side of the part where the second ground element 432 is attached. From this, it can be seen that the magnitude of the current flowing through the first ground element 431 and the second ground element 432 of the antenna device 410 can be adjusted by changing the distance d1.

[0116] Furthermore, adjusting the current path and current distribution in this way is also effective from the standpoint of noise suppression. For example, when placing an electronic component that generates noise near the antenna device 410, by setting the distance d1 to a small value to concentrate the current on the second ground element 432 and placing the electronic component on the first ground element 431 side, the influence of noise flowing into the antenna device 410 can be suppressed.

[0117] Furthermore, in the antenna device 410, the smaller the distance d1 is, and less than or equal to one-eighth of the wavelength of the radio waves in the frequency band corresponding to the antenna device 410 (approximately 350 mm in this case), the larger the current flowing through the second ground element 432 can be.

[0118] Next, Figure 15-17 shows the simulation results of the horizontal directivity of the antenna device 410. The numbers around the graph in Figure 15-17 indicate the direction in the horizontal plane (unit: °). The numbers from the center of the graph in Figure 15-17 to the direction 0° indicate the gain (unit: dBi). Also, in the graph in Figure 15-17, the direction 0° is the +Y direction. The direction 90° is the -X direction. The direction 180° is the -Y direction. The direction 270° is the +X direction.

[0119] In the graph of Figure 15, the solid line shows the results when the distance d1 is 30 mm, the dotted line shows the results when the distance d1 is 50 mm, the dashed line shows the results when the distance d1 is 70 mm, the dashed line shows the results when the distance d1 is 90 mm, and the dashed line shows the results when the distance d1 is 120 mm. From the graph of Figure 15, it can be seen that a null occurs when the distance d1 is 120 mm, while the null becomes shallower when the distance d1 is 90 mm or less.

[0120] Here, it can be seen that the distance d1 from the feed point 441 to the second ground element 432 in the first ground element 431 affects the radiation characteristics of the antenna device 410. In particular, when the length L9 of the second ground element is near one-quarter of the wavelength of the radio waves in the frequency band corresponding to the antenna device 410 (for example, 100 MHz), the second ground element 432 is more likely to resonate electrically, and a null occurs due to the radiation from the first ground element 431 and the second ground element 432.

[0121] Furthermore, if the open ends of the second ground element 432 and the antenna element 421 are close together, the radiation from both elements may spatially influence each other, potentially generating a larger null. In this case, by sufficiently separating the second ground element 432 from the antenna element 421, the mutual influence between the two elements can be reduced, and the generation of nulls can be suppressed. On the other hand, current control becomes more difficult.

[0122] Therefore, in this embodiment, the second ground element 432 is brought sufficiently close to the antenna element 421, so that both elements operate as a single unit and their contribution to radiation is distributed.

[0123] The graph in Figure 15 shows that by setting the distance d1 to less than 1 / 32nd of the wavelength of the radio waves in the frequency band corresponding to the antenna device 410 (approximately 90 mm in this case), the nulls in the radiation pattern can be effectively improved, and stable radiation characteristics can be obtained in all directions.

[0124] In the graph of Figure 16, the solid line shows the results when the length L9 is 700 mm, the dashed line shows the results when the length L9 is 800 mm, and the dotted line shows the results when the length L9 is 600 mm. The result for the solid line in the graph of Figure 16 with a length L9 of 700 mm is the same as the result for the distance d1 of 120 mm in the graph of Figure 15. From the graph of Figure 16, it can be seen that nulls are not generated by changing the length L9 of the second ground element 432. Specifically, by making the length L9 of the second ground element 432 longer or shorter, the antenna device 410 will no longer generate nulls.

[0125] This is because the length L9 of the second ground element 432 affects the radiation characteristics of the antenna device 410. In particular, when the length L9 of the second ground element 432 is near one-quarter of the wavelength of the radio waves in the frequency band corresponding to the antenna device 410, the radiation from the second ground element 432 becomes stronger, and nulls are more likely to occur due to interference with the antenna element 421.

[0126] Therefore, in order to concentrate the current in the second ground element 432 while suppressing the occurrence of nulls in the radiation pattern, the length L9 of the second ground element 432 may be set to avoid the range of one-fifth (approximately 600 mm) to one-quarter (approximately 750 mm) of the wavelength of the radio waves in the corresponding frequency band. If the length L9 of the second ground element 432 is increased, the shape of the second ground element 432 may be made into a meander shape.

[0127] Alternatively, instead of increasing the length L9 of the second ground element 432, a coil or inductor may be attached to the second ground element 432. In the graph of Figure 17, the solid line shows the result when the length L9 is 700 mm, and the dashed line shows the result when the length L9 is 700 mm and a coil is attached. From the graph of Figure 17, it can be seen that even when a coil is attached to the second ground element 432, the antenna device 410 does not generate nulls.

[0128] The antenna device 410 may be installed on the vehicle 1. In this case, at least one of the first ground element 431 and the second ground element 432 may be the conductor frame 2 of the vehicle 1.

[0129] For example, the side roof 2G, which is the conductor frame 2 of the vehicle 1, may be used as the first ground element 431 of the antenna device 410, and the center reinforcement 2E may be used as the second ground element 432. In this case, the antenna device 410 using the conductor frame 2 can be configured by providing the antenna element 421 and the feed point 441 in appropriate positions.

[0130] Furthermore, the antenna device 410 may also have a second ground element 432 that is a conductive member electrically connected to the conductor frame 2 as a separate component from the conductor frame 2. In this case, as described above, by attaching the second ground element 432 to the first ground element 431, the magnitude of the current flowing through the first ground element 431 can be reduced. In particular, if an electronic component that generates electromagnetic noise is attached to the tip side of the first ground element 431, the influence of noise from such an electronic component can be suppressed.

[0131] Furthermore, depending on the placement of electronic components, the noise generated by these components may have a particularly large impact on the antenna characteristics. The area from the feed point 441 to within one-quarter of the wavelength of the radio waves in the frequency band corresponding to the antenna device 410 is a region where a relatively large amount of current flows through both the antenna element and the ground element. For example, if electronic components are placed within one-quarter of the wavelength of the radio waves in the frequency band corresponding to the antenna device 410 from the feed point of the ground element, noise generated by these electronic components is likely to be superimposed on the current flowing through the ground element.

[0132] Therefore, when electronic components are positioned within a range of one-quarter of the wavelength of radio waves in the frequency band corresponding to the antenna device 410 from the power supply unit 441, the influence of noise generated from the electronic components flowing into the antenna device can be suppressed by controlling the current path and current distribution by the configuration of each ground element.

[0133] In this embodiment, the +Y direction corresponds to the "first direction". The direction in which the first ground element 431 extends corresponds to the "second direction". The +Y direction corresponds to the "third direction". d1 corresponds to a "predetermined distance". The corresponding frequency band of the antenna device 410 corresponds to the "first frequency band corresponding to the antenna element".

[0134] <<Modification 4>> Figure 18 is an explanatory diagram of the antenna device 510. The antenna device 510 has an antenna element 521, a first ground element 531, a second ground element 532, and a feed unit 541. In this embodiment, the antenna element 521, the first ground element 531, and the second ground element 532 function as elements of a dipole antenna corresponding to linear polarization.

[0135] The antenna element 521 is a metal member having a length approximately equal to one-quarter of the wavelength of the radio waves in the frequency band corresponding to the antenna device 510. In this embodiment, the antenna element 521 is a rod-shaped member with a length L10. The antenna element 521 extends in the -Y direction from the feed point 541 on the YZ plane.

[0136] The first ground element 531 is a metal member having a length of at least one-quarter of the wavelength of the radio waves in the frequency band corresponding to the antenna device 510. In this embodiment, the first ground element 531 is a rod-shaped member with a length of L11. The first ground element 531 extends from the feed point 541 at an angle θ6 with respect to the antenna element 521 in the YZ plane. Therefore, the direction in which the first ground element 531 extends and the direction in which the antenna element 521 extends intersect at an angle θ6. In this embodiment, an example is shown where the angle θ6 is 60 degrees, but the angle θ6 is not limited to this.

[0137] In this embodiment, the second ground element 532 is a rod-shaped metal member with a length of L12. The second ground element 532 extends from the feed point 541 in the +Y direction, which is approximately opposite to the -Y direction in which the antenna element 521 extends. The length L12 of the second ground element 532 is shorter than the length L11 of the first ground element 531.

[0138] The feeding section 541 is a portion that includes a feeding point where the feed line (not shown) of the antenna device 510 is electrically connected to the antenna element 521, the first ground element 531, and the second ground element 532. The feeding section 541 includes a portion where the inner conductor (not shown) of the feed line of the antenna device 510 is connected to the antenna element 521, and a portion where the outer conductor (not shown) of the feed line of the antenna device 510 is connected to the first ground element 531 and the second ground element 532.

[0139] Next, the characteristics of the antenna device 510 in this embodiment will be described. Figure 19(a) shows the simulation results of the vertical directivity of the antenna device 510, and Figure 19(b) shows the simulation results of the horizontal directivity of the antenna device 510. The numbers around the graphs shown in Figures 19(a) and (b) indicate the direction (unit: °) in the vertical or horizontal plane. The numbers from the center of the graphs shown in Figures 19(a) and (b) to the direction 0° indicate the gain (unit: dBi).

[0140] In the graph shown in Figure 19(a), an azimuth of 0° corresponds to the -Y direction. An azimuth of 90° corresponds to the -X direction. An azimuth of 180° corresponds to the +Y direction. An azimuth of 270° corresponds to the +X direction. On the other hand, in the graph shown in Figure 19(b), an azimuth of 0° corresponds to the +Z direction. An azimuth of 90° corresponds to the -X direction. An azimuth of 180° corresponds to the -Z direction. An azimuth of 270° corresponds to the +X direction.

[0141] In the graphs in Figures 19(a) and 19(b), the solid line shows the results when the length L12 is 800 mm, the dashed line shows the results when the length L12 is 600 mm, and the dotted line shows the results when the length L12 is 400 mm. From the graph in Figure 19(a), it can be seen that shortening the length L12 of the second ground element 532 improves the gain of vertical polarization. This is thought to be because the magnitude of the current flowing through the second ground element 532, which mainly receives horizontally polarized radio waves, decreases, and the magnitude of the current flowing through the first ground element 531, which strongly radiates in the vertical direction, increases.

[0142] On the other hand, the graph in Figure 19(b) shows that even if the length L12 of the second ground element 532 is shortened, the horizontal polarization gain does not change much. From the above, it can be seen that the directivity of the antenna device 510 can be changed by changing the length L12 of the second ground element 532. In particular, by making the length L12 of the second ground element 532 less than one-eighth of the wavelength of the radio waves in the frequency band corresponding to the antenna device 510, it becomes shorter than the resonant length of one-quarter of the wavelength of the radio waves in the frequency band corresponding to the antenna device 510. As a result, the impedance of the second ground element 532 becomes relatively higher than the impedance of the first ground element 531. This makes it easier for current to flow through the first ground element 531 than through the second ground element 532, and the magnitude of the current flowing through the second ground element 532 can be reduced.

[0143] The antenna device 510 may be installed on the vehicle 1. In this case, at least one of the first ground element 531 and the second ground element 532 may be the conductor frame 2 of the vehicle 1.

[0144] For example, the C-pillar 2C, which is the conductor frame 2 of the vehicle 1, may be used as the first ground element 531 of the antenna device 510, and the side roof 2G may be used as the second ground element 532. In this case, by providing the antenna element 521 and the power supply unit 541 in appropriate positions, an antenna device 510 using the conductor frame 2 can be constructed.

[0145] Furthermore, the antenna device 510 may have a first ground element 531 which is a conductive member electrically connected to the conductor frame 2. In this case, as described above, by configuring the first ground element 531 to extend from the feed point 541 so as to intersect the antenna element 521 at an angle θ6, the magnitude of the current flowing through the second ground element 532 can be reduced. In particular, if electronic components such as a power amplifier are attached to the second ground element 532, it is possible to suppress noise generated from such electronic components from flowing into the antenna device.

[0146] In this embodiment, the -Y direction corresponds to the "first direction". The direction in which the first ground element 531 extends corresponds to the "second direction". The +Y direction corresponds to the "third direction". The frequency band that the antenna device 510 corresponds to is the "first frequency band that the antenna element corresponds to".

[0147] The shape of the element is not limited to rod-shaped, plate-shaped, wire-shaped, meander-shaped, etc., and may be a conductive member appropriately designed to obtain the desired electrical characteristics.

[0148] ==Summary== According to this specification, antenna devices in the following embodiments are provided.

[0149] (Aspect 1) Aspect 1 is an antenna device comprising a signal line side conductor, a ground side conductor, and an antenna element to which the signal line side conductor is electrically connected, wherein at least the antenna element and the conductor frame of a vehicle to which the ground side conductor is electrically connected form a dipole antenna.

[0150] According to the above-described embodiment, the degree of freedom in the layout of the antenna device in a vehicle can be improved.

[0151] (Aspect 2) In aspect 2, the conductor frame has a first conductor portion having an angle with respect to the horizontal plane and a second conductor portion whose angle with respect to the horizontal plane is smaller than the angle of the first conductor portion with respect to the horizontal plane, and the ground-side conductor is electrically connected to at least one of the first end of the first conductor portion and the second end of the second conductor portion located on the side of the first end.

[0152] According to the above-described embodiment, a dipole antenna can be formed using at least one of the conductor portion extending vertically and the conductor portion extending horizontally in the grid structure formed on the conductor frame of the vehicle, and the gain can be further improved.

[0153] (Aspect 3) In aspect 3, a first axis along the direction in which the first conductor portion extends and a second axis along the direction in which the second conductor portion extends intersect at a predetermined intersection, and the ground-side conductor is electrically connected to at least one of the first end and the second end on the side where the interior angle formed by the first axis and the second axis at the intersection is located.

[0154] According to the above-described embodiment, a dipole antenna can be formed using at least one of the conductor portion extending vertically and the conductor portion extending horizontally in the grid structure formed on the conductor frame of the vehicle, and the gain can be further improved.

[0155] (Aspect 4) In aspect 4, the dipole antenna is an antenna for linear polarization.

[0156] According to the above-described embodiment, the gain can be improved in both the vertical and horizontal components of linear polarization.

[0157] According to this specification, dipole antennas in the following embodiments are provided.

[0158] (Aspect 5) Aspect 5 is a dipole antenna comprising a signal line side antenna element to which a signal line side conductor is electrically connected, and a ground side antenna element which is at least a vehicle conductor frame to which a ground side conductor is electrically connected.

[0159] According to the above-described embodiment, the degree of freedom in the layout of the antenna device in a vehicle can be improved.

[0160] According to this specification, vehicles in the following embodiments are provided.

[0161] (Aspect 6) In aspect 6, the vehicle comprises a conductor frame and an antenna device, wherein the antenna device has a signal line side conductor, a ground side conductor, and an antenna element to which the signal line side conductor is electrically connected, and the antenna element and the conductor frame to which the ground side conductor is electrically connected form a dipole antenna.

[0162] According to the above-described embodiment, the degree of freedom in the layout of the antenna device in a vehicle can be improved.

[0163] According to this specification, antenna devices in the following embodiments are provided.

[0164] (Aspect 7) Aspect 7 is an antenna device corresponding to linear polarization, comprising an antenna element extending in a first direction from a feed point and a ground element extending in a second direction intersecting the first direction from the feed point, wherein the ground element is a conductor frame of a vehicle, and the angle between the first direction and the second direction is less than 90 degrees and 15 degrees or more.

[0165] According to the above-described embodiment, the height can be reduced compared to the case where the angle between the antenna element and the ground element is 90 degrees, thus enabling the antenna device to be miniaturized.

[0166] (Aspect 8) Aspect 8 is an antenna device corresponding to linear polarization, comprising: an antenna element extending in a first direction from a feed point; a first ground element extending in a second direction intersecting the first direction from the feed point; a second ground element extending in substantially the opposite direction to the second direction from the feed point; and a third ground element extending in a third direction intersecting the first and second directions from the feed point, wherein at least one of the first ground element, the second ground element, and the third ground element is a conductor frame of a vehicle.

[0167] According to the above-described embodiment, current paths for the antenna device can be preferentially formed in the first ground element and the second ground element, and even when electronic components are connected, a configuration can be realized that can suppress the influence of noise generated from electronic components flowing into the antenna device.

[0168] (Aspect 9) In aspect 9, the third ground element is the conductor frame of the vehicle, and the second ground element is a conductive member electrically connected to the conductor frame.

[0169] According to the above-described embodiment, by connecting the second ground element to the vehicle's conductor frame, the constraints imposed by the vehicle structure and the mounting position of the antenna device become less significant, and the layout flexibility of the antenna device can be improved.

[0170] (Aspect 10) In aspect 10, an electronic component is placed on the third ground element.

[0171] According to the above-described embodiment, the influence of noise from electronic components can be suppressed.

[0172] (Aspect 11) Aspect 11 is an antenna device corresponding to linear polarization, comprising: an antenna element extending in a first direction from a feed point; a first ground element extending in a second direction intersecting the first direction from the feed point; and a second ground element positioned at a predetermined distance from the feed point on the first ground element and extending in a third direction intersecting the second direction, wherein at least one of the first ground element and the second ground element is a conductor frame of a vehicle.

[0173] According to the above-described embodiment, by providing a second ground element at a predetermined distance from the power supply unit in the first ground element, the magnitude of the current flowing through the first ground element and the second ground element can be adjusted.

[0174] (Aspect 12) In aspect 12, the predetermined distance is less than or equal to one-eighth of the wavelength of the radio wave in the first frequency band to which the antenna element corresponds.

[0175] According to the above-described embodiment, the magnitude of the current flowing through the second ground element can be increased.

[0176] (Aspect 13) In aspect 13, the first ground element is the conductor frame of the vehicle, and the second ground element is a conductive member electrically connected to the conductor frame of the vehicle.

[0177] According to the above-described embodiment, the magnitude of the current flowing through the first and second ground elements can be adjusted by connecting the second ground element to the conductor frame of the vehicle.

[0178] (Aspect 14) Aspect 14 is an antenna device corresponding to linear polarization, comprising: an antenna element extending in a first direction from a feed point; a first ground element extending in a second direction intersecting the first direction from the feed point; and a second ground element extending in a third direction substantially opposite to the first direction from the feed point, wherein at least one of the first ground element and the second ground element is a conductor frame of a vehicle, and the length of the second ground element is shorter than the length of the first ground element.

[0179] According to the above-described embodiment, the directivity of the antenna device can be changed.

[0180] (Aspect 15) In aspect 15, the length of the second ground element is less than or equal to one-eighth of the wavelength of the radio wave in the first frequency band to which the antenna element corresponds.

[0181] According to the above-described embodiment, the directivity of the antenna device can be changed more significantly.

[0182] (Aspect 16) In aspect 16, the second ground element is the conductor frame of the vehicle, and the first ground element is a conductive member electrically connected to the conductor frame of the vehicle.

[0183] According to the above-described embodiment, the directivity of the antenna device can be changed by connecting the first ground element to the conductor frame of the vehicle.

[0184] 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 the present invention includes equivalents thereof.

[0185] 1 Vehicle, 2 Conductor frame, 10, 210, 310, 410, 510 Antenna device, 20 Dipole antenna, 31 Signal line side conductor, 32 Ground side conductor, 221, 321, 421, 521 Antenna element, 231 Ground element, 331, 431, 531 First ground element, 332, 432, 532 Second ground element, 333 Third ground element, 351 Electronic component

Claims

1. An antenna device for linear polarization, comprising: an antenna element extending in a first direction from a feed point; and a ground element extending in a second direction intersecting the first direction from the feed point, wherein the ground element is a conductor frame of a vehicle, and the angle between the first direction and the second direction is less than 90 degrees and 15 degrees or more.

2. An antenna device for linear polarization, comprising: an antenna element extending in a first direction from a feed point; a first ground element extending in a second direction intersecting the first direction from the feed point; a second ground element extending in substantially the opposite direction to the second direction from the feed point; and a third ground element extending in a third direction intersecting the first and second directions from the feed point, wherein at least one of the first ground element, the second ground element, and the third ground element is a conductor frame of a vehicle.

3. The antenna device according to claim 2, wherein the third ground element is the conductor frame of the vehicle, and the second ground element is a conductive member electrically connected to the conductor frame.

4. The antenna device according to claim 3, wherein an electronic component is arranged on the third ground element.

5. An antenna device for linear polarization, comprising: an antenna element extending in a first direction from a feed point; a first ground element extending in a second direction intersecting the first direction from the feed point; and a second ground element positioned at a predetermined distance from the feed point on the first ground element and extending in a third direction intersecting the second direction, wherein at least one of the first ground element and the second ground element is a conductor frame of a vehicle.

6. The antenna device according to claim 5, wherein the predetermined distance is less than or equal to one-eighth of the wavelength of the radio wave in the first frequency band to which the antenna element corresponds.

7. The antenna device according to claim 5, wherein the first ground element is the conductor frame of the vehicle, and the second ground element is a conductive member electrically connected to the conductor frame of the vehicle.

8. An antenna device for linear polarization, comprising: an antenna element extending in a first direction from a feed point; a first ground element extending in a second direction intersecting the first direction from the feed point; and a second ground element extending in a third direction substantially opposite to the first direction from the feed point, wherein at least one of the first ground element and the second ground element is a conductor frame of a vehicle, and the length of the second ground element is shorter than the length of the first ground element.

9. The antenna device according to claim 8, wherein the length of the second ground element is less than or equal to one-eighth the wavelength of the radio wave in the first frequency band to which the antenna element corresponds.

10. The antenna device according to claim 8, wherein the second ground element is a conductor frame of a vehicle, and the first ground element is a conductive member electrically connected to the conductor frame of the vehicle.

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