Antenna device, dipole antenna, and vehicle

Abstract

Provided 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. At least the antenna element and a conductor frame, of a vehicle, to which the ground-side conductor is electrically connected constitute a dipole antenna. Further provided 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 conductor frame of a vehicle and to which a ground-side conductor is electrically connected. Still further provided is a vehicle comprising a conductor frame and an antenna device. The antenna device includes a signal line-side conductor, a ground-side conductor, and an antenna element to which the signal line-side conductor is electrically connected. The antenna element and the conductor frame to which the ground-side conductor is electrically connected constitute a dipole antenna.

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 inside a spoiler of a vehicle.

[0003] Japanese Patent Application Laid-Open No. 2003-309414

[0004] In order to operate the antenna device of Patent Document 1 as a monopole antenna, a large conductive surface (e.g., the roof of a vehicle) is required as a ground. It is also necessary to install the antenna element as far away as possible from other conductors (e.g., the body of the vehicle). In other words, when installing the antenna device in a vehicle, it is difficult to freely lay out the antenna device due to constraints on electrical performance and installation location.

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

[0006] One aspect of the present invention 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 a conductor frame of a vehicle to which the ground side conductor is electrically connected form a dipole antenna.

[0007] One aspect of the present invention 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 that is at least a conductor frame of a vehicle and to which a ground side conductor is electrically connected.

[0008] One aspect of the present invention is a vehicle comprising 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.

[0009] According to the above aspect of the present invention, it is possible to improve the degree of freedom in the layout of the antenna device in the vehicle.

[0010] 1 is a perspective view of a vehicle 1 on which an antenna device 10 of the present embodiment is installed. FIG. 2 is an exploded perspective view of the antenna device 10 of the present embodiment. FIG. 3 is an explanatory diagram showing an overview of how an outer conductor 182 of a coaxial cable 18 is electrically connected to a conductor frame 2 of the vehicle 1. FIG. 4 is an explanatory diagram showing details of how an outer conductor 182 of a coaxial cable 18 is electrically connected to a conductor frame 2 of the vehicle 1. FIG. 5 is a diagram showing an example of frequency characteristics of gain in a vertically polarized component of a dipole antenna 20. FIG. 6 is a diagram showing an example of frequency characteristics of gain in a horizontally polarized component of a dipole antenna 20. FIG. 7 is a diagram showing an example of average gain for different installation locations of the antenna device 10. FIG. 8 is an explanatory diagram of an antenna device 10A and a dipole antenna 20A of modified examples.

[0011] At least the following matters will become clear from the description of this specification and the accompanying drawings.

[0012] 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 designated by the same reference numerals, and redundant explanations will be omitted where appropriate.

[0013] ==Present Embodiment== FIG. 1 is a perspective view of a vehicle 1 on which an antenna device 10 of this embodiment is installed.

[0014] <<Definition of Directions, Etc.>> First, with reference to FIG. 1, directions, etc. in the antenna device 10 of this embodiment will be defined.

[0015] 1, the forward direction as seen from the driver's seat of the vehicle 1 in which the antenna device 10 is installed is the +X direction (forward direction) of the antenna device 10, the left direction as seen from the driver's seat of the vehicle 1 is the +Y direction (left direction) of the antenna device 10, and the upward direction as seen from the driver's seat of the vehicle 1 is the +Z direction (upward direction) of the antenna device 10. The opposite directions of the +X direction, +Y direction, and +Z direction are the −X direction (rearward direction), −Y direction (rightward direction), and −Z direction (downward direction), respectively.

[0016] Each of the +X direction, -X direction, +Y direction, -Y direction, +Z direction, and -Z direction is a single direction (a direction with a fixed orientation). Furthermore, rather than being a single direction (a direction with a fixed orientation), for example, both the +X direction and the -X direction may be simply referred to as the "X direction." Similarly, both the +Y direction and the -Y direction may be simply referred to as the "Y direction." Furthermore, both the +Z direction and the -Z direction may be simply referred to as the "Z direction."

[0017] 1, the +X direction, +Y direction, and +Z direction are each represented by a line segment with an arrow to facilitate understanding of directions and the like in the antenna device 10. Note that the intersection of these line segments with an arrow does not represent the origin of the coordinate system.

[0018] The above definitions of directions and the like are common to other embodiments in this specification unless otherwise specified.

[0019] <<Outline of Antenna Device 10 >> Next, an outline of the antenna device 10 of this embodiment will be described with reference again to FIG. 1 described above.

[0020] As shown in Fig. 1, the antenna device 10 is an antenna device installed in a vehicle 1. The body of the vehicle 1 has a frame (hereinafter, sometimes referred to as a "conductor frame 2") formed of a conductor (e.g., metal) as a structural body. Examples of the conductor frame 2 in the side portion of the vehicle body include an A-pillar (front pillar) 2A, a B-pillar (center pillar) 2B, and a C-pillar (rear pillar) 2C. Examples of the conductor frame 2 in the ceiling portion of the vehicle body include a front roof 2D, a center reinforcement 2E, a rear roof 2F, and a side roof 2G.

[0021] In the conductor frame 2 of the vehicle 1 illustrated above, a lattice structure is formed by combining conductor portions extending in a predetermined direction. Specifically, the conductor frame 2 has a lattice structure formed by conductor portions extending in a vertical direction (here, the Z direction) and conductor portions extending in a horizontal direction (here, a direction perpendicular to the Z direction). In the following description, the conductor portions extending in the vertical direction (Z direction) may be referred to as "first conductor portions," and the conductor portions extending in the horizontal direction (direction perpendicular to the Z direction) may be referred to as "second conductor portions." However, the extension direction of the first conductor portions does not have to be strictly vertical, as long as they form a predetermined angle of at least 0 degrees with respect to the horizontal plane (a direction rising at a predetermined angle). Similarly, the extension direction of the second conductor portions does not have to be strictly horizontal, as long as their angle with respect to the horizontal plane is smaller than the angle of the first conductor portions with respect to the horizontal plane (the predetermined angle described above).

[0022] In the conductor frame 2 of the vehicle 1 illustrated above, as shown in Fig. 3, the A-pillar 2A, the B-pillar 2B, and the C-pillar 2C correspond to the first conductor portion, and the front roof 2D, the center reinforcement 2E, the rear roof 2F, and the side roof 2G correspond to the second conductor portion. The antenna device 10 of this embodiment is installed at an intersection between the first conductor portion and the second conductor portion, specifically, at an 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 Fig. 1, such as the intersection between the A-pillar 2A and the front roof 2D.

[0023] 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. The antenna device 10 may be installed, for example, on the roof panel, windshield, rear window, glass roof, side mirror, inside the instrument panel, above the dashboard, overhead console, bumper, license plate attachment portion, spoiler, etc. of the vehicle 1. In this way, the antenna device 10 can be installed in any desired location within the vehicle.

[0024] As shown in FIG. 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 the outside of the conductor frame 2. In this embodiment, even when the antenna device 10 is arranged so that the antenna device 10 and the conductor frame 2 overlap, it is possible to reduce the effects of gain degradation, as described below. Furthermore, it is also possible to prevent the aesthetic appearance of the vehicle 1 from being impaired by the antenna device 10 being visible from the outside. However, the antenna device 10 does not have to be arranged so that the entire antenna device 10 overlaps with the conductor frame 2 when viewed from the outside of the conductor frame 2. The antenna device 10 may be arranged so that a portion of the antenna device 10 overlaps with the conductor frame 2, or so that the antenna device 10 and the conductor frame 2 do not overlap.

[0025] Here, one antenna device 10 is installed in the vehicle 1 shown in FIG. However, the number of antenna devices 10 installed in the vehicle 1 is not limited to one, and multiple antenna devices 10 may be installed in the vehicle 1. The multiple antenna devices 10 installed in the vehicle 1 may be compatible with a diversity communication method or may be compatible with MIMO (Multiple-Input Multiple-Output) communication. Furthermore, the antenna device 10 may be combined with another antenna (a monopole antenna or a planar antenna) and placed in the same housing. In this case, the antenna device 10 may be installed in the vehicle 1 as a system unit consisting of multiple antennas.

[0026] The manner in which the antenna device 10 is installed in the vehicle 1 is not limited to the manner in which it is attached to the vehicle 1, but also includes the manner in which it is brought into the vehicle 1 and used within the vehicle 1. Furthermore, the term "vehicle" refers to a vehicle with wheels, and examples thereof include ordinary automobiles such as passenger cars, buses, and trucks, motorcycles such as motorcycles, and special-purpose automobiles (industrial vehicles) such as tractors, bulldozers, and tractors.

[0027] The antenna device 10 of this embodiment is compatible with radio broadcasts, for example, radio waves in the frequency bands for AM and FM radio. That is, the antenna device 10 is compatible with both radio waves in the AM broadcast frequency band of 522 kHz to 1710 kHz and radio waves in the FM broadcast frequency band of 76 MHz to 108 MHz. However, the antenna device 10 may be compatible with only either the AM broadcast frequency band or the FM broadcast frequency band.

[0028] The communication standards and frequency bands supported by the antenna device 10 are not limited to those described above, and other communication standards may be used. For example, the antenna device 10 may be compatible with radio waves in frequency bands for TEL, such as 4G, 5G, and LTE, telematics, and V2X (Vehicle-to-Everything: vehicle-to-vehicle communication and road-to-vehicle communication). The antenna device 10 may also be compatible with radio waves in frequency bands for GNSS (Global Navigation Satellite System), SXM (Sirius XM), ETC (Electronic Toll Collection system), Wi-Fi, Bluetooth, DAB, DTV, KEYLESS, and the like.

[0029] <<Basic Configuration of Antenna Device 10 >> Next, the basic configuration of the antenna device 10 of this embodiment will be described with reference to FIG.

[0030] FIG. 2 is an exploded perspective view of the antenna device 10 of this embodiment.

[0031] The antenna device 10 includes a case 11A, a base 11B, a pad 12, a plate-like element 13, a bobbin 14, a helical element 15, a substrate 16, and cables 17A and 17B. Fig. 2 shows an exploded perspective view of the antenna device 10 in which only the case 11A has been moved in the +Z direction.

[0032] The case 11A and the base 11B are members that constitute the exterior of the antenna device 10. The case 11A is located on the +Z direction side of the antenna device 10 and is formed in a plate shape. Similarly, the base 11B is located on the −Z direction side of the antenna device 10 and is formed in a plate shape. The antenna device 10 is installed on the vehicle 1 by attaching the base 11B to a predetermined location on the vehicle 1. However, the orientation in which the antenna device 10 is installed on the vehicle 1 is not limited to the orientation shown in FIG. 2 (i.e., the orientation in which the antenna device 10 is installed so that the case 11A is located on the +Z direction side and the base 11B is located on the −Z direction side), and may be any orientation.

[0033] The case 11A and the base 11B are formed of an insulating resin such as PC resin, ASA resin, a PC / ASA resin composition, or ABS resin. However, the case 11A and the base 11B may be formed of a material other than insulating resin that is transparent to radio waves. The case 11A and the base 11B may also be composed of an insulating resin portion and a material other than insulating resin that is transparent to radio waves. Furthermore, a portion of the case 11A and the base 11B may be formed of a conductive material or a material that is opaque to radio waves. In other words, the case 11A and the base 11B may be formed of any combination of desired materials, or the case 11A and the base 11B may be formed of different materials.

[0034] The case 11A and the base 11B form a storage space that stores the plate-like element 13, the bobbin 14, the helical element 15, the substrate 16, the cables 17A and 17B. The case 11A and the base 11B are attached to each other by any desired attachment means such as screw fastening, snap fitting, welding, or adhesive.

[0035] The pad 12 is a member disposed between the case 11A and the base 11B. The pad 12 is sandwiched and compressed between the case 11A and the base 11B, thereby ensuring waterproofing of the housing space for the antenna device 10. The pad 12 is formed from an elastic material such as TPE or rubber (NBR, EPDM, etc.). However, the pad 12 may be formed from other elastic materials.

[0036] The plate 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 element 13 is a capacitive element in an antenna for AM / FM radio, and is sometimes called a capacitive loading element. The -Y direction end of the plate element 13 is electrically connected to the +X direction end of the helical element 15. Here, "electrically connected" is not limited to a physical (direct) connection, such as joining objects with a conductor such as solder, but also includes an indirect connection, such as a connection via an electronic circuit or electronic component. The same applies to the following explanation of "electrically connected."

[0037] In the antenna device 10 of this embodiment, the plate-like element 13 is built into the housing (i.e., the storage space formed by the case 11A and the base 11B), but the plate-like element 13 may also be disposed outside the housing. Also, in cases where the antenna device 10 does not support radio waves in the AM broadcast frequency band (i.e., when it supports only radio waves in the FM broadcast frequency band), the plate-like element 13 may not be provided. This allows the antenna device 10 to be made smaller.

[0038] The bobbin 14 is a member that supports the helical element 15. The helical element 15 is wound around the outer peripheral surface of the bobbin 14, except for both ends of the bobbin 14 in the X direction. The bobbin 14 is formed of an insulating resin, such as PC resin, ASA resin, a PC / ASA resin composition, or ABS resin. However, the bobbin 14 may be formed of a material other than insulating resin. However, the antenna device 10 does not need to have the bobbin 14. In this case, the helical element 15 may be supported by the substrate 16, or may be supported by a resin support member different from the bobbin 14.

[0039] The helical element 15, together with the planar element 13, is an element that corresponds to radio waves in the AM / FM radio frequency band. However, the antenna device 10 does not necessarily have to include the helical element 15. In this case, only the planar element 13 is an element that corresponds to radio waves in the AM / FM radio frequency band. The helical element 15 is an inductive element in an AM / FM radio antenna, and is sometimes referred to as a helical element (or simply a "coil"). The +X-direction end of the helical element 15 is electrically connected to the -Y-direction end of the planar element 13, and the -X-direction end of the helical element 15 is electrically connected to the substrate 16. As a result, the planar element 13, the helical element 15, and the substrate 16 are electrically connected in series.

[0040] The substrate 16 is a plate-like member on which conductor patterns and electronic components such as an antenna impedance matching circuit and an amplifier circuit are arranged. The substrate 16 in this embodiment is a printed circuit board (PCB) made of a resin material such as glass epoxy resin, on which the conductor patterns, electronic components, etc. are arranged. However, the substrate 16 may also be made of a resin material other than glass epoxy resin, such as phenolic resin, on which the conductor patterns, electronic components, etc. are arranged.

[0041] Cable 17A is a cable having a conductor portion (hereinafter sometimes referred to as a "signal line side conductor") through which a signal from an antenna (here, a dipole antenna 20 described later) in antenna device 10 is transmitted. Cable 17B is a cable having a conductor (hereinafter sometimes referred to as a "ground side conductor") that serves as the ground for the antenna (dipole antenna 20) in antenna device 10. One end of cable 17A on the substrate 16 side is electrically connected to the substrate 16 by soldering or other bonding. Similarly, one end of cable 17B on the substrate 16 side is electrically connected to the substrate 16 by soldering or other bonding. Cables 17A and 17B are drawn out toward the outside of antenna device 10 via grommets 19.

[0042] The antenna device 10 of this embodiment further includes a coaxial cable 18 (not shown in FIG. 2; see FIGS. 3 and 4 described below). Outside the antenna device 10, the cable 17A is electrically connected to an inner conductor 181 of the coaxial cable 18, and the cable 17B is electrically connected to an outer conductor 182 of the coaxial cable 18. Therefore, in the following description, the inner conductor 181 of the coaxial cable 18 together with the cable 17A may be referred to as a "signal line side conductor," and the outer conductor 182 of the coaxial cable 18 together with the cable 17B may be referred to as a "ground side conductor."

[0043] However, the antenna device 10 may not include the coaxial cable 18, and may not include the cables 17A and 17B. That is, the antenna device 10 does not have to be connected using a cable. For example, a connector may be attached to the substrate 16, and the antenna device 10 may be electrically connected to the outside of the antenna device 10 (here, the vehicle 1) via this connector. In this case, a conductor pattern serving as a signal line side conductor and a ground pattern serving as a ground side conductor may be arranged on the substrate 16. Furthermore, if the antenna device 10 includes the coaxial cable 19, the signal line side conductor may be formed by the inner conductor 181 of the coaxial cable 18, and the ground side conductor may be electrically connected directly from the substrate 16 to the vehicle 1 via a metal terminal.

[0044] <<Outline of Dipole Antenna 20 >> Next, with reference to FIG. 2 again and also with reference to FIGS. 3 and 4, an outline of the dipole antenna 20 configured in this embodiment will be described.

[0045] Fig. 3 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. Fig. 4 is an explanatory diagram showing the details of how the outer conductor 182 of the coaxial cable 18 is electrically connected to the conductor frame 2 of the vehicle 1.

[0046] However, if a structure is required in which the antenna device does not protrude from the exterior of the vehicle body, the antenna device must be particularly compact. Furthermore, if a glass roof or a plastic roof is used as the vehicle roof, it may be difficult to use the roof as the ground for the antenna device. If the antenna in the antenna device were to function as a monopole antenna, a large conductive surface like the vehicle roof would be required, which would limit the space available for laying out the antenna device.

[0047] However, the antenna in the antenna device 10 of this embodiment operates as a dipole antenna. The elements inside the antenna device 10 (the plate element 13 and the helical element 15) are used as one element of the dipole antenna, and the conductor frame 2 of the vehicle 1 is used as the other element of the dipole antenna.

[0048] In this embodiment, the elements (the plate-like element 13 and the helical element 15) inside the antenna device 10 to which the signal line side conductor 31 (the inner conductor 181 of the coaxial cable 18) is electrically connected serve as the above-mentioned one side element of the dipole antenna 20. Also, 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 above-mentioned other side element of the dipole antenna 20. As a result, in the antenna device 10 of this embodiment, the conductor frame 2 of the vehicle 1 can be used as a part of the element of the dipole antenna 20.

[0049] In the following description, the elements (here, the plate-shaped element 13 and the helical element 15) to which the signal line side conductor 31 is electrically connected may be referred to as the "signal line side antenna element," and the conductor frame 2 of the vehicle 1 to which the ground side conductor 32 is electrically connected may be referred to as the "ground side antenna element."

[0050] If 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, the dipole antenna 20 is formed using the conductor frame 2 of the vehicle 1, so it can be placed close to the vehicle body 1. Furthermore, because the conductor frame 2 operates as an antenna on the opposite pole of the dipole antenna 20, gain can be ensured. Therefore, in this embodiment, the degree of freedom in layout of the antenna device 10 on the vehicle 1 can be improved.

[0051] Furthermore, even if the antenna element on the antenna device 10 side (the signal line side antenna element) is made smaller, gain can be maintained, allowing the antenna device 10 to be made more compact. The antenna element on the antenna device 10 side (the signal line side antenna element) is sufficiently small compared to the wavelength of the radio waves that the dipole antenna 20 supports (e.g., less than one-fourth of the wavelength), thereby ensuring a sufficient distance from, for example, a noise source. Furthermore, the conductor frame 2 of the vehicle 1, which serves as the antenna on the opposite side of the dipole antenna 10, also functions as a ground for 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.

[0052] 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 supports is shorter than the wavelength of radio waves for AM / FM radio, such as the wavelength of radio waves for telephone calls, 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 made as small as one-fourth the wavelength of the radio waves that the dipole antenna 20 supports.

[0053] In the above description, the conductor frame 2 of the vehicle 1 is used as the ground-side antenna element of the dipole antenna 20, but this is not limited to this, and a part of the outer conductor 182 of the coaxial cable 18 may also be used as the ground-side antenna element.

[0054] As shown in FIG. 3 , the outer conductor 182 of the coaxial cable 18 is electrically connected to the intersection 3 between the B-pillar 2B as a first conductor portion extending vertically and the center reinforcement 2E as a second conductor portion extending horizontally. That is, the outer conductor 182 is electrically connected to both the first conductor portion and the second conductor portion. This allows a larger current to flow in the dipole antenna 20, thereby improving gain. Furthermore, the dipole antenna 20 can accommodate both vertically polarized signals and horizontally polarized signals. However, it is sufficient that the outer conductor 182 be electrically connected to at least one of the end of the first conductor portion facing the second conductor portion (hereinafter sometimes referred to as the “first end”) and the end of the second conductor portion facing the first conductor portion (hereinafter sometimes referred to as the “second end”).

[0055] In this embodiment, the dipole antenna 20 is an antenna for linear polarization, which can improve the gain in both the vertical and horizontal components of the linear polarization that the dipole antenna 20 supports. However, the dipole antenna 20 may be an antenna other than that for linear polarization.

[0056] 3, at a point where a first axis X1 extending along the direction in which the B-pillar 2B, which is the first conductor portion, and a second axis X2 extending along the direction in which the center reinforcement 2E, which is the second conductor portion, intersect, the outer conductor 182 is electrically connected to at least one of the first end portion and the second end portion on the side where the interior angle formed by the first axis X1 and the second axis X2 is located. This can further improve gain. However, the outer conductor 182 may also be electrically connected to at least one of the first end portion and the second end portion on a side other than the side where the interior angle formed by the first axis X1 and the second axis X2 is located.

[0057] The electrical connection between the outer conductor 182 of the coaxial cable 18 and the intersection 3 is established, for example, using a connecting wire 4 formed of a conductor, as shown in FIG. 4 . One end of the connecting wire 4 is crimped to join the outer conductor 182 and the connecting wire 4 with a crimping part 4A. A metal fitting 4B is attached to the other end of the connecting wire 4 and fastened to a hole 3A in the intersection 3 with a fastening part 5 such as a bolt. This electrically connects the outer conductor 182 and the intersection 3 via the connecting wire 4. However, the electrical connection between the outer conductor 182 of the coaxial cable 18 and the intersection 3 is not limited to the method shown in FIG. 4 . For example, the other end of the connecting wire 4 may be formed into a film (plane) shape and disposed at the intersection 3, thereby connecting the outer conductor 182 and the intersection 3 by capacitive coupling. Alternatively, the base 11 may have a metal fixing bracket and be directly fastened to the body of the vehicle 1.

[0058] <<Characteristics of Dipole Antenna 20>> Next, the characteristics of the dipole antenna 20 according to this embodiment will be described in comparison with a shark fin antenna.

[0059] Fig. 5 is a diagram showing an example of frequency characteristics of gain in the vertically polarized wave component of the dipole antenna 20. Fig. 6 is a diagram showing an example of frequency characteristics of gain in the horizontally polarized wave component of the dipole antenna 20.

[0060] 5 and 6, the horizontal axis represents frequency, and the vertical axis represents gain. Furthermore, in Fig. 5 and Fig. 6, the results for the dipole antenna 20 of the present embodiment are shown by solid lines, and the results for the comparative antenna (shark fin antenna) are shown by dashed lines. Here, the results are shown for the FM broadcast frequency band of 76 MHz to 108 MHz.

[0061] In both the vertically polarized component shown in Figure 5 and the horizontally polarized component shown in Figure 6, the dipole antenna 20 of this embodiment has better gain results than the antenna of the comparative example. Furthermore, in the antenna of the comparative example, the gain peaks near 85 MHz in both the vertically polarized component and the horizontally polarized component, and drops off at frequencies lower and wider than that. However, in the dipole antenna 20 of this embodiment, in the vertically polarized component shown in Figure 5, the gain increase / decrease is small across the entire FM broadcast frequency band (76 MHz to 108 MHz). Furthermore, in the horizontally polarized component shown in Figure 6, the gain increase / decrease relative to the peak is small compared to the comparative example.

[0062] From the above results, it can be seen that the dipole antenna 20 of this embodiment can achieve higher gain and wider bandwidth than the shark fin antenna of the comparative example. Therefore, in this embodiment, not only can the antenna device 10 be made smaller, but it can also achieve higher gain and wider bandwidth.

[0063] <<Installation Location of Antenna Device 10>> FIG. 7 is a diagram showing an example of average gain for each installation location of the antenna device 10. In FIG.

[0064] 7, 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 in the vehicle 1. As shown in FIG. 7, it can be seen that the dipole antenna 20 can ensure a stable gain regardless of the installation location.

[0065] <<Modification>> FIG. 8 is an explanatory diagram of an antenna device 10A and a dipole antenna 20A according to a modification.

[0066] In the antenna device 10 of the above-described embodiment, elements inside the antenna device 10 (plate-shaped element 13 and helical element 15) are used as elements on one side of the dipole antenna 20, and the conductor frame 2 of the vehicle 1 is used as elements on the other side of the dipole antenna 20.

[0067] As shown in FIG. 8 , some conductor portions (e.g., a portion of the center reinforcement 2E) of the conductor frame 2 of the vehicle 1 may be electrically disconnected from other conductor portions by being connected with a resin member or the like. Hereinafter, the conductor portion of the conductor frame 2 that is not electrically connected to other conductor portions may be referred to as a "floating conductor portion." In this case, this floating conductor portion (a portion of the center reinforcement 2E) can be used as one element of the dipole antenna 20A, rather than an element inside the antenna device 10A. Furthermore, a conductor portion (here, the B-pillar 2B and the side roof 2G) that is electrically connected to other conductor portions and can be used as ground can be used as the other element of the dipole antenna 20A.

[0068] That is, in the dipole antenna 20 of this modified example, the elements on either side of the dipole antenna 20A use the conductor frame 2 of the vehicle 1, and the antenna device 10A can be made even smaller.

[0069] Summary According to the present specification, there is provided an antenna device having the following aspects.

[0070] (Aspect 1) Aspect 1 is an antenna device including a signal line side conductor, a ground side conductor, and an antenna element to which the signal line side conductor is electrically connected, and in which at least the antenna element and a conductor frame of a vehicle to which the ground side conductor is electrically connected form a dipole antenna.

[0071] According to the above-described aspect, it is possible to improve the degree of freedom in the layout of the antenna device in the vehicle.

[0072] (Aspect 2) In aspect 2, the conductor frame has a first conductor portion that is angled with respect to a horizontal plane and a second conductor portion that has an angle with respect to the horizontal plane that 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 a first end of the first conductor portion and a second end of the second conductor portion that is located on the side of the first end.

[0073] According to the above-described aspect, a dipole antenna can be formed using at least one of the vertically extending conductor portion and the horizontally extending conductor portion of the lattice structure formed on the conductor frame of the vehicle, thereby further improving the gain.

[0074] (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.

[0075] According to the above-described aspect, a dipole antenna can be formed using at least one of the vertically extending conductor portion and the horizontally extending conductor portion of the lattice structure formed on the conductor frame of the vehicle, thereby further improving the gain.

[0076] (Aspect 4) In aspect 4, the dipole antenna is an antenna for linearly polarized waves.

[0077] According to the above-described aspect, it is possible to improve the gain in both the vertical component and the horizontal component of the linearly polarized wave.

[0078] According to the present specification, there is provided a dipole antenna having the following configuration.

[0079] (Aspect 5) Aspect 5 is a dipole antenna including a signal line side antenna element to which a signal line side conductor is electrically connected, and a ground side antenna element that is at least a conductor frame of a vehicle and to which a ground side conductor is electrically connected.

[0080] According to the above-described aspect, it is possible to improve the degree of freedom in the layout of the antenna device in the vehicle.

[0081] According to the present specification, a vehicle having the following aspects is provided.

[0082] (Aspect 6) Aspect 6 is a vehicle including 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.

[0083] According to the above-described aspect, it is possible to improve the degree of freedom in the layout of the antenna device in the vehicle.

[0084] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the present invention. Furthermore, the present invention may be modified or improved without departing from the spirit thereof, and the present invention includes equivalents thereof.

[0085] REFERENCE SIGNS LIST 1 vehicle, 2 conductor frame, 10 antenna device, 20 dipole antenna, 31 signal line side conductor, 32 ground side conductor

Claims

1. 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 a conductor frame of a vehicle to which the ground side conductor is electrically connected form a dipole antenna.

2. The antenna device described in claim 1, wherein the conductor frame has a first conductor portion that is angled with respect to a 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 a first end of the first conductor portion and a second end of the second conductor portion that is located on the side of the first end.

3. The antenna device described in claim 2, wherein 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.

4. The antenna device according to claim 2 or 3, wherein the dipole antenna is an antenna for linear polarization.

5. 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 that is at least a conductor frame of a vehicle and to which a ground side conductor is electrically connected.

6. A vehicle comprising 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.

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