Antenna device

Abstract

An antenna device, which is provided in a vehicle and is capable of receiving radio waves of a predetermined frequency band, is provided with a power supply electrode electrically connected to a signal line of a transmission line, an antenna element electrically connected to the power supply electrode, and a ground conductor including a ground electrode electrically connected to a ground line of the transmission line, the reactance between the ground conductor and the metal vehicle body of the vehicle is-50 Omega or more and + 50 Omega or less in the frequency band, and the antenna device does not have a linear ground element extending from the ground electrode.

Description

Technical Field

[0001] The present invention relates to an antenna device. Background Art

[0002] There has been conventionally known a windshield provided with a glass antenna element, wherein the glass antenna element has a core wire side antenna element and a ground side antenna element (see, for example, Patent Document 1). Prior Art Documents Patent Documents

[0003] Patent Document 1: WO 2019 / 198561 Summary of the Invention Technical Problem to be Solved by the Invention

[0004] However, it has been difficult for the prior art to simplify the antenna element while ensuring the antenna gain.

[0005] The present disclosure provides an antenna device capable of ensuring the antenna gain with a simple antenna element. Means for Solving the Technical Problem

[0006] According to one aspect of the present disclosure, there is provided an antenna device provided on a vehicle and capable of receiving radio waves in a specified frequency band. The antenna device includes: a power supply electrode electrically connected to a signal line of a transmission line; an antenna element electrically connected to the power supply electrode; and a ground conductor including a ground electrode electrically connected to a ground wire of the transmission line. The reactance between the ground conductor and the metal body of the vehicle is -50 Ω or more and +50 Ω or less within the frequency band. The antenna device does not have a linear ground element extending from one end connected to the ground electrode to the other end not connected to other conductors. Advantageous Effects of the Invention

[0007] According to one aspect of the present invention, it is possible to provide a vehicle window glass capable of ensuring the antenna gain. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 FIG. schematically shows a structural example of an antenna device according to an embodiment from a top view perspective of a window glass. Figure 2 FIG. is a top view showing an example of a connection method of a coaxial cable and an antenna. Figure 3 FIG. is a partial top view of a structural example of the antenna device according to the first embodiment. Figure 4It is a partial cross-sectional view of a structural example of the antenna device of the first embodiment. Figure 5 It is a top view showing a first modified example of the antenna device of the first embodiment. Figure 6 It is a top view showing a second modified example of the antenna device of the first embodiment. Figure 7 It is a partial top view of a structural example of the antenna device of the second embodiment. Figure 8 It is a partial cross-sectional view of a structural example of the antenna device of the second embodiment. Figure 9 It is within the DAB BandIII frequency band for Figure 3 A diagram showing the result of simulating the relationship between the element length Ha shown and the maximum element length L. Figure 10 It is within the frequency band of terrestrial digital television broadcast waves for Figure 3 A diagram showing the result of simulating the relationship between the element length Ha shown and the maximum element length L. Figure 11 It is within the frequency band of FM broadcast waves for Figure 3 A diagram showing the result of simulating the relationship between the element length Ha shown and the maximum element length L. Detailed Embodiments

[0009] Hereinafter, the embodiments will be described with reference to the drawings. For ease of understanding, the scales of the respective parts in the drawings are sometimes different from the actual ones. Terms such as parallel, right angle, orthogonal, horizontal, vertical, up and down, left and right, etc., allow deviations to the extent that the functions and effects of the embodiments are not impaired. The shape of the corners is not limited to right angles and may be arcuate with rounded corners. By overlapping, it may include the meaning of partial overlap. By relative, it may include the meaning of partial relativity. The X-axis direction, Y-axis direction, and Z-axis direction respectively represent directions parallel to the X-axis, Y-axis, and Z-axis. The X-axis direction, Y-axis direction, and Z-axis direction are mutually orthogonal. The XY plane, YZ plane, and ZX plane respectively represent imaginary planes parallel to the X-axis direction and Y-axis direction, imaginary planes parallel to the Y-axis direction and Z-axis direction, and imaginary planes parallel to the Z-axis direction and X-axis direction.

[0010] Examples of vehicle window glasses to which this embodiment is applied include rear window glasses installed at the rear of the vehicle, windshield glasses installed at the front of the vehicle, side window glasses installed on the sides of the vehicle, sunroof glasses installed on the top of the vehicle, etc. The vehicle window glass is not limited to these examples. For example, it may also be a window glass in which the sunroof glass is integrated with one or both of the windshield glass or the rear window glass.

[0011] Figure 1 This is a diagram schematically showing a structural example of an antenna device according to an embodiment from a top-down perspective of a window glass. Figure 1 The illustrated antenna device 100 is an example of a vehicle-mounted antenna device provided on a vehicle. In the illustrated example, it is provided on a vehicle window glass 1. The antenna device 100 has an antenna 10 capable of receiving radio waves in a specified frequency band F. The antenna device 100 is a vehicle-mounted antenna device capable of receiving radio waves in the specified frequency band F through the antenna 10.

[0012] Among them, the antenna 10 can be an antenna capable of transmitting and receiving radio waves in the specified frequency band F. Transceiving means both transmitting and receiving. In addition, receiving (or transceiving) radio waves in the frequency band F can be receiving (or transceiving) radio waves in a part of the frequency band F or receiving (or transceiving) all frequency bands of the frequency band F.

[0013] The frequency band F is, for example, a UHF (Ultra High Frequency) band with a frequency of 300 MHz to 3 GHz, a VHF (Very High Frequency) band with a frequency of 30 MHz to 300 MHz, or a frequency band spanning these two bands. As a specific example of the frequency band included in the UHF band, there is a frequency band of terrestrial digital television broadcast waves (for example, 470 MHz to 710 MHz), etc. As a specific example of the frequency band included in the VHF band, there are frequency bands of FM broadcast waves (for example, 76 MHz to 108 MHz), DAB Band III (for example, 170 MHz to 240 MHz), etc.

[0014] The window glass 1 is an example of a dielectric plate mounted on a vehicle. More specifically, it is an example of a glass plate mounted on a vehicle. The antenna device 100 or the antenna 10 can be provided on or near the window glass 1, or can be provided on or near a dielectric plate different from the window glass 1.

[0015] The part on or near the dielectric plate provided with the antenna device 100 or the antenna 10 is not limited to the window glass 1 as shown in the figure, and can also be a resin body, a spoiler, a bumper, etc.

[0016] The antenna device 100 or the antenna 10 can be provided on the surface of the window glass 1 (for example, the inner surface of the vehicle). In addition, the antenna device 100 or the antenna 10 can also be provided in a manner of being enclosed in the window glass 1, where the window glass 1 is a laminated glass formed by sandwiching a resin layer between two glass plates.

[0017] The vicinity of the window glass 1 provided with the antenna device 100 or the antenna 10 includes, for example, the interior of the vehicle within a distance of 100 mm or less from the surface of the window glass 1. The vicinity of the window glass 1 is not limited to the interior of the vehicle and may also include the exterior of the vehicle within a distance of 100 mm or less from the surface of the window glass 1. As a specific example of the vicinity of the window glass 1, for example, vehicle-side parts such as the roof, the center console, the pillars, the trim pieces, and the vehicle mirrors that are at a certain distance from the window glass 1 can be cited. The antenna device 100 or the antenna 10 can be arranged in such a way that the antenna 10 is mounted on the window glass 1 or on a component near it.

[0018] The antenna device 100 or the antenna 10 can be configured to overlap partially or entirely with a part of the light-shielding film 5 formed by the peripheral edge of the window glass 1 when viewed from above the window glass 1, or to overlap partially or entirely on the light-shielding film 5. As a specific example of the light-shielding film 5, ceramics such as a black ceramic film can be cited. When observing the window glass 1 from the outside of the vehicle, the part provided on the glass edge side closer to the glass than the inner edge 5a of the light-shielding film 5 is not easily visible from the outside of the vehicle, thus improving the design of the window glass.

[0019] The antenna device 100 or the antenna 10 is not limited to the arrangement shown in the figure along the upper glass edge 1a of the window glass 1 (in other words, the upper end edge of the unillustrated window frame on which the window glass 1 is mounted). For example, the antenna 10 can also be arranged along any one of the lower glass edge 1b of the window glass 1 (the lower end edge of the window frame), the left glass edge 1c of the window glass 1 (the left end edge of the window frame), and the right glass edge 1d of the window glass 1 (the right end edge of the window frame).

[0020] The antenna device 100 has a ground conductor 18 for grounding the antenna 10. The antenna 10 has a power supply electrode 16, an antenna element 13, and a ground electrode 17. The ground electrode 17 is a part included in the ground conductor 18.

[0021] The positional relationship and shape of the power supply electrode 16, the antenna element 13, and the ground electrode 17 are not limited to Figure 1 the example. For example, the positional relationship between the power supply electrode 16 and the ground electrode 17 can be the opposite of Figure 1 the example. In addition, the direction in which the antenna element 13 extends can also be a direction different from Figure 1 the example. Furthermore, the shapes of the power supply electrode 16 and the ground electrode 17 are not limited to rectangles and can be other shapes such as circles.

[0022] The power supply electrode 16 is electrically connected to the signal line 51 of a transmission line 50 such as a coaxial cable. The antenna element 13 is electrically connected to the power supply electrode 16. The ground conductor 18 includes the ground electrode 17. In Figure 1In the example of , the linear ground element is not connected to the ground electrode 17. The ground electrode 17 is electrically connected to the ground line 52 of the transmission line 50 (for example, the external conductor (Japanese: external conductor) of the coaxial cable).

[0023] Figure 2 1 is a top view showing an example of a connection method of the coaxial cable 53 and the antenna 10. The coaxial cable 53 is an example of a transmission line. In the antenna device 100, the connector 40 for connecting the coaxial cable 53 and the antenna 10 can be installed on the power supply electrode 16 and the ground electrode 17. In this case, the signal line of the coaxial cable 53 is electrically connected to the power supply electrode 16 through the connector 40, and the external wire of the coaxial cable 53 is electrically connected to the ground electrode 17 through the connector 40.

[0024] Furthermore, the antenna device 100 may include an amplifier 41 mounted on the window glass 1 or a dielectric plate such as a dielectric layer 19 described later. The amplifier 41 may be a component integrated with the connector 40 or a component separate from the connector 40. Figure 2 The example shows that the amplifier 41 is an integral component built into the connector 40. The input terminal 42 of the amplifier 41 may be electrically connected to the power supply electrode 16, the ground terminal 43 of the amplifier 41 may be electrically connected to the ground electrode 17, and the output terminal 44 of the amplifier 41 may be electrically connected to the signal line of the coaxial cable 53. In addition, a DC blocking capacitor may be interposed between the internal ground of the amplifier 41 and the ground terminal 43.

[0025] Figure 3 It is a partial plan view of a configuration example of the antenna device according to the first embodiment. Figure 4 1 is a partial cross-sectional view of a configuration example of the antenna device according to Embodiment 1. Antenna device 101 is a configuration example of the antenna device 100 described above. Figure 3 and Figure 4 In the figure, when the window glass 1 is mounted on the flange 66 formed on the vehicle body 62, the positive side in the Z-axis direction represents the vehicle interior, and the negative side in the Z-axis direction represents the vehicle exterior. The vehicle body 62 is an example of a metal vehicle body. The flange 66 is a metal portion facing the metal vehicle body, and is also called a window frame.

[0026] Figure 4In the embodiment, the window glass 1 has a main surface 2 (an example of a first main surface) facing the negative side in the Z-axis direction and a main surface 3 (an example of a second main surface facing the side opposite to the first main surface) facing the positive side in the Z-axis direction. The window glass 1 is mounted on the flange 66 by bonding the peripheral portion of the main surface 3 to the flange 66 with an adhesive 65 such as a polyurethane resin, for example. The flange 66 has a metal portion 63 that is opposite to at least a portion of the peripheral portion of the main surface 3 when the window glass 1 is viewed from the Z-axis direction. The inner edge 64 of the metal portion 63 forms an opening covered by the window glass 1 when the window glass 1 is viewed from the Z-axis direction. The window glass 1 is an example of a glass plate for a vehicle, and is a plate-like body having a dielectric such as glass as a main component.

[0027] Figure 3 and Figure 4 In the embodiment, the antenna element 13 , the power supply electrode 16 , the ground electrode 17 and the extension conductor 31 are arranged on the same plane, and in this example, they are formed on the main surface 3 of the window glass 1 . Figure 3 The antenna element 13 shown is an L-shaped linear conductor, but is not limited to the L-shape. The antenna element 13 may be T-shaped, loop-shaped, or any other shape including a fold or branch and having one or more open ends. In addition, the T-shape may be considered to include an L-shape. Furthermore, the antenna element 13 may be a (pattern) shape in which a plurality of linear conductors extend from the power supply electrode 16 in any direction. Figure 3 In the example of FIG. 1 , the antenna element 13 has a line extending from the power supply electrode 16 and is a line having a single open end 13 a.

[0028] The power supply electrode 16 is a square planar conductor. The ground conductor 18 includes a ground electrode 17 and an extension conductor 31. The ground electrode 17 is a square planar conductor. The extension conductor 31 is a linear or planar conductor extending from the ground electrode 17. In this example, the extension conductor 31 is an L-shaped conductor, which includes a conductor portion 31a extending from the ground electrode 17 to the positive side in the Y-axis direction and a conductor portion 31b connected to the conductor portion 31a. The extension conductor 31 may also be in other shapes such as a T-shape. The conductor portion 31b extends in the X-axis direction along the inner edge 64 of the metal portion 63.

[0029] When the window glass 1 is mounted on the flange 66, at least a portion of the ground conductor 18 (the conductor portion 31b in this example) overlaps the metal portion 63 when viewed from above the window glass 1. Figure 4 As shown in FIG. 6 , the adhesive 65 is a dielectric layer interposed between the extension conductor 31 and the metal portion 63. Figure 4In the example, the adhesive 65 is interposed between the conductor portion 31b of the extended conductor 31 and the mounting surface of the metal portion 63, and the capacitive coupling between the conductor portion 31b and the metal portion 63 is formed by the adhesive 65. In addition, a dielectric layer different from the adhesive 65 may be included between the extended conductor 31 and the metal portion 63. Further, the conductor portion 31b of the extended conductor 31 may not be electrically connected to the metal portion 63 by the adhesive 65. In this case, the reactance between the ground conductor 18 and the metal portion 63 is substantially zero.

[0030] Here, the reactance between the ground conductor 18 and the metal portion 63 is defined as the reactance Xr. In this example, the reactance Xr may also be defined as the reactance between the extended conductor 31 included in the ground conductor 18 and the mounting surface of the metal portion 63.

[0031] When the reactance Xr is -50 Ω or more and +50 Ω or less within the frequency band F, the ground electrode 17 included in the ground conductor 18 is stably grounded to the metal portion 63. Thus, even if the external wire length Lg of the coaxial cable 53 from the ground electrode 17 to the intermediate ground point 54 (see Figure 2 ) changes, the decrease in the antenna gain of the antenna 10 can be suppressed. As a result, the antenna gain of the antenna device 101 is ensured. From the viewpoint of suppressing the decrease in the antenna gain, the reactance Xr is preferably -40 Ω or more and +40 Ω or less within the frequency band F, and more preferably -30 Ω or more and +30 Ω or less.

[0032] Figure 2 In, the intermediate ground point 54 is a portion where the external wire of the coaxial cable 53 is grounded to the metal body 62 at the intermediate position of the coaxial cable 53. The external wire length Lg of the coaxial cable 53 from the ground electrode 17 to the intermediate ground point 54 varies according to vehicle specifications and deviations between vehicles. When the length Lg changes, the resonance length of the antenna 10 may also change. However, in the present embodiment, since the ground electrode 17 is stably grounded to the metal portion 63, the influence on the resonance of the antenna 10 is reduced. Therefore, even if the length Lg changes, the decrease in the antenna gain of the antenna 10 can be suppressed. Among them, the intermediate ground point 54 may be omitted.

[0033] The antenna device 100 may include an inductor 45 connected in series with the antenna element 13 and having one end electrically connected to the power supply electrode 16. By providing the inductor 45, the antenna device 100 can miniaturize the antenna 10. The inductor 45 may be serially inserted into the intermediate portion of the antenna element 13, may be serially inserted between the antenna element 13 and the power supply electrode 16, may be serially inserted between the power supply electrode 16 and the input terminal 42 of the amplifier 41, or may be serially inserted into the input portion on the substrate on which the amplifier 41 is mounted. The inductor 45 is, for example, a coil element.

[0034] In addition, when the reactance Xr is -50 Ω or more and +50 Ω or less within the frequency band F, the ground electrode 17 is stably grounded to the metal part 63. Therefore, the antenna device 101 may not have a linear ground element that extends from one end connected to the ground electrode 17 to the other end not connected to other conductors. Since the ground electrode 17 is stably grounded to the metal part 63, the potential of the ground electrode 17 is close to the potential of the metal part 63. Therefore, common-mode noise via the ground electrode 17 can be suppressed. As a result, a decrease in the antenna gain of the antenna 10 is suppressed. Therefore, when the reactance Xr of the antenna device 101 within the frequency band F is -50 Ω or more and +50 Ω or less, it does not have a linear ground element that extends from one end connected to the ground electrode 17 to the other end not connected to other conductors. Therefore, the antenna gain can be ensured with a simple antenna element.

[0035] In addition, the so-called linear ground element that extends from one end connected to the ground electrode 17 to the other end not connected to other conductors refers to an element that extends from the ground electrode 17 and whose extended front end is not connected to other conductors. Figure 3 The shown extended conductor 31 is not a linear ground element that extends from one end connected to the ground electrode 17 to the other end not connected to other conductors because the conductor part 31b at its front end is electrically connected to the metal part 63 of the conductor. In addition, in the case where a linear element is defined as an element having a line width thicker than that of the antenna element 13, Figure 3 the shown extended conductor 31 has a line width thicker than that of the antenna element 13. Therefore, it does not correspond to a linear ground element extending from the ground electrode 17.

[0036] Figure 4 When the equivalent series resistance (ESR) between the ground conductor 18 and the metal part 63 is 5 Ω or less, the ground electrode 17 included in the ground conductor 18 is stably grounded to the metal part 63. Therefore, the antenna gain can be ensured. From the perspective of ensuring the antenna gain, the ESR is preferably 4 Ω or less, more preferably 3 Ω or less, and further preferably 2 Ω or less. From the perspective of ensuring the antenna gain, the ESR can be zero.

[0037] If the reactance Xr between the ground conductor 18 and the metal part 63 is -50 Ω or more and +50 Ω or less within the frequency band F, the surface (mounting surface) of the metal part 63 can be covered with the coating material 67 serving as an insulating layer. If the reactance Xr is -50 Ω or more and +50 Ω or less within the frequency band F, the ground conductor 18 (more specifically, at least one of the ground electrode 17 and the extended conductor 31) can be covered with an insulating layer.

[0038] Figure 3 In this case, the antenna element 13 is provided on the main surface 3 of the window glass 1. However, the antenna element 13 can also be like Figure 1It is disposed on the main surface 19a of the dielectric layer 19 provided on the main surface 3 of the window glass 1. The dielectric layer 19 can be a dielectric substrate mainly composed of a dielectric, such as a printed substrate or a flexible substrate. The antenna element 13, the power supply electrode 16, and the ground electrode 17 can be disposed on the main surface 19a (the same plane) of the dielectric layer 19.

[0039] Figure 3 The antenna element 13 shown is an L-shaped element disposed on the main surface 3 of the window glass 1. The antenna element 13 extends from the power supply electrode 16 in a first direction (the negative Y-axis direction in this example) away from the metal portion 63, and then bends at the bending point 13b and extends along the inner edge 64 of the metal portion 63 in a second direction (the positive X-axis direction in this example) to the open end 13a. The antenna element 13 includes a first element 11 that extends from the power supply electrode 16 in the first direction and bends at the bending point 13b, and a second element 12 that extends from the bending point 13b to the open end 13a.

[0040] Figure 3 In this case, the element length of the first element 11 is set as Ha, and the maximum element length from the power supply electrode 16 to the open end 13a of the antenna element 13 is set as L. Also, the wavelength shortening rate caused by the dielectric plate (such as the window glass 1 or the dielectric layer 19) is set as k, and the wavelength of the radio wave in the air at the center frequency of the frequency band F is set as λ.

[0041] For example, in the case of the frequency band of DAB BandIII with the frequency band F being 170 MHz to 240 MHz, when the antenna device 101 satisfies 0.0036×k×λ≤Ha≤0.28×k×λ...... Equation 1a 0.062×k×λ≤L≤0.28×k×λ...... Equation 2a the decrease in the antenna gain within DAB BandIII is suppressed.

[0042] From the perspective of suppressing the decrease in the antenna gain within DAB BandIII, it is preferable that 0.0100×k×λ≤Ha≤0.27×k×λ...... Equation 1b 0.070×k×λ≤L≤0.27×k×λ...... Equation 2b, more preferably 0.0200×k×λ≤Ha≤0.25×k×λ...... Equation 1c 0.080×k×λ≤L≤0.25×k×λ...... Equation 2c.

[0043] For example, in the case of the frequency band F of the terrestrial digital television broadcast wave being in the frequency band of 470 MHz to 710 MHz, the antenna device 101 satisfies 0.00505×k×λ ≤ Ha ≤ 0.28×k×λ... Equation 3a 0.0717×k×λ ≤ L ≤ 0.28×k×λ... Equation 4a the decrease in the antenna gain within the frequency band of the terrestrial digital television broadcast wave is suppressed.

[0044] From the perspective of suppressing the decrease in the antenna gain within the frequency band of the terrestrial digital television broadcast wave, it is preferable that 0.01000×k×λ ≤ Ha ≤ 0.27×k×λ... Equation 3b 0.0800×k×λ ≤ L ≤ 0.27×k×λ... Equation 4b, more preferably 0.02000×k×λ ≤ Ha ≤ 0.25×k×λ... Equation 3c 0.0900×k×λ ≤ L ≤ 0.25×k×λ Equation... 4c.

[0045] For example, in the case of the frequency band F of the FM broadcast wave being in the frequency band of 76 MHz to 108 MHz, when the antenna device 101 satisfies 0.00373×k×λ ≤ Ha ≤ 0.28×k×λ... Equation 5a 0.063×k×λ ≤ L ≤ 0.28×k×λ... Equation 6a the decrease in the antenna gain within the frequency band of the FM broadcast wave is suppressed.

[0046] From the perspective of suppressing the decrease in the antenna gain within the frequency band of the FM broadcast wave, it is preferable that 0.01000×k×λ ≤ Ha ≤ 0.27×k×λ... Equation 5b 0.0700×k×λ ≤ L ≤ 0.27×k×λ... Equation 6b, more preferably 0.02000×k×λ ≤ Ha ≤ 0.25×k×λ... Equation 5c 0.0800×k×λ ≤ L ≤ 0.25×k×λ... Equation 6c.

[0047] Figure 5 is a top view showing a first modification of the antenna device of the first embodiment. As Figure 5As shown, the antenna 10 may further include a short - circuit element 14 that extends from one end connected to the ground electrode 17 to the other end connected to another conductor (antenna element 13). By adding the short - circuit element 14, impedance matching can be achieved, and the antenna 10 can function as an inverted - F antenna. The front end of the short - circuit element 14 is connected to the second element 12 of the antenna element 13, so it does not belong to the linear ground element that extends from the end connected to the ground electrode 17 to the end not connected to other conductors.

[0048] Figure 6 is a top view showing a second modification of the antenna device according to the first embodiment. As Figure 6 shown, the extending conductor 31 may include a plurality of conductor portions that extend from one end connected to the ground electrode 17 to the other end electrically connected to another conductor (metal portion 63). Since the plurality of conductor portions have front ends electrically connected to the metal portion 63, they do not belong to the linear ground element that extends from the end connected to the ground electrode 17 to the end not connected to other conductors. The plurality of conductor portions may be electrically connected to the metal portion 63 via a conductive member 20 described later. As long as the electrical connection between the ground electrode 17 and the metal portion 63 is not damaged, the shape of the extending conductor 31 can be any shape. For example, the shape of the extending conductor 31 can be annular or mesh - shaped.

[0049] Figure 7 is a partial top view of a structural example of the antenna device according to the second embodiment. Figure 8 is a partial cross - sectional view of a structural example of the antenna device according to the second embodiment. In the second embodiment, the description of the same structures, functions, and effects as those in the first embodiment is omitted by reference to the above description. The antenna device 102 is a structural example of the above - mentioned antenna device 100. The difference between the second embodiment and the first embodiment is that the ground conductor 18 includes a three - dimensional conductive member 20 that is in electrical contact with the metal body of the vehicle.

[0050] Figure 7 and Figure 8 shown, the ground conductor 18 includes a three - dimensional conductive member 20 that is in electrical contact with the metal portion 63. By making the ground conductor 18 include the conductive member 20, the ground electrode 17 included in the ground conductor 18 is stably grounded to the metal portion 63. As a result, a decrease in the antenna gain of the antenna 10 caused by a change in the external wire length Lg of the coaxial cable 53 from the ground electrode 17 to the intermediate ground point 54 (see Figure 2 ), or a decrease in the antenna gain caused by the presence or absence of the intermediate ground point 54 can be further suppressed. As a result, the antenna gain of the antenna device 102 can be further ensured.

[0051] Figure 7 and Figure 8In this case, the conductive member 20 is interposed between the extending conductor 31 on the main surface 3 and the mounting surface of the metal part 63, and electrically connects the ground electrode 17 and the metal part 63. The conductive member 20 is in contact with the conductor portion 31b. In this case, the conductor portion 31a (see Figure 7 ) is a connecting conductor that connects the ground electrode 17 and the conductive member 20. In addition, the conductive member 20 may also be in contact with the conductor portion 31a.

[0052] Figure 8 In this case, when the conductive member 20 includes the elastomer 21, it deforms along the unevenness of the mounting surface of the metal part 63. Therefore, even if there are unevenness on the mounting surface of the metal part 63, by making the conductive member 20 elastic (including the elastomer 21), the ground electrode 17 included in the ground conductor 18 is stably grounded to the metal part 63.

[0053] The elastomer 21 included in the conductive member 20 may include, for example, a rod-shaped spacer. The spacer may be a member in which a conductive coating film 22 is coated on the outer surface of the insulating elastomer 21. The spacer uses, for example, a barrier spacer. Thus, if the elastomer 21 including the barrier spacer is fixed in a state of elastically contacting so as to fill the space between the ground electrode 17 and the metal part 63, sometimes the need for fasteners such as screws for grounding the ground electrode 17 can be eliminated. Furthermore, if the elastomer 21 can be fixed in a state of elastically contacting so as to fill the space between the ground electrode 17 and the metal part 63, the assembly will become easy.

[0054] Figure 7 In this case, the conductive member 20 may include a proximity region 23 that is in proximity to the metal part 63 at a distance of 1 mm or less when viewed from the thickness direction of the metal part 63 (the Z-axis direction in this example). Let the area of the proximity region 23 be S [mm 2 , and let the frequency included in the frequency band F be f [MHz]. At this time, when the antenna device 102 satisfies 9.59×10 3 / f ≤ S ≤ 3.24×10 5 / f... Equation 7a the decrease in the antenna gain within the frequency band F is suppressed.

[0055] In addition, from the perspective of suppressing the decrease in the antenna gain within the frequency band F, it is preferable that 1.50×10 4 / f ≤ S ≤ 3.00×10 5 / f... Equation 7b, more preferably 2.00×10 4 / f ≤ S ≤ 2.80×10 5 / f... Equation 7c.

[0056] Next, simulation results of the antenna device according to the present embodiment will be described.

[0057] Figure 9 In the case of DAB Band III, the frequency band F is 170MHz to 240MHz. Figure 3 1 and 2. The relationship between the element length Ha and the maximum element length L is simulated in a graph. The dotted line A represents the case where the antenna element 13 has only the first element 11 and no second element 12. When the relationship between the element length Ha and the maximum element length L is within the range above the dotted line A and the curve B1, the antenna gain drop of the bandwidth 70 MHz of DAB Band III is suppressed to within 10 dB relative to the maximum antenna gain within the bandwidth 70 MHz. This result satisfies the above-mentioned equations 1a and 2a.

[0058] Figure 10 In the case of a terrestrial digital television broadcast wave with a frequency band F of 470 MHz to 710 MHz, Figure 3 1 and 2 are graphs showing the results of simulations of the relationship between the element length Ha and the maximum element length L shown in FIG. The dotted line A represents the case where the antenna element 13 has only the first element 11 and does not have the second element 12. When the relationship between the element length Ha and the maximum element length L is within the range above the dotted line A and the curve B2, the result is obtained that the antenna gain drop within the bandwidth of 240 MHz of the terrestrial digital TV broadcast wave is suppressed to within 10 dB relative to the maximum antenna gain within the bandwidth of 240 MHz. This result satisfies the above-mentioned equations 3a and 4a.

[0059] Figure 11 In the case of the FM broadcast wave frequency band F of 76MHz to 108MHz, Figure 3 1 and 2 are graphs showing the results of simulations of the relationship between the element length Ha and the maximum element length L shown in FIG. The dotted line A represents the case where the antenna element 13 has only the first element 11 and does not have the second element 12. When the relationship between the element length Ha and the maximum element length L is within the range above the dotted line A and the curve B3, the result is obtained that the antenna gain drop within the bandwidth of 32 MHz of the FM broadcast wave is suppressed to within 10 dB relative to the maximum antenna gain within the bandwidth of 32 MHz. This result satisfies the above-mentioned equations 5a and 6a.

[0060] As described above, the embodiments have been described, but the above embodiments are presented only as examples, and the present invention is not limited to the above embodiments. The above embodiments can be implemented in various other ways, and various combinations, omissions, substitutions, changes, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope or gist of the invention and are included in the invention described in the claims and its equivalents.

[0061] This international application claims priority based on Japanese Patent Application No. 2022-192787 filed on December 1, 2022, and incorporates the entire contents of Japanese Patent Application No. 2022-192787 into this international application.

[0062] Regarding the above embodiments, the following additional notes are further disclosed. (Supplementary Note 1) An antenna device that is an antenna device provided on a vehicle and capable of receiving radio waves in a specified frequency band. It has: a power supply electrode electrically connected to the signal line of the transmission line, an antenna element electrically connected to the power supply electrode, and a ground conductor, and the ground conductor includes a ground electrode electrically connected to the ground line of the transmission line. The reactance between the ground conductor and the metal body of the vehicle is -50 Ω or more and +50 Ω or less within the frequency band. The antenna device does not have a linear ground element that extends from one end connected to the ground electrode to the other end not connected to other conductors. (Supplementary Note 2) The antenna device according to Supplementary Note 1, wherein the equivalent series resistance between the ground conductor and the metal body is 5 Ω or less. (Supplementary Note 3) The antenna device according to Supplementary Note 1 or Supplementary Note 2, wherein the antenna element has a single line extending from the power supply electrode. (Supplementary Note 4) The antenna device according to any one of Supplementary Notes 1 to 3, wherein the antenna element has one or more open ends. (Supplementary Note 5) The antenna device according to Supplementary Note 4, wherein the antenna element is a single line having a single open end. (Supplementary Note 6) The antenna device according to any one of Supplementary Notes 1 to 5, wherein the antenna element includes an L-shaped element provided on a dielectric plate. The L-shaped element extends in a first direction away from the metal body starting from the power supply electrode and then bends in a second direction. (Supplementary Note 7) The antenna device according to Note 6, wherein the L-shaped element includes a first element that extends and bends from the power supply electrode in the first direction, When the element length of the first element is set as Ha, the maximum element length from the power supply electrode to the open end of the antenna element is set as L, the wavelength shortening rate caused by the dielectric plate is set as k, and the wavelength of the radio wave in the air at the center frequency of the frequency band is set as λ, the following is satisfied: 0.0036×k×λ ≤ Ha ≤ 0.28×k×λ, 0.062×k×λ ≤ L ≤ 0.28×k×λ. (Note 8) The antenna device according to Note 6 or Note 7, wherein the power supply electrode, the antenna element, and the ground electrode are provided on the same plane of the dielectric plate. (Note 9) The antenna device according to any one of Notes 6 to 8, wherein the dielectric plate includes the glass plate of the vehicle. (Note 10) The antenna device according to Note 9, wherein the dielectric plate includes the glass plate and a dielectric layer having a main surface on which the antenna element is formed. (Note 11) The antenna device according to Note 9 or Note 10, wherein the metal body is a flange opposite to the glass plate. (Note 12) The antenna device according to any one of Notes 1 to 11, wherein the surface of the metal body is covered with a coating material that serves as an insulating layer. (Note 13) The antenna device according to any one of Notes 1 to 12, wherein the ground conductor includes a three-dimensional conductive member that is in electrical contact with the metal body. (Note 14) The antenna device according to Note 13, wherein the conductive member includes a proximity region that is in proximity to the metal body at a distance of 1 mm or less when viewed in the thickness direction of the metal body, When the area of the proximity region is set as S [mm 2 , and the frequency included in the frequency band is set as f [MHz], the following is satisfied: 9.59×10 3 / f ≤ S ≤ 3.24×10 5 / f. (Note 15) The antenna device according to Note 13 or 14, wherein the ground conductor includes a connection conductor connecting the ground electrode and the conductive member. (Note 16) The antenna device according to any one of Notes 13 to 15, wherein the conductive member includes an elastomer. (Note 17) The antenna device according to Note 16, wherein the elastomer includes a rod-shaped spacer. (Note 18) The antenna device according to Note 17, wherein the spacer is coated with a conductive film on the outer surface of the elastomer. (Note 19) The antenna device according to any one of Notes 13 to 18, wherein the metal body includes a flange facing the vehicle glass plate, The conductive member is interposed between the glass plate and the flange. (Note 20) The antenna device according to any one of Notes 1 to 19, wherein it includes an inductor connected in series with the antenna element and having one end electrically connected to the power supply electrode. (Note 21) The antenna device according to any one of Notes 1 to 20, wherein the frequency band is at least one of the frequency bands of FM broadcast waves, DAB BandIII, and terrestrial digital television broadcast waves. (Note 22) The antenna device according to any one of Notes 1 to 21, wherein the ground wire is grounded to the metal body. Symbol Explanation

[0063] 1 Window glass 1a - 1d Glass edge 2, 3 Main surface 10 Antenna 11 First element 12 Second element 13 Antenna element 14 Short - circuit element 16 Power supply electrode 17 Ground electrode 18 Ground conductor 19 Dielectric layer 20 Conductive member 21 Elastomer 22 Conductive film 23 Proximity area 31 Extension conductor Conductor parts 31a, 31b Connector 40 Amplifier 41 Input terminal 42 Ground terminal 43 Output terminal 44 Inductor 45 Transmission line 50 Signal line 51 Ground wire 52 Coaxial cable 53 Intermediate ground point 54 Vehicle body 62 Metal part 63 Inner edge 64 Adhesive 65 Flange 66 Coating material 67 Antenna devices 100, 101, 102.

Claims

1. An antenna device, which is an antenna device provided on a vehicle and capable of receiving radio waves in a specified frequency band, comprising: a power supply electrode electrically connected to the signal line of the transmission line, an antenna element electrically connected to the power supply electrode, and a ground conductor, the ground conductor including a ground electrode electrically connected to the ground wire of the transmission line, wherein the reactance between the ground conductor and the metal body of the vehicle is -50 Ω or more and +50 Ω or less within the frequency band, and the antenna device does not have a linear ground element extending from one end connected to the ground electrode to the other end not connected to other conductors.

2. The antenna device according to claim 1, wherein, The equivalent series resistance between the ground conductor and the metal body is 5 Ω or less.

3. The antenna device according to claim 1, wherein, The antenna element has a single line extending from the power supply electrode.

4. The antenna device according to any one of claims 1 to 3, wherein, The antenna element has one or more open ends.

5. The antenna device according to claim 4, wherein, The antenna element is a single line with a single open end.

6. The antenna device according to any one of claims 1 to 3, wherein The antenna element includes an L-shaped element provided on a dielectric plate, and the L-shaped element extends from the power supply electrode in a first direction away from the metal body and then bends in a second direction.

7. The antenna device according to claim 6, wherein, The L-shaped element includes a first element extending from the power supply electrode in the first direction and then bending, when the element length of the first element is set as Ha, the maximum element length from the power supply electrode to the open end of the antenna element is set as L, the wavelength shortening rate caused by the dielectric plate is set as k, and the wavelength of the radio wave in the air at the center frequency of the frequency band is set as λ, the following are satisfied: 0.0036×k×λ ≤ Ha ≤ 0.28×k×λ, 0.062×k×λ ≤ L ≤ 0.28×k×λ.

8. The antenna device according to claim 7, wherein, The power supply electrode, the antenna element, and the ground electrode are provided on the same plane of the dielectric plate.

9. The antenna device according to claim 6, wherein, The dielectric plate includes the glass plate of the vehicle.

10. The antenna device according to claim 9, wherein, The dielectric plate includes the glass plate and a dielectric layer having a main surface on which the antenna element is formed.

11. The antenna device according to claim 9, wherein, The metal body is a flange opposite to the glass plate.

12. The antenna device according to any one of claims 1 to 3, wherein, The surface of the metal body is covered with a coating material serving as an insulating layer.

13. The antenna device according to any one of claims 1 to 3, wherein, The ground conductor includes a three-dimensional conductive member in electrical contact with the metal body.

14. The antenna device according to claim 13, wherein, The conductive member includes a close-proximity region, which is a portion that is in close proximity to the metal body at a distance of 1 mm or less when viewed in the thickness direction of the metal body, When the area of the proximity region is set to S [mm 2 , and the frequency included in the frequency band is set to f [MHz], the following is satisfied: 9.59×10 3 / f ≤ S ≤ 3.24×10 5 / f。 15. The antenna device according to claim 13, wherein, and the ground conductor includes a connection conductor connecting the ground electrode and the conductive member.

16. The antenna device according to claim 13, wherein, The conductive member includes an elastomer.

17. The antenna device according to claim 16, wherein, The elastomer includes a rod-shaped gasket, and the gasket is coated with a conductive coating film on its outer surface.

18. The antenna device according to claim 13, wherein, The metal body includes a flange opposite to the vehicle glass plate, and the conductive member is interposed between the glass plate and the flange.

19. The antenna device according to any one of claims 1 to 3, wherein, It is provided with an inductor connected in series with the antenna element and having one end electrically connected to the power supply electrode.

20. The antenna device according to any one of claims 1 to 3, wherein, The frequency band is at least one of the frequency bands of FM broadcast waves, DAB Band III, and terrestrial digital television broadcast waves.

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