Antenna device and vehicle antenna system

Abstract

The present invention reduces interference between signals that are input to and output from a feeder point, and reduces the size of an antenna apparatus.　This antenna apparatus comprises a flat antenna conductor provided on a first main surface, and a ground conductor provided on a second main surface. The shape of the flat antenna conductor, when viewed in plan, is line-symmetrical with respect to a first virtual line and a second virtual line which are parallel to a part of the outer edge of the flat antenna conductor and are orthogonal to each other. When an orthogonal coordinate system is defined that has the first virtual line and the second virtual line as coordinate axes, the flat antenna conductor has corner portions respectively positioned at coordinates (+L, +L), (-L, +L), (-L, -L), and (+L, -L), a first feeder point positioned at coordinates (+a×(1±b), +a×(1±b)), and a second feeder point positioned at coordinates (-a×(1±b), +a×(1±b)), the outer edge being located inside a square region of 2×L on a side, wherein a satisfies 0.10×L≦a≦0.60×L, and b satisfies 0≦b≦0.10.

Description

[Technical Field]

[0001] The present disclosure relates to an antenna device and a vehicle antenna system. [Background technology]

[0002] Mobile objects such as vehicles equipped with communication devices are equipped with antennas that transmit and receive (either or both) radio waves in a specific frequency band. In particular, it is known to use array antennas, which are arrays of multiple antennas, in order to improve the sensitivity of transmission and reception.

[0003] An array antenna is configured by arranging multiple antenna elements, such as patch antennas. However, due to this configuration, narrowing the spacing between adjacent antenna elements increases mutual coupling between the adjacent antenna elements, resulting in a reduction in antenna gain.

[0004] Therefore, a technique is known in which mutual coupling between adjacent antenna elements is reduced by providing a coupling line near the adjacent antenna elements (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2017 / 216871 Summary of the Invention [Problem to be solved by the invention]

[0006] However, with a configuration in which one feed probe is connected to each of a plurality of antenna elements as in Patent Document 1, it is difficult to reduce the size of the antenna device.

[0007] The present disclosure provides an antenna device that includes a single planar antenna conductor having two feed points through which signals related to radio waves in a predetermined frequency band are input and output, and that is capable of reducing interference between signals input and output to both feed points and of being miniaturized, and a vehicle antenna system that includes the antenna device. [Means for solving the problem]

[0008] In one aspect of the present disclosure, a dielectric layer having a first major surface and a second major surface opposite the first major surface; a planar antenna conductor provided on the first principal surface; a ground conductor provided on the second main surface, the shape of the planar antenna conductor is, in a plan view, symmetrical with respect to a first imaginary line and a second imaginary line that are parallel to a part of an outer edge of the planar antenna conductor and perpendicular to each other; When a Cartesian coordinate system having the first virtual line and the second virtual line as its coordinate axes is defined, the planar antenna conductor has corners located at coordinates (+L, +L), (-L, +L), (-L, -L), and (+L, -L), a first feed point located at coordinates (+a×(1±b), +a×(1±b)), and a second feed point located at coordinates (-a×(1±b), +a×(1±b)); The outer edge is inside a square area with one side being 2×L, a satisfies 0.10×L≦a≦0.60×L, There is provided an antenna device, wherein b satisfies 0≦b≦0.10.

[0009] In another aspect of the present disclosure, There is provided a vehicle antenna system comprising the antenna device and a vehicle to which the antenna device is attached. [Effects of the Invention]

[0010] The present disclosure can provide an antenna device that includes a single planar antenna conductor having two feed points through which signals related to radio waves in a predetermined frequency band are input and output, and that can reduce interference between the signals input and output to both feed points and can be made smaller, as well as a vehicle antenna system that includes the antenna device. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a plan view showing a configuration example of an antenna device according to a first embodiment. [Figure 2] 1 is a cross-sectional view showing an example of the configuration of an antenna device according to a first embodiment. [Figure 3] FIG. 10 is a plan view showing a configuration example of an antenna device according to a second embodiment. [Figure 4] FIG. 10 is an exploded perspective view showing a configuration example of an antenna device according to a second embodiment. [Figure 5A] 3 is a cross-sectional view showing an example of mounting the antenna device to a vehicle in each embodiment. FIG. [Figure 5B] 3 is a cross-sectional view showing an example of mounting the antenna device to a vehicle in each embodiment. FIG. [Figure 5C] 3 is a cross-sectional view showing an example of mounting the antenna device to a vehicle in each embodiment. FIG. [Figure 5D] 3 is a cross-sectional view showing an example of mounting the antenna device to a vehicle in each embodiment. FIG. [Figure 6] FIG. 10 is a plan view showing a first modified example of the cutout portion. [Figure 7] FIG. 10 is a plan view showing a second modified example of the cutout portion. [Figure 8A] 10 is a plan view showing an example of the configuration of an antenna device showing a power feeding configuration using a transmission line via a connector. FIG. [Figure 8B] 10 is a plan view showing an example of the configuration of an antenna device showing another power feeding configuration using a transmission line via a connector. FIG. [Figure 9] 10A to 10C are diagrams illustrating application examples of the antenna devices in the respective embodiments. [Figure 10]5 is a diagram showing an example of a simulation result of a reflection coefficient S11 and a transmission coefficient S21 of the antenna device according to the first embodiment. FIG. [Figure 11] FIG. 10 is a diagram showing an example of a simulation result of a reflection coefficient S11 and a transmission coefficient S21 of the antenna device according to the second embodiment. [Figure 12] 10A and 10B are diagrams illustrating an example of a simulation result when the notch depth of the notch portion is changed. [Figure 13] 10A and 10B are diagrams illustrating an example of a simulation result when the width of the cutout portion is changed. [Figure 14] FIG. 10 is a diagram showing an example of a simulation result when the thickness of a dielectric layer is changed. [Figure 15] FIG. 10 is a diagram showing an example of a simulation result of a resonance frequency when the length of one side of a dielectric layer is changed. [Figure 16] FIG. 10 is a diagram showing an example of a simulation result of the wavelength of the resonant frequency when the length of one side of the dielectric layer is changed. [Figure 17] FIG. 10 is a diagram showing an example of a simulation result of the reflection coefficient S11 when the area ratio between the planar antenna conductor and the ground conductor is changed. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, each embodiment according to the present disclosure will be described with reference to the drawings. Note that for ease of understanding, the scale of each part in the drawings may differ from the actual scale. Deviations in directions such as parallel, right-angled, orthogonal, horizontal, vertical, up-down, and left-right are permitted to the extent that they do not impair the effects of the embodiments. The shape of the corners is not limited to right angles and may be rounded like an arch. The X-axis, Y-axis, and Z-axis directions represent directions parallel to the X-axis, Y-axis, and Z-axis, respectively. The X-axis, Y-axis, and Z-axis directions are mutually orthogonal. The XY plane, YZ plane, and ZX plane represent imaginary planes parallel to the X-axis and Y-axis directions, imaginary planes parallel to the Y-axis and Z-axis directions, and imaginary planes parallel to the Z-axis and X-axis directions, respectively.

[0013] The antenna device according to the present disclosure transmits and receives (either or both) radio waves in a predetermined frequency band F, and is suitable for transmitting and receiving radio waves in a high frequency band (e.g., 300 MHz or higher and 300 GHz or lower) equal to or higher than the UHF (Ultra High Frequency) band. The predetermined frequency band F may be one contiguous frequency band or multiple contiguous frequency bands. For example, if frequency band F consists of two frequency bands, a contiguous frequency band L and a frequency band H higher than frequency band L, there may be a frequency band between frequency band L and frequency band H in which the antenna device does not transmit or receive.

[0014] The UHF band refers to a frequency band between 300 MHz and 3 GHz. Specific examples of frequency bands included in the UHF band include the band used for terrestrial digital television broadcast waves (e.g., 473 MHz to 713 MHz). For example, an antenna device according to the present disclosure is suitable for receiving terrestrial digital television broadcast waves.

[0015] The frequency band F may include one or both of the SHF (Super High Frequency) band of 3 GHz or more and 30 GHz or less and the EHF (Extremely High Frequency) band of 30 GHz or more and 300 GHz or less. For example, the antenna device according to each embodiment of the present disclosure may be applied to a V2X communication system, a fifth-generation mobile communication system (so-called 5G), an in-vehicle radar system, etc., but the systems to which the antenna device according to each embodiment of the present disclosure is applied are not limited to these. An example of a V2X communication system is an ETC system.

[0016] When the antenna device according to each embodiment of the present disclosure is applied to use in the frequency band (3.3 GHz or higher) below 6 GHz (sub6) or the FR1 band (7.125 GHz or lower) including Band n41, among the frequency bands used in 5G, it can be applied to transmitting and receiving radio waves in the 5.8 GHz band or 5.9 GHz band. However, the antenna device according to each embodiment of the present disclosure may also be applied to the 4G LTE frequency band.

[0017] Fig. 1 is a plan view showing an example of the configuration of an antenna device according to the first embodiment. Fig. 2 is a cross-sectional view showing an example of the configuration of an antenna device according to the first embodiment. The antenna device 101 shown in Figs. 1 and 2 is a patch antenna that transmits and receives radio waves in a predetermined frequency band F. The antenna device 101 includes a dielectric layer 10, a planar antenna conductor 20, and a ground conductor 30. A patch antenna is also called a planar antenna.

[0018] The dielectric layer 10 has a main surface 11 and a main surface 12 opposite to the main surface 11 in the Z-axis direction. The main surface 11 is an example of a first main surface, and the main surface 12 is an example of a second main surface. Both main surfaces 11 and 12 are surfaces parallel to the XY plane. The Z-axis direction corresponds to the thickness direction of the dielectric layer 10.

[0019] The dielectric layer 10 is composed of one or more members whose main component is a dielectric. The dielectric layer 10 may be a plate-shaped or sheet-shaped substrate. Examples of materials for the dielectric layer 10 include glass such as quartz glass, ceramics, and resin.

[0020] The planar antenna conductor 20 is a patch conductor provided on the principal surface 11 and arranged parallel to the XY plane. The planar antenna conductor 20 may be a conductor pattern formed on the principal surface 11, or may be formed by a conductor sheet or conductor substrate arranged on the principal surface 11. Examples of conductor materials used for the planar antenna conductor 20 include, but are not limited to, gold, silver, copper, aluminum, platinum, and chromium.

[0021] The ground conductor 30 is a planar conductor provided on the principal surface 12 and is arranged parallel to the XY plane. The ground conductor 30 may be a conductor pattern formed on the principal surface 12, or may be formed by a conductor sheet or conductor substrate arranged on the principal surface 12. Examples of conductor materials used for the ground conductor 30 include, but are not limited to, gold, silver, copper, aluminum, platinum, and chromium.

[0022] The shape of the planar antenna conductor 20 is symmetrical with respect to imaginary lines 41 and 42, which are parallel to a part of the outer edge 21 of the planar antenna conductor 20 and perpendicular to each other, when viewed from the Z-axis direction. The imaginary line 41 is an example of a first imaginary line. The imaginary line 42 is an example of a second imaginary line. In this example, the outer edge 21 has edges 21a, 21b, 21c, and 21d, and the imaginary line 41 is parallel to edges 21b and 21d, and the imaginary line 42 is parallel to edges 21a and 21c.

[0023] Here, a Cartesian coordinate system is defined with the virtual lines 41 and 42 as its coordinate axes. This Cartesian coordinate system is a two-dimensional coordinate system with the origin O being the intersection of the virtual lines 41 and 42. The origin O is the intersection of two different symmetric axes (the virtual lines 41 and 42), and is the center of gravity of the planar antenna conductor 20.

[0024] When this Cartesian coordinate system is defined, the planar antenna conductor 20 has corners 22a, 22b, 22c, and 22d located at coordinates (+L, +L), (-L, +L), (-L, -L), and (+L, -L), respectively, a feed point 23 located at coordinates (+a×(1±b), +a×(1±b)), and a feed point 24 located at coordinates (-a×(1±b), +a×(1±b)). The feed point 23 is an example of a first feed point. The feed point 24 is an example of a second feed point. Both L and a are non-negative values ​​(absolute values). Furthermore, a is expressed as follows: 0.10×L≦a≦0.60×L...Formula 1a Furthermore, b only needs to satisfy 0≦b≦0.10, preferably 0≦b≦0.05, and more preferably b=0.

[0025] In this embodiment, the feed point 23 is located on or near an imaginary line 43 connecting the corners 22a and 22c, and the feed point 24 is located on or near an imaginary line 44 connecting the corners 22b and 22d.

[0026] The outer edge 21 of the planar antenna conductor 20 is located inside a square region 50 with a side length of 2×L in plan view from the Z-axis direction. The square region 50 includes a square perimeter 51 of the square region 50 inside. The square region 50 corresponds to the region obtained by projecting an imaginary square with a side length of 2×L from the Z-axis direction onto the main surface 11 of the dielectric layer 10. In this embodiment, the perimeter 51 has four sides 51a, 51b, 51c, and 51d, and the edges 21a, 21b, 21c, and 21d coincide with the corresponding sides 51a, 51b, 51c, and 51d in plan view.

[0027] Antenna device 101 includes a single planar antenna conductor 20 having two feed points 23 and 24, which input and output (either input or output, or both) signals related to radio waves in frequency band F. By arranging the two feed points 23 and 24 at coordinate positions that satisfy formula 1a, current flows near feed points 23 and 24 such that the directional vector of the current flowing near feed point 23 is perpendicular to the directional vector of the current flowing near feed point 24. For example, the current flowing near feed point 23 flows along imaginary line 43 from corner 22c toward corner 22a, and the current flowing near feed point 24 flows along imaginary line 44 from corner 22d toward corner 22b.

[0028] Also, a is 0.15×L≦a≦0.55×L...Formula 1b It is preferable to satisfy 0.20×L≦a≦0.50×L...Formula 1c It is more preferable to satisfy the following.

[0029] Current flows near feed points 23 and 24 so that the directional vector of the current flowing near feed point 23 and the directional vector of the current flowing near feed point 24 are orthogonal, thereby reducing interference between signals input / output to / from feed point 23 and signals input / output to / from feed point 24. In particular, by setting the shortest conductive path length between feed point 23 and feed point 24 to be in the range of about k×λ0 / 4 (for example, not less than k×(λ0 / 4−λ0 / 5) and not more than k×(λ0 / 4+λ0 / 20)), the node of the current distribution between feed point 23 and feed point 24 is located near feed points 23 and 24, thereby reducing the interference. Furthermore, the shortest conductive path length between feed point 23 and feed point 24 is preferably in the range of k×(λ0 / 4−3λ0 / 20) or more and k×(λ0 / 4+λ0 / 20) or less, and more preferably in the range of k×(λ0 / 4−λ0 / 10) or more and k×(λ0 / 4+λ0 / 20) or less.

[0030] 1, the shortest conductive path length represents the linear distance between the feed point 23 and the feed point 24, and represents the shortest path length that bypasses the cutout portion 25b in the example shown in Fig. 3 described later. Also, λ0 is the wavelength of radio waves in the air at the resonant frequency f0 of the planar antenna conductor 20 when the planar antenna conductor 20 has the same shape as the square region 50, and k is the wavelength shortening rate of the dielectric layer 10.

[0031] The reduction in interference between the signals input / output to / from feed point 23 and the signals input / output to / from feed point 24 can improve the isolation between feed point 23 and feed point 24. Furthermore, since the two isolated feed points 23, 24 are present on a single planar antenna conductor 20, the antenna device can be made smaller than in a conventional configuration in which one feed point is provided for each of a plurality of antenna elements.

[0032] a satisfies the above formula 1a. If a does not satisfy formula 1a, feed point 23 is located closer to the center of gravity O or corner 22a, and feed point 24 is located closer to the center of gravity O or corner 22b. In this case, the orthogonal relationship between the directional vector of the current flowing near feed point 23 and the directional vector of the current flowing near feed point 24 is lost, and further, the shortest conduction path length between feed point 23 and feed point 24 becomes approximately k × λ0 / 2, thereby reducing the isolation between feed point 23 and feed point 24.

[0033] 1, the shape of the planar antenna conductor 20 is a square with a side length of 2×L in a planar view. This increases the degree to which the directional vector of the current flowing near the feed point 23 and the directional vector of the current flowing near the feed point 24 are orthogonal, and the shortest conduction path length between the feed points 23 and 24 becomes approximately k×λ0 / 4, thereby improving the isolation between the feed points 23 and 24. In the embodiment shown in FIG. 1, edges 21a, 21b, 21c, and 21d included in the outer edge 21 of the planar antenna conductor 20 correspond to the four sides of the square.

[0034] FIG. 3 is a plan view showing a configuration example of an antenna device according to the second embodiment. The description of the second embodiment, which is similar to that of the first embodiment, will be omitted by referencing the above description of the first embodiment. The outer edge 21 of the planar antenna conductor 20 of the antenna device according to the second embodiment is common to the entire periphery 51 of the square region 50 in the antenna device 101 shown in FIG. 1 , whereas the outer edge 21 of the planar antenna conductor 20 is common to a part of the periphery 51 of the square region 50 in the antenna device 102 shown in FIG. 3 . Furthermore, in the antenna device 102 shown in FIG. 3 , the planar antenna conductor 20 has four identically shaped cutout portions 25a, 25b, 25c, and 25d that overlap either the imaginary line 41 or the imaginary line 42 in a planar view. By providing these four cutout portions 25a, 25b, 25c, and 25d, the planar antenna conductor 20 can increase the resonant frequencies in a predetermined frequency band, thereby enabling the planar antenna conductor 20 to be broadened in bandwidth and miniaturized. Furthermore, it becomes easy to tune the resonance frequency of the planar antenna conductor 20 to a desired value.

[0035] Examples of the shape of the cutout portions 25a, 25b, 25c, and 25d include a square, a rectangle, and a trapezoid, but are not limited to these as long as the shape of the planar antenna conductor 20 is line-symmetrical with respect to the imaginary lines 41 and 42. When the cutout portions 25a, 25b, 25c, and 25d have such shapes, it becomes easy to tune the resonant frequency of the planar antenna conductor 20 to a desired value. Fig. 3 shows an example in which the cutout portions 25a, 25b, 25c, and 25d have rectangular shapes.

[0036] The depth of the cutout portions 25a, 25b, 25c, and 25d is defined as D, and the width of the cutout portions 25a, 25b, 25c, and 25d is defined as W. In this case, W and D are expressed as follows: 0.10×L≦W≦0.85×L...Formula 2a 0.14×L≦D≦0.54×L...Formula 3a When the above expression is satisfied, matching can be easily achieved at the resonant frequency f of the planar antenna conductor 20 having the cutout portions 25a, 25b, 25c, and 25d. When the shape of the cutout portions 25a, 25b, 25c, and 25d is rectangular, the cutout depth D is the long side of the rectangle, and the cutout width W is the short side.

[0037] Since W and D are easily matched at the resonant frequency f of the planar antenna conductor 20, 0.15×L≦W≦0.74×L...Formula 2b 0.21×L≦D≦0.53×L...Equation 3b It is preferable to satisfy 0.21×L≦W≦0.63×L...Formula 2c 0.26×L≦D≦0.52×L...Formula 3c It is more preferable to satisfy the following.

[0038] When the planar antenna conductor 20 has the same shape as the square region 50 (i.e., when there are no notches 25a, 25b, 25c, and 25d), the wavelength of the radio wave in the air at the resonance frequency f0 of the planar antenna conductor 20 is λ0, and the wavelength shortening rate of the dielectric layer 10 is k. In this case, D is given by 0.030×k×λ0≦D≦0.100×k×λ0...Equation 4a If the above condition is satisfied, isolation between the feeding point 23 and the feeding point 24 can be ensured in a state where the planar antenna conductor 20 having the notches 25a, 25b, 25c, and 25d is matched at the resonance frequency f.

[0039] D is a value that ensures isolation between the feeding point 23 and the feeding point 24 in a state where the planar antenna conductor 20 having the notched portions 25a, 25b, 25c, and 25d is matched at the resonant frequency f. 0.035×k×λ0≦D≦0.090×k×λ0...Equation 4b It is preferable to satisfy 0.040×k×λ0≦D≦0.080×k×λ0...Formula 4c It is more preferable to satisfy the following.

[0040] When the planar antenna conductor 20 has the same shape as the square region 50 (i.e., when there are no notches 25a, 25b, 25c, and 25d), the wavelength of the radio wave in the air at the resonance frequency f0 of the planar antenna conductor 20 is λ0, and the wavelength shortening rate of the dielectric layer 10 is k. In this case, W is given by 0.001×k×λ0≦W≦0.200×k×λ0...Equation 5a If the above condition is satisfied, isolation between the feeding point 23 and the feeding point 24 can be ensured in a state where the planar antenna conductor 20 having the notches 25a, 25b, 25c, and 25d is matched at the resonance frequency f.

[0041] W is set to ensure isolation between the feeding point 23 and the feeding point 24 in a state where the planar antenna conductor 20 having the notched portions 25a, 25b, 25c, and 25d is matched at the resonant frequency f. 0.002×k×λ0≦W≦0.160×k×λ0...Equation 5b It is preferable to satisfy 0.005×k×λ0≦W≦0.110×k×λ0...Formula 5c It is more preferable to satisfy the following.

[0042] Fig. 4 is an exploded perspective view showing an example of the configuration of an antenna device according to the second embodiment. The dielectric layer 10 does not have to be made up of a single dielectric member, and may be made up of a plurality of dielectric members as shown in Fig. 4. In the antenna device 102 according to the second embodiment, the dielectric layer 10 has a spacer 15 and a dielectric substrate 14. Note that the dielectric layer 10 of the antenna device 101 according to the first embodiment may also be formed as shown in Fig. 4.

[0043] The dielectric substrate 14 has a main surface 11 on which the planar antenna conductor 20 is provided. The dielectric substrate 14 is, for example, a glass epoxy plate, but is not limited to this.

[0044] The spacer 15 is a dielectric member for ensuring a predetermined distance or more between the planar antenna conductor 20 and the ground conductor 30. The spacer 15 has a main surface 12 to which the ground conductor 30 is attached, and a main surface opposite to the main surface 12 to which the dielectric substrate 14 is attached. The material of the spacer 15 is, for example, a resin such as polylactic acid (PLA), but is not limited to this.

[0045] The spacer 15 has a space 16. By providing the space 16, the spacer 15 can reduce the weight of the antenna device 102 while maintaining a predetermined distance or more between the planar antenna conductor 20 and the ground conductor 30. Providing the spacer 15 facilitates wiring of a feeder line such as a coaxial cable, which will be described later. Furthermore, by including the spacer 15 in addition to the dielectric substrate 14, the dielectric layer 10 can also adjust the wavelength shortening rate k and the dielectric constant ε of the dielectric layer 10.

[0046] Fig. 5A is a cross-sectional view showing an example of mounting the antenna device in each embodiment to a vehicle. Fig. 5A shows, as a representative example, an example of mounting the antenna device 102 in the second embodiment to a vehicle 301. The description of Fig. 5A also applies to the case where the antenna device 101 in the first embodiment is mounted to a vehicle. The antenna system 201 shown in Fig. 5A is an example of a vehicle antenna system, and includes the antenna device 102 and the vehicle 301. The antenna device 102 is mounted to the vehicle 301.

[0047] The ground conductor 30 is electrically connected to a conductive metal part 302 of the vehicle 301, and may be connected, for example, by DC connection or capacitive coupling. This allows the radio waves traveling from the planar antenna conductor 20 to the metal part 302 to be directed in the opposite direction of the metal part 302 with respect to the planar antenna conductor 20 (in this example, the positive side in the Z-axis direction). This improves the antenna gain on the opposite side of the metal part 302 with respect to the planar antenna conductor 20.

[0048] 5A shows a configuration in which the ground conductor 30 is electrically connected to the metal part 302 of the vehicle 301, but the metal part 302 may also be the ground conductor 30. In other words, the antenna device 102 may use the metal part 302 of the vehicle 301 as the ground conductor of the planar antenna conductor 20. Even in a configuration in which the metal part 302 is used in this way, the antenna gain on the side opposite to the metal part 302 with respect to the planar antenna conductor 20 is improved, similar to the configuration shown in FIG.

[0049] Furthermore, the outer edge 302a of the metal part 302 may be located outside the outer edge 21 of the planar antenna conductor 20 in plan view in the Z-axis direction. This allows the radio waves traveling from the planar antenna conductor 20 to the metal part 302 to be directed more toward the side of the planar antenna conductor 20 opposite the metal part 302 (in this example, the positive side in the Z-axis direction). This further improves the antenna gain on the side of the planar antenna conductor 20 opposite the metal part 302.

[0050] The metal part 302 may be a part of the metal body of the vehicle 301, or may be a part of a metal member (such as a back door) attached to the metal body.

[0051] The surface of the planar antenna conductor 20 is approximately perpendicular to the horizontal plane, and when the surface is positioned further outward from the vehicle 301 than the ground conductor 30, the antenna gain in the horizontal plane of the planar antenna conductor 20 improves from the planar antenna conductor 20 toward the outside of the vehicle 301. In the example shown in Fig. 5A, if the ZX plane is the horizontal plane, the surface of the planar antenna conductor 20 is approximately perpendicular to the horizontal plane. However, this is not limiting, and the surface of the planar antenna conductor 20 may have an inclination with respect to the horizontal plane (for example, an inclination of 45° or more and less than 90° with respect to the horizontal plane) due to an inclination of the metal part 302 at the mounting position on the vehicle 301.

[0052] The feed point 23 is electrically connected to a feed line 60 such as a coaxial cable or a planar waveguide. The feed line 60 has a signal line 61 electrically connected to the feed point 23 and a ground portion 62 electrically connected to the ground conductor 30. Specific examples of planar waveguides include a coplanar line and a microstrip line. Although not shown in FIG. 5A , the feed line electrically connected to the feed point 24 has the same configuration as the feed line electrically connected to the feed point 23.

[0053] Fig. 5B is a cross-sectional view showing another example of mounting the antenna device in each embodiment to a vehicle, in which the same components (component materials) as those in the mounting example of Fig. 5A are denoted by the same reference numerals, and description of these components (component materials) will be omitted. In the antenna system 201 shown in Fig. 5B, a feeder line 60 such as a coaxial cable extends in the Z-axis direction and has a signal line 61 electrically connected to the feed point 23 and a grounding part 62 electrically connected to the grounding conductor 30. In this case, a conductive metal part 302 of the vehicle 301 may be formed with a hole through which the feeder line 60 is inserted.

[0054] Fig. 5C is a cross-sectional view showing yet another example of mounting the antenna device of each embodiment to a vehicle. The same components (component materials) as those in the mounting example of Fig. 5A are assigned the same reference numerals, and description of these components (component materials) will be omitted. In the antenna system 201 shown in Fig. 5C, the feeder line 60 includes a transmission line (signal pattern 31) on a dielectric substrate 32, such as a microstrip line, and has a signal line 61 electrically connected to the feed point 23 and a ground portion 62 electrically connected to the ground conductor 30. In the antenna system 201 of Fig. 5C, the feeder line 60 includes a coaxial cable and a microstrip line connected to the coaxial cable. The microstrip line (dielectric substrate 32) may also include circuits such as various filters and amplifiers.

[0055] FIG. 5D is a cross-sectional view showing yet another example of mounting the antenna device of each embodiment to a vehicle. The same components (component materials) as those in the mounting example of FIG. 5C are denoted by the same reference numerals, and a description of these components (component materials) will be omitted. In the antenna system 201 shown in FIG. 5D, the feeder line 60 includes a transmission line (signal pattern 31) on a dielectric substrate 32, such as a microstrip line. The signal line 61 is electrically connected to the feed point 23, and the grounding portion 62 is electrically connected to the grounding conductor 30. In the mounting example shown in FIG. 5D, the transmission line (signal pattern 31) on the dielectric substrate 32, such as a microstrip line, is arranged upside down relative to the configuration shown in FIG. 5C. In the mounting example shown in FIG. 5D, the feeder line 60 includes a coaxial cable and a microstrip line connected to the coaxial cable. In the mounting example shown in FIG. 5D, the signal pattern 31 is arranged so as to be electrically (high frequency) separated from the metal portion 302. The microstrip line (dielectric substrate 32) may also be provided with circuits such as various filters and amplifiers.

[0056] FIG. 6 is a plan view showing a first modification of the notch portion. FIG. 7 is a plan view showing a second modification of the notch portion. Both the antenna device 102A shown in FIG. 6 and the antenna device 102B shown in FIG. 7 have trapezoidal notch portions 25a, 25b, 25c, 25d. The trapezoidal notch portions 25a, 25b, 25c, 25d shown in FIG. 6 each have an upper side with a notch width W1 and a lower side with a notch width W2, and the notch width widens toward the inside (W1 < W2). The trapezoidal notch portions 25a, 25b, 25c, 25d shown in FIG. 7 each have an upper side with a notch width W2 and a lower side with a notch width W1, and the notch width widens toward the outside (W2 < W1). By changing the shape of the notch portion as shown in FIG. 6 or FIG. 7, one or more resonance frequencies of the planar antenna conductor 20 can be tuned. W1 and W2 are each an example of the notch width W described above.

[0057] Also, in the antenna device in each embodiment, when the planar antenna conductor 20 has the same shape as the square region 50 (that is, when there are no notch portions 25a, 25b, 25c, 25d), let the wavelength of the radio wave in air at the resonance frequency f0 of the planar antenna conductor 20 be λ0. Also, let the thickness of the dielectric layer 10 be d, and the wavelength shortening rate of the dielectric layer 10 be k. At this time, d is 0.018 × k × λ0 ≤ d ≤ 0.096 × k × λ0 ··· Equation 6a When this is satisfied, matching can be easily achieved at the resonance frequency f0 or the resonance frequency f of the planar antenna conductor 20. Note that the resonance frequency f is the resonance frequency of the planar antenna conductor 20 having the notch portions 25a, 25b, 25c, 25d as described above, and by satisfying Equation 6a including λ0, matching at the resonance frequency f also becomes easy.

[0058] d is for easily achieving matching at the resonance frequency f0 or the resonance frequency f of the planar antenna conductor 20, 0.036 × k × λ0 ≤ d ≤ 0.087 × k × λ0 ··· Equation 6b It is preferable to satisfy 0.054 × k × λ0 ≤ d ≤ 0.077 × k × λ0 ··· Equation 6c It is more preferable to satisfy the following.

[0059] In the antenna device of each embodiment, the shape of the dielectric layer 10 may be a square with a side length of Ld in plan view. In this case, Ld is 2.0×L≦Ld≦6.0×L...Formula 7a If the above condition is satisfied, the planar antenna conductor 20 can be miniaturized while being matched at the resonant frequency f0 or the resonant frequency f of the planar antenna conductor 20.

[0060] Ld is set to a value that is smaller than the planar antenna conductor 20 while matching the planar antenna conductor 20 at the resonant frequency f0 or the resonant frequency f. 2.0×L≦Ld≦3.0×L...Formula 7b It is preferable to satisfy 2.0×L≦Ld≦2.7×L...Formula 7c It is more preferable to satisfy 2.0×L≦Ld≦2.4×L...Formula 7d It is more preferable that the following be satisfied.

[0061] In the antenna device of each embodiment, the area of ​​the planar antenna conductor 20 is S ANT , the area of ​​the ground conductor 30 is S GND In this case, S GND / S ANT teeth, S GND / S ANT ≧0.8 ···Formula 8a If the above expression is satisfied, matching can be easily achieved at the resonant frequency f0 or the resonant frequency f of the planar antenna conductor 20.

[0062] S GND / S ANT is set to easily achieve matching at the resonant frequency f0 or the resonant frequency f of the planar antenna conductor 20. S GND / S ANT ≧1.0 ···Equation 8b It is preferable to satisfy S GND / S ANT ≧1.4 ···Formula 8c It is more preferable to satisfy the following.

[0063] 8A is a plan view showing an antenna device 102 including transmission lines 33 and 34 formed on a dielectric substrate 32 and connected to feed points 23 and 24, respectively, and a connector 38 for drawing out and connecting these two transmission lines. The transmission lines 33, 34, and connector are arranged in the negative Z-axis direction with respect to the planar antenna 20. The antenna device 102 shown in FIG. 8A has the connector 38 near an end edge of the antenna device 102 in a planar view, and the transmission lines 33 and 34 branch out from the connector and connect to feed points 23 and 24, respectively.

[0064] 8B is a plan view showing an antenna device 102 including transmission lines 33 and 34 formed on a dielectric substrate 32 and connected to feed points 23 and 24, respectively, and a connector 38 for drawing out and connecting these two transmission lines. The transmission lines 33, 34, and connector are arranged in the negative Z-axis direction with respect to the planar antenna 20. The antenna device 102 shown in FIG. 8B has the connector 38 in the center of the antenna device 102 in a planar view, and the transmission lines 33 and 34 branching from the connector are connected to feed points 23 and 24, respectively.

[0065] 9 is a diagram showing an application example of the antenna devices in each embodiment. In FIG. 9, an application example of the antenna device 101 in the first embodiment is shown as a representative example. The explanation of FIG. 9 also applies to the case where the antenna device 102 in the second embodiment is applied. The antenna system shown in FIG. 9 has a plurality of antenna devices 101, a plurality of adjusters 111 and 112, and a combiner 120.

[0066] The multiple adjusters 111 and 112 are provided for each of the multiple antenna devices 101 and are circuits electrically connected to the feed points 23 and 24 of the corresponding antenna devices 101. The adjuster 111 includes a phase shifter that changes the phase of the signal output from the feed point 23 and an amplifier that changes the amplitude of the signal output from the feed point 23. The adjuster 112 includes a phase shifter that changes the phase of the signal output from the feed point 24 and an amplifier that changes the amplitude of the signal output from the feed point 24. The adjusters 111 and 112 change either or both of the phase and amplitude of the signals output from the feed points 23 and 24 by utilizing the orthogonality of the directional vectors of the currents flowing near the feed points 23 and 24. In this way, the adjusters 111 and 112 optimally adjust the reception state output from the combiner 120 to match the electric field state, such as linear polarization (horizontal polarization, vertical polarization), circular polarization (right-handed, left-handed), or oblique polarization. The combiner 120 combines the signals output from the feeding points 23 and 24. The combined signal is demodulated by the demodulator.

[0067] Next, the simulation results of the antenna devices in each embodiment will be described.

[0068] In the simulation results described below, the reflection coefficient S11 represents the reflection gain as seen from the feed point 23 (more specifically, in FIG. 5A , the observation point between the tip of the signal line 61 on the ground portion 62 side and the ground conductor 30), and the lower the reflection coefficient S11, the better the matching. The transmission coefficient S21 represents the pass characteristic from the feed point 23 to the feed point 24, and the lower the transmission coefficient S21, the better the isolation from the feed point 23 to the feed point 24 is ensured. Note that in the antenna devices according to the embodiments of the present disclosure, the planar antenna conductor 20 has a symmetrical structure as described above. Therefore, the reflection coefficient S22 (the reflection gain as seen from the feed point 24) is the same as the reflection coefficient S11, and the transmission coefficient S12 (the pass characteristic from the feed point 24 to the feed point 23) is the same as the transmission coefficient S21.

[0069] Fig. 10 is a diagram showing an example of a simulation result of the reflection coefficient S11 and the transmission coefficient S21 of the antenna device 101 in the first embodiment. As shown in Fig. 10, in the vicinity of approximately 600 MHz, which is included in the band of terrestrial digital television broadcast waves as the predetermined frequency band F, a result was obtained in which isolation between the feed point 23 and the feed point 24 was achieved in a matched state. Note that λ0 at 600 MHz is approximately 500 mm.

[0070] The conditions for the dimensions of each part (see Figures 1 and 2) during the simulation shown in Figure 10 are as follows: L: 110mm 2×L:220mm a:45mm 2×a:90mm Ld: 240mm d:20mm k: approx. 0.95 In this case, a≒0.41×L, d≒0.042×k×λ0, and Ld≒2.2×L. The area of ​​the ground conductor is equivalent to Ld×Ld, and S GND / S ANT ≈1.2. Furthermore, the shortest conductive path length (2×a) between the feed point 23 and the feed point 24 was approximately 0.19×k×λ0.

[0071] 11 is a diagram showing an example of a simulation result of the reflection coefficient S11 and the transmission coefficient S21 of the antenna device 102 according to the second embodiment. As shown in FIG. 11, a result was obtained in which isolation between the feed point 23 and the feed point 24 was achieved in a matched state at a first resonance frequency of approximately 550 MHz, which is included in the band of terrestrial digital television broadcast waves, as the predetermined frequency band F. Furthermore, by providing the cutout portions 25a, 25b, 25c, and 25d, a result was obtained in which the planar antenna conductor 20 resonated at a second resonance frequency of approximately 680 MHz, which is included in the band of terrestrial digital television broadcast waves, as the predetermined frequency band F. In this case, the resonance frequency f0 when assuming a configuration without the cutout portions is 644 MHz, and λ0 at 644 MHz is approximately 466 mm.

[0072] The conditions for the dimensions of each part (see Figures 3 and 4) during the simulation shown in Figure 11 are as follows: L: 95mm 2×L:190mm a:25mm 2×a:50mm Ld: 228mm d:20mm D: 45mm W: 22mm k: approx. 0.95 In this case, a≒0.26×L, W≒0.23×L, D≒0.47×L, D≒0.102×k×λ0, W≒0.050×k×λ0, d≒0.045×k×λ0, and Ld=2.4×L. The area of ​​the ground conductor 30 corresponds to Ld×Ld, and S GND / S ANT ≈1.44. Furthermore, the shortest conductive path length between the feed point 23 and the feed point 24 was approximately 0.11 × k × λ0.

[0073] Fig. 12 is a diagram showing an example of a simulation result when the cutout depth D of the rectangular cutout portions 25a, 25b, 25c, and 25d is changed in the antenna device 102 according to the second embodiment. As shown in Fig. 12, when 0.03 × k × λ0 ≦ D ≦ 0.10 × k × λ0, isolation between the feed point 23 and the feed point 24 is ensured in a state where the planar antenna conductor 20 having the cutout portions 25a and the like is matched at the resonant frequency f.

[0074] The conditions for the dimensions of each part (see FIGS. 3 and 4) during the simulation shown in FIG. 12 were the same as those for FIG. 11, except for the notch depth D. λ / λ0 in FIG. 12 is the ratio between the wavelength λ0 corresponding to the resonant frequency f0 when there is no notch and the wavelength λ corresponding to the resonant frequency f when the notch depth is D. λ / λ0 represents the amount of change in wavelength λ from the wavelength λ0 corresponding to the resonant frequency f0 when there is no notch.

[0075] Fig. 13 is a diagram showing an example of a simulation result when the cutout width W of the rectangular cutout portions 25a, 25b, 25c, and 25d is changed in the antenna device 102 according to the second embodiment. As shown in Fig. 13, when 0.001 × k × λ0 ≦ W ≦ 0.200 × k × λ0, isolation between the feed point 23 and the feed point 24 is ensured in a state where the planar antenna conductor 20 having the cutout portions 25a and the like is matched at the resonant frequency f.

[0076] The conditions such as the dimensions of each part (see FIGS. 3 and 4) during the simulation shown in FIG. 13 were the same as those in FIG. 11, except for the notch width W. λ / λ0 in FIG. 13 is the ratio between the wavelength λ0 corresponding to the resonant frequency f0 when there is no notch and the wavelength λ corresponding to the resonant frequency f when the notch width is W. λ / λ0 represents the amount of change in wavelength λ from the wavelength λ0 corresponding to the resonant frequency f0 when there is no notch.

[0077] 14 is a diagram showing an example of a simulation result when the thickness d of the dielectric layer 10 is changed in the antenna device 102 according to the second embodiment having rectangular cutout portions 25a, 25b, 25c, and 25d. As shown in Fig. 14, matching results were obtained at the resonant frequency f of the planar antenna conductor 20 when 0.018 × k × λ0 ≦ d ≦ 0.096 × k × λ0.

[0078] The conditions such as the dimensions of each part (see FIGS. 3 and 4) during the simulation shown in FIG. 14 were the same as those in FIG. 11, except for the thickness d.

[0079] FIG. 15 shows the antenna device 102 according to the second embodiment having rectangular cutouts 25a, 25b, 25c, and 25d, in which the length Ld (=k d 10 is a diagram showing an example of a simulation result of the resonance frequency when the (k) is changed. dis a coefficient representing the magnification, f1 is the first resonance frequency (≈550 MHz), and f2 is the second resonance frequency (≈680 MHz). FIG. 16 shows the relationship between the length Ld (=k d 1 is a diagram showing an example of a simulation result of the wavelength of the resonance frequency when the wavelength λ1 is changed. λ2 is the wavelength of the second resonance frequency. 01 is k d = 2, the wavelength of the first resonance frequency f1, λ 02 is k d is the wavelength of the second resonance frequency f2 when =2.

[0080] As shown in Figure 15, 1.0 ≤ k d 16, the first resonance frequency f1 and the second resonance frequency f2 are stable when 1.0≦k d ≦3.0, λ1 / λ 01 and λ2 / λ 02 In other words, when 2.0×L≦Ld≦6.0×L, the planar antenna conductor 20 can be miniaturized while matching is maintained at the first resonance frequency f1 and the second resonance frequency f2 of the planar antenna conductor 20. d is 1.1≦k d ≦3.0 is preferred, and 1.2≦k d A range of ≦3.0 is more preferred.

[0081] The conditions such as the dimensions of each part (see FIGS. 3 and 4) during the simulation shown in FIGS. 15 and 16 were the same as those in FIG. 11, except for Ld.

[0082] FIG. 17 shows the area ratio (S GND / S ANT 17 is a diagram showing an example of a simulation result of the reflection coefficient S11 when the area SANT With the area S of the ground conductor 30 fixed, GND By changing the area ratio (S GND / S ANT ) is changed. As shown in Figure 17, GND / S ANT Matching was easily achieved at ≥ 0.8.

[0083] The conditions for the dimensions of each part (see Figs. 3 and 4) during the simulation shown in Fig. 17 are as follows: GND 17. λ / λ0 in Fig. 17 is the ratio between the wavelength λ0 corresponding to the resonant frequency f0 when there is no notch and the wavelength λ corresponding to the resonant frequency f when the area of ​​the ground conductor 30 of the antenna device 102 with the notch is changed. λ / λ0 represents the amount of change in wavelength λ from the wavelength λ0 corresponding to the resonant frequency f0 when there is no notch.

[0084] Although the embodiments have been described above, the technology of the present disclosure is not limited to the above-described embodiments, and various modifications and improvements are possible, such as combinations with or substitutions for part or all of other embodiments. The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2020-215715, filed on December 24, 2020, are hereby incorporated by reference as the disclosure of the specification of the present invention. [Explanation of symbols]

[0085] 10 Dielectric Layer 11,12 Main surfaces 14 Dielectric substrate 15 spacer 16 Space 20 Planar antenna conductor 21 Outer Edge 21a, 21b, 21c, 21d Edge 22a,22b,22c,22d corner 23,24 Power supply point 25a, 25b, 25c, 25d Notch 30 Grounding conductor 31 Signal Pattern 32 Dielectric substrate 33,34 Transmission lines 38 Connectors 41, 42, 43, 44 Imaginary lines 50 square areas 51 Outer circumference Areas 51a, 51b, 51c, and 51d 60 feeder line 61 Signal line 62 Grounding part 101, 102, 102A, 102B Antenna device 111,112 regulator 120 Synthesizer 201 Antenna System 301 vehicles 302 Metal part O Origin

Claims

1. a dielectric layer having a first major surface and a second major surface opposite the first major surface; a planar antenna conductor provided on the first principal surface; a ground conductor provided on the second main surface, the shape of the planar antenna conductor is, in a plan view, symmetrical with respect to a first imaginary line and a second imaginary line that are parallel to a part of an outer edge of the planar antenna conductor and perpendicular to each other; When a Cartesian coordinate system having the first virtual line and the second virtual line as its coordinate axes is defined, the planar antenna conductor has corners located at coordinates (+L, +L), (-L, +L), (-L, -L), and (+L, -L), respectively, a first feed point located at coordinates (+a×(1±b), +a×(1±b)), and a second feed point located at coordinates (-a×(1±b), +a×(1±b)); The outer edge is inside a square area with one side measuring 2×L, a satisfies 0.10×L≦a≦0.60×L, b satisfies 0≦b≦0.10, the outer edge is common to a part of the periphery of the square region, the planar antenna conductor has four cutout portions of the same shape that overlap with either the first imaginary line or the second imaginary line in a plan view, The antenna device, wherein the first feed point and the second feed point are located inside the outer edge including the cutout portion.

2. The antenna device according to claim 1 , wherein the dielectric layer includes a spacer having a space therebetween.

3. 3. The antenna device according to claim 1, wherein the planar antenna conductor has a square shape with a side length of 2*L in a plan view.

4. The antenna device according to claim 1 , wherein the shape of the cutout portion is square, rectangular, or trapezoidal.

5. When the notch depth of the notch portion is D and the notch width of the notch portion is W, W and D satisfy the following two formulas: 0.10 x L ≤ W ≤ 0.85 x L 0.14 x L ≤ D ≤ 0.54 x L 5. The antenna device according to claim 1.

6. When the planar antenna conductor has the same shape as the square area, the wavelength of the radio wave in the air at the resonant frequency of the planar antenna conductor is λ ０ When the wavelength shortening rate of the dielectric layer is k, D satisfies the following equation: 0.030×k×λ ０ ≦D≦0.100×k×λ ０ 6. The antenna device according to claim 5.

7. When the planar antenna conductor has the same shape as the square area, the wavelength of the radio wave in the air at the resonant frequency of the planar antenna conductor is λ ０ When the wavelength shortening rate of the dielectric layer is k, W satisfies the following equation: 0.001×k×λ ０ ≦W≦0.200×k×λ ０ 7. The antenna device according to claim 5 or 6.

8. When the planar antenna conductor has the same shape as the square area, the wavelength of the radio wave in the air at the resonant frequency of the planar antenna conductor is λ ０ When the thickness of the dielectric layer is d and the wavelength shortening rate of the dielectric layer is k, d satisfies the following equation: 0.018×k×λ ０ ≦d≦0.096×k×λ ０ 8. An antenna device according to claim 1.

9. The dielectric layer has a square shape with a side length of Ld in a plan view, where Ld satisfies the following formula: 2.0 x L ≤ Ld ≤ 6.0 x L 9. An antenna device according to claim 1.

10. The area of ​​the planar antenna conductor is S ＡＮＴ , the area of ​​the ground conductor is S ＧＮＤ Then, S ＧＮＤ / S ＡＮＴ satisfies the following equation: S ＧＮＤ / S ＡＮＴ ≧0.8 10. An antenna device according to any one of claims 1 to 9.

11. The antenna device according to claim 1 , wherein the signals input to and output from the first feed point and the second feed point are both signals related to radio waves in a predetermined frequency band.

12. The antenna device according to claim 11, wherein the predetermined frequency band is a UHF band or higher.

13. 13. The antenna device according to claim 11, wherein the predetermined frequency band is a band used for terrestrial digital television broadcast waves.

14. When the planar antenna conductor has the same shape as the square region, the wavelength of radio waves in the air at the resonant frequency of the planar antenna conductor is λ0, and the wavelength shortening rate of the dielectric layer is k. The shortest conductive path length between the first feeding point and the second feeding point is k × (λ ０ / 4-λ ０ / 5) or more k×(λ ０ / 4+λ ０ 14. The antenna device according to claim 1, wherein the .lambda.

15. A vehicle antenna system comprising an antenna device described in any one of claims 1 to 14 and a vehicle on which the antenna device is mounted.

16. 16. The vehicle antenna system according to claim 15, wherein the ground conductor is a metal part of the vehicle.

17. 16. The vehicle antenna system according to claim 15, wherein the ground conductor is electrically connected to a metal part of the vehicle.

18. 18. The vehicle antenna system according to claim 16, wherein an outer edge of the metal part is located outside an outer edge of the planar antenna conductor in a plan view.

19. 19. The vehicle antenna system according to claim 15, wherein the planar antenna conductor is substantially perpendicular to a horizontal plane and is positioned outside the vehicle relative to the ground conductor.

Images