Antenna device

Abstract

Provided is an antenna device comprising: a dielectric plate having a first surface provided with a radiation conductor and a second surface opposite to the first surface; a conductive layer provided on the dielectric plate; and a power supply structure for supplying power to the radiation conductor. When λ is the wavelength in air of a radio wave transmitted or received by the radiation conductor and k is the wavelength shortening rate by the dielectric plate, the conductive layer has an inner edge which surrounds the radiation conductor so that a gap exists between the inner edge of the conductive layer and an outer edge of the radiation conductor in a plan view of the dielectric plate, and the inner edge of the conductive layer has a polygonal shape having a length on at least one side of 0.25 × λ or more and 1.75 × λ or less, a circular shape having a diameter of 0.25 × λ or more and 1.75 × λ or less, or an elliptical shape having a long axis or a short axis length of 0.25 × λ or more and 1.75 × λ or less. The sheet resistance of the radiation conductor is equal to or less than the sheet resistance of the conductive layer.

Description

Antenna device

[0001] The present disclosure relates to an antenna device.

[0002] Conventionally, an antenna device has been known that includes a dielectric substrate on which a patch conductor is provided, an electromagnetic coupling conductor that is electromagnetically coupled to the patch conductor, and a transmission conductor that is connected to the electromagnetic coupling conductor and functions as a signal line (see, for example, Patent Document 1).

[0003] WO 2004 / 095639

[0004] A conductive layer may be provided on a dielectric plate on which a radiating conductor such as a patch conductor is provided. Because the conductive layer has low radio wave permeability, it is preferable that the conductive layer be provided so as to surround the radiating conductor in a planar view of the dielectric plate. However, if the conductive layer is provided so as to surround the radiating conductor in a planar view of the dielectric plate, the conductive layer may reduce the directivity of the antenna device (particularly, the directivity in a direction at a relatively low elevation angle with respect to the surface (mounting surface) on which the radiating conductor is provided on the dielectric plate).

[0005] The present disclosure provides an antenna device that can suppress a decrease in directivity when a conductive layer is provided on a dielectric plate on which a radiation conductor is provided.

[0006] A first aspect of the present invention is a dielectric plate having a first surface on which a radiating conductor is provided and a second surface opposite to the first surface, a conductive layer provided on the dielectric plate, and a feeding structure for feeding power to the radiating conductor, wherein, when the wavelength in air of a radio wave transmitted or received by the radiating conductor is λ and the wavelength shortening rate by the dielectric plate is k, the outer edge of the radiating conductor is a polygon with at least one side length of 0.8×k×(λ / 2) to 1.3×k×(λ / 2), a circle with a diameter of 0.8×k×(λ / 2) to 1.3×k×(λ / 2), or an ellipse with a major axis or a minor axis length of 0.8×k×(λ / 2) to 1.3×k×(λ / 2), and the conductive layer has an inner edge surrounding the radiating conductor such that a gap exists between the inner edge and the outer edge in a plan view of the dielectric plate, The antenna device has an inner edge of the conductive layer that is polygonal with at least one side having a length of 0.25×λ or more and 1.75×λ or less, a circle with a diameter of 0.25×λ or more and 1.75×λ or less, or an ellipse with a major axis or a minor axis having a length of 0.25×λ or more and 1.75×λ or less, and the sheet resistance of the radiating conductor is equal to or less than the sheet resistance of the conductive layer.

[0007] A second aspect is the antenna device of the first aspect, wherein the sheet resistance of the radiation conductor may be 0.5 [mΩ / sq] or more and 50 [Ω / sq] or less, 1 [mΩ / sq] or more and 25 [Ω / sq] or less, or 3 [mΩ / sq] or more and 5 [Ω / sq] or less.

[0008] A third aspect is the antenna device of the first or second aspect, wherein the sheet resistance of the conductive layer may be 1 mΩ / sq or more and 200 Ω / sq or less, 3 mΩ / sq or more and 50 Ω / sq or less, or 300 mΩ / sq or more and 25 Ω / sq or less.

[0009] A fourth aspect is an antenna device according to any one of the first to third aspects, further comprising a light-shielding layer formed on the first surface or the second surface, wherein the light-shielding layer may have a portion that overlaps with the outer edge or the inner edge of the dielectric plate in a planar view.

[0010] A fifth aspect is an antenna device according to any one of the first to fourth aspects, wherein the conductive layer includes a first conductive layer provided on the first surface, and the first conductive layer may have a first inner edge that is the inner edge.

[0011] A sixth aspect is an antenna device according to any one of the first to fifth aspects, wherein the conductive layer includes a second conductive layer provided on an inner layer of the dielectric plate, and the second conductive layer may have a second inner edge that is the inner edge.

[0012] A seventh aspect is an antenna device according to any one of the first to sixth aspects, wherein the conductive layer may include a first conductive layer provided on the first surface and a second conductive layer provided on an inner layer of the dielectric plate, the first conductive layer may have a first inner edge which is the inner edge, and the second conductive layer may have a second inner edge which surrounds the first inner edge so that a gap exists between the first inner edge and the second inner edge when viewed in a plane of the dielectric plate.

[0013] An eighth aspect is the antenna device of the seventh aspect, wherein the sheet resistance of the radiation conductor may be lower than the sheet resistances of the first conductive layer and the second conductive layer.

[0014] A ninth aspect is the antenna device according to any one of the first to eighth aspects, wherein the power feeding structure may feed power to the radiation conductor in a non-contact manner.

[0015] A tenth aspect is the antenna device according to any one of the first to ninth aspects, wherein the outer edge of the radiation conductor may have a square shape with a pair of diagonal corners cut out.

[0016] An eleventh aspect is the antenna device according to any one of the first to tenth aspects, wherein the radiation conductor has a void formed in a central portion thereof.

[0017] According to the present disclosure, it is possible to provide an antenna device that can suppress a decrease in directivity when a conductive layer is provided on a dielectric plate on which a radiation conductor is provided.

[0018] FIG. 1 is a partial plan view showing an example of a configuration of an antenna device of a first embodiment. FIG. 2 is a partial cross-sectional view showing an example of a configuration of an antenna device of a second embodiment. FIG. 3 is a partial cross-sectional view showing an example of a configuration of an antenna device of a third embodiment. FIG. 4 is a partial cross-sectional view showing an example of a configuration of an antenna device of a fourth embodiment. FIG. 5 is a partial plan view showing an example of a shape of a radiating conductor. FIG. 6 is a partial plan view showing an example of a shape of a radiating conductor. FIG. 7 is a diagram showing an example of a simulation result of the directivity of the antenna device. FIG. 8 is a diagram showing an example of a simulation result of the directivity of the antenna device. FIG. 9 is a diagram showing an example of a simulation result of the directivity of the antenna device. FIG. 10 is a diagram showing an example of a simulation result of the directivity of the antenna device.

[0019] The present embodiment will be described below with reference to the drawings. For ease of understanding, the scales of the various components in the drawings may differ from the actual scale. Directions such as parallel, right-angled, orthogonal, horizontal, vertical, up, down, left, and right, as well as terms such as identical and equal, are permitted to deviate to the extent that they do not impair the functions and effects of the embodiment. The shape of corners is not limited to right angles and may be rounded like an arch. Overlapping may also mean partially overlapping. 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.

[0020] The antenna device of the present embodiment is applicable to, for example, a Global Navigation Satellite System (GNSS), a Vehicle to Everything (V2X) communication system, a fifth-generation mobile communication system (so-called 5G), an in-vehicle radar system, etc. However, applicable systems are not limited to these.

[0021] GNSS (Global Navigation Satellite System) is a general term for satellite positioning systems such as GPS in the United States, Quasi-Zenith Satellite System (QZSS) in Japan, GLONASS in Russia, Galileo in Europe, BeiDou in China, and NAVIC in India. The antenna device of this embodiment is not limited to use with GNSS, but is also suitable for Satellite Digital Audio Radio Service (SDARS) or low-earth-orbit satellite communications.

[0022] An example of a V2X communication system is an ETC system. The antenna device of this embodiment is suitable for use in the frequency band of 6 GHz or less (sub6) among the frequency bands used in 5G, and may be used for transmitting and receiving (one or both of transmitting and receiving) radio waves in the 5.8 GHz band or 5.9 GHz band, for example. However, the antenna device of this embodiment is not limited to the frequency band used in 5G (3.3 GHz or more), and can also be used for 4G LTE, millimeter wave bands (30 GHz to 300 GHz), and microwaves.

[0023] Fig. 1 is a partial plan view showing an example of the configuration of an antenna device according to a first embodiment. Fig. 1 is a plan view of a dielectric plate 10. Fig. 2 is a partial cross-sectional view showing an example of the configuration of the antenna device according to the first embodiment. The antenna device 101 shown in Figs. 1 and 2 includes a dielectric plate 10 provided with a conductive layer 30, a radiation conductor 20 that transmits or receives radio waves A through the dielectric plate 10, and a feed structure 40 that feeds the radiation conductor 20. Note that the feed structure 40 is omitted from Fig. 1 to ensure visibility.

[0024] The dielectric plate 10 is, for example, a window glass for a vehicle. Examples of the window glass for a vehicle include a roof glass attached to the ceiling of the vehicle, a windshield attached to the front of the vehicle, a rear glass attached to the rear of the vehicle, and a side glass attached to the side of the vehicle. The window glass for a vehicle is not limited to these, and may be, for example, a window glass in which the roof glass is integrated with one or both of the windshield and the rear glass.

[0025] The dielectric plate 10 may be a plate other than a glass plate (for example, a resin plate).

[0026] The dielectric plate 10 is a plate-shaped dielectric having a principal surface 11 facing in the negative Z-axis direction and a principal surface 12 facing in the opposite direction (positive Z-axis direction) to the principal surface 11. While the principal surfaces 11 and 12 are illustrated parallel to the XY plane, the principal surface 11 or 12 may be curved relative to the XY plane. When the principal surface 11 or 12 is curved relative to the XY plane, i.e., when the dielectric plate 10 has a curved shape, the dielectric plate 10 may have a single curved shape curved in only one of the left-right or up-down directions, or a compound curved shape curved in both the left-right and up-down directions. When the dielectric plate 10 has a curved shape, the radius of curvature may be 2000 to 11000 mm. When the dielectric plate 10 is a glass plate, gravity forming, press forming, roller forming, or the like is used to bend the dielectric plate 10. The principal surface 11 is an example of a first surface on which a radiation conductor is provided. The main surface 12 is an example of a second surface opposite to the first surface.

[0027] When the dielectric plate 10 is a window glass for a vehicle, for example, the main surface 11 is the surface of the window glass facing the inside of the vehicle, and the main surface 12 is the surface of the window glass facing the outside of the vehicle.

[0028] The dielectric plate 10 is, for example, a single-pane window glass, which is a window glass made up of only one glass plate.

[0029] The thickness of the glass plate (dielectric plate 10 in the example of FIG. 2) in the single plate in the Z-axis direction is not particularly limited, but can generally be selected appropriately in the range of 0.5 mm to 10 mm. The thickness of the dielectric plate 10 is preferably 0.5 mm or more, more preferably 0.7 mm or more, even more preferably 1.1 mm or more, and particularly preferably 1.6 mm or more. Furthermore, to prevent the mass from becoming too large, the thickness of the dielectric plate 10 is preferably 7 mm or less, more preferably 5 mm or less, and even more preferably 4 mm or less.

[0030] Furthermore, when the dielectric plate 10 is a laminated glass as described below, the thickness of the dielectric plate 10 in the Z-axis direction is not particularly limited and can be appropriately selected from the range of 0.1 mm to 10 mm. The thickness of the dielectric plate 10 is preferably 0.3 mm or more, more preferably 0.5 mm or more, even more preferably 0.7 mm or more, particularly preferably 1.1 mm or more, and most preferably 1.6 mm or more. Furthermore, to prevent the mass of the laminated glass from becoming too large, the thickness of the dielectric plate 10 is preferably 3.0 mm or less, more preferably 2.6 mm or less, and even more preferably 2.1 mm or less. The thicknesses of the multiple glass plates constituting the dielectric plate 10 may be the same or different.

[0031] When the dielectric plate 10 is a glass plate, the relative dielectric constant of the dielectric plate 10 is 3.7 or more and 10 or less, and the wavelength shortening factor k of the dielectric plate 10 is 0.316 or more and 0.52.

[0032] The conductive layer 30 is provided on the dielectric plate 10. In the example shown in Fig. 2, the conductive layer 30 is provided on the main surface 11 of the dielectric plate 10. The conductive layer 30 may be provided directly on the main surface 11 so as to be in contact with the main surface 11, or may be provided indirectly on the main surface 11 so as to have a predetermined intermediate member interposed between the conductive layer 30 and the main surface 11.

[0033] The conductive layer 30 is a planar conductor disposed on the main surface 11 side of the dielectric plate 10. The conductive layer 30 may be a conductor in contact with the main surface 11, or may be a conductor disposed on the main surface 11 side via a transparent or translucent dielectric (not shown). The conductive layer 30 may be transparent or translucent. Specific examples of the conductive layer 30 include a metal film such as an Ag (silver) film, a metal oxide film such as an ITO (indium tin oxide) film, a resin film containing conductive particles, and a laminate of multiple types of films. The conductive layer 30 may be a resin film such as polyethylene terephthalate coated by vapor deposition or the like. The conductive layer 30 may also be a film formed into a mesh shape by conductive ink or etching.

[0034] The conductive layer 30 may be a conductive film coated on the main surface 11 of the dielectric plate 10. A specific example of the conductive film is a low-emissivity film such as a Low-E (Low Emissivity) film that exhibits low radiation performance.

[0035] Low emissivity refers to reducing heat transfer due to radiation. Low emissivity films such as Low-E films ensure thermal insulation by suppressing heat transfer due to radiation. The low emissivity film may be a general film, for example, a laminated film including a transparent dielectric film, an infrared reflective film, and a transparent dielectric film in this order. Typical transparent dielectric films are metal oxides and metal nitrides. Typical metal oxides are zinc oxide and tin oxide. Typical infrared reflective films are metal films. Typical metal films are silver (Ag). Here, one or more infrared reflective films may be formed between the transparent dielectric films.

[0036] Furthermore, the conductive layer 30 is not limited to a low-emissivity film such as a Low-E film, and may have other functions as long as it is a conductive layer. For example, the conductive layer 30 may have a function of preventing icing or fogging of the dielectric plate 10 such as window glass by generating heat when a voltage is applied.

[0037] The conductive layer 30 may be a conductive film included in a light-controlling film that can actively change the visible light transmittance of the dielectric plate 10 by applying an AC voltage. The light-controlling film has, for example, a molecular layer with optical anisotropy between a pair of opposing resin substrates. A conductive film and an electrode electrically connected to the conductive film are provided on the main surface of each resin substrate. The light-controlling film can be driven by applying a voltage between the pair of conductive layers via the electrodes.

[0038] The resin substrate is made of, for example, a transparent resin. The resin substrate may have, for example, polyethylene terephthalate (PET), polycarbonate (PC), or cycloolefin polymer (COP). Furthermore, a pair of opposing resin substrates may be made of, for example, a combination of the above-mentioned resins. The thickness of the resin substrate is, for example, in the range of 5 μm to 500 μm, preferably in the range of 10 μm to 200 μm, more preferably in the range of 20 μm to 180 μm, and even more preferably in the range of 50 μm to 150 μm.

[0039] The conductive film may include, for example, a transparent conductive oxide, a transparent conductive polymer, a laminated film of a metal layer and a dielectric layer, silver nanowires, a silver or copper metal mesh, etc. The thickness of the conductive film may be, for example, in the range of 5 nm to 2 μm.

[0040] Examples of molecules having optical anisotropy include liquid crystals. That is, for example, a liquid crystal layer may be used as a molecular layer having optical anisotropy. Examples of the liquid crystal layer include polymer dispersed liquid crystal (PDLC), polymer network liquid crystal (PNLC), and guest-host liquid crystal. Alternatively, iodine or the like may be used as a molecule having optical anisotropy. The light control film may have a suspended particle device (SPD) including such a molecular layer.

[0041] The radiating conductor 20 is provided on the main surface 11 of the dielectric plate 10. The radiating conductor 20 may be provided directly on the main surface 11 so as to be in contact with the main surface 11, or may be provided indirectly on the main surface 11 so as to have a predetermined intermediate member interposed between the radiating conductor 20 and the main surface 11.

[0042] The radiating conductor 20 is a planar conductor arranged on the principal surface 11 side of the dielectric plate 10. The radiating conductor 20 may be a conductor in contact with the principal surface 11, or may be a conductor arranged on the principal surface 11 side via a transparent or translucent dielectric (not shown). The radiating conductor 20 may be transparent or translucent. Specific examples of the radiating conductor 20 include a conductor formed by applying and firing a silver paste containing silver powder and glass frit onto the dielectric plate 10, a metal film such as an Ag (silver) film, a metal oxide film such as an ITO (indium tin oxide) film, a resin film containing conductive particles, or a laminate formed by stacking multiple types of films including a conductive film. The radiating conductor 20 may be formed by coating a resin film such as polyethylene terephthalate with a vapor deposition process or the like. The radiating conductor 20 may be formed by applying conductive ink or etching to a film to form a mesh shape. The radiating conductor 20 may be a conductive film coated on the principal surface 11 of the dielectric plate 10.

[0043] The radiating conductor 20 is, for example, a flat pattern formed of a conductor on the main surface 11. The shape of the radiating conductor 20 in a plan view is not limited to a rectangle, and may be other shapes (for example, a polygon other than a rectangle, a circle, an ellipse, etc.). The rectangle, polygon, circle, and ellipse may include an approximate rectangle, an approximate polygon, an approximate circle, and an approximate ellipse, respectively.

[0044] The radiation conductor 20 is a radiation element that transmits or receives radio waves A having a frequency included in a predetermined frequency band W through the dielectric plate 10. The radiation conductor 20 is also called a patch conductor.

[0045] The frequency band W is a relatively high band such as the UHF (Ultra High Frequency) band of 300 MHz to 3 GHz, the SHF (Super High Frequency) band of 3 GHz to 30 GHz, or the EHF (Extremely High Frequency) band of 30 GHz to 300 GHz. Specific examples of such high frequency bands include bands used in the fifth generation communication (5G) standard (frequency bands of 6 GHz or less (sub6) and frequency bands of 24 GHz or more (28 GHz band, 39 GHz band, etc.)).

[0046] The power feeding structure 40 feeds power to the radiation conductor 20. In the example shown in Fig. 2, the power feeding structure 40 feeds power to the radiation conductor 20 in a non-contact manner by electromagnetic coupling or the like. Non-contact power feeding improves attachment ease and durability against vibrations, etc. The power feeding structure 40 may also feed power to the radiation conductor 20 in a contact manner.

[0047] The feeding structure 40 is disposed on the main surface 11 side of the dielectric plate 10, and at least a portion of the feeding structure 40 overlaps with the radiation conductor 20 in a plan view. The feeding structure 40 includes, for example, a substrate 41 and a feeding conductor 47.

[0048] The substrate 41 is a plate-shaped dielectric having a substrate surface 42 facing in the negative Z-axis direction and a substrate surface 43 facing in the opposite direction (positive Z-axis direction) to the substrate surface 42. The substrate surface 43 faces the main surface 11. Although the substrate surfaces 42 and 43 are illustrated as being parallel to the XY plane, the substrate surface 42 or the substrate surface 43 may be curved with respect to the XY plane.

[0049] A signal line 45 is formed on the substrate surface 42, and a ground conductor 44 is formed on the substrate surface 43. The signal line 45 faces the ground conductor 44 across the dielectric substrate 41, forming a transmission line. Semiconductor components 46, such as an amplifier that amplifies a signal transmitted through the signal line 45, are mounted on the substrate surface 42.

[0050] The power supply conductor 47 is a power supply element that supplies power to the radiation conductor 20 in a non-contact manner. The power supply conductor 47 is, for example, electromagnetically coupled to the radiation conductor 20, and supplies power to the radiation conductor 20 in a non-contact manner through electromagnetic coupling. The power supply conductor 47 is electrically connected to one end of the signal line 45. The power supply conductor 47 is not connected to the ground conductor 44 in a DC manner.

[0051] The power supply conductor 47 has, for example, a portion that faces the radiation conductor 20 in the Z-axis direction. In the example shown in FIG. 2 , the power supply conductor 47 includes an L-shaped conductor portion having a vertical portion 48 and a parallel portion 49. The vertical portion 48 is fixed to the substrate 41 while penetrating the substrate 41. The vertical portion 48 extends in the positive Z-axis direction from the substrate surface 43. One end of the parallel portion 49 is connected to the end of the vertical portion 48 in the positive Z-axis direction. The parallel portion 49 extends parallel to the ground conductor 44 and the radiation conductor 20. The parallel portion 49 is spaced apart from the ground conductor 44 in the positive Z-axis direction and from the radiation conductor 20 in the negative Z-axis direction.

[0052] A dielectric layer 110 is present between the feeding structure 40 and the main surface 11. The dielectric layer 110 may be air or a solid dielectric. The feeding structure 40 is fixed relative to the main surface 11 so that the dielectric layer 110 is present between the feeding structure 40 and the main surface 11.

[0053] The conductive layer 30 has an inner edge 31 that surrounds the radiating conductor 20 so that a gap exists between the inner edge 31 and the outer edge 21 of the radiating conductor 20 in a plan view of the dielectric plate 10. A gap length a indicates the length of the gap in a plan view of the dielectric plate 10. The inner edge 31 forms an opening 32 (see FIG. 1 ) that surrounds the radiating conductor 20 in a plan view. The opening 32 functions as a window through which radio waves A transmitted or received by the radiating conductor 20 pass.

[0054] The inner edge 31 is formed so as to surround the radiation conductor 20 in plan view. In the example shown in Fig. 1 , the inner edge 31 forms an opening 32 that is completely closed by the conductive layer 30 in plan view. However, by cutting out a portion of the inner edge 31, the opening 32 does not have to be completely closed by the conductive layer 30 in plan view.

[0055] The conductive layer 30 in the first embodiment is an example of a first conductive layer provided on the first surface on which the radiation conductor is provided. The inner edge 31 is an example of a first inner edge that is the inner edge of the first conductive layer.

[0056] Here, the wavelength in air of radio wave A transmitted or received by the radiating conductor 20 is defined as λ, and the wavelength shortening rate due to the dielectric plate 10 is defined as k. The outer edge 21 of the radiating conductor 20 is a polygon with at least one side having a length of 0.8×k×(λ / 2) to 1.3×k×(λ / 2), a circle with a diameter of 0.8×k×(λ / 2) to 1.3×k×(λ / 2), or an ellipse with a major or minor axis having a length of 0.8×k×(λ / 2) to 1.3×k×(λ / 2). Hereinafter, this dimensional and shape condition is defined as "Condition C." Furthermore, the length of one side, the diameter, or the length of the major or minor axis of the shape of the outer edge 21 is defined as "length c." Figure 1 illustrates an example in which the outer edge 21 is square, satisfying Condition C.

[0057] When the outer edge 21 satisfies condition C, the radiation conductor 20 is formed to have a length c whose median is k × (λ / 2), and the radiation conductor 20 functions as a radiation element of the patch antenna. Therefore, the antenna gain of the antenna device 101 that transmits or receives radio waves A with wavelength λ is improved compared to when condition C is not satisfied.

[0058] The condition C, "0.8×k×(λ / 2) or more and 1.3×k×(λ / 2) or less," is preferably "0.8×k×(λ / 2) or more and 1.2×k×(λ / 2) or less," more preferably "0.9×k×(λ / 2) or more and 1.1×k×(λ / 2) or less," and even more preferably "0.95×k×(λ / 2) or more and 1.05×k×(λ / 2) or less."

[0059] Meanwhile, the inner edge 31 of the conductive layer 30 is a polygon with at least one side length of 0.25×λ to 1.75×λ, a circle with a diameter of 0.25×λ to 1.75×λ, or an ellipse with a major axis or a minor axis length of 0.25×λ to 1.75×λ. Hereinafter, this dimensional shape condition will also be referred to as "Condition D." Furthermore, with regard to the shape of the inner edge 31, the length of one side, the diameter, or the length of the major axis or the minor axis is defined as "length d." Figure 1 illustrates an example where the inner edge 31 that satisfies Condition D is a square.

[0060] When the inner edge 31 satisfies condition D, the opening 32 functions as a radio wave transmission window having a length d whose median value is (1 × λ). When the inner edge 31 satisfies condition D, as in the simulation example described below, the directivity of the antenna device 101 (particularly the directivity in a direction at a relatively low elevation angle with respect to the main surface 11 (mounting surface) on which the radiation conductor 20 is provided) is improved compared to when condition D is not satisfied. This is because when the inner edge 31 satisfies condition D, the effect of the inner edge 31 of the conductive layer 30 on the radio waves A is reduced compared to when condition D is not satisfied.

[0061] The condition D, "0.25×λ or more and 1.75×λ or less," is preferably "0.5×λ or more and 1.5×λ or less," and more preferably "0.8×λ or more and 1.2λ or less," in terms of improving antenna gain.

[0062] The gap length a between the outer edge 21 of the radiating conductor 20 and the inner edge 31 of the conductive layer 30 may be equal to or greater than {0.25×λ−0.8×k×(λ / 2)} / 2 and equal to or less than {1.75×λ−1.2×k×(λ / 2)} / 2, thereby improving the directivity of the antenna device 101 (particularly, the directivity in a direction at a relatively low elevation angle with respect to the principal surface 11 (mounting surface) on which the radiating conductor 20 is provided).

[0063] The sheet resistance of the radiating conductor 20 (hereinafter also referred to as "sheet resistance R20") is preferably low to improve the radiation efficiency of the antenna, and is preferably lower than the sheet resistance (hereinafter also referred to as "sheet resistance R30") of the conductive layer 30. This improves the radiation characteristics of the radiating conductor 20, and improves the directivity of the antenna device 101 (particularly, the directivity in a direction at a relatively low angle of elevation with respect to the main surface 11).

[0064] The sheet resistance R20 is desirably as low as possible in terms of antenna radiation efficiency, and is, for example, 0.5 mΩ / sq to 50 mΩ / sq, preferably 1 mΩ / sq to 25 mΩ / sq, and more preferably 3 mΩ / sq to 5 mΩ / sq. The sheet resistance R30 is, for example, 1 mΩ / sq to 200 mΩ / sq, preferably 3 mΩ / sq to 50 mΩ / sq, and more preferably 300 mΩ / sq to 25 mΩ / sq.

[0065] 3 is a partial cross-sectional view showing an example of the configuration of an antenna device according to the second embodiment. In the second embodiment, the description of the configuration, operation, and effects similar to those of the above-described embodiments will be omitted by referencing the above description. The antenna device 102 shown in FIG. 3 differs from the above-described antenna device 101 in that it includes a light-shielding layer 50.

[0066] 3, the antenna device 102 includes a light-shielding layer 50 formed on the main surface 11. The light-shielding layer 50 has a portion that overlaps with the outer edge 21 or the inner edge 31 of the dielectric plate 10 in a planar view. As a result, the outer edge 21 or the inner edge 31 overlaps with the light-shielding layer 50 in a planar view, making the outer edge 21 or the inner edge 31 less noticeable. Furthermore, at least a portion of the opening 32 also overlaps with the light-shielding layer 50 in a planar view, making the opening 32 less noticeable. This improves the appearance of the antenna device and also the appearance of the window glass as a whole.

[0067] The light-shielding layer 50 is a layer that blocks visible light. When the dielectric plate 10 is a laminated glass, the light-shielding layer 50 may be formed on the inner main surfaces of the multiple glass plates that make up the laminated glass.

[0068] The light-shielding layer 50 is, for example, an opaque colored ceramic layer having a thickness of approximately 5 μm to 25 μm. The color of the light-shielding layer 50 is arbitrary, but a dark color such as black, brown, gray, or dark blue, or white is preferable, and black is more preferable. The light-shielding layer 50 is formed by applying a ceramic paste containing a dark color such as black, brown, gray, or dark blue, or white pigment, and glass frit, onto the dielectric plate 10 and firing the paste.

[0069] 4 is a partial cross-sectional view showing an example of the configuration of an antenna device according to the third embodiment. In the third embodiment, the same configuration, operation, and effects as those of the above-described embodiments will not be described again by citing the above description. The antenna device 103 shown in FIG. 4 differs from the antenna device 102 in that the conductive layer 30 is provided as an inner layer of the dielectric plate 10.

[0070] The dielectric plate 10 is, for example, a laminated glass for a vehicle. The dielectric plate 10 includes a glass plate 80, a glass plate 90, and an interlayer film 120. In the example shown in Fig. 4, the dielectric plate 10 is a laminated glass in which the glass plate 80 disposed on the inside of the vehicle and the glass plate 90 disposed on the outside of the vehicle are bonded together via the interlayer film 120. The interlayer film 120 is sandwiched between the glass plate 80 and the glass plate 90.

[0071] The glass plate 80 and the glass plate 90 are transparent plate-shaped dielectric plates. One or both of the glass plate 80 and the glass plate 90 may be translucent. The glass plate 80 is an example of a first dielectric plate, and the glass plate 90 is an example of a second dielectric plate.

[0072] Glass plate 80 has a main surface 81 facing in the negative Z-axis direction and a main surface 82 facing in the opposite direction (positive Z-axis direction) from main surface 81. Main surface 81 is an example of a first main surface. Glass plate 90 has a main surface 91 facing in the negative Z-axis direction and a main surface 92 facing in the opposite direction (positive Z-axis direction) from main surface 91. Main surface 92 is an example of a second main surface.

[0073] The interlayer film 120 is a dielectric film disposed between the main surface 82 of the glass plate 80 and the main surface 91 of the glass plate 90. The interlayer film 120 is a transparent or semi-transparent dielectric material interposed between the glass plate 80 and the glass plate 90. The glass plate 80 and the glass plate 90 are bonded together by the interlayer film 120. Examples of the interlayer film 120 include thermoplastic polyvinyl butyral (PVB), ethylene vinyl acetate copolymer (EVA), and cycloolefin polymer (COP). The relative dielectric constant of the interlayer film 120 is preferably 2.4 or more and 3.5 or less.

[0074] The conductive layer 30 in the third embodiment is an example of a second conductive layer provided on the inner layer of the dielectric plate. The inner edge 31 is an example of a second inner edge that is the inner edge of the second conductive layer. In the example shown in FIG. 4 , the conductive layer 30 is provided on the main surface 91. However, the conductive layer 30 may also be provided on the main surface 82.

[0075] Fig. 5 is a partial cross-sectional view showing an example of the configuration of an antenna device according to a fourth embodiment. In the fourth embodiment, the description of the configuration, operation, and effects similar to those of the above-described embodiments will be omitted by incorporating the above description. The antenna device 104 shown in Fig. 5 differs from the antenna device 102 or 103 in that the conductive layer 30 includes multiple conductive layers (two conductive layers 60 and 70 in this example).

[0076] The conductive layer 60 in the fourth embodiment is an example of a first conductive layer provided on the first surface on which the radiation conductor is provided. The inner edge 61 is an example of a first inner edge that is the inner edge of the first conductive layer. The conductive layer 70 in the fourth embodiment is an example of a second conductive layer provided on the inner layer of the dielectric plate. The inner edge 71 is an example of a second inner edge that is the inner edge of the second conductive layer.

[0077] The conductive layer 30 includes a conductive layer 60 provided on the principal surface 11 (principal surface 81) and a conductive layer 70 provided on an inner layer of the dielectric plate 10. The conductive layer 60 has an inner edge 61 that satisfies the above-mentioned condition D. The conductive layer 70 has an inner edge 71 that surrounds the inner edge 61 so that a gap exists between the inner edge 61 and the conductive layer 70 in a planar view of the dielectric plate 10. The gap length e indicates the length of the gap in a planar view of the dielectric plate 10. The inner edges 61, 71 form an opening 32 (see FIG. 1 ) that surrounds the radiating conductor 20 in a planar view. The opening 32 functions as a window through which radio waves A transmitted or received by the radiating conductor 20 pass.

[0078] In plan view, the inner edge 71 is located outside the inner edge 61 in the direction along the XY plane. This causes the influence of the inner edge 61 of the conductive layer 60 on the radio wave A to become dominant, and reduces the influence of the inner edge 71 of the conductive layer 70. Therefore, the directivity of the antenna device 104 (particularly, the directivity in a direction at a relatively low elevation angle with respect to the main surface 11 (mounting surface) on which the radiation conductor 20 is provided) is improved compared to when the inner edge 71 is located inside the inner edge 61 in plan view.

[0079] The sheet resistance R20 of the radiating conductor 20 is preferably low to improve the radiation efficiency as an antenna, and is preferably lower than the sheet resistances of the conductive layer 60 (hereinafter also referred to as "sheet resistance R60") and the conductive layer 70 (hereinafter also referred to as "sheet resistance R70"). This improves the radiation characteristics of the radiating conductor 20, and improves the directivity of the antenna device 104 (particularly, the directivity in a direction at a relatively low angle of elevation with respect to the main surface 11).

[0080] The sheet resistance R60 is, for example, 1 mΩ / sq or more and 200 Ω / sq or less, preferably 3 mΩ / sq or more and 50 Ω / sq or less, and more preferably 300 mΩ / sq or more and 25 Ω / sq or less. The sheet resistance R70 is, for example, 1 mΩ / sq or more and 200 Ω / sq or less, preferably 3 mΩ / sq or more and 50 Ω / sq or less, and more preferably 300 mΩ / sq or more and 25 Ω / sq or less. However, the sheet resistance R70 of the conductive layer 70 may be lower than the sheet resistance R60 of the conductive layer 60.

[0081] Fig. 6 is a partial plan view showing an example of the shape of the radiating conductor. The outer edge 21 of the radiating conductor 20 is a square with one pair of diagonal corners cut out. In order to improve the circular polarization characteristics of the antenna device (radiating conductor 20), it is preferable to provide a notch 23 in the radiating conductor 20. However, this is not limited to this, and the radiating conductor 20 does not necessarily have to have the notch 23. In the example shown in Fig. 6, the shape of the notch 23 is a right-angled isosceles triangle or a substantially right-angled isosceles triangle, but the shape of the notch 23 is not limited to this.

[0082] The radiation conductor 20 has a void 22 formed in the center. The void 22 is a portion where no conductor is provided. The presence of the void 22 allows the radiation conductor 20 to be made smaller than when the void 22 is not present, and also reduces distortion caused by differences in heat distribution when the radiation conductor 20 is formed by coating and firing silver paste by screen printing or the like. The shape of the void 22 is not limited to a square, and may be a polygon other than a square, a circle, an ellipse, or the like.

[0083] Fig. 7 is a partial plan view showing an example of the shape of the radiating conductor. The outer edge 21 of the radiating conductor 20 is circular or elliptical with a pair of diagonal corners cut out. In order to improve the circular polarization characteristics of the antenna device (radiating conductor 20), it is preferable to provide a cutout 23 in the radiating conductor 20. In the example shown in Fig. 7, the inner edge 31 of the conductive layer 30 is circular.

[0084] The shape of the outer edge 21 is a polygon, a circle, or an ellipse, and the shape of the inner edge 31 is also a polygon, a circle, or an ellipse. Any shapes may be combined for the outer edge 21 and the inner edge 31. For example, the shape of the outer edge 21 may be a polygon and the shape of the inner edge 31 may be a circle, or the shape of the outer edge 21 may be a circle and the shape of the inner edge 31 may be a polygon.

[0085] Fig. 8 is a diagram showing an example of a simulation result of the directivity of the antenna device when the size of the opening 32 is changed by changing the length d. Fig. 8 shows a simulation example of the antenna device 101 (Fig. 2) including the radiating conductor 20 having the shape shown in Fig. 6, in which the radiating conductor 20 and the conductive layer 30 are both perfect conductors (with zero sheet resistance).

[0086] Fig. 9 is a diagram showing an example of a simulation result of the directivity of an antenna device when the size of the opening 32 is changed by changing the length d. Fig. 9 shows a simulation example of the antenna device 101 (Fig. 2) including the radiating conductor 20 having the shape shown in Fig. 6, where the sheet resistance of the radiating conductor 20 is 1.0 [mΩ / sq], which corresponds to the sheet resistance of copper foil, and the sheet resistance of the conductive layer 30 is 15 [Ω / sq]. Note that when the sheet resistance of the radiating conductor 20 is 4.0 [mΩ / sq], which corresponds to the sheet resistance of a conductor formed by screen printing and firing silver paste, results similar to those shown in Fig. 9 were obtained.

[0087] Fig. 10 is a diagram showing an example of a simulation result of the directivity of the antenna device when the size of the opening 32 is changed by changing the length d. Fig. 10 shows a simulation example of the antenna device 101 (Fig. 2) including the radiating conductor 20 having the shape shown in Fig. 7, in which the sheet resistance of the radiating conductor 20 is set to 4.0 [mΩ / sq], which corresponds to the sheet resistance of a conductor formed by screen printing and firing silver paste, and the conductive layer 30 is set to a perfect conductor.

[0088] In Figures 8, 9, and 10, "Phi = 0.0" indicates directivity in the ZX plane. "Phi = 90" indicates directivity in the YZ plane. The shape of the inner edge 31 in Figures 8 and 9 is a square with a side length of d. The shape of the inner edge 31 in Figure 10 is a circle with a diameter of d. Here, the length d is defined as nmlz_f x λg, and is a value normalized by the wavelength λg. λg is the wavelength λ of a radio wave with a frequency f of 2.3325 GHz. "nmlz_f = 0.5," "nmlz_f = 1.0," and "nmlz_f = 1.5" satisfy the above condition D. "nmlz_f = 2.0" does not satisfy the above condition D.

[0089] 8, 9, and 10, when condition D is satisfied, the directivity of the antenna device is improved compared to when condition D is not satisfied. In particular, the directivity in directions at relatively low elevation angles relative to the main surface 11 (mounting surface) is improved compared to when condition D is not satisfied. When the normal direction to the main surface 11 is set to 0°, not only the directivity in the normal direction to the main surface 11 but also the directivity in the low elevation angle ranges of 40° to 70° and 290° to 320° is improved.

[0090] 8, 9 and 10 were as follows: Dielectric plate 10: laminated glass (interlayer 120, glass plate 80, and glass plate 90) Thickness of glass plate 80: 2 mm Thickness of glass plate 90: 2 mm Thickness of interlayer 120: 0.76 mm Material of interlayer 120: PVB Material of substrate 41: FR-4 Thickness of substrate 41: 0.8 mm Thickness of dielectric layer 110: 3.6 mm Adhesive layer between power supply structure 40 and main surface 11: acrylic foam tape Thickness of adhesive layer between power supply structure 40 and main surface 11: 0.8 mm Ground conductor 44: square, 55 mm long and 55 mm wide Length c of radiating conductor 20: 26.15 mm Length h of notch 23: 5.5 mm Length g of void 22: 8 mm Length s of power supply conductor 47: 14.4 mm

[0091] Fig. 11 is a diagram showing an example of a simulation result of the directivity of the antenna device when the size of the aperture 32 is changed by changing the length c from 0.7 × k × (λ / 2) to 1.4 × k × (λ / 2) or less. Fig. 11 shows an example of a simulation of the antenna device 101 (Fig. 2) including the radiating conductor 20 having the shape shown in Fig. 6, where the sheet resistance of the radiating conductor 20 is 1.0 [mΩ / sq], which corresponds to the sheet resistance of copper foil, and the sheet resistance of the conductive layer 30 is 15 [Ω / sq].

[0092] In FIG. 11 , "Phi = 0.0" indicates directivity in the ZX plane. "Phi = 90" indicates directivity in the YZ plane. The shape of the inner edge 31 in FIG. 11 is a square with a side length of d. Here, the length d is 130 mm, the frequency f of the radio wave is 2.3325 GHz (wavelength λ = 128.6 mm), the dielectric plate 10 is glass with a relative dielectric constant of 7, and the wavelength shortening rate k is 0.378. When the length c is "0.7 × k × (λ / 2)" or "1.4 × k × (λ / 2)," the above condition C is not satisfied, but when the length c is other than these, the above condition C is satisfied.

[0093] 11 , when condition C is satisfied, the directivity of the antenna device is improved compared to when condition C is not satisfied. In particular, the directivity in directions at relatively low elevation angles relative to the main surface 11 (mounting surface) is improved compared to when condition C is not satisfied. When the normal direction to the main surface 11 is set to 0°, not only the directivity in the normal direction to the main surface 11 but also the directivity in the low elevation angle ranges of 40° to 70° and 290° to 320° is improved.

[0094] The conditions such as the dimensions of each part in FIG. 11 are the same as those in the cases of FIGS. 8 and 9.

[0095] 12 is a diagram showing an example of a simulation result of an antenna device when the magnitude relationship between the sheet resistances of the radiating conductor 20 and the conductive layer 30 is changed. FIG. 12 shows an example of a simulation of the antenna device 101 ( FIG. 2 ) including the radiating conductor 20 having the shape shown in FIG. 6 . “Conductive layer 15Ω / radiating conductor Copper” indicates an example in which the sheet resistance of the radiating conductor 20 is 1.0 mΩ / sq, which corresponds to the sheet resistance of copper foil, and the sheet resistance of the conductive layer 30 is 15 Ω / sq (in which the sheet resistance of the radiating conductor 20 is lower than that of the conductive layer 30). “Conductive layer 15Ω / radiating conductor 16Ω” indicates a comparative example in which the sheet resistance of the radiating conductor 20 is 16 Ω / sq, and the sheet resistance of the conductive layer 30 is 15 Ω / sq (in which the sheet resistance of the radiating conductor 20 is higher than that of the conductive layer 30).

[0096] In Fig. 12, "Phi = 0.0" indicates directivity in the ZX plane. "Phi = 90" indicates directivity in the YZ plane. The shape of the inner edge 31 in Fig. 12 is a square with a length d of one side. Here, the length d is set to 130 mm, the frequency f of the radio wave is set to 2.3325 GHz (wavelength λ = 128.6 mm), the dielectric plate 10 is made of glass with a relative dielectric constant of 7, and the wavelength shortening rate k is set to 0.378.

[0097] As shown in Figure 12, in the embodiment where the sheet resistance of the radiating conductor 20 is lower than the sheet resistance of the conductive layer 30, the antenna gain of the antenna device is improved overall compared to the comparative example where the sheet resistance of the radiating conductor 20 is higher than the sheet resistance of the conductive layer 30.

[0098] The conditions such as the dimensions of each part in FIG. 12 are the same as those in the cases of FIGS. 8 and 9.

[0099] Although the embodiments have been described above, they are presented as examples and the present invention is not limited to the above embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims.

[0100] This international application claims priority based on Japanese Patent Application No. 2023-137890, filed on August 28, 2023, the entire contents of which are incorporated herein by reference.

[0101] REFERENCE SIGNS LIST 10 Dielectric plate 11, 12 Main surface 20 Radiating conductor 21 Outer edge 22 Void 23 Notch 30 Conductive layer 31 Inner edge 32 Opening 40 Power supply structure 41 Substrate 42, 43 Substrate surface 44 Ground conductor 45 Signal line 46 Semiconductor component 47 Power supply conductor 48 Vertical portion 49 Parallel portion 50 Light-shielding layer 60 Conductive layer 61 Inner edge 70 Conductive layer 71 Inner edge 80, 90 Glass plate 101, 102, 103, 104 Antenna device 110 Dielectric layer 120 Interlayer

Claims

1. A dielectric plate having a first surface on which a radiating conductor is provided and a second surface opposite to the first surface, a conductive layer provided on the dielectric plate, and a power supply structure for supplying power to the radiating conductor, wherein, when the wavelength in air of a radio wave transmitted or received by the radiating conductor is λ and the wavelength shortening rate by the dielectric plate is k, the outer edge of the radiating conductor is a polygon having at least one side length of 0.8×k×(λ / 2) to 1.3×k×(λ / 2), a circle having a diameter of 0.8×k×(λ / 2) to 1.3×k×(λ / 2), or an ellipse having a major axis or a minor axis length of 0.8×k×(λ / 2) to 1.3×k×(λ / 2), and the conductive layer has an inner edge surrounding the radiating conductor such that a gap exists between the inner edge and the outer edge in a plan view of the dielectric plate, an inner edge of the conductive layer is a polygon having at least one side with a length of 0.25×λ or more and 1.75×λ or less, a circle having a diameter of 0.25×λ or more and 1.75×λ or less, or an ellipse having a major axis or a minor axis with a length of 0.25×λ or more and 1.75×λ or less, and a sheet resistance of the radiating conductor is equal to or less than the sheet resistance of the conductive layer.

2. The antenna device as described in claim 1, wherein the sheet resistance of the radiating conductor is 0.5 [mΩ / sq] or more and 50 [Ω / sq] or less, 1 [mΩ / sq] or more and 25 [Ω / sq] or less, or 3 [mΩ / sq] or more and 5 [Ω / sq] or less.

3. The antenna device according to claim 1, wherein the sheet resistance of the conductive layer is from 1 mΩ / sq to 200 Ω / sq, from 3 mΩ / sq to 50 Ω / sq, or from 300 mΩ / sq to 25 Ω / sq.

4. An antenna device as described in claim 1, comprising a light-shielding layer formed on the first surface or the second surface, the light-shielding layer having a portion that overlaps with the outer edge or the inner edge of the dielectric plate in a planar view.

5. The antenna device according to claim 1, wherein the conductive layer includes a first conductive layer provided on the first surface, the first conductive layer having a first inner edge which is the inner edge.

6. An antenna device as claimed in any one of claims 1 to 5, wherein the conductive layer includes a second conductive layer provided on an inner layer of the dielectric plate, and the second conductive layer has a second inner edge which is the inner edge.

7. An antenna device as described in any one of claims 1 to 4, wherein the conductive layer includes a first conductive layer provided on the first surface and a second conductive layer provided on an inner layer of the dielectric plate, the first conductive layer has a first inner edge which is the inner edge, and the second conductive layer has a second inner edge which surrounds the first inner edge so that a gap exists between the first inner edge and the second inner edge when viewed in a plane of the dielectric plate.

8. The antenna device according to claim 7, wherein the sheet resistance of the radiation conductor is lower than the sheet resistances of the first conductive layer and the second conductive layer.

9. An antenna device according to any one of claims 1 to 5, wherein the feeding structure feeds power to the radiation conductor in a non-contact manner.

10. An antenna device according to any one of claims 1 to 5, wherein the outer edge of the radiating conductor is in the shape of a square with a pair of diagonal corners cut out.

11. The antenna device according to any one of claims 1 to 5, wherein the radiation conductor has a void formed in the center.