ANTENNA DEVICE

Abstract

Antenna device comprising: a ground plate (10) made from a conductor with a flat plate shape; an opposing conductive plate (30), made of another conductor with a flat plate shape, is arranged to be spaced apart from the ground plate (10) by a predetermined distance, and has a power supply point that is electrically connected to a power supply line; and a short-circuit section (40) which is arranged in a central region of the opposite conductive plate (30) and electrically connects the opposite conductive plate (30) and the ground plate (10), wherein: a parallel resonance at a predetermined target frequency is generated by an inductance provided in the short-circuit section (40) and a capacitance between the ground plate (10) and the opposite conductive plate (30); the ground plate (10) is arranged asymmetrically with respect to the opposite conductive plate (30); the ground plate (10) and the opposite conductive plate (30) are arranged on a carrier plate (20) made of resin material, the antenna device further comprising: a resin housing (60) for receiving the carrier plate (20), wherein: the resin housing (60) includes a housing base (61) which is opposite the mass plate (10) with a predetermined distance between them; the resin housing (60) includes a housing side wall (62) which is raised from an edge of the housing base; the housing side wall (62) is positioned higher than an upper surface of the support plate (20); and an interior of the resin housing (60) is filled with a resin material having a relative dielectric constant of 2.0 or more, as a sealing material (70) for covering the upper surface of the carrier plate (20).

Description

TECHNICAL AREA

[0001] The present disclosure relates to an antenna device having a flat plate structure. STATE OF THE ART

[0002] JP 2005-20301A discloses an antenna device including a microstrip antenna (in other words, a patch antenna) and a monopole antenna mounted upright on the patch antenna. According to the antenna device, the patch antenna provides directivity in the direction perpendicular to the flat ground wire (hereinafter referred to as the ground plate), and the monopole antenna provides directivity in the direction parallel to the ground plate. According to this configuration, for example, when the ground plate is used in a horizontal position, it is possible to receive both radio waves arriving from the zenith direction and radio waves arriving from the horizontal direction. The radio wave arriving from the zenith direction is, for example, a radio wave from a satellite station. The radio wave from the horizontal direction is, for example, a radio wave from a ground station.

[0003] The configuration disclosed in JP 2005-20301A includes a monopole antenna for transmitting and receiving radio waves in the horizontal direction. Since the monopole antenna must have a length equal to one-quarter of the wavelength of the radio wave to be transmitted and received, the height of the antenna assembly (hereinafter referred to as the mounting height) is considerable. The mounting height here refers to the height when the antenna assembly is mounted on the moving body in a position where the plane of the patch antenna is horizontal. It is conceivable that the conductor element of the monopole antenna could be shortened using a coil or the like, but if the height is reduced by the coil or the like, the performance may degrade.

[0004] Reference is also made to JP 2017 - 005 663 A, which was determined to be state of the art. OVERVIEW OF THE INVENTION

[0005] The present disclosure was prepared based on this circumstance and its purpose is to provide an antenna device, the height of which is reduced in order to emit radio waves in the direction perpendicular to the ground and in the direction parallel to the ground.

[0006] The problem is solved by the subject matter of the independent claim. Advantageous further developments can be found in the dependent claims.

[0007] An antenna device comprises: a ground plane, which is a flat, plate-shaped conductor element; an opposing conductive plate, provided with a power supply point for electrical connection to a power supply line and made of a flat, plate-shaped conductor element installed at a predetermined distance from the ground plane; and a short-circuit section provided in a central region of the opposing conductive plate, electrically connecting the opposing conductive plate and the ground plane. Using the inductance provided in the short-circuit section and the electrostatic capacitance formed by the ground plane and the opposing conductive plate, parallel resonance occurs at a predetermined target frequency. The ground plane is arranged asymmetrically with respect to the opposing conductive plate.

[0008] In this type of antenna device, parallel resonance is generated due to an electrostatic capacitance formed between the ground plate and the opposite conductive plate, and an inductance contained in the short-circuited section. The parallel resonance is generated at a frequency corresponding to the electrostatic capacitance and the inductance. Then, due to the vertical electric field generated between the opposite conductive plate and the ground plate according to the parallel resonance, linearly polarized waves, whose oscillation direction of the electric field is perpendicular to the ground plate, are transmitted and received in the direction along the opposite conductive plate.

[0009] Furthermore, since the ground plate is arranged asymmetrically with respect to the opposite conductive plate, the magnitude of current flowing in the ground plate along one direction from the short-circuit section and the magnitude of current flowing in the opposite direction in the ground plate are asymmetrical. Consequently, the degree to which radio waves radiated by currents flowing in either direction from the short-circuit section cancel each other out is reduced. The radio waves radiated by the current flowing through the ground plate remain uncancelled, and the remaining radio waves propagate into space. That is, radio waves are radiated from a region of the ground plate that is asymmetrical when viewed from the opposite conductive plate (hereinafter referred to as an asymmetrical section).

[0010] Simulation confirms that the current is primarily induced at the edge of the asymmetric section. The edge of the ground plane can be considered linear. That is, according to the configuration described above, the edge of the asymmetric section of the ground plane acts as a linear antenna (for example, a pole-type antenna). The radio waves radiated from the asymmetric section of the ground plane are linearly polarized waves whose electric field oscillation direction is parallel to the ground plane. Furthermore, the radio wave radiated from the asymmetric section of the ground plane is radiated in a direction orthogonal to the edge of the asymmetric section. The direction orthogonal to the edge of the asymmetric section also includes the direction perpendicular to the ground plane.

[0011] As described above, according to the configuration above, radio waves can be radiated in the direction perpendicular to the ground plate and in the direction parallel to the ground plate. Furthermore, radiation in a direction parallel to the ground plate is generated by parallel resonance due to the capacitance formed between the ground plate and the opposite conductive plate, and the inductance provided in the short-circuit section. Therefore, the height of the antenna device can be reduced.

[0012] According to an example that serves as an illustrative example for a better understanding of the invention, the antenna device comprises: a ground plate, which is a flat, plate-shaped conductor element; an opposing conductive plate, which is provided with a power supply point for electrical connection to a power supply line and is made of a flat, plate-shaped conductor element installed at a predetermined distance from the ground plate; and a short-circuit section provided in a central region of the opposing conductive plate, which electrically connects the opposing conductive plate and the ground plate. Using the inductance provided in the short-circuit section and the electrostatic capacitance formed by the ground plate and the opposing conductive plate, parallel resonance occurs at a predetermined target frequency.The short-circuit section is formed at a position that is spaced a predetermined amount from the center of the opposite conductive plate.

[0013] In this configuration, linearly polarized waves with the oscillation direction of the electric field perpendicular to the ground plate in the direction along the opposite conducting plate are sent and received using the parallel resonance of the capacitance formed between the ground plate and the opposite conducting plate and the inductance provided in the short-circuit section.

[0014] Furthermore, in this configuration, since the short-circuit section is located at a position that deviates from the center of the opposite conductive plate, the symmetry of the current distribution—the current flowing through the opposite conductive plate—is broken, and the degree of cancellation of the radio waves radiated by the short-circuit section in any direction is reduced. Consequently, radio waves are radiated from the opposite conductive plate in a direction perpendicular to the opposite conductive plate. Since the opposite conductive plate is positioned to face the ground plate, the direction perpendicular to the opposite conductive plate corresponds to the direction perpendicular to the ground plate. That is, according to the above configuration, radio waves can be radiated both in the direction perpendicular to the ground plate and in the direction parallel to the ground plate.Furthermore, radiation in a direction parallel to the ground plate is generated by causing parallel resonance due to the capacitance formed between the ground plate and the opposite conductive plate, and the inductance provided in the short-circuit section. Therefore, the height of the antenna device can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The foregoing and other tasks, features, and advantages of the present disclosure will become clearer from the following detailed description in conjunction with the drawings. These show: Fig. 1. A perspective exterior view showing a configuration of the antenna device; Fig. 2 a cross-sectional view of the antenna device along line II-II in Fig. 1; Fig. 3 a diagram to explain the positional relationship between the ground plate and the opposite conductive plate; Fig. 4 a diagram illustrating a current distribution, a voltage distribution and an electric field distribution near the opposite conducting plate; Fig. 5 a diagram showing radiation characteristics in the LC resonance mode in the XY plane; Fig. 6 a diagram showing radiation characteristics in the LC resonance mode in the XZ plane and the YZ plane; Fig. 7 a diagram to explain the operating principle of the mass plate excitation mode; Fig. 8 a diagram to explain the operating principle of the mass plate excitation mode; Fig. 9 a diagram showing radiation characteristics provided by the mass plate excitation mode; Fig. 10 a diagram showing a relationship between gain in the horizontal direction of the antenna, gain in the upward direction of the antenna and width W of an asymmetric section; Fig. 11 a diagram showing an example of an antenna device mounting position and orientation on a vehicle; Fig. 12 a conceptual diagram showing the directivity of the antenna device according to the mounting position and orientation, which is in Fig. 11 are shown, shows; Fig. 13 a diagram to illustrate a preferred mounting position of the antenna device; Fig. 14 a diagram showing a modification example of the antenna device; Fig. 15 a diagram showing a modification example of the antenna device; Fig. 16 a diagram showing a modification example of the antenna device; Fig. 17 a diagram showing a configuration in which a circuit section is formed on a top surface of a carrier plate; Fig. 18 a diagram showing a modification example of the antenna device; Fig. 19 a diagram showing a modification example of the antenna device; Fig. 20 a diagram showing a modification example of the antenna device; Fig. 21 a diagram showing a configuration of a mass plate in which a connection state between a symmetry retention section and an asymmetric section is switchable; Fig. 22 a diagram showing an antenna device in which a short-circuit section is provided at a position that differs from the center of the opposite conductive plate; Fig. 23 a diagram showing a current distribution on an opposite conductive plate when a short-circuit section is formed in the middle of the opposite conductive plate; Fig. 24 a diagram to explain a current distribution on the opposite conductive plate and its operation when a short-circuit section is formed at a position spaced from the center of the opposite conductive plate; Fig. 25 a perspective external view showing the configuration of an antenna device, which serves as an illustrative example for a better understanding of the invention; and Fig. 26 A top view to illustrate the positional relationship between the ground plate, the opposite conductive plate and the short-circuit section. FORM OF EXECUTION OF THE INVENTION [Form of execution]

[0016] An embodiment of the present disclosure is described below according to the drawings. Elements with the same function are subsequently designated by the same reference numerals, and their redundant descriptions are omitted. If only part of the configuration is described, the configuration described in the previous embodiment can be applied to other parts.

[0017] Fig. Figure 1 is a perspective external view illustrating an example of a schematic structure of an antenna device 1 according to the present embodiment. Fig. Figure 2 is a cross-sectional view of the antenna device 1 along line II-II, which is in Fig. Figure 1 illustrates the antenna device 1, which is used to be mounted on a moving body such as a vehicle.

[0018] Antenna device 1 is configured to transmit and receive radio waves at a predetermined target frequency. In another mode, antenna device 1 can, of course, be used only for transmitting or only for receiving. Since transmitting and receiving radio waves are reversible, a configuration that can transmit radio waves at a predetermined frequency is the same as, or similar to, a configuration that can receive radio waves at the predetermined frequency.

[0019] Here, the operating frequency is, for example, 2.45 GHz. Of course, the target frequency can be appropriately designed, and target frequencies can be, for example, 300 MHz, 760 MHz, 850 MHz, 900 MHz, 1.17 GHz, 1.28 GHz, 1.55 GHz, 5.9 GHz, or the like. The antenna device 1 can not only transmit and receive the target frequency but also radio waves with a frequency within a predetermined range, determined with the target frequency as a reference. For example, the antenna device 1 is configured to transmit and receive frequencies belonging to the 2400 MHz to 2500 MHz band (hereinafter referred to as the 2.4 GHz band).

[0020] This means that the antenna device 1 can transmit and receive radio waves in frequency bands used in short-range radio communication, such as Bluetooth Low Energy (Bluetooth is a registered trademark), Wi-Fi (registered trademark), ZigBee (registered trademark), and the like. In other words, the antenna device 1 is configured to transmit and receive radio waves in the frequency band (so-called ISM band) specified by the International Telecommunication Union for general use in the industrial, scientific, and medical fields.

[0021] In the following, “λ” represents the wavelength of the radio wave at the target frequency (hereinafter also referred to as the target wavelength). For example, “λ / 2” and “0.5 λ” refer to one half of the target wavelength, and “λ / 4” and “0.25 λ” refer to one quarter of the target wavelength. The wavelength of the 2.4 GHz radio wave (that is, λ) in a vacuum and air is 125 mm.

[0022] The antenna device 1 is connected to a wireless device (not shown) by means of, for example, a coaxial cable, and a signal received by the antenna device 1 is sequentially output to the wireless device. The antenna device 1 converts an electrical signal input from the wireless device into a radio wave and emits the radio wave into space. The wireless device uses signals received by the antenna device 1 and also supplies radio frequency power to the antenna device 1 in accordance with transmitted signals.

[0023] In the present embodiment, an example is described in which the antenna device 1 and the wireless device are connected by the coaxial cable, although alternatively another communication cable, such as a power supply cable, can be used for the connection. The antenna device 1 and the wireless device can be connected by means of a matching network, a filter circuit, or the like, in addition to the coaxial cable. The antenna device 1 can be configured integrally with the wireless device. For example, the antenna device 1 can be implemented on a printed circuit board on which a modulation / demodulation circuit or the like is mounted.

[0024] The following describes a specific structure of antenna device 1. As in Fig. As shown in Figure 1, the antenna device 1 comprises a ground plate 10, a support plate 20, an opposing conductive plate 30, and a short-circuit section 40. For simplicity, each part is subsequently described as the top side of the antenna device 1, with the side on which the opposing conductive plate 30 is provided relative to the ground plate 10 being the side on which the antenna device 1 is located. That is, the direction from the ground plate 10 to the opposing conductive plate 30 corresponds to the upward direction for the antenna device 1. The direction from the opposing conductive plate 30 to the ground plate 10 corresponds to the downward direction for the antenna device 1.

[0025] The ground plate 10 is a conductive element in the form of a plate and is made of a conductor such as copper. The ground plate 10 is positioned along the underside surface of the carrier plate 20. The plate shape is a thin film, such as a metal foil. That is, the ground plate 10 can be a pattern formed on the surface of a resin plate, such as a printed wiring board, by electroplating or the like. The ground plate 10 is electrically connected to the outer conductor of the coaxial cable and provides the ground potential (in other words, ground) in the antenna device 1.

[0026] The ground plate 10 is rectangular. The length of the short side of the ground plate 10 is electrically fixed to a value corresponding to, for example, 0.4 λ. Furthermore, the length L of the long side of the ground plate 10 is electrically fixed to 1.2 λ. In this case, the electrical length is an effective length with respect to an electric stray field, a wavelength shortening effect due to a dielectric material, and the like. If the support plate 20 is made of a dielectric material with a relative permittivity or dielectric constant of 4.3, the wavelength on the surface of the ground plate 10 is approximately 60 mm due to the wavelength shortening effect of the dielectric material that forms the support plate 20. Therefore, the length that corresponds electrically to 1.2 λ is 72 mm.

[0027] The x-axis, which appears in various drawings such as Fig. Figure 1 shows the longitudinal direction of the ground plate 10, the Y-axis represents the transverse direction of the ground plate 10, and the Z-axis represents the vertical direction. A three-dimensional coordinate system including the X-axis, Y-axis, and Z-axis is a concept for describing the configuration of the antenna device 1. Furthermore, if the ground plate 10 has a square shape, the direction along any side can be the X-axis. If the ground plate 10 is circular, any direction parallel to the ground plate 10 can be defined as the X-axis. The Y-axis can be parallel to the ground plate 10 and orthogonal to the X-axis. If the ground plate 10 has a shape such as a rectangle or an ellipse, in which a longitudinal and a transverse direction exist, the longitudinal direction can be the X-axis direction.

[0028] The size of the mass plate 10 can be suitably modified. The length of one side of the mass plate 10 can be set to a value that is electrically smaller than a wavelength (for example, 1 / 3 of a target wavelength). Furthermore, the shape of the mass plate 10, viewed from above (hereinafter referred to as a planar shape), can be suitably modified. Here, for example, the planar shape of the mass plate 10 is a rectangular shape, whereas alternatively, as another aspect, the planar shape of the mass plate 10 can be a square shape or another polygonal shape. For example, the mass plate 10 can have a square shape in which one side is electrically fixed to a value corresponding to a wavelength.

[0029] It may be preferred that the mass plate 10 has a line-symmetric shape (hereinafter referred to as a bidirectional line-symmetric shape), wherein each of two straight lines represents an axis of symmetry orthogonal to the other. The bidirectional line-symmetric shape relates to a figure that is line-symmetric with a first straight line as one axis of symmetry and that is further line-symmetric with respect to a second straight line that is orthogonal to the first straight line. The bidirectional line-symmetric shape corresponds, for example, to an ellipse, a rectangle, a circle, a square, a regular hexagon, a regular octagon, a rhombus, or the like. The mass plate 10 may preferably be configured to have a size larger than a circle with a diameter equal to a wavelength. The planar shape of an element refers to the shape of the element as viewed from above.An edge section of the ground plate 10 can be partially or entirely meandering. The bidirectional line-symmetric shape also includes a form in which minute irregularities (approximately several millimeters) can be provided at the edge of the bidirectional line-symmetric shape. The unevenness provided on the edge of the ground plate 10 and the slot formed at a position away from the edge of the ground plate 10 can be neglected as long as they do not affect the antenna operation. The same applies to the point-symmetric shape.

[0030] The support plate 20 is a plate-shaped element for arranging the ground plane 10 and the opposing conductive plate 30 so that they face each other at a predetermined interval. The support plate 20 has a rectangular, flat plate shape, and its size in a top view is essentially the same as the size of the ground plane 10. The support plate 20 is made of a dielectric material having a predetermined relative permittivity, or dielectric constant, such as glass epoxy resin. For example, the support plate 20 is made of a glass epoxy resin with a relative permittivity of 4.3 (in other words, FR4: flame-retardant type 4).

[0031] In the present embodiment, for example, the thickness H1 of the carrier plate 20 is configured to be, for example, 1.5 mm. The thickness H1 of the carrier plate 20 corresponds to the distance between the ground plate 10 and the opposite conductive plate 30. By adjusting the thickness H1 of the carrier plate 20, the distance between the opposite conductive plate 30 and the ground plate 10 can be adjusted. The specific value of the thickness H1 of the carrier plate 20 can be suitably determined by simulations or experiments. The thickness H1 of the carrier plate 20 can be 2.0 mm, 3.0 mm, or the like. The wavelength of the carrier plate 20 is approximately 60 mm due to the wavelength shortening effect of the dielectric material. Therefore, a thickness of 1.5 mm corresponds electrically to 1 / 40 of the target wavelength (i.e., λ / 40).

[0032] The carrier plate 20 can fulfill the aforementioned function, and its shape can be suitably modified. A configuration for arranging the opposing conductive plate 30, facing the ground plate 10, can consist of multiple columns. Furthermore, in the present embodiment, a configuration in which a resin fills the carrier plate 20 is used between the ground plate 10 and the opposing conductive plate 30, although the present embodiment need not be limited to this. The space between the ground plate 10 and the opposing conductive plate 30 can be hollow or vacuum-sealed. The carrier plate 20 can, for example, have a honeycomb structure. Furthermore, the structures described above can be combined.If the antenna device 1 is implemented using a printed wiring board, several conductor layers included in the printed wiring board can be used as the ground plate 10 and the opposite conductive plate 30, and a resin layer separating the conductor layers can be used as the carrier plate 20.

[0033] The thickness H1 of the carrier plate 20 also functions as a parameter for setting the length of a short-circuit section 40 (in other words, the inductance provided by the short-circuit section 40), as will be described later. The interval H1 also functions as a parameter for setting the capacitance formed by the ground plate 10 and the opposing conductive plate 30, which face each other.

[0034] The opposing conductive plate 30 is a conductive element in a plate shape and is made of a conductor such as copper. As described above, the plate shape also includes a thin-film form, such as copper foil. The opposing conductive plate 30 is arranged to face the ground plate 10 by means of the support plate 20. Similar to the ground plate 10, the opposing conductive plate 30 can also have a pattern formed on the surface of a resin plate, such as a printed wiring board. The term "parallel" here need not be limited to perfectly parallel. The opposing conductive plate 30 can be inclined by several degrees up to ten degrees with respect to the ground plate 50. That is to say, the term "parallel" implies a substantially parallel state.

[0035] By arranging the opposing conductive plate 30 and the ground plate 10 to face each other, a capacitance is formed according to the area of ​​the opposing conductive plate 30 and the distance between the opposing conductive plate 30 and the ground plate 10. The opposing conductive plate 30 is designed to have a size that forms a capacitance which resonates in parallel with the inductance of the short-circuit section 40 at a target frequency. The area of ​​the opposing conductive plate 30 can be appropriately designed to provide the desired capacitance (and thus operate at the target frequency). For example, the opposing conductive plate 30 is electrically configured in a square shape with a side of 12 mm.Since the wavelength on the surface of the opposite conductive plate 30 is approximately 60 mm due to the wavelength shortening effect of the support plate 20, the value of 12 mm corresponds electrically to 0.2 λ. Of course, the length of one side of the opposite conductive plate 30 can be suitably changed and can be, for example, 14 mm, 15 mm, 20 mm, 25 mm or the like.

[0036] The opposite conductive plate 30 has, for example, a square shape, but alternatively, as another configuration, the planar shape of the opposite conductive plate 30 can be circular, regular octagonal, regular hexagonal, or the like. Furthermore, the opposite conductive plate 30 can have a rectangular or elongated shape. The opposite conductive plate 30 can preferably have a bidirectional line-symmetric shape. It is also preferred that the opposite conductive plate 30 is a point-symmetric figure such as a circle, a square, a rectangle, or a parallelogram.

[0037] The opposing conductive plate 30 may be slotted or have rounded corners. For example, a recess may be provided as a degenerate separating element on a pair of diagonal sections. An edge section of the opposing conductive plate 30 may be partially or completely meandering. Irregularities provided on the edge section of the opposing conductive plate 30 that do not affect the operation may be ignored.

[0038] A power supply point 31 is formed at an arbitrary position on the opposite conductive plate 30. The power supply point 31 is a section where the inner conductor of the coaxial cable and the opposite conductive plate 30 are electrically connected. The inner conductor of the coaxial cable corresponds to the power supply line. The power supply point 31 can be located at a position where the characteristic impedance of the coaxial cable and the impedance of the antenna device 1 can be matched at the target frequency. In other words, the power supply point 31 can be located at a position where the return loss reaches a predetermined permissible level. The power supply point 31 can be located at any position, such as in the central region of the edge section of the opposite conductive plate 20.

[0039] Various methods, such as a direct connection power supply method and an electromagnetic coupling method, can be used as a power supply method for the counter-conductor plate 30. The direct connection power supply method refers to a method in which a microstrip line, conductor pin, via, or the like, which is electrically connected to the inner conductor of the coaxial cable (i.e., for power supply), is directly connected to the counter-conductor plate 30. In the direct power supply method, the connection point between the microstrip line or the like and the counter-conductor plate 30 corresponds to the power supply point 31 for the counter-conductor plate 30.The electromagnetic coupling method refers to a power supply method using electromagnetic coupling between a microstrip line or the like for power supply and the counter-conductor board 30.

[0040] As in Fig. As shown in Figure 3, the opposite conductive plate 30 is arranged to face the ground plate 10 such that one set of opposite sides is parallel to the X-axis and another set of opposite sides is parallel to the Y-axis. The center of this set of opposite sides is arranged to deviate from the center of the ground plate 10 by a predetermined amount in the X-axis direction. In particular, the opposite conductive plate 30 is arranged such that its center is electrically offset from the center of the ground plate 10 in the X-axis direction by 1 / 20 (i.e., 0.05 λ) of the target wavelength. From another perspective, this configuration corresponds to a configuration in which the ground plate 10 is arranged asymmetrically with respect to the opposite conductive plate 30.

[0041] The distance between the center of the ground plate 10 (hereinafter referred to as the ground plate center) and the center of the opposite conductive plate 30 in the X-axis direction (hereinafter referred to as the ground plate offset ΔSa) need not be limited to 0.05 λ. The ground plate offset ΔSa may be 0.08 λ, 0.04 λ, 0.25 λ, or the like. The ground plate offset ΔSa may be fixed at λ / 8. The ground plate offset ΔSa may be suitably varied within a range in which the opposite conductive plate 30, viewed from above, does not protrude beyond the outer surface of the ground plate 10. The opposite conductive plate 30 is positioned such that at least its entire region (in other words, its entire surface) faces the ground plate 10. The ground plate offset ΔSa corresponds to the deviation between the center of the ground plate 10 and the center of the opposite conductive plate 30.

[0042] In Fig. Figure 3 shows the carrier plate 20 as transparent (i.e., not shown) to clarify the positional relationship between the ground plate 10 and the opposite conductive plate 30. The alternating long and short dashed line Lx1, which is shown in Fig. Figure 3 shows a straight line passing through the center of ground plate 10 and parallel to the X-axis, and the alternating long and short dashed line Ly1 represents a straight line passing through the center of ground plate 10 and parallel to the Y-axis. The alternating long and short dashed line Ly2 represents a straight line passing through the center of the opposite conductive plate 30 and parallel to the Y-axis. From another perspective, the straight line Lx1 corresponds to the axis of symmetry for ground plate 10 and the opposite conductive plate 30. The straight line Ly1 corresponds to the axis of symmetry for ground plate 10. The straight line Ly2 corresponds to the axis of symmetry for the opposite conductive plate 30.

[0043] Since the opposite conductive plate 30 is positioned such that it is offset by a predetermined amount in the X-axis direction from a position concentric with the ground plate 10, the alternating long and short dashed line Lx1 also passes through the center of the opposite conductive plate 30. That is, the alternating long and short dashed line Lx1 is a straight line parallel to the X-axis and corresponds to a straight line passing through the center of the ground plate 10 and the opposite conductive plate 30. The intersection of the straight line Lx1 and the straight line Ly1 corresponds to the center of the ground plate, and the intersection of the straight line Lx1 and the straight line Ly2 corresponds to the center of the opposite conductive plate 30 (hereinafter referred to as the conductive plate center). The conductive plate center corresponds to the center of gravity of the opposite conductive plate 30.Since the opposite conductive plate 30 has a square shape in the present embodiment, the center of the conductive plate corresponds to the intersection of two diagonal lines of the opposite conductive plate 30. The arrangement mode in which the ground plate 10 and the opposite conductive plate 30 are concentric corresponds to an arrangement mode in which the center of the opposite conductive plate 30 and the center of the ground plate 10 overlap in plan view.

[0044] The short-circuit section 40 is a conductive element that electrically connects the ground plate 10 and the opposite conductive plate 30. It is sufficient that the short-circuit section 40 is provided using a conductive pin (hereinafter referred to as the short-circuit pin). The inductance of the short-circuit pin 40 can be adjusted by setting the diameter and length of the short-circuit pin that serves as the short-circuit section 40.

[0045] The short-circuit section 40 can be a linear element, one end of which is electrically connected to the ground plate 10 and the other end of which is electrically connected to the opposite conductive plate 30. If the antenna device 1 is implemented using a printed wiring board as a base material, a via hole provided on the wiring board can be used as the short-circuit section 40.

[0046] The short-circuit section 40 is, for example, designed to be located at the center of the conductive plate. It should be noted that the position of the short-circuit section 40 does not necessarily have to coincide exactly with the center of the opposite conductive plate 40. The short-circuit section 40 may deviate from the center of the conductive plate by several millimeters. The short-circuit section 40 may be located in a central region of the opposite conductive plate 30. The central region of the opposite conductive plate 30 refers to a region within the line connecting the points that internally divides the conductive plate from the center of the edge section in a 1:5 ratio. From another perspective, the central region corresponds to a region where concentric figures overlap, in which the opposite conductive plate 30 is similarly reduced to 1 / 6. <Operation der Antennenvorrichtung 1>

[0047] The operation of the antenna device 1, configured as described above, is described. The opposite conductive plate 30 in the antenna device 1X is short-circuited to the ground plate 10 by a short-circuit section 40 provided in the central region of the opposite conductive plate 30, and the area of ​​the opposite conductive plate 30 is equal to an area for forming an electrostatic capacitance that resonates in parallel with the inductance of the short-circuit section 40 at the target frequency.

[0048] For this reason, a parallel resonance (so-called LC parallel resonance) occurs due to an energy exchange between the inductor and the capacitor, and a vertical electric field perpendicular to the ground plate 10 and the opposite conducting plate 30 is generated between the ground plate 10 and the opposite conducting plate 30. This vertical electric field propagates from the short-circuit section 40 towards the edge of the opposite conducting plate 30, and at the edge of the opposite conducting plate 30, the vertical electric field becomes a linearly polarized wave (i.e., a vertically polarized ground plate wave) with a plane of polarization perpendicular to the ground plate 10 and propagates in space. The vertically polarized ground plate wave is a radio wave in which the direction of oscillation of the electric field is perpendicular to the ground plate 10 and the opposite conducting plate 30.When the antenna device 1 is used in a position parallel to the horizontal plane, the vertically polarized wave of the ground plate refers to a polarized wave in which the oscillation direction of the electric field is perpendicular to ground (a so-called vertically polarized wave).

[0049] As in Fig. As shown in Figure 4, the direction of propagation of the vertical electric field is symmetrical with respect to the short-circuit section 40. Therefore, as shown in Figure 4, the direction of propagation of the vertical electric field is symmetrical with respect to the short-circuit section 40. Fig. As shown in Figure 5, the antenna device 1 has the same gain in all directions in the horizontal plane. In other words, at the target frequency, the antenna device 1 has a directional characteristic in all directions from the central region towards the edge of the opposite conductive plate 30 (that is, a horizontal antenna direction). When the ground plate 10 is oriented horizontally, the antenna device 1 functions as an antenna with a main beam in the horizontal direction. The horizontal plane of the antenna refers to a plane parallel to the ground plate 10 and the opposite conductive plate 30. The horizontal direction of the antenna refers to the direction from the center of the opposite conductive plate 30 towards its edge.From another perspective, the horizontal antenna direction refers to a direction perpendicular to a line perpendicular to the ground plate 10, which passes through the center of the opposite conductive plate 30. The horizontal antenna direction corresponds to a transverse direction of the antenna device 1.

[0050] Since the short-circuit section 40 is located at the center of the opposite conductive plate 30, a current flowing through the opposite conductive plate 30 is symmetrical about the short-circuit section 40. Therefore, a radio wave in the antenna's vertical direction, generated by a current flowing through the opposite conductive plate 30 in a certain direction from the center of the opposite conductive plate 30, is canceled out by a radio wave generated by the current flowing in the opposite direction. That is, the current excited by the opposite conductive plate 30 does not contribute to the emission of a radio wave. Therefore, as in Fig. As shown in Figure 6, radio waves are not emitted upwards from the antenna. For simplicity, a mode in which the antenna device 1 operates through the LC parallel resonance of the capacitance formed between the ground plate 10 and the opposite conductive plate 30, and the inductance of the short-circuit section 40, is hereafter referred to as an LC resonant mode. The LC resonant mode corresponds to an operating mode using a voltage oscillation of the opposite conductive plate 30 with respect to the ground plate 10. The LC resonant mode corresponds to a zero-order resonance mode. The antenna device 1 in the LC resonant mode corresponds to a voltage antenna.

[0051] Furthermore, the antenna device 1 also radiates radio waves from the ground plate 10 due to the fact that the ground plate 10 is asymmetrically configured when viewed from the opposite conductive plate 30. Specific examples are as follows. In the antenna device 1 of the present embodiment, the opposite conductive plate 30 is arranged such that it is electrically offset from a position concentric with the ground plate 10 in the X-axis direction by 1 / 20 (i.e., λ / 20) of the target wavelength. According to the embodiment in which the ground plate offset ΔSa is set to λ / 20, the region within λ / 10 of the edge section in the X-axis direction is the asymmetric section 11 for the opposite conductive plate 30. The asymmetric section 11 here refers to a region of the ground plate 10 that is asymmetrically configured when viewed from the opposite conductive plate 30. Fig. 7 and Fig. In Figure 8, the asymmetrical section 11 is hatched with a dot pattern to clearly indicate the region. For simplicity, the maximum region of the mass plate 10 that has symmetry with respect to the opposite conductive plate 30 is also referred to as the symmetry retention section 12. The symmetry retention section 12 is defined to include part of the edge section of the mass plate 10. The length of the symmetry retention section 12 from the midpoint to the end section in the X-axis direction is (L / 2 - ΔSa). The center of the symmetry retention section 12 and the center of the opposite conductive plate 30 coincide in the top view.

[0052] Fig. Figure 7 is a diagram that conceptually shows the current flowing through the ground plate 10. The simulation confirmed that the current flowing through the ground plate 10 due to the LC parallel resonance flows mainly along the edge of the ground plate 10. Fig. 7 represents the strength of the arrow, the amplitude of the current. In Fig. 7 is the carrier plate 20 drawn transparently (that is, not shown).

[0053] The current flowing from the opposite conductive plate 30 through the short-circuit section 40 and into the ground plate 10 flows from the short-circuit section 40 to both sides of the ground plate 10 in the longitudinal direction. The short-circuit section 40, which serves as the input and output of the current for the ground plate 10, is located at the center of the symmetry maintenance section 12 in the longitudinal direction. Furthermore, in the symmetry maintenance section 12, the currents flowing from the short-circuit section 40 to both ends in the X-axis direction have opposite directions and the same magnitude.Accordingly, the electromagnetic wave generated by the current flowing in a certain direction (for example, the positive x-axis direction) from the center of the symmetry maintenance section 12 is canceled out by the electromagnetic wave formed by the current flowing in the opposite direction (for example, the negative x-axis direction), as in . Fig. Figure 8 shows that the radio wave is not substantially emitted by the symmetry retention section 12.

[0054] However, the radio wave generated by the current flowing through the asymmetric section 11 remains unquenched. In other words, the edge of the asymmetric section 11 acts as a radiating element (essentially a linear antenna). The radio waves radiated from the ground plate 10 are linearly polarized waves in which the electric field oscillates in a direction parallel to the ground plate 10 (hereinafter referred to as parallel-polarized waves of the ground plate). Specifically, the radio wave radiated from the ground plate 10 is linearly polarized (hereinafter referred to as a wave parallel to the x-axis), with the direction of oscillation of the electric field being parallel to the x-axis. Furthermore, the parallel polarization of the ground plate is radiated in a direction orthogonal to the x-axis.This means that the parallel polarization of the ground plate is also radiated in the upward direction (hereinafter referred to as the upward direction of the antenna) for the antenna device 1.

[0055] For the sake of simplicity, the operating mode using the linear current flowing through the edge of the asymmetric section 11 of the ground plate 10 will henceforth be referred to as the ground plate excitation mode. The ground plate excitation mode corresponds to an operating mode in which linearly polarized waves, whose electric field oscillates in the direction in which the asymmetric section 11 and the symmetry-maintaining section 12 are connected (here the X-axis direction), are radiated in the direction perpendicular to the edge section. The antenna device 1 in the ground plate excitation mode corresponds to a current-based antenna that radiates radio waves by means of an induced current.When the antenna device 1 is used in a position parallel to the horizontal plane, the parallel polarization of the ground plate corresponds to the linear polarization (that is, the horizontal polarization) in which the direction of electric field oscillation is parallel to ground. Fig. Figure 9 is a diagram showing a simulation result of the radiation characteristics of the antenna device 1, in which the electrical length of the mass plate offset amount ΔSa is set to 0.05 λ in the mass plate excitation mode.

[0056] As described above, the antenna device 1 of the present embodiment can operate simultaneously in both the LC resonance mode, in which the beam is formed in the horizontal direction of the antenna, and the ground plate excitation mode, in which the beam is formed in the upward direction of the antenna. When the relationship between the length of the asymmetric section 11 in the X-axis direction (hereinafter referred to as the width W of the asymmetric section), the gain in the horizontal direction of the antenna, and the gain in the upward direction of the antenna was simulated, it was confirmed that the ratio between the gain in the plate vertical direction and the gain in the ground plate parallel varies depending on the length of the asymmetric section 511 in the X-axis direction (hereinafter referred to as the width W of the asymmetric section).The width W of the asymmetric section can be adjusted appropriately so that a desired gain ratio can be achieved.

[0057] In this case, the ratio of the gain in the vertical direction of the ground plate to the gain in the parallel direction of the ground plate can be affected not only by the width W of the asymmetric section, but also by the separation between the ground plate 10 and the rear metal body, which is a metal element that exists on the underside (in other words, the back) of the antenna device 1. Fig. Figure 10 shows the characteristics when a conductive plate larger than the ground plate 10 is positioned 4 mm below the ground plate 10. The width W of the asymmetric section is designed based on simulation or the like to achieve a desired gain ratio with respect to the separation between the rear metal body or metal chassis and the ground plate 10. As described above, the width W of the asymmetric section is set here to 0.1 λ, but can be set to 0.25 λ in another embodiment. The width W of the asymmetric section corresponds to twice the value of the ground plate offset ΔSa. Thus, the configuration in which the width W of the asymmetric section is 0.25 λ corresponds to the configuration in which the ground plate offset ΔSa is set to 0.125 λ.

[0058] The operation of antenna device 1 when transmitting radio waves and the operation of antenna device 1 when receiving radio waves are mutually reversible. That is, according to antenna device 1, the vertical polarization of the ground plane arriving from the horizontal direction of the antenna can be received, and the parallel polarization of the ground plane arriving from the upward direction of the antenna can likewise be received.

[0059] By operating in LC resonant mode, antenna device 1 can transmit and receive the vertical polarization of the ground plane in all directions along the horizontal axis of the antenna. Simultaneously, antenna device 1 operates in ground plane excitation mode, allowing it to transmit and receive ground plane parallel polarization in the upward direction of the antenna. In this way, antenna device 1 can transmit and receive radio waves with different polarization planes in directions orthogonal to each other.

[0060] Furthermore, the antenna device 1 utilizes the parallel resonance of the capacitance formed between the ground plate 10 and the opposite conductive plate 30, and the inductance provided in the short-circuit section 40, to generate vertical polarization in the horizontal direction of the antenna. In the configuration disclosed in JP 2005-20301A, an electrical length of λ / 4 is required to transmit and receive vertically polarized waves in the horizontal direction of the antenna, where the height (in other words, thickness) of the antenna device 1 is approximately λ / 100. That is, the size of the antenna device 1 in the vertical direction can be reduced.

[0061] Furthermore, the antenna device 1 operates in ground-plate excitation mode because the asymmetric section 11 is arranged adjacent to (and extends over) the symmetry-maintaining section 12. That is, as a configuration for adding further directivity in the upward direction of the antenna of the antenna device 1 as the LC resonant antenna, the ground plate 10 can be provided in a position that is asymmetric with respect to the opposite conductive plate 30. The aforementioned asymmetric section 11 can be realized using a portion of the ground plate 10 that is incorporated into the LC resonant antenna. Therefore, according to the configuration of the present embodiment, it is possible to reduce the manufacturing costs compared to the case in which the antenna for horizontally polarized waves is provided separately from the antenna for vertically polarized waves. <Verwendung der Antennenvorrichtung 1>

[0062] The antenna device 1 described above can, for example, be configured as shown in Fig. As shown in Figure 11, the device can be used by mounting it on the outer surface of the vehicle cabin at the B-pillar 51 of the vehicle, such that the grounding plate 10 faces the surface of the B-pillar 51, and the X-axis direction is aligned along the longitudinal direction (in other words, the vehicle's height direction) of the B-pillar 51. Alternatively, the device 1 can be mounted to have the position described above on an inner section of the door panel that overlaps the B-pillar 51.

[0063] According to the above mounting position, the Z-axis direction (in other words, the upward direction of the antenna) for antenna device 1 corresponds to the direction orthogonal to the side surface of the vehicle (that is, the vehicle width direction), and the horizontal direction of the antenna is the direction along the side surface of the vehicle (in other words, a parallel direction). According to the mounting position as shown in Fig. As shown in 12, the directional effect can be formed in both the direction parallel to the vehicle side surface section and in the vehicle width direction.

[0064] The mounting position and orientation of the antenna device 1 need not be limited to the examples above. The antenna device 1 can be mounted at any position on the vehicle's exterior surface, such as the exterior surface of the vehicle cabin at the A-pillar 52 and the C-pillar, the sill section (in other words, the side sill) 54, and the inside / near the outer door handle 55. For example, the antenna device 1 can be mounted inside the outer door handle 55 in a position where the X-axis direction is along the longitudinal direction of the handle and the Y-axis is along the vehicle's vertical direction.

[0065] It may be preferred that the antenna device 1 is mounted on the flat metal body section of the vehicle (hereinafter referred to as the vehicle body 50) in a position in which the ground plate 10 faces the vehicle body 50. According to the embodiment in which the antenna device 1 is mounted on the vehicle body 50, the vehicle body 50 functions as a base plate (hereinafter referred to as a main ground plate) for the ground plate 10, as shown in Fig. Figure 13 shows that the operation of antenna device 1 is stable.

[0066] Although the embodiment of the present disclosure has been described above, the present disclosure is not limited to the embodiment described above, and various modifications described below are likewise included within the technical scope of the present disclosure. Furthermore, various modifications may be made within the scope that do not deviate from the following. For example, various modifications to be described below may be implemented in suitable combinations within a scope that does not cause any technical inconsistency. [Modification 1]

[0067] As in Fig. As shown in Figure 13, the antenna device 1 can include a main ground plate 50a that is larger than the ground plate 10 and is located on the underside of the ground plate 10. The main ground plate 50a can preferably be a conductor element with a length of one wavelength or more in both the X-axis and Y-axis directions. If the ground plate 10 is defined as the first ground plate, the main ground plate 50a corresponds to the second ground plate. The conductor element, as the main ground plate 50a, can be an element having a substantially flat surface facing the ground plate 10.

[0068] The main ground plate 50a is arranged to face the ground plate 10 at a predetermined distance. The main ground plate 50a is located on the inner bottom surface of the resin housing 60 of the antenna device 1, for example, as shown in (A) of Fig. As shown in (B) of 14, arranged. Fig. As shown in Figure 14, the main ground plate 50a can be arranged on the outer bottom surface of the housing 60 of the antenna device 1. The housing 60 and the main ground plate 50a can be integrally formed. Furthermore, the bottom of the housing 60 can be made of metal. In this case, the bottom of the metal housing corresponds to the main ground plate 50a. Alternatively, the vehicle metal body 50 can be used as the main ground plate 50a. [Second modification]

[0069] As explained in the first modification, the antenna device 1 can include a housing 60 for receiving the ground plate 10, the opposing conductive plate 30, and the support plate 20 on which the short-circuit section 40 is formed. The housing 60 is formed by combining, for example, an upper housing and a lower housing, which are vertically separable. The housing 60 is constructed using, for example, a polycarbonate (PC) resin. Various resins, such as a synthetic resin obtained by mixing acrylonitrile butadiene styrene copolymer (so-called ABS) with PC resin and polypropylene (PP), can be used as the housing 60 material. The housing 60 includes a housing bottom section 61, a housing side wall section 62, and a housing top plate section 63. The housing bottom section 61 is configured to provide the base of the housing 60.The housing base section 61 is designed in a flat plate form. The printed circuit board 100 is arranged in the housing 60 such that the ground plane 10 faces the housing base section 61. The distance between the housing base section 91 and the ground plane 10 can preferably be set to λ / 25 or less.

[0070] The housing side wall section 62 is configured to provide the lateral surface of the housing 60 and is positioned upwards from the edge section of the housing bottom section 61. The height of the housing side wall section 62 is designed such that, for example, the distance between the inner surface of the housing top plate section 63 and the opposite conductive plate 30 is λ / 25 or less. The housing top plate section 63 is configured to provide an upper surface section of the housing 60. The housing top plate section 63 of this embodiment is formed in a flat plate shape. Various other shapes, such as a dome shape, can be used for the housing top plate section 63. The housing top plate section 63 is configured such that its inner surface faces the upper surface of the support section 20 (and thus the opposite conductive plate 30).

[0071] When the housing top plate section 63 is arranged close to the opposite conductive plate 30 as in the configuration described above, the wrapping of the vertical electric field radiated by the LC resonant mode from the edge section of the opposite conductive plate 30 is suppressed, and the antenna gain in the horizontal direction can be increased. The term "close to the opposite conductive plate 30" refers, for example, to a region where the distance from the opposite conductive plate 30 is electrically 1 / 25 or less of the target wavelength. When the housing bottom plate section 61 is arranged close to the ground plate 10 as in the configuration described above, the wrapping of the vertical electric field radiated by the LC resonant mode from the edge section of the ground plate 10 is suppressed.wrapping), and the antenna gain in the horizontal direction can be increased.

[0072] Furthermore, if the antenna device 1 includes the housing 60, it may be preferred that the inside of the housing 60 be filled with a sealing material 70 such as silicone. The sealing material 70 corresponds to a sealing element. According to the configuration in which the housing 60 is filled with the sealing material 70, the sealing material 70, which is arranged above the opposite conductive plate 30, suppresses the wrapping or winding of the vertical polarization of the ground plate from the end section of the opposite conductive plate 30 to the top, thus improving the antenna gain in its horizontal direction. In the housing 60, at least one side surface section and one top surface section may be made of resin or ceramic with a predetermined relative dielectric constant.Furthermore, depending on the configuration in which the sealing material 70 is filled in the housing 60, water tightness, dust tightness and vibration resistance can be improved.

[0073] Furthermore, as in Fig. As shown in Figure 15, the housing top plate section 63 can be configured with an upper rib 631 that comes into contact with the edge section of the opposite conductive plate 30. The upper rib 631 has a convex structure that projects downwards onto the inner surface of the housing top plate section 63. The upper rib 631 is designed to come into contact with the edge section of the opposite conductive plate 30. The upper rib 631 secures the position of the support plate 20 in the housing 60, prevents the vertical polarization of the ground plate from wrapping around from the end of the opposite conductive plate 30 towards the top, and improves the antenna gain in the horizontal direction.A metal pattern such as a copper foil can be arranged on the vertical surface (that is, the outer surface) of the upper rib 631, which is connected to the edge of the opposite conductive plate 30.

[0074] Since the housing 60 and the main ground plate 50a have independent configurations, only one of them can be fitted. For example, the antenna device 1 can include a housing 60 without the main ground plate 50a. Filling the sealing material 70, when the antenna device 1 includes the housing 60, need not be an essential element. The upper rib 631 can also be an optional element. Urethane resin, such as a polyurethane prepolymer, can be used as the sealing material 70. Various other materials, such as epoxy resin and silicone resin, can also be used as the sealing material 70.The housing top plate section 63, the upper rib 631, and the sealing material 70 correspond to a configuration (hereinafter referred to as a radio wave shield) that suppresses the vertical electric field radiated by the LC resonant mode from wrapping around the edge section of the opposite conductive plate 30. The configuration disclosed as the second modification corresponds to a configuration in which a radio wave shielding body, configured using a conductor or a dielectric material, is arranged on the top surface of the opposite conductive plate 30.

[0075] The housing 60, which includes the upper rib 631 and the sealing material 70, may preferably have a high relative permittivity and a low dielectric loss factor. For example, it may be preferred that the relative permittivity is 2.0 or greater and the dielectric loss factor is 0.03 or less. When the dielectric loss factor is high, the amount of radiant energy lost as heat increases. Therefore, it may be preferred that the housing 60 and the sealing material 70 be made of a material with a lower dielectric loss factor. Furthermore, the housing 60 and the sealing material 70 function in such a way that they strongly suppress the wrapping of the electric field as the permittivity increases.In other words, the higher the dielectric constant of the housing 60 and the sealing material 70, the better the gain improvement effect in the horizontal direction of the antenna. Therefore, it may be advantageous for the housing 60 and the sealing material 70 to be made of a dielectric with a high dielectric constant.

[0076] Either the housing base 91 or the housing top plate 93, which are contained within the housing 90, can be omitted. If either the top or the bottom of the housing 90 is omitted (i.e., an opening is created), the sealing material 70 can preferably be implemented using a resin that maintains strength within the temperature range assumed to be that of the environment in which the antenna device 1 is used (hereinafter referred to as the operating temperature range). The operating temperature range can, for example, be -30 °C to 100 °C. [Third modified example]

[0077] As in Fig. As shown in Figure 16, a circuit unit 80, including a modulation / demodulation circuit, a power supply circuit, and the like, can be formed on the surface of the carrier plate 20 on the side on which the opposing conductive plate 30 is arranged (hereinafter referred to as the top surface 20a of the carrier plate). The circuit unit 80 is an electrical assembly of various parts, such as an IC, an analog circuit element, and a connector. This configuration corresponds to a configuration in which the antenna device 1 is implemented by arranging the ground plate 10, the opposing conductive plate 30, the shorting section 40, and the circuit unit 80 on the printed circuit board that forms the carrier plate 20. Reference numeral 81 in Fig. 16 provides a microstrip line for supplying electrical energy to the opposite conductive plate 30. The circuit unit 80 can, for example, be formed in a region located above the asymmetric section 11 on the top surface 20a of the carrier plate. [Fourth modified example]

[0078] The arrangement mode of the opposing conductive plate 30 with respect to the ground plate 10 need not be limited to the configuration disclosed as the embodiment. The opposing conductive plate 30 can be arranged in a position other than that which is concentric with the ground plate 10. Different arrangement modes can be used for the opposing conductive plate 30 with respect to the ground plate 10, as shown in Fig. 17 to Fig. 20 is illustrated. In Fig. In figures 17 to 20, the carrier plate 20 is drawn transparently (i.e., not shown) to clarify the positional relationship between the ground plate 10 and the opposite conductive plate 30. In each drawing, the area corresponding to the asymmetrical section 11 is marked with a dot pattern hatching as shown in Fig. 7. The dimensions of each drawing are examples and can be modified as appropriate.

[0079] It should be noted that Lx2, which is in Fig. Figure 18 shows a straight line passing through the center of the opposite conductive plate 30 and parallel to the X-axis. The configuration shown in Fig. The configuration disclosed in Figure 18 corresponds to a configuration in which the opposite conductive plate 30 is arranged to be offset by a predetermined amount in the Y-axis direction from a position concentric with the ground plate 10. The offset direction of the conductive plate, which is the direction in which the opposite conductive plate 30 is offset relative to the ground plate 10, need not necessarily be limited to the longitudinal direction of the ground plate 10 (i.e., the X-axis direction). The offset direction of the conductive plate can be the transverse direction of the ground plate 10. The offset direction of the conductive plate corresponds to the direction in which the asymmetric section 11 of the ground plate 10 is arranged when viewed from the opposite conductive plate 30. Fig. Figure 19 illustrates an embodiment in which the opposing conductive plate 30 is circular. As described above, different shapes can be used for the ground plate 10 and the opposing conductive plate 30.

[0080] Furthermore, as in Fig. As shown in Figure 20, according to the configuration in which the asymmetrical sections 11 are provided in the X-axis direction and the Y-axis direction respectively, the edge section parallel to the X-axis and the edge section parallel to the Y-axis function as radiating elements. ΔSa1 in Fig. 20 represents the mass plate offset ΔSa in the X-axis direction, and ΔSa2 represents the mass plate offset ΔSa in the Y-axis direction. ΔSa1 and ΔSa2 can have the same or different values.

[0081] According to the configuration that is in Fig. As shown in Figure 20, both the polarization parallel to the X-axis and the linear polarization, whose electric field oscillation direction is parallel to the Y-axis (hereinafter referred to as polarization parallel to the Y-axis), can be radiated upwards on the antenna. In particular, diagonally polarized waves, formed by synthesizing polarization parallel to the X-axis according to ΔSa1 and polarization parallel to the Y-axis according to ΔSa2, can be radiated. By adjusting the ratio ΔSa and ΔSa2, the ratio of the polarization parallel to the X-axis to the polarization parallel to the Y-axis, which forms the diagonally polarized wave, can be arbitrarily adjusted. The configuration shown in Figure 20 Fig. Figure 20 shows a configuration in which the opposite conductive plate 30 is offset by a predetermined amount in the X-axis direction from a position that is concentric with the mass plate 10, and further offset by a predetermined amount in the Y-axis direction. [Fifth modification]

[0082] The symmetry-preserving section 12 and the asymmetric section 11 can be physically separated, as in Fig. Figure 21 shows that the electrical connection state between two sections can be switched using a switch 13. The separation between the symmetry-maintaining section 12 and the asymmetric section 11 can be set to a value based on the simulation that does not cause electromagnetic coupling at the target frequency. When the switch 13 is off, the antenna device 1 operates only in LC resonant mode. When the switch 13 is on, the antenna device 1 operates in both LC resonant mode and ground-plate excitation mode. According to this configuration, it is possible to control whether or not the antenna device 1 operates in ground-plate excitation mode by turning the switch 13 on and off. In this modification configuration, the width W of the asymmetric section can preferably be set to an integral multiple of λ / 4, such as λ / 4 or λ / 2.According to such a definition, the gain can be increased as the mass plate excitation mode. [Sixth modified example]

[0083] As in Fig. As shown in Figure 22, the short-circuit section 40 can be arranged at a position that deviates from the center of the opposite conducting plate 30 by a predetermined amount in the Y-axis direction (hereinafter short-circuit section offset amount ΔSb). According to this configuration, the symmetry of the current distribution on the opposite conducting plate 30 is broken, and linearly polarized waves parallel to the Y-axis direction are radiated from the opposite conducting plate 30. Specific examples are as follows.

[0084] In the configuration where the short-circuit section 40 is arranged at the center of the opposite conductive plate 30, as in the antenna device 1 of the embodiment, the current flowing through the opposite conductive plate 30 is symmetrical with a center on the short-circuit section 40, as in Fig. Figure 23 shows that the radio waves generated by the current flowing in a certain direction from the connection point of the opposite conductive plate 30 (hereinafter referred to as the short-circuited point) between the short-circuited section 40 and the opposite conductive plate 30 are canceled out by the radio waves generated by the current flowing in the opposite direction.

[0085] On the other hand, in the configuration where the short-circuit section 40 is located at a position that deviates from the center of the opposite conductive plate 30 by a predetermined amount in the Y-axis direction, the symmetry in the current distribution of the current flowing through the opposite conductive plate 30 is as shown in (A) of Fig. 24 is shown, broken. Accordingly, as in Fig. As shown in Figure 6B, the radio waves radiated by the current component in the Y-axis direction remain unquenched. That is, in the configuration where the short-circuit section 40 is located at a position that deviates by a predetermined amount in the Y-axis direction from the center of the opposite conducting plate 30, the linearly polarized waves, in which the electric field oscillates in the direction parallel to the Y-axis, are radiated upwards from the opposite conducting plate 30. Since the symmetry of the current component in the X-axis direction is maintained, the linearly polarized waves, in which the electric field oscillates in the X-axis direction, cancel each other out. That is, the linearly polarized wave whose electric field oscillates in the X-axis direction is not radiated from the opposite conducting plate 30.

[0086] Naturally, according to the above configuration, the vertical polarization of the ground plate in the horizontal direction of the antenna is radiated by the parallel resonance of the capacitance formed between the opposite conductive plate 30 and the ground plate 10, and the inductance provided by the short-circuit section 40. That is, according to the above configuration, the vertical polarization of the ground plate in the horizontal direction of the antenna, the polarization parallel to the X-axis in the upward direction of the antenna, and the polarization parallel to the Y-axis in the upward direction of the antenna can be radiated simultaneously. The radiation of the polarization parallel to the X-axis in the upward direction of the antenna is provided by the asymmetric section 11 of the ground plate 10.The emission of the polarization parallel to the Y-axis in the upward direction of the antenna is provided by the offset arrangement of the short-circuit section 40 in the Y-axis direction.

[0087] The direction of displacement of the short-circuit section 40 with respect to the center of the opposite conducting plate 30 (hereinafter referred to as the short-circuit section offset) can be orthogonal to the offset direction of the conducting plate. According to this configuration, it is possible to radiate two types of linearly polarized waves, whose electric field oscillation directions are orthogonal to each other, as linearly polarized waves radiated upwards on the antenna.

[0088] The short-circuit section 40 can be formed in a central region of the opposite conductive plate 30. The short-circuit offset ΔSb can preferably be set to 0.04 λ or less to maintain omnidirectionality in the horizontal direction of the antenna. It is preferred that the short-circuit offset ΔSb be 0.02 λ (= 2.5 mm) or less, such as 0.004 λ (= 0.5 mm), 0.008 λ (= 1.0 mm), 0.012 λ (= 1.5 mm), etc. By changing the short-circuit offset ΔSb, the radiation gain of polarization parallel to the Y-axis in the upward direction of the antenna can be adjusted. Furthermore, the operating frequency does not change even when the short-circuit offset ΔSb is changed. If the position of the power supply point 31 is fixed, the VSWR can fluctuate according to the short-circuit section offset amount ΔSb.Since the power supply point 31 can be set to any position, the VSWR at the target frequency can be suppressed to a practical level (for example, 3 or less) by positioning the power supply point 31 at a location corresponding to the short-circuit offset ΔSb. That is, the return loss can be suppressed to a desired permissible level by adjusting the position of the power supply point 31 according to the position of the short-circuit section 40. [Explanatory example for better understanding of the invention]

[0089] In the first embodiment described above, the configuration is disclosed subject to the condition that the opposite conductive plate 30 is arranged in a position that deviates from the center of the ground plate 10, with the alternative being that the configuration of the antenna device 1 need not be limited to this feature. If the antenna device 1 has the configuration disclosed in modified Example 6, the opposite conductive plate 30 may be arranged in a position that is concentric with the ground plate 10, as shown in Fig. 25 and Fig. 26 is shown. In other words, in the configuration where the short-circuit section 40 is located at a position that deviates from the center of the opposite conductive plate 30, the ground plate 10 does not always have to have the asymmetric section 11. Lx2 and Ly2, which are shown in Fig. Figure 25 shows the axes of symmetry of the opposite conducting plate 30. Lx1 and Ly1, which are shown in Fig. Figures 26 show the axis of symmetry of the mass plate 10.

[0090] As disclosed in the embodiment and the explanatory example for better understanding of the invention, the radiation of parallel polarization of the ground plate in the upward direction of the antenna can be achieved using at least one of the configurations in which the short-circuited section 40 is arranged to be offset from the center of the opposite conductive plate 30 in the direction along the axis of symmetry, and the configuration in which the asymmetric section 11 is added to the ground plate 10. As a further aspect, as disclosed in Japanese patent application no. JP 2016-15688A, a configuration (hereinafter referred to as a comparative configuration) is also conceivable such that the opposite conductive plate 30 operates as a patch antenna by arranging the second power supply point on the axis of symmetry of the opposite conductive plate 30.In the comparative configuration, two power supply points are required, which complicates the circuit. On the other hand, according to the configurations of the embodiment and the explanatory example, for a better understanding of the invention, the opposite conductive plate 30 can have only one power supply point, thus simplifying the circuit configuration.

[0091] Although the present revelation has been described according to the examples, it is evident that the present revelation is not limited to such examples or structures. The present revelation also includes various modified examples and modifications within a unified scope. Furthermore, various combinations and elaborations, as well as other combinations and formations that contain only one element or more or less than these elements, also fall within the spirit and scope of the present revelation.

Claims

[1] Antenna device comprising: a ground plate (10) made from a conductor with a flat plate shape; an opposing conductive plate (30), made of another conductor with a flat plate shape, is arranged to be spaced apart from the ground plate (10) by a predetermined distance, and has a power supply point that is electrically connected to a power supply line; and a short-circuit section (40) which is arranged in a central region of the opposite conductive plate (30) and electrically connects the opposite conductive plate (30) and the ground plate (10), wherein: a parallel resonance at a predetermined target frequency is generated by an inductance provided in the short-circuit section (40) and a capacitance between the ground plate (10) and the opposite conductive plate (30); the ground plate (10) is arranged asymmetrically with respect to the opposite conductive plate (30); the ground plate (10) and the opposite conductive plate (30) are arranged on a carrier plate (20) made of resin material, the antenna device further comprising: a resin housing (60) for receiving the carrier plate (20), wherein: the resin housing (60) includes a housing base (61) which is opposite the mass plate (10) with a predetermined distance between them; the resin housing (60) includes a housing side wall (62) which is raised from an edge of the housing base; the housing side wall (62) is positioned higher than an upper surface of the support plate (20); and an interior of the resin housing (60) is filled with a resin material having a relative dielectric constant of 2.0 or more, as a sealing material (70) for covering the upper surface of the carrier plate (20). [2] Antenna device according to claim 1, wherein: the mass plate (10) is arranged in a shape symmetrically with respect to each of two straight lines that are orthogonal to each other; the opposite conductive plate (30) has an entire surface facing the ground plate (10); and a center of the opposite conductive plate (30) does not overlap with a center of the ground plate (10). [3] Antenna device according to claim 1 or 2, wherein: the mass plate (10) has a rectangular shape; the opposite conductive plate (30) has an entire surface facing the ground plate (10); and the opposite conductive plate (30) is arranged at a position which is displaced in a longitudinal direction of the ground plate (10) from a position where the opposite conductive plate (30) and the ground plate (10) are concentric. [4] Antenna device according to claim 3, wherein: the opposite conductive plate (30) is arranged at a position that deviates by a predetermined amount in the longitudinal direction of the ground plate (10) from a center of the ground plate (10). [5] Antenna device according to any one of claims 1 to 4, wherein: the short-circuit section (40) is arranged at a position that is spaced a predetermined amount away from the center of the opposite conductive plate (30). [6] Antenna device according to any one of claims 1 to 5, wherein: the mass plate (10) has a rectangular shape; the opposite conductive plate (30) has an entire surface facing the ground plate (10); the opposite conductive plate (30) is arranged at a position that deviates from a center of the ground plate (10) in a longitudinal direction of the ground plate (10); and the short-circuit section (40) is arranged at a position which deviates by a predetermined amount in a transverse direction of the ground plate (10) from a position in which the opposite conductive plate (30) and the ground plate (10) are concentric. [7] Antenna device according to claim 6, wherein: the short-circuit section (40) is arranged at a position that deviates by a predetermined amount in the transverse direction of the ground plate (10) from a center of the ground plate (10). [8] Antenna device according to any one of claims 1 to 7, wherein: the opposite conducting plate (30) is arranged in a shape that is line-symmetric with respect to each of two straight lines that are orthogonal to each other. [9] Antenna device according to any one of claims 1 to 8, further comprising: a radio wave shielding body (63, 631, 70) for shielding against the propagation of an electric field, which is made of a conductor or a dielectric material and is arranged on the top side of the opposite conductive plate (30).

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