ANTENNA DEVICE

Abstract

Antenna device comprising: a ground plate (10) made from a conductor with a flat plate shape; an opposing conductive plate (20) 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 which is electrically connected to a power supply line; a short-circuit section (40) that electrically connects the opposite conductive plate (20) and the ground plate (10); and a radio wave shielding body (60) for shielding against the propagation of an electric field, which is arranged on a top side of the opposite conductive plate (20) and is made of a conductor or a dielectric material, 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 (20), and wherein the ground plate (10) and the opposite conductive plate (20) are arranged on a carrier plate (30) made of resin material, the antenna device further comprising: a resin housing (90) for receiving the carrier plate (30), wherein: the resin housing (90) includes a housing top plate section (93) which is arranged above the opposite conductive plate (20); and the housing top plate section (93) includes an edge contact section (931) which contacts an edge section of the opposite conductive plate (20).

Description

TECHNICAL AREA

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

[0002] As disclosed in US 7 911 386 B1, there are antenna devices that include: a flat, plate-shaped metal conductor (hereinafter referred to as a ground plate) that acts as a ground; a flat, plate-shaped metal conductor (hereinafter referred to as an opposite conductive plate) that is positioned to face the ground plate and has a power supply point located at any position; and a short-circuit section that electrically connects the ground plate to the opposite conductive plate.

[0003] 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. Specifically, the opposite conductive plate and the ground plate act as a capacitor, and a vertical electric field is generated between the opposite conductive plate and the flat plate due to the current flowing through the short-circuited section. The vertical electric field propagates from the short-circuited section toward the outer circumferential section and leaks into the space at the end of the opposite conductive plate, allowing radio waves to be radiated perpendicular to the ground plate.For the sake of simplicity, an antenna device operating by parallel resonance of the capacitance formed between the ground plate and the opposite conductive plate and the inductance provided in the short-circuit section will henceforth be referred to as a 0th order resonant antenna.

[0004] The capacitance formed between the ground plate and the opposite conductive plate is determined by the area of ​​the opposite conductive plate and the distance between the ground plate and the opposite conductive plate. Furthermore, the inductance provided in the short-circuit section is determined by the diameter of the short-circuit section. Thus, for example, by adjusting the area of ​​the opposite conductive plate and the diameter of the short-circuit section, the frequency to be transmitted and received in the antenna device (hereinafter referred to as the target frequency) can be set to a desired frequency. US 7,911,386 B1 further discloses a configuration in which several patch units, each equipped with an opposite conductive plate and a short-circuit section, are arranged periodically.Such a configuration, in which the zeroth order resonant antennas are arranged periodically, is also called a metamaterial antenna.

[0005] Reference is also made to JP 2018 - 061 137 A, which was determined to be state of the art. OVERVIEW OF THE INVENTION

[0006] When the inventors verified the operating mode of the zero-order resonant antenna, they discovered that the vertical electric field radiated from the edge of the opposite conductive plate wraps around the top surface of that plate. As the vertical electric field wraps around the top surface of the opposite conductive plate, the vertical electric field propagating in the horizontal direction of the antenna is reduced by that amount. This means the gain in the horizontal direction of the antenna can be reduced. It was also found that this tendency becomes more pronounced as the distance between the opposite conductive plate and the ground plate decreases (i.e., the thinner the antenna structure). The horizontal direction of the antenna here refers to the direction from the center of the opposite conductive plate towards its edge.The horizontal direction of the antenna corresponds to the side for the antenna device.

[0007] The present disclosure is based on this circumstance and the purpose of the present disclosure is to provide an antenna device that can maintain / improve the gain in the horizontal direction of the antenna in the antenna device, which operates by parallel resonance of the capacitance formed between the ground plate and the opposite conductive plate and the inductance of the short-circuit section.

[0008] This task is solved by the subject matter of the independent claim. Advantageous further developments can be found in the dependent claims.

[0009] An antenna device comprises: a ground plane, which is a flat conductor element; an opposite conductive plate, which is a flat conductor element installed at a predetermined distance from the ground plane and electrically connected to a power supply line; a short-circuit section for electrically connecting the opposite conductive plate and the ground plane; and a radio wave shield for blocking the propagation of the electric field, located on the top of the opposite conductive plate and made of a conductive or dielectric material. Using the inductance provided in the short-circuit section and the electrostatic capacitance formed by the ground plane and the opposite conductive plate, parallel resonance occurs at a predetermined target frequency.

[0010] According to the configuration described above, since the radio wave shielding body is designed to shield the radio waves on the top surface of the opposing conductive plate, it prevents the vertical electric field radiated from the edge of the opposing conductive plate from wrapping, looping, or twisting around its top surface. This means the radiation direction of the vertical electric field can be concentrated in the horizontal direction of the antenna. Consequently, the gain in the horizontal direction of the antenna can be maintained or improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] 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 of Fig. 1; Fig. 3 a diagram showing a basic configuration (that is, a comparison configuration) of a 0th order resonant antenna; Fig. 4 a diagram to explain the operating principle of the 0th order resonant antenna; Fig. 5 a diagram showing an intensity distribution of a vertical electric field in a comparison configuration; Fig. 6 a diagram to describe the effects of the present embodiment; Fig. 7 a diagram showing an increase in the horizontal direction of the antenna with a comparison configuration and the antenna device of the present embodiment; Fig. 8 a diagram showing a simulation result of the relationship between the thickness of the upper shielding body, the material and the reinforcement; Fig. 9 a diagram showing a modified example of the upper shielding body; Fig. 10 a diagram showing a modified example of the upper shielding body; Fig. 11 a diagram showing a modified example of the upper shielding body; Fig. 12 a diagram showing an example of a configuration in which an antenna device is mounted on a printed circuit board; Fig. 13 a view showing a cross-section along line XIII-XIII, which is in Fig. 12 is shown; Fig. 14 a diagram showing a configuration of an antenna device 1 including a housing; Fig. 15 a diagram showing a modified example of the case; Fig. 16 a diagram showing an antenna device in which a sealing material is filled into a housing; and Fig. 17 a diagram showing a modified example of the case. EXECUTIONAL FORMS FOR IMPLEMENTING THE INVENTION

[0012] A first 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.

[0013] 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.

[0014] 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.

[0015] Here, the operating frequency is, for example, 2.4 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 band from 2400 MHz to 2480 MHz (hereinafter referred to as the 2.4 GHz band). 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.For the sake of simplicity, a frequency band that enables an antenna device 1 to perform transmitting and receiving is hereinafter referred to as an operation band.

[0016] 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.

[0017] 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 feed line, 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 network, 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.

[0018] The following describes a specific structure of antenna device 1. As in Fig. 1 and Fig. As shown in Figure 2, the antenna device 1 comprises a ground plate 10, an opposing conductive plate 20, a support section 30, a short-circuit section 40, a power supply line 50, and an upper shielding body 60. For simplicity, each part is hereafter described as the top side of the antenna device 1, with the side on which the opposing conductive plate 20 is provided with respect to the ground plate 10. The direction from the opposing conductive plate 20 to the ground plate 10 corresponds to the downward direction for the antenna device 1.

[0019] The ground plane 10 is a conductive element in a plate shape and is made of a conductor such as copper. The plate shape is a thin film, similar to a metal foil. This means the ground plane 10 can be a pattern formed on the surface of a resin plate, such as a printed wiring board. The ground plane 10 is square. The length of one side of the ground plane 10 is electrically defined to a value corresponding to, for example, 1.1 times the wavelength of the radio wave at the target frequency (hereinafter referred to as the target wavelength). In this case, the electrical length is an effective length with respect to an electric stray field, wavelength shortening effect due to a dielectric substance, and 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.

[0020] The size of the ground plane 10 can be suitably modified. For example, the ground plane 10 can have a square shape, with one side electrically fixed to a value corresponding to a wavelength. The ground plane 10 can preferably have a size required for stable operation of the antenna device 1. Alternatively, the length of one side of the ground plane 10 can be electrically fixed to a value smaller than a wavelength (for example, one-third of the target wavelength). The wavelength of the 2.4 GHz radio wave (i.e., the target wavelength) in a vacuum and air is 125 mm.

[0021] Furthermore, the shape of the mass plate 10, viewed from above (hereinafter referred to as a planar shape), can be suitably modified. For example, the planar shape of the mass plate 10 is a square shape, whereas alternatively, as another aspect, the planar shape of the mass plate 10 can be a rectangular shape or another polygonal shape. Alternatively, it can be a circular shape (including an ellipse). The mass plate 10 can 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 when viewed from above.

[0022] The opposing conductive plate 20 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 20 is arranged to face the ground plate 10 by means of the support section 30. Similar to the ground plate 10, the opposing conductive plate 20 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 40 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.

[0023] By arranging the opposing conductive plate 20 and the ground plate 10 to face each other, a capacitance is formed according to the area of ​​the opposing conductive plate 20 and the distance between the opposing conductive plate 20 and the ground plate 10. The opposing conductive plate 20 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 20 can be appropriately designed to provide the desired capacitance (and thus operate at the target frequency). For example, the opposing conductive plate 20 is formed in a square shape with a side of 14 mm. Of course, the length of one side of the opposing conductive plate 20 can be suitably varied and can be, for example, 12.5 mm, 15 mm, 20 mm, 25 mm, or the like.

[0024] The opposite conductive plate 20 has, for example, a square shape, but alternatively, as another configuration, the planar shape of the opposite conductive plate 20 can be circular, regular octagonal, regular hexagonal, or the like. Furthermore, the opposite conductive plate 20 can have a rectangular or elongated shape. It may be preferred that the opposite conductive plate 20 has a line-symmetric shape (hereinafter referred to as a bidirectional line-symmetric shape), wherein each of two straight lines is orthogonal to each other and represents an axis of symmetry. The bidirectional line-symmetric shape refers 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. It may be preferred that the opposite conducting plate 20 is a point-symmetric figure such as a circle, a square, a rectangle, or a parallelogram.

[0025] The opposing conductive plate 20 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 20 may be partially or completely meandering. The bidirectional line-symmetric shape also includes a shape in which the edge section of the bidirectional line-symmetric shape is provided with irregularities. The same applies to the point-symmetric shape.

[0026] The support section 30 is a plate-shaped element for arranging the ground plate 10 and the opposing conductive plate 20 so that they face each other at a predetermined interval. The support section 30 is made using a dielectric material such as resin. A flame-retardant type 4 (so-called FR4) or the like can also be used as a material for the support section 30. As an example, the support section 30 is shown here made using FR4 with a relative dielectric constant of 4.3.

[0027] In the present embodiment, for example, the support section 30 is designed as a plate-shaped element with a thickness of 1.5 mm. The support section 30 corresponds to a support plate. The thickness H1 of the support section 30 corresponds to the distance between the ground plate 10 and the opposite conductive plate 20. By adjusting the thickness H1 of the support section 30, the distance between the opposite conductive plate 20 and the ground plate 10 can be adjusted. The specific value of the thickness H1 of the support section 30 can be suitably determined by simulations or experiments. The thickness H1 of the support section 30 can be 2.0 mm, 3.0 mm, or the like. The wavelength of the support section 30 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.

[0028] The shape of the support section 30 is not limited to a plate shape, as long as the support section 30 fulfills the function described above. The support section 30 can consist of several columns that support the mass plate 10 and the opposing conductive plate 20 such that they face each other at a predetermined interval. Furthermore, in the present embodiment, a configuration in which a resin fills the support section 30 is used between the mass plate 10 and the opposing conductive plate 20, although the present embodiment need not be limited to this. The space between the mass plate 10 and the opposing conductive plate 20 can be hollow or a vacuum. Furthermore, the structures illustrated 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 20, and a resin layer separating the conductor layers can be used as the carrier section 30.

[0029] The thickness H1 of the carrier section 30 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 20, which face each other.

[0030] The short-circuit section 40 is a conductive element that electrically connects the ground plate 10 and the opposite conductive plate 20. 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.

[0031] 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 20. 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.

[0032] The short-circuit section 40 is designed to be located at the center of the opposite conductive plate 20 (hereinafter referred to as the center of the conductive plate). The center of the conductive plate corresponds to the centroid of the opposite conductive plate 20. Since the opposite conductive plate 20 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 20. It should be noted that the position of the short-circuit section 40 does not always have to coincide exactly with the center of the opposite conductive plate 40. The short-circuit section 40 can deviate from the center of the conductive plate by several millimeters. The short-circuit section 40 can be located in a central region of the opposite conductive plate 20.The central region of the opposite conducting plate 20 refers to a region within the line connecting the points that internally divides the conducting plate from the center of the edge section in a ratio of 1:5. From another perspective, the central region corresponds to a region where concentric figures overlap and where the opposite conducting plate 20 is similarly reduced to 1 / 6.

[0033] The power supply line 50 is a microstrip line provided on the patch-side surface of the carrier section 30 to supply power to the opposite conductive plate 20. One end of the power supply line 50 is electrically connected to the center conductor of the coaxial cable, and the other end is electrically connected to the edge of the opposite conductive plate 20. The connection section between the power supply line 50 and the opposite conductive plate 20 corresponds to a power supply point for the opposite conductive plate 20. An electric current introduced into the power supply line 50 via the coaxial cable propagates to the opposite conductive plate 20, exciting and vibrating it.The point on the edge of the opposite conductive plate 20, which is connected to the power supply line 50, corresponds to the power supply point.

[0034] In this embodiment, a direct-connection power supply method is used for the power supply of the opposite conductive plate 20, in which the power supply line 50 is directly connected to the opposite conductive plate 20. Alternatively, the present embodiment need not be limited to this feature. As a further embodiment, a power supply method in which the power supply line 50 and the opposite conductive plate 20 are electromagnetically coupled can be used. The direct power supply method can be implemented using a conductive pin or a via. The position of the power supply point can be a position where the impedance matches or is matched. The power supply point can be located at any position, such as in the central region of the opposite conductive plate 20.

[0035] The upper shielding body 60 is made of a plate-shaped dielectric material and is arranged on the top surface of the opposing conductive plate 20. In the present embodiment, for example, the vertical and horizontal dimensions (in other words, the planar shape) of the upper shielding body 60 are configured to be the same as those of the support section 30. The thickness H2 of the upper shielding body 60 is, for example, 3 mm. The upper shielding body 60 is arranged on the opposing conductive plate 20 such that it covers the upper surface section of the opposing conductive plate 20 (in other words, is in contact with the plate 20).

[0036] The upper shielding body 60 is configured to prevent a vertical electric field, generated from an end section of the opposite conductive plate 20, from wrapping around the top surface of the opposite conductive plate 20, as described later. The upper shielding body 60 corresponds to a radio wave blocking body. Ideally, the blocking body is configured to reflect radio waves, although it need not be limited to this feature. A configuration that suppresses (in other words, inhibits) the propagation of radio waves corresponds to a configuration that shields the propagation of radio waves. It may be preferred that the upper shielding body 60 be configured to be in contact with the edge section of the opposite conductive plate 20 and to have a predetermined height.

[0037] Various dielectric materials such as resin, glass, and ceramics can be used as the material for the upper shielding body 60. For example, the upper shielding body 60 is made using a ceramic with a relative dielectric constant of 50 or higher. Alternatively, the upper shielding body 60 can be made of a ferroelectric substance such as barium titanate (BaTiO3) or lead zirconate titanate. The upper shielding body 60 can also be made of a conventional dielectric such as barium titanate (BaTiO2), titanium dioxide (TiO2), or calcium zirconate (CaZrO3). In this case, the upper shielding body 60 can be made using polycarbonate, ABS resin, or similar materials. Various resin materials such as urethane resin, epoxy resin, and silicon or silicone can also be used as the material for the upper shielding body 60.

[0038] If the dielectric loss factor of the upper shielding body 60 is high, the amount of radiated energy lost as heat increases. Therefore, it may be preferable for the upper shielding body 60 to be made of a material with a lower dielectric loss factor. Furthermore, the upper shielding body 60 acts to suppress the wrapping of the electric field as the dielectric constant increases. In other words, the higher the dielectric constant of the upper shielding body 60, the better the gain improvement effect in the horizontal direction of the antenna. Therefore, it is preferable for the material of the upper shielding body 60 to be made of a dielectric with a high dielectric constant.Furthermore, the upper shielding body 60 can be configured using a metal (i.e., a conductor) as described later as a modification. <Operationsprinzip der Resonanzantenne 0-ter Ordnung>

[0039] Next, the antenna device 1X is prepared as a comparison configuration (in other words, a basic configuration) of the 0th-order resonant antenna, and the operating principle of the 0th-order resonant antenna is described. The antenna device 1X corresponds to a comparison configuration for the antenna device 1 of the present embodiment. As in Fig. As shown in Figure 3, the antenna device 1X, as a basic 0th order resonant antenna, includes a ground plate 10, an opposing conductive plate 20, a carrier section 30, a short-circuit section 40, and a power supply line 50. That is, the antenna device 1X, as the comparison configuration, corresponds to the configuration in which the upper shielding body 60 is located away from the antenna device 1 of the present embodiment.

[0040] Although the basic operating principle of the zeroth-order resonant antenna is described here, the antenna device 1 of the present embodiment (hereinafter also referred to as a proposed configuration) operates according to the same principle. That is, the description of antenna device 1X can be generally applied to antenna device 1. Furthermore, the operation when the comparison configuration transmits (i.e., radiates) radio waves and the operation when radio waves are received are reversible. Therefore, only the operation when radio waves are radiated is described here, and the description of the operation when radio waves are received is omitted.

[0041] The zeroth-order resonant antenna, disclosed as antenna device 1X, generally operates by LC parallel resonance of the capacitance formed between the ground plate 10 and the opposite conductive plate 20 and the inductance provided in the short-circuit section 40. Specific examples are as follows. The opposite conductive plate 20 in 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 20, and the area of ​​the opposite conductive plate 20 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.Accordingly, a parallel resonance (so-called LC parallel resonance) occurs due to an energy exchange between the inductor and the capacitor, and an electric field perpendicular to the ground plate 10 (and to the opposite conducting plate 20) is generated between the ground plate 10 and the opposite conducting plate 20. This vertical electric field propagates from the short-circuit section 40 towards the edge section of the opposite conducting plate 20, and at the edge section of the opposite conducting plate 20, the vertical electric field is vertically polarized and propagates in space. The vertically polarized wave is a radio wave in which the oscillation direction of the electric field is perpendicular to the ground plate 10 and the opposite conducting plate 20.

[0042] Since the propagation direction of the vertical electric field is symmetrical with respect to the short-circuit section 40, as in Fig. As shown in Figure 4, it has the same gain in all directions in the horizontal plane of the antenna. In other words, at the target frequency, antenna device 1 and antenna device 1X have a directivity in all directions (i.e., a horizontal antenna direction) from the central region towards the edge of the opposite conductive plate 20. Therefore, when the ground plate 10 is oriented horizontally, antenna device 1 has a directivity in the horizontal plane direction. The horizontal plane of the antenna refers to a plane parallel to the ground plate 10 and the opposite conductive plate 20. The horizontal direction of the antenna refers to the direction from the center of the opposite conductive plate 20 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 20. The horizontal antenna direction corresponds to a transverse direction (e.g., lateral direction) of the antenna device.

[0043] Since the current flowing through the opposite conductive plate 20 is symmetrical about the short-circuit section 40, the radio waves in the antenna's vertical direction, generated by the current flowing in a specific cross-section, are canceled out by the radio waves generated by the current flowing in the opposite direction. Therefore, it does not radiate any radio waves in the antenna's vertical direction. <Wirkung von Antennenvorrichtung 1 (hauptsächlich Anordnung von oberem Abschirmungskörper)>

[0044] Next, the effect / advantage of this embodiment compared to the comparison configuration will be described. When the inventors verified the operating mode of the comparison configuration as a possible zero-order resonant antenna, the winding / twisting structure in the comparison configuration, as shown in Fig. As shown in Figure 5, the vertical electric field around the top of the opposite conductive plate 20 and the radiation intensity (i.e., gain) of the radio wave in the horizontal direction of the antenna are affected. It was also found that the above trend becomes more pronounced when the distance H1 between the ground plate 10 and the opposite conductive plate 20 decreases. That is, in the comparison configuration, the smaller the distance H1 between the ground plate 10 and the opposite conductive plate 20, the lower the gain in the horizontal direction of the antenna.

[0045] In response to such a difficulty, the configuration of the present embodiment includes a dielectric element that covers the edge of the opposing conductive plate 20 as the upper shielding body 60. Since the upper shielding body 60 is configured using a dielectric element with a predetermined dielectric constant, it is possible to prevent the vertical electric field from wrapping or twisting around the top of the opposing conductive plate 20, as shown in Fig. 6 is shown. Accordingly, as in Fig. As shown in Figure 7, the gain in the horizontal direction of the antenna can be increased.

[0046] As described above, in addition to ceramic, a resin, a conductor or the like can be used as the material of the upper shielding body 60. Fig. Figure 8 is a diagram showing the test results of the relationship between the material of the upper shielding body 60, the thickness H2, and the gain in the horizontal direction of the antenna. If the upper shielding body 60 is made of ceramic, as in Fig. As shown in Figure 8, a gain of approximately 2 dB or more can be achieved by setting the thickness H2 to approximately 3 mm. Furthermore, if the thickness H2 of any material is increased, the gain in the horizontal direction of the antenna approaches the theoretical value of the gain of a 1 / 4-wavelength monopole antenna. The theoretical value of the gain of the 1 / 4-wavelength monopole antenna is 5.16 dBi.

[0047] Furthermore, if a perfect conductor (i.e., metal) or ceramic is used as the material of the upper shielding body 60, it is also evident that a gain close to that of the monopole antenna can be achieved by setting the thickness H2 to 18 mm. Furthermore, since the wavelength of 2.4 GHz in air is 125 mm, the height of the 1 / 4-wavelength monopole antenna must be approximately 31.3 mm. On the other hand, according to the configuration of the present disclosure, a gain equivalent to that of a 1 / 4-wavelength monopole antenna is obtained at a height of approximately 18 mm (i.e., approximately 60% of the height of a 1 / 4-wavelength monopole antenna). That is, according to the configuration of the present embodiment, the height of the antenna device 1 can be reduced. The configuration in which the thickness H2 is 18 mm is closer to a block shape than a plate shape.Since the difference between the plate shape and the block shape is ambiguous, the plate shape here also includes the block shape.

[0048] The embodiment of the present disclosure has been described above. The present disclosure is not intended to be limited to the embodiment described above, but has a technical scope that covers various modifications, which are described below, and can likewise be implemented with various modifications, which are not described below, within a scope that does not depart from the purpose of the present disclosure. For example, various modifications, which will be described below, can be implemented in suitable combinations within a scope that does not cause any technical inconsistency. [Modification 1]

[0049] The upper shielding body 60 can be made of metal (i.e., a conductor), as in Fig. Figure 9 shows that this configuration corresponds to one in which a conductor is positioned at the end of the opposite conductive plate 20. Since the conductor reflects radio waves, it suppresses the wrapping or twisting (in other words, propagation) of radio waves more than the dielectric material. Therefore, when the upper shielding body 60 is implemented using a conductor, the gain in the horizontal direction of the antenna can be increased compared to the configuration in which the upper shielding body 60 is implemented using a dielectric material.

[0050] Furthermore, according to the configuration in which the upper shielding body 60 is made of a conductor, a current flows on the vertical surface of the upper shielding body 60. Since the current flowing in the vertical plane of the upper shielding body 60 causes the vertically polarized waves to be radiated in the horizontal direction of the antenna, the gain in the horizontal direction of the antenna can be further improved compared to the embodiment described above.

[0051] However, the configuration in which the upper shielding body 60 is implemented using a conductor is inferior in terms of robustness with respect to dimensional errors and the like compared to the configuration in which the upper shielding body 60 is implemented using a dielectric material such as ceramic. For example, if the metallic upper shielding body 60 protrudes towards the outside of the opposite conductive plate 20, the target frequency can change significantly. This is because the section of the metallic upper shielding body 60 that protrudes from the opposite conductive plate 20 forms a capacitance with the ground plate 10.For example, in a configuration where the distance between the ground plate 10 and the opposite conductive plate 20 is 1.5 mm and the relative dielectric constant of the carrier section 30 is 4.3, if the upper shielding body 60 protrudes 1 mm from the edge section of the opposite conductive plate 20, the capacitance contributing to the parallel resonance increases and the operating frequency shifts towards the low-frequency side by almost 1 GHz. Specifically, the operating frequency shifts from 2.4 GHz to 1.5 GHz.

[0052] On the other hand, according to the configuration in which the upper shielding body 60 is made of a dielectric material, even if the upper shielding body 60 protrudes approximately 1 mm outside the opposite conductive plate 20, the amount of capacitance increase is negligible. Therefore, according to the configuration in which the upper shielding body 60 is made of a dielectric material such as ceramic, it is possible to suppress the influence of the assembly error and the dimensional error of the upper shielding body 60 on the operating frequency.

[0053] The metallic upper shielding body 60 can be formed integrally with the opposing conductive plate 20. Furthermore, it is preferred that the upper shielding body 60 is in contact with the opposing conductive plate 20, and alternatively, in a further embodiment, the upper shielding body 60 is arranged on the upper surface of the opposing conductive plate 20 at a predetermined interval. The upper shielding body 60 can preferably be arranged on the upper surface of the edge section of the opposing conductive plate 20 such that the distance from the edge section is 1 / 10 of the wavelength or less.

[0054] Furthermore, it may be preferred that the vertical surface of the upper shielding body 60 is formed at a position where its vertical surface is in contact with the edge section of the opposite conductive plate 20, whereas alternatively, in a further embodiment, the vertical surface of the upper shielding body 60 has its vertical surface at a position within a predetermined distance (for example, by several millimeters) from the edge of the opposite conductive plate 20. That is, the planar shape of the upper shielding body 60 can be smaller than that of the opposite conductive plate 20. [Second modification]

[0055] If the upper shielding body 60 is made of a conductor, it can be formed on the top of the edge section of the opposite conductive plate 20. The conductor forming the upper shielding body 60 does not always have to be located above the center region of the opposite conductive plate 20. For example, as in Fig. As shown in Figure 10, the conductor can be configured as the upper shielding body 60 in a box shape in which the upper surface is open. The upper shielding body 60 corresponds to a configuration including a shielding body base section 61 arranged on the upper surface of the opposite conductive plate 20, and an upright section 62 erect on the edge section of the opposite conductive plate 20. The shielding base section 61 corresponds to a configuration in which it is arranged to face the opposite conductive plate 20. The shielding base section 61 can be configured to have the same dimensions as the opposite conductive plate 20. The upright section 62 can be inclined at 15 degrees with respect to the opposite conductive plate 20.The term "upright" also includes a mode in which the object is inclined by approximately 15 degrees from a truly right-angled state.

[0056] The metallic upper shielding body 60 only needs to have one upright section 62, and the shielding body bottom section 61 need not be an essential element. In the configuration where the shielding bottom section 61 of the upper shielding body 60 is located away from the upper shielding body 60 that is in Fig. As shown in Figure 10, the configuration corresponds to the frame-shaped / tubular configuration with a predetermined thickness H2 (in other words, height or depth) to position the upper shielding body 60 along the edge of the opposite conductive plate 20. Furthermore, the metallic upper shielding body 60 can be formed integrally with the opposite conductive plate 20. The opposite conductive plate 20 can also be used as the shielding bottom section 61. The metallic upright section 62 provides a function for extending the radiation range of the vertical electric field.

[0057] The configuration disclosed as the second modification can also be applied to the embodiment described above. For example, as in Fig. As shown in Figure 11, the ceramic / resin can be configured as the upper shielding body 60 in a flat box shape (in other words, flat bottom) with an open top surface. Dielectrics are not as effective as metals at shielding radio waves. Therefore, it may be preferable for the upright section 62, configured using a dielectric material, to have a thickness and height sufficient to block the wrapping or twisting of radio waves. For example, the dielectric material of the upright section 62 may preferably have a thickness of at least approximately 2 mm to 5 mm. The specific thickness and height of the upright section 62, made of a dielectric material, can be suitably designed based on simulation or the like.The upper shielding body 60 can fulfill the aforementioned function, and its shape need not be limited to a plate shape. The upper shielding body 60 can have a flat plate shape, a block shape, a box shape, or a tube shape. [Third modified example]

[0058] When the length (in other words, the width) of the ground plate 10 in a particular direction becomes one wavelength or less (especially 0.7 wavelengths or less), an electric field wraps itself around beneath the ground plate 10, causing a decrease in gain. For example, as in Fig. As shown in Figure 12, if the ground plate 10 has a rectangular shape and the length of the shorter side is electrically 0.5 of the wavelength, an electric field can wrap or twist around the underside of the ground plate 10. Given such circumstances, if the length of the ground plate 10 is configured in a certain direction to be 1 wavelength or less (in particular 0.7 wavelengths or less), as in Figure 12, the following applies: Fig. As shown in Figure 13, it may be preferred that a dielectric element or a conductor be added to block the propagation of the electric field as the lower shielding body 70, which is located below the ground plate 10.

[0059] Similar to the upper shielding body 60, the lower shielding body 70 is configured to suppress the wrapping or winding of radio waves. The lower shielding body 70 can preferably be configured to cover the entire underside surface of the ground plate 10. By positioning the lower shielding body 70 on the underside of the ground plate 10, it is possible to reduce the probability that the gain in the horizontal direction of the antenna will be impaired due to the electric field wrapping or winding around the underside of the ground plate 10. For the material and shape of the lower shielding body 70, reference is made to the description of the upper shielding body 60.

[0060] The lower shielding body 70 can be in contact with the grounding plate 10 or can be arranged to face it at a predetermined interval. The case described above is rectangular, but alternatively, the technical idea disclosed as this modification can be applied to the case where the grounding plate 10 is elliptical, circular, or regularly polygonal. For example, if the grounding plate 10 has an elliptical shape, it may be preferred that the lower shielding body 70 be arranged when the length of the minor axis of the grounding plate 10 is one wavelength or less.If the length in the direction in which the length becomes the smallest among the lengths in the different directions passing through the point of the ground plate 10 that overlaps the center of the opposite conductive plate is one wavelength or less, it may be preferred that the lower shielding body 70 be arranged.

[0061] Reference numbers 81 and 82, which are in Fig. Figure 12 shows electronic components for implementing the modulation / demodulation circuit. The printed circuit board on which the opposing conductive plate 20, the ground plate 10, the modulation / demodulation circuit, and the like are mounted corresponds to the carrier section 30 described above. Hereinafter, the printed circuit board on which the opposing conductive plate 20, the ground plate 10, the modulation / demodulation circuit, and the like are mounted is referred to as a printed circuit board 100. The printed circuit board 100 corresponds to a module that provides a function as an antenna device 1. [Fourth modified example]

[0062] As in Fig. As shown in Figure 14, the antenna device 1 can include a housing 90 for receiving the printed circuit board 100. The housing 90 is formed by combining, for example, an upper housing and a lower housing, which are vertically separable. The housing 90 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 material for the housing 90. The housing 90 includes a housing bottom section 91, a housing side wall section 92, and a housing top plate section 93. The housing bottom section 91 is configured to provide the base of the housing 90. The housing bottom section 91 is formed in a flat plate shape.In the housing 90, the circuit board 100 is arranged such that the ground plane 10 faces the housing bottom section 91. The distance between the housing bottom section 91 and the ground plane 10 can preferably be set to λ / 25 or less.

[0063] The housing side wall section 92 is configured to provide the lateral surface of the housing 90 and is positioned upwards from the edge section of the housing bottom section 91. The height of the housing side wall section 92 is designed such that, for example, the distance between the inner surface of the housing top plate section 93 and the opposite conductive plate 20 is λ / 25 or less. The housing top plate section 93 is configured to provide an upper surface section of the housing 90. The housing top plate section 93 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 93. The housing top plate section 93 is configured such that its inner surface faces the upper surface of the support section 30 (and thus the opposite conductive plate 20).

[0064] If the housing top plate section 93 is arranged near the opposite conductive plate 20 as in the configuration described above, the housing top plate section 93 can also function as the upper shielding body 60 mentioned above. The expression "near the opposite conductive plate 20" refers, for example, to a region where the distance from the opposite conductive plate 20 is electrically 1 / 25 or less of the target wavelength. The configuration described above corresponds to a configuration in which the housing top plate section 93 is used as the upper shielding body 60. Furthermore, if the housing bottom plate section 91 is arranged near the ground plate 10 as in the configuration described above, the housing bottom plate section 91 can also function as the lower shielding body 70 mentioned above.The expression “near the ground plate 10” means, for example, a region where the distance from the ground plate 10 is electrically 1 / 25 or less of the target wavelength. The lower shielding body 70 can be implemented using the housing bottom section 91.

[0065] The housing 90 can be configured with an upper rib 931 for supporting and positioning the printed circuit board 100. The upper rib 931 has a convex structure extending downwards from a predetermined position on the inner surface of the housing top plate section 93. The upper rib 931 is integral with the housing 90. The upper rib 931 regulates the position of the support section 30 within the housing 90. As shown in Fig. As shown in Figure 15, the upper rib 931 can preferably be configured to be in contact with the edge section of the opposite conductive plate 20. In the configuration where the upper rib 931 is arranged to be in contact with the edge section of the opposite conductive plate 20, the upper rib 931 functions as the upper shielding body 60 (in particular, the upright section 62). Therefore, the gain in the horizontal direction of the antenna can be increased compared to the configuration without the upper rib 931. The upper rib 931, configured to be in contact with the edge section of the opposite conductive plate 20, corresponds to the edge contact section. A metal pattern, such as a copper foil, can be arranged on the vertical surface (i.e., the outer surface) of the upper rib 931 that is connected to the edge of the opposite conductive plate 20.According to this configuration, essentially the same effect can be achieved as in the configuration in which the upright section 62, which is made of a conductor, is added.

[0066] A lower rib 911 for supporting and positioning the printed circuit board 100 can be formed on the housing base section 91. The lower rib 911 has a convex structure that extends integrally from a predetermined position of the housing base section 91 to the top surface. The lower rib 911 serves to regulate the position of the printed circuit board 100 within the housing 90. The lower rib 911 is configured such that the distance between the ground plane 10 and the housing base section 91 is λ / 25 or less. The lower rib 911 can preferably be configured to be in contact with the edge section of the ground plane 10. In this configuration, the lower rib 911 also functions as the lower shielding body 70. Consequently, the gain in the horizontal direction of the antenna can be increased compared to the configuration in which the lower rib 911 is not formed. The lower rib 911 corresponds to the lower support section.A metal pattern such as a copper foil can be arranged on the vertical surface (that is, the outer surface) of the lower rib 911, which is connected to the edge of the mass plate 10. [Fifth modification]

[0067] As in Fig. As illustrated in Figure 12, the antenna device 1, including the opposing conductive plate 20 and the like, can be integrally formed on the printed circuit board 100 on which the modulation / demodulation circuit and the like are mounted. The printed circuit board 100 is housed in a casing 90 and is used for waterproofing and the like.

[0068] If the antenna device 1 includes the housing 90, it may be preferable to fill the space between the housing 90 and the circuit board 100 with a sealing material 110 such as silicone, as shown in Fig. Figure 16 is shown only by reference numerals. The sealing material 110 corresponds to a sealing element. In Fig. In Figure 16, the hatching of the sealing material 110 is not shown in order to maintain the visibility of the drawing. The same applies to Fig. 17. According to the configuration in which the housing 90 is filled with the sealing material 110, the sealing material 110 (that is, the section defined by 110a in Fig. (as shown in Figure 16), which is located above the opposite conductive plate 20, functions as the upper shielding body 60. Even when the sealing material 110 is filled on the top of the opposite conductive plate 20, the housing top plate section 93 can function as part of the upper shielding body 60. The upper shielding body 60 can be realized by combining the sealing material 110 located above the opposite conductive plate 20 and the housing top plate section 93. Furthermore, depending on the configuration in which the sealing material 110 is filled in the housing 90, water tightness, dust tightness, and vibration resistance can be improved. From another point of view, such a configuration is equivalent to a configuration in which the sealing material 110, for watertight purposes, also provides the upper shielding body 60, similar to silicone.

[0069] Furthermore, the sealing material 110 (that is, the section defined by 110b in Fig. (as shown in Figure 16), which is located below the ground plate 10, functions as the lower shielding body 70, which is referenced in modified Example 3. That is, according to the configuration in which the sealing material 110 is filled into the housing 90, the sealing material 110 functions as the upper shielding body 60 and the lower shielding body 70, so that both the watertightness property and the gain improvement in the horizontal direction of the antenna can be achieved. Even when the sealing material 110a is filled, the housing bottom section 91 can function as part of the lower shielding body 70. The configuration in which the sealing material 110 is filled into the housing 90 corresponds to the configuration in which the lower shielding body 70 is realized by the combination of the sealing material 110, which is located below the ground plate 10, and the housing bottom section 91.

[0070] Urethane resin, such as a polyurethane prepolymer, can be used as the sealing material 110. Various other materials, such as epoxy resin and silicone resin, can also be used as the sealing material 110. The configuration disclosed as modification 5 can be implemented in combination with modification 4. In particular, the housing 90 of the antenna device 1, which is located in Fig. Figure 16 shows an upper rib 931 and a lower rib 911 which are designed to be in contact with the edge section of the opposite conductive plate 20.

[0071] In general, the printed circuit board (PCB) 100 contains electronic components 81 and 82, such as IC chips and three-dimensional structures like connectors. Furthermore, a space is usually provided between the PCB and the housing so that the three-dimensional structures do not interfere with the housing 90. Therefore, a separation can occur between the inner surface of the housing top plate section 93 and the opposite conductive plate 20. The greater the distance between the inner surface of the housing top plate section 93 and the opposite conductive plate 20, the more difficult it is for the housing top plate section 93 to function as the upper shielding body 60.

[0072] The configuration disclosed as the present modification 5 is implemented taking into account the aforementioned difficulties, and the directivity in the horizontal direction of the antenna is improved by filling the interior of the housing 90 with a sealing material 110 such as silicon or silicone. As described in the description of the upper shielding body 60, a material with a high relative permittivity and a low dielectric loss factor may be preferred as the sealing material. 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.

[0073] In the case of housing 90, the housing bottom section 91 can be omitted, as shown in (A) of Fig. 17 is shown. Furthermore, housing 90 can be used, as shown in (B) of Fig.As shown in Figure 17, the housing top plate section 93 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 110 can preferably be implemented using a resin that maintains strength in the range assumed to be the ambient temperature 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.

[0074] Although the present disclosure has been described according to embodiments, it is evident that the present disclosure is not limited to such embodiments or structures. The present disclosure also includes various modified examples and modifications within a unified scope. Furthermore, various combinations and embodiments, as well as other combinations and designs containing only one element or more or fewer than these elements, also fall within the spirit and scope of the present disclosure.

Claims

[1] Antenna device comprising: a ground plate (10) made from a conductor with a flat plate shape; an opposing conductive plate (20) 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 which is electrically connected to a power supply line; a short-circuit section (40) that electrically connects the opposite conductive plate (20) and the ground plate (10); and a radio wave shielding body (60) for shielding against the propagation of an electric field, which is arranged on a top side of the opposite conductive plate (20) and is made of a conductor or a dielectric material, 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 (20), and wherein the ground plate (10) and the opposite conductive plate (20) are arranged on a carrier plate (30) made of resin material, the antenna device further comprising: a resin housing (90) for receiving the carrier plate (30), wherein: the resin housing (90) includes a housing top plate section (93) which is arranged above the opposite conductive plate (20); and the housing top plate section (93) includes an edge contact section (931) which contacts an edge section of the opposite conductive plate (20). [2] Antenna device according to claim 1, wherein: a distance between the radio wave shielding body (60), which is located above an edge section of the opposite conductive plate (20), and the edge section of the opposite conductive plate (20) is 1 / 25 or less of a wavelength at the target frequency. [3] Antenna device according to claim 1 or 2, wherein: the radio wave shielding body (60) is arranged to contact an upper surface of an edge section of the opposite conductive plate (20). [4] Antenna device according to one of claims 1 or 3, wherein: a distance between the carrier plate (30) and the housing top plate section (93) is 1 / 25 or less of a wavelength at the target frequency so that the housing top plate section (93) functions as the radio wave shielding body (60). [5] Antenna device according to claim 1 or 4, wherein: the resin housing (90) includes a housing base (91) which is opposite the mass plate (10) with a predetermined distance between them; and the housing base (91) includes a lower support section (911) which contacts the edge section of the ground plate (10). [6] Antenna device according to one of claims 1, 4 or 5, wherein: a resin material with a relative dielectric constant of 2.0 or more is filled as a sealing element (110) between the carrier plate (30) and the resin housing (90).

Images