Antenna device

Abstract

An antenna device (10) includes a main plate (20), a ground plate (30), a patch (40), a power feeder (50), a short-circuit portion (60), and an additional conductor (80). The main plate is made of a dielectric material. The ground plate is disposed at the main plate and provides a ground potential. The patch is disposed at the main plate to face the ground plate in a thickness direction of the main plate. The power feeder is disposed at the main plate and electrically connected to the patch. The short-circuit portion is a via conductor disposed at the main plate and electrically connected to the patch and the ground plate. The additional conductor is disposed at the main plate so that a side surface of the additional conductor faces a side surface of the patch and has the same potential as the ground potential of the ground plate.

Description

TECHNICAL FIELD

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

[0002] JP 2018-61137A describes an antenna device including a zeroth-order resonant antenna. SUMMARY

[0003] JP 2018-61137A describes that an additional conductor is disposed on the side opposite to a ground plate with respect to a patch in a zeroth-order antenna. In this structure, a capacitor formed between the patch and the additional conductor is connected in parallel to a capacitor formed between the patch and the ground plate. Therefore, the capacitance value of the capacitor in the LC parallel resonant circuit becomes larger compared to the structure without the additional conductor, and the resonant frequency shifts to the lower frequency side. In order to obtain a predetermined resonant frequency on the higher frequency side, it can be necessary to reduce the area of the patch, for example.

[0004] A zeroth-order resonant antenna employs a main plate made of a material. Conductors such as a ground plate, a patch, and a short-circuit portion can be disposed at the main plate. The short-circuit portion includes a via conductor arranged on the main plate. Due to limitations by, for example, the main plate thickness and the via diameter, it is difficult to improve the reflection characteristics. Therefore, there is a demand for further improvement of the antenna device.

[0005] An object of the present disclosure is to provide an antenna device for enhancing the reflection characteristics while shifting the resonant frequency to the higher frequency side without changing the physical size of the patch.

[0006] According to an aspect of the present disclosure, an antenna device includes a main plate, a ground plate, a patch, a power feeder, a shorting part, and an additional conductor. The main plate is made of a dielectric material. The ground plate is disposed at the main plate and provides a ground potential. The patch is disposed at the main plate to face the ground plate in a thickness direction of the main plate. The power feeder is disposed at the main plate and electrically connected to the patch. The shorting part is a via conductor disposed at the main plate and electrically connected to the patch and the ground plate. The additional conductor is disposed at the main plate such that a side surface of the additional conductor faces a side surface of the patch and has the same potential as the ground potential of the ground plate. The patch includes an outer surface, at least one slit, and an inner surface. The outer surface defines an outer contour of the patch, and the outer surface is a side surface of the patch. The slit is open to a position away from an outer surface portion at the outer surface where the power feeder is electrically connected. The inner surface defines the slit, and the inner surface is a side surface of the patch. The additional conductor includes a base portion, an insertion portion, and a connection portion. The base portion extends in an extension direction along the outer surface of the patch and is disposed to face the outer surface around an aperture of the slit. The insertion portion is connected to the base portion and is disposed within the slit to face the inner surface of the patch. The connection portion extends from the base portion and electrically connects the ground plate and the additional conductor.

[0007] According to the above-described antenna device, a capacitor is formed at a portion where the base portion of the additional conductor and the outer surface of the patch face each other. The connection portion of the additional conductor includes an inductor. The capacitor and the inductor shift a resonance frequency to a higher frequency side. Even if the area of the patch is not reduced, the resonance frequency can be shifted to a higher frequency side relative to a structure that does not have the additional conductor.

[0008] A capacitor is formed at a portion where the insertion portion of the additional conductor faces the inner surface of the patch. This capacitor enhances a reflection characteristic. As a result, the resonance frequency can be shifted to a higher resonance frequency side while enhancing the reflection characteristic without changing the physical size of the patch. BRIEF DESCRIPTION OF DRAWINGS

[0009] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0010] Figure 1 is a plan view showing an antenna device according to a first embodiment;

[0011] Figure 2 is a cross-sectional view taken along Figure 1 line II-II;

[0012] Figure 3 is a cross-sectional view taken alongFigure 1 a sectional view taken along line III-III of

[0013] Figure 4 a sectional view taken along line IV-IV of Figure 1

[0014] Figure 5 a schematic view of a reference example;

[0015] Figure 6 a schematic view of Figure 1

[0016] Figure 7 a schematic view of a first embodiment;

[0017] Figure 8 showing a reflection characteristic;

[0018] Figure 9 showing a radiation characteristic of the first reference example;

[0019] Figure 10 showing a radiation characteristic of the second reference example;

[0020] Figure 11 showing a radiation characteristic of the first embodiment;

[0021] Figure 12 showing a relationship between a position of a connecting portion and a reflection characteristic;

[0022] Figure 13 showing an arrangement of a connecting portion;

[0023] Figure 14 a plan view showing a modification example;

[0024] Figure 15 a plan view showing a modification example;

[0025] Figure 16 a plan view showing a modification example;

[0026] Figure 17 a schematic view of Figure 15

[0027] Figure 18 a schematic view of Figure 15

[0028] a plan view showing a modification example; Figure 19

[0029] a plan view showing a modification example; Figure 20

[0030] Figure 21 ​​​​is a plan view showing a modification example;

[0031] Figure 22 is a plan view showing a modification example;

[0032] Figure 23 is a plan view showing an antenna device according to a second embodiment;

[0033] Figure 24 is Figure 23 is a schematic view of a region XXIV enlarged;

[0034] Figure 25 shows an equivalent circuit diagram;

[0035] Figure 26 shows a reflection characteristic;

[0036] Figure 27 shows a radiation characteristic;

[0037] Figure 28 is a plan view showing a modification example; and

[0038] Figure 29 is a plan view showing a modification example. DETAILED DESCRIPTION

[0039] A plurality of embodiments will be described below with reference to the accompanying drawings. In each of the embodiments, the same reference numerals are assigned to corresponding elements, and thus repeated description can be omitted. When a part of a feature in each of the embodiments is explained, the remaining part of the feature can be provided by a feature in another previously explained embodiment. In addition, a combination of configurations explicitly shown in the description of the corresponding embodiment and configurations of the plurality of embodiments can be partially combined, even if the configurations are not explicitly shown, as long as there is no particular difficulty in the combination.

[0040] (First Embodiment)

[0041] The antenna device according to the present embodiment transmits and / or receives radio waves of a predetermined operation frequency. The antenna device transmits and / or receives radio waves in a frequency band used in short distance wireless communication. The operation frequency of the present embodiment is 2.44 GHz. The operation frequency can be appropriately designed, and can be other frequencies (for example, 5 GHz). Hereinafter, relative is a state in which two objects face each other at a predetermined distance.

[0042] (Structure of Antenna Device)

[0043] First, the structure of the antenna device will be described below with reference to Figures 1 to 4 Figure 1 is a plan view of the antenna device according to the present embodiment from the board thickness direction of the board viewed from the patch. Figure 2 is a plan view of the antenna device according to the present embodiment from the board thickness direction of the board viewed from the patch.​Figure 1 a cross-sectional view taken along line II-II of FIG. 10. Figure 3 is a cross-sectional view taken along line III-III of FIG. 11. Figure 1 is a cross-sectional view taken along line III-III of FIG. 11. Figure 4 is a cross-sectional view taken along line IV-IV of FIG. 12. Figure 1 is a cross-sectional view taken along line IV-IV of FIG. 12.

[0044] As shown in FIG. 1, the antenna device 10 includes a main plate 20, a ground plate 30, a patch 40, a power feeder 50, and a short-circuit portion 60. The antenna device 10 is configured on a printed circuit board. In other words, the antenna is mounted on the printed circuit board. The main plate 20 is, for example, an insulating base material of the printed circuit board. The main plate 20 can also be referred to as a substrate or a main plate. The elements other than the main plate 20, that is, the ground plate 30, the patch 40, the power feeder 50, and the short-circuit portion 60 are conductor elements of the printed circuit board. The ground plate 30 can also be referred to as a ground plate or a bottom plate. The patch 40 can also be referred to as a patch portion. The power feeder 50 can also be referred to as a feeding line, a power supply line, or a power source line. Figures 1 to 4 Hereinafter, a plate thickness direction of the main plate 20 is defined as a Z direction, and one direction orthogonal to the Z direction is defined as an X direction. A direction orthogonal to both the Z direction and the X direction is defined as a Y direction. Unless otherwise specified, a shape observed in a plane from the Z direction, that is, a shape along an XY plane defined by the X and Y directions is referred to as a planar shape.

[0045] The main plate 20 is made of a dielectric material such as resin. By using the main plate 20, a wavelength shortening effect of the dielectric material can be expected. As the main plate 20, for example, a member made of only resin can be employed, or a combination of resin and glass cloth, non-woven fabric, or the like can be employed. The main plate 20 functions as a holding portion that holds the ground plate 30 and the patch 40 in a predetermined positional relationship.

[0046] The main plate 20 includes a main surface 20a and a rear surface 20b, the rear surface 20b being a surface opposite to the main surface 20a in the Z direction. In the present embodiment, the ground plate 30 is disposed at the main surface 20a of the main plate 20, and the patch 40 and the power feeder 50 are disposed at the rear surface 20b of the main plate 20. Depending on the thickness of the main plate 20, the relative distance between the ground plate 30 and the patch 40 in the Z direction and the length of the short-circuit portion 60 can be adjusted. The main plate 20 can have a single-layer structure or a multi-layer structure.

[0047]

[0048] ​The ground plate 30 is connected to a feeder circuit (not shown) to provide a ground potential of the antenna device 10. The ground plate 30 provides the ground potential by an electrical connection, for example, an outer conductor of a coaxial cable. The ground plate 30 is a flat plate-shaped conductor made of copper or the like. A direction perpendicular to a plate face of the ground plate 30 is also substantially parallel to the Z direction. In a plan view, an area of the ground plate 30 is larger than an area of the patch 40. The ground plate 30 has a size including the entire patch 40. The ground plate 30 can have a size required for stable operation of the antenna device (i.e., a zeroth-order resonant antenna).

[0049] The ground plate 30 of the present embodiment has a substantially rectangular planar shape. A length of each side of the ground plate 30 is, for example, one or more times a wavelength of a radio wave of an operating frequency, i.e., one wavelength or more. As described above, the ground plate 30 is disposed at the main surface 20a of the main plate 20. The ground plate 30 is formed by patterning a metal foil disposed at the main surface 20a of the main plate 20. The planar shape of the ground plate 30 can be changed as appropriate. In the present embodiment, the planar shape of the ground plate 30 is exemplified by a rectangle, but as another configuration, the planar shape of the ground plate 30 can be a square or other polygon. Further, the planar shape of the ground plate 30 can be a circle (including an ellipse). The ground plate 30 can be formed to have a size larger than a circle having a diameter of one wavelength.

[0050] The patch 40 is a conductor made of copper or the like. The patch 40 is a conductor disposed to face the ground plate 30 so that the ground plate 30 and the patch 40 have a predetermined distance in the Z direction. The patch 40 can also be referred to as a radiating element. In a plan view, the entire patch 40 overlaps the ground plate 30. That is, the entire plate surface (lower surface) of the patch 40 faces the ground plate 30 in the Z direction. The patch 40 is disposed substantially parallel to the ground plate 30. Substantially parallel is not limited to complete parallel. For example, the patch 40 can be inclined by several degrees to ten degrees with respect to the ground plate 30.

[0051] As described above, the patch 40 according to the present embodiment is disposed at the rear surface 20b of the main plate 20. The patch 40 is formed by patterning a metal foil disposed at the rear surface 20b of the main plate 20. The patch 40 has a substantially square basic shape. The patch 40 has a substantially H-shaped shape by providing two slits 41, which will be described later, in the substantially square shape. The basic shape is an outer contour of the patch 40 in a plan view. The patch 40 has four sides defining the outer contour in the plan view. The patch 40 includes a power feeding side 40a, adjacent sides 40b, 40c, and an opposite side 40d. The power feeding side 40a is electrically connected to the power feeder 50. The adjacent sides 40b, 40c connect the power feeding side 40a. The opposite side 40d is located at a position opposite to the power feeding side 40a. The power feeding side 40a and the opposite side 40d are substantially parallel in the Y direction. The adjacent sides 40b, 40c are substantially parallel in the X direction.

[0052] The patch 40 and the ground plate 30 are disposed to face each other to form an electrostatic capacitor in accordance with an area of the patch 40 and a distance between the patch 40 and the ground plate 30. The patch 40 is formed to have a size to form a capacitance or a capacitor that resonates in parallel with an inductance of the short-circuit portion 60 at a target frequency. The area of the patch 40 is appropriately designed to provide a desired capacitance and thus operate at an operating frequency.

[0053] In the present embodiment, a basic shape of the patch 40, that is, an outer contour of the patch 40 is exemplified by a square, but as another configuration, a planar shape of the patch 40 can be a circle, a regular octagon, a regular hexagon, or the like. The basic shape of the patch 40 can have a line-symmetrical shape, that is, a two-way line-symmetrical shape in which each of two straight lines orthogonal to each other is taken as an axis of symmetry. The two-way line-symmetrical shape refers to a figure that is symmetrical with respect to a first straight line as an axis of symmetry and also symmetrical with respect to a second straight line orthogonal to the first straight line. The two-way line-symmetrical shape corresponds to, for example, an ellipse, a rectangle, a circle, a square, a regular hexagon, a regular octagon, a rhombus, or the like. Further, the patch 40 can also be a point-symmetrical figure such as a circle, a square, a rectangle, a parallelogram, or the like.

[0054] The power feeder 50 is a conductor for supplying power to the patch 40. The power feeder 50 extends from an edge portion of the patch 40 in a direction perpendicular to the Z direction. The power feeder 50 includes a portion extending from a power supply point along a virtual straight line connecting an approximate center of the patch 40 and the power supply point. One of end portions of the power feeder 50 is electrically connected to an end portion of the patch 40. The other end portion of the power feeder 50 is electrically connected to an inner conductor of the coaxial cable. A connection portion between the power feeder 50 and the patch 40 corresponds to the power supply point. A current flowing into the power feeder 50 through the coaxial cable is conducted to the patch 40 and causes the patch 40 to resonate. The power supply method is not limited to the direct power supply method. A power supply method in which the power feeder 50 and the patch 40 are electromagnetically coupled can also be employed.

[0055] As described above, the power feeder 50 according to the present embodiment is a conductor arranged at the rear surface 20b of the main plate 20. The conductor is sometimes referred to as a microstrip line. The power feeder 50 is formed by patterning a metal foil arranged at the rear surface 20b of the main plate 20. The power feeder 50 is formed integrally with the patch 40. The power feeder 50 extends in the X direction from the power supply side 40a of the patch 40. The power feeder 50 is connected to an approximate center portion of the power supply side 40a in the Y direction. The power feeder 50 has a substantially L shape in a plan view. The power feeder 50 extends from an edge portion of the patch 40 in the X direction, and extends from an end portion of the extension portion in the X direction in the Y direction. The power feeder 50 is arranged to face the ground plate 30 in the Z direction.

[0056] The short-circuit portion 60 electrically connects the ground plate 30 and the patch 40 even if the ground plate 30 and the patch 40 are short-circuited. The short-circuit portion 60 is a columnar conductor arranged at the main plate 20. One of the end portions of the short-circuit portion 60 is connected to the ground plate 30, and the other of the end portions of the short-circuit portion 60 is connected to the patch 40. The short-circuit portion 60 has, for example, a substantially circular plane. By adjusting the diameter and the length of the short-circuit portion 60, the inductance provided in the short-circuit portion 60 can be adjusted. The short-circuit portion 60 is connected to the substantially center of the patch 40 in a plan view. Further, the center of the patch 40 corresponds to the centroid of the patch 40.

[0057] Since the patch 40 according to the present embodiment has a square planar shape, the center corresponds to the intersection of the two diagonal lines of the patch 40. The short-circuit portion 60 is a via conductor that arranges a conductor in a through-hole formed at the main plate 20. The through-hole can also be referred to as a via. The through-hole penetrates the main plate 20 from the main surface 20a to the rear surface 20b. The number of via conductors that constitute the short-circuit portion 60 is not particularly limited. In the present embodiment, one via conductor includes the short-circuit portion 60. The short-circuit portion 60 can be formed of a plurality of via conductors arranged in parallel between the ground plate 30 and the patch 40.

[0058] The antenna device 10 further includes a shielding portion 70. The shielding portion 70 has the same potential as the ground plate 30 and functions as an electromagnetic wave shield. The shielding portion 70 according to the present embodiment has a ground conductor 71 and a via conductor 72. The ground conductor 71 is arranged on the rear surface 20b of the main plate 20. The ground conductor 71 surrounds the patch 40 in a plan view. The ground conductor 71 is formed by patterning a metal foil arranged at the rear surface 20b of the main plate 20. The ground conductor 71 includes a notch 71a. The power feeder 50 is led outside the ground conductor 71 through the notch 71a. The ground conductor 71 has a substantially C shape in a plan view. The ground conductor 71 faces each of the four sides of the patch 40.

[0059] The via conductor 72 is a conductor arranged in a through-hole formed at the main plate 20. The through-hole can also be referred to as a via. The through-hole penetrates the main plate 20 in the Z direction. The via conductor 72 extends in the Z direction. One of the end portions of the via conductor 72 is connected to the ground plate 30, and the other of the end portions of the via conductor 72 is connected to the ground conductor 71. The shielding portion 70 includes a plurality of via conductors 72. The via conductors 72 are arranged side by side along the extension direction of the ground conductor 71. The via conductors 72 are arranged at intervals of a half wavelength or less of the operating frequency, so that electromagnetic waves do not leak from adjacent via conductors 72.

[0060] The ground conductor 71 is connected to the ground plate 30 through the passage conductor 72. Therefore, the outer conductor of the coaxial cable can be connected to the ground conductor 71 so that the ground plate 30 provides a ground potential. The configuration of the shield portion 70 can not be limited to the above example. For example, a configuration excluding the ground conductor 71, that is, a configuration in which only the passage conductor 72 is provided, can also be employed. The arrangement of the shield portion 70 in a plan view can not be limited to the above example. The shield portion 70 can be arranged to face only a part of the sides of the patch 40. For example, it can be arranged to face only one of the four sides of the patch 40.

[0061] The connection between the antenna device 10 and the power supply circuit (wireless device) is not limited to the coaxial cable. The antenna device 10 and the power supply circuit can be connected by using another communication cable such as a power supply line or a feed line. Furthermore, the antenna device 10 and the power supply circuit can be connected via a matching circuit, a filter circuit, or the like in addition to the coaxial cable. The antenna device 10 can be provided integrally with the power supply circuit.

[0062] (Antenna operation)

[0063] The operation of the antenna device 10 will be described below. The antenna device 10 thus configured has a structure in which the ground plate 30 and the patch 40 facing each other are connected through the short-circuit portion 60. This structure is a so-called mushroom-like structure, which is the same as the basic structure of metamaterials. Since the antenna device 10 is an antenna to which the technology of metamaterials is applied, the antenna device 10 is sometimes referred to as a metamaterial antenna.

[0064] Since the antenna device 10 is designed to operate in a zero-order resonant mode at a desired operating frequency, the antenna device can also be referred to as a zero-order resonant antenna. In the dispersion characteristics of metamaterials, the resonance phenomenon at a frequency at which the phase constant β becomes zero (0) is zero-order resonance. The phase constant β is the imaginary part of the propagation coefficient γ of a wave propagating on a transmission line. The antenna device 10 is capable of satisfactorily transmitting and / or receiving radio waves in a predetermined frequency band including the frequency at which zero-order resonance occurs.

[0065] The antenna device 10 operates by LC parallel resonance of a capacitor formed between the ground plate 30 and the patch 40 and an inductor provided in the short-circuit portion 60. In the equivalent circuit described below, the capacitor formed between the ground plate 30 and the patch 40 is referred to as Cl, and the inductor formed in the short-circuit portion 60 is referred to as LI. In the antenna device 10, the patch 40 is short-circuited with the ground plate 30 by the short-circuit portion 60 provided in the central region of the patch 40. The area of the patch 40 is the area of the capacitor that is formed in parallel with the inductor of the short-circuit portion 60 at a desired frequency (operating frequency). The value of the inductor is determined in accordance with the dimensions of the respective portions of the short-circuit portion 60, such as the length and diameter of the short-circuit portion 60 in the Z direction. The value of the inductor can also be referred to as the inductance.

[0066] Therefore, when power of the operating frequency is supplied, parallel resonance occurs due to the exchange of energy between the inductor and the capacitor, and an electric field that is perpendicular to the ground plate 30 and the patch 40 is generated between the ground plate 30 and the patch 40. That is, an electric field in the Z direction is generated. This vertical electric field propagates from the short-circuit portion 60 toward the edge portion of the patch 40, is vertically polarized at the edge portion of the patch 40, and propagates in space. The vertically polarized wave here refers to a radio wave in which the direction of vibration of the electric field is perpendicular to the ground plate 30 and the patch 40. Furthermore, the antenna device 10 receives a vertically polarized wave from outside the antenna device that is resonated by the LC parallel resonance.

[0067] The resonance frequency of the zeroth-order resonance does not depend on the antenna size. Therefore, the length of one side of the patch 40 can be made shorter than the 1 / 2 wavelength of the zeroth-order resonance frequency. For example, even if one side has a length equal to the quarter wavelength, the zeroth-order resonance can be generated. For example, when the operating frequency is 2.44 GHz, the wavelength λe can be obtained by (300 [mm / s] / 2.44 [GHz]) / the square root of the dielectric constant of the main plate 20 in a configuration including the main plate 20. One side can be made shorter than the quarter wavelength. However, the gain, such as the antenna gain, can be reduced, for example.

[0068] (Slits and additional conductors)

[0069] The following describes Figures 1 to 7 An additional structure according to the present embodiment that is added to the basic structure of the zeroth-order resonance antenna. Figure 5 An equivalent circuit diagram of a reference example of an antenna device is shown. In the reference example, elements that are the same as or related to the present embodiment are denoted by adding "r" to the end of the reference numerals in the present embodiment. However, the common reference numerals are given to the capacitor and the inductor. In Figure 5 In the reference example, some circuit elements, such as the inductor included in the patch, are omitted for convenience.Figure 6 is Figure 1 is an enlarged view of the region VI in Figure 6 Various capacitors and inductors are also shown.

[0070] As Figure 1 and Figure 3 In the antenna device 10 according to the present embodiment, the patch 40 has at least one slit 41. The slit 41 has a predetermined depth in the Z direction and has an aperture that opens to a side surface 400 of the patch 40. The aperture can also be referred to as an opening. In particular, the side surface 400 has an aperture that opens to an outer surface 400a. The side surface 400 is a surface that connects a lower surface of the patch 40 at the main board 20 and an upper surface of the main board 20 that is opposite to the lower surface in the Z direction. The side surface 400 is substantially parallel to the Z direction. The outer surface 400a defines or specifies an outer contour of the patch 40. The outer surface 400a is a surface that is derived from an outer peripheral surface of a basic shape of the patch 40. The side surface 400 has an inner surface 400b that defines or specifies the slit 41. The inner surface 400b is different from the outer surface 400a. The inner surface 400b is connected to the outer surface 400a. The inner surface 400b can also be referred to as an inner side surface. The outer surface 400a can also be referred to as an outer side surface.

[0071] The aperture of the slit 41 is formed away from the feeding point at the outer surface 400a of the patch 40. For example, in a planar square patch 40, the slit 41 has an aperture at a side different from the feeding side 40a. The shape, size, arrangement, and number of the slit 41 are not limited to the above example. The patch 40 can have only one slit 41 or can have a plurality of slits 41. The positions of the two slits 41 can be staggered in a single direction orthogonal to the Z direction. The slit 41 can be provided to have an aperture that opens to the outer surface 400a at the opposite side 40d. The slit 41 is not limited to a straight line. For example, a slit 41 having a substantially L shape in a plan view can be employed.

[0072] The slit 41 can be a groove provided to be half the depth of the patch 40. The slit 41 according to the present embodiment penetrates the patch 40 in the Z direction. The patch 40 has two slits 41. The provision of the two slits 41 is such that the patch 40 has two-fold symmetry around the Z axis. When the slit 41 is provided to have two-fold symmetry, deviation of the electric field distribution can be suppressed.

[0073] Two slits 41 are provided to sandwich the short-circuit portion 60 in a plan view, in other words, the approximate center of the patch 40 in the Y direction. One of the slits 41 has an aperture that opens to the outer surface 400a at the adjacent side 40b and extends toward the center of the patch 40 in the Y direction. The other of the slits 41 has an aperture that opens to the outer surface 400a at the adjacent side 40c and extends toward the center of the patch 40 in the Y direction. Each of the slits 41 has an approximately rectangular planar shape whose longitudinal direction is the Y direction. Hereinafter, the slit 41 having the aperture that opens to the adjacent side 40b can be referred to as slit 41b, and the slit 41 having the aperture that opens to the adjacent side 41c can be referred to as slit 41c.

[0074] The extension length and the width of the two slits 41b, 41c are equal to each other. The slits 41b, 41c divide the patch 40 into a first patch portion 401, a second patch portion 402, and a third patch portion 403. The first patch portion 401 and the second patch portion 402 have the same shape and area. The first patch portion 401 is a portion at the opposite side 40d with respect to the slits 41b, 41c. The second patch portion 402 is a portion at the power feeding side 40a with respect to the slits 41b, 41c. The third patch portion 403 is a portion sandwiched between the two slits 41b and 41c, connecting the first patch portion 401 and the second patch portion 402. In the Y direction, the extension length of each of the slits 41b and 41c is longer than the length of the third patch portion 403. The width of each of the slits 41b, 41c is shorter than the respective lengths of the first patch portion 401 and the second patch portion 402 in the X direction. The patch 40 includes the slits 41b, 41c, the first patch portion 401, the second patch portion 402, and the third patch portion 403 to form a substantially planar H shape.

[0075] Figure 5 The antenna device 10r in the reference example has a structure in which the additional conductor 80 described later is removed from the antenna device 10 of the present embodiment. The patch 40r has two slits (not shown) similar to the slits 41b, 41c described above. The capacitor C2 is formed between the first patch portion and the second patch portion through one of the slits. The capacitor C3 is formed between the first patch portion and the second patch portion through one of the slits. These capacitors C2 and C3 are connected in parallel to each other. The parallel circuit of the capacitors C2, C3 is connected between the capacitor C1 and the inductor L1. If the slits are provided in the patch 40r and the capacitors are connected between the capacitor C1 and the inductor L1, the reflection characteristics can be improved.

[0076] As Figure 1 , 3As shown in FIGS. 4 and 6, the antenna device 10 further includes an additional conductor 80. The additional conductor 80 is a conductor added to the basic configuration of the zeroth-order resonant antenna. The additional conductor 80 is a conductor made of copper or the like and has the same potential (ground potential) as the ground plate 30. The additional conductor 80 is arranged at the main plate 20 so that a side surface of the additional conductor 80 faces a side surface of the patch 40 at a predetermined distance. In a plan view, the entire additional conductor 80 overlaps the ground plate 30.

[0077] The additional conductor 80 is arranged on the rear surface 20b of the main plate 20. That is, the additional conductor 80 is arranged on the same surface shared by the patch 40 and the power feeder 50. The additional conductor 80 is formed by patterning a metal foil arranged at the rear surface 20b of the main plate 20. The thickness of the additional conductor 80 is substantially equal to the thickness of the patch 40 and the power feeder 50. The additional conductor 80 has a base portion 81, an insertion portion 82, and a connection portion 83.

[0078] The base portion 81 extends along the outer surface 400a of the patch 40. The base portion 81 is arranged to face the outer surface 400a around the aperture of the slit 41. The base portion 81 can be arranged to span the aperture of the slit 41, or can be arranged only on one side with respect to the slit 41.

[0079] In the present embodiment, the base portion 81 is arranged to face the outer surface 400a of the adjacent side 40b. The base portion 81 faces the outer surface 400a around the aperture of the slit 41b. The base portion 81 faces each of the first patch portion 401 and the second patch portion 402. The base portion 81 extends in the X direction. By the above arrangement, the capacitor C5 is formed at the outer surface 400a of the adjacent side 40b between a portion of the first patch portion 401 and a side surface of the base portion 81. The capacitor C6 is formed at the outer surface 400a of the adjacent side 40b between a portion of the second patch portion 402 and a side surface of the base portion 81.

[0080] The capacitance value, in other words, the electrostatic capacitance of the capacitors C5, C6 is determined by the distance between the base portion 81 and the outer surface 400a of the patch 40 and / or the relative area formed therebetween. In the first patch portion 401 and the second patch portion 402, the distance between the base portion 81 and the outer surface 400a of the patch 40 can be substantially equal to each other, or can be different from each other. The length of the base portion 81 and the length of the patch 40 in the X direction are opposite to each other. In the first patch portion 401 and the second patch portion 402, the length, in other words, the relative area can be substantially equal to each other, or can be different from each other. The value of each of the capacitors C5, C6 can be adjusted according to the distance and / or the relative area, in other words, the relative length.

[0081] In the present embodiment, the base portion 81 is arranged to face the entire area of the adjacent side 40b. The base portion 81 is arranged to face the portion of the adjacent side 40b from the boundary with the opposite side 40d to the boundary with the power supply side 40a. The distance between the base portion 81 and the outer surface 400a of the patch 40 is substantially constant over the total length of the base portion 81.

[0082] The insertion portion 82 is connected to the base portion 81 and arranged in the slit 41 to face the inner surface 400b of the patch 40. The connection position of the insertion portion 82 with respect to the base portion 81 is not particularly limited. In the present embodiment, the insertion portion 82 extends in the Y direction. The insertion portion 82 has a substantially rectangular planar shape with the long side direction being the Y direction. The side surface of the insertion portion 82 faces each of the inner surface 400b of the first patch portion 401, the inner surface 400b of the second patch portion 402, and the inner surface 400b of the third patch portion 403. The insertion portion 82 is connected to the central portion of the base portion 81 in the X direction.

[0083] By the above arrangement, the capacitor C21 is formed between the inner surface 400b of the first patch portion 401 and the side surface of the insertion portion 82. The capacitor C22 is formed between the inner surface 400b of the third patch portion 403 as the base portion of the slit 41 and the side surface of the insertion portion 82. The capacitor C23 is formed between the inner surface 400b of the second patch portion 402 and the side surface of the insertion portion 82. The parallel circuit of the capacitors C21, C22, and C23 corresponds to the above-described capacitor C2.

[0084] The capacitance value of each of the capacitors C21, C22, and C23 is determined by the distance between the insertion portion 82 and the inner surface 400b of the patch 40 and / or the opposing area formed therebetween.

[0085] For example, the distance between the insertion portion 82 and the inner surface 400b can be substantially equal in the first patch portion 401 and the second patch portion 402, or can be different from each other. The respective lengths of the insertion portion 82 and the length of the inner surface 400b in the extension direction of the insertion portion 82 are relative to each other. The relative lengths, in other words, the opposing areas in the first patch portion 401 and the second patch portion 402 can be substantially equal, or can be different from each other. The respective values of the capacitors C21, C22, and C23 can be adjusted according to the distance and / or the opposing area, in other words, the relative lengths, between the insertion portion 82 and each of the patch portions 401, 402, and 403. In the present embodiment, the distance between the insertion portion 82 and the inner surface 400b is substantially constant over the total length of the opposing area.

[0086] The connecting portion 83 is a part of the additional conductor 80 that electrically connects the other portions (i.e., the base portion 81 and the insertion portion 82) to the ground plate 30. The connecting portion 83 extends from the base portion 81 and includes the inductor L2. For example, a conductor arranged on the rear surface 20b of the main plate 20 and connected to the base portion 81, a via conductor connected to the base portion 81, and a combination of the conductor and the via conductor arranged on the rear surface 20b can be employed as the connecting portion 83.

[0087] In the present embodiment, the connecting portion 83 is a conductor connected to the base portion 81. The connecting portion 83 is integrally formed with the base portion 81 and the insertion portion 82 by patterning a metal foil. The connecting portion 83 extends from the base portion 81 to a side opposite to the insertion portion 82 in the Y direction. One of the end portions of the connecting portion 83 is connected to the base portion 81. The other of the end portions of the connecting portion 83 is connected to the ground conductor 71 included in the shielding portion 70. By electrically connecting the connecting portion 83 to the ground conductor 71, the additional conductor 80 has the same potential (ground potential) as the ground plate 30. The inductance value of the inductor L2 included in the connecting portion 83 is determined in accordance with the length and the width of the conductor in the extending direction.

[0088] Figure 7 is an equivalent circuit diagram of the antenna device 10 according to the present embodiment. In Figure 7 , some circuit elements are omitted for convenience, for example, the inductors included in the patch.

[0089] As described above, in the present embodiment, the insertion portion 82 of the additional conductor 80 forms capacitors C21, C22, and C23 with the inner surface 400b defining the slit 41 or 41b at the patch 40. By arranging the insertion portion 82 in the slit 41b, Figure 5 The capacitor C2 in the reference example of Figure 7 is replaced with a parallel circuit of the capacitors C21, C22, and C23. As shown in

[0090] The base portion 81 of the additional conductor 80 forms capacitors C5 and C6 with the outer surface 400a of the patch 40. A parallel circuit of the capacitors C5 and C6 is connected to the ground plate 30 through the inductor L2 of the connecting portion 83. As shown in Figure 7 , an LC circuit having the inductor L2 and the capacitors C5 and C6 is formed between the ground plate 30 and the patch 40. The LC circuit is connected in parallel to the capacitor C1 and the inductor L1.

[0091] (Summary of the first embodiment)

[0092] Figures 8 to 11 Results of electromagnetic field simulation of the antenna device at a printed circuit board are shown.Figure 8 The reflection characteristics are shown. In Figure 8 the single-dot chain line and the double-dot chain line respectively indicate the results of the antenna device in the reference examples. The antenna device in the reference examples includes the basic structure of the zeroth-order resonant antenna, and does not have a slit and an additional conductor. In other words, the antenna device in the reference examples includes the zeroth-order resonant antenna having the comparative structure. The single-dot chain line indicates the result of the first reference example, and the double-dot chain line indicates the result of the second reference example. The solid line indicates the antenna device 10 of the present embodiment, i.e., the result of the present embodiment. In the reference examples and the present embodiment, the operating frequency, the configuration of the main board such as the dielectric constant and the thickness, and the diameter of the shorting portion are the same.

[0093] The zeroth-order resonant antenna (metamaterial antenna) configured at the printed circuit board can cause a change in the frequency band with respect to the target resonant frequency due to various reasons, such as a change in the dielectric and a modification of the main board material. Due to the above reasons, in the first reference example, the frequency band deviates from the target resonant frequency (2.44 GHz). As Figure 8 indicated, the frequency band of the first reference example shifts to the low frequency side with respect to the target. Figure 9 The reflection characteristics (electric field distribution) in the first reference example are indicated. The maximum gain of the first reference example is -11.8 dB at 2.44 GHz. Due to the deviation of the frequency band, the antenna gain is reduced.

[0094] The zeroth-order resonant antenna having the basic structure at the printed circuit board operates by LC parallel resonance between the inductor L1 of the via conductor included in the shorting portion and the capacitor C1 formed between the patch and the ground plate. The inductor L1 is determined by the thickness of the main board and the via diameter, and the capacitor C1 is determined by the size of the patch and the thickness of the main board. The thickness of the main board is limited by the configuration of other circuits formed at the printed circuit board. As described above, there are few parameters that determine the resonant frequency.

[0095] The size of the patch, the via diameter of the shorting portion, and the size of the ground plate are adjusted to enhance the reflection characteristics. To change the size of the antenna, the layout of the circuits around the antenna at the printed circuit board needs to be considered. In addition, since the via diameter is limited by the processing (e.g., drilling), the via diameter cannot be made smaller than the predetermined diameter. When the frequency is shifted to the low frequency side with respect to the target as in the first reference example, the resonant frequency cannot be increased unless the size of the patch portion is reduced.

[0096] In the second reference example, the size of the patch is smaller than the patch size of the first reference example to increase the resonant frequency. As described above, when the size of the patch is reduced, not only the relative area formed between the patch and the ground plate is reduced, but also the value of the capacitor C1 is reduced. As a result, as Figure 8As shown, the resonant frequency of the second reference example is shifted to the higher frequency side relative to the first reference example. On the other hand, the gain of the antenna decreases due to the decrease in the radiation area. Figure 10 The reflection characteristics in the second reference example are shown. Although the resonant frequency is shifted near the target, the maximum gain of the second reference example is -9.7 dB at 2.44 GHz due to the decrease in the radiation area.

[0097] Since the zeroth-order resonant antenna has a smaller maximum gain than the first-order resonant antenna, it can be desirable to change the design without reducing the original gain. Since the via diameter is generally limited in the process, the size of the patch is the main parameter for adjusting the resonant frequency and enhancing the reflection characteristics in the zeroth-order resonant antenna having the basic structure. Therefore, it affects the antenna gain.

[0098] On the other hand, according to the antenna device 10 in the present embodiment, an additional conductor 80 is added to the basic structure of the zeroth-order resonant antenna. A capacitor is formed at a portion of the base 81 of the additional conductor 80 facing the outer surface 400a of the patch 40. The connection portion 83 of the additional conductor 80 includes an inductor. Since a new parameter is added in the LC parallel resonant circuit, the design freedom of the antenna device 10 is improved. In a case where the size of the patch 40 is configured to be the same as that in the first reference example, the resonant frequency can be shifted to the higher frequency side as shown in Figure 8 to match the target. In other words, the resonant frequency can be shifted to the higher frequency side without reducing the size of the patch 40.

[0099] The patch 40 is provided with a slit 41. Since the area of the patch 40 is reduced by the slit 41, the capacitance value of the capacitor C1 is reduced. On the other hand, the slit 41 connects the capacitor between the capacitor C1 and the inductor L1 as shown in Figure 5 the above-described reference example. Therefore, the parameters for determining the entire capacitor increase. By providing the slit 41, the design freedom of the antenna device 10 is improved. The reflection characteristics can be improved compared to a case where there is no slit 41.

[0100] In the present embodiment, the insertion portion 82 of the additional conductor 80 is arranged inside the slit 41. A plurality of capacitors are formed at a portion of the insertion portion 82 of the additional conductor 80 facing the inner surface 400b of the patch 40. As a result, the parameters can be further increased, and the design freedom of the antenna device 10 can be further improved. Therefore, as shown in Figure 8 the reflection characteristics can be further enhanced. According to the present embodiment, the reflection characteristics can be further improved compared to a structure in which the insertion portion is not arranged in the slit as shown in Figure 5

[0101] ​According to the antenna device 10 of the present embodiment, it is possible to improve the reflection characteristic while shifting the resonance frequency to the higher resonance frequency side without changing the physical size of the patch 40. Since the physical size (outer contour) of the patch 40 is not changed, it is possible to improve the antenna gain. Figure 11 The radiation characteristic in the present example is shown. The maximum gain of the present example is -7.8 dB at 2.44 GHz.

[0102] In the present embodiment, the patch 40 having a substantially square planar shape includes the slit 41b and the slit 41c. The slit 41b has an aperture opening to the adjacent side 40b, and the slit 41c has an aperture opening to the adjacent side 40c. The effect of improving the reflection characteristic is higher in the case where the slit 41 is provided in at least one of the adjacent sides 40b and 40c than in the case where the slit 41 is provided in the opposite side 40d. The slits 41b and 41c correspond to adjacent slits.

[0103] In the present embodiment, the insertion portion 82 of the additional conductor 80 is arranged at only the slit 41b among the slits 41b and 41c. According to this case, the electric field distribution is shifted to the side where the insertion portion 82 is provided, and the directivity can be shifted to the slit 41b side in the Y direction. In the present embodiment, the power feeder 50 has a substantially L-shaped planar shape, and has a portion extending toward the slit 41b in the Y direction. As a result, the directivity is shifted to the slit 41b in the Y direction. A synergistic effect of the arrangement of the power feeder 50 and the arrangement of the insertion portion 82 can be expected. The slit 41b corresponds to a first adjacent slit, and the slit 41c corresponds to a second adjacent slit.

[0104] In the present embodiment, the base portion 81 is arranged to face the outer surface 400a across the aperture of the slit 41b. In other words, the base portion 81 is arranged to face the outer surface 400a of the first patch portion 401 and the outer surface 400a of the second patch portion 402. As a result, the above-described capacitors C5 and C6 are formed. With the increase in the number of parameters, it is possible to improve the design freedom of the antenna device 10. Since a more fine adjustment can be made by improving the design freedom, it is easier to match the resonance frequency to the target resonance frequency.

[0105] In the present embodiment, the connection portion 83 includes a conductor connected to the base portion 81. In other words, at least a portion of the connection portion 83 closer to the base portion 81 is provided at the surface where the base portion 81 is located. As a result, the distance between the base portion 81 and the outer surface 400a of the patch 40 can be narrowed compared to the configuration where the via conductor of the connection portion 83 is connected to the base portion 81. Therefore, it is possible to improve the design freedom of the antenna device 10.

[0106] Figure 12The reflection characteristic variation depending on the position of the connection portion 83 in the antenna device 10 is shown. Figure 13 The arrangement of the connection portion 83 with respect to the base portion 81 is shown. In the electromagnetic field simulation, the center of the portion of the second patch portion 402 facing the base portion 81 in the X direction is set as the reference position of the connection portion 83. Figure 12 The center shown in (B) indicates the reflection characteristic in the case where the connection portion 83 is taken as the reference position. Figure 12 The movement toward XR shown in (C) indicates the reflection characteristic in the case where the connection portion 83 is moved by a predetermined distance in the XR direction from the reference position. Figure 13 The reflection characteristic in the case where the connection portion 83 is moved by a predetermined distance in the XR direction from the reference position is shown. Figure 12 The movement toward XL shown in (D) indicates the reflection characteristic in the case where the connection portion 83 is moved by a predetermined distance in the XL direction from the reference position. Figure 13 The reflection characteristic in the case where the connection portion 83 is moved by a predetermined distance in the XL direction from the reference position is shown. The XR direction is the direction in the X direction from the reference position toward the power feeding side 40a. The XL direction is the direction in the X direction from the reference position toward the opposite side 40d. In the electromagnetic field simulation, the base portion 81 has a length substantially equal to that of the adjacent side 40b of the patch 40.

[0107] In the case where the connection portion 83 is set closer to XR from the reference position, the amount of high frequency shift of the resonance frequency is smaller than that of the reference position, as shown by the single-dot chain line in (B). Figure 12 In the case where the connection portion 83 is set closer to XL from the reference position, the amount of high frequency shift of the resonance frequency is larger than that of the reference position, as shown by the broken line in (B). Figure 12 In the case where the connection portion 83 is moved toward the XR side, the distance from the shorting portion 60 to the connection portion where the ground conductor 71 is connected to the connection portion 83 becomes longer. In other words, the connection portion is the ground connection portion at the additional conductor 80. As a result, the amount of high frequency shift decreases. In the case where the connection portion 83 is moved toward the XL side, the distance from the shorting portion 60 to the connection portion where the ground conductor 71 is connected to the connection portion 83 becomes longer, and the amount of high frequency shift decreases.

[0108] In other words, in the case where the connection portion 83 is connected closer to the shorting portion 60 than the end portion of the base portion 81 in the extending direction (i.e., the X direction), the amount of high frequency shift can be further increased. In the case where the connection portion 83 is connected to the end portion of the base portion 81 in the extending direction, the amount of high frequency shift can be decreased.

[0109] (Variation Example)

[0110] The above describes the example in which the insertion portion 82 of the additional conductor 80 is arranged at the slit 41b of the adjacent side 40b, but the present disclosure is not limited to such a case. For example, as shown in the variation example in (B), in a configuration in which the patch 40 has two slits 41b, 41c, the additional conductor 80 can also be provided at the slit 41c. As shown in (C), the additional conductor 80 can also be provided at the slit 41b of the adjacent side 40b and at the slit 41c of the opposite side 40d. Figure 14 Figure 14 ​As shown, the base 81 of the additional conductor 80 faces the outer surface 400a of the adjacent side 40c. The insertion portion 82 is arranged in the slit 41c and faces the inner surface 400b. The connection portion 83 extends from the base 81 in the Y direction to a side away from the patch 40.

[0111] As shown in a modification example of Figure 15 , the additional conductor 80 can be arranged at each of the two slits 41b and 41c. The antenna device 10 includes two additional conductors 80b and 80c. The insertion portion 82 of the additional conductor 80b is arranged at the slit 41b. The insertion portion 82 of the additional conductor 80c is arranged at the slit 41c.

[0112] As shown in a modification example of Figure 16 , the patch 40 can have a slit 41d having an aperture opening to the opposite side 40d. The antenna device 10 can include an additional conductor 80d at the slit 41d. The insertion portion 82 of the additional conductor 80d is arranged at the slit 41d. In Figure 16 , the patch 40 has three slits 41b, 41c, and 41d. In the present embodiment, the additional conductor 80 is arranged at two of the three slits 41b, 41c, and 41d. Although only the slit 41d can be provided, the slits 41b and 41c each having an aperture opening to the adjacent side 40b and 40c are more effective in enhancing the reflection characteristics.

[0113] Figure 17 is an enlarged view of the region XVII of Figure 15 . As shown in Figure 17 , the capacitors C7, C8, C31, C32, and C33 are formed between the additional conductor 80c and the patch 40. The capacitor C7 is formed between the base 81 and the outer surface 400a of the first patch portion 401. The capacitor C8 is formed between the base 81 and the outer surface 400a of the second patch portion 402. The capacitor C31 is formed between the insertion portion 82 and the inner surface 400b of the first patch portion 401. The capacitor C32 is formed between the insertion portion 82 and the inner surface 400b of the third patch portion 403. The capacitor C33 is formed between the insertion portion 82 and the inner surface 400b of the second patch portion 402. The connection portion 83 includes the inductor L3.

[0114] Figure 18 is an enlarged view of the region XVII of Figure 15An equivalent circuit diagram of the modification example shown. By adding an additional conductor 80c, the capacitor C3 is replaced with a parallel circuit having capacitors C31, C32, and C33. A parallel circuit having capacitors C21, C22, C23, C32, and C33 is connected between the capacitor C1 and the inductor L1. An LC circuit having the inductor L3 and the capacitors C7 and C8 is formed between the ground plate 30 and the patch 40. The LC circuit having the inductor L3 and the capacitors C7 and C8 is connected in parallel with the LC circuit having the inductor L2 and the capacitors C5 and C6. Since the parameters are further increased by increasing the number of additional conductors 80, the design freedom of the antenna device 10 can be improved.

[0115] As shown in the modification example of Figure 19 , one additional conductor 80 can have a plurality of connection portions 83. In Figure 19 , two connection portions 83 are connected to one base portion 81. The base portion 81 and the connection portion 83 have a substantially F-shaped planar shape.

[0116] As shown in the modification example of Figure 20 , the extension length of the base portion 81 can be shorter than the length of the side on which the slit 41 is opened. In Figure 20 , the extension length of the base portion 81 is shorter than the length of the adjacent side 40b. The base portion 81 faces the entire area of the first patch portion 401 at the adjacent side 40b, and faces only a part of the second patch portion 402 at the adjacent side 40b. Since the relative area formed between the base portion 81 and the second portion 402 is small, the capacitance value of the capacitor C6 becomes small.

[0117] In Figure 20 , the connection portion 83 is connected to the end of the base portion 81 in the extension direction of the base portion 81. On the other hand, as shown in the modification example of Figure 21 , the connection portion 83 can be connected to a position closer to the short-circuit portion 60 than the end of the base portion 81 in the extension direction. As described above, the high-frequency shift amount can be further increased.

[0118] As in the modification example of Figure 22 , the connection portion 83 of the additional conductor 80 can include a via conductor 83b and a conductor 83a arranged at the rear surface 20b. Although not shown, the connection portion 83 can include only the via conductor 83b and not include the conductor 83a.

[0119] (Second Embodiment)

[0120] The second embodiment is a modification of the foregoing embodiment as a basic configuration and can incorporate the description of the foregoing embodiment. In the previous embodiment, the power feeder 50 is connected to the patch 40. Instead, the power feeder 50 can form a capacitor with the patch 40.

[0121] Figure 23 An antenna device 10 according to the present embodiment is shown. Figure 24 Figure 23 A schematic view of the area XXIV is enlarged. As shown in Figure 23 24 The power feeder 50 is not connected to the patch 40 in the antenna device 10 according to the present embodiment, as shown in Figs. 9A and 9B. The power feeder 50 forms a capacitor with the patch 40, and is electrically connected to the patch 40 through the capacitor. The power feeder 50 has a branch portion 51. The branch portion 51 is provided at an end of the power feeder 50 close to the patch 40. The branch portion 51 branches into a plurality of branches. In the present embodiment, the branch portion 51 branches into three branches. The branch portion 51 includes a base portion 51a and three protruding portions 51b extending from the base portion 51a in the X direction.

[0122] The second patch portion 402 of the patch 40 includes notches 42 for individually accommodating each of the protruding portions 51b of the branch portion 51. The notches 42 have apertures opening toward the outer surface 400a of the patch 40. The side surface 400 has an inner surface 400c defining or designating the notches 42. The inner surface 400c is connected to the outer surface 400a of the power feeding side 40a. The notches 42 include three grooves accommodating the protruding portions 51b, respectively, and include two protruding portions between adjacent grooves.

[0123] The branch portion 51 is arranged to face the inner surface 400c at a predetermined distance. By the above arrangement, capacitors C9, C10, and C11 are formed between the respective tip end surfaces of the protruding portions 51b and the inner surface 400c forming the groove bottoms. Capacitors C12, C13, C14, C15, C16, and C17 are formed between the two side surfaces of the protruding portions 51b and the inner surface 400c. Capacitors C18 and C19 are formed between the base portion 51a and the inner surface 400c forming the tip ends of the protruding portions. The branch portion 51 penetrates the short circuit portion 60 in a plan view, and is linearly symmetric with respect to a virtual straight line parallel to the X axis. Similarly, the notches 42 are linearly symmetric with respect to the above virtual straight line. The power feeder 50 includes an inductor L4. Since other configurations are similar to those described in the foregoing embodiment, the other configurations are not described hereinafter.

[0124] Figure 25 is an equivalent circuit diagram of the antenna device 10 according to the present embodiment. As described above, in the present embodiment, the power feeder 50 includes the inductor L4. The branch portion 51 provided at the end of the power feeder 50 forms the capacitors C9 to C19 with the inner surface 400c of the patch 40. These capacitors C9 to C19 are connected in parallel to each other. The LC circuit having the inductor L4 and the capacitors C9 to C19 is connected in parallel to the LC circuit having the inductor L2 and the capacitors C15, C6. ​​

[0125] (Summary of the second embodiment)

[0126] Figure 26 Results of electromagnetic field simulation of the antenna device 10 of the present embodiment, that is, reflection characteristics, are shown. In Figure 26 , results of the aforementioned embodiment are shown as a reference example in a broken line. The results of the aforementioned embodiment correspond to a solid line in Figure 8 . The solid line indicates results of the antenna device 10 in the present embodiment. In the electromagnetic field simulation of the present embodiment, configurations such as dielectric constant and thickness of the main board and diameter of the short-circuit portion are the same as those of the simulation of the previous embodiment.

[0127] The antenna device 10 according to the present embodiment includes the patch 40 having the slit 41 and the additional conductor 80. Therefore, the same advantageous effects as the configuration described in the first embodiment can be produced. In other words, it is possible to shift the resonance frequency to the higher resonance frequency side while enhancing the reflection characteristics without changing the physical size of the patch 40.

[0128] The power feeder 50 forms a capacitor or capacitance with the patch 40. The capacitance value of this capacitor is sufficiently small compared to the capacitors C5, C6 near the additional conductor 80 connected in parallel to this capacitor. The capacitance value of the capacitor near the power feeder 50 is, for example, about 1 / 50 to 1 / 1000 of the capacitance value of the capacitor near the additional conductor 80 compared to the total number of capacitors included in the respective LC circuits. The inductance value of the inductor L4 included in the power feeder 50 is sufficiently small compared to the inductor L2 included in the connection portion 83 of the additional conductor 80. Therefore, the LC circuit near the power feeder 50 enhances the impedance matched to the antenna, in other words, the reflection characteristics, but does not significantly enhance on the high frequency shift.

[0129] Since a new parameter is added in the LC parallel resonance circuit, the design freedom of the antenna device 10 is improved. In other words, as Figure 26 shown, it is possible to shift the resonance frequency to the higher resonance frequency side while enhancing the reflection characteristics without changing the physical size of the patch 40. Figure 27 Radiation characteristics in the present example are shown. The maximum gain of the present example is -7.3 dB at 2.44 GHz.

[0130] In the present embodiment, the power feeder 50 includes the branch portion 51 at the end portion near the patch 40. The branch portion 51 forms capacitors C9 to C19 with the inner surface 400c included in the notch 42 of the patch 40. With the increase in the number of parameters, the design freedom of the antenna device 10 can be improved. Since fine tuning can be performed with the improvement in the design freedom, the reflection characteristics can be further improved.

[0131] (Variation example)

[0132] The shape, size, arrangement, and number of the slits 41 and the additional conductors 80 are not limited to the above examples. Combinations with the configurations described in the foregoing examples are also possible. For example, as shown in a variant example of Figure 28 The connecting structure connecting the power feeder 50 and the patch 40 can be combined with a configuration including the patch 40 having two slits 41b, 41c and two additional conductors 80b, 80c. In this case, the slits 41b, 41c are arranged to be offset from each other. The slits 41b, 41c do not sandwich the short-circuit portion 60 in the Y direction. The patch 40 having the slits 41b and 41c has twofold symmetry about the Z axis. Figure 28

[0133] The present disclosure describes an example in which the branch portion 51 has three protruding portions 51b. However, the present disclosure is not limited to this example. For example, as shown in a variant example of Figure 29 The branch portion 51 can have five protruding portions 51b. As the number of protruding portions increases, the parameters further increase.

[0134] The present disclosure describes an example in which the power feeder 50 includes the branch portion 51. However, the present disclosure is not limited to this example. At least one capacitor can be formed between the power feeder 50 and the patch 40. For example, the end portion of the portion of the power feeder 50 extending in the X direction can be arranged to face the outer surface 400a of the power feeding side 40a of the patch 40 to form a capacitor. A portion of the power feeder 50 can be arranged at the notch 42 to form a plurality of capacitors.

[0135] (Other Embodiments)

[0136] The disclosure in the specification and drawings and the like is not limited to the above-described embodiments. The present disclosure encompasses the above-described embodiments and modifications by those skilled in the art based on the embodiments. For example, the present disclosure is not limited to the combination of the components and / or elements shown in the embodiments. The present disclosure can be implemented in various combinations. The present disclosure can have additional portions that can be added to the embodiments. The present disclosure encompasses the omission of components and / or elements of the embodiments. The present disclosure encompasses the replacement or combination of components, elements between one of the embodiments and another embodiment. The scope of the disclosed technology is not limited to the description of the embodiments.​

Claims

1. An antenna device, comprising: A motherboard (20) made of dielectric material, the motherboard including a main surface and a rear surface, the rear surface being the surface opposite to the main surface in the thickness direction of the motherboard; Ground plane (30), which is disposed on the main surface of the motherboard and configured to provide a ground potential; A patch (40) is disposed on the rear surface of the motherboard facing the ground plane; A power transmitter (50) is disposed on the rear surface of the motherboard and electrically connected to the patch; The short-circuit section (60) includes a pass conductor disposed on the motherboard and electrically connected to the patch and the ground plane; and An additional conductor (80) is disposed on the motherboard such that its side surface faces the side surface of the patch and has the same potential as the ground potential of the ground plane. The patch includes: An outer surface (400a) is configured to define the outer contour of the patch, the outer surface being a side surface of the patch; At least one slit (41) having an aperture opening toward a location remote from the portion of the outer surface electrically connected to the power feeder; and An inner surface (400b), configured to define the slit, is a side surface of the patch, and The additional conductor (80) includes: A base (81) extends in a direction along the outer surface of the patch and is positioned to face the outer surface surrounding the aperture of the slit. An insertion portion (82) is connected to the base and disposed inside the slit to face the inner surface of the patch; and A connecting portion (83) extends from the base and electrically connects the ground plane and the additional conductor.

2. The antenna device according to claim 1, in, The patch has a rectangular shape in a plan view perpendicular to the thickness direction. The patch further includes: The power supply side (40a) is electrically connected to the power feeder; Adjacent sides (40b, 40c) are the sides of the patch that are adjacent to the power supply side; The opposite side (40d) is located on the side opposite to the power supply side. Wherein, the slit has at least one adjacent slit opening toward the outer surface at the adjacent side, and The additional conductor is disposed in at least the adjacent slits.

3. The antenna device according to claim 2, in, The adjacent sides include multiple adjacent sides having a first adjacent side and a second adjacent side. The adjacent slits include multiple adjacent slits. The adjacent slits include: The first adjacent slit (41b) opens toward the outer surface at the first adjacent side; and The second adjacent slit (41c) opens toward the outer surface at the second adjacent side, and The additional conductor is located at one of the first adjacent slit and the second adjacent slit.

4. The antenna device according to claim 1, in, The base is disposed across the aperture of the slit, the insertion portion connected to the base is disposed in the aperture of the slit, and the base is disposed facing the outer surface.

5. The antenna device according to claim 1, in, At least a portion of the connecting portion extending from the base is disposed on the surface of the motherboard on which the base is disposed.

6. The antenna device according to claim 5, in, The connecting portion is connected to a position closer to the short-circuit portion than the end of the base in the extending direction.

7. The antenna device according to claim 5, in, The connecting portion is connected to the end of the base in the extending direction.

8. The antenna device according to any one of claims 1 to 7, in, The capacitance formed between the power transmitter and the patch has a smaller capacitance value than the capacitance formed between the base and the patch.

9. The antenna device according to claim 8, in, The power feeder has a branch portion (51) that branches into multiple branches at the end of the power feeder near the patch, and The patch has a notch (42) that opens onto the outer surface to accommodate the branch.

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