Antenna device

Abstract

This antenna device comprises: a first dielectric layer; a radiation electrode provided to the first dielectric layer; a second dielectric layer that has a higher relative permittivity than the first dielectric layer and covers the radiation electrode; a ground electrode that faces the radiation electrode from across the first dielectric layer and is provided on the opposite side to the second dielectric layer; and a conductor wall that extends along the thickness direction of at least the first dielectric layer among the first dielectric layer and the second dielectric layer and is provided along the outer edge of the radiation electrode in a plan view.

Description

Antenna device

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

[0002] Patent Documents 1 and 2 describe antenna devices that use a high dielectric constant material as a dielectric layer. Patent Document 3 describes an antenna having a configuration in which a conductor is provided on the outer periphery of a planar antenna and the conductor is connected to ground.

[0003] JP 2006-60772 A JP 6-29723 A JP 2020-43422 A

[0004] Such antenna devices are required to be compact and have wideband antenna characteristics. Furthermore, Patent Documents 1 to 3 do not take into consideration antenna devices that combine the respective configurations.

[0005] An object of the present invention is to provide an antenna device that can be made smaller and has broadband antenna characteristics.

[0006] An antenna device according to one embodiment includes a first dielectric layer, a radiation electrode provided on the first dielectric layer, a second dielectric layer having a higher dielectric constant than the first dielectric layer and covering the radiation electrode, a ground electrode facing the radiation electrode across the first dielectric layer and provided on the opposite side of the second dielectric layer, and a conductor wall extending along at least the thickness direction of the first dielectric layer of the first dielectric layer and the second dielectric layer and provided along the outer edge of the radiation electrode in a planar view.

[0007] According to the antenna device of the present invention, it is possible to achieve miniaturization and broadband antenna characteristics.

[0008] FIG. 1 is a perspective view showing an antenna device according to a first embodiment. FIG. 2 is a plan view showing a portion of the antenna device according to the first embodiment. FIG. 3 is a cross-sectional view taken along line III-III′ in FIG. 2 . FIG. 4 is a graph showing the relationship between the size of the ground electrode and the Q value of an antenna device according to a comparative example. FIG. 5 is a graph showing the frequency characteristics of return loss of antenna devices according to Example 1 and the comparative example. FIG. 6 is a graph showing the relationship between the size of the ground electrode and the Q value of antenna devices according to Example 1 and the comparative example. FIG. 7 is a cross-sectional view showing an antenna device according to a second embodiment. FIG. 8 is a plan view showing an antenna device according to a third embodiment. FIG. 9 is a plan view showing an antenna device according to a first modified example of the third embodiment. FIG. 10 is a perspective view showing an antenna device according to a fourth embodiment. FIG. 11 is a cross-sectional view taken along line XI-XI′ in FIG. 10 . FIG. 12 is a cross-sectional view showing a portion of an antenna device according to a second modified example of the fourth embodiment. FIG. 13 is a perspective view showing an antenna device according to a third modified example of the fourth embodiment. FIG. 14 is an explanatory diagram for explaining the polarization direction and polar angle of antenna devices according to Examples 2 to 6. Fig. 15 is a graph showing the radiation pattern of the antenna device according to Example 2. Fig. 16 is a graph showing the radiation pattern of the antenna device according to Example 3. Fig. 17 is a graph showing the radiation pattern of the antenna device according to Example 4. Fig. 18 is a graph showing the radiation pattern of the antenna device according to Example 5. Fig. 19 is a graph showing the radiation pattern of the antenna device according to Example 6.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to these embodiments. Note that each embodiment described in the present disclosure is illustrative, and partial substitution or combination of configurations between different embodiments is possible. In modified examples and the second and subsequent embodiments, descriptions of matters common to the first embodiment will be omitted, and only differences will be described. In particular, similar effects resulting from similar configurations will not be mentioned in each embodiment.

[0010] (First embodiment) Fig. 1 is a perspective view showing an antenna device according to a first embodiment. Fig. 2 is a plan view showing a portion of the antenna device according to the first embodiment. Fig. 3 is a cross-sectional view taken along III-III' in Fig. 2. Note that, in Fig. 2, the second dielectric layer 12 is omitted to make the drawing easier to see, and the planar shapes of the electrodes and the conductor wall 31 are shown. As shown in Figs. 1 to 3, the antenna device 10 has a first dielectric layer 11, a second dielectric layer 12, a radiation electrode 21, a ground electrode 22, and a conductor wall 31.

[0011] In the following description, the direction perpendicular to the surface of the radiation electrode 21 is referred to as the Z direction, the direction perpendicular to the Z direction is referred to as the X direction, and the direction perpendicular to the Z and X directions is referred to as the Y direction. The X and Y directions are both parallel to the surface of the radiation electrode 21. In the following description, a plan view refers to the positional relationship when viewed from the direction perpendicular to the surface of the radiation electrode 21 (the Z direction).

[0012] The first dielectric layer 11 is a multilayer substrate and has a rectangular shape in a plan view. The first dielectric layer 11 is flat and has a surface 11a and a back surface 11b opposite to the surface 11a. The second dielectric layer 12 is laminated on the surface 11a of the first dielectric layer 11. The second dielectric layer 12 has a higher relative dielectric constant than the first dielectric layer 11. The second dielectric layer 12 is a multilayer substrate. However, the second dielectric layer 12 may be a single layer.

[0013] The first dielectric layer 11 and the second dielectric layer 12 may be made of one or more of low temperature co-fired ceramics (LTCC), glass epoxy resin, liquid crystal polymer (LCP), fluororesin, polyimide resin, etc. Among these materials, LTCC has the highest relative dielectric constant, followed by glass epoxy resin, liquid crystal polymer, and fluororesin in that order.

[0014] For example, the relative dielectric constant of the first dielectric layer 11 is about 2, and a fluororesin is used as the material of the low-dielectric-constant first dielectric layer 11. The relative dielectric constant of the second dielectric layer 12 is about 7, and LTCC is used as the material of the high-dielectric-constant second dielectric layer 12.

[0015] The relative dielectric constants and materials of the first dielectric layer 11 and the second dielectric layer 12 are merely examples, and the combination of materials used for the first dielectric layer 11 and the second dielectric layer 12 can be changed as appropriate. By forming the first dielectric layer 11 and the second dielectric layer 12 from different types of materials, the relative dielectric constant of the first dielectric layer 11 and the relative dielectric constant of the second dielectric layer 12 can easily be made different.

[0016] 1 and 3, the first dielectric layer 11 and the second dielectric layer 12 are shown to have the same thickness, but this is not limiting. The thickness of the second dielectric layer 12 may be different from the thickness of the first dielectric layer 11. For example, the thickness of the second dielectric layer 12 may be thinner than the first dielectric layer 11. More preferably, the thickness of the second dielectric layer 12 is about λ / 4. Alternatively, the thickness of the second dielectric layer 12 may be λ / 4 or less.

[0017] The radiation electrode 21 is provided on the surface 11a of the first dielectric layer 11. The second dielectric layer 12 is provided to cover the radiation electrode 21. In other words, the radiation electrode 21 is located between the first dielectric layer 11 and the second dielectric layer 12 in the Z direction.

[0018] The ground electrode 22 is provided on the back surface 11b of the first dielectric layer 11. That is, the ground electrode 22 faces the radiation electrode 21 with the first dielectric layer 11 interposed therebetween. The radiation electrode 21 and the ground electrode 22 form a patch antenna. The antenna device 10 is formed by laminating the ground electrode 22, the first dielectric layer 11, the radiation electrode 21, and the second dielectric layer 12 in this order in the Z direction.

[0019] A via 23 penetrating the first dielectric layer 11 and a connection wiring 24 are connected to the feeding point of the radiation electrode 21. The connection wiring 24 is connected to an RFIC included in an external high-frequency circuit board. As a result, a high-frequency signal is supplied from the RFIC to the feeding point of the radiation electrode 21, and radio waves are emitted from the radiation electrode 21.

[0020] The radiation electrode 21 and the ground electrode 22 are made of a conductive metal material such as aluminum (Al), copper (Cu), gold (Au), or silver (Ag), or an alloy containing at least one of these materials.

[0021] 2 , the radiation electrode 21 and the ground electrode 22 each have a rectangular shape in a plan view. The electrode size of the ground electrode 22 is larger than the electrode size of the radiation electrode 21. That is, the width W2(x) of the ground electrode 22 in the X direction is larger than the width W1(x) of the radiation electrode 21 in the X direction. Furthermore, the width W2(y) of the ground electrode 22 in the Y direction is larger than the width W1(y) of the radiation electrode 21 in the Y direction.

[0022] Here, the width W2(x) can be rephrased as the length of each of two opposing sides of the ground electrode 22 in the Y direction. The width W2(y) can be rephrased as the length of each of two opposing sides of the ground electrode 22 in the X direction.

[0023] At least one of the width W2(x) and the width W2(y) of the ground electrode 22 is equal to or less than λ. More preferably, at least one of the width W2(x) and the width W2(y) of the ground electrode 22 is equal to or less than λ / 2.

[0024] 2, the radiation electrode 21 and the ground electrode 22 are square, but are not limited to this. The radiation electrode 21 and the ground electrode 22 may be rectangular. Furthermore, the radiation electrode 21 and the ground electrode 22 are not limited to a quadrangle, and may be polygonal, circular, or other shapes.

[0025] As shown in Fig. 2, the conductor wall 31 is provided along the outer edge of the radiation electrode 21 in a plan view. More specifically, the conductor wall 31 extends along the four sides of the radiation electrode 21 and surrounds the radiation electrode 21 to form a rectangular frame shape. As shown in Fig. 3, the conductor wall 31 extends along at least the thickness direction of the first dielectric layer 11 out of the first dielectric layer 11 and the second dielectric layer 12. The height position of the upper end of the conductor wall 31 is substantially equal to the height position of the upper surface of the radiation electrode 21. The lower end side of the conductor wall 31 is connected to the ground electrode 22. A reference potential (e.g., ground potential) is supplied to the conductor wall 31 through the ground electrode 22.

[0026] The conductive wall 31 is made of a conductive metal material. For example, the conductive wall 31 is made of the same material as the radiating electrode 21 and the ground electrode 22. However, the conductive wall 31 may be made of a different material from the radiating electrode 21 and the ground electrode 22.

[0027] In the first embodiment, the conductor wall 31 is formed in the form of a film on the side surface of the first dielectric layer 11. The conductor wall 31 is formed by, for example, sputtering. Alternatively, the conductor wall 31 is formed by applying a metal paste. This allows the conductor wall 31 to be formed thinner (the thickness of the conductor wall 31 in the X direction or the Y direction) than when the conductor wall 31 is formed using a via or the like that penetrates the first dielectric layer 11 in the Z direction, thereby enabling the antenna device 10 to be made smaller. Alternatively, because the conductor wall 31 can be made thinner, the area of ​​the radiation electrode 21 can be secured while the antenna device 10 is made smaller.

[0028] As described above, the antenna device 10 of this embodiment has the conductor walls 31 provided opposite the side surfaces (four sides) of the radiation electrode 21, and the ground electrode 22 provided opposite the lower surface of the radiation electrode 21. The upper surface of the radiation electrode 21 is covered with the second dielectric layer 12 made of a high-dielectric-constant material. This allows the antenna device 10 to be miniaturized and have broadband radiation characteristics. The miniaturization (size of the ground electrode 22) and radiation characteristics of the antenna device 10 will be described with reference to FIGS. 4 to 6.

[0029] 1 to 3 are merely examples and can be modified as appropriate. For example, the radiation electrode 21 is provided on the front surface 11a of the first dielectric layer 11, and the ground electrode 22 is provided on the back surface 11b of the first dielectric layer 11, but this is not limiting. The radiation electrode 21 may be provided on an inner layer of the first dielectric layer 11. The ground electrode 22 may also be provided on an inner layer of the first dielectric layer 11. In this case, the antenna device 10 is stacked in the Z direction in the following order: first dielectric layer 11, ground electrode 22, first dielectric layer 11, radiation electrode 21, first dielectric layer 11, and second dielectric layer 12.

[0030] Furthermore, the conductor wall 31 is formed in a frame shape surrounding the four sides of the radiation electrode 21, but is not limited to this. The conductor wall 31 may be provided extending along at least two opposing sides of the four sides of the radiation electrode 21, or may not be provided on any one of the four sides of the radiation electrode 21. Alternatively, a plurality of conductor walls 31 may be arranged at a distance from each other along the outer edge of the radiation electrode 21.

[0031] Example 1 Next, the antenna characteristics of the antenna device 10 of this embodiment will be described with reference to Fig. 4 to Fig. 6. Fig. 4 is a graph showing the relationship between the size of the ground electrode and the Q value of an antenna device according to a comparative example. Fig. 5 is a graph showing the frequency characteristics of return loss of the antenna devices according to Example 1 and the comparative example. Fig. 6 is a graph showing the relationship between the size of the ground electrode and the Q value of the antenna devices according to Example 1 and the comparative example.

[0032] The antenna device according to the comparative example shown in Fig. 4 has a configuration in which the second dielectric layer 12 and the conductor wall 31 are not included in the antenna device 10 of the first embodiment. The horizontal axis of the graph shown in Fig. 4 represents the size of the ground electrode (the width W2(x) or W2(y) of the ground electrode 22 in Fig. 2), and the vertical axis represents the Q value. The graph shown in Fig. 4 shows the results of a simulation of the Q value of the radiation characteristics under the conditions of a frequency of 28 GHz and a substrate dielectric constant of 3.

[0033] As shown in Figure 4, when the width of the ground electrode is 4 mm or more, the Q value is roughly constant. When the width of the ground electrode is 3.5 mm or less (approximately λ / 2 or less in electrical length), the Q value tends to increase. In other words, when the electrode size of the ground electrode is reduced, it may become difficult to achieve a broadband radiation characteristic.

[0034] 5 and 6 has the same configuration as the antenna device 10 of the first embodiment, and the first dielectric layer 11 has a relative dielectric constant of 3 and a thickness of 0.4 mm. The second dielectric layer 12 has a relative dielectric constant of 6 and a thickness of 0.8 mm. The widths W2(x) and W2(y) of the ground electrode 22 are each 3.0 mm.

[0035] The antenna device of Comparative Example 1 and Comparative Example 2 does not have the second dielectric layer 12 and the conductor wall 31, as compared to the antenna device of Example 1. The antenna device of Comparative Example 3 and Comparative Example 4 has the same configuration as the antenna device of Example 1 in that it has the second dielectric layer 12, but differs in that it does not have the conductor wall 31. The width of the ground electrodes of Comparative Examples 1 and 3 is 7.5 mm, and the width of the ground electrodes of Comparative Examples 2 and 4 is 3.0 mm. Note that Comparative Examples 1 and 2 are the same as some of the comparative examples shown in FIG. 4 described above (the widths of the ground electrodes are 7.5 mm and 3.0 mm).

[0036] 5 and 6 show the results of simulating the return loss and Q value for the example and comparative examples 1 to 4. The horizontal axis of the graph shown in Fig. 5 is frequency (GHz), and the vertical axis is the level (dB) of the S parameter S11. The horizontal axis of the graph shown in Fig. 6 is the width (mm) of the ground electrode, and the vertical axis is the Q value.

[0037] As shown in Figures 5 and 6, Comparative Examples 3 and 4 have a smaller Q value than Comparative Examples 1 and 2 because they include a second dielectric layer made of a high-dielectric-constant material. That is, Comparative Examples 3 and 4 have broader-band radiation characteristics than Comparative Examples 1 and 2. Comparative Examples 2 and 4 (3.0 mm), which have a smaller ground electrode width, have a larger Q value than Comparative Examples 1 and 3 (7.5 mm), which have a larger ground electrode width. Furthermore, in Comparative Examples 2 and 4 (3.0 mm), which have a smaller ground electrode width, the Q value of Comparative Example 4, which includes a second dielectric layer made of a high-dielectric-constant material, is less effective in suppressing the Q value than Comparative Example 2, which does not include a second dielectric layer. That is, when miniaturizing an antenna device, simply providing a second dielectric layer does not significantly improve the radiation characteristics.

[0038] 5 and 6, the antenna device according to the example is provided with the second dielectric layer 12 made of a high dielectric constant material and the conductor wall 31, and therefore, even when the width of the ground electrode is small (3.0 mm), it is possible to reduce the Q value compared to comparative examples 2 and 4. In other words, it is shown that the antenna device according to the example can be miniaturized and can satisfactorily achieve a wide band of radiation characteristics.

[0039] The relative dielectric constants and widths of the ground electrodes shown in Example 1 and the comparative examples are merely examples, and the invention is not limited to these.

[0040] Second Embodiment Fig. 7 is a cross-sectional view showing an antenna device according to a second embodiment. As shown in Fig. 7, the antenna device 10A according to the second embodiment differs from the first embodiment in that it has a first radiation electrode 25 and a second radiation electrode 26 as radiation electrodes. Furthermore, the antenna device 10A according to the second embodiment differs from the first embodiment in that the conductor wall 31A is formed inside the first dielectric layer 11, i.e., more inward than the side surface of the first dielectric layer 11.

[0041] The first radiation electrode 25 is provided between the first dielectric layer 11 and the second dielectric layer 12. The second radiation electrode 26 is provided on an inner layer of the first dielectric layer 11. That is, the second radiation electrode 26 is provided between the ground electrode 22 and the first radiation electrode 25 in the Z direction. The width (area in a plan view) of the first radiation electrode 25 is different from the width (area in a plan view) of the second radiation electrode 26. In the example shown in FIG. 7 , the area of ​​the first radiation electrode 25 is smaller than the area of ​​the second radiation electrode 26. Note that the first radiation electrode 25 is not limited to being provided on the surface 11 a of the first dielectric layer 11, and may be provided on an inner layer of the first dielectric layer 11.

[0042] The first radiation electrode 25 is a patch electrode for the high frequency side, and the second radiation electrode 26 is a patch electrode for the low frequency side. That is, the first radiation electrode 25 is electrically connected to an external RFIC (not shown) through a via 27. The second radiation electrode 26 is electrically connected to an external RFIC (not shown) through a via 28. The first radiation electrode 25 and the second radiation electrode 26 are configured to receive different high frequency signals from the external RFIC (not shown) and emit radio waves in different frequency bands.

[0043] Therefore, the antenna device 10A of this embodiment can operate in a plurality of frequency bands, and can achieve broadband radiation characteristics in each frequency band, similar to the first embodiment described above.

[0044] Furthermore, the conductor wall 31A of this embodiment includes a plurality of vias 33 arranged in the thickness direction (Z direction) of the first dielectric layer 11, and a plurality of connection pads 34 connecting the plurality of vias 33 arranged in the Z direction. The plurality of vias 33 and the connection pads 34 are alternately connected from the front surface 11a to the back surface 11b of the first dielectric layer 11. The lower ends of the plurality of vias 33 and the plurality of connection pads 34 connected in the Z direction are connected to the ground electrode 22. Furthermore, a group of the plurality of vias 33 and the plurality of connection pads 34 connected in the Z direction are arranged in multiple rows along the outer edges of the first radiation electrode 25 and the second radiation electrode 26. As a result, the plurality of vias 33 and the plurality of connection pads 34 are electrically formed as the conductor wall 31A.

[0045] The conductive wall 31A of this embodiment can be formed in the same process as the process for forming the first radiation electrode 25, the second radiation electrode 26, the vias 27, 28, etc. Therefore, in this embodiment, the conductive wall 31A can be easily formed. Furthermore, since the conductive wall 31A has a greater degree of freedom in placement than the conductive wall 31 of the first embodiment, it can be placed between adjacent radiation electrodes even when configured as an array antenna.

[0046] In this embodiment, the length of each of the two sides of the ground electrode 22 that face each other in the X direction and extend in the Y direction is λ or less. More preferably, the length of each of the two sides of the ground electrode 22 that face each other in the X direction and extend in the Y direction is λ / 2 or less. The antenna device 10A can obtain wideband radiation characteristics even when configured as an array antenna with a narrow width in the Y direction.

[0047] 8 is a plan view showing an antenna device according to a third embodiment. As shown in Fig. 8, the antenna device 10B according to the third embodiment is different from the above-described embodiments in that it is an array antenna in which a plurality of radiation electrodes 21 are arranged in the X direction.

[0048] Although not shown in the drawings, the plurality of radiation electrodes 21 are provided on a common first dielectric layer 11. The second dielectric layer 12 is provided to cover the plurality of radiation electrodes 21. That is, the first dielectric layer 11 and the second dielectric layer 12 are provided continuously over the plurality of radiation electrodes 21. The ground electrode 22 is formed as a common electrode for the plurality of radiation electrodes 21.

[0049] The conductor walls 31B are provided to surround each of the plurality of radiation electrodes 21. The conductor walls 31B can be a combination of the conductor walls 31 of the first embodiment and the conductor walls 31A of the second embodiment. That is, among the conductor walls 31B, the conductor walls 31Ba located on the outer periphery of the plurality of radiation electrodes 21 are configured with a conductor film covering the side surface of the first dielectric layer 11, similar to the conductor walls 31 of the first embodiment. Furthermore, among the conductor walls 31B, the conductor walls 31Bb located between the plurality of radiation electrodes 21 adjacent to each other in the X direction are configured by connecting a plurality of vias 33 and a plurality of connection pads 34, similar to the conductor wall 31A of the second embodiment.

[0050] As a result, the thickness of the conductor wall 31Ba located on the periphery (thickness in the direction perpendicular to the side surface of the first dielectric layer 11) can be made thinner than the conductor wall 31Bb, thereby enabling the miniaturization of the antenna device 10B. Furthermore, since the conductor wall 31B is provided on each of the plurality of radiation electrodes 21, the array antenna can also achieve a broadband radiation characteristic, as in the first embodiment described above.

[0051] (First Modification of Third Embodiment) Fig. 9 is a plan view showing an antenna device according to a first modification of the third embodiment. As shown in Fig. 9, the antenna device 10C according to the first modification of the third embodiment differs from the third embodiment in that it is an array antenna in which a plurality of radiation electrodes 21 are arranged in the X direction and also in the Y direction.

[0052] In other words, the radiation electrodes 21 are arranged in a matrix. The antenna device 10C is configured as a two-dimensional array antenna.

[0053] Moreover, the conductor walls 31C are provided so as to surround each of the plurality of radiation electrodes 21. In the first modification, among the conductor walls 31C, the conductor walls 31Ca located on the outer peripheries of the plurality of radiation electrodes 21 are also made of a conductor film covering the side surface of the first dielectric layer 11, similar to the conductor walls 31 of the first embodiment. Among the conductor walls 31C, the conductor walls 31Cb located between the plurality of radiation electrodes 21 adjacent to each other in the X direction and the conductor walls 31Cc located between the plurality of radiation electrodes 21 adjacent to each other in the Y direction are each configured by connecting a plurality of vias 33 and a plurality of connection pads 34, similar to the conductor walls 31A of the second embodiment.

[0054] (Fourth embodiment) Fig. 10 is a perspective view showing an antenna device according to a fourth embodiment. Fig. 11 is a cross-sectional view taken along the line XI-XI' of Fig. 10. Note that Fig. 11 shows a cross-sectional view of a portion of the antenna device 10D, i.e., a portion of the antenna device 10D corresponding to one first radiation electrode 25 and one of the plurality of second radiation electrodes 26 out of the plurality of first radiation electrodes 25 and the plurality of second radiation electrodes 26. As shown in Figs. 10 and 11 , the antenna device 10D according to the fourth embodiment differs from the above-described embodiments and modifications in that the conductor wall 31D includes a first conductor wall 35 and a second conductor wall 36.

[0055] The antenna device 10D of this embodiment has a plurality of first radiation electrodes 25 and a plurality of second radiation electrodes 26, which are arranged in the X direction. The configurations of the first radiation electrode 25, the second radiation electrode 26, the first dielectric layer 11, and the second dielectric layer 12 are the same as those of the second embodiment described above (see FIG. 7 ), and therefore repeated description will be omitted.

[0056] The first conductor wall 35 is provided on the first dielectric layer 11 and is provided along the thickness direction (Z direction) of the first dielectric layer 11. In this embodiment, the height of the first conductor wall 35 is equal to the thickness of the first dielectric layer 11. The multiple first conductor walls 35 each extend along the Y direction and are arranged in the X direction. The first conductor wall 35 is disposed between the multiple first radiation electrodes 25 adjacent to each other in the X direction and the multiple second radiation electrodes 26 adjacent to each other in the X direction.

[0057] The second dielectric layer 12 is provided to cover the first radiation electrode 25, the second radiation electrode 26, the first dielectric layer 11, and the first conductor wall 35. The second conductor wall 36 is provided on the second dielectric layer 12, overlapping with the first conductor wall 35. In other words, the second dielectric layer 12 is arranged between the first conductor wall 35 and the second conductor wall 36 in the Z direction. The second conductor wall 36 is provided spaced apart from the first conductor wall 35 and not in contact with it. Furthermore, the multiple second conductor walls 36 overlap with the first conductor wall 35 and extend in the same direction as the first conductor wall 35. In other words, the multiple second conductor walls 36 each extend along the Y direction and are arranged in the X direction. The second conductor walls 36 are arranged between the multiple first radiation electrodes 25 adjacent to each other in the X direction and between the multiple second radiation electrodes 26 adjacent to each other in the X direction.

[0058] In this embodiment, the conductor walls 31D (the first conductor wall 35 and the second conductor wall 36) do not have a portion extending in the X direction. That is, the conductor walls 31D are provided along two of the four sides of each of the first radiation electrode 25 and the second radiation electrode 26 that face each other in the X direction. Furthermore, the conductor walls 31D are not provided along two of the four sides of each of the first radiation electrode 25 and the second radiation electrode 26 that face each other in the Y direction.

[0059] The first conductor wall 35 and the second conductor wall 36 are formed of a conductive metal material such as aluminum (Al) or copper (Cu), or an alloy containing at least one of these materials.

[0060] The lower end side of the first conductive wall 35 is connected to the ground electrode 22 and is supplied with a reference potential (e.g., ground potential). As described above, the second conductive wall 36 is not in contact with the first conductive wall 35. The second conductive wall 36 may be connected to the reference potential at any point, or may be floating, i.e., not supplied with a fixed potential such as the reference potential.

[0061] In this embodiment, the first conductor wall 35 and the second conductor wall 36 are provided, which suppresses the current flowing on the second dielectric layer 12 and allows for good radiation characteristics to be obtained. The radiation characteristics of the antenna device 10D will be described later with reference to Figs. 15 to 19.

[0062] 12 is a cross-sectional view showing a part of an antenna device according to a second modification of the fourth embodiment. As shown in Fig. 12, the antenna device 10E according to the second modification is different from the antenna device 10D of the fourth embodiment in that the second conductor wall 36 of the conductor wall 31E is in contact with the first conductor wall 35.

[0063] The second conductor wall 36 is provided to overlap the first conductor wall 35, and the first conductor wall 35 and the second conductor wall 36 are provided in direct contact with each other. An opening is provided in the second dielectric layer 12 in a region overlapping with the second conductor wall 36, and the second conductor wall 36 is in contact with the first conductor wall 35 through the opening in the second dielectric layer 12. The second conductor wall 36 is in contact with a side surface (side surface of the opening) of the second dielectric layer 12. In this embodiment, the height of the second conductor wall 36 is greater than the height (film thickness) of the second dielectric layer 12. The upper surface of the second conductor wall 36 is provided to protrude in the Z direction from the upper surface of the second dielectric layer 12.

[0064] Even with this configuration, the antenna device 10E according to the second modified example can suppress the current flowing on the second dielectric layer 12, as in the fourth embodiment, and can obtain good radiation characteristics.

[0065] (Third Modification of Fourth Embodiment) Fig. 13 is a perspective view showing an antenna device according to a third modification of the fourth embodiment. As shown in Fig. 13, the antenna device 10F according to the third modification is different from the fourth embodiment described above in that the second conductor wall 36A of the conductor wall 31F has a ladder shape.

[0066] The conductor wall 31F includes a first conductor wall 35A and a second conductor wall 36A. The first conductor wall 35A is similar to the first conductor wall 35 described in the fourth embodiment, and a repeated description will be omitted. The second conductor wall 36A has a plurality of first portions 36Aa and a plurality of second portions 36Ab. The plurality of first portions 36Aa are provided so as to overlap with the plurality of first conductor walls 35A, respectively. That is, the plurality of first portions 36Aa each extend in the Y direction and are arranged in the X direction.

[0067] The multiple second portions 36Ab each extend in the X direction and are spaced apart in the Y direction. One end of each of the multiple first portions 36Aa is connected to one of the second portions 36Ab, and the other end of each of the multiple first portions 36Aa is connected to the other of the second portions 36Ab. This forms the second conductor wall 36A in a ladder shape. The first radiation electrode 25 and the second radiation electrode 26 are arranged in an area defined by the two first portions 36Aa and the two second portions 36Ab.

[0068] In the third modified example, the second conductor wall 36A and the first conductor wall 35A are stacked without contact with each other with the second dielectric layer 12 sandwiched therebetween, as in the fourth embodiment. However, the second conductor wall 36A and the first conductor wall 35A may be stacked in direct contact with each other, as in the second modified example (see FIG. 12 ). Furthermore, the configuration is not limited to one in which the multiple first conductor walls 35A are arranged in the X direction, and the first conductor wall 35A may also be formed in a ladder shape, similar to the second conductor wall 36A. In other words, the first conductor wall 35A may be provided so as to surround each of the multiple first radiation electrodes 25 and the multiple second radiation electrodes 26.

[0069] (Examples 2 to 6) Next, radiation patterns of antenna devices according to Examples 2 to 6 will be described with reference to Figs. 14 to 19. Fig. 14 is an explanatory diagram for explaining the polarization direction and polar angle of the antenna devices according to Examples 2 to 6. Fig. 15 is a graph showing the radiation pattern of the antenna device according to Example 2. Fig. 16 is a graph showing the radiation pattern of the antenna device according to Example 3. Fig. 17 is a graph showing the radiation pattern of the antenna device according to Example 4. Fig. 18 is a graph showing the radiation pattern of the antenna device according to Example 5. Fig. 19 is a graph showing the radiation pattern of the antenna device according to Example 6.

[0070] Although FIG. 14 illustrates the antenna device 10D according to the fourth embodiment, the description of the polarization direction and polar angle of the antenna device 10D can be applied to any of the second to sixth embodiments.

[0071] 14 , of the radio waves radiated from the first radiation electrode 25 and the second radiation electrode 26 of the antenna device 10D, the waves polarized in the Y direction are referred to as vertical polarization V-pol, and the waves polarized in the X direction are referred to as horizontal polarization H-pol. Furthermore, the angle of the direction tilting in the X direction with respect to the direction perpendicular to the surfaces of the first radiation electrode 25 and the second radiation electrode 26 (Z direction) is referred to as the X-direction polar angle θ(x). Furthermore, the angle of the direction tilting in the Y direction with respect to the direction perpendicular to the surfaces of the first radiation electrode 25 and the second radiation electrode 26 (Z direction) is referred to as the Y-direction polar angle θ(y).

[0072] An antenna device according to a second example shown in FIG. 15 is configured similarly to the antenna device 10D of the fourth embodiment (see FIGS. 10 and 11 ) without the second conductive wall 36. An antenna device according to a third example shown in FIG. 16 is configured similarly to the antenna device 10D of the fourth embodiment (see FIGS. 10 and 11 ). An antenna device according to a fourth example shown in FIG. 17 is configured similarly to the antenna device 10F of the third modified example (see FIG. 13 ). An antenna device according to a fifth example shown in FIG. 18 is configured similarly to the antenna device 10E of the second modified example (see FIG. 12 ). An antenna device according to a sixth example shown in FIG. 19 is configured similarly to the antenna device 10F of the third modified example (see FIG. 13 ) with the second conductive wall 36A and the first conductive wall 35A stacked in direct contact with each other.

[0073] The graphs shown in FIGS. 15 to 19 show the results of simulating the radiation patterns of the antenna devices according to Examples 2 to 6. The horizontal axis of each graph represents the polar angle (deg.). The vertical axis of each graph represents the gain (dB). The radiation pattern of vertically polarized wave V-pol (upper row) and the radiation pattern of horizontally polarized wave H-pol (lower row) are shown for each of Examples 2 to 6. The radiation patterns of different frequency bands (low band (left side) and high band (right side)) are also shown for each of Examples 2 to 6. For example, the high frequency band (high band) corresponds to the radiation pattern of the first radiation electrode 25, and the low-high frequency band (low band) corresponds to the radiation pattern of the second radiation electrode 26.

[0074] 15 to 19, for both the radiation patterns of vertically polarized waves V-pol and horizontally polarized waves H-pol, the antenna devices according to Examples 3 to 6, which have the second conductive walls 36, 36A, have smoother radiation patterns when the polar angle in the X direction is changed, compared to Example 2, which does not have the second conductive walls 36, 36A. That is, it was shown that Examples 3 to 6 have less variation in gain when the polar angle in the X direction is changed, compared to Example 2.

[0075] Furthermore, it was shown that in Examples 3 to 6, compared to Example 2, the antenna gain at a polar angle of 0° (Z direction) was greater in the radiation pattern at least in the high frequency band (High band).

[0076] The above-described embodiment is intended to facilitate understanding of the present invention, and is not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit and scope of the present invention, and equivalents thereof are also included in the present invention.

[0077] The present disclosure may also have the following configurations.

[0078] (1) An antenna device comprising: a first dielectric layer; a radiation electrode provided on the first dielectric layer; a second dielectric layer having a higher dielectric constant than the first dielectric layer and covering the radiation electrode; a ground electrode facing the radiation electrode across the first dielectric layer and provided on the opposite side of the second dielectric layer; and a conductor wall extending along a thickness direction of at least the first dielectric layer of the first and second dielectric layers and provided along an outer edge of the radiation electrode in a planar view. (2) The antenna device described in (1), in which the conductor wall is provided to surround the radiation electrode in a planar view. (3) The antenna device described in (1) or (2), in which the radiation electrode includes: a first radiation electrode; and a second radiation electrode having an area different from that of the first radiation electrode and provided between the first radiation electrode and the ground electrode. (4) The antenna device described in any one of (1) to (3), in which the conductor wall is provided on the first dielectric layer and the second dielectric layer. (5) The antenna device according to any one of (1) to (4), including a plurality of the radiation electrodes, the plurality of radiation electrodes being arranged in a first direction parallel to the surface of the first dielectric layer, and the conductive wall being provided to surround each of the plurality of radiation electrodes. (6) The antenna device according to (5), wherein the plurality of radiation electrodes are arranged in the first direction and also in a second direction orthogonal to the first direction. (7) The antenna device according to any one of (1) to (6), wherein the conductive wall includes a plurality of vias arranged in a thickness direction of the first dielectric layer and a plurality of connection pads connecting the plurality of vias arranged in the thickness direction. (8) The antenna device according to any one of (1) to (6), wherein the conductive wall is provided in the form of a film on at least a side surface of the first dielectric layer. (9) The antenna device described in any one of (1) to (8), wherein the conductor wall includes a first conductor wall provided on the first dielectric layer and a second conductor wall provided overlapping the first conductor wall, and the second dielectric layer is disposed between the first conductor wall and the second conductor wall.(10) The antenna device according to any one of (1) to (8), wherein the conductor wall includes a first conductor wall provided on the first dielectric layer and a second conductor wall provided overlapping the first conductor wall, and the first conductor wall and the second conductor wall are provided in direct contact with each other. (11) The antenna device according to (9) or (10), wherein the antenna device has a plurality of the radiation electrodes, wherein the plurality of radiation electrodes are arranged in a first direction, and the first conductor wall and the second conductor wall extend in a second direction orthogonal to the first direction and are disposed between the plurality of radiation electrodes arranged in the first direction in a planar view. (12) The antenna device according to (9) or (10), wherein the antenna device has a plurality of the radiation electrodes, wherein the plurality of radiation electrodes are arranged in a first direction, and at least the second conductor wall of the first conductor wall and the second conductor wall extends in the first direction and also in a second direction orthogonal to the first direction and is disposed to surround each of the plurality of radiation electrodes in a planar view. (13) The antenna device according to any one of (1) to (12), wherein the ground electrode includes at least two opposing sides, and each of the two opposing sides has a length of λ or less. (14) The antenna device according to any one of (1) to (12), wherein the ground electrode includes at least two opposing sides, and each of the two opposing sides has a length of λ / 2 or less.

[0079] REFERENCE SIGNS LIST 10, 10A, 10B, 10C, 10D, 10E, 10F Antenna device 11 First dielectric layer 12 Second dielectric layer 21 Radiation electrode 22 Ground electrode 23, 27, 28, 33 Via 24 Connection wiring 25 First radiation electrode 26 Second radiation electrode 31, 31A, 31B, 31C, 31D, 31E, 31F Conductive wall 34 Connection pad 35, 35A First conductive wall 36, 36A Second conductive wall

Claims

1. An antenna device comprising: a first dielectric layer; a radiating electrode provided on the first dielectric layer; a second dielectric layer having a higher dielectric constant than the first dielectric layer and covering the radiating electrode; a ground electrode facing the radiating electrode across the first dielectric layer and provided on the opposite side of the second dielectric layer; and a conductor wall extending along at least the thickness direction of the first dielectric layer of the first and second dielectric layers and provided along an outer edge of the radiating electrode in a planar view.

2. The antenna device according to claim 1, wherein the conductive wall is disposed so as to surround the radiation electrode in a plan view.

3. The antenna device according to claim 1 or 2, wherein the radiation electrode includes: a first radiation electrode; and a second radiation electrode having an area different from that of the first radiation electrode and provided between the first radiation electrode and the ground electrode.

4. The antenna device according to any one of claims 1 to 3, wherein the conductor wall is provided on the first dielectric layer and the second dielectric layer.

5. An antenna device as described in any one of claims 1 to 4, comprising a plurality of the radiation electrodes, the plurality of radiation electrodes being arranged in a first direction parallel to the surface of the first dielectric layer, and the conductor wall being arranged to surround each of the plurality of the radiation electrodes.

6. The antenna device according to claim 5, wherein the plurality of radiation electrodes are arranged in the first direction and in a second direction perpendicular to the first direction.

7. An antenna device as described in any one of claims 1 to 6, wherein the conductive wall includes a plurality of vias arranged in the thickness direction of the first dielectric layer, and a plurality of connection pads connecting the plurality of vias arranged in the thickness direction.

8. The antenna device according to any one of claims 1 to 6, wherein the conductor wall is provided in the form of a film on at least a side surface of the first dielectric layer.

9. An antenna device as described in any one of claims 1 to 8, wherein the conductor wall includes a first conductor wall provided on the first dielectric layer and a second conductor wall provided overlapping the first conductor wall, and the second dielectric layer is disposed between the first conductor wall and the second conductor wall.

10. An antenna device as described in any one of claims 1 to 8, wherein the conductor wall includes a first conductor wall provided on the first dielectric layer and a second conductor wall provided overlapping the first conductor wall, and the first conductor wall and the second conductor wall are provided in direct contact with each other.

11. An antenna device as described in claim 9 or claim 10, comprising a plurality of the radiation electrodes, the plurality of radiation electrodes being arranged in a first direction, the first conductor wall and the second conductor wall extending in a second direction perpendicular to the first direction and being disposed between the plurality of the radiation electrodes arranged in the first direction in a planar view.

12. An antenna device as described in claim 9 or claim 10, comprising a plurality of the radiation electrodes, the plurality of radiation electrodes being arranged in a first direction, and at least the second conductor wall of the first conductor wall and the second conductor wall extending in the first direction and also extending in a second direction perpendicular to the first direction, and being arranged to surround each of the plurality of radiation electrodes in a planar view.

13. The antenna device according to any one of claims 1 to 12, wherein the ground electrode includes at least two opposing sides, and the length of each of the two opposing sides is equal to or less than λ.

14. The antenna device according to any one of claims 1 to 12, wherein the ground electrode includes at least two opposing sides, and each of the two opposing sides has a length of λ / 2 or less.

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