Unit structure and radio wave control plate

Abstract

This unit structure constitutes a resonator and comprises a first electrode that that is disposed on a first surface and a second electrode that is disposed on a second surface separate from the first surface in a first direction. In a plan view from a direction orthogonal to the first surface and the second surface, the second electrode has an opening. The first electrode is constituted by one or more electrodes. In a plan view from a direction orthogonal to the first surface and the second surface, at least one electrode constituting the first electrode has one end part that overlaps with the second electrode and another end part that does not overlap with the second electrode.

Description

Unit structure and radio wave control board

[0001] The present disclosure relates to a unit structure and a radio wave control plate.

[0002] There are known techniques for controlling electromagnetic waves without using a dielectric lens. For example, Patent Document 1 describes a technique for refracting radio waves by changing the parameters of each element in a structure in which resonator elements are arranged.

[0003] JP 2015-231182 A

[0004] The unit structure of the present disclosure constitutes a resonator and comprises a first electrode arranged on a first surface and a second electrode arranged on a second surface spaced apart from the first surface in a first direction, wherein, when viewed in a plane from a direction perpendicular to the first and second surfaces, the second electrode has an opening and the first electrode is composed of one or more electrodes, and when viewed in a plane from a direction perpendicular to the first and second surfaces, at least one of the electrodes constituting the first electrode has one end overlapping the second electrode and the other end not overlapping the second electrode.

[0005] The radio wave control plate of the present disclosure includes a plurality of unit structures of the present disclosure.

[0006] FIG. 1 is a diagram for explaining an overview of a radio wave control plate. FIG. 2 is a diagram showing an example of the configuration of a radio wave control plate according to a comparative example. FIG. 3 is a diagram showing an example of the configuration of a unit structure according to a comparative example. FIG. 4 is a diagram showing analysis conditions for the Q value according to the first embodiment. FIG. 5 is a diagram showing an example of the configuration of a unit structure according to a comparative example. FIG. 6 is a diagram showing an example of the configuration of a unit structure according to the first embodiment. FIG. 7 is a diagram showing an example of the configuration of a unit structure according to a modified example of the first embodiment. FIG. 8 is a diagram showing an example of the configuration of a unit structure according to the second embodiment.

[0007] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to this embodiment, and in the following embodiments, the same components are designated by the same reference numerals, and redundant explanations will be omitted.

[0008] In the following description, an XYZ Cartesian coordinate system is set, and the positional relationship of each part will be described with reference to this XYZ Cartesian coordinate system. The direction parallel to the X axis in a horizontal plane is defined as the X-axis direction, the direction parallel to the Y axis in the horizontal plane perpendicular to the X axis is defined as the Y-axis direction, and the direction parallel to the Z axis perpendicular to the horizontal plane is defined as the Z-axis direction. Furthermore, the plane including the X axis and Y axis will be referred to as the XY plane as appropriate, the plane including the X axis and Z axis will be referred to as the XZ plane as appropriate, and the plane including the Y axis and Z axis will be referred to as the YZ plane as appropriate. The XY plane is parallel to the horizontal plane. The XY plane, XZ plane, and YZ plane are perpendicular to each other.

[0009] [Outline] (Radio wave control board) An outline of the radio wave control board will be described with reference to Fig. 1. Fig. 1 is a diagram for explaining the outline of the radio wave control board.

[0010] The radio wave control board 1 is a plate-shaped member configured to be able to reflect or transmit (refract) radio waves transmitted from a base station. For example, when receiving radio waves transmitted from a base station, the radio wave control board 1 is configured to reflect or refract the radio waves at a predetermined angle. The radio wave control board 1 can be configured, for example, from a metamaterial that changes the phase of the incident wave.

[0011] 1, radio wave control board 1 may include, for example, substrate 2 and unit structures 10a, 10b, 10c, and 10d. When there is no need to distinguish between unit structures 10a to 10d, they will be collectively referred to as unit structures 10.

[0012] The unit structures 10a, 10b, 10c, and 10d may be formed on a substrate 2. The substrate 2 may be, for example, a dielectric substrate made of a dielectric material. The substrate 2 may have, for example, but is not limited to, a rectangular shape. The unit structures 10a, 10b, 10c, and 10d may be arranged two-dimensionally.

[0013] In the radio wave control board 1, a plurality of unit structures 10a are arranged along the X-axis direction on one tier. A plurality of unit structures 10b are arranged along the X-axis direction on the tier above the tier on which unit structures 10a are arranged. A plurality of unit structures 10c are arranged along the X-axis direction on the tier above the tier on which unit structures 10b are arranged. A plurality of unit structures 10d are arranged along the X-axis direction on the tier above the tier on which unit structures 10c are installed. In the example shown in FIG. 1 , unit structures 10a, unit structures 10b, unit structures 10c, and unit structures 10d are arranged periodically along the Y-axis direction.

[0014] In this embodiment, unit structure 10a, unit structure 10b, unit structure 10c, and unit structure 10d are all different in size. In the example shown in FIG. 1 , unit structure 10a is the largest, followed by unit structure 10b, unit structure 10c, and unit structure 10d in order of size. That is, in this embodiment, radio wave control plate 1 has a structure in which a plurality of unit structures 10 of different sizes are periodically arranged. Here, radio wave control plate 1 is not limited to a structure in which a plurality of unit structures 10 of different sizes are periodically arranged, as long as a plurality of unit structures of different phase change amounts are periodically arranged.

[0015] The unit structures 10a to 10d may each have a different phase shift amount of the received radio waves. That is, the unit structures 10a to 10d are periodically arranged so as to have a gradient in the phase shift amount. The unit structures 10a to 10d each have a rectangular shape, but are not limited to this. For example, the phase shift amount of the reflected or refracted radio waves can be adjusted by changing only one or a combination of two or more of the size, shape, and dielectric constant of the unit structures 10a to 10d. When a material with a controllable dielectric constant, such as liquid crystal, is used for the unit structures, simply by periodically arranging unit structures of the same size and shape, the frequency band and phase shift amount of the reflected or refracted radio waves can be adjusted.

[0016] [Comparative Example] A radio wave control plate and a configuration example of a unit structure according to a comparative example will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a diagram showing a configuration example of a radio wave control plate according to a comparative example. Fig. 3 is a diagram showing a configuration example of a unit structure according to a comparative example.

[0017] 2, the radio wave control plate 1 has a plurality of unit structures 10. The unit structures 10 are periodically arranged in the XY plane. The radio wave control plate 1 is configured to refract radio waves W1 arriving from, for example, the −Z axis direction in a predetermined direction and emit transmitted waves W2.

[0018] As shown in FIGS. 2 and 3, the unit structure 10 includes a first electrode 12, a second electrode 14, and a liquid crystal layer 16.

[0019] The first electrode 12 is disposed on the top surface of the unit feature 10. The top surface of the unit feature 10 is also referred to as the first surface. The first electrode 12 is formed of a conductor. The first electrode 12 is a λ / 2 resonator. λ is the effective wavelength of the radio waves transmitted or reflected by the radio wave control plate 1.

[0020] The second electrode 14 is disposed on the bottom surface of the unit feature 10, away from the first electrode 12 in the Z-axis direction. The Z-axis direction is also referred to as the first direction. The bottom surface of the unit feature 10 is also referred to as the second surface. The second electrode 14 is formed of a conductor. The second electrode 14 is a ground conductor.

[0021] The liquid crystal layer 16 is disposed between the first electrode 12 and the second electrode 14. The liquid crystal layer 16 extends in the XY plane. When a voltage V1 is applied between the first electrode 12 and the second electrode 14, the orientation state of the liquid crystal molecules 18 contained in the liquid crystal layer 16 changes depending on the magnitude of the voltage V1. The change in the orientation state of the liquid crystal molecules 18 changes the capacitance value of the unit feature 10. By adjusting the capacitance value of the unit feature 10, the refraction direction or reflection direction of the radio wave can be changed.

[0022] Here, because the thickness of the liquid crystal layer 16 is several μm (micrometers), the distance between the first electrode 12 and the second electrode 14 is short. If the distance between the first electrode 12 and the second electrode 14 becomes short, there is a problem that loss in the unit structure 10 increases. In the present disclosure, even when the distance between the first electrode 12 and the second electrode 14 is short, an increase in loss is suppressed by providing an opening in the second electrode 14 and adjusting the degree of overlap between the first electrode 12 and the second electrode 14.

[0023] [First embodiment] (Analysis conditions for Q value) Analysis conditions for the Q value of the unit structure according to the first embodiment will be described with reference to Fig. 4. Fig. 4 is a diagram showing the analysis conditions for the Q value according to the first embodiment.

[0024] As shown in Figure 4, the Q value was calculated under the condition that a glass substrate 20 was placed on the first electrode 12 of the unit structure 10 and a glass substrate 22 was placed on the second electrode 14 of the unit structure 10. The electrical conductivity of the first electrode 12 and the second electrode 14 was 5.7 x 10 ６ The liquid crystal layer 16 has a dielectric constant of 5.07, a dielectric loss tangent of 0, and a thickness of 30 μm. The glass substrates 20 and 22 have a dielectric constant of 5.6, a dielectric loss tangent of 0, and a thickness of 0.3 mm.

[0025] (Configuration Example of Comparative Example) A configuration example of a unit structure according to a comparative example will be described with reference to Fig. 5. Fig. 5 is a diagram showing a configuration example of a unit structure according to a comparative example.

[0026] FIG. 5 shows the positional relationship between a first electrode 12A disposed on the upper surface and a second electrode 14A disposed on the lower surface of a unit structure 10A according to a comparative example.

[0027] The first electrode 12A is formed in a rectangular shape.

[0028] The second electrode 14A is formed in a rectangular shape. The second electrode 14A has an opening 30, an opening 32, an opening 34, and an opening 36. The openings 30, 32, 34, and 36 are formed in a triangular shape. The second electrode 14A includes a linear portion 40 and a linear portion 42.

[0029] The straight line portion 40 is formed on one diagonal of the second electrode 14. The straight line portion 42 is formed on the other diagonal of the second electrode 14.

[0030] When viewed from the Z-axis direction, the first electrode 12A and the linear portion 40 overlap one diagonal of the first electrode 12A. When viewed from the Z-axis direction, the first electrode 12A and the linear portion 42 overlap the other diagonal of the first electrode 12A.

[0031] A simulation analysis of the operating frequency and the Q value was carried out for the unit structure 10A shown in Fig. 5. As a result, the operating frequency of the unit structure 10A was 21.0146 [GHz] and the Q value was 18.

[0032] (Configuration Example of First Embodiment) A configuration example of a unit structure according to the first embodiment will be described with reference to Fig. 6. Fig. 6 is a diagram showing a configuration example of a unit structure according to the first embodiment.

[0033] FIG. 6 shows the positional relationship between a first electrode 12B disposed on the upper surface of a unit structure 10B according to the first embodiment and a second electrode 14B disposed on the lower surface thereof.

[0034] As shown in Fig. 6, the unit structure 10B includes first electrodes 12B, which are first electrodes 12Ba, 12Bb, 12Bc, and 12Bd. The first electrodes 12Ba to 12Bd are formed in a thin rectangular shape. The first electrodes 12Ba to 12Bd are approximately the same size. The first electrodes 12Ba to 12Bd are electrodes that constitute a λ / 2 resonator.

[0035] The second electrode 14B is formed in a rectangular shape. The second electrode 14B has an opening 60. The opening 60 is square-shaped, but is not limited to this. The opening 60 may be formed in, for example, a circular shape. The opening 60 may have any shape as long as it has approximately rotational symmetry in the XY plane, for example. Because the second electrode 14B has a rotational symmetry shape, two resonances occur at the same frequency as orthogonal modes. The second electrode 14B is a ground conductor.

[0036] The first electrode 12Ba has an end 50a and an end 50b. When viewed from the Z-axis direction, the end 50a and the second electrode 14B overlap. When viewed from the Z-axis direction, the end 50b and the second electrode 14B do not overlap. In other words, when viewed from the Z-axis direction, only one of the end 50a and the end 50b overlaps with the second electrode 14B.

[0037] The first electrode 12Bb has an end 52a and an end 52b. When viewed from the Z-axis direction, the end 52a and the second electrode 14B overlap. The degree of overlap between the end 52a and the second electrode 14B is the same as the degree of overlap between the end 50a of the first electrode 12Ba and the second electrode 14B. When viewed from the Z-axis direction, the end 52b and the second electrode 14B do not overlap. In other words, when viewed from the Z-axis direction, only one of the end 52a and the end 52b overlaps with the second electrode 14B.

[0038] The first electrode 12Bc has an end 54a and an end 54b. When viewed from the Z-axis direction, the end 54a overlaps with the second electrode 14B. The degree of overlap between the end 54a and the second electrode 14B is the same as the degree of overlap between the end 50a of the first electrode 12Ba and the second electrode 14B. When viewed from the Z-axis direction, the end 54b does not overlap with the second electrode 14B. In other words, when viewed from the Z-axis direction, only one of the end 54a and the end 54b overlaps with the second electrode 14B.

[0039] The first electrode 12Bd has an end 56a and an end 56b. When viewed from the Z-axis direction, the end 56a overlaps with the second electrode 14B. The degree of overlap between the end 56a and the second electrode 14B is the same as the degree of overlap between the end 50a of the first electrode 12Ba and the second electrode 14B. When viewed from the Z-axis direction, the end 56b does not overlap with the second electrode 14B. In other words, when viewed from the Z-axis direction, only one of the end 56a and the end 56b overlaps with the second electrode 14B, and the other end does not overlap with the second electrode 14B.

[0040] By applying a voltage between the second electrode 14B and the end 50a, the end 52a, the end 54a, and the end 56a, the orientation state of the liquid crystal molecules 18 in the liquid crystal layer 16 can be changed, thereby changing the capacitance value of the unit structure 10B. In other words, by applying a voltage between the second electrode 14B and the end 50a, the end 52a, the end 54a, and the end 56a, the refraction direction or transmission direction of the radio wave can be adjusted.

[0041] That is, when viewed from the Z-axis direction, the first electrodes 12Ba to 12Bd are each arranged such that only one of their two ends overlaps the second electrode 14B. Because the degree of overlap between each end and the second electrode 14B is approximately the same, the first electrodes 12Ba to 12Bd and the second electrode 14B are arranged to have approximately rotational symmetry in the XY plane. By arranging the first electrodes 12Ba to 12Bd and the second electrode 14B to have approximately rotational symmetry in the XY plane, two polarized waves that are orthogonal to each other can be transmitted or reflected. In this embodiment, the end of the first electrode is, for example, a region shorter than half the length of the long side of the first electrode.

[0042] A simulation analysis of the operating frequency and Q value was performed for the unit structure 10B shown in Fig. 6. As a result, the operating frequency of the unit structure 10B was 28.396 GHz, and the Q value was 245. That is, the unit structure 10B can improve the Q value compared to the unit structure 10A shown in Fig. 5. In other words, the unit structure 10B can reduce loss compared to the unit structure 10A shown in Fig. 5.

[0043] The electric field is stronger at both ends of each of the first electrodes 12Ba to 12Bd than at other portions. Therefore, by reducing the area where the second electrode 14B overlaps with the areas where the electric field is relatively strong in each of the first electrodes 12Ba to 12Bd when viewed from the Z-axis direction, the electromagnetic field confined within the unit structure 10B can be reduced. This improves the Q value of the unit structure 10B.

[0044] The arrangement of the first electrodes 12Ba to 12Bd is not limited to the example shown in Fig. 6. For example, when viewed from the Z-axis direction, the first electrodes 12Ba to 12Bd may be arranged such that only one end of at least one electrode overlaps with the second electrode 14B.

[0045] (Modification of First Embodiment) A configuration example of a unit structure according to a modification of the first embodiment will be described with reference to Fig. 7. Fig. 7 is a diagram showing a configuration example of a unit structure according to a modification of the first embodiment.

[0046] 7, the unit structure 10B may include two first electrodes 12B, a first electrode 12Ba and a first electrode 12Bb. That is, there is no limit to the number of first electrodes 12B included in the unit structure 10B.

[0047] 7, the first electrodes 12Ba and 12Bb may be arranged to have approximate rotational symmetry in the XY plane. In this case, it is sufficient that only one end of at least one of the first electrodes 12Ba and 12Bb overlaps with the second electrode 14B when viewed from the Z-axis direction.

[0048] In a modification of the first embodiment, for example, only one first electrode 12Ba may be disposed as the first electrode 12B. In this case, it is sufficient that only one end of the first electrode 12Ba overlaps with the second electrode 14 when viewed from the Z-axis direction.

[0049] Second Embodiment A configuration example of a unit structure according to the second embodiment will be described with reference to Fig. 8. Fig. 8 is a diagram showing a configuration example of a unit structure according to the second embodiment.

[0050] FIG. 8 shows the positional relationship between a first electrode 12C arranged on the upper surface of a unit structure 10C according to the second embodiment and a second electrode 14C arranged on the lower surface thereof.

[0051] 8, the unit structure 10C includes first electrodes 12C, which are first electrodes 12Ca, 12Cb, 12Cc, and 12Cd. The first electrodes 12Ca to 12Cd are rectangular. The first electrodes 12Ca to 12Cd are all the same size.

[0052] The second electrode 14C is formed in a rectangular shape. The second electrode 14C has an opening 80. The opening 80 has a polygonal shape obtained by obliquely cutting off each vertex of a square, but is not limited to this. The opening 80 may have any shape that is roughly rotationally symmetric in the XY plane, for example.

[0053] The first electrode 12Ca has an end 70a, an end 70b, an end 70c, and an end 70d. The end 70a to the end 70d are regions around each vertex of the first electrode 12Ca. For example, the end 70a to the end 70d are regions that are equal to or less than ¼ of the area of ​​the first electrode 12Ca including each vertex. When viewed from the Z-axis direction, the end 70a overlaps with the second electrode 14C. When viewed from the Z-axis direction, the end 70b, the end 70c, and the end 70d do not overlap with the second electrode 14C. In other words, when viewed from the Z-axis direction, only one end of the end 70a to the end 70d overlaps with the second electrode 14C.

[0054] The first electrode 12Cb has end portions 72a, 72b, 72c, and 72d. The end portions 72a to 72d are regions around the vertices of the first electrode 12Cb. For example, the end portions 72a to 72d are regions that are equal to or smaller than ¼ of the area of ​​the first electrode 12Cb, including the vertices. When viewed from the Z-axis direction, the end portion 72b overlaps the second electrode 14C. The degree of overlap between the end portion 72b and the second electrode 14C is the same as the degree of overlap between the end portion 70a of the first electrode 12Ca and the second electrode 14C. When viewed from the Z-axis direction, the end portions 72a, 72c, and 72d do not overlap the second electrode 14C. In other words, when viewed from the Z-axis direction, only one end portion from the end portions 72a to 72d overlaps the second electrode 14C.

[0055] The first electrode 12Cc has end portions 74a, 74b, 74c, and 74d. The end portions 74a to 74d are regions around each vertex of the first electrode 12Cc. For example, the end portions 74a to 74d are regions that are equal to or smaller than ¼ of the area of ​​the first electrode 12Cc, including each vertex. When viewed from the Z-axis direction, the end portion 74c overlaps the second electrode 14C. The degree of overlap between the end portion 74c and the second electrode 14C is the same as the degree of overlap between the end portion 70a of the first electrode 12Ca and the second electrode 14C. When viewed from the Z-axis direction, the end portions 74a, 74b, and 74d do not overlap the second electrode 14C. In other words, when viewed from the Z-axis direction, only one end portion from the end portions 74a to 74d overlaps the second electrode 14C.

[0056] The first electrode 12Cd has an end 76a, an end 76b, an end 76c, and an end 76d. The end 76a to the end 76d are regions around each vertex of the first electrode 12Cd. For example, the end 76a to the end 76d are regions that are equal to or smaller than ¼ of the area of ​​the first electrode 12Cd, including each vertex. When viewed from the Z-axis direction, the end 76d overlaps with the second electrode 14C. The degree of overlap between the end 76d and the second electrode 14C is the same as the degree of overlap between the end 70a of the first electrode 12Ca and the second electrode 14C. When viewed from the Z-axis direction, the end 70a, the end 70b, and the end 70c do not overlap with the second electrode 14C. In other words, when viewed from the Z-axis direction, only one end from the end 76a to the end 76d overlaps with the second electrode 14C.

[0057] That is, when viewed from the Z-axis direction, the first electrodes 12Ca to 12Cd are each arranged such that only one of their four ends overlaps the second electrode 14C. Because the degree of overlap between each end and the second electrode 14C is the same, the first electrodes 12Ca to 12Cd and the second electrode 14C are arranged to have approximate rotational symmetry in the XY plane.

[0058] The first electrodes 12Ca to 12Cd are λ / 2 resonators. Therefore, a strong electric field is distributed at each vertex of the first electrodes 12Ca to 12Cd. Therefore, by reducing the area where the first electrodes 12Ca to 12Cd overlap with the second electrode 14C, where the electric field is strongly distributed, as viewed from the Z-axis direction, the electromagnetic field confined within the unit structure 10C can be reduced. This improves the Q value of the unit structure 10C.

[0059] The arrangement of the first electrodes 12Ca to 12Cd is not limited to the example shown in Fig. 8. For example, the first electrodes 12Ca to 12Cd may be arranged such that at least one of their ends overlaps with the second electrode 14C when viewed from the Z-axis direction.

[0060] The present disclosure may also be configured as follows: (1) A unit structure comprising: a first electrode constituting a resonator and disposed on a first surface; and a second electrode disposed on a second surface spaced apart from the first surface in a first direction, wherein, when viewed in a plan view from a direction perpendicular to the first and second surfaces, the second electrode has an opening; the first electrode is composed of one or more electrodes; and, when viewed in a plan view from a direction perpendicular to the first and second surfaces, at least one of the electrodes constituting the first electrode has one end overlapping the second electrode and the other end not overlapping the second electrode. (2) The unit structure according to (1), wherein, when viewed in a plan view from a direction perpendicular to the first and second surfaces, the multiple electrodes constituting the first electrode are arranged in a rotational symmetry. (3) The unit structure according to (1) or (2), wherein a liquid crystal layer is disposed between the first electrode and the electrode. (4) A radio wave control board including a plurality of unit structures according to any one of (1) to (3).

[0061] REFERENCE SIGNS LIST 1 Radio wave control plate 10 Unit structure 12, 12A, 12Ba, 12Bb, 12Bc, 12Bd, 12Ca, 12Cb, 12Cc, 12Cd First electrode 14, 14A, 14B, 14C Second electrode 16 Liquid crystal layer 18 Liquid crystal molecules 20, 22 Glass substrate 30, 32, 34, 36, 60, 80 Opening 40, 42 Straight line portion

Claims

1. A unit structure constituting a resonator, comprising: a first electrode arranged on a first surface; and a second electrode arranged on a second surface separated from the first surface in a first direction, wherein, when viewed in a plane from a direction perpendicular to the first and second surfaces, the second electrode has an opening, and the first electrode is composed of one or more electrodes, and at least one of the electrodes constituting the first electrode has one end overlapping the second electrode and the other end not overlapping the second electrode when viewed in a plane from a direction perpendicular to the first and second surfaces.

2. The unit structure according to claim 1, wherein, when viewed in a plane from a direction perpendicular to the first surface and the second surface, the multiple electrodes constituting the first electrode are arranged in rotational symmetry.

3. The unit structure according to claim 1 or 2, wherein a liquid crystal layer is disposed between the first electrode and the electrode.

4. A radio wave control board comprising a plurality of unit structures according to claim 1.

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