reflector

Abstract

To provide a reflector that can reduce manufacturing costs. [Solution] A reflector 1 that reflects electromagnetic waves of a specific frequency band in a direction different from the specular reflection direction, having an uneven structure in which a plurality of unit structures 10 having a thickness distribution in which the thickness increases in a predetermined direction are arranged, the unit structure having a plurality of cell regions 11a to 11f of different thicknesses, and having at least a first unit structure having two or more cell regions of different thicknesses, having a conductive layer 3 on the surface facing the uneven structure, and adjacent cell regions being electrically connected to each other.

Description

[Technical Field]

[0001] This disclosure relates to a reflector that reflects electromagnetic waves of a specific frequency band in a direction different from the specular reflection direction. [Background technology]

[0002] In mobile communication systems, reflect array technology is being considered to improve the propagation environment and coverage area (for example, Patent Documents 1-2, Non-Patent Document 1). In particular, at high frequencies such as those used in fifth-generation communication systems (5G), where directivity is strong, eliminating coverage holes (areas where radio waves do not reach) is a crucial issue.

[0003] A reflect array is desired to be able to reflect electromagnetic waves of a specific frequency incident from a base station in a predetermined direction in a desired direction. Such a reflect array may consist of multiple reflective elements arranged in a specific configuration. By changing the size and shape of the reflective elements, the resonant frequency of each reflective element is changed, thereby controlling the reflection phase of the electromagnetic waves and, consequently, controlling the incident and reflected directions of the electromagnetic waves.

[0004] In the above-mentioned reflect array, the pattern of the reflecting element is known to be formed, for example, by etching a metal layer using photolithography technology.

[0005] To obtain a reflector array with reflective properties that have the desired reflection angle, it is necessary to precisely control the reflection phase within the reflector array surface. However, since photomasks are used for photolithography of metal layers, manufacturing costs tend to increase with miniaturization and increased precision. Furthermore, because there are limitations to the processing accuracy of photolithography of metal layers, it is difficult to precisely control the reflection phase at high frequencies where wavelengths are short and processing accuracy is required.

[0006] Furthermore, in the above-mentioned reflect array, the reflection angle can be increased by narrowing the pitch of the reflecting elements, for example. However, in a planar arrangement of reflecting elements, there are limits to how narrow the pitch of the reflecting elements can be, making it difficult to increase the reflection angle. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 5371633 [Patent Document 2] Patent No. 5162677 [Patent Document 3] International Publication No. 2016 / 002832 [Non-patent literature]

[0008] [Non-Patent Document 1] Mayumi Yoshino et al., "Improvement of Received Power in an L-Shaped Corridor Outside Line of Sight Environment Using Meta-Surface Reflectors," IEICE Technical Report A·P2020-5 (2020-04) [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] This disclosure is made in view of the above circumstances and primarily aims to provide a reflector that can reduce manufacturing costs. [Means for solving the problem]

[0010] One embodiment of the present disclosure provides a reflector that reflects electromagnetic waves of a specific frequency band in a direction different from the specular reflection direction, and has an uneven structure in which a plurality of unit structures having a thickness distribution in which the thickness increases in a predetermined direction are arranged, the unit structure having a plurality of cell regions of different thicknesses, and the unit structure having at least a first unit structure having two or more of the cell regions of different thicknesses, and having a conductive layer on the surface facing the uneven structure, and adjacent cell regions being electrically connected to each other.

[0011] In the present disclosure, it is preferable that the conductive layer is also disposed on the side surfaces of each of the cell regions.

[0012] Further, in the present disclosure, when the wavelength of the electromagnetic wave is λ, m is an integer, and a is a real number of 0 or more, in the unit structure, the thickness of the maximum thickness cell region having the maximum thickness is preferably represented by (λ / 2)×m + a.

[0013] Further, in the present disclosure, when the wavelength of the electromagnetic wave is λ and n is an integer, in the unit structure, the difference in thickness between adjacent cell regions is preferably represented by (λ / 2) / n.

[0014] Further, in the present disclosure, in the unit structure, it is preferable that the difference in thickness between adjacent cell regions is equal.

[0015] Further, in the present disclosure, in the unit structure, the difference between the thickness of the minimum thickness cell region having the minimum thickness and the thickness of the maximum thickness cell region having the maximum thickness is preferably less than 1 / 2 of the wavelength λ of the electromagnetic wave.

[0016] Further, the reflector of the present disclosure preferably has a periodic structure in which the unit structure is repeatedly arranged.

[0017] Further, the reflector of the present disclosure may have a second unit structure different from the first unit structure as the unit structure.

Advantages of the Invention

[0018] The reflector of the present disclosure has the effect of being able to reduce the manufacturing cost.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic plan view and a cross-sectional view illustrating the reflector of the present disclosure, and a schematic diagram for explaining the relative reflection phase of electromagnetic waves in each cell region of the unit structure in the reflector of the present disclosure. [Figure 2] This is a schematic diagram illustrating the reflective properties of the reflector in the present disclosure. [Figure 3] This is a schematic perspective view illustrating the unit structure of the reflector in this disclosure. [Figure 4] This is a schematic plan view illustrating the unit structure of the reflector in this disclosure. [Figure 5] This is a schematic cross-sectional view illustrating a reflector in this disclosure. [Figure 6] This is a schematic cross-sectional view illustrating a reflector in this disclosure. [Figure 7] This is a schematic cross-sectional view illustrating a reflector in this disclosure. [Figure 8] This is a schematic diagram illustrating the reflective properties of the reflector in the present disclosure. [Figure 9] This is a schematic plan view illustrating a reflector in the present disclosure. [Figure 10] This document provides a schematic cross-sectional view illustrating the reflector of the present disclosure, as well as a schematic diagram illustrating the relative reflection phase of electromagnetic waves in each cell region of the unit structure in the reflector of the present disclosure. [Figure 11] This is a schematic diagram illustrating the configuration of a unit structure in the reflector of this disclosure. [Figure 12] This is a schematic perspective view showing the simulation model of Example 1 and a graph showing the simulation results. [Modes for carrying out the invention]

[0020] Embodiments of this disclosure will be described below with reference to drawings and other figures. However, this disclosure can be implemented in many different ways and should not be interpreted as being limited to the embodiments described below. In addition, in order to make the explanation clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual form, but these are merely examples and should not limit the interpretation of this disclosure. Furthermore, in this specification and each figure, elements similar to those described above with respect to previously shown figures will be denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

[0021] In this specification, when describing a configuration in which one component is placed on top of another component, unless otherwise specified, the terms "above" or "below" include both cases: when the other component is placed directly above or below the component so as to be in contact with it, and when the other component is placed above or below the component via yet another component. When describing a configuration in which one component is placed above another component, unless otherwise specified, the terms "above" or "below" include, unless otherwise specified, all cases: when the other component is placed directly above or below the component so as to be in contact with it, when the other component is placed above or below the component via yet another component, and when the other component is placed above or below the component via space. Furthermore, in this specification, when describing a configuration in which one component is placed on the surface of another component, unless otherwise specified, the terms "on the surface" include both cases: when the other component is placed directly above or below the component so as to be in contact with it, and when the other component is placed above or below the component via yet another component.

[0022] The reflector described herein will be explained in detail below.

[0023] The reflector of this disclosure is a reflector that reflects electromagnetic waves of a specific frequency band in a direction different from the specular reflection direction, and has an uneven structure in which a plurality of unit structures having a thickness distribution in which the thickness increases in a predetermined direction are arranged, the unit structure has a plurality of cell regions of different thicknesses, and the unit structure has at least a first unit structure having two or more of the cell regions of different thicknesses, and has a conductive layer on the surface facing the uneven structure, and adjacent cell regions are electrically connected to each other.

[0024] The reflector of this disclosure will be described with reference to the drawings. Figures 1(a) and (b) are schematic plan view and cross-sectional view showing an example of the reflector of this disclosure, and Figure 1(b) is a cross-sectional view taken along line AA of Figure 1(a). As shown in Figures 1(a) and (b), the reflector 1 is a reflector that reflects electromagnetic waves of a specific frequency band and has an uneven structure in which a plurality of unit structures 10 having a thickness distribution in which the thickness t1 to t6 increases in a predetermined direction D1 are arranged. The unit structure 10 also has a plurality of cell regions 11a to 11f with different thicknesses t1 to t6. For example, in Figure 1(b), the unit structure 10 has a step shape in which the thickness t1 to t6 increases in a stepwise manner in a predetermined direction D1, and the number of steps in the step shape is 6, so the unit structure 10 has 6 cell regions 11a to 11f. The reflector 1 also has a conductive layer 3 on the surface facing the uneven structure, and the conductive layer 3 can also be arranged on the sides of the cell regions 11a to 11f, and adjacent cell regions are electrically connected to each other.

[0025] In Figure 1(b), the reflector 1 has a base layer 4 with irregularities on one surface and a conductive layer 3 arranged on the irregular side of the base layer 4, but the configuration of the reflector is not limited to this.

[0026] In the reflector 1, since the thickness t1 to t6 differs in each cell region 11a to 11f of the unit structure 10, the round-trip optical path lengths differ when electromagnetic waves are reflected from the surface of the reflector 1 on the uneven structure side and emitted towards the incident side of the electromagnetic waves. These differences in the round-trip optical path lengths of the electromagnetic waves create a difference in the reflection phase.

[0027] Here, the term "optical path length" is used in this specification because the wavelength of the frequency band covered in this disclosure is closer to that of light and has higher directivity compared to conventional LTE frequency bands, making it easier to explain by describing its behavior as similar to that of light. In reality, it refers to the effective distance when electromagnetic waves pass through air.

[0028] Furthermore, in the reflector 1, in the unit structure 10, in the cross-section of the unit structure 10 in the thickness direction in a predetermined direction D1, the ends E1 to E6 of each cell region 11a to 11f are on the same straight line.

[0029] For example, if the lengths of each cell region 11a to 11f in a predetermined direction D1 are the same, and the difference in thickness between adjacent cell regions is the same, then in the unit structure 10, the ends E1 to E6 of each cell region 11a to 11f will be aligned on the same straight line (the dashed line in the figure) in the cross-section of the unit structure 10 in the thickness direction of the predetermined direction D1.

[0030] Specifically, in a unit structure 10 having six cell regions 11a to 11f, when the wavelength of the electromagnetic wave is λ, the difference in thickness between adjacent cell regions can be designed to be λ / 2 divided by 6, i.e., λ / 12. In this case, if the wavelength of the electromagnetic wave is λ, m is an integer, a is a real number greater than or equal to 0, and the thickness t6 of the maximum thickness cell region 11f having a maximum thickness t6 is (λ / 2) × m + a, then the thicknesses t1 to t6 of each cell region 11a to 11f can be designed as follows.

[0031] t1:{(λ / 2)×m}-{(λ / 12)×5}+a t2:{(λ / 2)×m}-{(λ / 12)×4}+a t3:{(λ / 2)×m}-{(λ / 12)×3}+a t4:{(λ / 2)×m}-{(λ / 12)×2}+a t5:{(λ / 2)×m}-{(λ / 12)×1}+a t6:{(λ / 2)×m}+a

[0032] For example, when m=1 and a=0, the thicknesses t1 to t6 of each cell region 11a to 11f are as follows.

[0033] t1: 1λ / 12 t2:2λ / 12 t3:3λ / 12 t4:4λ / 12 t5:5λ / 12 t6:6λ / 12

[0034] In this case, the delay in the reflection phase of electromagnetic waves is greatest in the cell regions 11a, 11b, 11c, 11d, 11e, and 11f, with the reflection phase of electromagnetic waves being smallest in cell region 11f. When the reflection phase in cell region 11f, which has the smallest reflection phase, is used as the reference, the relative reflection phases in each cell region 11a to 11f are as shown in Figure 1(c), for example. In Figure 1(c), the relative reflection phases of electromagnetic waves in each cell region 11a to 11f of the unit structure 10 are -300 degrees, -240 degrees, -180 degrees, -120 degrees, -60 degrees, and 0 degrees, respectively, and the absolute value of the difference in the relative reflection phases of electromagnetic waves between adjacent cell regions is 60 degrees.

[0035] As described above, in each cell region 11a to 11f of the unit structure 10, the change in thickness t1 to t6 changes the round-trip optical path length of the electromagnetic wave and changes the reflection phase of the electromagnetic wave. As illustrated in Figure 2, the incident electromagnetic wave W1 can be reflected in a direction different from the specular reflection direction. In this case, the incident angle θ1 of the incident electromagnetic wave W1 and the reflection angle θ2 of the reflected electromagnetic wave W2 are different.

[0036] Therefore, in the reflector of this disclosure, the reflection phase of the electromagnetic wave can be controlled by changing the thickness of each cell region of the unit structure, thereby changing the round-trip optical path length of the electromagnetic wave for each cell region. This makes it possible to control the reflection direction of the electromagnetic wave with respect to a predetermined incident direction to any direction.

[0037] Herein, in this specification, "reflection phase" refers to the amount of change in the phase of a reflected wave with respect to the phase of an incident wave incident on a surface.

[0038] Furthermore, in this specification, "relative reflection phase" refers to the delay in the reflection phase of a given cell region relative to the reflection phase of the cell region with the smallest delay in the reflection phase within a single unit structure, expressed with a negative sign. For example, if the reflection phase of the cell region with the smallest delay in the reflection phase within a single unit structure is -10 degrees, then the relative reflection phase of a cell region with a reflection phase of -40 degrees will be -30 degrees.

[0039] Unless otherwise specified, the reflection phase is within the range of greater than -360 degrees and less than 360 degrees, with -360 degrees and +360 degrees returning to 0 degrees. Also, unless otherwise specified, the relative reflection phase is within the range of greater than -360 degrees and 0 degrees or less, with -360 degrees returning to 0 degrees.

[0040] Furthermore, in this specification, "cell region" refers to a region in a unit structure that has the same thickness, that is, a region in which the reflection phase of electromagnetic waves is the same.

[0041] In conventional reflect arrays where multiple reflective elements are arranged, the reflection phase can be delayed or advanced by adjusting, for example, the dimensions and shape of the reflective elements. In the reflector of this disclosure, the reflection phase can be advanced by increasing the thickness of each cell region of the unit structure, using the reflection phase in the cell region with the smallest thickness as a reference, thereby controlling the direction of the reflected wave. Furthermore, in the reflector of this disclosure, the direction of the reflected wave can also be controlled by utilizing the fact that the reflection phase is delayed as the thickness of each cell region of the unit structure decreases, using the reflection phase in the cell region with the largest thickness as a reference.

[0042] In this disclosure, since it is not necessary to arrange multiple reflective elements as in the conventional method, manufacturing costs can be reduced. Furthermore, the uneven structure in this disclosure can be formed by various methods such as cutting, laser processing, molding using a mold, 3D printing, and joining of small parts. Therefore, it does not require a photomask, as is the case with photolithography of the metal layer in conventional reflect arrays. Thus, when designing the thickness of each cell region of the unit structure to achieve the desired incidence and reflection angles and manufacturing a reflector, the desired reflector can be manufactured relatively inexpensively and in a short time. In addition, since the machinable range for the thickness and size of the unit structure, which affect the control of the reflection characteristics, is relatively wide, it is possible to increase the incidence and reflection angles of electromagnetic waves, for example, and thus widen the control range of the reflection characteristics. Furthermore, since the margin of dimensional processing accuracy for achieving the desired reflection phase is relatively wide for the thickness of the unit structure and the pitch of the cell regions of the unit structure, it is easier to obtain the desired reflection characteristics and the effects of dimensional variations can be reduced. Therefore, it is easy to customize the reflection characteristics of the reflector.

[0043] The following describes the various components of the reflector in this disclosure.

[0044] 1.Uneven structure The reflector of this disclosure has an uneven structure in which a plurality of unit structures having a thickness distribution in which the thickness increases in a predetermined direction are arranged.

[0045] The unit structure has multiple cell regions of different thicknesses.

[0046] Furthermore, if both the incident and reflected waves can be considered as plane waves, then in each unit structure, the edges of each cell region will lie on the same straight line in the cross-section of the unit structure in the thickness direction in a given direction.

[0047] On the other hand, for example, when the incident wave is a spherical wave or when controlling the reflected beam profile with a reflector, the cross-section in the thickness direction of the unit structure in a given direction will have a periodic stepped shape with a certain thickness as the upper limit, specifically a stepped shape in which the thickness is periodically increased or decreased with a certain thickness as the upper limit.

[0048] The end of a cell region refers to the end of a cell region located on the side of other cell regions that are thinner than the cell region in a direction in which the thickness increases, within the cross-section of a single unit structure. For example, in Figure 1(b), the end of cell region 11b is the end of cell region 11a located on the side of other cell regions 11a and 11c adjacent to cell region 11b in a predetermined direction D1, with respect to cell region 11b, and is indicated by E2. Similarly, the ends of each cell region 11c to 11f are indicated by E3 to E6, respectively. If, within the cross-section of a single unit structure, there are no other cell regions thinner than the cell region in a direction in which the thickness increases, then the end of a cell region refers to the end located on the opposite side from the other cell regions that are thicker than the cell region. For example, in Figure 1(b), the end of cell region 11a is the end located on the opposite side from cell region 11b, which is thicker than cell region 11a, and is indicated by E1.

[0049] Furthermore, in the cross-section of the unit structure in the thickness direction in a predetermined direction, the difference in the thickness direction at the ends of each cell region is preferably within ±λ / 2, more preferably within ±λ / 4, and even more preferably within ±λ / 6.

[0050] A unit structure has a thickness distribution in which the thickness increases in a predetermined direction. For example, a unit structure may have a thickness distribution in which the thickness increases in only one direction, or it may have a thickness distribution in which the thickness increases in two directions, a first direction and a second direction perpendicular to the first direction. For example, Figure 3(a) is an example in which unit structure 10 has a thickness distribution in which the thickness increases only in the first direction D1, and Figures 3(c), (e), and 4(a) are examples in which unit structure 10 has a thickness distribution in which the thickness increases in the first direction D1 and the second direction D2.

[0051] As described above, in each unit structure, if the ends of each cell region are collinear in a cross-section in the thickness direction of the unit structure in a predetermined direction, and the unit structure has a thickness distribution in which the thickness increases in only one direction, then the ends of each cell region will be collinear in the cross-section in the thickness direction of the unit structure in that one direction. Furthermore, in the above case, if the unit structure has a thickness distribution in which the thickness increases in two directions perpendicular to each other, then the ends of each cell region will be collinear in the cross-section in the thickness direction of the unit structure in those two directions, respectively.

[0052] On the other hand, as described above, if the cross-section in the thickness direction of a unit structure in a given direction has a periodic step shape with a certain thickness as the upper limit, specifically a step shape in which the thickness increases and decreases periodically with a certain thickness as the upper limit, and the unit structure has a thickness distribution in which the thickness increases in only one direction, then the cross-section in the thickness direction of the unit structure in that one direction will have a periodic step shape with a certain thickness as the upper limit. Furthermore, in the above case, if the unit structure has a thickness distribution in which the thickness increases in two directions perpendicular to each other, then the cross-sections in the thickness direction of the unit structure in those two directions will each have a periodic step shape with a certain thickness as the upper limit.

[0053] In a single unit structure, the thickness of the maximum thickness cell region having the maximum thickness is preferably expressed as (λ / 2) × m + a, where λ is the wavelength of the electromagnetic wave, m is an integer, and a is a real number of 0 or more. a is a real number of 0 or more, and is also the thickness of the base of the reflector, and is set appropriately considering the overall strength, ease of formation, etc. a can be, for example, 0 mm or more and 3 mm or less. Note that the base thickness a is a different concept from the thickness of the minimum thickness cell region having the minimum thickness. Also, m is an integer, for example, it can be an integer of 1 or more, and preferably an integer of 1 or more and 3 or less. If m becomes large, the overall thickness of the reflector will increase, which may make it difficult to install the reflector. For example, in Figure 1(b), it is preferable that the thickness t6 of the maximum thickness cell region 11f having the maximum thickness t6 is (λ / 2) × m + a.

[0054] In a single unit structure, the difference in thickness between adjacent cell regions is preferably expressed as (λ / 2) / n, where λ is the wavelength of the electromagnetic wave and n is an integer. n is an integer, and for example, if the cross-sectional shape of the unit structure is a staircase shape and the difference in thickness between adjacent cell regions is equal, it corresponds to the number of steps in the staircase shape, i.e., the number of cell regions.

[0055] For example, Figure 1(b) shows an example where the cross-sectional shape of the unit structure 10 is staircase-shaped, the number of steps in the staircase shape is 6, and the difference in thickness between adjacent cell regions is equal. In this case, it is preferable that the difference in thickness between adjacent cell regions is (λ / 2) / 6 = λ / 12.

[0056] Furthermore, for example, Figure 5 shows an example where the cross-sectional shape of the unit structure 10 is staircase-shaped, the number of steps in the staircase shape is 4, and the difference in thickness between adjacent cell regions is different. In this case, it is preferable that the difference in thickness between adjacent cell regions is (λ / 2) / n. Specifically, the thicknesses t1 to t4 of each cell region 11a to 11d of the unit structure 10 can be set to 1λ / 12, 3λ / 12, 4λ / 12, and 6λ / 12, respectively, and the difference in thickness between adjacent cell regions 11a and 11b can be set to 2λ / 12, the difference in thickness between adjacent cell regions 11b and 11c can be set to λ / 12, and the difference in thickness between adjacent cell regions 11c and 11d can be set to 2λ / 12. In this case, the difference in thickness between adjacent cell regions is 2λ / 12 = λ / 6 = (λ / 2) / 3 and λ / 12 = (λ / 2) / 6, respectively.

[0057] Furthermore, within a single unit structure, the difference in thickness between adjacent cell regions may be equal or different, but it is preferable that they be equal. For example, Figure 1(b) shows an example where the difference in thickness between adjacent cell regions is equal, and Figure 5 shows an example where the difference in thickness between adjacent cell regions is different.

[0058] Furthermore, in a single unit structure, it is preferable that the difference between the thickness of the minimum thickness cell region having the minimum thickness and the thickness of the maximum thickness cell region having the maximum thickness is less than half the wavelength λ of the electromagnetic wave. Also, in a single unit structure, it is preferable that the difference between the thickness of the minimum thickness cell region having the minimum thickness and the thickness of the maximum thickness cell region having the maximum thickness is greater than 1 / 6 the wavelength λ of the electromagnetic wave. For example, as shown in Figure 1(b), when the unit structure 10 has 6 cell regions, in a single unit structure 10, it is preferable that the difference between the thickness t1 of the minimum thickness cell region 11a having the minimum thickness t1 and the thickness t of the maximum thickness cell region 11f having the maximum thickness t6 is less than λ / 2. Specifically, in a single unit structure 10, the thickness t1 of the minimum thickness cell region 11a having the minimum thickness t1 is set to λ / 12, and the thickness t6 of the maximum thickness cell region 11f having the maximum thickness t6 is set to 6λ / 12, so that the difference between the thickness t1 of the minimum thickness cell region 11a having the minimum thickness t1 and the thickness t6 of the maximum thickness cell region 11f having the maximum thickness t6 is set to 5λ / 12.

[0059] The size of the unit structure, specifically the length of the unit structure in a predetermined direction where the thickness increases, is set appropriately according to the desired reflection characteristics. The length of the unit structure in the predetermined direction where the thickness increases causes a shift of one wavelength (phase difference: 360 degrees), thus allowing for adjustment of the reflection angle. For example, shortening the length of the unit structure in the predetermined direction where the thickness increases increases the difference between the reflection angle and the specular reflection angle, while lengthening the length of the unit structure in the predetermined direction where the thickness increases decreases the difference between the reflection angle and the specular reflection angle.

[0060] In a unit structure, the length of the unit structure in a predetermined direction in which the thickness increases refers to the length of the unit structure in a predetermined direction when the unit structure has a thickness distribution in which the thickness increases in that predetermined direction. For example, in Figure 5, the thickness of the unit structure 10 increases in a predetermined direction D1, and the length of the unit structure 10 in this predetermined direction D1 is L.

[0061] Furthermore, the cross-sectional shape of the unit structure may be, for example, a stepped shape in which the thickness gradually increases in a predetermined direction, or a tapered shape in which the thickness gradually increases in a predetermined direction. For example, Figures 1(b) and 5 show an example in which the unit structure 10 has a stepped shape, and Figure 6 shows an example in which the unit structure 10 has a tapered shape.

[0062] Although a unit structure has multiple cell regions of different thicknesses, if the cross-sectional shape of the unit structure is tapered, it can be considered as having an infinitely large number of cell regions. Even in this case, the thickness distribution of the unit structure is designed so that the thickness of each cell region is set as described above.

[0063] Furthermore, since the reflector consists of multiple unit structures with varying thicknesses, the planar pattern shape of the unit structures can be any shape that allows for seamless arrangement, such as a rectangular or hexagonal shape. For example, Figures 3(a) to 3(f) and 4(a) show an example where the planar pattern shape of unit structure 10 is rectangular.

[0064] In the unit structure, the thickness of each cell region is designed to match the settings described above. The thickness of each cell region is set appropriately according to the wavelength of the electromagnetic wave and the desired reflection characteristics. For example, if the frequency of the electromagnetic wave is 30 GHz, i.e., the wavelength of the electromagnetic wave is 10 mm, then the thickness of each cell region is preferably between 0.1 mm and 5.1 mm.

[0065] In the unit structure, the pitch and width of the cell area are set as appropriate.

[0066] Furthermore, regarding the size of the cell region, for example, if the pattern shape of the cell region in plan view is striped, then when the wavelength of the electromagnetic wave is λ and p is an integer, the width of the cell region can be λ / p or greater. That is, the unit structure can be a configuration in which cell regions with a width of λ / p or less are tiled together. p can be between approximately 2 and 10. On the other hand, in the above case, the length of the cell region only needs to be less than or equal to the length of one side of the reflector. Also, in a single unit structure, the number of tiled cell regions varies depending on the direction and angle of the incident and reflected waves, but is 2 or more.

[0067] Furthermore, it is preferable that the pitch of the cell regions be equal within a single unit structure.

[0068] The cell region pitch refers to the distance from the center of one cell region to the center of an adjacent cell region.

[0069] Furthermore, in a single unit structure, the widths of the cell regions in a predetermined direction where the thickness increases may be equal or different, but it is preferable that they be equal.

[0070] In a unit structure, examples of pattern shapes in a plan view of a cell region include stripes, one shape obtained by dividing a concentric square into four equal parts by lines parallel to the sides and perpendicular to each other, a microarray, a concentric quarter circle shape obtained by dividing a concentric circle into four equal parts by diameters perpendicular to each other, and a curved staircase shape. For example, Figure 3(b) is an example of a stripe, Figure 3(d) is an example of one shape obtained by dividing a concentric square into four equal parts by lines parallel to the sides and perpendicular to each other, Figures 3(f) and 4(a) are examples of a microarray, Figure 4(b) is an example of a concentric quarter circle shape, and Figure 4(c) is an example of a curved staircase shape. Note that Figure 3(b) is a top view of Figure 3(a), Figure 3(d) is a top view of Figure 3(c), and Figure 3(f) is a top view of Figure 3(e). Furthermore, when these exemplified unit structures are arranged without gaps, there are no particular restrictions on the direction of arrangement. For example, rectangular unit structures can be arranged across the entire surface after being rotated 30 degrees clockwise in a plan view. The unit structures should be arranged at an appropriate angle and in an appropriate direction according to the required reflective properties.

[0071] A unit structure has multiple cell regions. In a single unit structure, the number of cell regions is, for example, 3 or more, and preferably 6 or more. The more cell regions there are in a single unit structure, the smaller the difference in thickness between adjacent cell regions becomes, the smaller the difference in reflection phase of electromagnetic waves between adjacent cell regions becomes, and the smoother the wavefront of the reflected wave becomes. Furthermore, a larger number of cell regions in a single unit structure is preferable, and there is no particular upper limit. If the cross-sectional shape of the unit structure is a step shape, the number of cell regions corresponds to the number of steps in the step shape. Also, if the cross-sectional shape of the unit structure is a tapered shape, as described above, the tapered shape can be considered as having an infinitely large number of cell regions.

[0072] The reflector has at least one first unit structure, which has two or more cell regions of different thicknesses, as a unit structure.

[0073] Furthermore, the reflector may have only a first unit structure as its unit structure, or it may have a second unit structure different from the first unit structure. In other words, the reflector may have only identical unit structures as its unit structure, or it may have unit structures that are different from each other. When the reflector is composed of multiple unit structures that are different from each other, it can affect the overall reflection characteristics of the reflector. Specifically, examples include the adjustment of polarization characteristics and the effect on the beam profile (high directivity, diffuse, multi-beam, etc.).

[0074] In the first and second unit structures, the reflective properties can be made different, for example, the length of the unit structure in the direction of increasing thickness, the thickness distribution, the number, width, and pitch of the cell regions, the planar pattern shape of the unit structure, and the planar pattern shape of the cell regions can be made different.

[0075] Furthermore, if the reflectors have different unit structures as unit structures, the number of types of unit structures is not particularly limited.

[0076] In a reflector, the thickness distribution is appropriately selected and multiple unit structures are arranged so that the normal vector of the same-phase plane of the reflected wave for an incident wave incident at a predetermined incident angle becomes the desired reflection direction. For example, when an incident wave is reflected as a so-called plane wave, which is reflected in a single direction, it is preferable that the reflector consists of multiple identical unit structures, the lengths of the unit structures are the same in the predetermined direction in which the thickness increases, and the pattern shape of the cell region in plan view is striped. For example, in Figures 1(a) and (b), the reflector 1 has multiple identical unit structures, the lengths of the unit structures 10a and 10b are the same in the predetermined direction D1, and the pattern shape of the cell regions 11a to 11f in plan view is striped. In this case, as illustrated in Figure 2, an incident wave W1 incident at a predetermined incident angle θ1 can be reflected at a single reflection angle θ2, and the reflected wave W2 can be a plane wave without spreading. Furthermore, while Figure 1(a) shows an arrangement where the longitudinal direction of the cell area stripes is parallel to the short direction of the reflector, it is not limited to this arrangement. In actual reflectors, the longitudinal and short directions of the cell area stripes can be arbitrarily set according to the design of the reflective characteristics.

[0077] Furthermore, for example, when electromagnetic waves are diffused, that is, reflected as cylindrical waves, it is preferable that the reflector has multiple different unit structures arranged together, and that the lengths of the unit structures differ in a predetermined direction in which the thickness increases, and that the pattern shape in a plan view of the cell region is striped. For example, in Figure 7, the reflector 1 has three different types of unit structures 10a and 10b, 10c and 10d, and the lengths L1, L2 and L3 of the unit structures L1, L2 and L3 in a predetermined direction D1 differ between these unit structures 10a and 10b and 10c and 10d. Furthermore, the thicknesses of cell regions 11a, 12a, and 13a are the same; similarly, the thicknesses of cell regions 11b, 12b, and 13b are the same; the thicknesses of cell regions 11c, 12c, and 13c are the same; the thicknesses of cell regions 11d, 12d, and 13d are the same; the thicknesses of cell regions 11e, 12e, and 13e are the same; the thicknesses of cell regions 11f, 12f, and 13f are the same; and the thicknesses of cell regions 11g, 12g, and 13g are the same. As a result, the slopes of the lines passing through the ends of each cell region 11a to 11g of unit structure 10a, the lines passing through the ends of each cell region 12a to 12g of unit structures 10b and 10c, and the lines passing through each cell region 13a to 13g of unit structure 10d are different from each other, and the reflection characteristics of the three types of unit structures 10a and 10b, and 10c and 10d are different from each other. Furthermore, although not shown in the figures, the planar pattern shape of cell regions 11a-11g, 12a-12g, and 13a-13g is striped. In this case, as illustrated in Figure 8, the incident wave W1 incident at a predetermined incident angle θ1 can be reflected at reflection angles θ2, θ2', and θ2'' according to the unit structure, resulting in a broadened reflection and a wider wavefront for the reflected wave W2.

[0078] Furthermore, if the reflector has different unit structures as its unit structure, multiple types of unit structures with different reflective properties may be used, multiple unit structures of each type may be arranged, and regions where multiple units of the same type are arranged may be arranged in a planar configuration. For example, in Figure 9, two types of unit structures 10a and 10b with different reflective properties are used, and the reflector 1 is formed by arranging in a planar configuration a first region 5a where multiple units of one type of unit structure 10a are arranged, and a second region 5b where multiple units of the other type of unit structure 10b are arranged. In such a configuration, it is possible to accommodate multiple coverage holes.

[0079] Furthermore, if the reflector has different unit structures as its unit structure, the thickness of each cell region of the N unit structures may be set such that, for example, the N unit structures are shifted by N wavelengths (phase difference: N × 360 degrees). Note that N is an integer of 2 or more.

[0080] For example, Figures 10(a) and 10(b) show an example in which the reflector 1 has two different types of unit structures 10a and 10b, and the thickness of the respective cell regions 11a to 11b and 12a to 12c of the two unit structures 10a and 10b is set so that they are shifted by two wavelengths (phase difference: 720 degrees).

[0081] For example, if the lengths in a predetermined direction D1 are the same for each cell region 11a-11b and 12a-12c, and the difference in thickness between adjacent cell regions is the same, then in the cross-section of the unit structures 10a and 10b in the thickness direction in the predetermined direction D1, the straight line passing through the ends E1-E2 of each cell region 11a-11b of the unit structure 10a and the straight line passing through the ends E3-E5 of each cell region 12a-12c of the unit structure 10b will have the same slope.

[0082] Specifically, in two unit structures 10a and 10b having a total of five cell regions 11a-11b and 12a-12c, when the wavelength of the electromagnetic wave is λ, the difference in thickness between adjacent cell regions can be designed to be λ divided by 5, i.e., λ / 5. In this case, if the wavelength of the electromagnetic wave is λ, a is a real number greater than or equal to 0, and the thickness t5 of the maximum thickness cell region 12c having a maximum thickness t5 is (λ / 2)+a, then the thicknesses t1-t4 of each cell region 11a-11b and 12a-12c can be designed as follows.

[0083] t1:λ-{(λ / 5)×4}+a t2:λ-{(λ / 5)×3}+a t3:(λ / 2)-{(λ / 5)×2}+a t4:(λ / 2)-{(λ / 5)×1}+a t5:(λ / 2)+a

[0084] For example, when a=0, the thicknesses t1~t4 of each cell region 11a~11b and 12a~12c are as follows.

[0085] t1:2λ / 10 t2:4λ / 10 t3:1λ / 10 t4:3λ / 10 t5:5λ / 10

[0086] In such cases, if the reflection phase in cell region 12c, which has the smallest reflection phase, is used as the reference, the relative reflection phases in each cell region 11a-11b and 12a-12c will be as shown in Figures 10(b) and (c), for example. Figure 10(b) is a graph showing the range of the relative reflection phase of electromagnetic waves as greater than -360 degrees and less than or equal to 0 degrees, while Figure 10(c) is a graph showing the range of the relative reflection phase of electromagnetic waves as greater than -720 degrees and less than or equal to 0 degrees, with points that are essentially in phase but shifted by 360 degrees being interpolated. In these unit structures 10a and 10b, the lengths of the unit structures in a given direction D1 are different from each other, and the number of cell regions 11a-11b and 12a-12c are different from each other.

[0087] In addition, when the incident wave and the reflected wave are plane waves, the reflector has a periodic structure in which unit structures are repeatedly arranged. The "periodic structure" refers to a structure in which unit structures are periodically and repeatedly arranged. In the unit structure of the periodic structure, in the unit structures with the same reflection characteristics, the length of the unit structure, the thickness distribution, the number of cell regions, the width, the pitch, the pattern shape of the unit structure in plan view, the pattern shape of the cell region in plan view, etc. in the direction in which the thickness increases can be made the same. Further, even when the reflector has a periodic structure, as described above, unit structures with different reflection characteristics can be combined. In that case, the reflection characteristics of the unit structures to be combined are appropriately designed according to the target reflection characteristics. Specifically, in the unit structures to be combined, the length of the unit structure, the thickness distribution, the number of cell regions, the width, the pitch, the pattern shape of the unit structure in plan view, the pattern shape of the cell region in plan view, etc. in the direction in which the thickness increases are appropriately set according to the target reflection characteristics.

[0088] Generally, in the design of reflection characteristics for reflecting a plane wave in a direction different from the normal reflection direction, for example, after decomposing the incident and reflection characteristics in the in-plane x-direction and in-plane y-direction of the reflector, converting them into the reflection phase distributions in the x-direction and y-direction, and incorporating them as the thickness distribution of the unit structure, the design can be achieved. For example, as shown in FIG. 11, a part of a reflector in which cell regions of the same size (i = 10, j = 10) capable of individually adjusting the reflection phase are arranged will be described as an example. At this time, it should be noted that the size of 10×10 of the cell region is not necessarily the size of the unit structure. The plane wave incident from the direction of the incident angle (θ in , φ in ) is reflected as a plane wave in the direction of the reflection angle (θ out , φ out ). The reflection phase δ i,j required for the cell region at the (i, j) position is given by the following equation.

[0089] δ i,j = 2π{p×i×(sinθ out ×cosφ out - sinθ in ×cosφ in ) + p × j × (sinθ) out ×sinφ out -sinθ in ×sinφ in )} / λ Here, in the above formula, δ i,j : Reflection phase of the cell region at position (i,j) relative to the phase center (0,0) λ: Wavelength of the reflected wave [m] p: Size of the cell area [m] θ in : θ slope of the incident wave φ in : Slope of the incident wave θ out : θ slope of the reflected wave φ out : φ slope of the reflected wave This indicates.

[0090] Note that t is the thickness of the cell region, t min If we let Δt be the thickness of the minimum thickness cell region, Δt be the thickness increase from the minimum thickness, and λ be the wavelength of the electromagnetic wave, and take the reflection phase at Δt=0 as the reference (0), then the reflection phase δ can be expressed approximately as shown in the following equation. δ[rad] = 4 × π × (Δt / λ) From the above equation, Δt can be expressed as follows: Δt = (δ × λ) / (4 × π) Therefore, the above reflection phase δ is calculated using the following formula. i,j You should place a cell region with a thickness t that matches the given value. t=t min +Δt=t min +((δ×λ) / (4×π))

[0091] Furthermore, in the above equation, when Δt = λ / 2, δ = 2π [rad], and any reflection phase can be produced with a thickness less than that. Similarly, in the above equation, the reflection phase δ i,j If it exceeds 2π [rad], the reflection phase δ i,j The remainder of 2π is reflected as the phase δ i,j You can consider it that way.

[0092] Furthermore, the thickness t of the cell region does not need to strictly match the thickness obtained from the above formula; for example, it can be rounded to a thickness equivalent to a 2π / n [rad] (where n is a real number greater than 1, preferably 2 or more) step.

[0093] 2.Layer composition The reflector of this disclosure has a conductive layer on the surface with the uneven structure, and adjacent cell regions are electrically connected to each other.

[0094] The reflector only needs to have at least a conductive layer, for example, a base layer and a conductive layer disposed on the surface of the base layer, or it may have only a conductive layer.

[0095] The following description will be divided into two parts: a first embodiment in which the reflector has a base layer and a conductive layer, and a second embodiment in which the reflector has only a conductive layer.

[0096] (1) First aspect The reflector in this embodiment has a base layer and a conductive layer disposed on the surface of the base layer.

[0097] (a) conductive layer Herein, in this specification, "conductive layer" refers to a layer having a sheet resistance of 100 Ω / □ or less. The sheet resistance of the conductive layer is preferably 1 Ω / □ or less, and more preferably 0.01 Ω / □ or less. Furthermore, the lower limit of the sheet resistance of the conductive layer is not particularly limited, but for example, it can be 0.001 Ω / □ or more.

[0098] The sheet resistance of the conductive layer can be measured using the four-terminal method.

[0099] The conductive layer only needs to be placed on the surface of the reflector that has an uneven structure, but it is preferable to also place it on the side of the cell region in order to conduct electricity between adjacent cell regions.

[0100] The conductive layer is not particularly limited as long as it can reflect electromagnetic waves in a predetermined frequency band and satisfies the above-mentioned sheet resistance. Examples include metal films; metal oxide films such as ITO, IZO, AZO, GZO, and ATO; carbon films; and metal meshes.

[0101] The thickness of the conductive layer is not particularly limited as long as it can reflect electromagnetic waves in a predetermined frequency band and satisfies the above-mentioned sheet resistance. For example, it is preferably 100 nm to 100 μm, more preferably 100 nm to 10 μm, and even more preferably 1 μm to 10 μm.

[0102] The method for forming the conductive layer is not particularly limited as long as it can be formed on the substrate layer described later. Examples include PVD methods such as vacuum deposition and sputtering; CVD methods; and plating methods.

[0103] (b) Base material layer The base layer is a component that supports the conductive layer.

[0104] The material of the base layer is not particularly limited; for example, resin, glass, quartz, ceramics, etc., can be used. Among these, resin is preferred considering the ease of forming an uneven structure.

[0105] Furthermore, if the base layer contains resin, it may also contain conductive particles. In this case, even if the conductive layer is not placed on the side surface of the cell region, electrical conductivity can be established between adjacent cell regions.

[0106] Furthermore, if the base layer contains resin, it may also contain additives as needed.

[0107] The base layer may be, for example, a single layer or a multilayer layer. Furthermore, the base layer may have a base material portion and uneven portions arranged on the base material portion.

[0108] Furthermore, the base layer may be, for example, a single component in which all cell regions are formed integrally, or it may be a component in which individual cell regions are formed separately and block-shaped cell regions are arranged.

[0109] The method for forming the base layer is not particularly limited as long as it is capable of forming a predetermined uneven structure. Examples include cutting resin sheets, laser processing, molding using molds or vacuum casting, 3D printing, and joining of small parts. In the case of forming methods that do not use molds, such as cutting, laser processing, or 3D printing, customization according to the desired reflection angle is easy, making them suitable for special installation situations and for tuning the design when designing and developing large reflectors where simulation is difficult.

[0110] (2) Second aspect The reflector in this embodiment has only a conductive layer.

[0111] The definition of the conductive layer is the same as in the first embodiment described above.

[0112] The conductive layer is not particularly limited as long as it can reflect electromagnetic waves in a predetermined frequency band and satisfies the above-mentioned sheet resistance. Examples include metal films; metal oxide films such as ITO, IZO, AZO, GZO, and ATO; and carbon films.

[0113] The method for forming the conductive layer is not particularly limited as long as it is capable of forming a conductive layer having a predetermined uneven structure. Examples include cutting a metal sheet, molding using a mold, laser processing, fabrication using a metal 3D printer, and joining small parts.

[0114] Furthermore, the conductive layer may be, for example, a single component in which all cell regions are formed integrally, or it may be a combination of individually formed cell regions and an arrangement of block-shaped cell regions.

[0115] 3. Controlling the direction of electromagnetic wave reflection In the reflector of this disclosure, the reflection phase of electromagnetic waves can be controlled by changing the thickness of each cell region of the unit structure, thereby changing the round-trip optical path length of electromagnetic waves for each cell region. This allows the reflection direction of electromagnetic waves incident from a predetermined direction to be controlled by adjusting the size and planar pattern of the unit structure, as well as the number and thickness of the cell regions of the unit structure.

[0116] Furthermore, as described above, the reflection characteristics can be controlled by adjusting the length of the unit structure in a predetermined direction in which the thickness increases. For example, by shortening the length of the unit structure in a predetermined direction in which the thickness increases, the reflection angle of electromagnetic waves can be increased, while by lengthening the length of the unit structure in a predetermined direction in which the thickness increases, the reflection angle of electromagnetic waves can be decreased.

[0117] Furthermore, if we let t be the thickness of the cell region, b be the minimum thickness of the cell region during processing, and λ be the wavelength of the electromagnetic wave, and take the reflection phase when t=b as the reference (0), then the reflection phase δ can be expressed approximately as shown in the following equation. δ[rad] = 4 × π × {(tb) / λ)} From the above formula, the thickness t of the cell region can be expressed as follows: t = {(δ × λ) / (4 × π)} + b Therefore, the thickness t of the cell region expressed by the above formula is equal to the reflection phase δ of the cell region at the (i, j) position mentioned above. i,j They are arranged in such a way.

[0118] 4. Other configurations The reflector of this disclosure may have other configurations as needed.

[0119] (1) Ground layer If the reflector of this disclosure has the above-described base layer and conductive layer, it may also have a ground layer on the side of the base layer opposite to the conductive layer. The ground layer can block interference with objects on the back surface of the reflector and suppress the generation of noise. As the ground layer, a general conductive film such as a metal film, metal mesh, carbon film, or ITO film can be used.

[0120] (2) Fixing member When the reflector of this disclosure is used by being attached to, for example, a wall, a fixing member having a mechanism for attaching the reflector may be placed on the side of the reflector opposite to the uneven structure. In addition, a metal layer may be placed between the fixing member and the reflector to suppress interference between the fixing member and the reflector, or the fixing member may also serve as the metal layer. Furthermore, when the reflector of this disclosure is attached to a wall, the fixing member may have a mechanism to vary the angle in the normal direction of the reflector so that the discrepancy between the designed incident and reflected directions of electromagnetic waves and the actual incident and reflected directions of electromagnetic waves can be corrected.

[0121] 5. Characteristics of the reflector The reflector of this disclosure reflects electromagnetic waves of a specific frequency band in a direction different from the specular reflection direction. The frequency band of the electromagnetic waves is preferably 24 GHz or higher, and more preferably 24 GHz to 300 GHz. If the frequency band of the electromagnetic waves is within the above range, the reflector of this disclosure can be used in a fifth-generation mobile communication system, so-called 5G.

[0122] The reflector of this disclosure can be used, for example, as a reflector for communications, and is particularly suitable as a reflector for mobile communications.

[0123] This disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of this disclosure and achieves similar effects is included within the technical scope of this disclosure. [Examples]

[0124] The present disclosure will be specifically described below with reference to examples.

[0125] [Example 1] A simulation of the reflectivity characteristics of the reflector was performed. In the simulation, the unit structure of the reflector had a thickness distribution that increased in two directions, as shown in Figure 12(a), and consisted of a total of 36 cell regions of eight different thicknesses, with a periodic structure in which the unit structures were repeatedly arranged in each of the two directions. The following parameters were used for the reflector in the simulation.

[0126] Incident wave frequency: 28GHz Incident angle of incident wave: (θ, φ)=(20°, 90°) Desired reflection angle of the reflected wave: (θ, φ) = (45°, 0°) Thickness of each cell area: 0.1mm to 5.6mm Thickness difference between adjacent cell regions: 1.1 mm

[0127] The simulation results are shown in Figures 12(b) to (d). Figure 12(b) is a 3D representation of the bistatic radar cross-section of the reflector for electromagnetic waves arriving from the direction (θ, φ) = (20°, 90°). The axis extending from the lower left front is the x-axis, the axis extending from the lower right front is the y-axis, and the axis extending vertically is the z-axis, representing a right-handed Cartesian coordinate system. The polar coordinates (θ, φ) are defined accordingly, as shown in Figure 11 above. The RCS (radar cross-section) that appears to be reflected directly in front of the paper is the reflected wave according to this design. On the other hand, the RCS (radar cross-section) of the incident wave that passed around the reflector to the lower left front appears large, but this is because the air gap around the reflector was wider than the reflector in this simulation model, and is not related to the essence of this design. Figure 12(c) is a diagram showing the bistatic radar cross-section in the XZ plane swept with θ. Figure 12(d) shows the bistatic radar cross-section at θ=45° swept by φ. [Explanation of Symbols]

[0128] 1 … Reflector 3. Conductive layer 4 … Base material layer 10, 10a, 10b... Unit structure 11a-11g, 12a-12f, 13a-13e ... Cell regions D1 ... predetermined direction L… Length of the unit structure in a predetermined direction in which the thickness increases t1, t2, t3, t4, t5, t6 ... Thickness of the cell region

Claims

1. A reflector that reflects electromagnetic waves of a specific frequency band in a direction different from the specular reflection direction, It has an uneven structure in which multiple unit structures having a thickness distribution in which the thickness increases in a predetermined direction are arranged, The aforementioned unit structure has multiple cell regions of different thicknesses, The aforementioned unit structure comprises at least a first unit structure having two or more cell regions of different thicknesses, The surface on the uneven structure side has a conductive layer, and adjacent cell regions are electrically connected to each other. A reflector in which, when the wavelength of the electromagnetic wave is λ and n is an integer, the difference in thickness between adjacent cell regions in the unit structure is expressed as (λ / 2) / n.

2. A reflector that reflects electromagnetic waves of a specific frequency band in a direction different from the specular reflection direction, It has an uneven structure in which multiple unit structures having a thickness distribution in which the thickness increases in a predetermined direction are arranged, The aforementioned unit structure has multiple cell regions of different thicknesses, The aforementioned unit structure comprises at least a first unit structure having two or more cell regions of different thicknesses, The surface on the uneven structure side has a conductive layer, and adjacent cell regions are electrically connected to each other. In the aforementioned unit structure, the difference in thickness between adjacent cell regions is equal in the reflector.

3. A reflector that reflects electromagnetic waves of a specific frequency band in a direction different from the specular reflection direction, It has an uneven structure in which multiple unit structures having a thickness distribution in which the thickness increases in a predetermined direction are arranged, The aforementioned unit structure has multiple cell regions of different thicknesses, The aforementioned unit structure comprises at least a first unit structure having two or more cell regions of different thicknesses, The surface on the uneven structure side has a conductive layer, and adjacent cell regions are electrically connected to each other. In the aforementioned unit structure, the thickness of the minimum thickness cell region having the minimum thickness and the maximum thickness having the maximum A reflector in which the difference in thickness from the thick cell region is less than half the wavelength λ of the electromagnetic wave.

4. The reflector according to any one of claims 1 to 3, wherein the reflector comprises a base layer and the conductive layer disposed on the surface of the base layer.

5. The reflector according to claim 4, wherein the base material layer has a base material portion and an uneven portion disposed on the base material portion.

6. The reflector according to any one of claims 1 to 3, wherein the reflector has only the conductive layer.

7. The reflector according to claim 6, wherein the conductive layer is a single member in which all of the cell regions are integrally formed.

8. The reflector according to claim 6, wherein in the conductive layer, individual cell regions are formed separately, and block-shaped cell regions are arranged in a sequence.

9. The reflector according to any one of Claims 1 to 8, wherein when the wavelength of the electromagnetic wave is λ, m is an integer, and a is a real number of 0 or more, the thickness of the maximum thickness cell region having the maximum thickness in the unit structure is expressed as (λ / 2) × m + a.

10. The reflector according to any one of claims 1 to 9, having a periodic structure in which the unit structures are repeatedly arranged.

11. The unit structure comprises a second unit structure different from the first unit structure. A reflector according to any one of claims 1 to 10.

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