Reflectarray, reflectarray device, and reflectarray design method

Abstract

To provide a technique for improving an efficiency percentage.SOLUTION: A design method of a reflectarray of the present invention, is a design method of a reflectarray containing a reflection control region, and contains: a step of setting a reflection characteristic of the reflection control region; a step of determining a size of the reflection control region; a step of determining a size of a unit cell by dividing the reflection control region; a step of determining an element length of an element pattern arranged in the unit cell; a step of introducing a reflection phase of an element width of the element pattern as a design parameter, and acquiring an analysis result indicating a relation between the element width and the reflection phase; and a step of selecting the element width for realizing a desire reflection phase or an impedance on the basis of the analysis result.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reflectarray, a reflectarray device, and a method for designing a reflectarray. [Background technology]

[0002] With the advancement of digitalization in society, data communication speeds in wireless communications have increased dramatically, and the accompanying increase in the frequency of electromagnetic waves has been progressing. However, as the frequency of electromagnetic waves increases, they tend to travel in a more directional manner, meaning that they cannot bend around shadows of buildings, etc., and this can easily result in blind zones where communication is not possible. For these reasons, in order to realize 5G and 6G communications over a wide area, it is necessary to increase the number of base stations. However, increasing the number of base stations requires a large amount of cost, making it difficult to increase the number of base stations quickly. In recent years, technology that controls the direction of electromagnetic waves has been attracting attention as a solution to these issues.

[0003] Among these technologies, a reflector using a cross-shaped reflecting element has been developed. Patent Document 1 discloses the following points. The metasurface reflector includes a dielectric substrate, a metallic ground plane on the bottom surface of the dielectric substrate that blocks all polarization directions, and multiple supercells with two or more cross-shaped metallic resonators with different arm lengths. The supercells with metallic resonators are formed on the top surface of the dielectric substrate and are arranged with a diffraction grating period that reflects vertically and horizontally polarized incident waves and reflects extraordinary waves at a specified frequency with a required phase.

[0004] Furthermore, Patent Document 2 discloses the following points. A reflectarray has a plurality of reflecting elements arranged on a substrate, and reflects a first polarized wave having an electric field component parallel to the surface of the substrate and a second polarized wave having an electric field component perpendicular to the surface in first and second desired directions, respectively.Each of the plurality of reflecting elements has a patch spaced apart from a ground plane, and the gap between the patches of adjacent reflecting elements in a first axial direction is set to a value corresponding to the location of the gap so that the first polarized wave is reflected with a predetermined reflection phase, and the gap between the patches of adjacent reflecting elements in a second axial direction perpendicular to the first axis is set to a value corresponding to the location of the gap so that the second polarized wave is reflected with a predetermined reflection phase. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-48465 [Patent Document 2] Patent No. 5469724 Summary of the Invention [Problem to be solved by the invention]

[0006] In a reflectarray having an element pattern including a cross shape, if a dimensional error occurs in the element pattern, the reflection phase in each region tends to vary significantly from the design value, and the reflection intensity in the desired direction may decrease. This poses a problem in that it is difficult to increase the yield rate of reflectarrays. Furthermore, in neither Patent Document 1 nor Patent Document 2, sufficient consideration is given to the method of setting the design parameters. Therefore, an object of the present invention is to provide a technique for improving the yield rate of reflectarrays. [Means for solving the problem]

[0007] In order to solve the above problems, one representative reflectarray of the present invention is a reflectarray that has at least an element pattern, a dielectric layer, and a ground layer stacked in this order, and generates a predetermined asymmetric reflection of electromagnetic waves along a first direction, wherein the reflectarray includes at least one reflection control area, and the reflection control area includes n (n is an integer of 2 or more) unit cells divided at equal intervals in the first direction, and the mth element pattern arranged in the mth (m is an integer of 1 or more and n or less) unit cell has a different shape from the pth element pattern arranged in the pth (p is an integer of 1 or more and n or less other than m) unit cell, and the reflection characteristics of the mth unit cell are different from the reflection characteristics of the pth unit cell. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a technique for improving the yield rate of reflect arrays. Problems, configurations, and effects other than those described above will become apparent from the following description of the preferred embodiment of the invention. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the configuration of a reflect array. [Figure 2] FIG. 2 is a diagram showing an example of the arrangement of functional layers. [Figure 3] FIG. 3 is a diagram showing another example of the arrangement of the functional layers. [Figure 4] FIG. 4 is a diagram showing an example of the arrangement of unit cells according to the direction in which asymmetric reflection is to occur. [Figure 5] FIG. 5 is a diagram showing an example of the arrangement of unit cells according to the direction in which asymmetric reflection is to occur. [Figure 6] FIG. 6 is a diagram showing an example of the arrangement of unit cells according to the direction in which asymmetric reflection is to occur. [Figure 7] FIG. 7 is a diagram showing the configuration of the element pattern. [Figure 8] FIG. 8 is a diagram showing an example of a reflection control area. [Figure 9] FIG. 9 is a diagram showing a case where the element length in the x-axis direction and the element length in the y-axis direction are changed within the reflection control region. [Figure 10] FIG. 10 is a diagram showing examples of element pattern shapes and the widths of each element pattern. [Figure 11] FIG. 11 is a diagram showing an example of the shape of the element pattern after etching. [Figure 12] FIG. 12 is a diagram showing the structure of the reflect array described in the first embodiment in the xy plane. [Figure 13] FIG. 13 shows the analysis results of the unit cell in the design process of Comparative Example 1, and is a diagram showing the reflection phase when the element width of the element pattern is set to wx=wy=9.000 mm and the element length l is changed. [Figure 14] FIG. 14 is an analysis result of the reflectarray obtained in Comparative Example 1, showing the reflection characteristics of the reflectarray with and without dimensional error in the xz plane. [Figure 15] FIG. 15 shows the analysis results of the unit cell in the design process of Example 1, and is a diagram showing the reflection phase when the element width w of the element pattern is changed with the element length lx=ly=15.000 mm. [Figure 16] FIG. 16 is a diagram showing the analysis results of the reflectarray obtained in Example 1, illustrating the reflection patterns of the reflectarray with and without dimensional errors in the xz plane. [Figure 17] FIG. 17 shows the analysis results of the unit cell in the design process of Comparative Example 2, and is a diagram showing the reflection phase when the element width of the element pattern is set to wx=wy=1.000 mm and the element length 1 is changed. [Figure 18] FIG. 18 is a diagram showing the analysis results of the reflectarray obtained in Comparative Example 2, illustrating the reflection characteristics of the reflectarray with and without dimensional error in the xz plane. [Figure 19] FIG. 19 shows the analysis results of the unit cell in the design process of Example 2, and is a diagram showing the reflection phase when the element width w of the element pattern is changed with the element length lx=ly=3.250 mm. [Figure 20]FIG. 20 is an analysis result of the reflectarray obtained in Example 2, showing the reflection patterns of the reflectarray with and without dimensional error in the xz plane. [Figure 21] FIG. 21 shows the analysis results of the unit cell in the design process of Comparative Example 3, and is a diagram showing the reflection phase when the element width of the element pattern is set to wx=wy=0.500 mm and the element length 1 is changed. [Figure 22] FIG. 22 is an analysis result of the reflectarray obtained in Comparative Example 3, showing the reflection characteristics of the reflectarray with and without dimensional error in the xz plane. [Figure 23] FIG. 23 shows the analysis results of the unit cell in the design process of Example 3, and is a diagram showing the reflection phase when the element width w of the element pattern is changed with the element length lx=ly=1.700 mm. [Figure 24] FIG. 24 is a diagram showing the analysis results of the reflectarray obtained in Example 3, illustrating the reflection patterns of the reflectarray with and without dimensional errors in the xz plane. [Figure 25] FIG. 25 shows the analysis results of the unit cell in the design process of Comparative Example 4, and is a diagram showing the reflection phase when the element width 1 of the element pattern is changed with wx=wy=0.400 mm. [Figure 26] FIG. 26 is a diagram showing the analysis results of the reflectarray 6 obtained in Comparative Example 4, illustrating the reflection characteristics of the reflectarray with and without dimensional errors in the xz plane. [Figure 27] FIG. 27 shows the analysis results of the unit cell in the design process of Example 4, and is a diagram showing the reflection phase when the element width w of the element pattern is changed with the element length lx=ly=0.900 mm. [Figure 28] FIG. 28 is a diagram showing the analysis results of the reflectarray obtained in Example 4, illustrating the reflection patterns of the reflectarray with and without dimensional errors in the xz plane. [Figure 29] FIG. 29 is an analysis result of the reflectarray obtained in Example 5, showing the reflection characteristics of the reflectarray in the xz plane. [Figure 30] FIG. 30 is a diagram showing the analysis results of the reflectarray obtained in Example 6, illustrating the reflection characteristics of the reflectarray in the xz plane. [Figure 31] FIG. 31 is a diagram showing the analysis results of the reflectarray obtained in Example 7, illustrating the reflection characteristics of the reflectarray in the xz plane. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to this embodiment. In addition, in the description of the drawings, the same parts are designated by the same reference numerals. When there are multiple components with the same or similar functions, they may be described using the same reference numeral with different subscripts. When there is no need to distinguish between these multiple components, the subscripts may be omitted. To facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc. Therefore, the present disclosure is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

[0011] (Terminology explanation) In this disclosure, a "reflector array (electromagnetic wave reflector)" is a component that reflects electromagnetic waves. It is not limited to those that perform symmetric reflection where the angle of incidence and the angle of reflection are equal, but also includes those that perform asymmetric reflection where the angle of incidence and the angle of reflection are different, those that scatter electromagnetic waves in multiple directions, and those that concentrate electromagnetic waves at a specific location. In the following description, an xyz coordinate system is applied, and the reflector array is placed on the xy plane. The "reflection control area" refers to a part of the area that constitutes the reflect array. The reflection control area is the smallest area that can reflect electromagnetic waves incident on that area in a predetermined direction. The reflectarray is composed of one or more reflection control areas. The reflection control area includes not only a two-dimensional area in which the electromagnetic wave is incident in a direction parallel to the area, but also a layer structure formed in a direction perpendicular to the area. The term "unit cell" refers to a region obtained by dividing the reflection control region, and includes one element pattern. Also, "θi" indicates the angle of incidence of the incident wave. The angle of incidence in the x-axis direction is θix, and the angle of incidence in the y-axis direction is θiy. Also, "θr" indicates the angle of reflection of the reflected wave. The angle of reflection in the x-axis direction is θrx, and the angle of reflection in the y-axis direction is θry. The angle θx about the x-axis is expressed as a positive angle (0° to 180°) when it extends from the positive z-axis direction toward the positive x-axis direction, and as a negative angle (0° to -180°) when it extends from the positive z-axis direction toward the negative x-axis direction. Similarly, the angle θy about the y-axis is expressed as a positive angle (0° to 180°) when it extends from the positive z-axis direction toward the positive y-axis direction, and as a negative angle (0° to -180°) when it extends from the positive z-axis direction toward the negative y-axis direction. The element length in the x-axis direction is denoted as lx, and the element length in the y-axis direction is denoted as ly. The element width in the x-axis direction is denoted as wx, and the element width in the y-axis direction is denoted as wy.

[0012] [First embodiment] (Reflectarray configuration) The configuration of the reflectarray and the configuration of the element pattern will be described with reference to Figure 1. Figure 1 is a diagram showing the configuration of a reflectarray 6. The reflectarray 6 has multiple element patterns periodically arranged on a plane, allowing the direction of reflected waves to be set to a desired value. The reflectarray 6 includes at least an element pattern (element) 1, a dielectric layer 2, and a ground layer (base plate) 3. In the following description, an xyz coordinate system is applied, and the reflectarray 6 is arranged on the xy plane.

[0013] The reflectarray 6 in Fig. 1 generates a predetermined asymmetric reflection of electromagnetic waves along the x-axis. The reflectarray 6 in Fig. 1 has a configuration in which a plurality of reflection control regions identical to the reflection control region 5 are arranged in the x-axis and y-axis directions. In Fig. 1, the reflection control region 5 is shown by a solid line as a representative of the reflection control regions included in the reflectarray 6. The reflection control region 5 includes unit cells 41, 42, 43, ... 4 n (Hereinafter, when a unit cell is referred to without specifying it, it may be referred to as a "unit cell 4," where n is a positive integer of 2 or more.) The unit cells 4 are portions obtained by dividing the reflection control region 5 at equal intervals along the x-axis direction. n is the number of divisions when the reflection control region is divided into unit cells in the x-axis direction. If the size (length) of the unit cell 4 in the x-axis direction is sx and the size in the y-axis direction is sy, and the size of the reflection control region 5 in the x-axis direction is Lx and the size in the y-axis direction is Ly, then sx = Lx / n and sy = Ly. Note that, in FIG. 1 , the reflection control region 5 is configured by n unit cells 4 lined up in the x-axis direction, and the reflectarray 6 includes a plurality of reflection control regions 5, but the present disclosure is not limited to such a configuration. The reflection control region may be configured by unit cells lined up in the y-axis, or may include unit cells lined up in the x-axis and y-axis. The configuration of the reflection control region will be described later.

[0014] (Element pattern configuration) An element pattern is formed on the surface of the unit cell 4 facing the +z-axis direction. Using the division number n, unit cell 41, unit cell 42, ..., unit cell 4 n The element pattern 11 is formed in the unit cell 41. The element pattern 12 is formed in the unit cell 42. The element pattern 13 is formed in the unit cell 43. n Element pattern 1 n is formed. Furthermore, the element patterns are arranged at equal intervals within the reflection control area and between adjacent areas of the same reflection control area. Specifically, for each element pattern within reflection control area 5, if the size of the closest interval (hereinafter also referred to as "gap") between adjacent element patterns in the x-axis direction is gx, then within reflection control area 5, n are arranged at equal intervals of gx. n and a reflection control region 5x (shown by a broken line, element pattern 1) adjacent to the reflection control region 5 in the x-axis direction. x Unit cell 4 in which 1 was formed x 1. Element pattern 1 x 2 is formed in unit cell 4 x 2, ... Element pattern 1 x n Unit cell 4 formed x n Element pattern 1 x If the gap between 1 is Gx, then in FIG. 1, Gx and gx are equal. The element pattern of reflection control region 5 and reflection control region 5y (shown by a broken line, element pattern 1) adjacent to reflection control region 5 in the y-axis direction are y Unit cell 4 in which 1 was formed y 1. Element pattern 1 y 2 is formed in unit cell 4 y 2, ... Element pattern 1 y n Unit cell 4 formed y n The gaps between the element patterns are uniform and shown as Gy in FIG.

[0015] Within the reflection control region, each element pattern has a shape that is slightly different from the other element patterns. nThe shape of the element pattern shown in is sometimes called a cross patch. A cross patch refers to a shape in which two square patches intersect at right angles on the xy plane. Element pattern 11 has a shape in which a square patch having an element length lx1, which is the size in the x-axis direction, and an element width wy1, which is the size in the y-axis direction, and a square patch having an element length ly1, which is the size in the y-axis direction, and an element width wx1, which is the size in the x-axis direction, intersect at right angles with the center of gravity in common. Similarly, element pattern 1 n has a shape in which a square patch having an element length lxn and an element width wyn and a square patch having an element length lyn and an element width wxn are orthogonal to each other with a common center of gravity. The method for setting the element length and element width will be described later.

[0016] (Explanation of each configuration, design method) (Layer composition) The layer structure of the reflectarray 6 will be described with reference to Figures 2 and 3. Figures 2 and 3 are diagrams showing an example of the layer structure of the reflectarray 6. The reflectarray 6 has a structure in which at least an element pattern 1, a dielectric layer 2, and a ground layer 3 are stacked in a direction from the +z-axis direction to the -z-axis direction. In the following description, a structure consisting of three layers, i.e., the element pattern 1, the dielectric layer 2, and the ground layer 3, is referred to as the "basic structure." In practice, the reflectarray 6 preferably has one or more layers having various functionalities (hereinafter also referred to as "functional layers") stacked on either the element pattern 1 side or the ground layer 3 side of the basic structure, or on both sides. In the following description, layers included in the reflectarray other than the element pattern 1, the dielectric layer 2, and the ground layer 3 may be referred to as "functional layers" when the type of layer is not specified.

[0017] If necessary, a layer for improving the adhesion between the element pattern 1 and the dielectric layer 2, or between the ground layer 3 and the dielectric layer 2, may be formed. Also, a layer used for a purpose other than improving the adhesion may be formed. Note that intermediate products generated in the manufacturing process of the reflectarray 6 may be formed in layers and remain on the reflectarray 6.

[0018] Examples of functional layers include a design layer that is designed to take into consideration the landscape of the area where the reflect array 6 is installed, an installation layer that makes it easy to install the reflect array 6 on a support such as a wall or ceiling, a protective layer that protects the basic structure, and an adhesive layer for laminating each layer.

[0019] FIG. 2 is a diagram showing an example of the arrangement of the functional layer 7. The lamination method on the element pattern 1 side may be such that the functional layer 7 fills the gaps between the multiple element patterns 1, as in the reflectarray 6a (FIG. 2(a)), or such that the functional layer 7 contacts the upper surface of the element pattern 1 while maintaining the gaps between the multiple element patterns 1, as in the reflectarray 6b (FIG. 2(b)), or such that the functional layer 7 does not contact the upper surface of the element pattern 1, as in the reflectarray 6c (FIG. 2(c)). Note that if the reflectarrays 6a to 6c have a common configuration except for the functional layer 7, the reflectarrays 6a to 6c each have different reflection characteristics. Therefore, it is possible to change the characteristics of the reflectarray by changing the lamination method of the functional layer 7.

[0020] Figure 3 is a diagram showing another example of the arrangement of functional layers. Figure 3 shows an example of the arrangement of functional layers, including a protective layer 8, an adhesive layer 9, a design layer 10, and an installation layer 11. Figure 3(a) shows a reflectarray 6d in which a protective layer 8 is laminated to cover the element pattern 1 and the ground layer 3, and further includes a design layer 10 on the element pattern 1 side via an adhesive layer 9, and an installation layer 11 on the ground layer side via an adhesive layer 9. Figure 3(b) shows a reflectarray 6e in which an installation layer 11 is on the ground layer side via an adhesive layer 9, and a design layer 10 on the element pattern 1 side separated by an air gap.

[0021] (Reflection control area) The reflectarray 6 includes at least one reflection control area. The properties of the reflectarray can be changed by arranging the reflection control areas in a different manner. For example, when electromagnetic waves of a certain wavelength are incident at a certain angle of incidence, the reflectarray can be given the property of reflecting in a single direction by periodically arranging reflection control areas with a common reflection direction. Furthermore, when electromagnetic waves of a certain wavelength are incident at a certain angle of incidence, the reflectarray can be given the property of scattering the electromagnetic waves in multiple directions by configuring a reflectarray with reflection control areas each with a different reflection direction. Furthermore, by shifting the reflection direction by a predetermined angle for each reflection control area, it is possible to give the reflectarray the property of concentrating electromagnetic waves at a specific location. The frequency that is planned to be used for the reflectarray during design is hereinafter referred to as the "operating frequency."

[0022] The size Lx of the reflection control area in the x-axis direction is determined, for example, by equation (1), where λ is the wavelength of the operating frequency, θix is ​​the x-axis component of the angle of incidence of the electromagnetic wave incident on the reflection control area, and θrx is the x-axis component of the angle of reflection of the electromagnetic wave reflected from the reflection control area. When θix ≠ −θrx,

number

[0023] Furthermore, the size Ly of the reflection control area in the y-axis direction is determined, for example, by equation (2), where θiy is the y-axis component of the angle of incidence of the electromagnetic wave incident on the reflection control area, and θry is the y-axis component of the angle of reflection of the electromagnetic wave reflected from the reflection control area. When θiy ≠ -θry,

number

[0024] (Relationship between unit cell and reflection phase) The relationship between the unit cell and the reflection phase will be described with reference to FIGS. 4 to 6. FIGS. 4 to 6 are diagrams showing examples of unit cell arrangements according to the direction in which asymmetric reflection is generated. The reflection control region 5 has at least two unit cells. Here, FIG. 4(a) shows the direction of the electromagnetic wave (incident wave) incident on the reflectarray 6f and the direction of the electromagnetic wave (reflected wave) reflected from the reflectarray 6f. In other words, the thick solid arrows indicate the traveling direction of the wavefront, with the arrow pointing toward the reflectarray 6 indicating the traveling direction of the wavefront of the incident wave and the arrow pointing away from the reflectarray 6f indicating the traveling direction of the wavefront of the reflected wave. Also, FIG. 4(b) shows a plan view of the reflectarray 6f as seen from the z-axis direction. The relationship between (a) and (b) in FIGS. 5 and 6 is similar to that between (a) and (b) in FIG. 4.

[0025] The unit cells have the effect of reflecting incident electromagnetic waves with a predetermined phase difference. Because each unit cell in the reflection control region exhibits a different reflection phase, the wavefront of the reflected wave generated in the reflection control region is tilted from the reflection angle when the angle of incidence and the angle of reflection are equal, resulting in asymmetric reflection, which is different from symmetric reflection, where the angle of incidence and the angle of reflection are equal.

[0026] When reflectarray 6f is intended to perform asymmetric reflection only along the x-axis direction (θix ≠ -θrx as shown in Figure 4(a)), unit cells exhibiting different reflection phases along the x-axis direction are arranged in reflection control region 5a (Figure 4(b)). Reflection control region 5a has three unit cells arranged along the x-axis direction, with the number of divisions n = 3. The size Lx of reflection control region 5a in the x-axis direction is determined by equation (1), and the size of the unit cell in the x-axis direction is Lx / 3. When the y-axis component of the reflection angle is symmetric reflection (θiy = -θry), as represented in this example, Ly does not need to be determined by equation (2) and can take any value. However, for ease of design, a square unit cell whose size is determined by Lx and the number of divisions n is used for convenience, and Ly is set equal to Lx / 3.

[0027] Similarly, when reflectarray 6g is intended to perform asymmetric reflection only along the y-axis direction (θiy ≠ -θry as shown in Figure 5(a)), unit cells exhibiting different reflection phases are arranged along the y-axis direction in reflection control region 5b (Figure 5(b)). Here, m (m is a positive integer greater than or equal to 2) is the number of divisions when dividing the reflection control region into unit cells in the y-axis direction. Reflection control region 5b has three unit cells arranged in the y-axis direction, with the number of divisions m = 3. The size Ly of reflection control region 5b in the y-axis direction is determined by equation (2), and the size of the unit cell in the y-axis direction is Ly / 3. Because the x-axis component of the reflection angle is symmetric reflection, Lx does not need to be determined by equation (1) and can take any value. However, for ease of design, a square unit cell whose size is determined by Ly and the number of divisions m is used for convenience, and Lx is set equal to Ly / 3.

[0028] FIG. 6(a) shows the relationship between the reflectarray and electromagnetic waves, with FIG. 6(a1) showing the electromagnetic waves projected onto the zx plane and FIG. 6(a2) showing the electromagnetic waves projected onto the zy plane. When reflectarray 6h is intended to perform asymmetric reflection in both the x-axis and y-axis directions (θix ≠ -θrx as shown in FIG. 6(a1) and θiy ≠ -θry as shown in FIG. 6(a2)), unit cells with different reflection phases are arranged in reflection control region 5c along the x-axis, and unit cells with different reflection phases are also arranged along the y-axis (FIG. 6(b)). Reflection control region 5c includes nine unit cells, with three unit cells arranged along the x-axis and three unit cells arranged along the y-axis. The number of divisions in reflection control region 5c can also be expressed as 3 × 3 = 9, using the number of divisions in the x-axis direction (n = 3) and the number of divisions in the y-axis direction (m = 3). The size Lx of reflection control region 5c in the x-axis direction is determined by equation (1), and the size Ly of the y-axis direction is determined by equation (2). The size of the unit cell in the x-axis direction is determined by Lx and n and is Lx / 3. The size of the unit cell in the y-axis direction is determined by Ly and m and is Ly / 3. Both the x-axis and y-axis components of the incident wave are reflected asymmetrically. Therefore, the x-axis component of the reflected wavefront in the propagation direction is different from the x-axis component of the incident wavefront, and the y-axis component of the reflected wavefront in the propagation direction is different from the y-axis component of the incident wavefront (Figure 6(a)). Note that gx indicates the gap in the x-axis direction between element patterns within reflection control region 5c. gy indicates the gap in the y-axis direction between element patterns within reflection control region 5c. The spacing gx between element patterns in the x-axis direction is equal, and the spacing gy between element patterns in the y-axis direction is equal. Although the case where gx and gy are different is shown, gx and gy may also be equal. Furthermore, Gx denotes the gap between the element pattern of reflection control area 5c and the element pattern of the reflection control area adjacent to reflection control area 5c in the x-axis direction. Gy denotes the gap between the element pattern of reflection control area 5c and the element pattern of the reflection control area adjacent to reflection control area 5c in the y-axis direction. When a reflection control area identical to reflection control area 5c is adjacent to it in the y-axis direction without changing its position in the x-axis direction (or y-axis direction), gx and Gx are equal, and gy and Gy are equal.

[0029] (Distribution of reflection phase within the reflection control area, distribution of surface impedance) The distribution of reflection phases within the reflection control area is determined, for example, according to equations (3) and (4). Here, the wavelength of the operating frequency is λ (m), the x-axis component of the incident angle of the electromagnetic wave entering the reflection control area is θix, the y-axis component is θiy, the x-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control area is θrx, the y-axis component is θry, the reflection phases at arbitrary coordinates x1 and x2 parallel to the x-axis within the reflection control area are φx1 and φx2, respectively, the distance between coordinates x1 and x2 is dx, and the reflection phase difference between Φx1 and Φx2 is ΔΦx. Furthermore, the reflection phases at arbitrary coordinates y1 and y2 parallel to the y-axis are φy1 and φy2, respectively. When the reflection control area is intended to provide asymmetric reflection along the x-axis, it is preferable that equation (3) be satisfied. When the reflection control area is intended to provide asymmetric reflection along the y-axis, it is preferable that equation (4) be satisfied. Furthermore, when the reflection control region is intended to provide asymmetric reflection in both the x-axis direction and the y-axis direction, it is preferable that both formula (3) and formula (4) are satisfied.

number

number

[0030] Furthermore, instead of the reflection phase, the distribution of surface impedance can also be applied to the reflection control area. In this case, the distribution of surface impedance is expressed, for example, by equations (5) and (6). Here, Zsx is the surface impedance distribution parallel to the x-axis direction of the reflection control area, Zsy is the surface impedance distribution parallel to the y-axis direction of the reflection control area, and η1 is the impedance of the incident wave. Furthermore, the x-axis component of the incident angle of the electromagnetic wave incident on the reflection control area is defined as θix, the y-axis component as θiy, the x-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control area is defined as θrx, and the y-axis component as θry. Note that x1 and x2 indicate x coordinates as relative coordinates within the reflex control area, and any coordinate in the reflex control area can have the reference x = 0. Similarly, y1 and y2 indicate y coordinates as relative coordinates within the reflex control area, and any coordinate in the reflex control area can have the reference y = 0. Furthermore, k1 is the wave number of the reflected wave. j represents the imaginary unit. When the reflection control area is intended to perform asymmetric reflection along the x-axis direction, it is preferable that formula (5) be satisfied, and when the reflection control area is intended to perform asymmetric reflection along the y-axis direction, it is preferable that formula (6) be satisfied. When the reflection control area is intended to perform asymmetric reflection in both the x-axis direction and the y-axis direction, it is preferable that both formulas (5) and (6) be satisfied.

number

number

[0031] Other surface impedance distributions are expressed by, for example, equations (7) and (8). When the reflection control region is intended to cause asymmetric reflection only along the x-axis direction, it is preferable that equation (7) be satisfied, and when the reflection control region is intended to cause asymmetric reflection only along the y-axis direction, it is preferable that equation (8) be satisfied. Furthermore, when the reflection control region is intended to cause asymmetric reflection in both the x-axis and y-axis directions, it is preferable that equations (7) and (8) be satisfied simultaneously.

number

number

[0032] The above-mentioned formulas (3) to (8) are examples of design formulas used when designing the distribution of the reflection phase and the distribution of the surface impedance. The present disclosure is not limited to the use of formulas (3) to (8), and other design formulas can be selected as appropriate.

[0033] (element pattern) The details of the element pattern will be explained with reference to Figures 1 and 7 to 10. Generally, reflectarrays change their reflection characteristics by utilizing the resonance of the element pattern. Here, a linear or rectangular element pattern (square patch) mainly resonates with polarized waves in the direction along its long axis, so it is known that if an element pattern with a shape that intersects these at right angles is used, it can accommodate both TE and TM polarized waves.

[0034] In the reflectarray of the present disclosure, as the division numbers n and m of the reflection control region increase, the size of each unit cell and the size of the element pattern become smaller. Because resonance occurs only when a certain element pattern size is satisfied for the frequency, increasing n and m beyond a certain value makes it difficult to achieve asymmetric reflection at the operating frequency. On the other hand, as n and m are increased, the reflection characteristics can be controlled for each smaller region, and the reflection characteristics of the reflectarray approach the theoretical characteristics.

[0035] The element pattern in the reflectarray of the present disclosure includes a cross patch in the xy plane, where two square patches are orthogonal to each other. Here, as shown in Figure 1, the square patch that makes up the cross patch, with its long side in the x-axis direction, has an element length lx, which is the size of the long side, and an element width wy, which is the size of the short side, and the square patch that has its long side in the y-axis direction has an element length ly, which is the size of the long side, and an element width wx, which is the size of the short side. Therefore, the element pattern in unit cell 4n can be expressed as having element lengths lxn and lyn and element widths wxn and wyn.

[0036] FIG. 7 shows the configuration of an element pattern. One element pattern is arranged in a unit cell. The cross patches that make up the element pattern of a unit cell 4 may be such that the intersection point of two square patches is the same as the center of gravity of the unit cell (unit cell 4a in FIG. 7(a)), or may be different (unit cell 4b in FIG. 7(b) and unit cell 4c in FIG. 7(c)). These cross patch variations can be selected as appropriate, which increases the flexibility and scalability of the design.

[0037] In this disclosure, the element widths wx and wy are treated as design parameters, and each element pattern included in the reflection control region is designed to have a different element width. The element width wx can be varied within a range up to a value equal to the element length lx, and the element width wy can be varied within a range up to a value equal to the element length ly. The element widths wx and wy within the same element pattern may be equal or different. If they are different values, the characteristics for TE and TM polarization can be controlled individually.

[0038] FIG. 8 illustrates an example of a reflection control region. FIG. 8(a) illustrates an example in which element widths wx and wy are equal within the same element pattern, while FIG. 8(b) illustrates an example in which element widths wx and wy are different. In this example, n=3, the element pattern shape consists solely of two orthogonal rectangular patches, and lx and ly are equal. Meanwhile, within the reflection control region, the first element width wx, which is the width of the element pattern in the x-axis direction, and / or the second element width wy, which is the width of the element pattern in the y-axis direction, differ for each element pattern arranged in each unit cell. More specifically, in reflection control region 5d in FIG. 8(a), the element width wx1 in the x-axis direction of element pattern 1d1 is equal to the element width wy1 in the y-axis direction. The element width wx2 in the x-axis direction of element pattern 1d2 is equal to the element width wy2 in the y-axis direction. The element width wx3 in the x-axis direction of element pattern 1d3 is equal to the element width wy3 in the y-axis direction. 8(b), element pattern 1e1 has an element width wx1 in the x-axis direction that is smaller than its element width wy1 in the y-axis direction. Element pattern 1e2 has an element width wx2 in the x-axis direction that is larger than its element width wy2 in the y-axis direction. Element pattern 1e3 has an element width wx3 in the x-axis direction that is larger than its element width wy3 in the y-axis direction.

[0039] In the reflection control regions described so far, the element length lx in the x-axis direction is equal for each element pattern, and the element length ly in the y-axis direction is equal for each element pattern. Here, lx and ly may be equal or different. When lx and ly are different, characteristics for TE and TM polarization can be individually imparted to each element pattern.

[0040] FIG. 9 is a diagram showing a case where the element length in the x-axis direction and the element length in the y-axis direction are changed within the reflection control region. FIG. 9(a) shows an example of the case where lx and ly are equal, FIG. 9(b) shows an example of the case where lx > ly, and FIG. 9(c) shows an example of the case where lx < ly. In this example, n = 3, the element pattern shape consists only of a shape in which two rectangular patches are orthogonal, and wx and wy within the same element pattern are assumed to be equal. Specifically, in the reflection control region 5f of FIG. 9(a), each element pattern has an element length lx in the x-axis direction and an element length ly in the y-axis direction. Also in the reflection control region 5g of FIG. 9(b) and the reflection control region 5h of FIG. 9(c), the element lengths lx and ly between the element patterns are common.

[0041] Regarding the gaps, there are cases where only gx is equal between the element patterns within the reflection control region, cases where only gy is equal between the element patterns within the reflection control region, cases where gx and gy are respectively equal between the element patterns within the reflection control region and gx ≠ gy, and cases where gx and gy are respectively equal between the element patterns within the reflection control region and gx = gy.

[0042] FIG. 10 is a diagram showing an example of the element pattern shape and the width of each element pattern. FIG. 10(a) is an element pattern 1a having a shape in which rectangular patches are orthogonal, and FIG. 10(b) is an element pattern 1b having a shape generally called an Elsalam cross. FIG. 10(c) is an element pattern 1c in which an annular ring is arranged so as to surround the shape of FIG. 10(a). As shown in element patterns 1a to 1c, the two rectangular patches are orthogonal with a common center of gravity, and the shape of the element pattern in the xy plane is line-symmetric with respect to the x-axis and the y-axis. Here, a case where the element patterns are orthogonal with a common center of gravity is shown, but the present disclosure is not limited thereto. The two rectangular patches may be orthogonal without having a common center of gravity.

[0043] (Manufacturing method) The main manufacturing method for the basic structure of a reflectarray is to form an element pattern by cutting or etching a copper-clad laminate used in printed circuit boards, etc., or a dielectric layer on one or both sides of which a metal film has been formed by dry coating using vapor deposition or sputtering, plating or wet coating, etc. Specifically, a copper clad laminate is made by laminating copper foil to an insulator, which is a substrate such as glass cloth impregnated with a resin such as epoxy. The copper clad laminate has a plate-like shape, with copper foil laminated on both sides of the plate-like insulator. The copper foil on one side serves as the element pattern 1, and the copper foil on the other side serves as the ground layer 3. The insulator corresponds to the dielectric layer 2. When metal films are formed on both sides of the dielectric, the element pattern 1 is formed from one metal film, and the other metal film is applied to the ground layer 3. The dielectric becomes the dielectric layer 2.

[0044] FIG. 11 shows an example of the shape of the element pattern after etching. FIG. 11(a) shows a plan view of the element pattern 1, and FIGS. 11(b) to 11(d) show cross-sectional views of the element pattern 1. As shown in FIG. 11(a), the element pattern 1 is formed by a rectangular patch having an element length lx and an element width wy, and a rectangular patch having an element length ly and an element width wx, which are orthogonal to each other. Either dry etching or wet etching may be used for the etching method. When etching is used, corner rounding (FIG. 11(a)) or pinholes may occur in the element pattern 1. It is also expected that the cross-section of the element pattern 1 may have a forward taper (FIG. 11(b)), a reverse taper (FIG. 11(c)), or rounding (FIG. 11(d)). In FIG. 11, the thickness of the element pattern 1 is denoted by t. When etching is used, the cross-sectional shape of the element pattern is preferably a forward taper shape that widens in the -z-axis direction. The forward tapered shape increases the surface area of ​​the element pattern, making it possible to increase the adhesive strength with the functional layer when the functional layer is laminated, as will be described later.

[0045] Furthermore, due to the materials and manufacturing process, the final reflectarray may have a warp with a curvature radius of approximately R = 10 m.

[0046] Even if the above-mentioned shape change occurs, if the direction of the main beam changes by about ±5°, this is considered to be an acceptable reflection characteristic of the reflectarray.

[0047] Generally, in the case of cutting, the dimensional error of the element pattern is about ±100 μm, and in the case of etching, the dimensional error of the element pattern is about ±50 μm.

[0048] Other manufacturing methods include directly forming the element pattern and ground layer on the dielectric layer, printing using letterpress printing, lithographic printing, intaglio printing, stencil printing, transfer printing, etc., or masking the dielectric layer except for the element pattern area with masking tape or a masking agent, and then forming the element pattern using dry coating, plating, painting, or spraying.

[0049] Lamination of other layers (functional layers 7 such as protective layer 8, adhesive layer 9, design layer 10, installation layer 11, etc.) onto the basic structure can be performed by laminating, printing / coating, or extrusion molding. Examples of laminating methods include, but are not limited to, dry lamination, wet lamination, thermal lamination, and extrusion lamination.

[0050] When a large-sized reflectarray is required, multiple reflectarrays may be arranged to form a single reflectarray. In this case, during installation, it is expected that there will be misalignment between the reflectarrays in the x-axis direction, misalignment in the y-axis direction, and gaps between the reflectarrays of about 5 mm. It is also expected that each reflectarray will be misaligned in a direction that rotates by about 5° on the xy plane.

[0051] Even if the above changes occur, if the direction of the main beam changes by about ±5°, this is considered to be an acceptable reflection characteristic of the reflectarray.

[0052] (element pattern) The element pattern preferably has a surface resistance of 100 Ω / □ or less. Materials used for the element pattern include conductive materials such as inorganic oxide materials, metal materials, and conductive organic materials. Examples of inorganic oxide and metal materials include indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), antimony tin oxide, Ag, Al, Au, Pt, Pd, Cu, Co, Cr, In, Ag-Cu, Cu-Au, and Ni. Nanoparticles or nanowires containing at least one of these materials may also be used. Examples of conductive organic materials include polythiophene derivatives, polyacetylene derivatives, polyaniline derivatives, polypyrrole derivatives, carbon nanotubes, and graphene. Cu and Al are particularly preferred from the standpoints of material cost, conductivity, and film formation. Furthermore, a transparent reflect array can be fabricated using ITO or a mixture of polyethylenedioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT / PSS). The thickness of the element pattern is, for example, 10 nm to 18 μm. From the viewpoints of flexibility, film formation, stability, sheet resistance, and low cost, it is preferable to use a film formed by vapor deposition as the element pattern.

[0053] The material of the element pattern may be the same as that of the ground layer, or a different material may be used. For example, at least one of the layers of the ground layer or the element pattern may be formed from Cu or Al. Cu has excellent conductivity, which reduces conductor loss. Al has low density, is lightweight, and is inexpensive, allowing for the formation of a lightweight and inexpensive reflectarray. Furthermore, the thickness of at least one of the layers may be 1 μm or less. By making the thickness 1 μm or less, flexibility is improved, making it easier to install the reflectarray on curved surfaces, and weight reduction is also possible.

[0054] The above materials can be used in the form of a continuous film, a mesh, or a punched shape.

[0055] When the element pattern is mesh-shaped, the line width of the mesh is preferably 5 μm to 30 μm, more preferably 6 μm to 15 μm. The line spacing of the mesh is preferably 50 μm to 500 μm, more preferably 100 μm to 300 μm. Furthermore, when the wavelength at the operating frequency is λ, the line spacing of the mesh is preferably 0.5×λ or less, more preferably 0.1×λ or less, and even more preferably 0.01×λ or less. If the line spacing of the mesh is 0.5×λ or less, performance can be ensured. Furthermore, the line spacing of the mesh may be 0.001×λ or more.

[0056] When the element pattern is mesh-shaped or when a transparent conductive material is used, the reflect array exhibits visible light transparency, making it possible to maintain the appearance after installation.

[0057] When the element pattern is in the form of a thin film, the flexibility of the reflectarray can be improved, making it possible to use it on curved surfaces and to carry out roll-to-roll production processes.

[0058] When the element pattern is formed using a thin film, it is preferable that the thickness is greater than the skin depth calculated from equation (9), where d is the skin depth, ω is the angular frequency, μ is the magnetic permeability of the material, and σ is the electrical conductivity of the material.

number

[0059] Furthermore, in order to increase the reflection efficiency of electromagnetic waves, it is necessary to reduce the loss due to the element pattern, and therefore it is preferable that the surface roughness of the element pattern is small.

[0060] (dielectric layer) The dielectric layer may be made of a simple resin or a composite material in which paper, glass fiber, carbon fiber, or the like is impregnated with resin.

[0061] Examples of simple resins include polyethylene (εr = 2.2 to 2.4), polypropylene (εr = 2.0 to 2.6), polystyrene (εr = 2.4 to 2.6), polyvinyl chloride (εr = 2.8 to 8.0), AS resin (εr = 2.6 to 3.1), ABS resin (εr = 2.4 to 4.1), polyethylene terephthalate (εr = 2.9 to 3.0), acrylic resin (εr = 2.7 to 4.5), urethane resin (εr = 4.0 to 7.1), epoxy resin (εr = 2.5 to 6.0), and nylon (εr Examples of suitable dielectric materials include polyimide (εr = 3.0 to 5.0), polyimide (εr = 2.4 to 2.7), fluororesin (εr = 2.0 to 2.6), polycarbonate (εr = 2.9 to 8.9), polyphenylene ether (εr = 2.8 to 8.2), polyphenylene sulfide (εr = 3.2 to 4.6), polyvinylidene fluoride (εr = 6.4 to 10.0), polyethylene naphthalate (εr = 2.9), phenolic resin (εr = 3.0 to 12.0), and cycloolefin polymer (εr = 2.3 to 2.5). Here, εr indicates the relative dielectric constant. In particular, polyethylene terephthalate (PET) is preferred because of its low cost and versatility. The dielectric layer can be a single layer or multiple layers. The dielectric layer may be made of a foamed material made from the above materials. A highly flexible foam is preferably used as the foam.

[0062] Examples of composite materials include paper / phenolic resin, paper / epoxy resin, glass / epoxy resin, and glass / fluororesin composite materials.

[0063] Another example is the use of a mixture containing resin components or a dielectric compound and a resin component, from the viewpoint of adjusting the dielectric constant. The relative dielectric constant of the mixture can be adjusted by selecting the dielectric compound and its content.

[0064] The relative dielectric constant of a mixture can be predicted, for example, by using the Maxwell-Garnett law. In a mixture of dielectric A with a relative dielectric constant εa and dielectric B with a relative dielectric constant εb, when the volume fraction of A is δa, the relative dielectric constant εm of the mixture is given by the relational expression (10).

number

[0065] Examples of the dielectric compound include barium titanate (εr=250 to 20000), titanium oxide (εr=83 to 183), lead zirconate titanate, strontium tantalate bismuthate, and bismuth ferrite.

[0066] When a transparent dielectric is used, the reflectarray exhibits visible light transmittance, making it possible to maintain the appearance after installation.

[0067] The relative dielectric constant of the dielectric layer is preferably in the range of 1 or more and 20 or less, more preferably in the range of 1 or more and 10 or less, and even more preferably in the range of 2 or more and 4 or less. When the relative dielectric constant is within the above range, the desired reflection phase characteristics tend to be easily obtained in the reflectarray 1. Furthermore, the dielectric loss tangent is preferably in the range of 0.00005 or more and 0.01 or less, and more preferably in the range of 0.00005 or more and 0.001 or less. When it is within the above range, a reflectarray 1 with low dielectric loss can be produced.

[0068] The dielectric layer can be formed by, for example, wet coating such as die coating, comma coating, or gravure coating, melt extrusion such as T-die method or inflation method, calendar film formation method, solution casting method, heat press method, etc. Alternatively, a co-extrusion method in which multiple resins are extruded in multiple layers to form a film may be used.

[0069] The thickness of the dielectric layer is selected appropriately depending on the design frequency. When the design frequency is 28 GHz, it is preferably 40 μm or more and 250 μm or less, and more preferably 50 μm or more and 200 μm or less. If it is too thin, it becomes difficult to ensure the reflection phase, making the design of the reflectarray 1 difficult. On the other hand, if it is too thick, it tends to become difficult to ensure the reflection phase, lose flexibility, and increase the total thickness of the reflectarray, making it difficult to save space. For this reason, the thickness of the dielectric layer is preferably 250 μm or less. When the design frequency is 60 GHz, the thickness of the dielectric layer is preferably 10 μm or more and 250 μm or less. When the design frequency is 100 GHz or more, it is easier to design the reflectarray if the thickness of the dielectric layer is between several μm and 100 μm.

[0070] (Ground layer) The ground layer is provided to reflect electromagnetic waves that reach the reflect array and also serves to support and protect the dielectric layer. The ground layer is made of a conductive material such as an inorganic oxide material, a metal material, or a conductive organic material.

[0071] Examples of inorganic oxide and metal materials include indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), antimony tin oxide, Ag, Al, Au, Pt, Pd, Cu, Co, Cr, In, Ag-Cu, Cu-Au, and Ni. Nanoparticles or nanowires containing at least one of these materials may also be used. Conductive organic materials include polythiophene derivatives, polyacetylene derivatives, polyaniline derivatives, polypyrrole derivatives, carbon nanotubes, and graphene. Cu and Al are particularly preferred from the perspectives of material cost, conductivity, and film formation. To reflect electromagnetic waves, a surface resistance of the ground layer of 100 Ω / □ or less is desirable. If this requirement can be met, transparent reflect arrays can be fabricated using ITO or a mixture of polyethylenedioxythiophene (PEDOT) and polystyrene sulfonate (PSS) (PEDOT / PSS).

[0072] The above materials can be used in the form of a continuous film, a mesh, a punched shape, or a periodic structure.

[0073] Here, mesh refers to a state in which a conductor has a mesh-like opening on its plane. When the conductor is formed in a mesh shape, the mesh may be rectangular or diamond-shaped. When the mesh is formed in a rectangular shape, the mesh is preferably square. Square meshes provide good design. They may also be randomly shaped by a self-organizing method. Making the mesh random can prevent moire. When processing metal into a mesh shape, methods such as punching a metal plate or etching a metal plate can be used.

[0074] When the ground layer is mesh-like or a transparent conductive material is used, the reflect array exhibits visible light transparency, allowing the appearance to be maintained after installation.

[0075] When the ground layer is mesh-shaped, the line width of the mesh is preferably 5 μm to 30 μm, more preferably 6 μm to 15 μm. The line spacing of the mesh is preferably 50 μm to 500 μm, more preferably 100 μm to 300 μm. Furthermore, when the wavelength at the operating frequency is λ, the line spacing of the mesh is preferably 0.5 × λ or less, more preferably 0.1 × λ or less, and even more preferably 0.01 × λ or less. If the line spacing of the mesh is 0.5 × λ or less, performance can be ensured. Furthermore, the line spacing of the mesh may be 0.001 × λ or more.

[0076] When a metal material is used, the method for forming the ground layer can be selected from dry coating such as sputtering or vapor deposition, wet coating such as gravure coating or die coating by turning the metal material into ink, and surface treatment such as plating. Alternatively, a rolled metal plate can be used as the ground layer. When an inorganic oxide material is used, dry coating can be selected as the method for forming the ground layer 11. When an organic material is used, wet coating can be selected as the method for forming the ground layer 11. Alternatively, the ground layer can be formed by painting or spraying.

[0077] If the ground layer is in the form of a thin film formed by plating or vapor deposition, the flexibility of the reflectarray can be improved, making it possible to use it on curved surfaces or implement a roll-to-roll production process.

[0078] When the ground layer is in the form of a thin film, its thickness is preferably larger than the skin depth calculated from equation (9) in the same manner as the element pattern.

[0079] Furthermore, in order to increase the reflection efficiency of electromagnetic waves, it is also necessary to reduce loss due to the ground layer, so it is preferable that the surface roughness of the ground layer is small.

[0080] When the ground layer has a periodic structure, it can selectively reflect or transmit specific frequencies. For example, when a structure with periodically arranged patch-like conductive patterns is used as the ground layer, it is possible to reflect only specific frequencies, thereby imparting the ability to transmit frequencies other than the operating frequency. Furthermore, when a structure with periodically arranged holes where no conductive material exists is used, it is possible to design a reflect array that asymmetrically reflects the operating frequency while transmitting only specific frequencies.

[0081] (Support) The reflectarray is installed on a support. The support may be a newly installed panel or pole, or an existing signboard, wall, ceiling, etc. It is also possible to use such an existing support. The support preferably has a mechanism that can adjust the angle of the reflectarray in the vertical or horizontal direction, and more preferably has a mechanism that can move the position of the reflectarray up, down, left, and right. The reflectarray is installed on the support and used as a reflectarray device.

[0082] (installation layer) The mounting layer is a layer used to fix the reflectarray to the support. For example, an adhesive layer, a sticky layer, or a magnet can be used if the support is made of metal. When a magnet is used, the position and angle of the reflectarray can be easily changed.

[0083] (Design layer) The design layer is a layer for imparting design to the surface of the reflectarray. For example, when used as a building material such as wallpaper, a design layer may be further provided to harmonize with the space. When used as a whiteboard, a functional film may be used as the design layer. The design layer may also be given the function of the protective layer described below.

[0084] (protective layer) The protective layer may be a film or sheet having gas barrier properties, water vapor barrier properties, water resistance, abrasion resistance, and scratch resistance to prevent oxidation deterioration, physical damage, or peeling of the element pattern or ground layer.

[0085] When it is assumed that the reflectarray will be used indoors, it is preferable to use a protective layer that has antibacterial properties, antiviral properties, contamination resistance, etc. When it is assumed that the reflectarray will be used outdoors, weather resistance is required, so a layer containing UVA (ultraviolet absorber) or HALS (light stabilizer) may be used.

[0086] [Evaluation results (Examples and Comparative Examples)] The results of Examples 1-4 and Comparative Examples 1-4 are summarized in Table 1, and the results of Examples 5-7 are summarized in Table 2. 12 is a diagram showing the structure of the reflect array in the xy plane of Example 1. Note that the unit of dimensions in the diagram is mm. [Table 1] [Table 2]

[0087] (Comparative Example 1) A reflectarray 6 with a basic configuration was constructed using 0.018 mm thick copper for the element pattern 1 and ground layer 3, and a 1.564 mm thick glass / epoxy resin composite material for the dielectric layer 2. However, the conductivity of copper was set to 5.8 x 10^7 siemens / m, the real part of the relative permittivity of the dielectric layer 2 was set to 4.5, and tan δ was set to 0.014.

[0088] The operating frequency was set to 4.85 GHz, the target reflection characteristics (desired reflection characteristics) were set to θix = -60°, θrx = 0°, θiy = θry = 0°, and the size Lx of the reflection control area 5 in the x-axis direction was determined to be 71.376 mm using equation (1).

[0089] The number of divisions in reflection control region 5 was set to 3, and the size of the unit cell in the x-axis and y-axis directions was set to 23.792 mm. The shape of the element pattern was a cross patch in which two square patches intersected at right angles on the xy plane. Here, only the element length differed among the element patterns in reflection control region 5; specifically, the element lengths were lx1 = ly1, lx2 = ly2, lx3 = ly3, and the element widths were wx1 = wx2 = wx3 = wy1 = wy2 = wy3 = 9.000 mm. In Tables 1 and 2 and in the figures and text in the following explanation, the unit cells included in reflection control region 5 will be represented as unit cell 1, unit cell 2, ... unit cell p (p is an integer greater than or equal to 1 and less than or equal to the number of divisions n), and in unit cell p, the element length in the x-axis direction will be lxp, the element length in the y-axis direction will be lyp, the element width in the x-axis direction will be wxp, and the element width in the y-axis direction will be wyp. However, if lxp and lyp are equal, the subscripts x and y will be omitted, and if wxp and wyp are equal, the subscripts x and y will be omitted, and the subscript p may be omitted if the unit cell is not specified.

[0090] First, the reflection phase of the unit cell versus element length l was analyzed using finite element analysis software (HFSS) from Ansys. FIG. 13 shows the analysis results of the unit cell in the design process of Comparative Example 1, and is a diagram illustrating the reflection phase when the element width of the element pattern is set to wx = wy = 9.000 mm and the element length l is changed. The reflection phase changed as the element length l changed. Note that in FIG. 13, the element length l on the horizontal axis represents the element length lx in the x-axis direction and the element length ly in the y-axis direction. In the following explanation, the diagrams of element length l and reflection phase will show the same conditions as FIG. 13.

[0091] Next, based on the analysis results of the unit cell, the element length l in each unit cell was determined so as to follow the impedance distribution of equation (7). The element lengths l were set to lx1 = ly1 = 14.750 mm, lx2 = ly = 11.412 mm, and lx3 = ly3 = 15.237 mm, respectively. The element length l of each element pattern determined here was set to have no dimensional error.

[0092] The reflectarray 6 has 12 x 12 unit cells arranged in the x-axis and y-axis directions, and its size in the xy plane is 285.504 mm square. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto the reflectarray 6 at θix = -60° and θiy = 0°.

[0093] In order to understand the effect of dimensional errors on the reflection characteristics, a dimensional error due to cutting was assumed, and a similar analysis was performed when the element length l of each element pattern of the reflect array 6 was increased by 0.100 mm.

[0094] FIG. 14 is an analysis result of the reflectarray 6 obtained in Comparative Example 1, and is a diagram showing the reflection characteristics of the reflectarray 6 with and without a dimensional error in the xz plane. In FIG. 14, the horizontal axis is the reflection angle θrx, and the vertical axis is the RCS (radar cross section). RCS is a value that substantially corresponds to the intensity of the reflected wave. In the reflectarray 6 without a dimensional error, the electromagnetic wave incident at θix=-60° was reflected in the desired direction of θrx=0°, and the RCS was 7.06 dBsm. On the other hand, in the reflectarray 6 with a dimensional error, although reflection occurred in the direction of θrx=0°, the RCS was 6.87 dBsm, and the change in RCS due to the dimensional error was -0.18 dBsm.

[0095] Example 1 A reflectarray was prepared that was similar to the reflectarray described in Comparative Example 1 except for the element pattern shape. The element pattern shape was such that only the element width of each element pattern in reflection control region 5 was different, specifically the element length of each element pattern was lx1 = lx2 = lx3 = ly1 = ly2 = ly3 = 15,000 mm, and the element widths within the same element pattern were wx1 = wy1, wx2 = wy2, wx3 = wy3. The reflection phase of the unit cell relative to the element width w and the reflection characteristics of the reflectarray 6 with and without dimensional error were analyzed using HFSS.

[0096] FIG. 15 shows the analysis results of the unit cell in the design process of Example 1, and illustrates the reflection phase when the element length of the element pattern is lx = ly = 15,000 mm and the element width w is changed. In FIG. 15, the element width w on the horizontal axis represents the element width wx in the x-axis direction and the element width wy in the y-axis direction. In the following description, the diagrams of the element width w and reflection phase show the same conditions as in FIG. 15. The reflection phase changed as the element width changed. Furthermore, the slope of the reflection phase relative to the element width was gentler compared to the case of Comparative Example 1 shown in FIG. 13, in which the element length was changed. For example, to change the reflection phase from 120° to -120°, in Comparative Example 1, the element length l needs to be changed by 2.5 mm, from approximately 13.5 mm to 16 mm, whereas in Example 1, the element length w needs to be changed by 6 mm, from approximately 5 mm to 11 mm. This means that when a dimensional error of the same magnitude occurs, the present invention, which uses the element width as a design parameter, has a smaller change in the reflection phase in the unit cell, and as a result, the change in the reflection characteristics of the reflectarray 6 is smaller.

[0097] The element widths w were determined to be wx1 = wy1 = 8.306 mm, wx2 = wy2 = 1.305 mm, and wx3 = wy3 = 9.608 mm, respectively. Figure 16 shows the analysis results of the reflectarray 6 obtained in Example 1, illustrating the reflection patterns of the reflectarray 6 with and without dimensional errors in the xz plane. In the reflectarray 6 without dimensional errors, electromagnetic waves incident at θix = -60° were reflected in the desired direction of θrx = 0°, with an RCS of 7.03 dBsm. Furthermore, in the reflectarray 6 with dimensional errors, reflection occurred in the direction of θrx = 0°, with an RCS of 7.02 dBsm. Therefore, the change in RCS due to dimensional errors was -0.02 dBsm, and compared to the reflectarray 6 in which the element length described in Comparative Example 1 was used as a design parameter, the decrease in reflection intensity due to dimensional errors was successfully suppressed.

[0098] The design method will now be described in detail. The design method described here is for a reflectarray in which a plurality of identical reflection control regions are arranged in the x-axis and y-axis directions. (Step 1) First, set the target reflection characteristics (operating frequency, incident angle, and reflection angle). (Step 2) Next, the sizes Lx and Ly of the reflection control area are determined using equations (1) and (2). If asymmetric reflection is desired only in the x-axis direction, Lx is determined using equation (1), and Ly is set to any size. If asymmetric reflection is desired only in the y-axis direction, Ly is determined using equation (2), and Lx is set to any size. (Step 3) Next, the size of the reflection control area Lx is divided into n parts, and Ly is divided into m parts, thereby determining the size of the unit cell. (Step 4) Next, the element lengths lx and ly of the element patterns are determined so that they fit within the unit cell. Since the element patterns are arranged evenly within the unit cell, the gaps gx and gy between the element patterns are also determined. (Step 5) Next, the reflection phase of the unit cell is analyzed using the element width w as a design parameter. As shown in Fig. 15, the reflection phase is derived using the element widths wx and wy of the element pattern as design parameters, and an analysis result showing the relationship between the element width and the reflection phase in the unit cell is obtained. (Step 6) Next, the ideal reflection phase or impedance for realizing the reflection characteristics of the target reflection control region is calculated using equations (3) to (8), and the element width w that realizes the desired reflection phase or impedance is selected based on the above analysis results. In the case of Example 1, three element widths are selected, and a reflection control region including three unit cells is set. (Step 7) Next, a reflectarray is formed so as to include at least one reflection control region. The reflection characteristics of the reflectarray are analyzed. (Step 8) Based on the analysis results of Step 7, it is also possible to further fine-tune the element widths wx and wy using an optimization method so that the RCS at the target reflection angle is further increased and the RCS at angles other than the target angle is reduced.

[0099] (Comparative Example 2) A reflectarray 6 with a basic configuration was constructed using 0.018 mm thick copper for the element pattern 1 and ground layer 3, and a 0.764 mm thick glass / fluororesin composite material for the dielectric layer 2. However, the conductivity of copper was set to 5.8 x 10^7 siemens / m, the real part of the relative permittivity of the dielectric layer 2 was set to 2.6, and tan δ was set to 0.0025.

[0100] The operating frequency was set to 27.2 GHz, the target reflection characteristics were set to θix = 33°, θrx = 0°, θiy = θry = 0°, and the size Lx of reflection control area 5 in the x-axis direction was determined to be 20.238 mm using equation (1).

[0101] The number of divisions in reflection control region 6 was set to 3, and the size of the unit cell in the x-axis and y-axis directions was set to 6.746 mm. The shape of the element pattern was a cross patch in which two square patches intersected at right angles in the xy plane. Here, the only difference between the element patterns in reflection control region 5 was the element length; specifically, the element lengths were lx1 = ly1, lx2 = ly2, lx3 = ly3, and the element widths were wx1 = wx2 = wx3 = wy1 = wy2 = wy3 = 1.000 mm.

[0102] First, the reflection phase of the unit cell versus element length l was analyzed using HFSS. Fig. 17 shows the analysis results of the unit cell in the design process of Comparative Example 2, and is a diagram showing the reflection phase when the element width of the element pattern is set to wx = wy = 1.000 mm and the element length l is changed. The reflection phase changed as the element length changed.

[0103] Next, based on the analysis results of the unit cell, the element length l in each unit cell was determined so as to follow the impedance distribution of equation (7). The element lengths l were set to lx1 = ly1 = 3.390 mm, lx2 = ly2 = 3.709 mm, and lx3 = ly3 = 3.067 mm, respectively. The element length l of each element pattern determined here was set to have no dimensional error.

[0104] The reflectarray 6 has 9 x 9 unit cells arranged in the x-axis and y-axis directions, and its size in the xy plane is 60.714 mm square. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto the reflectarray 6 at θix = 33° and θiy = 0°.

[0105] In order to understand the effect of dimensional errors on the reflection characteristics, a dimensional error due to cutting was assumed, and a similar analysis was performed when the element length l of each element pattern of the reflect array 6 was increased by 0.100 mm.

[0106] 18 is an analysis result of the reflectarray 6 obtained in Comparative Example 2, showing the reflection characteristics of the reflectarray 6 with and without dimensional error in the xz plane. In the reflectarray 6 without dimensional error, the electromagnetic wave incident at θix=33° was reflected in the desired direction of θrx=0°, and the RCS was 0.22 dBsm. On the other hand, in the reflectarray 6 with dimensional error, although reflection occurred in the direction of θrx=0°, the RCS was -0.71 dBsm, and the change in RCS due to the dimensional error was -0.94 dBsm.

[0107] Example 2 A reflectarray was prepared that was similar to the reflectarray described in Comparative Example 2 except for the element pattern shape. The element pattern shape was such that only the element width of each element pattern in reflection control region 6 was different, and specifically, the element lengths of each element pattern were lx1 = lx2 = lx3 = ly1 = ly2 = ly3 = 3.250 mm, and the element widths were wx1 = wy1, wx2 = wy2, wx3 = wy3. The reflection phase of the unit cell relative to the element width w and the reflection characteristics of the reflectarray with and without dimensional error were analyzed using HFSS.

[0108] FIG. 19 shows the analysis results of a unit cell in the design process of Example 2, illustrating the reflection phase when the element length of the element pattern is lx = ly = 3.250 mm and the element width w is changed. The reflection phase changed as the element width changed. Furthermore, the slope of the reflection phase with respect to the element width was gentler than in FIG. 17 for Comparative Example 2, in which the element length was changed. For example, to change the reflection phase from 60° to −120° in Comparative Example 2, the element length l needs to be changed by 0.3 mm, from approximately 3.2 mm to 3.5 mm, whereas in Example 2, the element length w needs to be changed by 1.8 mm, from approximately 0.6 mm to 2.4 mm. This means that, given the same degree of dimensional error, Example 2, which uses the element width as a design parameter, exhibits a smaller change in the reflection phase in the unit cell, resulting in a smaller change in the reflection characteristics of the reflectarray 6.

[0109] The element widths were determined to be wx1 = wy1 = 1.582 mm, wx2 = wy2 = 2.955 mm, and wx3 = wy3 = 0.319 mm, respectively. Figure 20 shows the analysis results of the reflectarray 6 obtained in Example 2, illustrating the reflection patterns of the reflectarray 6 with and without dimensional errors in the xz plane. In the reflectarray 6 without dimensional errors, electromagnetic waves incident at θix = 33° were reflected in the desired direction of θrx = 0°, with an RCS of 0.26 dBsm. In addition, in the reflectarray 6 with dimensional errors, reflection occurred in the direction of θrx = 0°, with an RCS of 0.18 dBsm. Therefore, the change in RCS due to dimensional errors was -0.08 dBsm, and compared to the reflectarray 6 in which the element length described in Comparative Example 2 was used as a design parameter, the decrease in reflection intensity due to dimensional errors was suppressed.

[0110] (Comparative Example 3) A reflectarray 6 with a basic configuration was constructed using 0.018 mm thick copper for the element pattern 1 and ground layer 3, and 0.200 mm thick PTFE for the dielectric layer 2. However, the conductivity of copper was set to 5.8 x 10^7 siemens / m, the real part of the relative permittivity of the dielectric layer 2 was set to 2.06, and tan δ was set to 0.0007.

[0111] The operating frequency was set to 60 GHz, the target reflection characteristics were set to θix = 0°, θrx = 45°, θiy = θry = 0°, and the size Lx of reflection control region 5 in the x-axis direction was determined to be 7.065 mm using equation 1.

[0112] The number of divisions in reflection control region 5 was set to 3, and the size of the unit cell in the x-axis and y-axis directions was set to 2.355 mm. The shape of the element pattern was a cross patch in which two square patches intersected at right angles in the xy plane. Here, the only difference between the element patterns in reflection control region 5 was the element width; specifically, the element lengths were set to lx1 = ly1, lx2 = ly2, lx3 = ly3, and the element widths were set to wx1 = wx2 = wx3 = wy1 = wy2 = wy3 = 0.500 mm.

[0113] First, the reflection phase of the unit cell versus element length l was analyzed using HFSS. Fig. 21 shows the analysis results of the unit cell in the design process of Comparative Example 3, and is a diagram showing the reflection phase when the element width of the element pattern is set to wx = wy = 0.500 mm and the element length l is changed. The reflection phase changed as the element length changed.

[0114] Next, based on the analysis results of the unit cell, the element length l in each unit cell was determined so as to follow the impedance distribution of equation (7). The element lengths l were set to lx1 = ly1 = 1.844 mm, lx2 = ly2 = 1.581 mm, and lx3 = ly3 = 1.753 mm, respectively. The element length l of each element pattern determined here was assumed to have no dimensional error.

[0115] The reflectarray 6 has 27 x 27 unit cells arranged in the x-axis and y-axis directions, and its size in the xy plane is 63.585 mm square. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto the reflectarray 6 at θix = 0° and θiy = 0°.

[0116] In order to understand the effect of dimensional errors on the reflection characteristics, a dimensional error due to cutting was assumed, and a similar analysis was performed when the element length l of each element pattern of the reflect array 6 was increased by 0.100 mm.

[0117] 22 is an analysis result of the reflectarray 6 obtained in Comparative Example 3, showing the reflection characteristics of the reflectarray 6 with and without dimensional error in the xz plane. In the reflectarray 6 without dimensional error, the electromagnetic wave incident at θix=0° was reflected in the desired direction of θrx=45°, and the RCS was 7.40 dBsm. On the other hand, in the reflectarray with dimensional error, although reflection occurred in the direction of θrx=0°, the RCS was 5.12 dBsm, and the change in RCS due to the dimensional error was -2.28 dBsm.

[0118] Example 3 A reflectarray was prepared that was similar to the reflectarray described in Comparative Example 3 except for the element pattern shape. The element pattern shape was such that only the element width of each element pattern in reflection control region 5 was different, and specifically, the element lengths of each element pattern were lx1 = lx2 = lx3 = ly1 = ly2 = ly3 = 1.700 mm, and the element widths were wx1 = wy1, wx2 = wy2, wx3 = wy3. The reflection phase of the unit cell relative to the element width w and the reflection characteristics of the reflectarray 6 with and without dimensional error were analyzed using HFSS.

[0119] FIG. 23 shows the analysis results of a unit cell in the design process of Example 3, illustrating the reflection phase when the element length of the element pattern is lx = ly = 1.700 mm and the element width w is changed. The reflection phase changed as the element width changed. Furthermore, the slope of the reflection phase with respect to the element width was gentler than in FIG. 21 for Comparative Example 3, in which the element length was changed. For example, to change the reflection phase from 120° to −120° in Comparative Example 3, the element length l needs to be changed by 0.3 mm, between approximately 1.5 mm and 1.8 mm, whereas in Example 3, the element length w needs to be changed by 1.4 mm, between approximately 0.1 mm and 1.5 mm. This means that, given the same degree of dimensional error, Example 3, which uses the element width as a design parameter, exhibits a smaller change in the reflection phase in the unit cell, resulting in a smaller change in the reflection characteristics of the reflectarray 6.

[0120] The element widths were wx1 = wy1 = 1.362 mm, wx2 = wy2 = 0.142 mm, and wx3 = wy3 = 0.857 mm. Figure 24 shows the analysis results of the reflectarray 6 obtained in Example 3, illustrating the reflection patterns of the reflectarray 6 with and without dimensional errors in the xz plane. In the reflectarray 6 without dimensional errors, electromagnetic waves incident at θix = 0° were reflected in the desired θrx = 45° direction, with an RCS of 7.46 dBsm. In addition, in the reflectarray 6 with dimensional errors, reflection occurred in the θrx = 0° direction, with an RCS of 7.46 dBsm. Therefore, the change in RCS due to dimensional errors was 0.00 dBsm, and compared to the reflectarray 6 in which the element length described in Comparative Example 3 was used as a design parameter, the decrease in reflection intensity due to dimensional errors was successfully suppressed.

[0121] Comparative Example 4 A reflectarray 6 with a basic configuration was constructed using 0.002 mm thick copper for the element pattern 1 and ground layer 3, and 0.050 mm thick PET for the dielectric layer 2. However, the conductivity of copper was set to 5.8 x 10^7 siemens / m, the real part of the relative permittivity of the dielectric layer 2 was set to 3.03, and tan δ was set to 0.00476.

[0122] The operating frequency was set to 100 GHz, the target reflection characteristics were set to θix = 0°, θrx = 45°, θiy = θry = 0°, and the size Lx of reflection control region 5 in the x-axis direction was determined to be 4.240 mm using equation 1.

[0123] The number of divisions in reflection control region 5 was set to 4, and the size of the unit cell in the x-axis and y-axis directions was set to 1.060 mm. The shape of the element pattern was a cross patch in which two square patches intersected at right angles in the xy plane. Here, the only difference between the element patterns in reflection control region 5 was the element length; specifically, the element lengths were lx1=ly1, lx2=ly2, lx3=ly3, and lx4=ly4, and the element widths were wx1=wx2=wx3=wy1=wy2=wy3=0.400 mm.

[0124] First, the reflection phase of the unit cell relative to the element length l was analyzed using HFSS. Fig. 25 shows the analysis results of the unit cell in the design process of Comparative Example 4, and is a diagram showing the reflection phase when the element width l of the element pattern is changed with wx = wy = 0.400 mm. The reflection phase changed as the element length changed.

[0125] Next, based on the analysis results of the unit cell, the element length l of each unit cell was determined so as to conform to the impedance distribution of equation (7). The element lengths l were set as lx1 = ly1 = 0.929 mm, lx2 = ly2 = 0.959 mm, lx3 = ly3 = 0.862 mm, and lx4 = ly4 = 0.910 mm. The element length l of each element pattern determined here was assumed to have no dimensional error.

[0126] The reflectarray 6 has 12 x 12 unit cells arranged in the x-axis and y-axis directions, and its size in the xy plane is 12.720 mm square. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto the reflectarray 6 at θix = 0° and θiy = 0°.

[0127] In order to understand the effect of dimensional errors on the reflection characteristics, a dimensional error due to cutting was assumed, and a similar analysis was performed when the element length l of each element pattern of the reflect array 6 was increased by 0.100 mm.

[0128] 26 is an analysis result of the reflectarray 6 obtained in Comparative Example 4, showing the reflection characteristics of the reflectarray 6 with and without dimensional error in the xz plane. In the reflectarray 6 without dimensional error, the electromagnetic wave incident at θix=0° was reflected in the desired direction of θrx=45°, and the RCS was -17.5 dBsm. On the other hand, in the reflectarray 6 with dimensional error, although reflection occurred in the direction of θrx=0°, the RCS was -29.9 dBsm, and the change in RCS due to the dimensional error was -12.34 dBsm.

[0129] Example 4 A reflectarray was prepared that was similar to the reflectarray described in Comparative Example 4 except for the element pattern shape. The element pattern shape was such that only the element width of each element pattern in reflection control region 5 was different, and specifically, the element lengths of each element pattern were lx1 = lx2 = lx3 = ly1 = ly2 = ly3 = 0.900 mm, and the element widths were wx1 = wy1, wx2 = wy2, wx3 = wy3, wx4 = wy4. The reflection phase of the unit cell relative to the element width w and the reflection characteristics of the reflectarray 6 with and without dimensional error were analyzed using HFSS.

[0130] FIG. 27 shows the analysis results of a unit cell in the design process of Example 4, illustrating the reflection phase when the element length of the element pattern is lx = ly = 0.900 mm and the element width w is changed. The reflection phase changed as the element width changed. Furthermore, the slope of the reflection phase with respect to the element width was gentler than in FIG. 25 for Comparative Example 4, in which the element length was changed. For example, to change the reflection phase from 120° to −120° in Comparative Example 4, the element length l needs to be changed by 0.1 mm, between approximately 0.85 mm and 0.95 mm, whereas in Example 4, the element length w needs to be changed by 0.45 mm, between approximately 0.2 mm and 0.65 mm. This means that, given the same degree of dimensional error, Example 4, which uses the element width as a design parameter, exhibits a smaller change in the reflection phase in the unit cell, resulting in a smaller change in the reflection characteristics of the reflectarray 6.

[0131] The element widths were wx1 = wy1 = 0.532 mm, wx2 = wy2 = 0.656 mm, wx3 = wy3 = 0.173 mm, and wx4 = wy4 = 0.456 mm. Figure 28 shows the analysis results of the reflectarray 6 obtained in Example 4, illustrating the reflection patterns of the reflectarray 6 with and without dimensional errors in the xz plane. In the reflectarray 6 without dimensional errors, electromagnetic waves incident at θix = 0° were reflected in the desired θrx = 45° direction, with an RCS of -17.4 dBsm. Furthermore, in the reflectarray with dimensional errors, reflection occurred in the θrx = 0° direction, with an RCS of -19.9 dBsm. Therefore, the change in RCS due to dimensional errors was -2.51 dBsm. Compared to the reflectarray in Comparative Example 4, in which the element length was used as a design parameter, the decrease in reflection intensity due to dimensional errors was successfully suppressed.

[0132] Example 5 The reflectarray 6c was constructed by laminating a 0.098mm thick design layer 10 on the element pattern side using the method shown in Figure 2(c) with a 0.500mm gap between them, in addition to the basic configuration which used 0.018mm thick copper for the element pattern 1 and ground layer 3, and a 0.764mm thick glass / fluororesin composite for the dielectric layer 2. However, the conductivity of copper was set to 5.8 x 10^7 siemens / m, the real part of the relative permittivity of the dielectric layer 2 was set to 2.6 and tan δ was set to 0.0025, and the real part of the relative permittivity of the design layer 10 was set to 2.70 and tan δ was set to 0.0060.

[0133] The operating frequency was set to 27.2 GHz, the target reflection characteristics were set to θix = 33°, θrx = 0°, θiy = θry = 0°, and the size Lx of reflection control area 5 in the x-axis direction was determined to be 20.238 mm using equation 1.

[0134] The number of divisions in reflection control region 5 was set to 3, and the size of the unit cell in the x-axis and y-axis directions was set to 6.746 mm. The shape of the element pattern was a cross patch in which two square patches intersected at right angles in the xy plane. Here, the only difference between the element patterns in reflection control region 5 was the element width; specifically, the element lengths were lx1 = lx2 = lx3 = ly1 = ly2 = ly3 = 3.250 mm, and the element widths were wx1 = wy1 = 1.582 mm, wx2 = wy2 = 2.955 mm, and wx3 = wy3 = 0.319 mm.

[0135] The reflectarray 6c has 9 x 9 unit cells arranged in the x-axis and y-axis directions, and its size in the xy plane is 60.714 mm square. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto the reflectarray 6c at θix = 33° and θiy = 0°.

[0136] 29 is a diagram showing the reflection characteristics of the reflectarray 6c in the xz plane, which is an analysis result of the reflectarray 6c obtained in Example 5. The electromagnetic wave incident at θix=33° was reflected in the desired direction of θrx=0°, and the RCS was 0.23 dBsm.

[0137] Example 6 The reflectarray 6a was constructed by laminating a 0.060mm thick polyimide protective layer 8 using the method shown in Figure 2(a) on a basic configuration that uses 0.018mm thick copper for the element pattern 1 and ground layer 3, and a 0.764mm thick glass / fluororesin composite material for the dielectric layer 2. However, the conductivity of copper was set to 5.8 x 10^7 siemens / m, the real part of the relative dielectric constant of the dielectric layer was set to 2.6 and tan δ was set to 0.0025, and the real part of the relative dielectric constant of the protective layer 8 was set to 3.23 and tan δ was set to 0.0144.

[0138] The operating frequency was set to 27.2 GHz, the target reflection characteristics were set to θix = 33°, θrx = 0°, θiy = θry = 0°, and the size Lx of reflection control area 5 in the x-axis direction was determined to be 20.238 mm using equation 1.

[0139] The number of divisions in reflection control region 5 was set to 3, and the size of the unit cell in the x-axis and y-axis directions was set to 6.746 mm. The shape of the element pattern was a cross patch in which two square patches intersected at right angles in the xy plane. Here, the only difference between the element patterns in reflection control region 5 was the element width; specifically, the element lengths were set to lx1 = lx2 = lx3 = ly1 = ly2 = ly3 = 3.000 mm, and the element widths were set to wx1 = wy1 = 1.703 mm, wx2 = wy2 = 2.986 mm, and wx3 = wy3 = 0.075 mm.

[0140] The reflectarray 6a has 9 x 9 unit cells arranged in the x-axis and y-axis directions, and its size in the xy plane is 60.714 mm square. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto the reflectarray at θix = 33° and θiy = 0°.

[0141] 30 is a diagram showing the reflection characteristics of the reflectarray 6a in the xz plane, which is an analysis result of the reflectarray 6a obtained in Example 6. The electromagnetic wave incident at θix=33° was reflected in the desired direction of θrx=0°, and the RCS was 0.17 dBsm.

[0142] Example 7 A basic reflectarray 6 was constructed using 0.002 mm thick copper for the element pattern and ground layer, and 0.050 mm thick polystyrene for the dielectric layer. However, the conductivity of copper was set to 5.8 x 10^7 siemens / m, the real part of the relative permittivity of the dielectric layer was set to 2.47, and tan δ was set to 0.000644.

[0143] The operating frequency was set to 28 GHz, the target reflection characteristics were set to θix = 0°, θrx = 45°, θiy = θry = 0°, and the size Lx of reflection control area 5 in the x-axis direction was determined to be 15.140 mm using equation (1).

[0144] The number of divisions in reflection control region 5 was set to four, and the size of the unit cell in the x-axis and y-axis directions was set to 3.785 mm. The shape of the element pattern was a cross patch in which two square patches intersected at right angles in the xy plane. Here, the only difference between the element patterns in reflection control region 5 was the element width; specifically, the element lengths were set to lx1 = lx2 = lx3 = ly1 = ly2 = ly3 = 3.450 mm, and the element widths were set to wx1 = wy1 = 2.697 mm, wx2 = wy2 = 2.892 mm, wx3 = wy3 = 2.460 mm, and wx4 = wy4 = 2.639 mm.

[0145] The reflectarray 6 has 16 x 16 unit cells arranged in the x-axis and y-axis directions, and its size in the xy plane is 60.560 mm square. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto the reflectarray 6 at θix = 0° and θiy = 0°.

[0146] 31 is an analysis result of the reflectarray 6 obtained in Example 7, showing the reflection characteristics of the reflectarray 6 in the xz plane. The electromagnetic wave incident at θix=0° was reflected in the desired direction of θrx=45°, and the RCS was −5.91 dBsm.

[0147] (Actions and Effects) By using the element width as a design parameter, it is possible to reduce the phase change based on the design parameter and suppress the deterioration of the reflection characteristics due to dimensional errors, thereby improving the yield rate of the reflectarray.

[0148] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention.

[0149] [Other embodiments] The following are examples of possible embodiments of the present invention, but the present invention is not limited to these. (Aspect 1) A reflectarray in which at least an element pattern, a dielectric layer, and a ground layer are laminated in this order, The reflectarray includes at least one reflection control area; the reflection control region includes at least a first unit cell and a second unit cell; a first element pattern is disposed in the first unit cell; a second element pattern having a shape different from a shape of the first element pattern is disposed in the second unit cell; A reflect array, wherein the reflection characteristics of the first unit cell are different from the reflection characteristics of the second unit cell. (Aspect 2) the first element pattern and the second element pattern have an element length that is a length in a first direction and an element width that is a length in a second direction perpendicular to the first direction; a first element length that is an element length of the first element pattern and a second element length that is an element length of the second element pattern are the same length; A reflection phase of the reflection control region is set according to a first element width that is an element width of the first element pattern and a second element width that is an element width of the second element pattern. 2. The reflectarray according to embodiment 1, (Aspect 3) The reflectarray according to embodiment 1 or 2, further comprising a design layer. (Aspect 4) The reflectarray according to any one of aspects 1 to 3, further comprising a protective layer. (Aspect 5) A reflectarray device comprising the reflectarray according to any one of aspects 1 to 4 provided on a support. (Aspect 6) A design method for a reflectarray in which at least an element pattern, a dielectric layer, and a ground layer are laminated in this order, comprising: The reflectarray includes at least one reflection control area; the reflection control region includes at least a first unit cell and a second unit cell; a first element pattern is disposed in the first unit cell; a second element pattern having a shape different from a shape of the first element pattern is disposed in the second unit cell; a reflectance characteristic of the first unit cell is set to be different from a reflectance characteristic of the second unit cell; A method for designing a reflectarray, comprising: [Explanation of symbols]

[0150] 1, 11-1 n , 1d1-1d3, 1e1-1e3, 1a-1c, 1 x 1-1 x n , 1 y 1-1 y n Element pattern, 2 dielectric layers, 3 ground layer, 4, 41-4 n , 4a-4c, 4 x 1-4 x n , 4 y 1-4 y n unit cell, 5, 5a-5h, 5x, 5y reflection control area, 6, 6a-6h Reflect array, 7 functional layers, 8 protective layer, 9 Adhesive layer, 10 design layer, 11 Installation layer

Claims

1. A reflectarray in which at least an element pattern, a dielectric layer, and a ground layer are laminated in this order to generate a predetermined asymmetric reflection of an electromagnetic wave along a first direction, The reflectarray includes at least one reflection control area, the reflection control region includes n (n is an integer of 2 or more) unit cells divided at equal intervals in the first direction, an m-th element pattern arranged in an m-th unit cell (m is an integer of 1 to n) has a different shape from a p-th element pattern arranged in a p-th unit cell (p is an integer of 1 to n but not including m); the reflective properties of the m unit cell are different from the reflective properties of the p unit cell; where λ is a wavelength at an operating frequency of the reflectarray, the ground layer has a mesh shape with a line spacing of 0.5×λ or less and 0.001×λ or more, The operating frequency is 27.2 GHz or more and 100 GHz or less. A reflect array characterized by:

2. the mth element pattern and the pth element pattern have an element length that is a length in the first direction and an element width that is a length in a second direction perpendicular to the first direction, an m-th element length, which is an element length of the m-th element pattern, and a p-th element length, which is an element length of the p-th element pattern, are the same length; The reflection phase of the reflection control region is set according to the mth element width, which is the element width of the mth element pattern, and the pth element width, which is the element width of the pth element pattern. The reflect array according to claim 1 .

3. The reflect array according to claim 1 , further comprising a design layer.

4. The reflect array according to claim 1 , further comprising a protective layer.

5. A reflectarray device comprising the reflectarray according to claim 1 provided on a support.

6. A design method for a reflectarray that generates a predetermined asymmetric reflection of an electromagnetic wave along a first direction by stacking at least an element pattern, a dielectric layer, and a ground layer in this order, comprising: The reflectarray includes at least one reflection control area, the reflection control region includes n (n is an integer of 2 or more) unit cells divided at equal intervals in a first direction, an m-th element pattern arranged in an m-th unit cell (m is an integer of 1 to n) has a different shape from a p-th element pattern arranged in a p-th unit cell (p is an integer of 1 to n but not including m); the reflective properties of the m unit cell are different from the reflective properties of the p unit cell; where λ is a wavelength at an operating frequency of the reflectarray, the ground layer is set to have a mesh shape with a line spacing of 0.5×λ or less and 0.001×λ or more, The operating frequency is 27.2 GHz or more and 100 GHz or less. A method for designing a reflectarray, comprising:

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