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 communication have increased dramatically, and the frequency of electromagnetic waves has also increased accordingly. However, as the frequency of electromagnetic waves increases, they tend to travel in a more directional direction, meaning that electromagnetic waves cannot get around buildings and other obstacles, which 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, since increasing the number of base stations requires a large amount of cost, it is 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 metal ground plane provided on the bottom surface of the dielectric substrate that blocks all polarized waves from passing through the metasurface reflector, and a plurality of supercells having two or more types of cross-shaped metal resonators with different arm lengths. The supercells having the metal resonators are formed on the top surface of the dielectric substrate and are arranged with a period of a diffraction grating that reflects vertically and horizontally polarized waves of an incident wave and reflects an extraordinary wave of an electromagnetic wave at a specified frequency with a required phase.

[0004] Furthermore, Patent Document 2 discloses the following points. A reflectarray having a plurality of reflective elements arranged on a substrate, which 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, has a plurality of reflective elements each having a patch spaced apart from a ground plane, a gap between adjacent patches of reflective 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 a gap between adjacent patches of reflective 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 reflect array 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. Moreover, in neither Patent Documents 1 nor 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 reflect arrays. [Means for solving the problem]

[0007] In order to solve the above problems, one representative reflectarray of the present invention is a design method for a reflectarray including a reflection control area, comprising the steps of setting the reflection characteristics of the reflection control area, determining the size of the reflection control area, dividing the reflection control area to determine the size of a unit cell, determining the element length of an element pattern to be placed in the unit cell, deriving a reflection phase using the element width of the element pattern as a design parameter and obtaining an analysis result showing the relationship between the element width and the reflection phase, and selecting an element width that realizes a desired reflection phase or impedance based on the analysis result. Effect 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 description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a configuration of a reflect array. [Diagram 2] FIG. 2 is a diagram showing an example of an arrangement of functional layers. [Diagram 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 an arrangement of unit cells according to a direction in which asymmetric reflection is to be generated. [Diagram 5] FIG. 5 is a diagram showing an example of an arrangement of unit cells according to a direction in which asymmetric reflection is to be generated. [Figure 6] FIG. 6 is a diagram showing an example of an arrangement of unit cells according to a direction in which asymmetric reflection is to be generated. [Figure 7] FIG. 7 is a diagram showing the configuration of an element pattern. [Figure 8] FIG. 8 is a diagram showing an example of the 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 in the reflection control region. [Figure 10] FIG. 10 is a diagram showing examples of element pattern shapes and the width of each element pattern. [Figure 11] FIG. 11 is a diagram showing an example of the shape of an 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 is a diagram showing the analysis results of a 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 a diagram showing the analysis results of the reflectarray obtained in Comparative Example 1, illustrating the reflection characteristics of the reflectarray with and without dimensional error in the xz plane. [Figure 15] FIG. 15 is a diagram showing 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 error in the xz plane. [Figure 17] FIG. 17 is a diagram showing the analysis results of a 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. [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 is a diagram showing the analysis results of a unit cell in the design process of Example 2, illustrating 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 a diagram showing the analysis results of the reflectarray obtained in Example 2, and is a diagram showing the reflection patterns of the reflectarray with and without dimensional error in the xz plane. [Figure 21] FIG. 21 is a diagram showing the analysis results of a 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. [Figure 22] FIG. 22 is a diagram showing the analysis results of the reflectarray obtained in Comparative Example 3, illustrating the reflection characteristics of the reflectarray with and without dimensional error in the xz plane. [Figure 23] FIG. 23 is a diagram showing the analysis results of a 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, and is a diagram showing the reflection patterns of the reflectarray with and without dimensional error in the xz plane. [Diagram 25] FIG. 25 is a diagram showing the analysis results of a 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 the element width 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 a dimensional error in the xz plane. [Figure 27] FIG. 27 is a diagram showing the analysis results of a unit cell in the design process of Example 4, illustrating 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, and is a diagram showing the reflection patterns of the reflectarray with and without dimensional error in the xz plane. [Figure 29] FIG. 29 is a diagram showing the analysis results of the reflectarray obtained in Example 5, illustrating the reflection characteristics of the reflectarray in the xz plane. [Diagram 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. [Diagram 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 PREFERRED EMBODIMENTS

[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 the embodiment. In addition, in the description of the drawings, the same parts are denoted by the same reference numerals. When there are multiple components having the same or similar functions, they may be described by using the same reference numerals with different subscripts, or when there is no need to distinguish between these multiple components, the subscripts may be omitted. In order 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 member that reflects electromagnetic waves. It is not limited to those that perform symmetric reflection where the incident angle and the reflection angle are equal, but also includes those that perform asymmetric reflection where the incident angle and the reflection angle are different, those that scatter electromagnetic waves in multiple directions, and those that collect 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. In addition, 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 reflect array is composed of one or more reflection control regions. The reflection control region includes a layer structure formed in a direction perpendicular to the region, in addition to a two-dimensional region parallel to the electromagnetic wave incidence region. Moreover, the term "unit cell" refers to an area obtained by dividing the reflection control area. The unit cell includes one element pattern. Additionally, "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. Additionally, "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 in the x-axis direction is expressed as a positive angle (0° to 180°) when it spreads from the +z-axis direction toward the +x-axis direction, and as a negative angle (0° to -180°) when it spreads from the +z-axis direction toward the -x-axis direction. Similarly, the angle θy in the y-axis direction is expressed as a positive angle (0° to 180°) when it spreads from the +z-axis direction toward the +y-axis direction, and as a negative angle (0° to -180°) when it spreads from the +z-axis direction toward the -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 Fig. 1. Fig. 1 is a diagram showing the configuration of the reflectarray 6. The reflectarray 6 has a plurality of element patterns arranged periodically on a plane, and can set the direction of the reflected wave to a desired value. The reflectarray 6 includes at least an element pattern (element) 1, a dielectric layer 2, and a ground layer (ground 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 direction and the y-axis direction. 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 the unit cell is not specified, it is also referred to as "unit cell 4". n is a positive integer of 2 or more.) The unit cells 4 are parts obtained by dividing the reflection control region 5 at equal intervals along the x-axis direction. n is the number of divisions when dividing the reflection control region into unit cells in the x-axis direction. If the size (length) of the unit cell 4 in the x-axis direction is sx, 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 constituted by n unit cells 4 arranged in the x-axis direction, and the reflect array 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 constituted by unit cells arranged in the y-axis, or may include unit cells arranged 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. In addition, 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 in the 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, within the 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 1 is formed in unit cell 4 x 1. Element pattern 1 x 2 is formed in unit cell 4 x 2, ... Element pattern 1 x n The 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. In addition, the element pattern of the reflection control region 5 and the reflection control region 5y (shown by a broken line, element pattern 1) adjacent to the reflection control region 5 in the y-axis direction are y 1 is formed in unit cell 4 y 1. Element pattern 1 y 2 is formed in unit cell 4 y 2, ... Element pattern 1 y n The unit cell 4 formed y n The gaps between the element patterns of (including ) 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 are perpendicular to each other 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, are perpendicular to each other with a common center of gravity. 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 of 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 FIG. 2 and FIG. 3. FIG. 2 and FIG. 3 are diagrams showing an example of the layer structure of the reflectarray 6. The reflectarray 6 has a structure in which at least the element pattern 1, the dielectric layer 2, and the 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, the element pattern 1, the dielectric layer 2, and the ground layer 3, is referred to as a "basic structure". In practice, it is preferable that the reflectarray 6 has a single or multiple layers having various functionalities (hereinafter also referred to as "functional layers") stacked on 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. A layer used for a purpose other than the purpose for improving the adhesion may also be formed. Note that intermediate products generated in the manufacturing process of the reflect array 6 may be formed in layers and remain on the reflect array 6.

[0018] Examples of functional layers include a design layer that is designed to take into consideration the scenery of the area where the reflect array 6 is installed, an installation layer that enables the reflect array 6 to be easily installed 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 is laminated so as to fill the gaps between the multiple element patterns 1 as in the reflect array 6a (FIG. 2(a)), the functional layer 7 may be laminated so as to contact the upper surface of the element pattern 1 while maintaining the gaps between the multiple element patterns 1 as in the reflect array 6b (FIG. 2(b)), or the functional layer 7 may be laminated so as not to contact the upper surface of the element pattern 1 as in the reflect array 6c (FIG. 2(c)). In addition, when the reflect arrays 6a to 6c have a common configuration except for the functional layer 7, the reflect arrays 6a to 6c have different reflection characteristics. Therefore, it is also possible to change the characteristics of the reflect array by changing the lamination method of the functional layer 7.

[0020] Fig. 3 is a diagram showing another example of the arrangement of functional layers. Fig. 3 shows an example of the arrangement of functional layers, which are a protective layer 8, an adhesive layer 9, a design layer 10, and an installation layer 11. Fig. 3(a) shows a reflectarray 6d in which a protective layer 8 is laminated so as 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. Fig. 3(b) shows a reflectarray 6e in which a installation layer 11 is provided on the ground layer side via an adhesive layer 9, and a design layer 10 is provided on the element pattern 1 side with a gap therebetween.

[0021] (Reflection control area) The reflect array 6 includes at least one reflection control area. The properties of the reflect array can be changed depending on how the reflection control areas are arranged. For example, when an electromagnetic wave of a certain wavelength is incident at a certain incident angle, it is possible to give the reflect array a characteristic of reflecting in a single direction by periodically arranging reflection control areas with a common reflection direction. In addition, when an electromagnetic wave of a certain wavelength is incident at a certain incident angle, it is possible to give the reflect array a characteristic of scattering the electromagnetic wave in multiple directions by configuring a reflect array including reflection control areas with different reflection directions. In addition, it is possible to give the reflect array a characteristic of concentrating the electromagnetic wave at a specific location by shifting the reflection direction by a predetermined angle for each reflection control area. The frequency that is expected to be applied to the reflect array at the time of 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 incident angle of the electromagnetic wave incident on the reflection control area, and θrx is the x-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control area. When θix ≠ -θrx,

number

[0023] In addition, 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 incident angle of the electromagnetic wave incident on the reflection control area, and θry is the y-axis component of the reflection angle 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 FIG. 4 to FIG. 6. FIG. 4 to FIG. 6 are diagrams showing an example of the arrangement of the unit cell 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 reflect array 6f and the direction of the electromagnetic wave (reflected wave) reflected from the reflect array 6f. In other words, the arrow drawn with a thick solid line indicates the traveling direction of the wave front, the arrow toward the reflect array 6 indicates the traveling direction of the wave front of the incident wave, and the arrow away from the reflect array 6f indicates the traveling direction of the wave front of the reflected wave. FIG. 4(b) shows a plan view of the reflect array 6f seen from the z-axis direction. The relationship between (a) and (b) in FIG. 5 and FIG. 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. Since each unit cell in the reflection control region exhibits a different reflection phase, the reflected wavefront, which is the wavefront of the reflected wave generated from the reflection control region, is tilted from the reflection angle when the incident angle and the reflection angle are equal, resulting in asymmetric reflection, which is different from symmetric reflection when the incident angle and the reflection angle are equal.

[0026] In the case where the reflect array 6f is to perform asymmetric reflection only along the x-axis direction (θix ≠ -θrx as shown in FIG. 4(a)), unit cells exhibiting different reflection phases are arranged along the x-axis direction in the reflection control region 5a (FIG. 4(b)). The reflection control region 5a has a division number n=3 and has three unit cells arranged in the x-axis direction. The size Lx of the 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. In the case where 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 division number n is used for convenience, and Ly is set equal to Lx / 3.

[0027] Similarly, when it is desired to make the reflect array 6g perform asymmetric reflection only along the y-axis direction (θiy ≠ -θry as shown in FIG. 5(a)), unit cells exhibiting different reflection phases are arranged along the y-axis direction in the reflection control region 5b (FIG. 5(b)). Here, m (m is a positive integer of 2 or more) is the number of divisions when dividing the reflection control region into unit cells in the y-axis direction. The 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 the 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. Since the x-axis component of the reflection angle is a 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 made equal to Ly / 3.

[0028] FIG. 6(a) shows the relationship between the reflectarray and the electromagnetic wave, FIG. 6(a1) shows the case where the electromagnetic wave is projected onto the zx plane, and FIG. 6(a2) shows the case where the electromagnetic wave is projected onto the zy plane. When the reflectarray 6h is to perform asymmetric reflection in both the x-axis direction and the y-axis direction (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 the x-axis direction in the reflection control region 5c, and unit cells with different reflection phases are also arranged in the y-axis direction (FIG. 6(b)). The reflection control region 5c includes nine unit cells, with three unit cells arranged in the x-axis direction and three unit cells arranged in the y-axis direction. The number of divisions in the 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 the reflection control region 5c in the x-axis direction is determined by equation (1), and the size Ly of the reflection control region 5c in 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 in reflection control region 5c. gy indicates the gap in the y-axis direction between element patterns in 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 be equal. Furthermore, Gx indicates 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 indicates 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 (or x-axis direction) without changing its position in the x-axis direction (or y-axis direction), gx is equal to Gx, and gy is equal to Gy.

[0029] (Distribution of reflection phase within reflection control area, distribution of surface impedance) The distribution of the reflection phase in the reflection control area is determined to follow, for example, formulas (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 incident on 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 in 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. In addition, 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 to perform asymmetric reflection along the x-axis direction, it is preferable that formula (3) is satisfied, and when the reflection control area is to perform asymmetric reflection along the y-axis direction, it is preferable that formula (4) is satisfied. Furthermore, when it is intended that the reflection control region perform asymmetric reflection in both the x-axis direction and the y-axis direction, it is preferable that the region satisfy both formula (3) and formula (4).

number

number

[0030] Also, instead of the reflection phase, the distribution of surface impedance can be applied within the reflection control area. In that case, the distribution of surface impedance is expressed by, for example, equation (5) and equation (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. Also, the x-axis component of the incidence angle of the electromagnetic wave incident on 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, and the y-axis component is θry. Note that x1 and x2 indicate x coordinates as relative coordinates within the reflex control area, and can take the reference x = 0 at any coordinate in the reflex control area. Similarly, y1 and y2 indicate y coordinates as relative coordinates within the reflex control area, and can take the reference y = 0 at any coordinate in the reflex control area. Furthermore, k1 is the wave number of the reflected wave. j indicates an imaginary unit. When the reflection control area is intended to perform asymmetric reflection along the x-axis direction, it is preferable that formula (5) is satisfied, and when the reflection control area is intended to perform asymmetric reflection along the y-axis direction, it is preferable that formula (6) is 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) are satisfied.

number

number

[0031] Other surface impedance distributions are expressed by, for example, formula (7) and formula (8). When the reflection control area is intended to perform asymmetric reflection only along the x-axis direction, it is preferable that formula (7) is satisfied, and when the reflection control area is intended to perform asymmetric reflection only along the y-axis direction, it is preferable that formula (8) is satisfied. Furthermore, 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 formulas (7) and (8) are satisfied simultaneously.

number

number

[0032] The above 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 appropriately selected.

[0033] (element pattern) The details of the element pattern will be described with reference to Figures 1 and 7 to 10. Generally, reflectarrays change the reflection characteristics by utilizing the resonance of the element pattern. Here, since a linear or rectangular element pattern (square patch) mainly resonates the polarized waves in the direction along its long axis, it is known that when 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, the size of each unit cell and the size of the element pattern become smaller as the division numbers n and m of the reflection control area are increased. Since resonance occurs only when a certain element pattern size is satisfied for the frequency, if n and m are increased beyond a certain value, it becomes difficult to achieve asymmetric reflection at the operating frequency. On the other hand, the more n and m are increased, the more the reflection characteristics can be controlled for each smaller area, so 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 shape of two square patches perpendicular to each other in the xy plane. Here, as shown in Fig. 1, the square patch having a long side in the x-axis direction constituting the cross patch 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 having a 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 the unit cell 4n can be expressed as having element lengths lxn and lyn and element widths wxn and wyn.

[0036] Fig. 7 is a diagram showing the configuration of an element pattern. One element pattern is arranged in a unit cell. The cross patch constituting the element pattern of a unit cell 4 may be such that the position where two rectangular patches intersect 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 deformations can be appropriately selected, which can increase 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 changed within a range up to a value equal to the element length lx, and the element width wy can be changed within a range up to a value equal to the element length ly. The element width wx and the element width wy in the same element pattern may be equal or different. When the values ​​are different, the characteristics for the TE and TM polarizations can be controlled individually.

[0038] FIG. 8 is a diagram showing an example of a reflection control region. FIG. 8(a) shows an example in which the element widths wx and wy in the same element pattern are equal, and FIG. 8(b) shows an example in which the element widths wx and wy are different. In this example, n=3, the element pattern shape is composed only of two rectangular patches crossing each other at right angles, and lx and ly are equal. Meanwhile, in 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. To explain FIG. 8 in detail, in the reflection control region 5d in FIG. 8(a), the element width wx1 in the x-axis direction of the 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 the 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 the element pattern 1d3 is equal to the element width wy3 in the y-axis direction. 8(b), element width wx1 in the x-axis direction of element pattern 1e1 is smaller than element width wy1 in the y-axis direction. Element width wx2 in the x-axis direction of element pattern 1e2 is larger than element width wy2 in the y-axis direction. Element width wx3 in the x-axis direction of element pattern 1e3 is larger than element width wy3 in the y-axis direction.

[0039] In the reflection control region 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 imparted to each element pattern individually.

[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 and gx ≠ gy between the element patterns within the reflection control region, and cases where gx and gy are respectively equal and gx = gy between the element patterns within the reflection control region.

[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 the 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, the case where the element patterns are orthogonal with a common center of gravity is shown, but the present disclosure is not limited to this. 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, or a dielectric layer having a metal film formed on one or both sides of the dielectric layer by dry coating using a vapor deposition or sputtering method, plating process, wet coating, etc. Specifically, a copper-clad laminate is made by laminating copper foil onto an insulator, which is a base material such as glass cloth impregnated with a resin such as epoxy. The copper-clad laminate has a plate shape, and copper foil is laminated onto both sides of the plate-shaped insulator. The copper foil on one side is used as the element pattern 1, and the copper foil on the other side is used as the ground layer 3. The insulator corresponds to the dielectric layer 2. When metal films are formed on both sides of a 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 is a diagram showing an example of the shape of the element pattern after etching. FIG. 11(a) shows a plan view of the element pattern 1, and FIG. 11(b) to FIG. 11(d) show cross-sectional views of the element pattern 1. As shown in FIG. 11(a), the element pattern 1 is formed by orthogonally forming a square patch having an element length lx and an element width wy and a square patch having an element length ly and an element width wx. Either dry etching or wet etching may be used for the etching method. When the etching method is used, corner rounding (FIG. 11(a)) or pinholes may occur in the element pattern 1. It is also assumed that a forward taper (FIG. 11(b)), a reverse taper (FIG. 11(c)), or rounding (FIG. 11(d)) is formed in the cross-sectional view of the element pattern 1. In FIG. 11, the thickness of the element pattern 1 is t. When the etching method is used, the cross-sectional shape of the element pattern is preferably a forward taper shape with a base that spreads 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 described below.

[0045] In addition, due to the materials and manufacturing process, warping with a radius of curvature R of about 10 m may occur in the final reflectarray.

[0046] Even if the above-mentioned shape change occurs, a change in the direction of the main beam of ±5° is considered to be acceptable as a 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 a method of directly forming an element pattern or a ground layer on a dielectric layer, a printing method using letterpress printing, lithographic printing, intaglio printing, stencil printing, transfer printing, etc., or a method of masking the dielectric layer except for the element pattern portion with masking tape or a masking agent, etc., and forming the element pattern by 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 achieved by lamination, printing / coating, or extrusion molding. Examples of lamination 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 one reflectarray. In that case, when performing installation work, it is expected that there will be a shift between the reflectarrays in the x-axis direction, a shift in the y-axis direction, and a gap between the reflectarrays of about 5 mm. It is also expected that each reflectarray will be shifted in a direction rotating about 5° on the xy plane.

[0051] Even if the above changes occur, a change in the direction of the main beam of ±5° is considered to be acceptable as a reflection characteristic of the reflectarray.

[0052] (element pattern) The element pattern preferably has a surface resistance of 100Ω / □ or less. The material used for the element pattern is a conductive material such as an inorganic oxide material, a metal material, or a conductive organic material. For example, the inorganic oxide material and the metal material 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. The conductive organic material includes polythiophene derivatives, polyacetylene derivatives, polyaniline derivatives, polypyrrole derivatives, carbon nanotubes, and graphene. In particular, Cu and Al are preferable from the viewpoints of material cost, conductivity, and film formation. Also, a transparent reflect array can be produced by using ITO or a mixture (PEDOT / PSS) of polyethylenedioxythiophene (PEDOT) and polystyrenesulfonic acid (PSS). The thickness of the element pattern is, for example, 10 nm or more and 18 μm or less. From the viewpoints of flexibility, film-forming property, stability, sheet resistance value 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 of Cu or Al. Cu has excellent conductivity, so that conductor loss can be reduced. Al has low density, is lightweight, and is low cost, so that a lightweight and inexpensive reflect array can be formed. In addition, the thickness of at least one of the layers can be 1 μm or less. By making the thickness 1 μm or less, flexibility is improved, making it easier to install the reflect array on a curved surface, and making it possible to achieve weight reduction.

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

[0055] When the element pattern is in the form of a mesh, 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, the 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 a roll-to-roll production process.

[0058] When the element pattern is formed using a thin film, the thickness is preferably 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] In addition, in order to increase the reflection efficiency of electromagnetic waves, it is also desirable to reduce 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 such as paper, glass fiber, or carbon fiber impregnated with resin.

[0061] Examples of single 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), nylon (εr =3.0-5.0), polyimide (εr=2.4-2.7), fluororesin (εr=2.0-2.6), polycarbonate (εr=2.9-8.9), polyphenylene ether (εr=2.8-8.2), polyphenylene sulfide (εr=3.2-4.6), polyvinylidene fluoride (εr=6.4-10.0), polyethylene naphthalate (εr=2.9), phenol resin (εr=3.0-12.0), cycloolefin polymer (εr=2.3-2.5), etc. are listed. Here, εr indicates the relative dielectric constant. In particular, it is preferable to use polyethylene terephthalate (PET) because it is inexpensive and has excellent versatility. The dielectric layer can be a single layer or multiple layers. The dielectric layer may be a foam obtained by foaming the above materials. As the foam, a foam with high flexibility is preferably used.

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

[0063] In addition, from the viewpoint of adjusting the dielectric constant, a mixture containing resin components or a dielectric compound and a resin component may be used, and the relative dielectric constant of the mixture can be adjusted depending on the selection of the dielectric compound and its content.

[0064] The dielectric constant of a mixture can be predicted, for example, by using the Maxwell-Garnett law. In a mixture of dielectric A with a dielectric constant εa and dielectric B with a dielectric constant εb, when the volume fraction of A is δa, the dielectric constant εm of the mixture is expressed 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 material 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 to 20, more preferably in the range of 1 to 10, and even more preferably in the range of 2 to 4. When the relative dielectric constant is within the above range, the desired reflection phase characteristics tend to be easily obtained in the reflectarray 1. In addition, the dielectric loss tangent is preferably in the range of 0.00005 to 0.01, and more preferably in the range of 0.00005 to 0.001. 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 methods such as a T-die method or an inflation method, a calendar film forming method, a solution casting method, a heat press method, etc. Also, a co-extrusion method in which a film is formed by extruding a plurality of resins in multiple layers may be used.

[0069] The thickness of the dielectric layer is appropriately selected 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, and the design of the reflect array 1 becomes difficult. On the other hand, if it is too thick, it tends to be difficult to ensure the reflection phase, to lose flexibility, and to increase the total thickness of the reflect array, 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 easy to design the reflect array if the thickness of the dielectric layer is about several μm or more and 100 μm or less.

[0070] (Ground layer) The ground layer is provided to reflect the electromagnetic waves that reach the reflect array. It is also used 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] For example, inorganic oxide materials 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. Organic materials having electrical conductivity include polythiophene derivatives, polyacetylene derivatives, polyaniline derivatives, polypyrrole derivatives, carbon nanotubes, graphene, and the like. In particular, Cu and Al are preferred from the viewpoints of material cost, electrical conductivity, and film formability. In order to reflect electromagnetic waves, it is desirable for the surface resistance of the ground layer to be 100Ω / □ or less. If this condition can be met, a transparent reflect array can also be produced by using ITO or a mixture (PEDOT / PSS) of polyethylenedioxythiophene (PEDOT) and polystyrenesulfonic acid (PSS).

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

[0073] Here, mesh refers to a state in which a conductor has a mesh-like opening (opening) on ​​its plane. When the conductor is formed in a mesh shape, the mesh may be rectangular or rhombic. When the mesh is formed in a rectangular shape, it is preferable that the mesh is square. Square meshes have good design properties. 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, making it possible to maintain the appearance after installation.

[0075] When the ground layer is in the form of a mesh, 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 of 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, surface treatment such as plating, etc. 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 of forming the ground layer 11. When an organic material is used, wet coating can be selected as the method of forming the ground layer 11. It may also 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 reflect array 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 for the element pattern.

[0079] In addition, 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 a specific frequency. For example, when a structure in which patch-shaped conductive patterns are periodically arranged is used as the ground layer, it is possible to reflect only a specific frequency, and therefore it is possible to impart a function of transmitting frequencies other than the operating frequency. In addition, when a structure in which holes are periodically arranged where no conductive material exists is used, it is possible to design a reflect array that asymmetrically reflects the operating frequency while transmitting only a specific frequency.

[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. may be used. The support preferably has a mechanism that can adjust the angle of the reflectarray up and down or left and right, and more preferably has a mechanism that moves 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 installation layer is a layer for fixing 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 be given the function of the protective layer described below.

[0084] (protective layer) For the protective layer, a film or sheet having gas barrier properties, water vapor barrier properties, water resistance, abrasion resistance, and scratch resistance may be used to prevent oxidation deterioration, physical damage, and peeling of the element pattern and 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 reflect array 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 5.8×10^7siemens / m, the real part of the relative dielectric constant 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°, and 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 of the reflection control region 5 was set to 3, and the size of the unit cell in the x-axis direction and the y-axis direction was set to 23.792 mm. The shape of the element pattern was a cross patch in which two rectangular patches were orthogonal to each other in the xy plane. Here, only the element length was different in each element pattern in the reflection control region 5, and 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=9.000 mm. In Tables 1 and 2 and in the figures and text in the following description, the unit cells included in reflection control region 5 are represented as unit cell 1, unit cell 2, ... unit cell p (p is an integer between 1 and the number of divisions n), and in unit cell p, the element length in the x-axis direction is lxp, the element length in the y-axis direction is lyp, the element width in the x-axis direction is wxp, and the element width in the y-axis direction is wyp. However, when lxp and lyp are equal, the subscripts x and y are omitted, and when wxp and wyp are equal, the subscripts x and y are omitted, and when the unit cell is not specified, the subscript p may be omitted.

[0090] First, the reflection phase of the unit cell with respect to the element length l was analyzed using finite element analysis software (HFSS) made by Ansys. FIG. 13 is a diagram showing the analysis result 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 wx=wy=9.000 mm and the element length l is changed. The reflection phase changed as the element length l changed. In FIG. 13, the element length l on the horizontal axis indicates the element length lx in the x-axis direction and the element length ly in the y-axis direction. In the following explanation, the diagram of the element length l and the reflection phase shows 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 conform to 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 be free of 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. The reflection characteristics when the reflectarray 6 is irradiated with polarized waves parallel to the y-axis at θix = -60° and θiy = 0° were analyzed using HFSS.

[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 in which 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 dimensional error in the xz plane. However, the horizontal axis of FIG. 14 is the reflection angle θrx, and the vertical axis is the RCS (radar cross section). The RCS is a value that substantially corresponds to the intensity of the reflected wave. In the reflectarray 6 without 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 dimensional error, reflection occurred in the direction of θrx=0°, but 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 similar to the reflectarray described in Comparative Example 1 except for the element pattern shape was prepared. As for the element pattern shape, only the element width of each element pattern in the 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 in the same element pattern were wx1=wy1, wx2=wy2, wx3=wy3. The reflection phase of the unit cell with respect 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 is an analysis result of a unit cell in the design process of Example 1, and is a diagram showing 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 indicates the element width wx in the x-axis direction and the element width wy in the y-axis direction. In the following description, the diagram of the element width w and the reflection phase shows the same conditions as FIG. 15. As the element width changed, the reflection phase changed. In addition, the slope of the reflection phase with respect to the element width was gentler than that of FIG. 13 of Comparative Example 1 in which the element length was changed. For example, in order to change the reflection phase from 120° to -120°, the element length l needs to be changed by 2.5 mm between approximately 13.5 mm and 16 mm in Comparative Example 1, whereas the element length w needs to be changed by 6 mm between approximately 5 mm and 11 mm in Example 1. This means that when a dimensional error of the same order 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 reflect array 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. FIG. 16 is an analysis result of the reflectarray 6 obtained in Example 1, and is a diagram showing the reflection patterns of the reflectarray 6 with and without dimensional errors in the xz plane. In the reflectarray 6 without dimensional errors, the electromagnetic wave incident at θix=-60° was reflected in the desired θrx=0° direction, and the RCS was 7.03 dBsm. Also, in the reflectarray 6 with dimensional errors, reflection occurred in the θrx=0° direction, and the RCS was 7.02 dBsm. Therefore, the change in RCS due to the dimensional error 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 the dimensional error could be suppressed.

[0098] The design method will now be described in detail. What will be described here is a design method 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, the target reflection characteristics (operating frequency, incident angle, and reflection angle) are set. (Step 2) Next, the sizes Lx and Ly of the reflection control area are determined using equations (1) and (2). When asymmetric reflection is required only in the x-axis direction, Lx is determined using equation (1) and Ly is set to an arbitrary size. When asymmetric reflection is required only in the y-axis direction, Ly is determined using equation (2) and Lx is set to an arbitrary size. (Step 3) Next, the size of the reflection control area Lx is divided into n, and Ly is divided into m. The size of the unit cell is determined. (Step 4) Next, the element lengths lx and ly of the element patterns are determined within the range that fits 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 as a result. (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 area is calculated using equations (3) to (8), and the element width w for realizing 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 area 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 as to further increase the RCS at the target reflection angle and to reduce the RCS at angles other than the target angle.

[0099] Comparative Example 2 A reflect array 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 5.8×10^7siemens / m, the real part of the relative dielectric constant 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 the reflection control region 5 in the x-axis direction was determined to be 20.238 mm using equation (1).

[0101] The number of divisions of the reflection control region 6 was set to 3, and the size of the unit cell in the x-axis direction and the y-axis direction was set to 6.746 mm. The shape of the element pattern was a cross patch in which two square patches were orthogonal to each other in the xy plane. Here, the element patterns in the reflection control region 5 differed only in element length, and 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=1.000 mm.

[0102] First, the reflection phase of the unit cell with respect to the 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 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 conform to 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 be free of 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. The reflection characteristics when the reflectarray 6 is irradiated with polarized waves parallel to the y-axis at θix = 33° and θiy = 0° were analyzed using HFSS.

[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 in which 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, and is a diagram 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 similar to the reflectarray described in Comparative Example 2 was prepared except for the element pattern shape. The element pattern shape was such that only the element width of each element pattern in the reflection control region 6 was different, specifically, the element length of each element pattern was lx1=lx2=lx3=ly1=ly2=ly3=3.250 mm, and the element widths were wx1=wy1, wx2=wy2, and 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 is an analysis result of a unit cell in the design process of Example 2, and is a diagram showing 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. In addition, the slope of the reflection phase with respect to the element width was gentler than that of FIG. 17 of Comparative Example 2 in which the element length was changed. For example, in order to change the reflection phase from 60° to -120°, the element length l needs to be changed by 0.3 mm between approximately 3.2 mm and 3.5 mm in Comparative Example 2, whereas the element length w needs to be changed by 1.8 mm between approximately 0.6 mm and 2.4 mm in Example 2. This means that when the same degree of dimensional error occurs, the change in the reflection phase in the unit cell is smaller in Example 2 using the element width as a design parameter, and as a result, the change in the reflection characteristics of the reflect array 6 is smaller.

[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. FIG. 20 is an analysis result of the reflectarray 6 obtained in Example 2, and is a diagram showing the reflection pattern of the reflectarray 6 with / 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 θrx=0° direction, and the RCS was 0.26 dBsm. Also, in the reflectarray 6 with dimensional error, reflection occurred in the θrx=0° direction, and the RCS was 0.18 dBsm. Therefore, the change in RCS due to the dimensional error was -0.08 dBsm, and compared with 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 the dimensional error could be suppressed.

[0110] Comparative Example 3 A reflect array 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 5.8×10^7 siemens / m, the real part of the relative dielectric constant 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 the reflection control region 5 in the x-axis direction was determined to be 7.065 mm using Equation 1.

[0112] The number of divisions of reflection control region 5 was set to 3, and the size of the unit cell in the x-axis direction and the y-axis direction was set to 2.355 mm. The shape of the element pattern was a cross patch in which two rectangular patches were orthogonal to each other in the xy plane. Here, the element patterns in reflection control region 5 differed only in element width, and 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 with respect to the 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 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 conform to 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 set to be free of 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. The reflection characteristics when the reflectarray 6 is irradiated with polarized waves parallel to the y-axis at θix = 0° and θiy = 0° were analyzed using HFSS.

[0116] In order to grasp the effect of dimensional errors on the reflection characteristics, dimensional errors due to cutting were assumed and a similar analysis was performed in which 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, and is a diagram 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 similar to the reflectarray described in Comparative Example 3 was prepared except for the element pattern shape. The element pattern shape was such that only the element width of each element pattern in the reflection control region 5 was different, specifically, the element length of each element pattern was lx1=lx2=lx3=ly1=ly2=ly3=1.700 mm, and the element widths were wx1=wy1, wx2=wy2, and 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 a dimensional error were analyzed using HFSS.

[0119] FIG. 23 is an analysis result of a unit cell in the design process of Example 3, and is a diagram showing 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. In addition, the slope of the reflection phase with respect to the element width was gentler than that of Comparative Example 3 in FIG. 21 in which the element length was changed. For example, in order to change the reflection phase from 120° to −120°, the element length l needs to be changed by 0.3 mm between approximately 1.5 mm and 1.8 mm in Comparative Example 3, whereas the element length w needs to be changed by 1.4 mm between approximately 0.1 mm and 1.5 mm in Example 3. This means that when the same degree of dimensional error occurs, the change in the reflection phase in the unit cell is smaller in Example 3 using the element width as a design parameter, and as a result, the change in the reflection characteristics of the reflect array 6 is smaller.

[0120] The element widths were wx1=wy1=1.362 mm, wx2=wy2=0.142 mm, and wx3=wy3=0.857 mm. FIG. 24 is an analysis result of the reflectarray 6 obtained in Example 3, and is a diagram showing the reflection patterns of the reflectarray 6 with and without dimensional errors in the xz plane. In the reflectarray 6 without dimensional errors, the electromagnetic wave incident at θix=0° was reflected in the desired θrx=45° direction, and the RCS was 7.46 dBsm. In the reflectarray 6 with dimensional errors, reflection occurred in the θrx=0° direction, and the RCS was 7.46 dBsm. Therefore, the change in RCS due to the dimensional error 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 the dimensional error could be 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 5.8×10^7 siemens / m, the real part of the relative dielectric constant 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°, and θiy = θry = 0°, and the size Lx of the reflection control region 5 in the x-axis direction was determined to be 4.240 mm using Equation 1.

[0123] The number of divisions of the reflection control region 5 was set to 4, and the size of the unit cell in the x-axis direction and the y-axis direction was set to 1.060 mm. The shape of the element pattern was a cross patch in which two square patches were orthogonal to each other in the xy plane. Here, the element patterns in the reflection control region 5 differed only in element length, and 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 with respect 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 the element width 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 in 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, respectively. The element length l of each element pattern determined here was set to be free of 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. The reflection characteristics when the reflectarray 6 is irradiated with polarized waves parallel to the y-axis at θix = 0° and θiy = 0° were analyzed using HFSS.

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

[0130] FIG. 27 is an analysis result of a unit cell in the design process of Example 4, and is a diagram showing 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. In addition, the slope of the reflection phase with respect to the element width was gentler than that of Comparative Example 4 in FIG. 25 in which the element length was changed. For example, in order to change the reflection phase from 120° to −120°, the element length l needs to be changed by 0.1 mm between approximately 0.85 mm and 0.95 mm in Comparative Example 4, whereas the element length w needs to be changed by 0.45 mm between approximately 0.2 mm and 0.65 mm in Example 4. This means that when the same degree of dimensional error occurs, the change in the reflection phase in the unit cell is smaller in Example 4 using the element width as a design parameter, and as a result, the change in the reflection characteristics of the reflect array 6 is smaller.

[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. FIG. 28 is an analysis result of the reflectarray 6 obtained in Example 4, and is a diagram showing the reflection patterns of the reflectarray 6 with and without dimensional errors in the xz plane. In the reflectarray 6 without dimensional errors, the electromagnetic wave incident at θix=0° was reflected in the desired θrx=45° direction, and the RCS was −17.4 dBsm. Also, in the reflectarray with dimensional errors, reflection occurred in the θrx=0° direction, and the RCS was −19.9 dBsm. Therefore, the change in RCS due to the dimensional error was −2.51 dBsm, and compared to the reflectarray in which the element length described in Comparative Example 4 was used as a design parameter, the decrease in reflection intensity due to the dimensional error could be suppressed.

[0132] Example 5 The reflect array 6c was constructed by laminating a design layer 10 of 0.098 mm thickness using the method of Fig. 2(c) on the element pattern side with a gap of 0.500 mm from the basic configuration 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. The conductivity of copper was set to 5.8×10^7 siemens / m, the real part of the relative dielectric constant of the dielectric layer 2 was set to 2.6, tan δ was set to 0.0025, and the real part of the relative dielectric constant of the design layer 10 was set to 2.70, 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 the reflection control area 5 in the x-axis direction was determined to be 20.238 mm using Equation 1.

[0134] The number of divisions of the reflection control region 5 was set to 3, and the size of the unit cell in the x-axis direction and the y-axis direction was set to 6.746 mm. The shape of the element pattern was a cross patch in which two rectangular patches were orthogonal to each other in the xy plane. Here, the element patterns in the reflection control region 5 differed only in element width, and specifically, the element lengths were set to lx1=lx2=lx3=ly1=ly2=ly3=3.250 mm, and the element widths were set to 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. The reflection characteristics when the reflectarray 6c is irradiated with polarized waves parallel to the y-axis at θix = 33° and θiy = 0° were analyzed using HFSS.

[0136] 29 is a diagram showing the analysis result of the reflect array 6c obtained in Example 5, which is a diagram showing the reflection characteristics of the reflect array 6c in the xz plane. 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 reflect array 6a was constructed by laminating a 0.060mm thick polyimide-based protective layer 8 using the method of Fig. 2(a) on the basic configuration using 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 5.8×10^7siemens / m, the real part of the relative dielectric constant of the dielectric layer was set to 2.6, 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, 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 the reflection control area 5 in the x-axis direction was determined to be 20.238 mm using Equation 1.

[0139] The number of divisions of the reflection control region 5 was set to 3, and the size of the unit cell in the x-axis direction and the y-axis direction was set to 6.746 mm. The shape of the element pattern was a cross patch in which two rectangular patches were orthogonal to each other in the xy plane. Here, the element patterns in the reflection control region 5 differed only in element width, and 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. The reflection characteristics when the reflectarray is irradiated with polarized waves parallel to the y-axis at θix = 33° and θiy = 0° were analyzed using HFSS.

[0141] 30 is an analysis result of the reflect array 6a obtained in Example 6, which is a diagram showing the reflection characteristics of the reflect array 6a in the xz plane. 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 reflectarray 6 with a basic configuration 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 5.8×10^7 siemens / m, the real part of the relative dielectric constant 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°, and θiy = θry = 0°, and the size Lx of the reflection control region 5 in the x-axis direction was determined to be 15.140 mm using equation (1).

[0144] The number of divisions of the reflection control region 5 was set to 4, and the size of the unit cell in the x-axis direction and the y-axis direction was set to 3.785 mm. The shape of the element pattern was a cross patch in which two rectangular patches were orthogonal to each other in the xy plane. Here, the element patterns in the reflection control region 5 differed only in element width, and 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. The reflection characteristics when polarized waves parallel to the y-axis are irradiated onto the reflectarray 6 at θix = 0° and θiy = 0° were analyzed using HFSS.

[0146] 31 is an analysis result of the reflect array 6 obtained in Example 7, which is a diagram showing the reflection characteristics of the reflect array 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] (Action and effect) By using the element width as a design parameter, the phase change based on the design parameter can be reduced, and the deterioration of the reflection characteristics due to the dimensional error can be suppressed. As a result, the yield rate of the reflect array can be improved.

[0148] Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present invention.

[0149] [Other embodiments] The following are some possible embodiments of the present invention, but the present invention is not limited to these. (Aspect 1) A reflect array in which at least an element pattern, a dielectric layer, and a ground layer are laminated in this order, The reflect array 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 a reflection characteristic of the first unit cell is different from a reflection characteristic 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 reflect array according to embodiment 1, (Aspect 3) The reflect array according to embodiment 1 or 2, further comprising a design layer. (Aspect 4) The reflect array according to any one of embodiments 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 method for designing a reflectarray in which at least an element pattern, a dielectric layer, and a ground layer are laminated in this order, comprising: The reflect array 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 reflect array comprising the steps of: [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 method for designing a reflectarray including a reflection control region, comprising: setting a reflection characteristic of the reflection control area; determining a size of the reflectance control area; Dividing the reflection control area to determine a size of a unit cell; determining an element length of an element pattern to be disposed in the unit cell; Deriving a reflection phase using an element width of the element pattern as a design parameter, and acquiring an analysis result showing a relationship between the element width and the reflection phase; and selecting an element width that realizes a desired reflection phase or impedance based on the analysis result. A method for designing a reflect array comprising the steps of:

2. In the selecting step, a plurality of element widths are selected; In the step of determining the size of the unit cell, the reflection control area is divided into the plurality of unit cells. The method for designing a reflect array according to claim 1 .

3. forming the reflectarray and analyzing the reflection characteristics of the formed reflectarray; and fine-tuning the element width based on the analysis result. The method for designing a reflect array according to claim 2 .

4. In the step of determining the size of the reflection control area, A size Lx of the reflection control area in the x-axis direction is determined by Equation (1) when θix≠−θrx, where λ is the wavelength of the operating frequency, θix is ​​the x-axis component of the incident angle of the electromagnetic wave incident on the reflection control area, and θrx is the x-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control area, Furthermore, the size Ly of the reflection control area in the y-axis direction is determined by Equation (2) when θiy≠−θry, where θiy is the y-axis component of the incident angle of the electromagnetic wave incident on the reflection control area and θry is the y-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control area. The method for designing a reflect array according to claim 1 . [0010] [0025]

5. In the step of determining a size of the unit cell, The size of the unit cell is determined by dividing Lx by n (n is a positive integer of 2 or more) and dividing Ly by m (m is a positive integer of 2 or more). The method for designing a reflect array according to claim 4 .

6. In the step of selecting an element width, The wavelength of the operating frequency is λ (m), the x-axis component of the incident angle of the electromagnetic wave incident on 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, and the y-axis component is θry, Let the reflection phases at arbitrary coordinates x1, x2 parallel to the x-axis in the reflection control area be φx1, φx2, respectively, the distance between the coordinates x1 and x2 be dx, the reflection phase difference between φx1, φx2 be Δφx, the reflection phases at arbitrary coordinates y1, y2 parallel to the y-axis be φy1, φy2, respectively, the distance between the coordinates y1 and y2 be dy, and the reflection phase difference between φy1, φy2 be Δφy, Satisfying formula (3) or formula (4) The method for designing a reflect array according to claim 1 . [0030] [0045]

7. In the step of selecting an element width, Zsx is a surface impedance distribution parallel to the x-axis direction of the reflection control area, Zsy is a surface impedance distribution parallel to the y-axis direction of the reflection control area, and η1 is the impedance of the incident wave, The x-axis component of the incident angle of the electromagnetic wave incident on 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, and the y-axis component is θry, When k1 is the wave number of the reflected wave and j is the imaginary unit, Satisfying formula (5) or formula (6) The method for designing a reflect array according to claim 1 . [0050] [006]

8. In the step of selecting an element width, Zsx is a surface impedance distribution parallel to the x-axis direction of the reflection control area, Zsy is a surface impedance distribution parallel to the y-axis direction of the reflection control area, and η1 is the impedance of the incident wave, The x-axis component of the incident angle of the electromagnetic wave incident on 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, and the y-axis component is θry, When k1 is the wave number of the reflected wave and j is the imaginary unit, Satisfying formula (7) or formula (8) The method for designing a reflect array according to claim 1 . [0070] [0080]

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