Reflectarray, reflectarray device, and design method of reflectarray

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 Art

[0002] With the progress of digitalization in society, the data communication speed in wireless communication has improved dramatically, and the frequency of electromagnetic waves has increased accordingly. However, since electromagnetic waves become more rectilinear as the frequency increases, electromagnetic waves do not penetrate into the shadows of buildings, etc., and a dead zone where communication is impossible is likely to occur. For these reasons, in order to realize 5G / 6G communication 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 quickly increase the number of base stations. In recent years, technologies for controlling the direction of electromagnetic waves have attracted attention in order to solve these problems.

[0003] Among such 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 layer provided on the bottom surface of the dielectric substrate that does not transmit the metasurface reflector for all polarization directions, and a plurality of supercells having two or more types of cross-shaped metal resonators with different arm lengths. The supercells having metal resonators are formed on the upper surface of the dielectric substrate, reflect the vertical polarization wave and the horizontal polarization wave of the incident wave, and are arranged at the diffraction grating period that anomalously reflects electromagnetic waves at a required phase at a predetermined frequency.

[0004] Further, Patent Document 2 discloses the following points. A reflectarray in which a plurality of reflecting elements are arranged on a substrate and reflect a first polarization having an electric field component parallel to the surface of the substrate and a second polarization having an electric field component perpendicular to the surface in first and second desired directions, respectively, wherein each of the plurality of reflecting elements has a patch provided at a distance from a ground plane, and a gap between patches of reflecting elements adjacent in a first axial direction is set to a value according to the location of the gap so that the first polarization is reflected with a predetermined reflection phase, and a gap between patches of reflecting elements adjacent in a second axial direction perpendicular to the first axis is set to a value according to the location of the gap so that the second polarization is reflected with a predetermined reflection phase.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In a reflectarray having an element pattern including a cross shape, when a dimensional error occurs in the element pattern, the reflection phase in each region tends to change greatly from the designed value, and the reflection intensity in the desired direction may decrease. For this reason, there is a problem that it is difficult to increase the yield rate of the reflectarray. Also, in neither Patent Document 1 nor 2 has sufficient consideration been given to the method of setting design parameters. Therefore, an object of the present invention is to provide a technique for improving the yield rate of a reflectarray.

Means for Solving the Problems

[0007] To solve the above problems, one typical reflective array of the present invention is a reflective array in which at least an element pattern, a dielectric layer, and a ground layer are laminated in this order to generate a predetermined asymmetric reflection of electromagnetic waves along a first direction, the reflective array includes at least one reflection control region, the reflection control region includes n (n is an integer of 2 or more) unit cells equally divided in the first direction, and the m-th (m is an integer of 1 or more and n or less) element pattern arranged in the m-th unit cell has a different shape from the p-th (p is an integer of 1 or more and n or less and different from m) element pattern arranged in the p-th unit cell, and the reflection characteristics in the m-th unit cell are different from the reflection characteristics in the p-th unit cell.

Effect of the Invention

[0008] According to the present invention, it is possible to provide a technique for improving the yield rate of a reflective array. Problems, configurations, and effects other than those described above will be clarified by the description in the embodiments for carrying out the following invention.

Brief Description of the Drawings

[0009]

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DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited by this embodiment. Also, in the description of the drawings, the same parts are denoted by the same reference numerals. When there are a plurality of components having the same or similar functions, they may be described with different subscripts attached to the same reference numeral. Also, when it is not necessary to distinguish these plurality of components, the subscripts may be omitted in the description. The positions, sizes, shapes, ranges, etc. of the respective components shown in the drawings may not represent the actual positions, sizes, shapes, ranges, etc. in order to facilitate understanding of the invention. For this reason, the present disclosure is not necessarily limited to the positions, sizes, shapes, ranges, etc. disclosed in the drawings.

[0011] (Explanation of Terms) In the present disclosure, the "reflect array (electromagnetic wave reflector)" is a member that reflects electromagnetic waves. It includes not only those that cause symmetric reflection where the incident angle and the reflection angle are equal, but also those that cause asymmetric reflection where the incident angle and the reflection angle are different, those that scatter electromagnetic waves in a plurality of directions, and those that collect electromagnetic waves at a specific location. In the following description, an xyz coordinate system is applied, and it is assumed that the reflect array is arranged on the xy plane. Also, the "reflection control region" refers to a part of the region constituting the reflect array. The reflection control region is the smallest region that can reflect the electromagnetic waves incident on that region in a predetermined direction. The reflectarray is configured by combining one or more reflection control regions. The reflection control region shall include, in addition to a two-dimensional region in which electromagnetic waves are in a direction parallel to the incident region, a layer structure formed in a direction perpendicular to the region. Also, the "unit cell" refers to a region obtained by dividing the reflection control region. One element pattern is included in the unit cell. Also, "θi" represents the incident angle of the incident wave. Let the incident angle in the x-axis direction be θix and the incident angle in the y-axis direction be θiy. Also, "θr" represents the reflection angle of the reflected wave. Let the reflection angle in the x-axis direction be θrx and the reflection angle in the y-axis direction be θry. Also, for the angle θx in the x-axis direction, when it spreads in the direction from the +z-axis direction to the +x-axis direction, it is represented by a positive angle (from 0° to 180°), and when it spreads in the direction from the +z-axis direction to the -x-axis direction, it is represented by a negative angle (from 0° to -180°). Similarly, for the angle θy in the y-axis direction, when it spreads in the direction from the +z-axis direction to the +y-axis direction, it is represented by a positive angle (from 0° to 180°), and when it spreads in the direction from the +z-axis direction to the -y-axis direction, it is represented by a negative angle (from 0° to -180°). Also, regarding the element length, 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. Also, regarding the element width, 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] (Configuration of Reflectarray) Referring to FIG. 1, the configuration of the reflectarray and the configuration of the element pattern will be described. FIG. 1 is a diagram showing the configuration of the reflectarray 6. The reflectarray 6 can arrange a plurality of element patterns periodically in a plane and make the direction of the reflected wave a desired value. The reflectarray 6 includes at least an element pattern (element) 1, a dielectric layer 2, and a ground layer (ground plane) 3. In the following description, an xyz coordinate system is applied, and the reflectarray 6 is arranged on the xy plane.

[0013] The reflect array 6 in FIG. 1 causes a predetermined asymmetric reflection of electromagnetic waves along the x-axis. The reflect array 6 in FIG. 1 has a configuration in which a plurality of reflection control regions 5 identical to the reflection control region 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 representing the reflection control region included in the reflect array 6. In the reflection control region 5, there are unit cells 4 1 , 4 2 , 4 3 , … 4 n (hereinafter, when referring to the unit cell without specifying it, it is also referred to as "unit cell 4". n is a positive integer of 2 or more.) are included. The unit cell 4 is a part obtained by equally dividing the reflection control region 5 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. When the size (length) of the unit cell 4 in the x-axis direction is sx and the size in the y-axis direction is sy, and the size of the reflection control region 5 in the x-axis direction is Lx and the size in the y-axis direction is Ly, then sx = Lx / n and sy = Ly. In FIG. 1, the reflection control region 5 is composed of n unit cells 4 arranged in the x-axis direction, and the reflect array 6 is shown to include a plurality of reflection control regions 5, but the present disclosure is not limited to such a configuration. The reflection control region may be composed of unit cells arranged along the y-axis, or may be a configuration including unit cells arranged along the x-axis and the y-axis. The configuration of the reflection control region will be described later.

[0014] (Configuration of the element pattern) An element pattern is formed on the surface of the unit cell 4 facing the +z-axis direction. Using the number of divisions n, the unit cell 4 1 , unit cell 4 2 , … unit cell 4 n are represented. In the unit cell 4 1 , an element pattern 1 1 is formed. In the unit cell 4 2 , an element pattern 1 2 is formed. In the unit cell 4 3 , an element pattern 1 3 is formed. In the unit cell 4 n , an element pattern 1 n is formed. Also, within the reflection control region and between regions adjacent to the same reflection control region, the element patterns are arranged at equal intervals. Specifically, for each element pattern within the region of the reflection control region 5, when the size of the closest distance between adjacent element patterns in the x-axis direction (hereinafter also referred to as "gap") is gx, within the region of the reflection control region 5, the element pattern 1 1 from 1 n is arranged at equal intervals of gx. Also, the element pattern 1 n of the reflection control region 5 and the reflection control region 5x adjacent to the reflection control region 5 in the x-axis direction (shown by a dashed line, the unit cell 4 x 1 formed with the element pattern 1 x 1 , the element pattern 1 x 2 formed with the unit cell 4 x 2 , … the unit cell 4 x n formed with the element pattern 1 x n is included. ) If the gap between the element patterns 1 x 1 is Gx, in FIG. 1, Gx and gx are equal. In addition, for the element pattern of the reflection control region 5 and the reflection control region 5y adjacent to the reflection control region 5 in the y-axis direction (shown by a dashed line, the unit cell 4 y 1 formed with the element pattern 1 y 1 , the element pattern 1 y 2 formed with the unit cell 4 y 2 , … the unit cell 4 y n formed with the element pattern 1 y n is included. ) The gap between the element patterns is uniform in FIG. 1 and is shown as Gy.

[0015] Within the reflection control region, each element pattern has a slightly different shape from other element patterns. Here, the element pattern 1 1From the element pattern 1 n The shape of the element pattern shown in may be referred to as a cross patch. A cross patch refers to a shape in which two rectangular patches are orthogonal in the xy plane. Element pattern 1 1 has a rectangular 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 rectangular 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, and has a shape in which they are orthogonal with the position of the center of gravity being common. Similarly, element pattern 1 n has a rectangular patch having an element length lxn and an element width wyn, and a rectangular patch having an element length lyn and an element width wxn, and has a shape in which they are orthogonal with the position of the center of gravity being common. The method for setting the element length and the element width will be described later.

[0016] (Description of each configuration, design method) (Layer configuration) Referring to FIGS. 2 and 3, the layer configuration of the reflect array 6 will be described. FIGS. 2 and 3 are diagrams showing an example of the layer configuration of the reflect array 6. The reflect array 6 has a configuration in which at least the element pattern 1, the dielectric layer 2, and the ground layer 3 are laminated in the direction from the +z-axis direction to the -z-axis direction. In the following description, a configuration consisting of the three layers of the element pattern 1, the dielectric layer 2, and the ground layer 3 is referred to as a "basic configuration". In practical use, it is preferable to laminate one or more layers having various functions (hereinafter also referred to as "functional layers") on the element pattern 1 side or the ground layer 3 side, or both sides, of the basic configuration of the reflect array 6. In the following description, when referring to layers included in the reflect array other than the element pattern 1, the dielectric layer 2, and the ground layer 3 without specifying the type of layer, they may be referred to as "functional layers".

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

[0018] As functional layers, for example, there are a design layer with a design that takes into account the landscape of the location where the reflect array 6 is installed, an installation layer for easily installing the reflect array 6 on a support such as a wall or ceiling, a protection layer for protecting the basic configuration, 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. As for the lamination method on the element pattern 1 side, the functional layer 7 may be laminated so as to fill the gaps between a plurality of element patterns 1 like the reflect array 6a (FIG. 2(a)), or the functional layer 7 may be laminated so as to be in contact with the upper surface of the element pattern 1 while maintaining the gaps between a plurality of element patterns 1 like the reflect array 6b (FIG. 2(b)), or the functional layer 7 may be laminated so as not to be in contact with the upper surface of the element pattern 1 like the reflect array 6c (FIG. 2(c)). In addition, when the configurations excluding the functional layer 7 in the reflect arrays 6a to 6c are common, the reflect arrays 6a to 6c have different reflection characteristics respectively. 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 the functional layer. In FIG. 3, arrangement examples of a protection layer 8, an adhesive layer 9, a design layer 10, and an installation layer 11 are shown as functional layers. FIG. 3(a) shows a reflect array 6d in which the protection layer 8 is laminated so as to cover the element pattern 1 and the ground layer 3, and further, the design layer 10 is provided on the element pattern 1 side via the adhesive layer 9, and the installation layer 11 is provided on the ground layer side via the adhesive layer 9. FIG. 3(b) shows a reflect array 6e having the installation layer 11 on the ground layer side via the adhesive layer 9 and having the design layer 10 with a gap on the element pattern 1 side.

[0021] (Reflection control region) The reflect array 6 includes at least one reflection control region. By changing the arrangement of the reflection control regions, the properties of the reflect array can be altered. For example, when an electromagnetic wave of a certain wavelength is incident at a certain incident angle, by periodically arranging the reflection control regions with a common reflection direction, the reflect array can be given the property of reflecting in a single direction. Also, when an electromagnetic wave of a certain wavelength is incident at a certain incident angle, by configuring a reflect array that includes reflection control regions with different reflection directions, the property of scattering the electromagnetic wave in multiple directions can also be given. Further, by configuring such that the reflection direction is shifted by a predetermined angle for each reflection control region, the property of concentrating the electromagnetic wave at a specific location can also be given. At the design stage, the frequency planned to be applied to the reflect array is hereinafter referred to as the "operating frequency".

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

Equation

[0023] Also, the size Ly of the reflection control region in the y-axis direction is determined, for example, by Equation (2) when the y-axis component of the incident angle of the electromagnetic wave incident on the reflection control region is θiy, and the y-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control region is θry, and θiy≠-θry.

Equation

[0024] (Relationship between unit cell and reflection phase) Referring to FIGS. 4 to 6, the relationship between the unit cell and the reflection phase will be described. FIGS. 4 to 6 are diagrams showing an example of the arrangement of unit cells according to the direction in which asymmetric reflection occurs. 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 wavefront. The arrow toward the reflect array 6 indicates the traveling direction of the wavefront of the incident wave, and the arrow in the direction away from the reflect array 6f indicates the traveling direction of the wavefront of the reflected wave. Further, FIG. 4(b) shows a plan view of the reflect array 6f as viewed from the z-axis direction. The relationships of (a) and (b) in FIGS. 5 and 6 are the same as those of (a) and (b) in FIG. 4.

[0025] The unit cell has the function of reflecting the incident electromagnetic wave with a predetermined phase difference. In the reflection control region, since each unit cell shows a different reflection phase, the reflected wavefront, which is the wavefront of the reflected wave generated from the reflection control region, is inclined from the reflection angle when the incident angle and the reflection angle are equal, and an asymmetric reflection different from the symmetric reflection in which the incident angle and the reflection angle are equal is realized.

[0026] When attempting to cause the reflect array 6f to perform asymmetric reflection only along the x-axis direction (θix≠-θrx as shown in FIG. 4(a)), unit cells showing different reflection phases along the x-axis direction are arranged within 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. When the y-axis component of the reflection angle is in the case of symmetric reflection (θiy=-θry) as represented by this example, Ly does not need to be determined by Equation (2) and can take any value. However, for ease of design, it is assumed that a square unit cell whose size is determined from Lx and the division number n is used for convenience, and Ly is made equal to Lx / 3.

[0027] Similarly, when attempting to cause the reflect array 6g to perform asymmetric reflection only along the y-axis direction (θiy ≠ -θry as shown in Fig. 5(a)), unit cells showing different reflection phases along the y-axis direction within the reflection control region 5b are arranged (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 a division number m = 3 and has three unit cells arranged in the y-axis direction. The size Ly in the y-axis direction of the reflection control region 5b 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 symmetric reflection, it is not necessary for Lx to be determined by Equation (1) and can take any value. However, for ease of design, it is assumed that a square unit cell whose size is determined from Ly and the division number 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 attempting to cause the reflectarray 6h to perform asymmetric reflection in either the x-axis direction or the y-axis direction (θix≠-θrx as shown in Fig. 6(a1) and θiy≠-θry as shown in Fig. 6(a2)), within the reflection control region 5c, unit cells with different reflection phases are arranged in the x-axis direction, 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 in the x-axis direction of the reflection control region 5c is determined by Equation (1), and the size Ly in the y-axis direction is determined by Equation (2). The size of the unit cell in the x-axis direction is determined from Lx and n and is Lx / 3. The size of the unit cell in the y-axis direction is determined from Ly and m and is Ly / 3. Both the x-axis component and the y-axis component of the incident wave are asymmetrically reflected. For this reason, the x-axis component of the propagation direction of the reflected wavefront is different from the x-axis component of the propagation direction of the incident wavefront, and the y-axis component of the propagation direction of the reflected wavefront is different from the y-axis component of the propagation direction of the incident wavefront (Fig. 6(a)). Note that gx represents the gap in the x-axis direction between the element patterns within the region of the reflection control region 5c. gy represents the gap in the y-axis direction between the element patterns within the region of the reflection control region 5c. The intervals gx between the element patterns in the x-axis direction are equal, and the intervals gy between the element patterns in the y-axis direction are equal. Although cases where gx and gy are different are shown, gx and gy may also be equal. Also, Gx represents the gap between the element pattern of the reflection control region 5c and the element pattern of the reflection control region adjacent to the reflection control region 5c in the x-axis direction. Gy represents the gap between the element pattern of the reflection control region 5c and the element pattern of the reflection control region adjacent to the reflection control region 5c in the y-axis direction. When a reflection control region identical to the reflection control region 5c is adjacent in the y-axis direction (or x-axis direction) without changing its position in the x-axis direction (or y-axis direction), gx and Gx are equal, and gy and Gy are equal.

[0029] (Distribution of reflection phase and distribution of surface impedance within the reflection control region) The distribution of the reflection phase within the reflection control region is determined, for example, according to equations (3) and (4). Here, the wavelength of the operating frequency is λ (m), the x-axis component of the incident angle of the electromagnetic wave incident on the reflection control region 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 region is θrx, the y-axis component is θry, the reflection phases at arbitrary coordinates x1 and x2 parallel to the x-axis within the reflection control region are φx1 and φx2 respectively, the distance between the coordinates x1 and x2 is dx, and the reflection phase difference between Φx1 and Φx2 is ΔΦx. Also, the reflection phases at arbitrary coordinates y1 and y2 parallel to the y-axis are φy1 and φy2 respectively. When attempting to cause asymmetric reflection along the x-axis direction in the reflection control region, it is preferable to satisfy equation (3). When attempting to cause asymmetric reflection along the y-axis direction in the reflection control region, it is preferable to satisfy equation (4). Also, when attempting to cause asymmetric reflection in both the x-axis direction and the y-axis direction in the reflection control region, it is preferable to satisfy either equation (3) or equation (4). [Number] [Number]

[0030] In addition, instead of the reflection phase, the distribution of the surface impedance can also be applied within the reflection control region. In that case, the distribution of the surface impedance is represented 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 region, Zsy is the surface impedance distribution parallel to the y-axis direction of the reflection control region, and η 1 is the impedance of the incident wave. Also, let the x-axis component of the incident angle of the electromagnetic wave incident on the reflection control region be θix, the y-axis component be θiy, the x-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control region be θrx, and the y-axis component be θry. Note that x1 and x2 indicate the x-coordinates as relative coordinates within the reflection control region, and the reference x = 0 can be taken at any coordinate in the reflection control region. Similarly, y1 and y2 indicate the y-coordinates as relative coordinates within the reflection control region, and the reference y = 0 can be taken at any coordinate in the reflection control region. Also, k 1 is the wave number of the reflected wave. j represents the imaginary unit. When attempting to cause asymmetric reflection along the x-axis direction in the reflection control region, it is preferable to satisfy Equation (5). When attempting to cause asymmetric reflection along the y-axis direction in the reflection control region, it is preferable to satisfy Equation (6). Also, when the reflection control region attempts to cause asymmetric reflection in both the x-axis direction and the y-axis direction, it is preferable to satisfy either Equation (5) or Equation (6).

Number

Number

[0031] As other distributions of surface impedance, for example, they are represented by Expression (7) and Expression (8). When attempting to cause the reflection control region to perform asymmetric reflection only along the x-axis direction, it is preferable to satisfy Expression (7). When attempting to cause the reflection control region to perform asymmetric reflection only along the y-axis direction, it is preferable to satisfy Expression (8). Further, when attempting to cause the reflection control region to perform asymmetric reflection in both the x-axis direction and the y-axis direction, it is preferable to satisfy Expression (7) and Expression (8) simultaneously. [Number] [Number]

[0032] Note that Expressions (3) to (8) described above show an example of design expressions used when designing the distribution of reflection phase and the distribution of surface impedance. The present disclosure is not limited to the case of using these Expressions (3) to (8), and other design expressions can be appropriately selected.

[0033] (Element pattern) With reference to FIGS. 1 and 7 to 10, the details of the element pattern will be described. Generally, a reflectarray changes reflection characteristics by utilizing resonance by an element pattern. Here, since a linear or rectangular element pattern (square patch) mainly resonates a polarization in a direction along its major axis, it is known that when using an element pattern having a shape in which these are orthogonal, it is possible to correspond to both TE and TM polarizations.

[0034] In the reflectarray of the present disclosure, as the number of divisions n and m of the reflection control region increases, the size of each unit cell and the size of the element pattern become smaller. Since resonance occurs only when a size of a certain element pattern with respect to the frequency is satisfied, when n and m are increased beyond a certain level, it becomes difficult to realize asymmetric reflection at the operating frequency. On the other hand, as n and m increase, the reflection characteristics can be controlled for each smaller region, and thus the reflection characteristics of the reflectarray approach theoretical characteristics.

[0035] In the element pattern in the reflect array of the present disclosure, in the xy plane, the element pattern includes a cross patch in which two rectangular patches are orthogonal. Here, as shown in FIG. 1, the rectangular patch having a long side in the x-axis direction that constitutes 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 rectangular 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, it is possible to represent that the element pattern in the unit cell 4n has lxn and lyn as the element lengths and wxn and wyn as the element widths.

[0036] FIG. 7 is a diagram showing the configuration of the element pattern. One element pattern is arranged in the unit cell. The cross patch that constitutes the element pattern of the unit cell 4 may have the same position where the two rectangular patches intersect 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), unit cell 4c in FIG. 7(c)). These deformations of the cross patch can be appropriately selected, and the flexibility and expandability of the design can be enhanced.

[0037] In the present 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 from each other. The element width wx can vary within a range up to a value equal to the element length lx at maximum, and the element width wy can vary within a range up to a value equal to the element length ly at maximum. The element width wx and the element width wy within the same element pattern may be equal or different. When they are different, the characteristics for TE and TM polarized waves can be individually controlled.

[0038] FIG. 8 is a diagram showing an example of a reflection control region. FIG. 8(a) shows an example of a case where the element widths wx and wy within the same element pattern are equal, and FIG. 8(b) shows an example of a case where the element widths wx and wy are different. In this example, n = 3, the element pattern shape consists only of a shape in which two rectangular patches are orthogonal, and a case where lx and ly are equal is shown. On the other hand, within the reflection control region, the first element width wx which is the width of the element pattern in the x-axis direction and / or the second element width wy which is the width of the element pattern in the y-axis direction are different for each element pattern arranged in each unit cell. Regarding FIG. 8 in detail, in the reflection control region 5d of FIG. 8(a), the element width wx1 in the x-axis direction of the element pattern 1d 1 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 1d 2 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 1d 3 is equal to the element width wy3 in the y-axis direction. On the other hand, in the reflection control region 5e of FIG. 8(b), the element width wx1 in the x-axis direction of the element pattern 1e 1 is smaller than the element width wy1 in the y-axis direction. The element width wx2 in the x-axis direction of the element pattern 1e 2 is larger than the element width wy2 in the y-axis direction. The element width wx3 in the x-axis direction of the element pattern 1e 3 is larger than the 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 polarized waves can be individually imparted to each element pattern.

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

[0041] Regarding the gaps, there are cases where only gx is equal between the element patterns within the reflection control region, cases where only gy is equal between the element patterns within the reflection control region, cases where gx and gy are each equal and gx ≠ gy between the element patterns within the reflection control region, and cases where gx and gy are each 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 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) As the main manufacturing method of the basic structure of the reflect array, for a copper-clad laminate used for a printed circuit board or the like, or a dielectric layer having a metal film formed thereon by dry coating such as vapor deposition or sputtering, plating, or wet coating on one or both sides of the dielectric layer, an element pattern is formed by performing cutting, etching, or the like. Specifically, the copper-clad laminate is, for example, a laminate obtained by bonding a copper foil to an insulator obtained by impregnating a base material such as glass cloth with a resin such as epoxy. The copper-clad laminate has a plate-like shape, and copper foils are bonded to both sides of the plate-like insulator. One copper foil is used as the element pattern 1, and the copper foil on the other side is applied to the ground layer 3. The insulator corresponds to the dielectric layer 2. When forming metal films on both sides of the dielectric, the element pattern 1 is formed from one metal film, and the other metal film is applied to the ground layer 3. The dielectric becomes the dielectric layer 2.

[0044] FIG. 11 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 FIGS. 11(b) to 11(d) show cross-sectional views of the element pattern 1. As shown in FIG. 11(a), the element pattern 1 is formed by a 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 intersecting each other. For the etching method, either a dry etching or a wet etching method may be used. When the etching method is used, corner rounding (FIG. 11(a)) or pinholes may occur in the element pattern 1. Also, it is 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 denoted as t. When the etching method is used, the cross-sectional shape of the element pattern is preferably a forward taper shape in which the skirt spreads in the -z axis direction. By having a forward taper shape, the surface area of the element pattern increases, and it becomes possible to increase the adhesion with the functional layer when the functional layer described later is laminated.

[0045] In addition, due to the materials and manufacturing processes, the final product, the reflect array, may have a warp with a radius of curvature R of about 10 m.

[0046] Even when the above-mentioned shape change occurs, if the direction of the main beam changes by about ±5°, it shall be acceptable as the reflection characteristics of the reflect array.

[0047] In general, 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 and a ground layer on a dielectric layer. Examples of printing methods include using relief printing, lithography, intaglio printing, screen printing, transfer printing, etc., and a method of masking portions other than the element pattern portion of the dielectric layer with a masking tape, a masking agent, etc., and forming the element pattern by using dry coating, plating, painting, or spray method.

[0049] For the lamination of other layers (functional layers 7 such as protective layer 8, adhesive layer 9, design layer 10, installation layer 11, etc.) to the basic configuration, examples include bonding, printing / coating, and extrusion molding. Examples of bonding include using dry lamination, wet lamination, thermal lamination, and extrusion lamination, but are not limited thereto.

[0050] When a large-sized reflect array is required, a single reflect array may be configured by arranging multiple reflect arrays side by side. In that case, when installation work is performed, it is assumed that a displacement in the x-axis direction, a displacement in the y-axis direction, and a gap of about 5 mm between the reflect arrays will occur. In addition, it is assumed that each individual reflect array will be displaced in a direction of rotation of about 5° on the xy plane.

[0051] Even when the above-mentioned changes occur, if the direction of the main beam changes by about ±5°, it shall be acceptable as the reflection characteristics of the reflect array.

[0052] (Element pattern) The element pattern preferably has a surface resistance value of 100 Ω / square or less. As the material used for the element pattern, a conductive material such as an inorganic oxide material, a metal material, or a conductive organic material is used. For example, as the inorganic oxide material and the metal material, 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 are used. Further, nanoparticles or nanowires containing at least one of these materials may be used. Examples of the conductive organic material include polythiophene derivatives, polyacetylene derivatives, polyaniline derivatives, polypyrrole derivatives, carbon nanotubes, and graphene. Particularly from the viewpoints of material cost, conductivity, and film-forming property, Cu and Al are preferable. Also, a reflective array having transparency can be fabricated by using ITO or a mixture of polyethylenedioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT / PSS). The thickness of the element pattern is, for example, 10 nm 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 a vapor deposition method as the element pattern.

[0053] The material of the element pattern may be the same as that of the ground layer or may be a different material. For example, it is also possible that at least one of the ground layer and the element pattern is formed of Cu or Al. Since Cu has excellent conductivity, conductor loss can be reduced. Since Al has a small density, is lightweight, and has a low cost, a lightweight and inexpensive reflective array can be formed. Also, the thickness of at least one layer can be 1 μm or less. By setting it to 1 μm or less, flexibility is improved, installation on a curved surface or the like of the reflective array becomes easy, and weight reduction can be achieved.

[0054] Examples of the form of using the above materials include a continuous film, a mesh shape, and a punching shape.

[0055] When the element pattern is in a mesh shape, the line width of the mesh is preferably 5 μm or more and 30 μm or less, more preferably 6 μm or more and 15 μm or less. The line interval of the mesh is preferably 50 μm or more and 500 μm or less, more preferably 100 μm or more and 300 μm or less. Also, when the wavelength at the operating frequency is λ, the line interval 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 interval of the mesh is 0.5×λ or less, the performance can be ensured. Also, the line interval of the mesh may be 0.001×λ or more.

[0056] When the element pattern is in a mesh shape or when a transparent conductive material is used, the reflect array exhibits visible light transmissivity, making it possible to maintain the landscape after installation.

[0057] When the form of the element pattern is a thin film, it is possible to improve the flexibility of the reflect array, thereby enabling use on a curved surface and implementing a roll-to-roll production process.

[0058] When forming the element pattern using a thin film, its thickness is preferably greater than the skin depth calculated from Equation (9). However, d is the skin depth, ω is the angular frequency, μ is the magnetic permeability of the material, and σ is the conductivity of the material.

Equation

[0059] Also, in order to increase the reflection efficiency of electromagnetic waves, reducing the loss due to the element pattern can be mentioned. Therefore, the surface roughness of the element pattern is preferably small.

[0060] (Dielectric layer) In addition to a single resin, the dielectric layer may use a composite material in which paper, glass fiber, carbon fiber, etc. are impregnated with resin.

[0061] Examples of single resins include polyethylene (εr = 2.2 - 2.4), polypropylene (εr = 2.0 - 2.6), polystyrene (εr = 2.4 - 2.6), polyvinyl chloride (εr = 2.8 - 8.0), AS resin (εr = 2.6 - 3.1), ABS resin (εr = 2.4 - 4.1), polyethylene terephthalate (εr = 2.9 - 3.0), acrylic resin (εr = 2.7 - 4.5), urethane resin (εr = 4.0 - 7.1), epoxy resin (εr = 2.5 - 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), phenolic resin (εr = 3.0 - 12.0), cycloolefin polymer (εr = 2.3 - 2.5), etc. Here, εr represents the relative permittivity. In particular, from the viewpoints of low cost and excellent versatility, it is preferable to use polyethylene terephthalate (PET). Also, the dielectric layer can be a single layer or a multilayer. Further, the dielectric layer may use a foam obtained by foaming the above materials. As the foam, a highly flexible foam is preferably used.

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

[0063] In addition, from the viewpoint of permittivity adjustment, the use of a mixture containing resin components or a mixture of a dielectric compound and a resin component is also mentioned. The relative permittivity in the mixture can be adjusted according to the selection of the dielectric compound and its content.

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

Equation

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

[0066] When a dielectric having transparency is used, the reflectarray exhibits visible light transmissibility, making it possible to maintain the landscape after installation.

[0067] The relative permittivity of the dielectric layer is preferably in the range of 1 or more and 20 or less, more preferably in the range of 1 or more and 10 or less, and even more preferably in the range of 2 or more and 4 or less. When the relative permittivity is within the above range, it tends to be easy to obtain the desired reflection phase characteristics in the reflectarray 1. Also, the dielectric loss tangent is preferably in the range of 0.00005 or more and 0.01 or less, and preferably in the range of 0.00005 or more and 0.001 or less. When it is within the above range, a reflectarray 1 with less dielectric loss can be manufactured.

[0068] The dielectric layer can be formed, for example, using wet coating such as die coating, comma coating, gravure coating, melt extrusion methods such as the T-die method and the inflation method, calendar film forming method, solution casting method, hot pressing method, and the like. Also, a coextrusion method in which a plurality of resins are extruded in multiple layers to form a film may be used.

[0069] The thickness of the dielectric layer is appropriately selected according to 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 it becomes difficult to design the reflect array 1. On the other hand, if it is too thick, there is a tendency that it becomes difficult to ensure the reflection phase, the flexibility is lost, the total thickness of the reflect array becomes thick, etc., and it becomes 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, if the thickness of the dielectric layer is about several μm or more and 100 μm or less, it is easy to design the reflect array.

[0070] (Ground layer) The ground layer is provided to reflect the electromagnetic wave reaching the reflect array. It is also used to support and protect the dielectric layer. As the material of the ground layer, a conductive material such as an inorganic oxide material, a metal material, or a conductive organic material is used.

[0071] For example, as the inorganic oxide materials and metal materials, indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), tin antimonide oxide, Ag, Al, Au, Pt, Pd, Cu, Co, Cr, In, Ag-Cu, Cu-Au, Ni, etc. are used. Also, nanoparticles or nanowires containing at least one of these materials may be used. Examples of the conductive organic materials include polythiophene derivatives, polyacetylene derivatives, polyaniline derivatives, polypyrrole derivatives, carbon nanotubes, graphene, etc. Particularly from the viewpoints of material cost, conductivity, and film-forming property, Cu and Al are preferable. Also, in order to reflect electromagnetic waves, it is desirable that the surface resistance value of the ground layer is 100 Ω / sq or less. If this condition can be satisfied, a reflective array having transparency can be fabricated by using ITO, a mixture of polyethylenedioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT / PSS), etc.

[0072] Examples of the forms of using the above materials include a continuous film, a mesh shape, a punching shape, and a periodic structure.

[0073] Here, a mesh refers to a state in which a conductor has mesh-shaped through holes (openings) on its plane. When the conductor is formed in a mesh shape, the mesh openings may be square or rhombic. When forming the mesh openings in a square shape, it is preferable that the mesh openings are square. If the mesh openings are square, the design property is good. Also, a random shape by a self-assembly method may be used. By making it a random shape, moiré can be prevented. When processing the metal into a mesh shape, methods such as punching the metal plate and etching the metal plate can be adopted.

[0074] When the ground layer is in a mesh shape or when a transparent conductive material is used, the reflective array exhibits visible light transmittance and enables the landscape after installation to be maintained.

[0075] When the ground layer is in a mesh shape, the line width of the mesh is preferably 5 μm or more and 30 μm or less, more preferably 6 μm or more and 15 μm or less. The line interval of the mesh is preferably 50 μm or more and 500 μm or less, more preferably 100 μm or more and 300 μm or less. Further, the line interval 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, where λ is the wavelength at the operating frequency. If the line interval of the mesh is 0.5×λ or less, the performance can be ensured. Also, the line interval of the mesh may be 0.001×λ or more.

[0076] As a method for forming the ground layer, if a metal material is used, dry coating such as sputtering or vapor deposition, gravure coating by converting the metal material into ink, wet coating such as die coating, surface treatment such as plating, etc. can be selected. Alternatively, a rolled metal plate may be used as the ground layer. If an inorganic oxide material is used, dry coating can be selected as the method for forming the ground layer 11. If an organic material is used, wet coating can be selected as the method for forming the ground layer 11. Also, it may be formed by painting or spraying.

[0077] When the form of the ground layer is a thin film formed by plating or vapor deposition, etc., it is possible to improve the flexibility of the reflect array, thereby enabling use on a curved surface and implementing a roll-to-roll production process.

[0078] When the form of the ground layer is a thin film, its thickness is preferably larger than the skin depth calculated from Equation (9) similar to the element pattern.

[0079] Also, in order to increase the reflection efficiency of electromagnetic waves, reducing the loss due to the ground layer can be mentioned. Therefore, the surface roughness of the ground layer is preferably small.

[0080] When the form of the ground layer is a periodic structure, a function of selectively reflecting or transmitting a specific frequency can be exhibited. 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, so that a function of transmitting frequencies other than the operating frequency can be imparted. Further, when a structure in which holes are periodically provided at locations where there is no conductive material is used, it is possible to design a reflectarray that asymmetrically reflects the operating frequency while transmitting only a specific frequency.

[0081] (Support) The reflectarray is installed on a support. As the support, a new panel or pole may be installed, or an existing signboard, wall, ceiling, etc. may be used. The support preferably has a mechanism capable of adjusting the angle of the reflectarray in the vertical or horizontal direction, and more preferably has a mechanism capable of moving 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, an adhesive layer, or the use of a magnet when the support is made of metal can be mentioned. 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 properties to the surface of the reflectarray. For example, when used for building materials such as wallpaper, a design layer may be further provided to harmonize with the space. Also, when used as a whiteboard, a functional film may be used as the design layer. It is assumed that the function of the protective layer described later may be imparted to the design layer.

[0084] (Protective layer) For the protective layer, in order to prevent oxidative degradation, physical damage, and peeling of the element pattern and the ground layer, the use of a film or sheet having gas barrier properties, water vapor barrier properties, water resistance, abrasion resistance, and scratch resistance can be mentioned.

[0085] When assuming the indoor use of the reflect array, it is preferable to use a protective layer having antibacterial properties, antiviral properties, stain resistance, etc. Also, when assuming the outdoor use of the reflect array, since weather resistance is required, 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 were summarized in Table 1, and the results of Examples 5-7 were summarized in Table 2. In addition, FIG. 12 is a diagram showing the structure of the reflect array of Example 1 in the xy plane. However, the unit of the dimensions in the figure is mm.

Table 1

Table 2

[0087] (Comparative Example 1) A reflect array 6 with a basic configuration was constructed, where copper with a thickness of 0.018 mm was used for the element pattern 1 and the ground layer 3, and a composite material of glass / epoxy resin with a thickness of 1.564 mm was used for the dielectric layer 2. However, the conductivity of copper was 5.8×10^7 siemens / m, the real part of the relative permittivity of the dielectric layer 2 was 4.5, and tanδ was 0.014.

[0088] The operating frequency was set to 4.85 GHz, the target reflection characteristics (the desired reflection characteristics) were set to θix = -60°, θrx = 0°, θiy = θry = 0°, and the size Lx of the reflection control region 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 sizes of the unit cell in the x-axis direction and y-axis direction were set to 23.792 mm. The shape of the element pattern was a cross patch in which two square patches were orthogonal in the xy plane. Here, it was assumed that only the element length differed in each element pattern within the reflection control region 5. Specifically, the element lengths were lx1 = ly1, lx2 = ly2, lx3 = ly3, and the element widths were wx1 = wx2 = wx3 = wy1 = wy2 = wy3 = 9.000 mm. In addition, in Table 1, Table 2, the figures and texts in the subsequent descriptions, the unit cells included in the reflection control region 5 are represented as unit cell 1, unit cell 2,... unit cell p (p is an integer from 1 to the number of divisions n). 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 may be omitted. When wxp and wyp are equal, the subscripts x and y may be omitted. 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 method analysis software (HFSS) manufactured by Ansys. FIG. 13 shows 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 subsequent descriptions, the figures of the element length l and the reflection phase also show the same conditions as in FIG. 13.

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

[0092] The reflectarray 6 was arranged with 12×12 unit cells in the x-axis and y-axis directions, and the size in the xy plane was 285.504 mm square. The reflection characteristics were analyzed using HFSS when the reflectarray 6 was irradiated with a polarization parallel to the y-axis at θix = -60° and θiy = 0°.

[0093] In order to grasp the influence of dimensional errors on the reflection characteristics, assuming dimensional errors due to machining, the analysis was similarly performed for the case where the element length l of each element pattern of the reflectarray 6 was increased by 0.100 mm each.

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

[0095] (Example 1) A reflectarray was prepared in which other than the element pattern shape was the same as the reflectarray described in Comparative Example 1. As the element pattern shape, only the element width of each element pattern in the reflection control region 5 was different. Specifically, the element lengths of each element pattern were lx1 = lx2 = lx3 = ly1 = ly2 = ly3 = 15.000 mm, and the element widths within the same element pattern were wx1 = wy1, wx2 = wy2, wx3 = wy3. The reflection phase of the unit cell with respect to the element width w and the reflection characteristics of the reflectarray 6 with / without dimensional errors were analyzed using HFSS.

[0096] FIG. 15 shows the analysis results of the unit cell in the design process of Example 1, and is a diagram showing the reflection phase when the element length of the element pattern is set to lx = ly = 15.000 mm and the element width w is changed. In FIG. 15, the element width w on the horizontal axis represents the element width wx in the x-axis direction and the element width wy in the y-axis direction. In the following description, the diagrams of the element width w and the reflection phase also show the same conditions as in FIG. 15. As the element width changed, the reflection phase changed. Also, the slope of the reflection phase with respect to the element width was gentler compared to the case of FIG. 13 of Comparative Example 1 where the element length was changed. For example, in order for the reflection phase to change from 120° to -120°, in Comparative Example 1, it was necessary to change the element length l by about 2.5 mm between approximately 13.5 mm and 16 mm, whereas in Example 1, it was necessary to change the element length w by about 6 mm between approximately 5 mm and 11 mm. This means that when the same degree of dimensional error occurs, the present invention using the element width as a design parameter has a smaller change width of the reflection phase in the unit cell, and as a result, the change in the reflection characteristics as the reflectarray 6 is smaller.

[0097] The element widths w were determined to be wx1 = wy1 = 8.306 mm, wx2 = wy2 = 1.305 mm, and wx3 = wy3 = 9.608 mm, respectively. FIG. 16 shows the analysis results of the reflectarray 6 obtained in Example 1, and is a diagram showing the reflection patterns 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 = -60° was reflected in the desired direction of θrx = 0°, and its RCS was 7.03 dBsm. Also, in the reflectarray 6 with dimensional error, reflection occurred in the direction of θrx = 0°, and its RCS was 7.02 dBsm. Therefore, the change in RCS due to the dimensional error was -0.02 dBsm, and compared with the reflectarray 6 using the element length described in Comparative Example 1 as a design parameter, the decrease in the reflection intensity due to the dimensional error could be suppressed.

[0098] Note that the design method will be specifically described. What is described here is a design method for a reflectarray in which a plurality of the same reflection control regions are arranged in the x-axis direction and the y-axis direction. (Step 1) First, set the target reflection characteristics (operating frequency, incident angle, and reflection angle). (Step 2) Subsequently, use Equation (1) and Equation (2) to determine the sizes Lx and Ly of the reflection control region. When performing asymmetric reflection only in the x-axis direction, Lx is determined by Equation (1), and Ly can be of any size. Also, when performing asymmetric reflection only in the y-axis direction, Ly is determined by Equation (2), and Lx can be of any size. (Step 3) Subsequently, divide the size Lx of the reflection control region into n parts and divide Ly into m parts. The size of the unit cell is determined. (Step 4) Subsequently, within the range that fits within the unit cell, determine the element lengths lx and ly of the element pattern. Since the element patterns are evenly arranged without bias within the unit cell, as a result, the gaps gx and gy between the element patterns are also determined. (Step 5) Subsequently, analyze the reflection phase of the unit cell with the element width w as a design parameter. As shown in FIG. 15, derive the reflection phase with the element widths wx and wy of the element pattern as design parameters, and obtain an analysis result showing the relationship between the element width and the reflection phase in the unit cell. (Step 6) Subsequently, calculate the ideal reflection phase or impedance for realizing the reflection characteristics of the target reflection control region using Equations (3) to (8), and select the element width w that realizes the desired reflection phase or impedance based on the above analysis result. In the case of Example 1, three element widths are selected, and a reflection control region including three unit cells is set. (Step 7) Subsequently, form a reflectarray so as to include at least one reflection control region. Analyze the reflection characteristics of the reflectarray. (Step 8) Note that based on the analysis result of Step 7, it is also possible to further finely adjust the element widths wx and wy using an optimization method so that the RCS at the target reflection angle is further increased and the RCS at angles other than the target angle is decreased.

[0099] (Comparative Example 2) A reflectarray 6 with a basic configuration was constructed by using copper with a thickness of 0.018 mm for the element pattern 1 and the ground layer 3, and a composite material of glass / fluororesin with a thickness of 0.764 mm 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 permittivity of the dielectric layer 2 was 2.6, and tanδ was 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 in the x-axis direction of the reflection control region 5 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 sizes in the x-axis and y-axis directions of the unit cell were set to 6.746 mm. The shape of the element pattern was a cross-patch in which two square patches were orthogonal in the xy plane. Here, it was assumed that only the element length of each element pattern within the reflection control region 5 was different. Specifically, the element lengths were lx1 = ly1, lx2 = ly2, lx3 = ly3, and the element widths were wx1 = wx2 = wx3 = wy1 = wy2 = wy3 = 1.000 mm.

[0102] First, the reflection phase of the unit cell 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 shows the reflection phase when the element width of the element pattern was wx = wy = 1.000 mm and the element length l was 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 to follow the impedance distribution of Equation (7). The element lengths l were lx1 = ly1 = 3.390 mm, lx2 = ly2 = 3.709 mm, and lx3 = ly3 = 3.067 mm, respectively. The element lengths l of each element pattern determined here were assumed to have no dimensional error.

[0104] The reflectarray 6 was arranged with 9×9 unit cells in the x-axis and y-axis directions, and its size in the xy plane was 60.714 mm square. The reflection characteristics were analyzed using HFSS when the reflectarray 6 was irradiated with a polarization parallel to the y-axis at θix = 33° and θiy = 0°.

[0105] To understand the influence of dimensional errors on the reflection characteristics, assuming dimensional errors due to machining, the analysis was also performed when the element length l of each element pattern of the reflectarray 6 was increased by 0.100 mm each.

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

[0107] (Example 2) A reflectarray was prepared in which other than the element pattern shape was the same as the reflectarray described in Comparative Example 2. As the element pattern shape, only the element width of each element pattern in the reflection control region 6 was different. Specifically, the element lengths of each element pattern were lx1 = lx2 = lx3 = ly1 = ly2 = ly3 = 3.250 mm, and the element widths were wx1 = wy1, wx2 = wy2, wx3 = wy3. The reflection phase of the unit cell with respect to the element width w and the reflection characteristics of the reflectarray with / without dimensional errors were analyzed using HFSS.

[0108] FIG. 19 shows the analysis results of the unit cell in the design process of Example 2, and is a diagram showing the reflection phase when the element length of the element pattern is set to lx = ly = 3.250 mm and the element width w is changed. As the element width changed, the reflection phase changed. Also, the slope of the reflection phase with respect to the element width was gentler compared to the case of FIG. 17 of Comparative Example 2 where the element length was changed. For example, in order for the reflection phase to change from 60° to -120°, in Comparative Example 2, it was necessary to change the element length l by only 0.3 mm between approximately 3.2 mm and 3.5 mm, whereas in Example 2, it was necessary to change the element length w by 1.8 mm between approximately 0.6 mm and 2.4 mm. This means that when the same degree of dimensional error occurs, Example 2 using the element width as a design parameter has a smaller change width of the reflection phase in the unit cell, and as a result, the change in the reflection characteristics as the reflectarray 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 shows the analysis results of the reflectarray 6 obtained in Example 2, and is a diagram showing the reflection patterns 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 direction of θrx = 0°, and its RCS was 0.26 dBsm. Also, in the reflectarray 6 with dimensional error, reflection occurred in the direction of θrx = 0°, and its RCS was 0.18 dBsm. Therefore, the change in RCS due to dimensional error was -0.08 dBsm, and compared to the reflectarray 6 using the element length described in Comparative Example 2 as a design parameter, the decrease in reflection intensity due to dimensional error could be suppressed.

[0110] (Comparative Example 3) A reflectarray 6 having a basic configuration was constructed in which copper with a thickness of 0.018 mm was used for the element pattern 1 and the ground layer 3, and PTFE with a thickness of 0.200 mm was used for the dielectric layer 2. However, the conductivity of copper was 5.8×10^7 siemens / m, the real part of the relative permittivity of the dielectric layer 2 was 2.06, and tanδ was 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 in the x-axis direction of the reflection control region 5 was determined to be 7.065 mm using Equation 1.

[0112] The number of divisions of the reflection control region 5 was set to 3, and the sizes in the x-axis and y-axis directions of the unit cell were set to 2.355 mm. The shape of the element pattern was a cross-patch in which two square patches were orthogonal in the xy plane. Here, it was assumed that only the element width differed for each element pattern within the reflection control region 5. Specifically, the element lengths were lx1 = ly1, lx2 = ly2, lx3 = ly3, and the element widths were wx1 = wx2 = wx3 = wy1 = wy2 = wy3 = 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 to follow the impedance distribution of Equation (7). The element lengths l were lx1 = ly1 = 1.844 mm, lx2 = ly2 = 1.581 mm, lx3 = ly3 = 1.753 mm, respectively. The element lengths l of each element pattern determined here were assumed to have no dimensional error.

[0115] The reflectarray 6 was arranged with 27 × 27 unit cells in the x-axis and y-axis directions, and the size in the xy plane was 63.585 mm square. The reflection characteristics when irradiating the reflectarray 6 with a polarization parallel to the y-axis at θix = 0°, θiy = 0° were analyzed using HFSS.

[0116] In order to grasp the influence of dimensional errors on the reflection characteristics, the analysis was similarly carried out for the case where the element length l of each element pattern of the reflectarray 6 was increased by 0.100 mm each by machining, assuming dimensional errors due to machining.

[0117] FIG. 22 shows the analysis results of the reflectarray 6 obtained in Comparative Example 3, and is a diagram showing the reflection characteristics of the reflectarray 6 with / 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 direction of θrx = 45°, and its RCS was 7.40 dBsm. On the other hand, in the reflectarray with dimensional errors, although reflection occurred in the direction of θrx = 0°, its RCS was 5.12 dBsm, and the change in RCS due to dimensional errors was -2.28 dBsm.

[0118] (Example 3) A reflectarray was prepared in which other than the element pattern shape was the same as the reflectarray described in Comparative Example 3. As the element pattern shape, only the element width of each element pattern in the reflection control region 5 was different. Specifically, the element lengths of each element pattern were lx1 = lx2 = lx3 = ly1 = ly2 = ly3 = 1.700 mm, and the element widths were wx1 = wy1, wx2 = wy2, wx3 = wy3. The reflection phase of the unit cell with respect to the element width w and the reflection characteristics of the reflectarray 6 with / without dimensional errors were analyzed using HFSS.

[0119] FIG. 23 shows the analysis results of the unit cell in the design process of Example 3, and is a diagram showing the reflection phase when the element length of the element pattern is lx = ly = 1.700 mm and the element width w is changed. As the element width changed, the reflection phase changed. Also, the slope of the reflection phase with respect to the element width was gentler compared to the case of FIG. 21 of Comparative Example 3 where the element length was changed. For example, in order for the reflection phase to change from 120° to -120°, in Comparative Example 3, it was necessary to change the element length l by only 0.3 mm between approximately 1.5 mm and 1.8 mm, whereas in Example 3, it was necessary to change the element length w by only 1.4 mm between approximately 0.1 mm and 1.5 mm. This means that when the same degree of dimensional error occurs, Example 3 using the element width as a design parameter has a smaller change width of the reflection phase in the unit cell, and as a result, the change in the reflection characteristics as the reflectarray 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 shows the analysis results of the reflectarray 6 obtained in Example 3, and is a diagram showing the reflection patterns 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 = 0° was reflected in the desired θrx = 45° direction, and its RCS was 7.46 dBsm. Also, in the reflectarray 6 with dimensional error, reflection occurred in the θrx = 0° direction, and its RCS was 7.46 dBsm. Therefore, the change in RCS due to dimensional error was 0.00 dBsm, and compared to the reflectarray 6 using the element length described in Comparative Example 3 as a design parameter, a decrease in reflection intensity due to dimensional error could be suppressed.

[0121] (Comparative Example 4) A reflectarray 6 having a basic configuration was constructed in which copper with a thickness of 0.002 mm was used for the element pattern 1 and the ground layer 3, and PET with a thickness of 0.050 mm was used for the dielectric layer 2. However, the conductivity of copper was 5.8×10^7 siemens / m, the real part of the relative dielectric constant of the dielectric layer 2 was 3.03, and tanδ was 0.00476.

[0122] The operating frequency was set to 100 GHz, the target reflection characteristics were set to θix = 0°, θrx = 45°, θiy = θry = 0°, and the size Lx in the x-axis direction of the reflection control region 5 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 sizes in the x-axis and y-axis directions of the unit cell were set to 1.060 mm. The shape of the element pattern was a cross-patch in which two square patches were orthogonal in the xy plane. Here, it was assumed that only the element length differed for each element pattern within the reflection control region 5. Specifically, the element lengths were lx1 = ly1, lx2 = ly2, lx3 = ly3, 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 widths of the element patterns are wx = wy = 0.400 mm and the element width l is changed. 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 to follow the impedance distribution of Equation (7). The element lengths l were lx1 = ly1 = 0.929 mm, lx2 = ly2 = 0.959 mm, lx3 = ly3 = 0.862 mm, and lx4 = ly4 = 0.910 mm, respectively. The element lengths l of each element pattern determined here were assumed to have no dimensional error.

[0126] The reflectarray 6 was arranged with 12 × 12 unit cells in the x-axis and y-axis directions, and the size in the xy plane was 12.720 mm square. The reflection characteristics when irradiating the reflectarray 6 with a polarization parallel to the y-axis at θix = 0° and θiy = 0° were analyzed using HFSS.

[0127] In order to grasp the influence of dimensional errors on the reflection characteristics, the analysis was similarly carried out for the case where the element length l of each element pattern of the reflectarray 6 was increased by 0.100 mm each by machining, assuming dimensional errors due to machining.

[0128] FIG. 26 shows the analysis results of the reflectarray 6 obtained in Comparative Example 4, and is a diagram showing the reflection characteristics of the reflectarray 6 with / 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 direction of θrx = 45°, and its RCS was -17.5 dBsm. On the other hand, in the reflectarray 6 with dimensional errors, although reflection occurred in the direction of θrx = 0°, its RCS was -29.9 dBsm, and the change in RCS due to dimensional errors was -12.34 dBsm.

[0129] (Example 4) A reflectarray was prepared in which everything other than the element pattern shape was the same as the reflectarray described in Comparative Example 4. As the element pattern shape, only the element width of each element pattern in the reflection control region 5 was different. Specifically, the element lengths of each element pattern were lx1 = lx2 = lx3 = ly1 = ly2 = ly3 = 0.900 mm, and the element widths were wx1 = wy1, wx2 = wy2, wx3 = wy3, wx4 = wy4. The reflection phase of the unit cell with respect to the element width w and the reflection characteristics of the reflectarray 6 with / without dimensional errors were analyzed using HFSS.

[0130] FIG. 27 shows the analysis results of the unit cell in the design process of Example 4, and is a diagram showing the reflection phase when the element length of the element pattern is lx = ly = 0.900 mm and the element width w is changed. As the element width changed, the reflection phase changed. Also, the slope of the reflection phase with respect to the element width was gentler compared to the case of FIG. 25 of Comparative Example 4 where the element length was changed. For example, in order for the reflection phase to change from 120° to -120°, in Comparative Example 4, it was necessary to change the element length l by only 0.1 mm between approximately 0.85 mm and 0.95 mm, whereas in Example 4, it was necessary to change the element length w by only 0.45 mm between approximately 0.2 mm and 0.65 mm. This means that when the same degree of dimensional error occurs, Example 4 using the element width as a design parameter has a smaller change width of the reflection phase in the unit cell, and as a result, the change in the reflection characteristics as the reflectarray 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 shows the analysis results of the reflectarray 6 obtained in Example 4, and is a diagram showing the reflection patterns 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 = 0° was reflected in the desired direction of θrx = 45°, and its RCS was -17.4 dBsm. Also, in the reflectarray with dimensional error, reflection occurred in the direction of θrx = 0°, and its RCS was -19.9 dBsm. Therefore, the change in RCS due to dimensional error was -2.51 dBsm, and compared to the reflectarray with the element length described in Comparative Example 4 as a design parameter, the decrease in reflection intensity due to dimensional error could be suppressed.

[0132] (Example 5) For the basic configuration using copper with a thickness of 0.018 mm for the element pattern 1 and the ground layer 3 and a composite material of glass / fluororesin with a thickness of 0.764 mm for the dielectric layer 2, a design layer 10 with a thickness of 0.098 mm was laminated in the manner of Fig. 2(c) with a 0.500 mm gap on the element pattern side to form a reflectarray 6c. However, the conductivity of copper was set to 5.8×10^7 siemens / m, the real part of the relative permittivity of the dielectric layer 2 was 2.6, tanδ was 0.0025, the real part of the relative permittivity of the design layer 10 was 2.70, and tanδ was 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 in the x-axis direction of the reflection control region 5 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 sizes in the x-axis and y-axis directions of the unit cell were set to 6.746 mm. The shape of the element pattern was a cross-patch in which two square patches were orthogonal in the xy plane. Here, it was assumed that only the element width differed for each element pattern within the reflection control region 5. Specifically, the element lengths were lx1 = lx2 = lx3 = ly1 = ly2 = ly3 = 3.250 mm, and the element widths were wx1 = wy1 = 1.582 mm, wx2 = wy2 = 2.955 mm, and wx3 = wy3 = 0.319 mm.

[0135] The reflectarray 6c was arranged with 9×9 unit cells in the x-axis and y-axis directions, and its size in the xy plane was 60.714 mm square. The reflection characteristics when irradiating the reflectarray 6c with a polarization parallel to the y-axis at θix = 33° and θiy = 0° were analyzed using HFSS.

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

[0137] (Example 6) For the basic configuration in which copper with a thickness of 0.018 mm is used for the element pattern 1 and the ground layer 3, and a composite material of glass / fluororesin with a thickness of 0.764 mm is used for the dielectric layer 2, a polyimide-based protective layer 8 with a thickness of 0.060 mm is laminated in the manner of Fig. 2(a) to form the reflectarray 6a. However, the conductivity of copper is 5.8×10^7 siemens / m, the real part of the relative permittivity of the dielectric layer is 2.6, tanδ is 0.0025, the real part of the relative permittivity of the protective layer 8 is 3.23, and tanδ is 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 in the x-axis direction of the reflection control region 5 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 sizes in the x-axis and y-axis directions of the unit cell were set to 6.746 mm. The shape of the element pattern was a cross patch in which two square patches were orthogonal in the xy plane. Here, it was assumed that only the element width differed for each element pattern within the reflection control region 5. Specifically, the element lengths were lx1 = lx2 = lx3 = ly1 = ly2 = ly3 = 3.000 mm, and the element widths were wx1 = wy1 = 1.703 mm, wx2 = wy2 = 2.986 mm, and wx3 = wy3 = 0.075 mm.

[0140] The reflectarray 6a was arranged with 9×9 unit cells in the x-axis and y-axis directions, and the size in the xy plane was 60.714 mm square. The reflection characteristics when irradiating the reflectarray with a polarization parallel to the y-axis at θix = 33° and θiy = 0° were analyzed using HFSS.

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

[0142] (Example 7) A reflectarray 6 with a basic configuration was constructed by using copper with a thickness of 0.002 mm for the element pattern and the ground layer, and polystyrene with a thickness of 0.050 mm for the dielectric layer. However, the conductivity of copper was set to 5.8×10^7 siemens / m, the real part of the relative permittivity of the dielectric layer was 2.47, and tanδ was 0.000644.

[0143] The operating frequency was set to 28 GHz, the target reflection characteristics were set to θix = 0°, θrx = 45°, θiy = θry = 0°, and the size Lx of 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 sizes of the unit cell in the x-axis and y-axis directions were both 3.785 mm. The shape of the element pattern was a cross patch in which two square patches were orthogonal in the xy plane. Here, it was assumed that only the element widths of each element pattern within the reflection control region 5 were different. Specifically, the element lengths were lx1 = lx2 = lx3 = ly1 = ly2 = ly3 = 3.450 mm, and the element widths were wx1 = wy1 = 2.697 mm, wx2 = wy2 = 2.892 mm, wx3 = wy3 = 2.460 mm, wx4 = wy4 = 2.639 mm.

[0145] The reflectarray 6 was arranged with 16×16 unit cells in the x-axis and y-axis directions, and its size in the xy plane was 60.560 mm square. The reflection characteristics when irradiating the reflectarray 6 with a polarization parallel to the y-axis at θix = 0° and θiy = 0° were analyzed using HFSS.

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

[0147] (Function and Effect) By using the element width as a design parameter, it is possible to reduce the phase change based on the design parameter and suppress the degradation of the reflection characteristics with respect to dimensional errors. As a result, the yield of the reflectarray can be improved.

[0148] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

[0149] [Other Embodiments] Aspects that can be the content of the present invention are described below, but are not limited thereto. (Aspect 1) A reflectarray in which at least an element pattern, a dielectric layer, and a ground layer are laminated in this order, The reflectarray includes at least one reflection control region, The reflection control region includes at least a first unit cell and a second unit cell, A first element pattern is arranged in the first unit cell, A second element pattern having a shape different from that of the first element pattern is arranged in the second unit cell, A reflectarray characterized in that the reflection characteristics in the first unit cell are different from the reflection characteristics in the second unit cell. (Aspect 2) The first element pattern and the second element pattern have an element length that is the length in the first direction and an element width that is the length in a second direction perpendicular to the first direction, A first element length that is the element length of the first element pattern and a second element length that is the element length of the second element pattern are the same length, The reflection phase of the reflection control region is set according to a first element width that is the element width of the first element pattern and a second element width that is the element width of the second element pattern The reflectarray according to aspect 1, characterized by the above. (Aspect 3) The reflective array according to Embodiment 1 or Embodiment 2 including a design layer. (Embodiment 4) The reflective array according to any one of Embodiments 1 to 3 including a protective layer. (Embodiment 5) A reflective array device having the reflective array according to any one of Embodiments 1 to 4 provided on a support. (Embodiment 6) A method for designing a reflective array in which at least an element pattern, a dielectric layer, and a ground layer are laminated in this order, the reflective array includes at least one reflection control region, the reflection control region includes at least a first unit cell and a second unit cell, one first element pattern is arranged in the first unit cell, a second element pattern having a shape different from that of the first element pattern is arranged in the second unit cell, the reflection characteristics in the first unit cell are set to be different from the reflection characteristics in the second unit cell, characterized by the above. A method for designing a reflective array.

Description of Signs

[0150] 1, 1 1 -1 n , 1d 1 -1d 3 , 1e 1 -1e 3 , 1a - 1c, 1 x 1 -1 x n , 1 y 1 -1 y n Element pattern, 2 Dielectric layer, 3 Ground layer, 4, 4 1 -4 n , 4a - 4c, 4 x 1 -4 x n , 4 y1 -4 y n Unit cell, 5, 5a - 5h, 5x, 5y reflection control regions, 6, 6a - 6h reflect arrays, 7 functional layers, 8 protective layers, 9 adhesive layers, 10 decorative layers, 11 installation layers

Claims

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

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

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

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

5. The reflect array according to claim 1 , wherein the ground layer is in a mesh shape.

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

7. A design method for a reflectarray that generates a predetermined asymmetric reflection of an electromagnetic wave along a first direction by stacking at least an element pattern, a dielectric layer, and a ground layer in this order, comprising: The reflect array includes at least one reflection control area, the reflection control region includes n (n is an integer of 2 or more) unit cells equally spaced in a first direction, an m-th element pattern arranged in an m-th unit cell (m is an integer between 1 and n) has a different shape from a p-th element pattern arranged in a p-th unit cell (p is an integer between 1 and n but not including m); a reflectance characteristic of the m unit cell is set to be different from a reflectance characteristic of the p unit cell; A method for designing a reflect array comprising the steps of:

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