Reflectarray, electromagnetic wave reflection system, and method for installing a reflectarray

Abstract

To provide a reflect array that reflects electromagnetic waves incident from a wide angle range to a specific reflection angle, an electromagnetic wave reflection system, and an installation method for the reflect array.SOLUTION: Reflect arrays have a reflection control area that controls a phase. When the length of the long side is denoted as L, the wavelength of the electromagnetic wave to be reflected is denoted as λ, the incident angle is denoted as θi, and the reflection angle is denoted as θr, the reflection control area satisfies the following equation (1). An incident angle |θi| is in a range of 45° to 70°. The incident angle θi and the reflection angle θr satisfy the relationship of the following equation (2). An incident allowable angle range Δθi is in a range of greater than 5.5° and less than or equal to 16°.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a reflectarray, an electromagnetic wave reflection system, and a method for installing a reflectarray.

Background Art

[0002] With the progress of digitization in society, the data communication speed in wireless communication has improved dramatically, and the associated high-frequencyization of electromagnetic waves has advanced. However, since electromagnetic waves become more rectilinear as the frequency increases, electromagnetic waves do not penetrate into areas such as the shadow of a building, 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 rapidly increase the number of base stations. In recent years, in order to solve these problems, technologies for controlling the direction of electromagnetic waves have attracted attention.

[0003] Among such technologies, the development of a metamaterial reflector or a metasurface reflector that can freely control the reflection angle of electromagnetic waves has been actively carried out. Metamaterial reflectors include an active reflector that controls the directions of incident and reflected electromagnetic waves by electrical control (for example, Patent Document 1), and a passive reflector that has no electrical control mechanism and determines the directions of incident and reflected electromagnetic waves at the design stage, and designs the element dimensions and material physical properties based on that (for example, Patent Document 2).

[0004] In Patent Document 1, it is composed of a metamaterial structure and a variable capacitor connected to the metamaterial structure, and the phase is controlled by the fixed capacitance of the metamaterial structure and the variable capacitance by the variable capacitor. The operation of the variable capacitor is controlled by a phase control signal (bias voltage). Thereby, it is possible to reflect / scatter the electromagnetic waves radiated from the electromagnetic wave source in an arbitrary direction.

[0005] Further, Patent Document 2 discloses a metal ground layer provided on the bottom surface of a dielectric substrate, which does not transmit a metasurface reflector for all polarization directions, and a metasurface reflector including a plurality of supercells having two or more types of cross-shaped metal resonators with different arm lengths. The phase of this metasurface reflector can be controlled by the structure of the metal resonator.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] Since an active reflector can control the angle between the incident electromagnetic wave and the reflected electromagnetic wave by changing a voltage or the like, the angle can be appropriately adjusted according to the angles of the transmitter and the receiver, and there is a high degree of practical freedom. However, since a phase control signal for controlling the phase is required, there is a problem that it becomes expensive. In addition, since a passive reflector has no electrical control mechanism, it can be manufactured at low cost. However, since the angle between the incident electromagnetic wave and the reflected electromagnetic wave is fixed, there is a problem that the practical freedom is small. Therefore, an object of the present invention is to provide a reflectarray, an electromagnetic wave reflection system, and a method for installing a reflectarray, which are passive reflectors that can be manufactured at low cost and can reflect electromagnetic waves incident from a wide range of angles to a predetermined angle.

Means for Solving the Problems

[0008] To solve the above problems, a typical reflectarray of the present invention is a reflectarray that reflects electromagnetic waves. The reflectarray has a reflection control region for controlling the phase. When the length of the long side of the reflection control region is L, the wavelength of the electromagnetic wave to be reflected is λ, the incident angle is θi, and the reflection angle is θr, the reflectarray satisfies Equation (1) (described later). The incident angle |θi| is in the range of 45° or more and 70° or less, and the incident angle θi and the reflection angle θr satisfy the relationship of Equation (2) (described later). The incident acceptance angle range Δθi is greater than 5.5° and less than or equal to 16°. The reflectarray is characterized by this.

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a reflectarray that can reflect electromagnetic waves incident from a wide angle range to a predetermined angle. 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

[0010]

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Mode for Carrying Out the Invention

[0011] 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 the same reference numeral and different subscripts. Also, when it is not necessary to distinguish these multiple 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 the 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.

[0012] (Explanation of Terms) FIG. 1 is a diagram showing the configuration of a reflectarray. FIG. 1a is a diagram showing the overall configuration of the reflectarray, and FIG. 1b is an enlarged view showing a part of the reflection control region. Terms related to the configuration of the reflectarray of the present disclosure will be explained with reference to the figures. In the present disclosure, a "reflectarray (electromagnetic wave reflector)" is a member that reflects electromagnetic waves and has one or more reflection control regions for controlling the phase, and is a reflector that does not perform phase control by external power. It includes those that cause asymmetric reflection where the incident angle and the reflection angle are different, those that scatter electromagnetic waves in multiple directions, and those that collect electromagnetic waves at specific locations. In the following description, an xyz coordinate system is applied, and it is assumed that the reflectarray is arranged on the xy plane. Phase control by external power refers to an active reflector that has an external power source and can control the phase by controlling a voltage or the like.

[0013] Also, the "reflection control region" refers to a part of the region constituting the reflectarray. The reflection control region is the smallest region that can reflect the electromagnetic waves incident on that region in a predetermined direction. And the reflectarray is configured by combining one or more reflection control regions. When referring to the reflection control region, in addition to a two-dimensional region where the electromagnetic waves are in a direction parallel to the incident region, it is assumed to include a layer structure formed in a direction perpendicular to the region. In one reflection control region, the size (long side) of the side of the reflection control region where a plurality of unit cells are arranged is defined as L, and the size (short side) of the side of the reflection control region where only one unit cell is arranged is defined as M.

[0014] Also, the "unit cell" refers to a region obtained by dividing the reflection control region. One unit cell contains one element pattern (element). There are two or more unit cells in one reflection control region.

[0015] 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. 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.

[0016] Figure 2 is a diagram showing the incident angle and the reflection angle when the reflect array is arranged on the xy plane. Terms related to the definition of the angle in the present disclosure will be described with reference to Figure 2. Also, the angle θx in the x-axis direction is represented by a positive angle (0° to 180°) when it spreads in the direction from the +z-axis direction to the +x-axis direction, and is represented by a negative angle (0° to -180°) when it spreads in the direction from the +z-axis direction to the -x-axis direction. Similarly, the angle θy in the y-axis direction is represented by a positive angle (0° to 180°) when it spreads in the direction from the +z-axis direction to the +y-axis direction, and is represented by a negative angle (0° to -180°) when it spreads in the direction from the +z-axis direction to the -y-axis direction.

[0017] In the present disclosure, the "incident angle" is the incident angle θi of the electromagnetic wave incident on the reflection control region, and the "reflection angle" is the reflection angle θr of the electromagnetic wave reflected from the reflection control region. When the wavelength of the electromagnetic wave reflected from the reflection control region is λ, the reflection control region is designed to satisfy the following formula (1).

Equation

[0018] In the present disclosure, the "electromagnetic wave reflection system" is composed of a transmitter, a reflectarray, and a receiver. The "transmitter" refers to something that emits electromagnetic waves or something that reflects electromagnetic waves coming from something that emits electromagnetic waves. Specifically, there are a radio base station, a mobile station, a repeater, a moving body, a communication terminal, a reflector, etc. In addition, the "receiver" refers to something that receives electromagnetic waves. Specifically, there are a radio base station, a mobile station, a repeater, a moving body, a communication terminal, a reflector, etc. In the present disclosure, the "primary radiation" is the electromagnetic wave radiated from the transmitter in the electromagnetic wave reflection system. The "secondary radiation" refers to the radiation of the electromagnetic wave radiated from the reflectarray in the electromagnetic wave reflection system, which is caused by the primary radiation of the electromagnetic wave from the transmitter incident on the reflectarray.

[0019] [First Embodiment] (Configuration of Reflectarray) Referring to FIGS. 1 and 3, the configuration of the reflectarray and the configuration of the element pattern will be described. FIG. 3 is a diagram showing an example of the layer configuration of the reflectarray 6. The reflectarray 6 in FIG. 3 periodically arranges a plurality of element patterns in a plane, and the direction of the reflected wave can be set to a desired value. The reflectarray 6 includes at least an element pattern (element) 1, a dielectric layer 2, and a ground layer (ground plane) 3. In the following description, an xyz coordinate system is applied, and the reflectarray 6 is arranged on the xy plane.

[0020] The reflectarray 6 in FIG. 1b causes a predetermined asymmetric reflection of electromagnetic waves along the x-axis. The reflectarray 6 has at least one or more reflection control regions 5. The reflection control region 5 includes unit cells 41, 42, 43,... 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 portion obtained by equally dividing the reflection control region 5 along the x-axis direction. n is the number of divisions when the reflection control region is divided into unit cells in the x-axis direction. The unit cell 4 is square. When the size (length) of the unit cell 4 is s, the size (long side) of the reflection control region 5 in the x-axis direction is Lx, and the size (short side) in the y-axis direction is My, then s = Lx / n = My. Also, the size of the reflectarray 6 is determined by the size and number of the reflection control regions 5. For example, for a reflectarray that causes asymmetric reflection in the x-axis direction, when there are 8 reflection control regions 5 arranged in the x-axis direction and 6 arranged in the y-axis direction, the size of the reflectarray 6 in the x-axis direction is 8Lx, and the size in the y-axis direction is 6My. The reflection pattern of the reflectarray 6 changes according to the number of reflection control regions arranged in the direction of asymmetric reflection. That is, in FIG. 1b, the reflection pattern changes according to the number of reflection control regions arranged in the x-axis direction, but the number of reflection control regions arranged in the y-axis direction does not affect the reflection pattern. The more the number of reflection control regions arranged in the x-axis direction, the thinner the reflection pattern of the reflectarray. The number of reflection control regions arranged in the y-axis direction affects the reflection intensity, and the more the number of reflection control regions arranged in the y-axis direction, the greater the reflection intensity. In FIG. 1, the reflection control region 5 is composed of n unit cells 4 arranged in the x-axis direction, and the reflectarray 6 is shown to include a plurality of reflection control regions 5. However, 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.

[0021] (Configuration of Element Pattern) An element pattern is formed on the surface of the unit cell 4 facing the +z-axis direction. Using the division number n, the unit cell 41, unit cell 42, … unit cell 4 n are represented as such. An element pattern 11 is formed on the unit cell 41. An element pattern 12 is formed on the unit cell 42. An element pattern 13 is formed on the unit cell 43. The unit cell 4 n has an element pattern 1 n formed thereon.

[0022] Within the reflection control region of FIG. 1, each element pattern has a shape that is slightly different from other element patterns. Here, the shape of the element pattern shown from the element pattern 11 to the element pattern 1 n is sometimes referred to as a cross patch. The cross patch refers to a shape in which two rectangular patches are orthogonal in the xy plane. The element pattern 11 has a rectangular patch with 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 with 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 common position of the centers of gravity. Similarly, the element pattern 1 n has a rectangular patch with an element length lxn and an element width wyn, and a rectangular patch with an element length lyn and an element width wxn, and has a shape in which they are orthogonal with the common position of the centers of gravity.

[0023] (Description of Each Configuration, Design Method) (Configuration of Layers) Referring to FIG. 3, the layer structure of the reflect array 6 will be described. The reflect array 6 has a structure 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, the structure composed of the three layers of the element pattern 1, the dielectric layer 2, and the ground layer 3 is referred to as the "basic structure". 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, the ground layer 3 side, or both sides of the basic structure of the reflect array 6. In the following description, when referring to the 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, it may be referred to as a "functional layer".

[0024] 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. In addition, 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.

[0025] Examples of the functional layer include a design layer with a design considering the landscape of the place 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 a ceiling, a protection layer for protecting the basic structure, and an adhesive layer for laminating each layer.

[0026] (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 changed. For example, when electromagnetic waves of a certain wavelength are incident at a certain incident angle, by periodically arranging reflection control regions with a common reflection direction, the reflect array can be given the property of reflecting in a single direction. Also, when electromagnetic waves of a certain wavelength are incident at a certain incident angle, by configuring a reflect array that includes reflection control regions with different reflection directions, the property of scattering electromagnetic waves in multiple directions can also be given. Further, by configuring the reflection direction to be shifted by a predetermined angle for each reflection control region, the property of concentrating electromagnetic waves at a specific location can also be given. During design, the frequency planned to be applied to the reflect array is hereinafter referred to as the "operating frequency".

[0027] The size Lx of the reflection control region in the x-axis direction is determined, for example, by Equation (3) 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 。

Number

[0028] Also, the size Ly of the reflection control region in the y-axis direction is determined, for example, by Equation (4) 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

Number

[0029] Particularly, when not distinguishing the xy-axis components of Equation (3) and Equation (4), it is expressed as in Equation (1) described above

Number

[0030] (Relationship between unit cell and reflection phase) Referring to FIGS. 4 and 5, the relationship between the unit cell and the reflection phase will be described. FIGS. 4 and 5 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 FIG. 5 are the same as those of (a) and (b) in FIG. 4.

[0031] 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.

[0032] 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 in the reflection control region 5a (FIG. 4(b)). The reflection control region 5a has a division number n = 3 and three unit cells arranged in the x-axis direction. The size (long side) Lx of the reflection control region 5a in the x-axis direction is determined by Equation (3), and the size of the unit cell in the x-axis direction is Lx / 3. Since the y-axis component of the reflection angle is symmetric reflection, the size My of the short side of the reflection control region 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 m is used, and My is made equal to Lx / 3.

[0033] 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 m = 3 and has three unit cells arranged in the y-axis direction. The size Ly of the reflection control region 5b in the y-axis direction is determined by Equation (4), 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, the size Mx of the short side of the reflection control region can take any value. However, for ease of design, for the sake of convenience, a square unit cell whose size is determined from Ly and the number of divisions m is used, and Mx is made equal to Ly / 3.

[0034] (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, to follow Equation (5). Here, let the wavelength of the operating frequency be λ (m), 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, the y-axis component be θry, the reflection phases at arbitrary coordinates x1 and x2 parallel to the x-axis within the reflection control region be φx1 and φx2 respectively, the distance between the coordinates x1 and x2 be dx, and the reflection phase difference between Φx1 and Φx2 be ΔΦx. Also, let the reflection phases at arbitrary coordinates y1 and y2 parallel to the y-axis be φy1 and φy2 respectively. When attempting to cause the reflection control region to perform asymmetric reflection along the x-axis direction, it is preferable to satisfy Equation (5), and when attempting to cause the reflection control region to perform asymmetric reflection along the y-axis direction, it is preferable to satisfy Equation (6).

Equation

Equation

[0035] Alternatively, 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 (7) and Equation (8). 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 η1 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, k1 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 (7). When attempting to cause asymmetric reflection along the y-axis direction in the reflection control region, it is preferable to satisfy Equation (8). [Number] [Number]

[0036] As other distributions of the surface impedance, they are represented by, for example, Equation (9) and Equation (10). When attempting to cause the reflection control region to perform asymmetric reflection only along the x-axis direction, it is preferable to satisfy Equation (9). When attempting to cause the reflection control region to perform asymmetric reflection only along the y-axis direction, it is preferable to satisfy Equation (10). [Number] [Number]

[0037] Note that, from the above formula (5) to formula (10), it shows an example of the design formula used when designing the distribution of the reflection phase and the distribution of the surface impedance. The present disclosure is not limited to the case of using these formulas (5) to formula (10), and other design formulas can be appropriately selected.

[0038] (Method for designing a reflectarray) A method for designing a reflectarray will be described. Here, as an example, a method for designing a reflectarray in which a plurality of the same reflection control regions are arranged in the x-axis direction will be described. The same method can be used to design a reflectarray in which a plurality of the same reflection control regions are arranged in the y-axis direction or a reflectarray that attempts to perform asymmetric reflection in either the x-axis direction or the y-axis direction.

[0039] (Design method 1) In Design method 1, it is a design method of controlling the phase of the element pattern by fixing the element length and the gap between the element patterns and changing the element width. In this method, compared with Design methods 2 and 3 described later, the change in phase accompanying the change in element width is gentle, so there is an advantage that it is easy to ensure the performance of the product even if the element shape changes during the manufacturing process. (Step 1) First, set the target reflection characteristics (operating frequency, incident angle, and reflection angle). (Step 2) Subsequently, use formula (3) to determine the size Lx of the reflection control region. (Step 3) Subsequently, divide the size Lx of the reflection control region into n parts. The size of the unit cell is determined. (Step 4) Subsequently, within the range that fits into the unit cell, determine the element length lx of the element pattern. Since the element patterns are evenly arranged without bias within the unit cell, as a result, the gap gx between the element patterns is also determined. (Step 5) Subsequently, analyze the reflection phase of the unit cell with the element width wx as a design parameter. Derive the reflection phase with the element width wx of the element pattern as a design parameter, and obtain an analysis result showing the relationship between the element width and the reflection phase in the unit cell. (Step 6) Subsequently, an ideal reflection phase or impedance for realizing the reflection characteristics of the target reflection control region is calculated using Equations (5) to (10), and an element width wx for realizing a desired reflection phase or impedance is selected based on the above analysis results. (Step 7) Subsequently, a reflectarray is formed to include at least one reflection control region. The reflection characteristics of the reflectarray are analyzed. (Step 8) Note that based on the analysis results in Step 7, it is also possible to further finely adjust the element width wx 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.

[0040] (Design Method 2) Design Method 2 is a design method for controlling the phase of the element pattern by fixing the element width and changing the element length. (Step 1) First, set the target reflection characteristics (operating frequency, incident angle, and reflection angle). (Step 2) Subsequently, using Equation (3), determine the size Lx of the reflection control region. (Step 3) Subsequently, divide the size Lx of the reflection control region into n parts. The size of the unit cell is determined. (Step 4) Subsequently, within the range that fits into the unit cell, determine the element width wx of the element pattern. (Step 5) Subsequently, analyze the reflection phase of the unit cell with the element length lx as a design parameter. The reflection phase is derived with the element length lx of the element pattern as a design parameter, and an analysis result showing the relationship between the element length and the reflection phase in the unit cell is obtained. (Step 6) Subsequently, an ideal reflection phase or impedance for realizing the reflection characteristics of the target reflection control region is calculated using Equations (5) to (10), and an element length lx for realizing a desired reflection phase or impedance is selected based on the above analysis results. (Step 7) Subsequently, a reflectarray is formed to include at least one reflection control region. The reflection characteristics of the reflectarray are analyzed. (Step 8) Based on the analysis results of Step 7, it is also possible to further finely adjust the element length lx 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.

[0041] (Design Method 3) Design Method 3 is a design method for controlling the phase of the element pattern by changing both the element width and the element length. This design method is effective when a sufficient reflection phase change width cannot be ensured by Design Methods 1 and 2. (Step 1) First, set the target reflection characteristics (operating frequency, incident angle, and reflection angle). (Step 2) Subsequently, use Equation (3) to determine the size Lx of the reflection control region. (Step 3) Subsequently, divide the size Lx of the reflection control region into n parts. The size of the unit cell is determined. (Step 4) Subsequently, analyze the reflection phase of the unit cell with the element width wx and the element length lx as design parameters. Derive the reflection phase with the element width wx and the element length lx of the element pattern as design parameters, and obtain the analysis results showing the relationship between the element width wx, the element length lx, and the reflection phase in the unit cell. (Step 5) Subsequently, calculate the ideal reflection phase or impedance for realizing the reflection characteristics of the target reflection control region using Equations (5) to (10), and select the element width wx and the element length lx that realize the desired reflection phase or impedance based on the above analysis results. (Step 6) Subsequently, form a reflectarray so as to include at least one reflection control region. Analyze the reflection characteristics of the reflectarray. (Step 7) Based on the analysis results of Step 7, it is also possible to further finely adjust the element width wx and the element length lx 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.

[0042] (Element Pattern) Referring to FIGS. 1, 6, and 7, the details of the element pattern will be described. Here, a detailed description regarding the cross-patch shape will be given, but the element pattern shape is not limited thereto. For example, it may be a circular shape, a rectangular shape, or a square shape. Generally, a reflectarray changes the reflection characteristics by utilizing the resonance of the element pattern. Here, since a linear or rectangular element pattern (square patch) mainly resonates the polarization in the 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.

[0043] In the reflectarray of the present disclosure, as the number of divisions n, 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 the size of the element pattern that is constant with respect to the frequency is satisfied, when n, m are increased beyond a certain level, it becomes difficult to realize asymmetric reflection at the operating frequency. On the other hand, as n, m increase, the reflection characteristics can be controlled for each finer region, so the reflection characteristics of the reflectarray approach the theoretical characteristics.

[0044] The element pattern in the reflectarray of the present disclosure includes, in the xy plane, a cross-patch having a shape in which two square patches are orthogonal. Here, as shown in FIG. 1b, the square patch having a long side in the x-axis direction constituting the cross-patch has an element length lx which is the size of the long side and an element width wy which is the size of the short side, and the square patch having a long side in the y-axis direction has an element length ly which is the size of the long side and an element width wx which is the size of the short side. Therefore, it is possible to represent that the element pattern in the unit cell 4n has lxn, lyn as the element lengths and wxn, wyn as the element widths.

[0045] FIG. 6 is a diagram showing the configuration of the element pattern. One element pattern is arranged in a unit cell. For the cross patch constituting the element pattern of the unit cell 4, the position where the two rectangular patches intersect may be the same as the center of gravity of the unit cell (unit cell 4a in FIG. 6(a)), or may be different (unit cell 4b in FIG. 6(b), unit cell 4c in FIG. 6(c)). These deformations of the cross patch can be appropriately selected, and the design flexibility and expandability can be enhanced.

[0046] 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 different element widths from each other. The element width wx varies within a range up to a maximum value equal to the element length lx, and the element width wy can be varied within a range up to a maximum value equal to the element length ly. 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 controlled individually.

[0047] 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 also equal for each element pattern. Here, lx and ly may be equal or different. When lx and ly are different, the characteristics for TE and TM polarized waves can be individually imparted to each element pattern.

[0048] 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 oxide - zinc oxide (IZO), aluminum - doped zinc oxide (AZO), gallium - doped zinc oxide (GZO), antimony - doped tin oxide (ATO), 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 preferred. Also, by using ITO or a mixture of polyethylenedioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT / PSS), a reflective array having transparency can be fabricated. 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.

[0049] The material of the element pattern may be the same as that of the ground layer described later or may be a different material. For example, it is also possible that at least one of the ground layer or 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, it becomes easier to install the reflective array on a curved surface, etc., and weight reduction can be achieved.

[0050] Examples of the form of using the above materials include a continuous film, a mesh shape, and a punching shape.

[0051] Here, a mesh refers to a state where mesh-like through-holes (openings) are formed in the plane of a conductor. When the conductor is formed in a mesh shape, the mesh openings may be square or rhombic. When forming the mesh openings into 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 using a random shape, moiré can be prevented. When processing a metal into a mesh shape, methods such as punching of a metal plate and etching of a metal plate can be adopted.

[0052] 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.

[0053] 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, and more preferably 6 μm or more and 15 μm or less. The line pitch of the mesh is preferably 50 μm or more and 500 μm or less, and more preferably 100 μm or more and 300 μm or less. Also, when the wavelength at the operating frequency is λ, the line pitch 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 pitch of the mesh is 0.5×λ or less, the performance can be ensured. Also, the line pitch of the mesh may be 0.001×λ or more.

[0054] 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.

[0055] 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.

[0056] When the form of the element pattern is formed using a thin film, its thickness is preferably greater than twice the skin depth calculated from Equation (11). Here, 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. If the thickness is less than twice the skin depth calculated from Equation (11), part of the electromagnetic wave incident on the conductor will transmit through, and the reflection efficiency will deteriorate. Furthermore, more preferably, the thickness is greater than twice the skin depth calculated from Equation (11) and is close to that value. An element pattern having a thickness sufficiently greater than twice the skin depth calculated from Equation (11) will cause the current to concentrate on the surface portion of the conductor due to the skin effect, and almost no current will flow in the central portion. Therefore, even if the thickness is greater than twice the skin depth of Equation (11), the power transmission characteristics will not change significantly. The closer the value is to twice the skin depth calculated from Equation (11), the more sufficient power transmission characteristics can be provided, and the production can be achieved while suppressing the material cost.

Number

[0057] In addition, in order to enhance the reflection efficiency of the electromagnetic wave, reducing the loss caused by the element pattern can be mentioned. Therefore, the surface roughness of the element pattern is preferably small. At high frequencies, due to the influence of the skin effect, the current concentrates on the surface portion of the conductor, and the current density on the conductor surface becomes high. Therefore, it is easily affected by the surface roughness, and when the surface roughness is large, the conductor loss becomes large. In particular, when the surface roughness is greater than the skin depth, the conductor loss becomes significantly large. Therefore, in order to suppress the conductor loss, it is preferable that the surface roughness is small.

[0058] (Dielectric layer) For the dielectric layer, in addition to a single resin, the use of composite materials in which paper, glass fiber, carbon fiber, etc. are impregnated with resin can be mentioned.

[0059] 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 desired reflection phase characteristics in the reflect array 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 reflect array 1 with less dielectric loss can be manufactured.

[0060] Examples of the single resin include polyethylene (εr = 2.2 to 2.4), polypropylene (εr = 2.0 to 2.6), polystyrene (εr = 2.4 to 2.6), polyvinyl chloride (εr = 2.8 to 8.0), AS resin (εr = 2.6 to 3.1), ABS resin (εr = 2.4 to 4.1), polyethylene terephthalate (εr = 2.9 to 3.0), acrylic resin (εr = 2.7 to 4.5), urethane resin (εr = 4.0 to 7.1), epoxy resin (εr = 2.5 to 6.0), nylon (εr = 3.0 to 5.0), polyimide (εr = 2.4 to 2.7), fluororesin (εr = 2.0 to 2.6), polycarbonate (εr = 2.9 to 8.9), polyphenylene ether (εr = 2.8 to 8.2), polyphenylene sulfide (εr = 3.2 to 4.6), polyvinylidene fluoride (εr = 6.4 to 10.0), polyethylene naphthalate (εr = 2.9), phenol resin (εr = 3.0 to 12.0), cycloolefin polymer (εr = 2.3 to 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. Also, as the foam, a foam with high flexibility is preferably used.

[0061] Examples of the composite material include composite materials such as paper / phenol resin, paper / epoxy resin, glass / epoxy resin, and glass / fluororesin.

[0062] From the perspective of permittivity adjustment, the use of resin components or a mixture containing a dielectric compound and a resin component can be mentioned. The relative permittivity in the mixture can be adjusted according to the selection of the dielectric compound and its content.

[0063] 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 shown by the relational expression of Equation (12).

Equation

[0064] 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.

[0065] When a dielectric having transparency is used, the reflectarray exhibits visible light transmissibility, making it possible to maintain the landscape after installation.

[0066] 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, making it difficult to design the reflectarray 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, and the total thickness of the reflectarray becomes thick, making it difficult to save space. For this reason, the thickness of the dielectric layer is preferably 250 μm or less. When the design frequency is 60 GHz, the thickness of the dielectric layer is preferably 10 μm or more and 250 μm or less. When the design frequency is 100 GHz or more, when the thickness of the dielectric layer is about several μm or more and 100 μm or less, it is easy to design the reflectarray.

[0067] The dielectric layer can be formed using, for example, wet coating methods such as die coating, comma coating, and 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, etc. Also, a coextrusion method in which a plurality of resins are extruded in multiple layers to form a film may be used.

[0068] (Ground layer) The ground layer is provided to reflect electromagnetic waves reaching the reflect array. 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.

[0069] For example, as the inorganic oxide material and the metal material, indium tin oxide (ITO), indium zinc oxide (IZO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), antimony-doped tin oxide (ATO), Ag, Al, Au, Pt, Pd, Cu, Co, Cr, In, Ag-Cu, Cu-Au, and Ni, etc. are used. Also, 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, graphene, etc. Particularly from the viewpoints of material cost, conductivity, and film formability, Cu and Al are preferred. 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 transparent reflect array can also be produced by using ITO or a mixture of polyethylenedioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT / PSS), etc.

[0070] Examples of the form of using the above materials include a continuous film, a mesh shape, a punching shape, and a periodic structure.

[0071] Here, a mesh refers to a state where a conductor plane has mesh-shaped through-holes (openings). When the conductor is formed in a mesh shape, the mesh openings may be square or diamond-shaped. 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 the self-organization method may be used. By making it a random shape, moiré can be prevented. When processing the metal into a mesh shape, it is possible to adopt methods such as punching of a metal plate and etching of a metal plate.

[0072] When the ground layer is in a mesh shape or when a transparent conductive material is used, the reflect array exhibits visible light transmittance, making it possible to maintain the landscape after installation.

[0073] 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. 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.

[0074] 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 inkifying the metal material, 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.

[0075] 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 reflectarray, thereby enabling use on a curved surface and implementing a roll-to-roll production process.

[0076] When the form of the ground layer is a thin film, its thickness is preferably larger than the skin depth calculated from Equation (11) as in the case of the element pattern.

[0077] In addition, in order to enhance the reflection efficiency of electromagnetic waves, reducing the loss due to the ground layer can be mentioned. Therefore, it is preferable that the surface roughness of the ground layer is small.

[0078] 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 becomes possible to reflect only a specific frequency, so that a function of transmitting frequencies other than the operating frequency can be imparted. Also, 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.

[0079] (Manufacturing Method) As the main manufacturing methods for the basic configuration of the reflectarray, for a copper-clad laminate used for a printed circuit board or the like, or a dielectric layer having a metal film formed on one or both sides thereof by dry coating such as vapor deposition or sputtering, plating, or wet coating, etc., an element pattern is formed by performing cutting or etching, etc. Specifically, a copper-clad laminate is, for example, a copper foil bonded 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 side's 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 a dielectric, element pattern 1 is formed from one metal film, and the other metal film is applied to the ground layer 3. The dielectric becomes dielectric layer 2.

[0080] FIG. 7 is a diagram showing an example of the shape of the element pattern after etching. FIG. 7(a) shows a plan view of element pattern 1, and FIGS. 7(b) to 7(d) show cross-sectional views of element pattern 1. As shown in FIG. 7(a), element pattern 1 is formed by orthogonally arranging a rectangular patch having an element length lx and an element width wy and a rectangular patch having an element length ly and an element width wx. Either a dry etching method or a wet etching method may be used for the etching method. When the etching method is used, corner rounding (FIG. 7(a)) or pinholes may occur in element pattern 1. Also, in a cross-sectional view of element pattern 1, a forward taper (FIG. 7(b)), a reverse taper (FIG. 7(c)), or rounding (FIG. 7(d)) is assumed to be formed. Let the thickness of element pattern 1 in FIG. 7 be 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 force with the functional layer when laminating the functional layer described later.

[0081] Note that generally in the case of cutting, the dimensional error of the element pattern is about ±100 μm, and in the case of etching, the dimensional error of the element pattern is about ±50 μm.

[0082] Other manufacturing methods include a method of directly forming an element pattern or a ground layer on a dielectric layer. Examples include methods of printing using relief printing, lithography, intaglio printing, screen printing, transfer printing, etc., and methods of masking portions other than the element pattern portion on the dielectric layer with masking tape, masking agent, etc., and forming the element pattern by using dry coating, plating, painting, or spraying methods.

[0083] In the lamination of other layers (functional layers such as protective layers, adhesive layers, design layers, and installation layers) to the basic structure, examples include bonding, printing / coating, and extrusion molding. For bonding, examples include using dry lamination, wet lamination, thermal lamination, and extrusion lamination, but it is not limited thereto.

[0084] (Relationship between incident angle and reflection angle) The incident angle is the incident angle θi of the electromagnetic wave incident on the reflection control region, and the reflection angle is the reflection angle θr of the electromagnetic wave reflected from the reflection control region. When the wavelength of the electromagnetic wave reflected from the reflection control region is λ, the reflection control region is designed to satisfy the following formula (1).

Number

[0085] The reflection angle in the reflect array needs to satisfy formula (2).

Number

[0086] (Incident acceptance angle range) The incident deviation angle indicates the incident angle when a deviation from the incident angle that satisfies Equation (1) occurs, with the incident angle that satisfies Equation (1) as the reference (= 0°). The angular expression for the incident deviation angle is based on the incident angle that satisfies Equation (1) (= 0°), where the direction toward the +z axis is a positive angle (from 0° to -180°), and the direction toward the -z axis is a negative angle (from 0° to -180°). Also, the incident allowable angle range represents the angular width of the incident deviation angle within which the reflection intensity of the electromagnetic wave reflected by the reflection control region from the incident deviation angle to the reflection angle is within -3 dB, with the reflection intensity of the electromagnetic wave reflected by the reflection control region from the incident angle that satisfies Equation (1) to the reflection angle that satisfies Equation (1) as the reference (= 0 dB). -3 dB indicates that the power is halved compared to the reference. The -3 dB reference is used as a reference for indicating directivity in the antenna industry, and communication is considered to be sufficiently possible within that range. The reflectarray can increase the incident allowable angle range as the absolute value of the incident angle |θi| increases. Also, in the range where the absolute value of the incident angle |θi| is large, the incident allowable angle range is larger when the incident deviation angle is a positive value, and a wider incident allowable angle range can be ensured. This is thought to be because the apparent area of the reflectarray as seen from the transmitter becomes smaller, so the amount of energy hitting the reflectarray is small, and the accompanying reflected power becomes small. The incident allowable angle range Δθi is preferably greater than 5.5° and less than or equal to 16°. In the case of an incident allowable angle range smaller than 5.5°, it is necessary to accurately grasp the direction of the electromagnetic wave radiated from the transmitter. Also, when using an antenna with beamforming at the transmitter, more antenna elements need to be arranged to increase the angular accuracy of the beamforming, leading to an increase in the area and cost of the transmitter. Also, if the incident allowable angle range is 16° or more, radio wave sources other than the transmitter may be reflected, which may cause phase disturbances.

[0087] (Electromagnetic Wave Reflection System) Referring to FIG. 8, an example of an electromagnetic wave reflection system and a method for installing a reflectarray will be described. FIG. 8 is a diagram showing an example of an electromagnetic wave reflection system using a reflectarray. For ease of explanation, FIG. 8 is taken as an example for description, but the usage environment of the electromagnetic wave reflection system is not limited to this. As shown in the example of FIG. 8, when there is an obstacle 500, the electromagnetic wave radiated from the transmitter is blocked by the obstacle or the like and cannot reach the receiver directly. Since the higher the frequency of the electromagnetic wave, the higher its directivity, it becomes difficult for the electromagnetic wave to reach the back side of the obstacle by bypassing it. Here, by using a reflectarray, the electromagnetic wave primarily radiated from the transmitter hits the reflectarray, and the electromagnetic wave secondarily radiated from the reflectarray hits the receiver, thereby enabling the electromagnetic wave to reach from the transmitter to the receiver. Generally, when using a passive reflector, when constructing an electromagnetic wave reflection system, the usage environment is confirmed in advance, the installation location, incident angle, and reflection angle of the passive reflector are calculated, and based on this, the passive reflector is designed. In this case, if the prior confirmation is not accurate, the maximum effect cannot be exerted. Also, when installing the passive reflector, accurate angle adjustment is required. Here, by using the reflectarray of the present disclosure, within the range of the incident angle and reflection angle that satisfy Equation (2), even if an incident deviation angle occurs, the electromagnetic wave incident on the reflectarray can be reflected in the direction of the reflection angle, and a wide incident allowable angle range can be obtained, so that the construction of the electromagnetic wave reflection system becomes easy.

[0088] (Method for Installing Reflectarray) The installation location of the reflect array is preferably along a wall or the like because it does not take up installation space. Specifically, in FIG. 8, installation on wall 200 and wall 201 is assumed. Let the reflect array installed on wall 200 be 61 and the reflect array installed on wall 201 be 62. The reflect array 61 is an installation method that satisfies formula (2), and the reflect array 62 is an installation method that does not satisfy formula (2). The installation method of the reflect array 62 requires high precision to determine the positional relationship between the transmitter and the reflect array 62. When a deviation occurs in the installation position, the power that the receiver can receive will change significantly. By installing the reflect array 61 on wall 200, the incident acceptance angle range becomes wider, and electromagnetic waves incident from this angle range can be reflected toward the receiver with a stable reflection intensity. Considering practical use, for example, the installation position accuracy of the reflect array during construction is relaxed, and the construction becomes easier. Also, when using an antenna with beamforming for the transmitter, an effect can be expected that the accuracy of beamforming can also be relaxed.

[0089] (Support) The reflect array is installed on a support. FIG. 9 is a diagram showing an example of a reflect array installed on a support. As the support, an existing signboard, wall, ceiling, window glass, etc. may be used, or a new panel or pole may be installed. Because it does not take up installation space, it is preferably used by attaching it to an existing signboard, wall, ceiling, window glass, etc. as shown in FIG. 9(a). Furthermore, in order to harmonize with the space, a design layer can be provided, or transparency can be imparted by making the elements and the ground layer into a mesh. Also, when newly installing a panel or pole as shown in FIG. 9(b), it is preferably provided with a mechanism capable of adjusting the angle of the reflect array in the vertical or horizontal direction, and more preferably provided with a mechanism capable of moving the position of the reflect array vertically and horizontally. The reflect array is installed on the support and used as a reflect array device.

[0090] (Installation layer) The setting layer is a layer for fixing the reflect array 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.

[0091] (Design layer) The design layer is a layer for imparting design properties to the surface of the reflect array. 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 functions of the protective layer described later may be imparted to the design layer.

[0092] (Protective layer) For the protective layer, in order to prevent oxidation 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.

[0093] 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.

[0094] [Evaluation results (Examples and Comparative Examples)] Regarding Examples 1-4 and Comparative Examples 1-4, the results are summarized in Table 1, and regarding Examples 5-10 and Comparative Examples 5-10, the results are summarized in Table 2. The comparative examples used here compare the cases where the same reflect array satisfies and does not satisfy Equation (2) in order to show that the reflect array of the present disclosure has a wide incident acceptance angle range at a specific incident angle. The ease of installation of Table 1 and Table 2 is an index indicating how much installation error of the reflect array is allowed. When the distance between the transmitter and the reflect array is 5 m, if the received power decreases by within -3 dB even when the reflect array is moved by 45 cm, it is marked as ○, and if the received power decreases by more than -3 dB, it is marked as ×. When the reflect array is moved, in the case of a reflector that asymmetrically reflects in the x-axis direction, it shall be translated parallel to the x-axis. The reception stability is an index indicating the stability of the received power at the reflection angle that satisfies Equation (1) when the transmitter is moved. The transmitter is moved so that the incident deviation angle changes, and when the angle width (i.e., the incident allowable angle range) when the received power at the reflection angle reaches -3 dB is 5.5° or less, it is judged as ×, indicating a state where the received power is unstable, and when it is greater than 5.5° and 16° or less, it is judged as ○, indicating a state where the received power is stable.

Table 1

Table 2

[0095] (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 / fluororesin with a thickness of 0.764 mm was used for the dielectric layer 2. However, the conductivity of the copper was 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.

[0096] The operating frequency was set to 28 GHz, the target reflection characteristics (the desired reflection characteristics) were set to θix = -45°, θrx = 0°, θiy = θry = 0°, and the size Lx in the x-axis direction of the reflection control region 5 was determined to be 15.142 mm using Equation (3).

[0097] 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 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, in each element pattern within the reflection control region 5, the element length and element width were different, and within the same element pattern, the element lengths and element widths in the x-axis direction and y-axis direction were the same. Specifically, the element lengths were set as lx1 = ly1, lx2 = ly2, lx3 = ly3, and the element widths were set as wx1 = wy1, wx2 = wy2, wx3 = wy3. 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.

[0098] The reflection phases of the unit cell with respect to the element width w and element length l were analyzed using finite element method analysis software (HFSS) manufactured by Ansys. It was confirmed that the reflection phase changed as the element width w or element length l changed when the element width w or element length l was 1.400 mm.

[0099] Next, based on the analysis results of the reflection phases of the unit cells obtained above, the element length l in each unit cell was determined to follow the impedance distribution of Equation (9). The element lengths were lx1 = ly1 = 3.800 mm, lx2 = ly2 = 3.000 mm, lx3 = ly3 = 1.400 mm, and the element widths were wx1 = wy1 = 1.400 mm, wx2 = wy2 = 1.400 mm, wx3 = wy3 = 1.100 mm, respectively.

[0100] The reflect array 6 has 8×6 reflection control regions arranged in the x-axis and y-axis directions, and the size in the xy plane is 121.12 mm × 90.840 mm. The reflection characteristics were analyzed using HFSS when the reflect array 6 was irradiated with a polarization parallel to the y-axis at θix = -45° and θrx = 0°.

[0101] In order to grasp the incident allowable angle range, the same analysis was also performed when changing at 2° intervals in the range of -65° ≤ θix ≤ -25°.

[0102] Figure 10 shows the analysis results of the reflect array 6 obtained in Example 1. However, the horizontal axis in Figure 10 is the reflection angle θrx, and the vertical axis is the RCS (radar cross section). The RCS is a value corresponding substantially to the intensity of the reflected wave. In the reflect array 6 of Example 1, the electromagnetic wave incident at θix = -45° was reflected in the desired direction of θrx = 0°, and its RCS was -0.02 dBsm.

[0103] (Comparative Example 1) A reflect array that is the same as the reflect array described in Example 1 except for the incident angle θix and the reflection angle θrx was prepared. The incident angle θix and the reflection angle θrx were θix = 0° and θrx = -45°, respectively. The reflection characteristics of the reflect array 6 were analyzed using HFSS.

[0104] In order to grasp the incident allowable angle range, the same analysis was also performed when changing at 2° intervals in the range of -20° ≤ θix ≤ 20°.

[0105] Figure 11 shows the analysis results of the reflect array 6 obtained in Comparative Example 1. In the reflect array 6 of Example 1, the electromagnetic wave incident at θix = 0° was reflected in the desired direction of θrx = -45°, and its RCS was -0.28 dBsm.

[0106] Figure 12 shows the comparison results of the power change amount that can be received at a specific reflection angle θrx when changing the incident angles of Example 1 and Comparative Example 1 respectively. The horizontal axis in Figure 12 is the incident deviation angle, and the vertical The axis was defined as the amount of change in RCS when the RCS at an incident misalignment angle of 0° was set to 0 dB. Specifically, in Example 1, when the incident misalignment angle = 0°, θix = -45°, and the angles when -65° ≤ θix ≤ -25° were changed are shown on the horizontal axis of FIG. 12 for -20° ≤ incident misalignment angle ≤ 20°. The vertical axis shows how much the RCS has changed compared to when the incident misalignment angle = 0°, with the RCS (-0.02 dBsm) at θrx = 0° set to 0 dB. This is equivalent to showing how much the received power has changed at the reflection angle location. Also, in Comparative Example 1, when the incident misalignment angle = 0°, θix = 0°, and the angles when -20° ≤ θix ≤ 20° were changed are shown on the horizontal axis of FIG. 12 for -20° ≤ incident misalignment angle ≤ 20°. The vertical axis shows how much the RCS has changed compared to when the incident misalignment angle = 0°, with the RCS (-0.28 dBsm) at θrx = -45° set to 0 dB. Also, the dotted line at -3 dB is a line indicating the specification of the incident allowable angle range.

[0107] From the results of FIG. 12, the incident allowable angle ranges were 6.2° for Example 1 and 4.2° for Comparative Example 1. As a result of checking the ease of installation, in Example 1, even when the reflectarray moved 45 cm, the change in received power was within -3 dB in the direction of the received angle that satisfied Equation (1), while in Comparative Example 1, the change was greater than -3 dB. Also, as a result of checking the reception stability, in Example 1, the received power was stable in a range where the incident allowable angle range was greater than 5.5°, while in Comparative Example 1, the received power was not stable in a range where the incident allowable angle range was 5.5° or less.

[0108] (Example 2) A reflectarray 6 with a basic configuration was constructed 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 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.

[0109] The operating frequency was set to 28 GHz, the target reflection characteristics (the desired reflection characteristics) were set to θix = -50°, θrx = 0°, θiy = θry = 0°, and the size Lx in the x-axis direction of the reflection control region 5 was determined to be 13.977 mm using Equation (3).

[0110] 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 4.659 mm. The shape of the element pattern was a cross-patch in which two square patches were orthogonal in the xy plane. Here, in each element pattern within the reflection control region 5, the element length and element width were different, and within the same element pattern, the element lengths and element widths in the x-axis and y-axis directions were the same. Specifically, the element lengths were set to lx1 = ly1, lx2 = ly2, lx3 = ly3, and the element widths were set to wx1 = wy1, wx2 = wy2, wx3 = wy3.

[0111] The reflection phase of the unit cell with respect to each of the element width w and element length l was analyzed using finite element method analysis software (HFSS) manufactured by Ansys. It was confirmed that the reflection phase changes as the element width w or element length l changes.

[0112] Next, based on the analysis results of the reflection phase of the unit cell obtained above, the element length l in each unit cell was determined to follow the impedance distribution of Equation (9). The element lengths were lx1 = ly1 = 3.790 mm, lx2 = ly2 = 2.775 mm, lx3 = ly3 = 2.065 mm, respectively, and the element widths were wx1 = wy1 = 2.303 mm, wx2 = wy2 = 2.217 mm, wx3 = wy3 = 2.024 mm, respectively.

[0113] The reflectarray 6 was arranged with 8 × 6 in the x-axis and y-axis directions of the reflection control region, and the size in the xy plane was 111.816 mm × 27.954 mm. The reflection characteristics when the reflectarray 6 was irradiated with a polarization parallel to the y-axis at θix = -50° and θrx = 0° were analyzed using HFSS.

[0114] In order to grasp the incident allowable angle range, the same analysis was also performed when the angle was changed at 2° intervals within the range of -70° ≤ θix ≤ -30°.

[0115] Figure 13 shows the analysis results of the reflectarray 6 obtained in Example 2. However, the horizontal axis in Figure 13 is the reflection angle θrx, and the vertical axis is the RCS. In the reflectarray 6 of Example 2, the electromagnetic wave incident at θix = -50° was reflected in the desired direction of θrx = 0°, and its RCS was -1.82 dBsm.

[0116] (Comparative Example 2) A reflectarray that is the same as the reflectarray described in Example 2 except for the incident angle θix and the reflection angle θrx was prepared. The incident angle θix and the reflection angle θrx were set to θix = 0° and θrx = -50°, respectively. The reflection characteristics of the reflectarray 6 were analyzed using HFSS.

[0117] In order to grasp the incident allowable angle range, the same analysis was also performed when the angle was changed at 2° intervals within the range of -20° ≤ θix ≤ 20°.

[0118] Figure 14 shows the analysis results of the reflectarray 6 obtained in Comparative Example 2. In the reflectarray 6 of Example 2, the electromagnetic wave incident at θix = 0° was reflected in the desired direction of θrx = -50°, and its RCS was -1.89 dBsm.

[0119] Figure 15 shows the comparison results of the power change amount that can be received at a specific reflection angle θrx when the incident angles of Example 2 and Comparative Example 2 are changed.

[0120] From the results of FIG. 15, the incident acceptance angle ranges were 7.4° for Example 2 and 4.5° for Comparative Example 2. As a result of checking the ease of installation, in Example 2, even when the reflect array moved 45 cm, the change in received power was within -3 dB in the direction of the received angle that satisfied Equation (1), whereas in Comparative Example 2, the change was greater than -3 dB. Further, as a result of checking the reception stability, in Example 2, the received power was stable in a range where the incident acceptance angle range was greater than 5.5°, whereas in Comparative Example 2, the received power was not stable in a range where the incident acceptance angle range was 5.5° or less.

[0121] (Example 3) A reflect array 6 with 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 a composite material of glass / fluororesin with a thickness of 0.764 mm was used for the dielectric layer 2. However, the conductivity of the copper was 5.8×10^7 siemens / m, the real part of the relative dielectric constant of the dielectric layer 2 was 2.6, and tanδ was 0.0025.

[0122] The operating frequency was set to 28 GHz, the target reflection characteristics (the intended reflection characteristics) were set to θix = -60°, θrx = 0°, θiy = θry = 0°, and the size Lx in the x-axis direction of the reflection control region 5 was determined to be 12.363 mm using Equation (3).

[0123] 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 4.121 mm. The shape of the element pattern was a cross-patch in which two square patches were orthogonal in the xy plane. Here, in each element pattern within the reflection control region 5, the element length and element width were different, and within the same element pattern, the element lengths and element widths in the x-axis and y-axis directions were the same. Specifically, the element lengths were lx1 = ly1, lx2 = ly2, lx3 = ly3, and the element widths were wx1 = wy1, wx2 = wy2, wx3 = wy3.

[0124] The reflection phase of the unit cell with respect to each of the element width w and the element length l was analyzed using finite element method analysis software (HFSS) manufactured by Ansys. It was confirmed that the reflection phase changed as the element width w or the element length l changed.

[0125] Next, based on the analysis results of the reflection phase of the unit cell obtained above, the element length l in each unit cell was determined so as to follow the impedance distribution of Equation (9). The element lengths l were lx1 = ly1 = 2.051 mm, lx2 = ly2 = 3.614 mm, lx3 = ly3 = 2.815 mm, respectively, and the element widths were wx1 = wy1 = 1.427 mm, wx2 = wy2 = 1.521 mm, wx3 = wy3 = 1.699 mm, respectively.

[0126] The reflectarray 6 was arranged with 8 × 6 reflection control regions in the x-axis and y-axis directions, and the size in the xy plane was 98.904 mm × 24.726 mm. The reflection characteristics were analyzed using HFSS when irradiating the reflectarray 6 with a polarization parallel to the y-axis at θix = -60° and θrx = 0°.

[0127] In order to grasp the incident acceptance angle range, the same analysis was also performed when changing at 2° intervals in the range of -80° ≤ θix ≤ -40°.

[0128] FIG. 16 shows the analysis results of the reflectarray 6 obtained in Example 3. However, the horizontal axis in FIG. 16 is the reflection angle θrx, and the vertical axis is the RCS. In the reflectarray 6 of Example 3, the electromagnetic wave incident at θix = -60° was reflected in the desired direction of θrx = 0°, and its RCS was -6.14 dBsm.

[0129] (Comparative Example 3) A reflectarray similar to the reflectarray described in Example 3 except for the incident angle θix and the reflection angle θrx was prepared. The incident angle θix and the reflection angle θrx were θix = 0° and θrx = -60°, respectively. The reflection characteristics of the reflectarray 6 were analyzed using HFSS.

[0130] In order to grasp the incident acceptance angle range, the same analysis was also performed when changing at 2° intervals in the range of -20° ≤ θix ≤ 20°.

[0131] Figure 16 shows the analysis results of the reflectarray 6 obtained in Comparative Example 3. In the reflectarray 6 of Example 3, the electromagnetic wave incident at θix = 0° was reflected in the desired direction of θrx = -60°, and its RCS was -6.22 dBsm.

[0132] Figure 17 shows the comparison results of the power change amount that can be received at a specific reflection angle θrx when the incident angles of Example 3 and Comparative Example 3 are changed.

[0133] From the results of Figure 18, the incident angle tolerance range was 10.8° for Example 3 and 5.1° for Comparative Example 3. As a result of checking the ease of installation, in Example 3, even when the reflectarray moved 45 cm, the change in received power was within -3 dB in the direction of the received angle that satisfies Equation (1), while in Comparative Example 3, the change was greater than -3 dB. Also, as a result of checking the reception stability, in Example 3, the received power was stable in the range where the incident angle tolerance range was greater than 5.5°, while in Comparative Example 3, the received power was not stable in the range where the incident angle tolerance range was 5.5° or less.

[0134] (Example 4) A reflectarray 6 with 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 a composite material of glass / fluororesin with a thickness of 0.764 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 2.6, and tanδ was 0.0025.

[0135] The operating frequency was set to 28 GHz, the target reflection characteristics (the desired reflection characteristics) were set to θix = -70°, θrx = 0°, θiy = θry = 0°, and the size Lx in the x-axis direction of the reflection control region 5 was determined to be 11.394 mm using Equation (3).

[0136] 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 3.798 mm. The shape of the element pattern was a cross patch in which two square patches were orthogonal in the xy plane. Here, in each element pattern within the reflection control region 5, the element length and element width were different, and within the same element pattern, the element lengths and element widths in the x-axis direction and y-axis direction were the same. Specifically, the element lengths were set as lx1 = ly1, lx2 = ly2, lx3 = ly3, and the element widths were set as wx1 = wy1, wx2 = wy2, wx3 = wy3.

[0137] The reflection phase of the unit cell with respect to each of the element width w and element length l was analyzed using finite element method analysis software (HFSS) manufactured by Ansys. It was confirmed that the reflection phase changed as the element width w or element length l changed.

[0138] Next, based on the analysis results of the reflection phase of the unit cell obtained above, the element length l in each unit cell was determined to follow the impedance distribution of Equation (9). The element lengths were respectively lx1 = ly1 = 2.353 mm, lx2 = ly2 = 3.308 mm, lx3 = ly3 = 2.786 mm, and the element widths were respectively wx1 = wy1 = 1.500 mm, wx2 = wy2 = 1.500 mm, wx3 = wy3 = 1.500 mm.

[0139] The reflectarray 6 was arranged with 8 × 6 reflection control regions in the x-axis direction and y-axis direction, and the size in the xy plane was 91.152 mm × 22.788 mm. The reflection characteristics when irradiating the reflectarray 6 with a polarization wave parallel to the y-axis at θix = -70°, θrx = 0° were analyzed using HFSS.

[0140] In order to grasp the incident acceptance angle range, the same analysis was also performed when changing at 2° intervals within the range of -90° ≤ θix ≤ -50°.

[0141] Figure 19 shows the analysis results of the reflectarray 6 obtained in Example 4. However, the horizontal axis of Figure 19 is the reflection angle θrx, and the vertical axis is the RCS. In the reflectarray 6 of Example 4, the electromagnetic wave incident at θix = -70° was reflected in the desired direction of θrx = 0°, and its RCS was -15.56 dBsm.

[0142] (Comparative Example 4) A reflectarray similar to the reflectarray described in Example 4 except for the incident angle θix and the reflection angle θrx was prepared. The incident angle θix and the reflection angle θrx were set to θix = 0° and θrx = -70°, respectively. The reflection characteristics of the reflectarray 6 were analyzed using HFSS.

[0143] In order to grasp the incident angle tolerance range, the same analysis was also performed for the case where the incident angle was changed at 2° intervals in the range of -20° ≤ θix ≤ 20°.

[0144] Figure 20 shows the analysis results of the reflectarray 6 obtained in Comparative Example 4. In the reflectarray 6 of Example 4, the electromagnetic wave incident at θix = 0° was reflected in the desired direction of θrx = -70°, and its RCS was -15.56 dBsm.

[0145] Figure 21 shows the comparison results of the power change amount that can be received at a specific reflection angle θrx when the incident angles of Example 4 and Comparative Example 4 are changed.

[0146] From the results of Figure 21, the incident angle tolerance range was 15.3° for Example 4 and 5.5° for Comparative Example 4. As a result of checking the ease of installation, in Example 4, even when the reflectarray moved 45 cm, the change in received power was within -3 dB in the direction of the received angle that satisfies Equation (1), while in Comparative Example 4, the change was greater than -3 dB. Also, as a result of checking the reception stability, in Example 4, the received power was stable in the range where the incident angle tolerance range was greater than 5.5°, while in Comparative Example 4, the received power was not stable in the range where the incident angle tolerance range was 5.5° or less.

[0147] From the results of Examples 1-4 and Comparative Examples 1-4, it was found that within the range satisfying formula (2), a large incident acceptance angle range is obtained. In the case of the examples, FIG. 22 shows a relationship diagram between the absolute value of the incident angle satisfying formula (1) and the incident acceptance angle range, and in the case of the comparative examples, FIG. 22 shows a relationship diagram between the absolute value of the reflection angle satisfying formula (1) and the incident acceptance angle range. From the results of FIG. 22, in this example, it was found that the incident acceptance angle range increases as |θi| increases.

[0148] Examples 5-7 and Comparative Examples 5-7 are used to confirm the frequency dependence. (Example 5) A reflectarray 6 with 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 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.

[0149] The operating frequency was set to 4.85 GHz, the target reflection characteristics (the desired reflection characteristics) were set to θix = -70°, θrx = 0°, θiy = θry = 0°, and the size Lx in the x-axis direction of the reflection control region 5 was determined to be 65.780 mm using formula (3).

[0150] 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 16.445 mm. The shape of the element pattern was a cross patch in which two square patches were orthogonal in the xy plane. Here, in each element pattern within the reflection control region 5, the element length and the element width were different, and within the same element pattern, the element lengths and element widths in the x-axis and y-axis directions were the same. Specifically, the element lengths were lx1 = ly1, lx2 = ly2, lx3 = ly3, lx4 = ly4, and the element widths were wx1 = wy1, wx2 = wy2, wx3 = wy3, wx4 = wy4.

[0151] The reflection phase of the unit cell with respect to each of the element width w and the element length l was analyzed using finite element method analysis software (HFSS) manufactured by Ansys. It was confirmed that the reflection phase changes as the element width w or the element length l changes.

[0152] Next, based on the analysis results of the reflection phase of the unit cell obtained above, the element length l in each unit cell was determined so as to follow the impedance distribution of Equation (9). The element lengths l were lx1 = ly1 = 14.000 mm, lx2 = ly2 = 14.000 mm, lx3 = ly3 = 14.000 mm, lx4 = ly4 = 14.000 mm, respectively, and the element widths were wx1 = wy1 = 8.303 mm, wx2 = wy2 = 5.887 mm, wx3 = wy3 = 11.538 mm, wx4 = wy4 = 9.400 mm, respectively.

[0153] The reflectarray 6 was arranged with 8 × 6 reflection control regions in the x-axis direction and the y-axis direction, and the size in the xy plane was 206.240 mm × 38.670 mm. The reflection characteristics when irradiating the reflectarray 6 with a polarization parallel to the y-axis at θix = -70° and θrx = 0° were analyzed using HFSS.

[0154] In order to grasp the incident acceptance angle range, the same analysis was also performed when changing at intervals of 2° in the range of -90° ≤ θix ≤ -50°.

[0155] Figure 23 shows the analysis results of the reflectarray 6 obtained in Example 5. However, the horizontal axis in Figure 23 is the reflection angle θrx, and the vertical axis is the RCS. In the reflectarray 6 of Example 5, the electromagnetic wave incident at θix = -70° was reflected in the desired direction of θrx = 0°, and its RCS was 2.13 dBsm.

[0156] (Comparative Example 5) It is the same as the reflectarray described in Example 5 except for the incident angle θix and the reflection angle θrx. A reflectarray was prepared. The incident angle θix and the reflection angle θrx were θix = 0° and θrx = -70°, respectively. The reflection characteristics of the reflectarray 6 were analyzed using HFSS.

[0157] In order to grasp the incident acceptance angle range, the same analysis was also performed for the case where it was changed at 2° intervals in the range of -20° ≤ θix ≤ 20°.

[0158] FIG. 24 shows the analysis result of the reflect array 6 obtained in Comparative Example 5. In the reflect array 6 of Example 5, the electromagnetic wave incident at θix = 0° was reflected in the desired direction of θrx = -70°, and its RCS was 2.07 dBsm.

[0159] FIG. 25 shows the comparison result of the power change amount that can be received at a specific reflection angle θrx when the incident angles of Example 5 and Comparative Example 5 are changed.

[0160] From the results of FIG. 25, the incident acceptance angle range was 15.4° for Example 5 and 5.5° for Comparative Example 5. As a result of confirming the ease of installation, in Example 5, even when the reflect array moved 45 cm, the change in received power was within -3 dB in the direction of the received angle that satisfies Equation (1), while in Comparative Example 5, it changed more than -3 dB. Also, as a result of confirming the reception stability, in Example 5, the received power was stable in the range where the incident acceptance angle range was larger than 5.5°, while in Comparative Example 5, the received power was not stable in the range where the incident acceptance angle range was 5.5° or less.

[0161] (Example 6) A reflect array 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 a fluororesin material 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.

[0162] The operating frequency was set to 60 GHz, the target reflection characteristics (the target reflection characteristics) were set to θix = -45°, θrx = 0°, 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 (3).

[0163] 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 2.355 mm. The shape of the element pattern was a cross-patch in which two rectangular patches were orthogonal in the xy plane. Here, in each element pattern within the reflection control region 5, the element length and element width were different, and within the same element pattern, the element lengths and element widths in the x-axis direction and y-axis direction were the same. Specifically, the element lengths were set as lx1 = ly1, lx2 = ly2, lx3 = ly3, and the element widths were set as wx1 = wy1, wx2 = wy2, wx3 = wy3.

[0164] The reflection phase of the unit cell with respect to each of the element width w and element length l was analyzed using finite element method analysis software (HFSS) manufactured by Ansys. It was confirmed that the reflection phase changed as the element width w or element length l changed.

[0165] Next, based on the analysis results of the reflection phase of the unit cell obtained above, the element length l in each unit cell was determined to follow the impedance distribution of Equation (9). The element lengths were respectively lx1 = ly1 = 1.700 mm, lx2 = ly2 = 1.700 mm, lx3 = ly3 = 1.700 mm, lx4 = ly4 = 14.000 mm, and the element widths were respectively wx1 = wy1 = 1.362 mm, wx2 = wy2 = 1.741 mm, wx3 = wy3 = 1.538 mm.

[0166] The reflectarray 6 was arranged with 8 × 6 reflection control regions in the x-axis direction and y-axis direction, and the size in the xy plane was 62.184 mm × 15.546 mm. The reflection characteristics when irradiating the reflectarray 6 with a polarization wave parallel to the y-axis at θix = -45° and θrx = 0° were analyzed using HFSS.

[0167] In order to grasp the incident acceptance angle range, the same analysis was also performed when changing at 2° intervals in the range of -65° ≤ θix ≤ -25°.

[0168] Figure 26 shows the analysis results of the reflectarray 6 obtained in Example 6. However, the horizontal axis of Figure 26 is the reflection angle θrx, and the vertical axis is the RCS. In the reflectarray 6 of Example 6, the electromagnetic wave incident at θix = -45° was reflected in the desired direction of θrx = 0°, and its RCS was -6.86 dBsm.

[0169] (Comparative Example 6) A reflectarray that is the same as the reflectarray described in Example 6 except for the incident angle θix and the reflection angle θrx was prepared. The incident angle θix and the reflection angle θrx were set to θix = 0° and θrx = -45°, respectively. The reflection characteristics of the reflectarray 6 were analyzed using HFSS.

[0170] In order to grasp the incident allowable angle range, the same analysis was also performed for the case where the angle was changed at 2° intervals in the range of -20° ≤ θix ≤ 20°.

[0171] Figure 27 shows the analysis results of the reflectarray 6 obtained in Comparative Example 6. In the reflectarray 6 of Comparative Example 6, the electromagnetic wave incident at θix = 0° was reflected in the desired direction of θrx = -45°, and its RCS was -6.94 dBsm.

[0172] Figure 28 shows the comparison results of the power change amount that can be received at a specific reflection angle θrx when the incident angles of Example 6 and Comparative Example 6 are changed.

[0173] From the results of Figure 28, the incident allowable angle range was 6.1° for Example 6 and 4.2° for Comparative Example 6. As a result of confirming the ease of installation, in Example 6, even when the reflectarray moved 45 cm, the change in the received power was within -3 dB in the direction of the received angle that satisfies Equation (1), while in Comparative Example 6, the change was greater than -3 dB. Also, as a result of confirming the reception stability, in Example 6, the received power was stable in the range where the incident allowable angle range was greater than 5.5°, while in Comparative Example 6, the received power was not stable in the range where the incident allowable angle range was 5.5° or less.

[0174] (Example 7) A reflectarray 6 with a basic configuration was constructed, where a copper layer with a thickness of 0.018 mm was used for the element pattern 1 and the ground layer 3, and a fluororesin material with a thickness of 0.200 mm was used for the dielectric layer 2. However, the conductivity of the copper was set to 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.

[0175] The operating frequency was set to 60 GHz, the target reflection characteristics (the desired reflection characteristics) were set to θix = -70°, θrx = 0°, θiy = θry = 0°, and the size Lx in the x-axis direction of the reflection control region 5 was determined to be 5.316 mm using Equation (3).

[0176] 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 1.772 mm. The shape of the element pattern was a cross-patch in which two square patches were orthogonal in the xy plane. Here, in each element pattern within the reflection control region 5, the element length and element width were different, and within the same element pattern, the element lengths and element widths in the x-axis and y-axis directions were the same. Specifically, the element lengths were set to lx1 = ly1, lx2 = ly2, lx3 = ly3, and the element widths were set to wx1 = wy1, wx2 = wy2, wx3 = wy3.

[0177] The reflection phase of the unit cell with respect to each of the element width w and element length l was analyzed using finite element method analysis software (HFSS) manufactured by Ansys. It was confirmed that the reflection phase changes as the element width w or element length l changes.

[0178] Next, based on the analysis results of the reflection phase of the unit cell obtained above, the element length l in each unit cell was determined to follow the impedance distribution of Equation (9). The element lengths were lx1 = ly1 = 1.310 mm, lx2 = ly2 = 1.570 mm, lx3 = ly3 = 1.459 mm, and the element widths were wx1 = wy1 = 1.100 mm, wx2 = wy2 = 1.100 mm, wx3 = wy3 = 1.100 mm, respectively.

[0179] The reflectarray 6 has reflection control areas arranged in a matrix of 8 x 6 in the x-axis and y-axis directions, and its size in the xy plane is 42.528 mm x 10.632 mm. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto the reflectarray 6 at θix = -70° and θrx = 0°.

[0180] In order to grasp the allowable incident angle range, a similar analysis was performed when the angle was changed in 2° increments within the range of -90°≦θix≦-50°.

[0181] Fig. 29 shows the analysis results of the reflectarray 6 obtained in Example 7. In Fig. 29, the horizontal axis represents the reflection angle θrx, and the vertical axis represents the RCS. In the reflectarray 6 of Example 7, the electromagnetic wave incident at θrx = -70° was reflected in the desired direction of θrx = 0°, and the RCS was -8.84 dBsm.

[0182] (Comparative Example 7) A reflectarray was prepared that was the same as the reflectarray described in Example 7 except for the incident angle θix and reflection angle θrx. The incident angle θix and reflection angle θrx were set to θix = 0° and θrx = -70°, respectively. The reflection characteristics of the reflectarray 6 were analyzed using HFSS.

[0183] In order to grasp the allowable incident angle range, a similar analysis was performed when the angle was changed in 2° increments within the range of -20°≦θix≦20°.

[0184] 30 shows the analysis results of the reflectarray 6 obtained in Comparative Example 7. In the reflectarray 6 of Comparative Example 7, the electromagnetic wave incident at θix=0° was reflected in the desired direction of θrx=-70°, and the RCS was -8.89 dBsm.

[0185] FIG. 31 shows the results of comparison of the amount of change in power that can be received at a specific reflection angle θrx when the incident angle is changed in each of Example 7 and Comparative Example 7.

[0186] From the results of FIG. 31, the incident acceptance angle ranges were 15.1° for Example 7 and 5.4° for Comparative Example 7. As a result of checking the ease of installation, in Example 7, even when the reflect array moved 45 cm, the change in received power was within -3 dB in the direction of the received angle that satisfies Equation (1), whereas in Comparative Example 7, the change was greater than -3 dB. Further, as a result of checking the reception stability, in Example 7, the received power was stable in a range where the incident acceptance angle range was greater than 5.5°, whereas in Comparative Example 7, the received power was not stable in a range where the incident acceptance angle range was 5.5° or less.

[0187] From the comparison between Example 1 (Comparative Example 1) and Example 6 (Comparative Example 6), and Example 4 (Comparative Example 4) and Example 5 (Comparative Example 5), and Example 7 (Comparative Example 7), it was found that there is no significant difference in the incident acceptance angle range depending on the frequency.

[0188] Using Example 8 and Comparative Example 8, the influence of the reflection angle is confirmed. (Example 8) A reflect array 6 with a basic configuration was constructed 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 the copper was 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.

[0189] The operating frequency was set to 28 GHz, the target reflection characteristics (the intended reflection characteristics) were set to θix = 70°, θrx = -30°, θiy = θry = 0°, and the size Lx in the x-axis direction of the reflection control region 5 was determined to be 24.348 mm using Equation (3).

[0190] The number of divisions of the reflection control region 5 was set to 6, and the sizes of the unit cell in the x-axis direction and the y-axis direction were set to 4.058 mm. The shape of the element pattern was a cross-patch in which two rectangular patches were orthogonal in the xy plane. Here, in each element pattern within the reflection control region 5, the element length and the element width were different, and within the same element pattern, the element lengths and the element widths in the x-axis direction and the y-axis direction were the same. Specifically, the element lengths were lx1 = ly1, lx2 = ly2, lx3 = ly3, lx4 = ly4, lx5 = ly5, lx6 = ly6, and the element widths were wx1 = wy1, wx2 = wy2, wx3 = wy3, wx4 = wy4, wx5 = wy5, wx6 = wy6.

[0191] The reflection phases of the unit cell with respect to the element width w and the element length l were analyzed using finite element method analysis software (HFSS) manufactured by Ansys. It was confirmed that the reflection phase changed as the element width w or the element length l changed.

[0192] Next, based on the analysis results of the reflection phases of the unit cell obtained above, the element length l in each unit cell was determined to follow the impedance distribution of Equation (9). The element lengths were lx1 = ly1 = 2.897 mm, lx2 = ly2 = 3.079 mm, lx3 = ly3 = 3.621 mm, lx4 = ly4 = 1.885 mm, lx5 = ly5 = 2.530 mm, lx6 = ly6 = 2.743 mm, and the element widths were wx1 = wy1 = 1.500 mm, wx2 = wy2 = 1.500 mm, wx3 = wy3 = 1.500 mm, wx1 = wy1 = 1.500 mm, wx2 = wy2 = 1.500 mm, wx3 = wy3 = 1.500 mm, respectively.

[0193] The reflectarray 6 was arranged with 8 × 6 reflection control regions in the x-axis direction and the y-axis direction, and the size in the xy plane was 194.784 mm × 146.008 mm. The reflection characteristics when the reflectarray 6 was irradiated with a polarization wave parallel to the y-axis at θix = 70° and θrx = -30° were analyzed using HFSS.

[0194] In order to grasp the incident acceptance angle range, the same analysis was also performed when changing at 2° intervals in the range of 50° ≤ θix ≤ 90°.

[0195] Fig. 32 shows the analysis result of the reflectarray 6 obtained in Example 8. However, the horizontal axis in Fig. 32 is the reflection angle θrx, and the vertical axis is the RCS. In the reflectarray 6 of Example 8, the electromagnetic wave incident at θix = 70° was reflected in the desired direction of θrx = -30°, and its RCS was -1.19 dBsm.

[0196] (Comparative Example 8) A reflectarray similar to the reflectarray described in Example 8 except for the incident angle θix and the reflection angle θrx was prepared. The incident angle θix and the reflection angle θrx were set to θix = -30° and θrx = 70°, respectively. The reflection characteristics of the reflectarray 6 were analyzed using HFSS.

[0197] In order to grasp the incident acceptance angle range, the same analysis was also performed when changing at 2° intervals in the range of -20° ≤ θix ≤ 20°.

[0198] Fig. 33 shows the analysis result of the reflectarray 6 obtained in Comparative Example 8. In the reflectarray 6 of Comparative Example 8, the electromagnetic wave incident at θix = -30° was reflected in the desired direction of θrx = 70°, and its RCS was -1.86 dBsm.

[0199] Fig. 34 shows the comparison result of the power change amount that can be received at a specific reflection angle θrx when changing the incident angles of Example 8 and Comparative Example 8, respectively.

[0200] 34, the acceptable incident angle range was 8.3° for Example 8 and 2.5° for Comparative Example 8. As a result of checking the ease of installation, in Example 8, even when the reflectarray was moved 45 cm, the change in received power was within -3 dB in the direction of the receiving angle that satisfied formula (1), whereas in Comparative Example 8, the change was greater than -3 dB. Furthermore, as a result of checking the reception stability, in Example 8, the received power was stable in a range where the acceptable incident angle range was greater than 5.5°, whereas in Comparative Example 8, the received power was unstable in a range where the acceptable incident angle range was 5.5° or less.

[0201] [Other embodiments] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and examples, and various modifications are possible within the scope of the gist of the present invention. The following describes possible aspects of the present invention, but the present invention is not limited to these. (Aspect 1) A reflectarray that reflects electromagnetic waves, the reflectarray having a reflection control area that controls a phase, the reflection control area satisfying the following formula (1) when a length of a long side is L, a wavelength of the electromagnetic wave to be reflected is λ, an incident angle is θi, and a reflection angle is θr: the incident angle |θi| is in the range of 45° or more and 70° or less, the incident angle θi and the reflection angle θr satisfy the relationship of the following formula (2), and an acceptable incident angle range Δθi is in the range of more than 5.5° and 16° or less.

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Explanation of Signs

[0202] 1, 11-1 n , 1d1-1d3, 1e1-1e3, 1a-1c, 1 x 1-1 x n , 1 y 1-1 y n element pattern, 2 dielectric layer, 3 ground layer, 4, 41-4 n, 4a - 4c, 4 x 1 - 4 x n , 4 y 1 - 4 y n unit cell, 5 reflection control regions, 6, 61 - 62 reflect arrays, 200, 201 walls, 300 transmitter, 400 receiver, 500 shield, 501 building (shield), 600 support 601 support position adjustment jig

Claims

1. A reflectarray device having a reflectarray for reflecting electromagnetic waves installed on a support, wherein the reflectarray is fixed to the support by an installation layer, the reflectarray has a reflection control region for controlling the phase, when the length of the long side of the reflection control region is L, the wavelength of the electromagnetic wave to be reflected is λ, the incident angle is θi, and the reflection angle is θr, the following formula (1) is satisfied, the incident angle |θi| is in the range of 45° or more and 70° or less, and the incident angle θi and the reflection angle θr satisfy the relationship of the following formula (2), and the incident acceptance angle range Δθi is larger than 5.5° and 16° or less. A reflectarray device. 【Number 1】 【Number 2】

2. The reflectarray device according to claim 1, wherein the support is a signboard, a wall, a ceiling, or window glass.

3. The reflectarray device according to claim 1, wherein the position or angle of the reflectarray can be adjusted vertically, horizontally, and laterally by an adjustment mechanism attached to the support.

4. The reflectarray device according to claim 1, wherein a design layer is provided on the surface of the reflectarray.

5. The reflectarray device according to claim 1, wherein the reflectarray has transparency and the element or the ground layer is a mesh.

6. The reflectarray device according to any one of claims 1 to 5, wherein the reflectarray reflects electromagnetic waves of 3 GHz to 60 GHz.

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