Reflect array, electromagnetic wave reflection system, and installation method for reflect array

Abstract

To provide a reflect array that can reflect 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 8

Description

[Technical field]

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

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

[0003] Among these technologies, metamaterial or metasurface reflectors that can freely control the reflection angle of electromagnetic waves are being actively developed. There are two types of metamaterial reflectors: active reflectors that use electrical control to control the direction of incident and reflected electromagnetic waves (e.g., Patent Document 1), and passive reflectors that do not have an electrical control mechanism, and in which the directions of incident and reflected electromagnetic waves are determined at the design stage, and the dimensions of the element and the material properties are designed based on that (e.g., Patent Document 2).

[0004] In Patent Document 1, the device 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 of the variable capacitor. The operation of the variable capacitor is controlled by a phase control signal (bias voltage). This makes it possible to reflect / scatter electromagnetic waves emitted from an electromagnetic wave source in any direction.

[0005] Patent Document 2 also introduces a metasurface reflector that is provided with a metal ground layer on the bottom surface of a dielectric substrate that does not transmit polarized waves in any direction, and multiple supercells that have two or more types of cross-shaped metal resonators with different arm lengths. This metasurface reflector can control the phase by the structure of the metal resonators. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6438857 [Patent Document 2] Patent Publication No. 2021-48465 Summary of the Invention [Problem to be solved by the invention]

[0007] Since the angle between the incident electromagnetic wave and the reflected electromagnetic wave can be controlled by changing the voltage, etc., the angle can be adjusted appropriately by changing the angle between the transmitter and receiver, giving a high degree of freedom in practical use. However, a problem arises in that a phase control signal is required to control the phase, making it expensive. In addition, passive reflectors can be manufactured inexpensively because they do not have an electrical control mechanism, but they have a problem in that the angles between the incident electromagnetic wave and the reflected electromagnetic wave are fixed, so there is little flexibility in practical use. Therefore, the present invention aims to provide a reflectarray, an electromagnetic wave reflection system, and a method for installing a reflectarray, which is a passive reflector that can be manufactured inexpensively and can reflect electromagnetic waves incident from a wide range of angles to a specified angle. [Means for solving the problem]

[0008] In order to solve the above problems, a representative reflectarray of the present invention is a reflectarray that reflects electromagnetic waves, the reflectarray having a reflection control area that controls the phase, the reflection control area satisfying equation (1) (described below) when the length of the long side is L, the wavelength of the reflected electromagnetic wave is λ, the incident angle is θi, and the 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 equation (2) (described below), and the allowable incident angle range Δθi is in the range of more than 5.5° and less than 16°. Effect 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 at a predetermined angle. Problems, configurations and effects other than those described above will become apparent from the following description of the preferred embodiment of the invention. [Brief description of the drawings]

[0010] [Figure 1a] FIG. 1a is a diagram showing the overall configuration of a reflect array. [Figure 1b] FIG. 1b is an enlarged view of the reflection control area. [Diagram 2] FIG. 2 is a diagram showing the angles of incidence and reflection when a reflect array is placed on the xy plane. [Diagram 3] FIG. 3 is a diagram showing an example of a layer configuration of the reflect array 6. As shown in FIG. [Figure 4] FIG. 4 is a diagram showing an example of an arrangement of unit cells according to a direction in which asymmetric reflection is to be generated. [Diagram 5] FIG. 5 is a diagram showing an example of an arrangement of unit cells according to a direction in which asymmetric reflection is to be generated. [Figure 6] FIG. 6 is a diagram showing the configuration of an element pattern. [Figure 7] FIG. 7 is a diagram showing an example of the shape of an element pattern after etching. [Figure 8] FIG. 8 is a diagram showing an example of an electromagnetic wave reflection system using a reflect array. [Figure 9] FIG. 9 is a diagram showing an example of a reflect array installed on a support. [Figure 10] FIG. 10 is a diagram showing the analysis result of the reflectarray obtained in Example 1, and is a diagram showing the reflection pattern of the reflectarray when θix=−45° and θrx=0°. [Figure 11] FIG. 11 is a diagram showing the analysis result of the reflectarray obtained in Comparative Example 1, and is a diagram showing the reflection pattern of the reflectarray when θix=0° and θrx=−45°. [Figure 12] FIG. 12 is a diagram showing a comparison result 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 1 and Comparative Example 1. [Figure 13] FIG. 13 is a diagram showing the analysis result of the reflectarray obtained in Example 2, and is a diagram showing the reflection pattern of the reflectarray when θix=−50° and θrx=0°. [Figure 14] FIG. 14 is a diagram showing the analysis results of the reflectarray obtained in Comparative Example 2, and is a diagram showing the reflection patterns of the reflectarray when θix=0° and θix=−50°. [Figure 15] FIG. 15 is a diagram showing a comparison result 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 2 and Comparative Example 2. [Figure 16] FIG. 16 is a diagram showing the analysis result of the reflectarray obtained in Example 3, and is a diagram showing the reflection pattern of the reflectarray when θix=−60° and θrx=0°. [Figure 17] FIG. 17 is a diagram showing the analysis results of the reflectarray obtained in Comparative Example 3, and is a diagram showing the reflection pattern of the reflectarray when θix=0° and θrx=−60°. [Figure 18] FIG. 18 is a diagram showing a comparison result 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 3 and Comparative Example 3. [Figure 19] FIG. 19 is a diagram showing the analysis results of the reflectarray obtained in Example 4, and is a diagram showing the reflection pattern of the reflectarray when θix=−70° and θrx=0°. [Figure 20] FIG. 20 is a diagram showing the analysis results of the reflectarray obtained in Comparative Example 4, and is a diagram showing the reflection pattern of the reflectarray when θix=0° and θrx=−70°. [Figure 21] FIG. 21 is a diagram showing a comparison result 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 4 and Comparative Example 4. [Figure 22] FIG. 22 is a diagram showing the relationship between the incident angle and the incident angle range in Example 1-4 and the relationship between the incident angle and the incident angle range in Comparative Example 1-4. [Figure 23] FIG. 23 is a diagram showing the analysis result of the reflectarray obtained in Example 5, and is a diagram showing the reflection pattern of the reflectarray when θix=−70° and θrx=0°. [Figure 24] FIG. 24 is a diagram showing the analysis results of the reflectarray obtained in Comparative Example 5, and is a diagram showing the reflection pattern of the reflectarray when θix=0° and θrx=−70°. [Diagram 25] FIG. 25 is a diagram showing a comparison result 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 5 and Comparative Example 5. [Figure 26] FIG. 26 is a diagram showing the analysis results of the reflectarray obtained in Example 6, and is a diagram showing the reflection pattern of the reflectarray when θix=−45° and θrx=0°. [Figure 27] FIG. 27 is a diagram showing the analysis results of the reflectarray obtained in Comparative Example 6, and is a diagram showing the reflection pattern of the reflectarray when θix=0° and θrx=−45°. [Figure 28] FIG. 28 is a diagram showing a comparison result 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 6 and Comparative Example 6. [Figure 29]FIG. 29 is a diagram showing the analysis results of the reflectarray obtained in Example 7, and is a diagram showing the reflection pattern of the reflectarray when θix=−70° and θrx=0°. [Diagram 30] FIG. 30 is a diagram showing the analysis results of the reflectarray obtained in Comparative Example 7, illustrating the reflection pattern of the reflectarray when θix=0° and θrx=−70°. [Diagram 31] FIG. 31 is a diagram showing a comparison result 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. [Diagram 32] FIG. 32 is a diagram showing the analysis results of the reflectarray obtained in Example 8, and is a diagram showing the reflection pattern of the reflectarray when θix=70° and θrx=−30°. [Diagram 33] FIG. 33 is a diagram showing the analysis results of the reflectarray obtained in Comparative Example 8, and is a diagram showing the reflection pattern of the reflectarray when θix=−30° and θrx=70°. [Diagram 34] FIG. 34 is a diagram showing a comparison result 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 8 and Comparative Example 8. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiment. In addition, in the description of the drawings, the same parts are denoted by the same reference numerals. When there are multiple components having the same or similar functions, they may be described by using the same reference numerals with different subscripts, or when there is no need to distinguish between these multiple components, the subscripts may be omitted. In order to facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc. Therefore, the present disclosure is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

[0012] (Terminology explanation) Fig. 1 is a diagram showing the configuration of a reflectarray. Fig. 1a is a diagram showing the configuration of the entire reflectarray, and Fig. 1b is a diagram showing an enlarged reflection control area. Terms related to the configuration of the reflectarray of the present disclosure will be described with reference to the drawings. In this disclosure, a "reflectarray (electromagnetic wave reflector)" is a component that reflects electromagnetic waves and has one or more reflection control regions that control the phase, and is a reflector that does not perform phase control by external power. It includes reflectors that perform asymmetric reflection with different angles of incidence and reflection, reflectors that scatter electromagnetic waves in multiple directions, and reflectors that collect electromagnetic waves at a specific location. In the following description, an xyz coordinate system is applied, and the reflectarray is placed on the xy plane. Phase control using external power refers to an active reflector that has an external power source and can control the phase by controlling the voltage, etc.

[0013] Furthermore, the term "reflection control area" refers to a part of the area that constitutes the reflectarray. The reflection control area is the smallest area that can reflect electromagnetic waves incident on that area in a specified direction. The reflectarray is composed of one or more reflection control areas. The reflection control area includes not only a two-dimensional area in which the electromagnetic waves are parallel to the incident area, but also a layer structure formed in a direction perpendicular to the area. Within one reflection control area, the size of a side (long side) of a reflection control area in which multiple unit cells are arranged is defined as L, and the size of a side (short side) of a reflection control area in which only one unit cell is arranged is defined as M.

[0014] Moreover, the term "unit cell" refers to an area obtained by dividing the reflection control area. The unit cell includes one element pattern (element). Two or more unit cells exist in one reflection control area.

[0015] The element length in the x-axis direction is denoted as lx, and the element length in the y-axis direction is denoted as ly. The element width in the x-axis direction is denoted as wx, and the element width in the y-axis direction is denoted as wy.

[0016] 2 is a diagram showing the incident angle and the reflection angle when the reflect array is arranged on the xy plane. The terms related to the definition of angles in this disclosure will be explained with reference to FIG. The angle θx in the x-axis direction is expressed as a positive angle (0° to 180°) when it spreads from the +z-axis direction toward the +x-axis direction, and as a negative angle (0° to -180°) when it spreads from the +z-axis direction toward the -x-axis direction. Similarly, the angle θy in the y-axis direction is expressed as a positive angle (0° to 180°) when it spreads from the +z-axis direction toward the +y-axis direction, and as a negative angle (0° to -180°) when it spreads from the +z-axis direction toward the -y-axis direction.

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

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[0018] In this disclosure, an "electromagnetic wave reflection system" is composed of three components: a transmitter, a reflect array, and a receiver. A "transmitter" refers to something that emits electromagnetic waves or something that reflects electromagnetic waves from an electromagnetic wave emitter. Specifically, there are wireless base stations, mobile stations, repeaters, mobile bodies, communication terminals, reflectors, etc. Moreover, a "receiver" is something that receives electromagnetic waves, and specific examples thereof include a wireless base station, a mobile station, a repeater, a mobile body, a communication terminal, and a reflector. In this disclosure, "primary radiation" refers to electromagnetic waves emitted from a transmitter in an electromagnetic wave reflecting system, and "secondary radiation" refers to electromagnetic waves emitted from a reflectarray in an electromagnetic wave reflecting system, which are generated when the electromagnetic waves primarily emitted from the transmitter are incident on the reflectarray.

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

[0020] The reflectarray 6 of FIG. 1b produces 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 the unit cell is not specified, it will also be referred to as "unit cell 4". n is a positive integer of 2 or more.) The unit cell 4 is a part obtained by dividing the reflection control area 5 at equal intervals along the x-axis direction. n is the number of divisions when dividing the reflection control area into unit cells in the x-axis direction. The unit cell 4 is a square, and if the size (length) of the unit cell 4 is s, the size (long side) of the reflection control area 5 in the x-axis direction is Lx, and the size (short side) of the reflection control area 5 in the y-axis direction is My, then s = Lx / n = My. The size of the reflect array 6 is determined by the size and number of the reflection control regions 5. For example, in a reflect array that performs asymmetric reflection in the x-axis direction, in the case where eight reflection control regions 5 are arranged in the x-axis direction and six in the y-axis direction, the size of the reflect array 6 in the x-axis direction is 8Lx and the size in the y-axis direction is 6My. The reflection pattern of the reflect array 6 changes depending on the number of reflection control regions arranged in the direction of asymmetric reflection. That is, in FIG. 1b, the reflection pattern changes depending on 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 reflection control regions arranged in the x-axis direction, the thinner the reflection pattern of the reflect array becomes. The number of reflection control regions arranged in the y-axis direction affects the reflection intensity, and the more reflection control regions arranged in the y-axis direction, the greater the reflection intensity becomes. 1, the reflection control region 5 is configured by n unit cells 4 aligned in the x-axis direction, and the reflect array 6 includes a plurality of reflection control regions 5, but the present disclosure is not limited to such a configuration. The reflection control region may be configured by unit cells aligned on the y-axis, or may include unit cells aligned on the x-axis and y-axis. The configuration of the reflection control region will be described later.

[0021] (Element pattern configuration) An element pattern is formed on the surface of the unit cell 4 facing the +z-axis direction. Using the division number n, unit cell 41, unit cell 42, ... unit cell 4 n The element pattern 11 is formed in the unit cell 41. The element pattern 12 is formed in the unit cell 42. The element pattern 13 is formed in the unit cell 43. n Element pattern 1 n is formed.

[0022] Within the reflection control area of ​​FIG. 1, each element pattern has a shape that is slightly different from the other element patterns. n The shape of the element pattern shown in is sometimes called a cross patch. A cross patch refers to a shape in which two square patches are perpendicular to each other on the xy plane. Element pattern 11 has a shape in which a square patch having an element length lx1, which is the size in the x-axis direction, and an element width wy1, which is the size in the y-axis direction, and a square patch having an element length ly1, which is the size in the y-axis direction, and an element width wx1, which is the size in the x-axis direction, are perpendicular to each other with a common center of gravity. Similarly, element pattern 1 n has a shape in which a square patch having an element length lxn and an element width wyn and a square patch having an element length lyn and an element width wxn are orthogonal to each other with a common center of gravity.

[0023] (Explanation of each configuration, design method) (Layer composition) The layer structure of the reflectarray 6 will be described with reference to FIG. 3. The reflectarray 6 has a structure in which at least the element pattern 1, the dielectric layer 2, and the ground layer 3 are stacked in a direction from the +z-axis direction to the -z-axis direction. In the following description, a structure consisting of three layers, the element pattern 1, the dielectric layer 2, and the ground layer 3, is referred to as a "basic structure". In practice, it is preferable that the reflectarray 6 has one or more layers having various functionalities (hereinafter also referred to as "functional layers") stacked on the element pattern 1 side or the ground layer 3 side of the basic structure, or on both sides. In the following description, layers included in the reflectarray other than the element pattern 1, the dielectric layer 2, and the ground layer 3 may be referred to as "functional layers" when the type of layer is not specified.

[0024] If necessary, a layer for improving the adhesion between the element pattern 1 and the dielectric layer 2, or between the ground layer 3 and the dielectric layer 2, may be formed. A layer used for a purpose other than the purpose for improving the adhesion may also be formed. Note that intermediate products generated in the manufacturing process of the reflect array 6 may be formed in layers and remain on the reflect array 6.

[0025] Examples of functional layers include a design layer that is designed to take into consideration the scenery of the area where the reflect array 6 is installed, an installation layer that enables the reflect array 6 to be easily installed on a support such as a wall or ceiling, a protective layer that protects the basic structure, and an adhesive layer for laminating each layer.

[0026] (Reflection control area) The reflect array 6 includes at least one reflection control area. The properties of the reflect array can be changed depending on how the reflection control areas are arranged. For example, when an electromagnetic wave of a certain wavelength is incident at a certain incident angle, it is possible to give the reflect array a characteristic of reflecting in a single direction by periodically arranging reflection control areas with a common reflection direction. In addition, when an electromagnetic wave of a certain wavelength is incident at a certain incident angle, it is possible to give the reflect array a characteristic of scattering the electromagnetic wave in multiple directions by configuring a reflect array including reflection control areas with different reflection directions. In addition, it is possible to give the reflect array a characteristic of concentrating the electromagnetic wave at a specific location by shifting the reflection direction by a predetermined angle for each reflection control area. The frequency that is expected to be applied to the reflect array at the time of design is hereinafter referred to as the "operating frequency".

[0027] The size Lx of the reflection control area in the x-axis direction is determined by, for example, equation (3), where λ is the wavelength of the operating frequency, θix is ​​the x-axis component of the incident angle of the electromagnetic wave incident on the reflection control area, and θrx is the x-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control area. When θix ≠ -θrx, .

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[0028] In addition, the size Ly of the reflection control area in the y-axis direction is determined, for example, by equation (4), where θiy is the y-axis component of the incident angle of the electromagnetic wave incident on the reflection control area, and θry is the y-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control area. When θiy ≠ -θry,

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[0029] In particular, when there is no distinction between the x-axis and y-axis components of equations (3) and (4), they are expressed as in equation (1) above.

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[0030] (Relationship between unit cell and reflection phase) The relationship between the unit cell and the reflection phase will be described with reference to FIG. 4 and FIG. 5. FIG. 4 and FIG. 5 are diagrams showing an example of the arrangement of the unit cells according to the direction in which asymmetric reflection is generated. The reflection control region 5 has at least two unit cells. Here, FIG. 4(a) shows the direction of the electromagnetic wave (incident wave) incident on the reflect array 6f and the direction of the electromagnetic wave (reflected wave) reflected from the reflect array 6f. In other words, the arrow drawn with a thick solid line shows the traveling direction of the wave front, the arrow toward the reflect array 6 shows the traveling direction of the wave front of the incident wave, and the arrow away from the reflect array 6f shows the traveling direction of the wave front of the reflected wave. Also, FIG. 4(b) shows a plan view of the reflect array 6f seen from the z-axis direction. The relationship between (a) and (b) in FIG. 5 is similar to that between (a) and (b) in FIG. 4.

[0031] The unit cells have the effect of reflecting incident electromagnetic waves with a predetermined phase difference. Since each unit cell in the reflection control region exhibits a different reflection phase, the reflected wavefront, which is the wavefront of the reflected wave generated from the reflection control region, is tilted from the reflection angle when the incident angle and the reflection angle are equal, resulting in asymmetric reflection, which is different from symmetric reflection when the incident angle and the reflection angle are equal.

[0032] In the case where the reflect array 6f is to perform asymmetric reflection only along the x-axis direction (θix ≠ -θrx as shown in FIG. 4(a)), unit cells exhibiting different reflection phases are arranged along the x-axis direction in the reflection control region 5a (FIG. 4(b)). The reflection control region 5a has a division number n=3 and has three unit cells arranged in the x-axis direction. The size (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 a symmetric reflection, the size My of the short side of the reflection control region can take any value. However, for ease of design, a square unit cell whose size is determined by Lx and the division number m is used for convenience, and My is set equal to Lx / 3.

[0033] Similarly, when it is desired to make the reflect array 6g perform asymmetric reflection only along the y-axis direction (θiy ≠ -θry as shown in FIG. 5(a)), unit cells exhibiting different reflection phases are arranged along the y-axis direction in the reflection control region 5b (FIG. 5(b)). Here, m (m is a positive integer of 2 or more) is the number of divisions when dividing the reflection control region into unit cells in the y-axis direction. The reflection control region 5b has three unit cells arranged in the y-axis direction, with the number of divisions m=3. The size Ly of the reflection control region 5b in the y-axis direction is determined by equation (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 a symmetric reflection, the size Mx of the short side of the reflection control region can take any value. However, for ease of design, a square unit cell whose size is determined by Ly and the number of divisions m is used for convenience, and Mx is set equal to Ly / 3.

[0034] (Distribution of reflection phase within reflection control area, distribution of surface impedance) The distribution of the reflection phase in the reflection control area is determined to follow, for example, formula (5). Here, the wavelength of the operating frequency is λ(m), the x-axis component of the incident angle of the electromagnetic wave incident on the reflection control area is θix, the y-axis component is θiy, the x-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control area is θrx, the y-axis component is θry, the reflection phases at arbitrary coordinates x1 and x2 parallel to the x-axis in the reflection control area are φx1 and φx2, respectively, the distance between coordinates x1 and x2 is dx, and the reflection phase difference between Φx1 and Φx2 is ΔΦx. In addition, the reflection phases at arbitrary coordinates y1 and y2 parallel to the y-axis are φy1 and φy2, respectively. When the reflection control area is to perform asymmetric reflection along the x-axis direction, it is preferable that formula (5) is satisfied, and when the reflection control area is to perform asymmetric reflection along the y-axis direction, it is preferable that formula (6) is satisfied.

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[0035] Also, instead of the reflection phase, the distribution of surface impedance can be applied within the reflection control area. In that case, the distribution of surface impedance is expressed by, for example, equation (7) and equation (8). Here, Zsx is the surface impedance distribution parallel to the x-axis direction of the reflection control area, Zsy is the surface impedance distribution parallel to the y-axis direction of the reflection control area, and η1 is the impedance of the incident wave. Also, the x-axis component of the incidence angle of the electromagnetic wave incident on the reflection control area is θix, the y-axis component is θiy, the x-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control area is θrx, and the y-axis component is θry. Note that x1 and x2 indicate x coordinates as relative coordinates within the reflex control area, and can take the reference x = 0 at any coordinate in the reflex control area. Similarly, y1 and y2 indicate y coordinates as relative coordinates within the reflex control area, and can take the reference y = 0 at any coordinate in the reflex control area. Furthermore, k1 is the wave number of the reflected wave, and j represents an imaginary unit. When it is intended to cause the reflection control area to perform asymmetric reflection along the x-axis direction, it is preferable that formula (7) be satisfied, and when it is intended to cause the reflection control area to perform asymmetric reflection along the y-axis direction, it is preferable that formula (8) be satisfied.

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[0036] Other surface impedance distributions are expressed, for example, by formula (9) and formula (10). When the reflection control area is intended to perform asymmetric reflection only along the x-axis direction, it is preferable that formula (9) be satisfied, and when the reflection control area is intended to perform asymmetric reflection only along the y-axis direction, it is preferable that formula (10) be satisfied.

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[0037] The above formulas (5) to (10) are examples of design formulas used when designing the distribution of the reflection phase and the distribution of the surface impedance. The present disclosure is not limited to the use of formulas (5) to (10), and other design formulas can be appropriately selected.

[0038] (Reflectarray design method) A method for designing a reflectarray will be described. As an example, a method for designing a reflectarray in which multiple identical reflection control areas are arranged in the x-axis direction will be described. A reflectarray in which multiple identical reflection control areas are arranged in the y-axis direction and a reflectarray that is intended to perform asymmetric reflection in both the x-axis and y-axis directions can also be designed in a similar manner.

[0039] (Design method 1) Design method 1 is a design method in which the element length and the gap between the element patterns are fixed, and the element width is changed to control the phase of the element pattern. This method has the advantage that the change in phase associated with the change in element width is more gradual than in design methods 2 and 3 described below, making it easier to ensure product performance even if the element shape changes during the manufacturing process. (Step 1) First, the target reflection characteristics (operating frequency, incident angle, and reflection angle) are set. (Step 2) Next, the size Lx of the reflection control area is determined using equation (3). (Step 3) Next, the size Lx of the reflection control area is divided into n parts to determine the size of the unit cell. (Step 4) Next, the element length lx of the element pattern is determined within the range that fits in the unit cell. Since the element patterns are arranged evenly within the unit cell, the gap gx between the element patterns is also determined as a result. (Step 5) Next, the reflection phase of the unit cell is analyzed using the element width wx as a design parameter. The reflection phase is derived using the element width wx of the element pattern as a design parameter, and an analysis result showing the relationship between the element width and the reflection phase in the unit cell is obtained. (Step 6) Next, the ideal reflection phase or impedance for realizing the reflection characteristics of the targeted reflection control region is calculated using equations (5) to (10), and the element width wx for realizing the desired reflection phase or impedance is selected based on the above analysis results. (Step 7) Next, a reflectarray is formed so as to include at least one reflection control region. The reflection characteristics of the reflectarray are analyzed. (Step 8) Based on the analysis results of Step 7, it is also possible to further fine-tune the element width wx using an optimization method so as to further increase the RCS at the target reflection angle and reduce the RCS at angles other than the target angle.

[0040] (Design method 2) In design method 2, the element width is fixed and the element length is changed to control the phase of the element pattern. (Step 1) First, the target reflection characteristics (operating frequency, incident angle, and reflection angle) are set. (Step 2) Next, the size Lx of the reflection control area is determined using equation (3). (Step 3) Next, the size Lx of the reflection control area is divided into n parts to determine the size of the unit cell. (Step 4) Next, the element width wx of the element pattern is determined within the range that fits in the unit cell. (Step 5) Next, the reflection phase of the unit cell is analyzed using the element length lx as a design parameter. The reflection phase is derived using 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) Next, the ideal reflection phase or impedance for realizing the reflection characteristics of the targeted reflection control region is calculated using equations (5) to (10), and the element length lx for realizing the desired reflection phase or impedance is selected based on the above analysis results. (Step 7) Next, a reflectarray is formed so as to include at least one reflection control region. The reflection characteristics of the reflectarray are analyzed. (Step 8) Based on the analysis results of Step 7, it is also possible to further fine-tune the element length lx using an optimization method so as to further increase the RCS at the target reflection angle and to reduce the RCS at angles other than the target angle.

[0041] (Design method 3) Design method 3 is a design method in which the phase of the element pattern is controlled by changing both the element width and element length. This design method is effective when design methods 1 and 2 do not provide a sufficient reflection phase change width. (Step 1) First, the target reflection characteristics (operating frequency, incident angle, and reflection angle) are set. (Step 2) Next, the size Lx of the reflection control area is determined using equation (3). (Step 3) Next, the size Lx of the reflection control area is divided into n parts to determine the size of the unit cell. (Step 4) Next, the reflection phase of the unit cell is analyzed using the element width wx and element length lx as design parameters. The reflection phase is derived using the element width wx and element length lx of the element pattern as design parameters, and an analysis result is obtained that shows the relationship between the element width wx, element length lx, and reflection phase in the unit cell. (Step 5) Next, the ideal reflection phase or impedance for realizing the reflection characteristics of the targeted reflection control region is calculated using equations (5) to (10), and the element width wx and element length lx for realizing the desired reflection phase or impedance are selected based on the above analysis results. (Step 6) Next, a reflectarray is formed so as to include at least one reflection control region. The reflection characteristics of the reflectarray are analyzed. (Step 7) Based on the analysis results of step 7, it is also possible to further fine-tune the element width wx and element length lx using an optimization method so as to further increase the RCS at the target reflection angle and to reduce the RCS at angles other than the target angle.

[0042] (element pattern) The element pattern will be described in detail with reference to Figures 1, 6, and 7. Here, a detailed description will be given of the cross patch shape, but the element pattern shape is not limited to this. For example, it may be a circular shape, a rectangular shape, or a square shape. Generally, reflectarrays change their reflection characteristics by utilizing the resonance of the element pattern. Here, linear or rectangular element patterns (square patches) mainly resonate with polarized waves in the direction along their long axis, so it is known that when an element pattern with a shape that is perpendicular to these is used, it can accommodate both TE and TM polarized waves.

[0043] In the reflectarray of the present disclosure, the size of each unit cell and the size of the element pattern become smaller as the division numbers n and m of the reflection control area are increased. Since resonance occurs only when a certain element pattern size is satisfied for the frequency, if n and m are increased beyond a certain value, it becomes difficult to achieve asymmetric reflection at the operating frequency. On the other hand, the more n and m are increased, the more the reflection characteristics can be controlled for each smaller area, so the reflection characteristics of the reflectarray approach the theoretical characteristics.

[0044] The element pattern in the reflectarray of the present disclosure includes a cross patch in the shape of two square patches perpendicular to each other in the xy plane. Here, as shown in FIG. 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, the element pattern in the unit cell 4n can be expressed as having element lengths lxn and lyn and element widths wxn and wyn.

[0045] Fig. 6 is a diagram showing the configuration of an element pattern. One element pattern is arranged in a unit cell. The cross patch constituting the element pattern of a unit cell 4 may be such that the intersection point between two rectangular patches is 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) and unit cell 4c in Fig. 6(c)). These cross patch variations can be appropriately selected, which can increase the flexibility and scalability of the design.

[0046] In this disclosure, the element widths wx and wy are treated as design parameters, and each element pattern included in the reflection control region is designed to have a different element width. The element width wx can be changed within a range up to a value equal to the element length lx, and the element width wy can be changed within a range up to a value equal to the element length ly. The element width wx and the element width wy in the same element pattern may be equal or different. When the values ​​are different, the characteristics for the TE and TM polarizations can be controlled individually.

[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 equal for each element pattern. Here, lx and ly may be equal or different. When lx and ly are different, characteristics for TE and TM polarization can be imparted to each element pattern individually.

[0048] The element pattern preferably has a surface resistance of 100Ω / □ or less. The material used for the element pattern is a conductive material such as an inorganic oxide material, a metal material, or a conductive organic material. For example, the inorganic oxide material and the metal material may be 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. Nanoparticles or nanowires containing at least one of these materials may also be used. The conductive organic material may be a polythiophene derivative, a polyacetylene derivative, a polyaniline derivative, a polypyrrole derivative, a carbon nanotube, or graphene. In particular, Cu or Al is preferable from the viewpoints of material cost, conductivity, and film formation. Also, a transparent reflect array can be produced by using ITO or a mixture (PEDOT / PSS) of polyethylenedioxythiophene (PEDOT) and polystyrenesulfonic acid (PSS). The thickness of the element pattern is, for example, 10 nm or more and 18 μm or less. From the viewpoints of flexibility, film-forming property, stability, sheet resistance value and low cost, it is preferable to use a film formed by vapor deposition as the element pattern.

[0049] The material of the element pattern may be the same as that of the ground layer described later, or a different material may be used. For example, at least one of the layers of the ground layer or the element pattern may be formed of Cu or Al. Cu has excellent conductivity, so that conductor loss can be reduced. Al has low density, is lightweight, and is low cost, so that a lightweight and inexpensive reflect array can be formed. In addition, the thickness of at least one of the layers can be 1 μm or less. By making the thickness 1 μm or less, flexibility is improved, making it easier to install the reflect array on a curved surface, and making it possible to achieve weight reduction.

[0050] The above materials can be used in the form of a continuous film, mesh, or punched shape.

[0051] Here, mesh refers to a state in which a conductor has a mesh-like opening (opening) on ​​its plane. When the conductor is formed in a mesh shape, the mesh may be rectangular or rhombic. When the mesh is formed in a rectangular shape, it is preferable that the mesh is square. Square meshes have good design properties. They may also be randomly shaped by a self-organizing method. Making the mesh random can prevent moire. When processing metal into a mesh shape, methods such as punching a metal plate or etching a metal plate can be used.

[0052] When the element pattern is mesh-shaped or when a transparent conductive material is used, the reflect array exhibits visible light transparency, making it possible to maintain the appearance after installation.

[0053] When the element pattern is in the form of a mesh, the line width of the mesh is preferably 5 μm to 30 μm, more preferably 6 μm to 15 μm. The line spacing of the mesh is preferably 50 μm to 500 μm, more preferably 100 μm to 300 μm. Furthermore, when the wavelength at the operating frequency is λ, the line spacing of the mesh is preferably 0.5×λ or less, more preferably 0.1×λ or less, and even more preferably 0.01×λ or less. If the line spacing of the mesh is 0.5×λ or less, the performance can be ensured. Furthermore, the line spacing of the mesh may be 0.001×λ or more.

[0054] When the element pattern is mesh-shaped or when a transparent conductive material is used, the reflect array exhibits visible light transparency, making it possible to maintain the appearance after installation.

[0055] When the element pattern is in the form of a thin film, the flexibility of the reflectarray can be improved, making it possible to use it on curved surfaces and to carry out a roll-to-roll production process.

[0056] When the element pattern is formed using a thin film, its thickness is preferably greater than twice the skin depth calculated from equation (11), where d is the skin depth, ω is the angular frequency, μ is the magnetic permeability of the material, and σ is the electrical conductivity of the material. If the thickness is less than twice the skin depth calculated from equation (11), part of the electromagnetic wave incident on the conductor is transmitted, resulting in poor reflection efficiency. More preferably, the thickness is greater than or close to twice the skin depth calculated from equation (11). In an element pattern having a thickness sufficiently greater than twice the skin depth calculated from equation (11), the current concentrates on the surface of the conductor due to the skin effect, with almost no current flowing in the center. Therefore, even if the thickness is greater than twice the skin depth in equation (11), the power transmission characteristics do not change significantly. The closer the value is to twice the skin depth calculated from equation (11), the more sufficient the power transmission characteristics can be provided and the lower the material costs can be produced.

number

[0057] Another advantage is that the loss due to the element pattern can be reduced in order to increase the reflection efficiency of electromagnetic waves. Therefore, it is preferable for the surface roughness of the element pattern to be small. At high frequencies, the skin effect causes current to concentrate on the surface portion of the conductor, resulting in a high current density on the conductor surface. This makes it susceptible to the effects of surface roughness, and the greater the surface roughness, the greater the conductor loss. In particular, when the surface roughness is greater than the skin depth, the conductor loss becomes significantly large. Therefore, it is preferable for the surface roughness to be small in order to suppress conductor loss.

[0058] (Dielectric layer) The dielectric layer may be made of a simple resin or a composite material such as paper, glass fiber, or carbon fiber impregnated with resin.

[0059] The relative dielectric constant of the dielectric layer is preferably in the range of 1 to 20, more preferably in the range of 1 to 10, and even more preferably in the range of 2 to 4. When the relative dielectric constant is within the above range, the desired reflection phase characteristics tend to be easily obtained in the reflectarray 1. In addition, the dielectric loss tangent is preferably in the range of 0.00005 to 0.01, and more preferably in the range of 0.00005 to 0.001. When it is within the above range, a reflectarray 1 with low dielectric loss can be produced.

[0060] Examples of single resins include polyethylene (εr = 2.2 to 2.4), polypropylene (εr = 2.0 to 2.6), polystyrene (εr = 2.4 to 2.6), polyvinyl chloride (εr = 2.8 to 8.0), AS resin (εr = 2.6 to 3.1), ABS resin (εr = 2.4 to 4.1), polyethylene terephthalate (εr = 2.9 to 3.0), acrylic resin (εr = 2.7 to 4.5), urethane resin (εr = 4.0 to 7.1), epoxy resin (εr = 2.5 to 6.0), nylon (εr =3.0-5.0), polyimide (εr=2.4-2.7), fluororesin (εr=2.0-2.6), polycarbonate (εr=2.9-8.9), polyphenylene ether (εr=2.8-8.2), polyphenylene sulfide (εr=3.2-4.6), polyvinylidene fluoride (εr=6.4-10.0), polyethylene naphthalate (εr=2.9), phenol resin (εr=3.0-12.0), cycloolefin polymer (εr=2.3-2.5), etc. are listed. Here, εr indicates the relative dielectric constant. In particular, it is preferable to use polyethylene terephthalate (PET) because it is inexpensive and has excellent versatility. The dielectric layer can be a single layer or multiple layers. The dielectric layer may be a foam obtained by foaming the above materials. As the foam, a foam with high flexibility is preferably used.

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

[0062] From the viewpoint of adjusting the dielectric constant, a mixture containing resin components or a dielectric compound and a resin component may be used. The relative dielectric constant of the mixture can be adjusted by selecting the dielectric compound and its content.

[0063] The dielectric constant of a mixture can be predicted, for example, by using the Maxwell-Garnett law. In a mixture of dielectric A with a dielectric constant εa and dielectric B with a dielectric constant εb, when the volume fraction of A is δa, the dielectric constant εm of the mixture is expressed by the relational expression (12).

number

[0064] Examples of the dielectric compound include barium titanate (εr=250 to 20000), titanium oxide (εr=83 to 183), lead zirconate titanate, strontium tantalate bismuthate, and bismuth ferrite.

[0065] When a transparent dielectric material is used, the reflect array exhibits visible light transmittance, making it possible to maintain the appearance after installation.

[0066] The thickness of the dielectric layer is appropriately selected depending on the design frequency. When the design frequency is 28 GHz, it is preferably 40 μm or more and 250 μm or less, and more preferably 50 μm or more and 200 μm or less. If it is too thin, it becomes difficult to ensure the reflection phase, and the design of the reflect array 1 becomes difficult. On the other hand, if it is too thick, it tends to be difficult to ensure the reflection phase, to lose flexibility, and to increase the total thickness of the reflect array, making it difficult to save space. For this reason, the thickness of the dielectric layer is preferably 250 μm or less. When the design frequency is 60 GHz, the thickness of the dielectric layer is preferably 10 μm or more and 250 μm or less. When the design frequency is 100 GHz or more, it is easy to design the reflect array if the thickness of the dielectric layer is about several μm or more and 100 μm or less.

[0067] The dielectric layer can be formed by, for example, wet coating such as die coating, comma coating, or gravure coating, melt extrusion methods such as a T-die method or an inflation method, a calendar film forming method, a solution casting method, a heat press method, etc. Also, a co-extrusion method in which a film is formed by extruding a plurality of resins in multiple layers may be used.

[0068] (Ground layer) The ground layer is provided to reflect electromagnetic waves that reach 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, inorganic oxide materials and metal materials include 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. Nanoparticles or nanowires containing at least one of these materials may also be used. Organic materials having electrical conductivity include polythiophene derivatives, polyacetylene derivatives, polyaniline derivatives, polypyrrole derivatives, carbon nanotubes, graphene, and the like. In particular, Cu and Al are preferred from the viewpoints of material cost, electrical conductivity, and film formability. Furthermore, in order to reflect electromagnetic waves, it is desirable for the surface resistance of the ground layer to be 100 Ω / □ or less. If this condition can be met, a transparent reflect array can be produced by using ITO or a mixture of polyethylenedioxythiophene (PEDOT) and polystyrene sulfonate (PSS) (PEDOT / PSS).

[0070] The above materials can be used in the form of a continuous film, mesh, punched shape, or periodic structure.

[0071] Here, mesh refers to a state in which a conductor has a mesh-like opening (opening) on ​​its plane. When the conductor is formed in a mesh shape, the mesh may be rectangular or rhombic. When the mesh is formed in a rectangular shape, it is preferable that the mesh is square. Square meshes have good design properties. They may also be randomly shaped by a self-organizing method. Making the mesh random can prevent moire. When processing metal into a mesh shape, methods such as punching a metal plate or etching a metal plate can be used.

[0072] When the ground layer is mesh-like or a transparent conductive material is used, the reflect array exhibits visible light transparency, making it possible to maintain the appearance after installation.

[0073] When the ground layer is in the form of a mesh, the line width of the mesh is preferably 5 μm to 30 μm, more preferably 6 μm to 15 μm. The line spacing of the mesh is preferably 50 μm to 500 μm, more preferably 100 μm to 300 μm. Furthermore, when the wavelength at the operating frequency is λ, the line spacing of the mesh is preferably 0.5×λ or less, more preferably 0.1×λ or less, and even more preferably 0.01×λ or less. If the line spacing of the mesh is 0.5×λ or less, performance can be ensured. Furthermore, the line spacing of the mesh may be 0.001×λ or more.

[0074] When a metal material is used, the method of forming the ground layer can be selected from dry coating such as sputtering or vapor deposition, wet coating such as gravure coating or die coating by turning the metal material into ink, surface treatment such as plating, etc. Alternatively, a rolled metal plate can be used as the ground layer. When an inorganic oxide material is used, dry coating can be selected as the method of forming the ground layer 11. When an organic material is used, wet coating can be selected as the method of forming the ground layer 11. It may also be formed by painting or spraying.

[0075] If the ground layer is in the form of a thin film formed by plating or vapor deposition, the flexibility of the reflect array can be improved, making it possible to use it on curved surfaces or implement a roll-to-roll production process.

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

[0077] In addition, in order to increase the reflection efficiency of electromagnetic waves, it is also necessary to reduce loss due to the ground layer, so it is preferable that the surface roughness of the ground layer is small.

[0078] When the ground layer has a periodic structure, it can selectively reflect or transmit a specific frequency. For example, when a structure in which patch-shaped conductive patterns are periodically arranged is used as the ground layer, it is possible to reflect only a specific frequency, and therefore it is possible to impart a function of transmitting frequencies other than the operating frequency. In addition, when a structure in which holes are periodically arranged where no conductive material exists is used, it is possible to design a reflect array that asymmetrically reflects the operating frequency while transmitting only a specific frequency.

[0079] (Manufacturing method) The main manufacturing method for the basic structure of a reflectarray is to form an element pattern by cutting or etching a copper-clad laminate used in printed circuit boards, or a dielectric layer having a metal film formed on one or both sides of the dielectric layer by dry coating using a vapor deposition or sputtering method, plating process, wet coating, etc. Specifically, a copper-clad laminate is made by laminating copper foil onto an insulator, which is a base material such as glass cloth impregnated with a resin such as epoxy. The copper-clad laminate has a plate shape, and copper foil is laminated onto both sides of the plate-shaped insulator. The copper foil on one side is used as the element pattern 1, and the copper foil on the other side is used as the ground layer 3. The insulator corresponds to the dielectric layer 2. When metal films are formed on both sides of a dielectric, the element pattern 1 is formed from one metal film, and the other metal film is applied to the ground layer 3. The dielectric becomes the dielectric layer 2.

[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 the element pattern 1, and FIG. 7(b) to FIG. 7(d) show cross-sectional views of the element pattern 1. As shown in FIG. 7(a), the element pattern 1 is formed by orthogonally forming a square patch having an element length lx and an element width wy and a square patch having an element length ly and an element width wx. Either dry etching or wet etching may be used for the etching method. When the etching method is used, corner rounding (FIG. 7(a)) or pinholes may occur in the element pattern 1. It is also assumed that a forward taper (FIG. 7(b)), a reverse taper (FIG. 7(c)), or rounding (FIG. 7(d)) ​​is formed in the cross-sectional view of the element pattern 1. In FIG. 7, the thickness of the element pattern 1 is t. When the etching method is used, the cross-sectional shape of the element pattern is preferably a forward taper shape with a base that spreads in the -z axis direction. The forward tapered shape increases the surface area of ​​the element pattern, making it possible to increase the adhesive strength with the functional layer when the functional layer is laminated, as described below.

[0081] 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, a printing method using letterpress printing, lithographic printing, intaglio printing, stencil printing, transfer printing, etc., or a method of masking the dielectric layer except for the element pattern portion with masking tape or a masking agent, etc., and forming the element pattern by dry coating, plating, painting, or spraying.

[0083] Lamination of other layers (functional layers such as protective layers, adhesive layers, design layers, installation layers, etc.) onto the basic structure can be achieved by lamination, printing / coating, or extrusion molding. Examples of lamination include, but are not limited to, dry lamination, wet lamination, thermal lamination, and extrusion lamination.

[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 area, and the reflection angle is the reflection angle θr of the electromagnetic wave reflected from the reflection control area. When the wavelength of the electromagnetic wave reflected from the reflection control area is λ, the reflection control area is designed to satisfy the following formula (1).

number

[0085] The reflection angle in the reflectarray must satisfy equation (2).

number

[0086] (Acceptable incident angle range) The incidence deviation angle indicates the incidence angle when a deviation occurs from the incidence angle (=0°) that satisfies formula (1). The incidence deviation angle is expressed as an angle in which the incidence angle that satisfies formula (1) is the reference (=0°), with the direction toward the +z axis being expressed as a positive angle (0° to -180°) and the direction toward the -z axis being expressed as a negative angle (0° to -180°). The allowable incident angle range indicates the angle width of the incident deviation angle within which the reflection intensity of the electromagnetic wave, which the reflection control area reflects to a reflection angle that satisfies formula (1) when the electromagnetic wave is incident from an incident angle that satisfies formula (1) (=0 dB), is within -3 dB. -3 dB indicates that the power is half of the reference. The -3 dB reference is used in the antenna industry as a reference for directivity, and is considered to be sufficient for communication within that range. The reflectarray can increase the allowable incident 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 allowable incident angle range is larger when the incident deviation angle is a positive value, and a wider allowable incident angle range can be secured. This is thought to be because the apparent area of ​​the reflectarray when viewed from the transmitter becomes smaller, so the amount of energy that hits the reflectarray is smaller, and the reflected power is therefore smaller. The allowable incident angle range Δθi is preferably greater than 5.5° and equal to or less than 16°. When the allowable incident angle range is smaller than 0.5°, it is necessary to accurately grasp the direction of the electromagnetic waves emitted from the transmitter. Also, when using an antenna with beamforming for the transmitter, more antenna elements must be placed in order to increase the angle precision of the beamforming, which leads to a larger area and higher costs for the transmitter. Also, when the allowable incident angle range is 16° or more, radio wave sources other than the transmitter are reflected, which can cause phase disturbance.

[0087] (Electromagnetic Wave Reflection System) An example of an electromagnetic wave reflection system and an installation method of a reflectarray will be described with reference to Fig. 8. Fig. 8 is a diagram showing an example of an electromagnetic wave reflection system using a reflectarray. For ease of explanation, Fig. 8 is used as an example for explanation, but the environment in which the electromagnetic wave reflection system is used is not limited to this. As shown in the example of Figure 8, if there is a shield 500, the electromagnetic waves radiated from the transmitter are blocked by the shield and cannot reach the receiver directly. The higher the frequency, the more linear the electromagnetic waves are, making it more difficult to get around to the back of the shield and deliver the electromagnetic waves. By using a reflectarray, the electromagnetic waves radiated primarily from the transmitter hit the reflectarray, and the electromagnetic waves radiated secondarily from the reflectarray hit the receiver, allowing the electromagnetic waves to be delivered from the transmitter to the receiver. Generally, when using a passive reflector, when constructing an electromagnetic wave reflection system, the usage environment is checked in advance, the installation location of the passive reflector and the angle of incidence and reflection are calculated, and the passive reflector is designed based on that. In this case, if the confirmation in advance is not accurate, the maximum effect cannot be achieved. In addition, accurate angle adjustment is required when installing the passive reflector. Here, by using the reflectarray disclosed herein, within the range of incident angle and reflection angle that satisfies equation (2), electromagnetic waves incident on the reflectarray can be reflected in the reflection angle direction even if an incident deviation angle occurs, and the allowable incident angle range can be made wide, making it easy to construct an electromagnetic wave reflection system.

[0088] (How to install a reflectarray) The reflectarray is preferably installed along a wall or the like in order to save installation space. Specifically, in FIG. 8, installation on a wall 200 and a wall 201 is assumed. The reflectarray installed on the wall 200 is designated as 61, and the reflectarray installed on the wall 201 is designated as 62. The reflectarray 61 is an installation method that satisfies the formula (2), and the reflectarray 62 is an installation method that does not satisfy the formula (2). The installation method of the reflectarray 62 requires high accuracy to determine the positional relationship between the transmitter and the reflectarray 62, and if there is a deviation in the installation position, the power that the receiver can receive changes significantly. By installing the reflectarray 61 on the wall 200, the allowable incident angle range is widened, and the electromagnetic waves incident from this angle range can be reflected toward the receiver with a stable reflection intensity. Considering practical use, for example, the accuracy of the installation position of the reflectarray during construction is relaxed, making construction easier. Furthermore, when an antenna having beamforming is used for the transmitter, it is expected that the accuracy of the beamforming can be relaxed.

[0089] (Support) The reflectarray is installed on a support. FIG. 9 is a diagram showing an example of a reflectarray 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. In order to save installation space, it is preferable to use it 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 may be provided, or the element or ground layer may be made into a mesh to give transparency. In addition, when a new panel or pole is installed as shown in FIG. 9(b), it is preferable to have a mechanism that can adjust the angle of the reflectarray in the vertical or horizontal direction, and more preferably to have a mechanism that moves the position of the reflectarray up, down, left, and right. The reflectarray is installed on a support and used as a reflectarray device.

[0090] (installation layer) The mounting layer is a layer for fixing the reflectarray to the support. For example, an adhesive layer, a sticky layer, or a magnet can be used when the support is made of metal.

[0091] (Design layer) The design layer is a layer for imparting design to the surface of the reflectarray. For example, when used as a building material such as wallpaper, a design layer may be further provided to harmonize with the space. When used as a whiteboard, a functional film may be used as the design layer. The design layer may be given the function of the protective layer described below.

[0092] (protective layer) For the protective layer, a film or sheet having gas barrier properties, water vapor barrier properties, water resistance, abrasion resistance, and scratch resistance may be used to prevent oxidation deterioration, physical damage, and peeling of the element pattern and ground layer.

[0093] When it is assumed that the reflectarray will be used indoors, it is preferable to use a protective layer that has antibacterial properties, antiviral properties, contamination resistance, etc. When it is assumed that the reflectarray will be used outdoors, weather resistance is required, so a layer containing UVA (ultraviolet absorber) or HALS (light stabilizer) may be used.

[0094] [Evaluation results (Examples and Comparative Examples)] The results of Examples 1-4 and Comparative Examples 1-4 are summarized in Table 1, and the results of Examples 5-10 and Comparative Examples 5-10 are summarized in Table 2. The comparative examples used here compare the same reflectarrays that satisfy formula (2) with those that do not, in order to show that the reflectarray of the present disclosure has a wide incident angle range at a specific incident angle. The ease of installation in Tables 1 and 2 is an index showing the tolerance for installation error of the reflectarray. When the distance between the transmitter and the reflectarray is 5m, if the reflected array is moved 45cm and the drop in received power is within -3dB, it is marked as ◯, and if the drop in received power is greater than -3dB, it is marked as ×. When the reflector has an asymmetrical reflection in the x-axis direction, the direction in which the reflectarray is moved is to move it parallel to the x-axis. Reception stability is an index showing the stability of the received power at the reflection angle that satisfies formula (1) when the transmitter is moved. The transmitter is moved so that the incident deviation angle changes, and if the angle width (i.e., the incident allowable angle range) at which the received power at the reflection angle becomes -3 dB is 5.5° or less, the received power is judged as unstable and is marked as X, and if it is greater than 5.5° and less than 16°, the received power is judged as stable and is marked as ◯. [Table 1] [Table 2]

[0095] Example 1 A reflect array 6 with a basic configuration was constructed using 0.018 mm thick copper for the element pattern 1 and ground layer 3, and a 0.764 mm thick glass / fluororesin composite material for the dielectric layer 2. However, the conductivity of copper was set to 5.8×10^7siemens / m, the real part of the relative dielectric constant of the dielectric layer 2 was set to 2.6, and tan δ was set to 0.0025.

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

[0097] The number of divisions of the reflection control region 5 was set to 3, and the size of the unit cell in the x-axis direction and the y-axis direction was set to 3.785 mm. The shape of the element pattern was a cross patch in which two square patches were orthogonal to each other in the xy plane. Here, the element length and element width were different in each element pattern in the reflection control region 5, and the element length and element width in the x-axis direction and the y-axis direction were set to be the same in the same element pattern. Specifically, the element lengths were set to lx1=ly1, lx2=ly2, and lx3=ly3, and the element widths were set to wx1=wy1, wx2=wy2, and wx3=wy3. In Tables 1 and 2 and in the figures and text in the following description, the unit cells included in reflection control region 5 are represented as unit cell 1, unit cell 2, ... unit cell p (p is an integer between 1 and the number of divisions n), and in unit cell p, the element length in the x-axis direction is lxp, the element length in the y-axis direction is lyp, the element width in the x-axis direction is wxp, and the element width in the y-axis direction is wyp. However, when lxp and lyp are equal, the subscripts x and y are omitted, and when wxp and wyp are equal, the subscripts x and y are omitted, and when the unit cell is not specified, the subscript p may be omitted.

[0098] The reflection phase of the unit cell for each element width w and element length l was analyzed using finite element analysis software (HFSS) made by Ansys. It was confirmed that the reflection phase changes as the element width w or element length l changes when the element width w or element length l is 1.400 mm.

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

[0100] The reflectarray 6 has reflection control areas arranged in the x-axis and y-axis directions as 8 × 6, and its size in the xy plane is 121.12 mm × 90.840 mm. The reflection characteristics when the reflectarray 6 is irradiated with polarized waves parallel to the y-axis at θix = -45° and θrx = 0° were analyzed using HFSS.

[0101] In order to grasp the allowable range of incident angles, a similar analysis was performed when the angle was changed in 2° increments in the range of -65°≦θix≦-25°.

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

[0103] Comparative Example 1 A reflectarray was prepared that was the same as the reflectarray described in Example 1 except for the incident angle θix and the reflection angle θrx. 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.

[0104] In order to grasp the allowable range of incident angles, a similar analysis was performed when the angle was changed in 2° increments in the range of -20°≦θix≦20°.

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

[0106] 12 shows a comparison result of the amount of change in power that can be received at a specific reflection angle θrx when the incidence angle is changed in each of Example 1 and Comparative Example 1. The horizontal axis of FIG. 12 represents the incidence deviation angle, and the vertical axis represents the The axis represents the change in RCS when the RCS is 0 dB when the incident deviation angle is 0°. Specifically, in the first embodiment, when the incident deviation angle is 0°, θix=-45°, and the angle when it is changed by -65°≦θix≦-25° is shown on the horizontal axis of FIG. 12 as -20°≦incident deviation angle≦20°. The vertical axis shows how much the RCS has changed compared to the incident deviation angle=0°, with the RCS (-0.02 dBsm) at θrx=0° being 0 dB. This is synonymous with showing how much the received power at the reflection angle point has changed. In addition, in the first comparative example, when the incident deviation angle is 0°, θix=0°, and the angle when it is changed by -20°≦θix≦20° is shown on the horizontal axis of FIG. 12 as -20°≦incident deviation angle≦20°. The vertical axis shows how much the RCS has changed compared to the incident deviation angle=0°, with the RCS (-0.28 dBsm) at θrx=-45° being 0 dB. The dotted line at -3 dB indicates the range of allowable incident angles.

[0107] From the results of Fig. 12, the allowable incident angle range was 6.2° in Example 1 and 4.2° in Comparative Example 1. As a result of confirming the ease of installation, in Example 1, even if the reflect array was moved by 45 cm, the change in the received power was within -3 dB in the direction of the receiving angle that satisfied formula (1), whereas in Comparative Example 1, the change was greater than -3 dB. Furthermore, as a result of confirming the reception stability, in Example 1, the received power was stable in a range of the allowable incident angle range greater than 5.5°, whereas in Comparative Example 1, the received power was unstable in a range of the allowable incident angle range of 5.5° or less.

[0108] Example 2 A reflect array 6 with a basic configuration was constructed using 0.018 mm thick copper for the element pattern 1 and ground layer 3, and a 0.764 mm thick glass / fluororesin composite material for the dielectric layer 2. However, the conductivity of copper was set to 5.8×10^7siemens / m, the real part of the relative dielectric constant of the dielectric layer 2 was set to 2.6, and tan δ was set to 0.0025.

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

[0110] The number of divisions of the reflection control region 5 was set to 3, and the size of the unit cell in the x-axis direction and the y-axis direction was set to 4.659 mm. The shape of the element pattern was a cross patch in which two square patches were orthogonal to each other in the xy plane. Here, the element length and element width were different in each element pattern in the reflection control region 5, and the element length and element width in the x-axis direction and the y-axis direction were set to be the same in the same element pattern. Specifically, the element lengths were set to lx1=ly1, lx2=ly2, and lx3=ly3, and the element widths were set to wx1=wy1, wx2=wy2, and wx3=wy3.

[0111] The reflection phase of the unit cell for each element width w and element length l was analyzed using finite element analysis software (HFSS) made 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 of each unit cell was determined to follow the impedance distribution of equation (9). The element lengths l were lx1=ly1=3.790mm, lx2=ly2=2.775mm, and lx3=ly3=2.065mm, and the element widths were wx1=wy1=2.303mm, wx2=wy2=2.217mm, and wx3=wy3=2.024mm, respectively.

[0113] The reflectarray 6 has reflection control areas arranged in the x-axis and y-axis directions as 8 × 6, and its size in the xy plane is 111.816 mm × 27.954 mm. The reflection characteristics when the reflectarray 6 is irradiated with polarized waves parallel to the y-axis at θix = -50° and θrx = 0° were analyzed using HFSS.

[0114] In order to grasp the allowable incident angle range, a similar analysis was performed when the angle was changed in 2° intervals in the range of -70°≦θix≦-30°.

[0115] Fig. 13 shows the analysis results of the reflectarray 6 obtained in Example 2. In Fig. 13, the horizontal axis represents the reflection angle θrx, and the vertical axis represents 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 the RCS was -1.82 dBsm.

[0116] Comparative Example 2 A reflectarray was prepared that was the same as the reflectarray described in Example 2 except for the incident angle θix and the reflection angle θrx. 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 allowable range of incident angles, a similar analysis was performed when the angle was changed in 2° increments in the range of -20°≦θix≦20°.

[0118] 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 the RCS was −1.89 dBsm.

[0119] FIG. 15 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 2 and Comparative Example 2.

[0120] From the results of Fig. 15, the allowable incident angle range was 7.4° in Example 2 and 4.5° in Comparative Example 2. As a result of confirming the ease of installation, in Example 2, even if the reflectarray was moved by 45 cm, the change in the received power was within -3 dB in the direction of the receiving angle that satisfied formula (1), whereas in Comparative Example 2, the change was greater than -3 dB. Furthermore, as a result of confirming the reception stability, in Example 2, the received power was stable in a range of the allowable incident angle range greater than 5.5°, whereas in Comparative Example 2, the received power was unstable in a range of the allowable incident angle range of 5.5° or less.

[0121] Example 3 A reflect array 6 with a basic configuration was constructed using 0.018 mm thick copper for the element pattern 1 and ground layer 3, and a 0.764 mm thick glass / fluororesin composite material for the dielectric layer 2. However, the conductivity of copper was set to 5.8×10^7siemens / m, the real part of the relative dielectric constant of the dielectric layer 2 was set to 2.6, and tan δ was set to 0.0025.

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

[0123] The number of divisions of the reflection control region 5 was set to 3, and the size of the unit cell in the x-axis direction and the y-axis direction was set to 4.121 mm. The shape of the element pattern was a cross patch in which two square patches were orthogonal to each other in the xy plane. Here, the element length and element width were different in each element pattern in the reflection control region 5, and the element length and element width in the x-axis direction and the y-axis direction were set to be the same in the same element pattern. Specifically, the element lengths were set to lx1=ly1, lx2=ly2, and lx3=ly3, and the element widths were set to wx1=wy1, wx2=wy2, and wx3=wy3.

[0124] The reflection phase of the unit cell for each element width w and element length l was analyzed using finite element analysis software (HFSS) made by Ansys. It was confirmed that the reflection phase changes as the element width w or element length l changes.

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

[0126] The reflectarray 6 has reflection control areas arranged in the x-axis and y-axis directions as 8 × 6, and its size in the xy plane is 98.904 mm × 24.726 mm. The reflection characteristics when the reflectarray 6 is irradiated with polarized waves parallel to the y-axis at θix = -60° and θrx = 0° were analyzed using HFSS.

[0127] In order to grasp the allowable incident angle range, a similar analysis was performed when the angle was changed in 2° intervals in the range of -80°≦θix≦-40°.

[0128] Fig. 16 shows the analysis results of the reflectarray 6 obtained in Example 3. In Fig. 16, the horizontal axis represents the reflection angle θrx, and the vertical axis represents 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 the RCS was -6.14 dBsm.

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

[0130] In order to grasp the allowable range of incident angles, a similar analysis was performed when the angle was changed in 2° increments in the range of -20°≦θix≦20°.

[0131] 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 the RCS was -6.22 dBsm.

[0132] FIG. 17 shows the comparison results 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 3 and Comparative Example 3.

[0133] From the results of Fig. 18, the allowable incident angle range was 10.8° in Example 3 and 5.1° in Comparative Example 3. As a result of confirming the ease of installation, in Example 3, even if the reflect array was moved by 45 cm, the change in the received power was within -3 dB in the direction of the receiving angle that satisfied formula (1), whereas in Comparative Example 3, the change was greater than -3 dB. Furthermore, as a result of confirming the reception stability, in Example 3, the received power was stable in a range of the allowable incident angle range greater than 5.5°, whereas in Comparative Example 3, the received power was unstable in a range of the allowable incident angle range of 5.5° or less.

[0134] Example 4 A reflect array 6 with a basic configuration was constructed using 0.018 mm thick copper for the element pattern 1 and ground layer 3, and a 0.764 mm thick glass / fluororesin composite material for the dielectric layer 2. However, the conductivity of copper was set to 5.8×10^7siemens / m, the real part of the relative dielectric constant of the dielectric layer 2 was set to 2.6, and tan δ was set to 0.0025.

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

[0136] The number of divisions of the reflection control region 5 was set to 3, and the size of the unit cell in the x-axis direction and the y-axis direction was set to 3.798 mm. The shape of the element pattern was a cross patch in which two square patches were orthogonal to each other in the xy plane. Here, the element length and element width were different in each element pattern in the reflection control region 5, and the element length and element width in the x-axis direction and the y-axis direction were set to be the same in the same element pattern. Specifically, the element lengths were set to lx1=ly1, lx2=ly2, and lx3=ly3, and the element widths were set to wx1=wy1, wx2=wy2, and wx3=wy3.

[0137] The reflection phase of the unit cell for each element width w and element length l was analyzed using finite element analysis software (HFSS) made by Ansys. It was confirmed that the reflection phase changes as the element width w or element length l changes.

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

[0139] The reflectarray 6 has reflection control areas arranged in the x-axis and y-axis directions as 8 × 6, and its size in the xy plane is 91.152 mm × 22.788 mm. The reflection characteristics when the reflectarray 6 is irradiated with polarized waves parallel to the y-axis at θix = -70° and θrx = 0° were analyzed using HFSS.

[0140] In order to grasp the allowable incident angle range, a similar analysis was performed when the angle was changed in 2° increments in the range of -90°≦θix≦-50°.

[0141] Fig. 19 shows the analysis results of the reflectarray 6 obtained in Example 4. In Fig. 19, the horizontal axis represents the reflection angle θrx, and the vertical axis represents 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 the RCS was -15.56 dBsm.

[0142] Comparative Example 4 A reflectarray similar to the reflectarray described in Example 4 was prepared except for the incident angle θix and the reflection angle θrx. 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 allowable range of incident angles, a similar analysis was performed when the angle was changed in 2° increments in the range of -20°≦θix≦20°.

[0144] 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 the RCS was -15.56 dBsm.

[0145] FIG. 21 shows the comparison results 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 4 and Comparative Example 4.

[0146] From the results of Fig. 21, the allowable incident angle range was 15.3° in Example 4 and 5.5° in Comparative Example 4. As a result of confirming the ease of installation, in Example 4, even if the reflectarray was moved by 45 cm, the change in the received power was within -3 dB in the direction of the receiving angle that satisfied formula (1), whereas in Comparative Example 4, the change was greater than -3 dB. Furthermore, as a result of confirming the reception stability, in Example 4, the received power was stable in a range of the allowable incident angle range greater than 5.5°, whereas in Comparative Example 4, the received power was unstable in a range of the allowable incident angle range of 5.5° or less.

[0147] From the results of Examples 1-4 and Comparative Examples 1-4, it was found that the allowable incident angle range is large in the range that satisfies formula (2). Fig. 22 shows a relationship diagram between the absolute value of the incident angle that satisfies formula (1) and the allowable incident angle range in the case of the Examples, and a relationship diagram between the absolute value of the reflection angle that satisfies formula (1) and the allowable incident angle range in the case of the Comparative Examples. From the results of Fig. 22, it was found that in this example, the allowable incident angle range becomes larger as |θi| becomes larger.

[0148] Using Examples 5-7 and Comparative Examples 5-7, frequency dependence is confirmed. Example 5 A reflect array 6 with a basic configuration was constructed using 0.018 mm thick copper for the element pattern 1 and ground layer 3, and a 1.564 mm thick glass / epoxy resin composite material for the dielectric layer 2. However, the conductivity of copper was set to 5.8×10^7siemens / m, the real part of the relative dielectric constant of the dielectric layer 2 was set to 4.5, and tan δ was set to 0.014.

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

[0150] The number of divisions of the reflection control region 5 was set to 4, and the size of the unit cell in the x-axis direction and the y-axis direction was set to 16.445 mm. The shape of the element pattern was a cross patch in which two rectangular patches were orthogonal to each other in the xy plane. Here, the element length and element width were different in each element pattern in the reflection control region 5, and the element length and element width in the x-axis direction and the y-axis direction were set to be the same in the same element pattern. Specifically, the element lengths were set to lx1=ly1, lx2=ly2, lx3=ly3, and lx4=ly4, and the element widths were set to wx1=wy1, wx2=wy2, wx3=wy3, and wx4=wy4.

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

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

[0153] The reflectarray 6 has reflection control areas arranged in the x-axis and y-axis directions as 8 × 6, and its size in the xy plane is 206.240 mm × 38.670 mm. The reflection characteristics when the reflectarray 6 is irradiated with polarized waves parallel to the y-axis at θix = -70° and θrx = 0° were analyzed using HFSS.

[0154] In order to grasp the allowable incident angle range, a similar analysis was performed when the angle was changed in 2° increments in the range of -90°≦θix≦-50°.

[0155] Fig. 23 shows the analysis results of the reflectarray 6 obtained in Example 5. In Fig. 23, the horizontal axis represents the reflection angle θrx, and the vertical axis represents 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 the RCS was 2.13 dBsm.

[0156] Comparative Example 5 Other than the incident angle θix and the reflection angle θrx, it is the same as the reflect array described in Example 5. A reflectarray 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.

[0157] In order to grasp the allowable range of incident angles, a similar analysis was performed when the angle was changed in 2° increments in the range of -20°≦θix≦20°.

[0158] 24 shows the analysis results of the reflectarray 6 obtained in Comparative Example 5. In the reflectarray 6 of Example 5, the electromagnetic wave incident at θix=0° was reflected in the desired direction of θrx=−70°, and the RCS was 2.07 dBsm.

[0159] FIG. 25 shows a comparison result 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 5 and Comparative Example 5.

[0160] From the results of Fig. 25, the allowable incident angle range was 15.4° in Example 5 and 5.5° in Comparative Example 5. As a result of confirming the ease of installation, in Example 5, even if the reflect array was moved by 45 cm, the change in the received power was within -3 dB in the direction of the receiving angle that satisfied formula (1), whereas in Comparative Example 5, the change was greater than -3 dB. Furthermore, as a result of confirming the reception stability, in Example 5, the received power was stable in a range of the allowable incident angle range greater than 5.5°, whereas in Comparative Example 5, the received power was unstable in a range of the allowable incident angle range of 5.5° or less.

[0161] Example 6 A reflect array 6 with a basic configuration was constructed using 0.018 mm thick copper for the element pattern 1 and ground layer 3, and a 0.200 mm thick fluororesin material for the dielectric layer 2. However, the conductivity of copper was set to 5.8×10^7siemens / m, the real part of the relative dielectric constant of the dielectric layer 2 was set to 2.06, and tan δ was set to 0.0007.

[0162] The operating frequency was set to 60 GHz, the target reflection characteristics (desired reflection characteristics) were set to θix = -45°, θrx = 0°, and θiy = θry = 0°, and the size Lx of the reflection control region 5 in the x-axis direction was determined to be 7.065 mm using equation (3).

[0163] The number of divisions of the reflection control region 5 was set to 3, and the size of the unit cell in the x-axis direction and the y-axis direction was set to 2.355 mm. The shape of the element pattern was a cross patch in which two square patches were orthogonal to each other in the xy plane. Here, the element length and element width were different in each element pattern in the reflection control region 5, and the element length and element width in the x-axis direction and the y-axis direction were set to be the same in the same element pattern. Specifically, the element lengths were set to lx1=ly1, lx2=ly2, and lx3=ly3, and the element widths were set to wx1=wy1, wx2=wy2, and wx3=wy3.

[0164] The reflection phase of the unit cell for each element width w and element length l was analyzed using finite element analysis software (HFSS) made by Ansys. It was confirmed that the reflection phase changes as the element width w or element length l changes.

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

[0166] The reflectarray 6 has reflection control areas arranged in the x-axis and y-axis directions as 8 × 6, and its size in the xy plane is 62.184 mm × 15.546 mm. The reflection characteristics when the reflectarray 6 is irradiated with polarized waves parallel to the y-axis at θix = -45° and θrx = 0° were analyzed using HFSS.

[0167] In order to grasp the allowable range of incident angles, a similar analysis was performed when the angle was changed in 2° increments in the range of -65°≦θix≦-25°.

[0168] Fig. 26 shows the analysis results of the reflectarray 6 obtained in Example 6. In Fig. 26, the horizontal axis represents the reflection angle θrx, and the vertical axis represents 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 the RCS was -6.86 dBsm.

[0169] Comparative Example 6 A reflectarray similar to the reflectarray described in Example 6 was prepared except for the incident angle θix and the reflection angle θrx. 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 allowable range of incident angles, a similar analysis was performed when the angle was changed in 2° increments in the range of -20°≦θix≦20°.

[0171] 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 the RCS was -6.94 dBsm.

[0172] FIG. 28 shows the comparison results 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 6 and Comparative Example 6.

[0173] From the results of Fig. 28, the allowable incident angle range was 6.1° in Example 6 and 4.2° in Comparative Example 6. As a result of confirming the ease of installation, in Example 6, even if the reflectarray was moved by 45 cm, the change in the received power was within -3 dB in the direction of the receiving angle that satisfied formula (1), whereas in Comparative Example 6, the change was greater than -3 dB. Furthermore, as a result of confirming the reception stability, in Example 6, the received power was stable in a range of the allowable incident angle range greater than 5.5°, whereas in Comparative Example 6, the received power was unstable in a range of the allowable incident angle range of 5.5° or less.

[0174] Example 7 A reflect array 6 with a basic configuration was constructed using 0.018 mm thick copper for the element pattern 1 and ground layer 3, and a 0.200 mm thick fluororesin material for the dielectric layer 2. However, the conductivity of copper was set to 5.8×10^7siemens / m, the real part of the relative dielectric constant of the dielectric layer 2 was set to 2.06, and tan δ was set to 0.0007.

[0175] The operating frequency was set to 60 GHz, the target reflection characteristics (desired reflection characteristics) were set to θix = -70°, θrx = 0°, and θiy = θry = 0°, and the size Lx of the reflection control region 5 in the x-axis direction 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 size of the unit cell in the x-axis direction and the y-axis direction was set to 1.772 mm. The shape of the element pattern was a cross patch in which two square patches were orthogonal to each other in the xy plane. Here, the element length and element width were different in each element pattern in the reflection control region 5, and the element length and element width in the x-axis direction and the y-axis direction were set to be the same in the same element pattern. Specifically, the element lengths were set to lx1=ly1, lx2=ly2, and lx3=ly3, and the element widths were set to wx1=wy1, wx2=wy2, and wx3=wy3.

[0177] The reflection phase of the unit cell for each element width w and element length l was analyzed using finite element analysis software (HFSS) made 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 of each unit cell was determined to follow the impedance distribution of equation (9). The element lengths l were lx1=ly1=1.310mm, lx2=ly2=1.570mm, and lx3=ly3=1.459mm, and the element widths were wx1=wy1=1.100mm, wx2=wy2=1.100mm, and wx3=wy3=1.100mm, respectively.

[0179] The reflectarray 6 has reflection control areas arranged in the x-axis and y-axis directions as 8 × 6, and its size in the xy plane is 42.528 mm × 10.632 mm. The reflection characteristics when the reflectarray 6 is irradiated with polarized waves parallel to the y-axis at θix = -70° and θrx = 0° were analyzed using HFSS.

[0180] In order to grasp the allowable incident angle range, a similar analysis was performed when the angle was changed in 2° increments in 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 is the reflection angle θrx, and the vertical axis is the RCS. In the reflectarray 6 of Example 7, the electromagnetic wave incident at θix = -70° is reflected in the desired direction of θrx = 0°, and the RCS is -8.84 dBsm.

[0182] Comparative Example 7 A reflectarray similar to the reflectarray described in Example 7 was prepared except for the incident angle θix and the reflection angle θrx. 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.

[0183] In order to grasp the allowable range of incident angles, a similar analysis was performed when the angle was changed in 2° increments in 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 comparison results 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 allowable incident angle range was 15.1° in Example 7 and 5.4° in Comparative Example 7. As a result of confirming the ease of installation, in Example 7, even if the reflectarray was moved by 45 cm, the change in the received power was within -3 dB in the direction of the receiving angle that satisfied formula (1), whereas in Comparative Example 7, the change was greater than -3 dB. Furthermore, as a result of confirming the reception stability, in Example 7, the received power was stable in a range of the allowable incident angle range greater than 5.5°, whereas in Comparative Example 7, the received power was unstable in a range of the allowable incident angle range of 5.5° or less.

[0187] Comparisons between Example 1 (Comparative Example 1) and Example 6 (Comparative Example 6), and between Example 4 (Comparative Example 4) and Example 5 (Comparative Example 5), and Example 7 (Comparative Example 7) revealed that there is no significant difference in the allowable incident angle range depending on the frequency.

[0188] Using Example 8 and Comparative Example 8, the effect of the reflection angle is confirmed. Example 8 A reflect array 6 with a basic configuration was constructed using 0.018 mm thick copper for the element pattern 1 and ground layer 3, and a 0.764 mm thick glass / fluororesin composite material for the dielectric layer 2. However, the conductivity of copper was set to 5.8×10^7siemens / m, the real part of the relative dielectric constant of the dielectric layer 2 was set to 2.6, and tan δ was set to 0.0025.

[0189] The operating frequency was set to 28 GHz, the target reflection characteristics (desired reflection characteristics) were set to θix = 70°, θrx = -30°, and θiy = θry = 0°, and the size Lx of the reflection control area 5 in the x-axis direction 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 size of the unit cell in the x-axis direction and the y-axis direction was set to 4.058 mm. The shape of the element pattern was a cross patch in which two square patches were orthogonal to each other in the xy plane. Here, the element length and element width were different in each element pattern in the reflection control region 5, and the element length and element width in the x-axis direction and the y-axis direction were set to be the same in the same element pattern. Specifically, the element lengths were set to lx1=ly1, lx2=ly2, lx3=ly3, lx4=ly4, lx5=ly5, and lx6=ly6, and the element widths were set to wx1=wy1, wx2=wy2, wx3=wy3, wx4=wy4, wx5=wy5, and wx6=wy6.

[0191] The reflection phase of the unit cell for each element width w and element length l was analyzed using finite element analysis software (HFSS) made by Ansys. It was confirmed that the reflection phase changes as the element width w or element length l changes.

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

[0193] The reflectarray 6 has reflection control areas arranged in the x-axis and y-axis directions as 8 × 6, and the size in the xy plane is 194.784 mm × 146.008 mm. The reflection characteristics when the reflectarray 6 is irradiated with polarized waves parallel to the y-axis at θix = 70° and θrx = -30° were analyzed using HFSS.

[0194] In order to grasp the allowable range of incident angles, a similar analysis was performed when the angle was changed in 2° increments within the range of 50°≦θix≦90°.

[0195] Fig. 32 shows the analysis results of the reflectarray 6 obtained in Example 8. In Fig. 32, the horizontal axis represents the reflection angle θrx, and the vertical axis represents 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 the RCS was -1.19 dBsm.

[0196] Comparative Example 8 A reflectarray similar to the reflectarray described in Example 8 was prepared except for the incident angle θix and the reflection angle θrx. 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 allowable range of incident angles, a similar analysis was performed when the angle was changed in 2° increments in the range of -20°≦θix≦20°.

[0198] 33 shows the analysis results 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 the RCS was -1.86 dBsm.

[0199] FIG. 34 shows the comparison results 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 8 and Comparative Example 8.

[0200] From the results of Fig. 34, the allowable incident angle range was 8.3° in Example 8 and 2.5° in Comparative Example 8. As a result of confirming the ease of installation, in Example 8, even if the reflectarray was moved by 45 cm, the change in the 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 confirming the reception stability, in Example 8, the received power was stable in a range of the allowable incident angle range greater than 5.5°, whereas in Comparative Example 8, the received power was unstable in a range of the allowable incident angle range of 5.5° or less.

[0201] [Other embodiments] Although the embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned embodiment and examples, and various modifications are possible without departing from the gist of the present invention. The following are some 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 a reflected electromagnetic wave 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 incident allowable angle range Δθi is in the range of more than 5.5° and 16° or less.

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[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 layers, 3 Ground layer, 4, 41-4 n, 4a-4c, 4 x 1-4 x n , 4 y 1-4 y n Unit cell, 5 reflex control area, 6, 61-62 Reflectarray, 200, 201 Wall, 300 transmitters, 400 receivers, 500 cover, 501 Building (cover), 600 Support 601 Support position adjustment jig

Claims

1. A method for installing a transmitter or a receiver in an electromagnetic wave reflection system in which an electromagnetic wave incident from a transmitter and reflected by a reflect array is received by a receiver, comprising: The reflect array has a reflection control region that controls a phase, The reflection control area satisfies the following formula (1), where L is the length of the long side, λ is the wavelength of the reflected electromagnetic wave, θi is the angle of incidence, and θr is the angle of reflection: A method for installing a transmitter or a receiver, comprising installing the transmitter or the receiver such that 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). [0010] [0025]

2. 2. The transmitter or receiver installation method according to claim 1, wherein an allowable incident angle range Δθi of the reflect array is greater than 5.5° and less than or equal to 16°.

3. The transmitter or receiver installation method according to claim 1 or 2, wherein the reflect array reflects electromagnetic waves of 3 GHz to 60 GHz.

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