JP7525011B1 - Reflectarray, electromagnetic wave reflection system, and reflectarray installation method - Google Patents

Abstract

[Problem] To provide a reflectarray, an electromagnetic wave reflection system, and a method for installing a reflectarray that can reflect electromagnetic waves incident from a wide angle range at a specific reflection angle. [Solution] A reflectarray 61, 62 that reflects electromagnetic waves has a reflection control area that controls the phase, and the reflection control area satisfies the following formula (1) 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, and the incident angle |θi| is in the range of 45° to 70°, and the incident angle θi and the reflection angle θr satisfy the relationship of the following formula (2), and the incident allowable angle range Δθi is in the range of more than 5.5° to 16°. TIFF0007525011000026.tif13170TIFF0007525011000027.tif13170[Selected Figure] Figure 8

Description

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

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 bend 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 problems.

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 have no electrical control mechanism and in which the directions of incident and reflected electromagnetic waves are determined at the design stage, and the dimensions and material properties of the element are designed based on that (e.g., Patent Document 2).

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.

Patent Document 2 also introduces a metasurface reflector that includes a metal ground layer provided 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.

Patent No. 6438857 JP 2021-48465 A

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.

To solve the above problem, a representative reflectarray of the present invention is a reflectarray that reflects electromagnetic waves, and has a reflection control area that controls the phase, and the reflection control area satisfies formula (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° to 70°, and the incident angle θi and the reflection angle θr satisfy the relationship of formula (2) (described below), and the allowable incident angle range Δθi is in the range of more than 5.5° to 16°.

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.

FIG. 1a is a diagram showing the overall configuration of a reflect array. FIG. 1b is an enlarged view of the reflection control area. FIG. 2 is a diagram showing the angles of incidence and reflection when a reflect array is arranged on an xy plane. FIG. 3 is a diagram showing an example of a layer configuration of the reflect array 6. As shown in FIG. 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. FIG. 5 is a diagram showing an example of the arrangement of unit cells according to the direction in which asymmetric reflection is to be generated. FIG. 6 is a diagram showing the configuration of an element pattern. FIG. 7 is a diagram showing an example of the shape of an element pattern after etching. FIG. 8 is a diagram showing an example of an electromagnetic wave reflection system using a reflect array. FIG. 9 is a diagram showing an example of a reflect array installed on a support. FIG. 10 is a diagram showing the analysis result of the reflect array obtained in Example 1, and is a diagram showing the reflection pattern of the reflect array when θix=−45° and θrx=0°. FIG. 11 is a diagram showing the analysis results of the reflect array obtained in Comparative Example 1, and is a diagram showing the reflection pattern of the reflect array when θix=0° and θrx=−45°. 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 incidence angle is changed in each of Example 1 and Comparative Example 1. FIG. 13 is a diagram showing the analysis results of the reflect array obtained in Example 2, and is a diagram showing the reflection pattern of the reflect array when θix=−50° and θrx=0°. 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°. 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. FIG. 16 is a diagram showing the analysis results of the reflectarray obtained in Example 3, and is a diagram showing the reflection pattern of the reflectarray when θix=−60° and θrx=0°. FIG. 17 is a diagram showing the analysis results of the reflect array obtained in Comparative Example 3, and is a diagram showing the reflection pattern of the reflect array when θix=0° and θrx=−60°. 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. FIG. 19 is a diagram showing the analysis results of the reflect array obtained in Example 4, and is a diagram showing the reflection pattern of the reflect array when θix=−70° and θrx=0°. FIG. 20 is a diagram showing the analysis results of the reflect array obtained in Comparative Example 4, and is a diagram showing the reflection pattern of the reflect array when θix=0° and θrx=−70°. 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. 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. FIG. 23 is a diagram showing the analysis results of the reflect array obtained in Example 5, and is a diagram showing the reflection pattern of the reflect array when θix=−70° and θrx=0°. FIG. 24 is a diagram showing the analysis results of the reflect array obtained in Comparative Example 5, and is a diagram showing the reflection pattern of the reflect array when θix=0° and θrx=−70°. 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. FIG. 26 is a diagram showing the analysis results of the reflect array obtained in Example 6, and is a diagram showing the reflection pattern of the reflect array when θix=−45° and θrx=0°. FIG. 27 is a diagram showing the analysis results of the reflect array obtained in Comparative Example 6, and is a diagram showing the reflection pattern of the reflect array when θix=0° and θrx=−45°. 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. FIG. 29 is a diagram showing the analysis results of the reflect array obtained in Example 7, and is a diagram showing the reflection pattern of the reflect array when θix=−70° and θrx=0°. FIG. 30 is a diagram showing the analysis results of the reflect array obtained in Comparative Example 7, and is a diagram showing the reflection pattern of the reflect array when θix=0° and θrx=−70°. 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. FIG. 32 is a diagram showing the analysis results of the reflect array obtained in Example 8, and is a diagram showing the reflection pattern of the reflect array when θix=70° and θrx=−30°. FIG. 33 is a diagram showing the analysis results of the reflect array obtained in Comparative Example 8, and is a diagram showing the reflection pattern of the reflect array when θix=−30° and θrx=70°. 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.

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.

(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. The terms related to the configuration of the reflectarray of the present disclosure will be described with reference to the drawings.
In this disclosure, a "reflector array (electromagnetic wave reflector)" is a member 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 reflector array 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.

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 combined. 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 lined up is defined as L, and the size of a side (short side) of a reflection control area in which only one unit cell is lined up is defined as M.

In addition, a "unit cell" refers to an area divided from the reflection control area. A unit cell contains one element pattern (element). Two or more unit cells exist within one reflection control area.

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.

2 is a diagram showing an incident angle and a reflection angle when a reflect array is arranged on an xy plane. Terms related to the definition of angles in this disclosure will be described 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.

特に設計した時の入射角度と反射角度を特定して示す場合には、設計の入射角度及び反射角度及び反射制御領域の関係を示す「式（１）を満たす」入射角度または反射角度と表現をする。
「入射ずれ角度」とは、式（１）を満たす入射角度を基準（＝０°）として、そこからの入射角度のずれが生じた時のずれの角度を示す。「入射ずれ角度」における角度表現は式（１）を満たす入射角度を基準（＝０°）として、＋ｚ軸方向に向かう方向を正の角度（０°から－１８０°）、－ｚ軸方向に向かう方向を負の角度（０°から－１８０°）として表す。
また、「入射許容角度範囲」Δθiとは、反射制御領域が式（１）を満たす入射角度から入射した電磁波を式（１）を満たす反射角度に反射させる電磁波の反射強度を基準（＝０ｄＢ）として、反射制御領域が入射ずれ角度から入射した電磁波を反射角度に反射させる電磁波の反射強度が、－３ｄＢ以内である入射ずれ角度の角度幅を表す。本開示における「入射許容角度範囲」は反射制御領域を８個用意して、１辺の長さが８Ｌとなるように並べたリフレクトアレイの性能と定義する。しかし、本請求の範囲のリフレクトアレイが「反射制御領域を８個用意して、１辺の長さが８Ｌとなるように並べたリフレクトアレイ」に限定されるものではない。 In the present 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).

In particular, when the designed incident angle and reflection angle are specifically indicated, they are expressed as an incident angle or reflection angle that "satisfies formula (1)" which indicates the relationship between the designed incident angle, reflection angle, and reflection control area.
The "incident deviation angle" refers to the angle of deviation when the incident angle deviates from the reference angle (=0°) that satisfies formula (1). The angle expression for the "incident deviation angle" is expressed by taking the incident angle that satisfies formula (1) as the reference angle (=0°) and expressing the direction toward the +z axis direction as a positive angle (0° to -180°) and the direction toward the -z axis direction as a negative angle (0° to -180°).
In addition, the "allowable incident angle range" Δθi represents the angle width of the incident deviation angle within -3 dB, where the reflection intensity of the electromagnetic wave that the reflection control area reflects the electromagnetic wave that is incident from the incident angle that satisfies the formula (1) to the reflection angle that satisfies the formula (1) is taken as the reference (=0 dB). The "allowable incident angle range" in the present disclosure is defined as the performance of a reflectarray in which eight reflection control areas are prepared and arranged so that the length of one side is 8L. However, the reflectarray in the present claims is not limited to "a reflectarray in which eight reflection control areas are prepared and arranged so that the length of one side is 8L".

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 a device that emits electromagnetic waves or a device that reflects electromagnetic waves from a device that emits electromagnetic waves. 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.

[First embodiment]
(Reflectarray configuration)
The configuration of the reflectarray and the configuration of the element pattern will be described with reference to Figures 1 and 3. Figure 3 is a diagram showing an example of the layer configuration of the reflectarray 6. The reflectarray 6 in Figure 3 has a plurality of element patterns periodically arranged 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 plane) 3. In the following description, an xyz coordinate system is applied, and the reflectarray 6 is arranged on the xy plane.

The reflect array 6 in FIG. 1b generates a predetermined asymmetric reflection of electromagnetic waves along the x-axis. The reflect array 6 has at least one or more reflection control regions 5. The reflection control region 5 includes unit cells 4 ₁ , 4 ₂ , 4 ₃ , ... 4 _n (hereinafter, when the unit cells are not specified, they are also referred to as "unit cells 4". n is a positive integer of 2 or more). The unit cells 4 are parts obtained by dividing the reflection control region 5 at equal intervals along the x-axis direction. n is the number of divisions when the reflection control region is divided into unit cells in the x-axis direction. The unit cell 4 is a square, and s = Lx/n = My, where s is the size (length) of the unit cell 4, Lx is the size (long side) of the reflection control region 5 in the x-axis direction, and My is the size (short side) of the reflection control region 5 in the y-axis direction.
The size of the reflect array 6 is determined by the size and number of the reflection control areas 5. For example, in the case of a reflect array that performs asymmetric reflection in the x-axis direction, in which eight reflection control areas 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 areas arranged in the direction of asymmetric reflection. That is, in FIG. 1b, the reflection pattern changes depending on the number of reflection control areas arranged in the x-axis direction, but the number of reflection control areas arranged in the y-axis direction does not affect the reflection pattern. The more the number of reflection control areas arranged in the x-axis direction, the thinner the reflection pattern of the reflect array becomes. The number of reflection control areas arranged in the y-axis direction affects the reflection intensity, and the more the number of reflection control areas 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 in the y-axis, or may include unit cells aligned in the x-axis and y-axis. The configuration of the reflection control region will be described later.

(Configuration of element pattern)
An element pattern is formed on the surface of the unit cell 4 facing the +z-axis direction. Using the division number n, the unit cells are expressed as unit cell ₄₁ , unit cell ₄₂ , ..., unit cell _4n . An element pattern ₁₁ is formed in the unit cell _41. An element pattern ₁₂ is formed in _the unit cell 42. An element pattern ₁₃ is formed in the unit cell 43. _An element pattern _1n is formed in the unit cell _4n .

In the reflection control area of FIG. 1, each element pattern has a shape slightly different from the other element patterns. Here, the shapes of the element patterns shown in element patterns 1 ₁ to 1 _n are sometimes called cross patches. A cross patch refers to a shape in which two square patches are orthogonal to each other in the xy plane. The element pattern 1 ₁ 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 orthogonal to each other with a common center of gravity. Similarly, the 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.

(Explanation of each configuration, design method)
(Layer configuration)
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, the three-layer structure of the element pattern 1, the dielectric layer 2, and the ground layer 3 is referred to as the "basic structure". In practice, it is preferable that the reflectarray 6 has a single or multiple layers having various functionalities (hereinafter also referred to as "functional layers") stacked on the element pattern 1 side or the ground layer 3 side of the basic structure, or on both sides. In the following description, layers included in the reflectarray other than the element pattern 1, the dielectric layer 2, and the ground layer 3 may be referred to as "functional layers" when the type of layer is not specified.

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 purposes other than improving the adhesion may also be formed. Note that intermediate products generated during the manufacturing process of the reflect array 6 may be formed in layers and remain on the reflect array 6.

Examples of functional layers include a design layer that is designed to blend in with the scenery of the area where the reflectarray 6 is installed, an installation layer that allows the reflectarray 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 the various layers.

(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 collecting 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".

The size Lx of the reflection control area in the x-axis direction is determined, for example, by 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,

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,

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.

(Relationship between unit cell and reflection phase)
The relationship between the unit cell and the reflection phase will be described with reference to Figs. 4 and 5. Figs. 4 and 5 are diagrams showing an example of the arrangement of 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 indicates the traveling direction of the wave front, the arrow toward the reflect array 6 indicates the traveling direction of the wave front of the incident wave, and the arrow away from the reflect array 6f indicates the traveling direction of the wave front of the reflected wave. 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.

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

When it is desired to make the reflect array 6f 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 area 5a (FIG. 4(b)). The reflection control area 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 area 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 area 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.

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.

(Distribution of reflection phase in 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.

Also, instead of the reflection phase, the distribution of the surface impedance can be applied to the reflection control area. In this case, the distribution of the surface impedance is expressed by, for example, formula (7) and formula (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 reflection control area, and any coordinates within the reflection control area can have a reference x = 0. Similarly, y1 and y2 indicate y coordinates as relative coordinates within the reflection control area, and any coordinates within the reflection control area can have a reference y = 0.
Furthermore, _k1 is the wave number of the reflected wave. j indicates an imaginary unit. When the reflection control area is to perform asymmetric reflection along the x-axis direction, it is preferable that the formula (7) is satisfied, and when the reflection control area is to perform asymmetric reflection along the y-axis direction, it is preferable that the formula (8) is satisfied.

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

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 selected as appropriate.

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

(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 accompanying 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 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 within the unit cell. Since the element patterns are evenly arranged 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) Note that, 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 to reduce the RCS at angles other than the target angle.

(Design method 2)
Design method 2 is a design method in which 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 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) It is also possible to further fine-tune the element length lx using an optimization method based on the analysis results of step 7 so as to further increase the RCS at the target reflection angle and to reduce the RCS at angles other than the target angle.

(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 the element length. This design method is effective when design methods 1 and 2 cannot ensure 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 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) Note that, 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.

(Element Pattern)
The element pattern will be described in detail with reference to Fig. 1, Fig. 6, and Fig. 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.
In general, reflectarrays change the reflection characteristics by utilizing the resonance of the element pattern. Here, since a linear or rectangular element pattern (square patch) mainly resonates the polarized wave in the direction along its long axis, it is known that when an element pattern with a shape perpendicular to these is used, it can handle both TE and TM polarized waves.

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, as n and m are increased, the reflection characteristics can be controlled for each smaller area, and the reflection characteristics of the reflectarray approach the theoretical characteristics.

The element pattern in the reflect array of the present disclosure includes a cross patch in the xy plane, in which two square patches are perpendicular to each other. Here, as shown in FIG. 1b, the square patch having a long side in the x-axis direction that constitutes the cross patch has an element length lx, which is the size of the long side, and an element width wy, which is the size of the short side, and the 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 unit cell 4n can be expressed as having element lengths lxn and lyn, and element widths wxn and wyn.

Figure 6 shows the configuration of an element pattern. One element pattern is placed in a unit cell. The cross patch that constitutes the element pattern of 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 Figure 6(a)), or may be different (unit cell 4b in Figure 6(b) and unit cell 4c in Figure 6(c)). These cross patch deformations can be selected as appropriate, which can increase the flexibility and scalability of the design.

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 element width wy in the same element pattern may be equal or different values. When they are different values, the characteristics for TE and TM polarization can be controlled separately.

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

The element pattern preferably has a surface resistance of 100 Ω/□ 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, or Ni. Nanoparticles or nanowires containing at least one of these materials may also be used. Examples of conductive organic materials include polythiophene derivatives, polyacetylene derivatives, polyaniline derivatives, polypyrrole derivatives, carbon nanotubes, and graphene. In particular, Cu and Al are preferred from the viewpoints of material cost, conductivity, and film formation. In addition, a transparent reflect array can be produced by using ITO or a mixture of polyethylenedioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT/PSS). The thickness of the element pattern is, for example, 10 nm to 18 μm. From the viewpoints of flexibility, film-forming properties, stability, sheet resistance, and low cost, it is preferable to use a film formed by vapor deposition as the element pattern.

The material of the element pattern may be the same as that of the ground layer described below, or a different material may be used. For example, at least one of the layers of the ground layer or the element pattern may be formed from Cu or Al. Cu has excellent conductivity and can reduce conductor loss. Al has low density, is lightweight, and is low cost, making it possible to form a lightweight and inexpensive reflect array. The thickness of at least one of the layers may be 1 μm or less. By making the thickness 1 μm or less, flexibility is improved, making it easier to install the reflect array on curved surfaces, and making it possible to achieve a lightweight structure.

The above materials can be used in a continuous film, mesh, or punched shape.

Here, mesh refers to a state in which a conductor has a mesh-like opening (hole) 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 be square. Square meshes provide good design. They may also be randomly shaped by a self-organizing method. Making the mesh random can prevent moire. When processing metal into a mesh shape, methods such as punching a metal plate or etching a metal plate can be used.

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

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

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

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

When the element pattern is formed using a thin film, the thickness is preferably greater than twice the skin depth calculated from formula (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 formula (11), a 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 formula (11). In an element pattern having a thickness sufficiently greater than twice the skin depth calculated from formula (11), the current is concentrated on the surface of the conductor due to the skin effect, and almost no current flows in the center. Therefore, even if the thickness is greater than twice the skin depth of formula (11), the power transmission characteristics do not change significantly. The closer the value is to twice the skin depth calculated from formula (11), the more sufficient the power transmission characteristics can be provided and the lower the material costs can be produced.

In addition, in order to increase the reflection efficiency of electromagnetic waves, it is also possible to reduce losses due to the element pattern. For this reason, 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, and the current density on the conductor surface becomes high. For this reason, it is easily affected by 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.

(Dielectric Layer)
For the dielectric layer, in addition to a simple resin, a composite material in which paper, glass fiber, carbon fiber, etc. are impregnated with resin can be used.

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. If the relative dielectric constant is within the above range, it tends to be easier to obtain the desired reflection phase characteristics in the reflect array 1. In addition, the dielectric tangent is preferably in the range of 0.00005 to 0.01, and more preferably in the range of 0.00005 to 0.001. If it is within the above range, a reflect array 1 with low dielectric loss can be produced.

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 to 5.0), polyimide (εr = 2.4 to 2.7), fluororesin (εr = 2.0 to 2.6), polycarbonate (εr = 2.9 to 8.9), polyphenylene ether (εr = 2.8 to 8.2), polyphenylene sulfide (εr = 3.2 to 4.6), polyvinylidene fluoride (εr = 6.4 to 10.0), polyethylene naphthalate (εr = 2.9), phenolic resin (εr = 3.0 to 12.0), cycloolefin polymer (εr = 2.3 to 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.

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

From the viewpoint of adjusting the dielectric constant, a mixture containing resin components or a dielectric compound and a resin component can be used. The relative dielectric constant of the mixture can be adjusted depending on the selection of the dielectric compound and its content.

The dielectric constant of a mixture can be predicted, for example, by using the Maxwell-Garnett law. In a mixture of a dielectric A having a dielectric constant εa and a dielectric B having 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).

Examples of dielectric compounds include barium titanate (εr = 250 to 20,000), titanium oxide (εr = 83 to 183), lead zirconate titanate, strontium tantalate bismuthate, and bismuth ferrite.

When a transparent dielectric is used, the reflectarray exhibits visible light transparency, allowing the appearance to be maintained after installation.

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 easier to design the reflect array if the thickness of the dielectric layer is several μm or more and 100 μm or less.

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

(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.

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, and graphene. In particular, Cu and Al are preferred from the viewpoints of material cost, electrical conductivity, and film-forming properties. In addition, 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).

The above materials can be used in a continuous film, mesh, punched shape, or periodic structure.

Here, mesh refers to a state in which a conductor has a mesh-like opening (hole) 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 be square. Square meshes provide good design. They may also be randomly shaped by a self-organizing method. Making the mesh random can prevent moire. When processing metal into a mesh shape, methods such as punching a metal plate or etching a metal plate can be used.

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

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

When a metal material is used as a method for forming the ground layer, it is possible to select 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 may be used as the ground layer. When an inorganic oxide material is used, dry coating may be selected as a method for forming the ground layer 11. When an organic material is used, wet coating may be selected as a method for forming the ground layer 11. It may also be formed by painting or spraying.

When the ground layer is in the form of a thin film formed by plating or vapor deposition, it is possible to improve the flexibility of the reflect array, making it possible to use it on curved surfaces and to implement a roll-to-roll production process.

If the ground layer is in the form of a thin film, its thickness is preferably greater than the skin depth calculated from equation (11), similar to the element pattern.

In addition, in order to increase the reflection efficiency of electromagnetic waves, it is necessary to reduce losses due to the ground layer. For this reason, it is preferable for the surface roughness of the ground layer to be small.

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

(Production 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, for example, a copper foil laminated onto an insulator, such as a glass cloth base material 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.

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 adhesion with the functional layer when it is laminated, as described below.

Generally, the dimensional error of the element pattern when cutting is about ±100 μm, and when etching is about ±50 μm.

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

Laying other layers (functional layers such as protective layers, adhesive layers, design layers, installation layers, etc.) onto the basic structure can be done by laminating, printing/coating, or extrusion molding. Lamination can be done by, for example, dry lamination, wet lamination, thermal lamination, or extrusion lamination, but is not limited to these.

リフレクトアレイにおける入射角度は、－７０°以上－４５°以下または＋４５°以上＋７０°以下であることが好ましい。｜θｉ｜が大きいほど、リフレクトアレイは入射許容角度範囲が広くなり、この角度範囲から入射した電磁波を反射角度方向に反射させることができる。 (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).

The incident angle in the reflect array is preferably −70° to −45° or +45° to +70°. The larger |θi| is, the wider the incident angle range of the reflect array becomes, and electromagnetic waves incident from this angle range can be reflected in the reflection angle direction.

この範囲においてリフレクトアレイは広い範囲の角度から入射した電磁波を反射角度方向に反射させることができる。より好ましくは、反射角度θｒが－３０°以上＋３０°以下であることが好ましく、さらに好ましくは－２０°以上＋２０°以下であることが好ましい。反射角度が０°に近いほど広い範囲の角度から入射した電磁波を反射角度方向に反射させることができ、広い入射許容角度範囲を確保できる。 The reflection angle in the reflectarray needs to satisfy formula (2).

In this range, the reflect array can reflect electromagnetic waves incident from a wide range of angles in the reflection angle direction. More preferably, the reflection angle θr is -30° or more and +30° or less, and even more preferably, -20° or more and +20° or less. The closer the reflection angle is to 0°, the wider the range of angles that the electromagnetic waves incident from can be reflected in the reflection angle direction, ensuring a wide range of allowable incident angles.

(Acceptable incident angle range)
The incidence deviation angle indicates the incidence angle at which a deviation occurs from the incidence angle (=0°) that satisfies the formula (1). The incidence deviation angle is expressed as an angle in which the incidence angle that satisfies the formula (1) is the reference (=0°), and the direction toward the +z axis direction is expressed as a positive angle (0° to −180°), and the direction toward the −z axis direction is expressed as a negative angle (0° to −180°).
The allowable incidence angle range indicates the angle width of the incidence deviation angle within which the reflection intensity of the electromagnetic wave that the reflection control area reflects, to a reflection angle that satisfies the formula (1), the electromagnetic wave that is incident from the incidence deviation angle to which the reflection control area reflects the electromagnetic wave to a reflection angle that satisfies the formula (1) is within -3 dB, with the reflection intensity of the electromagnetic wave being taken as the reference (=0 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 |θi| of the incident angle increases. Also, in the range where the absolute value |θi| of the incident angle 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 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 less than 16°. When the allowable incident angle range is less than 5.5°, it is necessary to accurately grasp the direction of the electromagnetic wave emitted from the transmitter. Also, when an antenna with beamforming is used for the transmitter, it is necessary to arrange more antenna elements in order to increase the angular accuracy of the beamforming, which leads to a larger area and higher cost of the transmitter. Also, when the allowable incident angle range is 16° or more, radio wave sources other than the transmitter are reflected, which may cause phase disturbance.

(Electromagnetic Wave Reflection System)
An example of an installation method of an electromagnetic wave reflection system and 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 Fig. 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 reflect array of the present disclosure, within the range of incident angles and reflection angles that satisfy formula (2), electromagnetic waves incident on the reflect array 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.

(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 6 ₁ , and the reflectarray installed on the wall 201 is 6 ₂ . The reflectarray 6 ₁ is an installation method that satisfies the formula (2), and the reflectarray 6 ₂ is an installation method that does not satisfy the formula (2). The installation method of the reflectarray 6 ₂ requires high accuracy to determine the positional relationship between the transmitter and the reflectarray 6 ₂ , and if there is a deviation in the installation position, the power that the receiver can receive changes significantly. By installing the reflectarray 6 ₁ 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.

(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 provide 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.

(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.

(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.

(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.

When the reflectarray is intended for indoor use, it is preferable to use a protective layer that has antibacterial, antiviral, and contamination resistance properties. Furthermore, when the reflectarray is intended for outdoor use, weather resistance is required, so a layer containing UVA (ultraviolet absorber) and HALS (light stabilizer) may be used.

[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 cases where the same reflectarray satisfies and does not satisfy Equation (2) 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 of installation error of the reflectarray. When the distance between the transmitter and the reflectarray is 5 m, if the reduction in received power is within -3 dB even if the reflectarray is moved 45 cm, it is marked as ◯, and if the reduction in received power is greater than -3 dB, it is marked as ×. When the reflector has an asymmetric reflection in the x-axis direction, the direction in which the reflectarray is moved is parallel to the x-axis.
The reception stability is an index showing the stability of the received power at the reflection angle that satisfies the 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, it is judged as an X, which means that the received power is unstable, and if it is greater than 5.5° and less than 16°, it is judged as an O, which means that the received power is stable.

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

The operating frequency was set to 28 GHz, the target reflection characteristics (target reflection characteristics) were set to θix = -45°, θrx = 0°, 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).

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.

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 when the element width w or element length l was 1.400 mm, the reflection phase changed as the element width w or element length l changed.

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 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.

Reflectarray 6 has 8 x 6 reflection control areas arranged in the x-axis and y-axis directions, with a size of 121.12 mm x 90.840 mm in the xy plane. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto reflectarray 6 at θix = -45° and θrx = 0°.

To understand the acceptable range of incident angles, a similar analysis was performed when the angle was changed in 2° increments in the range -65°≦θix≦-25°.

Figure 10 shows the analysis results of the reflectarray 6 obtained in Example 1. In Figure 10, the horizontal axis is the reflection angle θrx, and the vertical axis is the RCS (radar cross section). RCS is a value that essentially 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.

(Comparative Example 1)
A reflectarray similar to the reflectarray described in Example 1 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.

To understand the acceptable range of incident angles, a similar analysis was performed when the angle was changed in 2° intervals in the range of -20°≦θix≦20°.

Figure 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.

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 shows the incidence deviation angle, and the vertical axis shows the amount of change in RCS when the RCS when the incidence deviation angle = 0° is set to 0 dB.
Specifically, in the first embodiment, when the incident deviation angle is 0°, θix=-45°, and the angle when the incident deviation angle 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 set to 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 the incident deviation angle 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 set to 0 dB. The dotted line at -3 dB indicates the range of allowable incident angles.

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

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

The operating frequency was set to 28 GHz, the target reflection characteristics (target reflection characteristics) were set to θix = -50°, θrx = 0°, 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).

The number of divisions in the reflection control region 5 was set to 3, and the size of the unit cell in the x-axis and y-axis directions was set to 4.659 mm. The shape of the element pattern was a cross patch in which two square patches crossed at right angles in the xy plane. Here, the element lengths and element widths were different in each element pattern in the reflection control region 5, and the element lengths and element widths in the x-axis and y-axis directions 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.

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.

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 equation (9). The element lengths l were set to lx1 = ly1 = 3.790 mm, lx2 = ly2 = 2.775 mm, and lx3 = ly3 = 2.065 mm, and the element widths were set to wx1 = wy1 = 2.303 mm, wx2 = wy2 = 2.217 mm, and wx3 = wy3 = 2.024 mm, respectively.

Reflectarray 6 has reflection control areas arranged in the x-axis and y-axis directions in a matrix of 8 x 6, with a size of 111.816 mm x 27.954 mm in the xy plane. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto reflectarray 6 at θix = -50° and θrx = 0°.

To understand the acceptable range of incident angles, a similar analysis was performed when the angle was changed in 2° intervals in the range -70°≦θix≦-30°.

Figure 13 shows the analysis results of the reflectarray 6 obtained in Example 2. In Figure 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.

(Comparative Example 2)
A reflectarray similar to the reflectarray described in Example 2 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=−50°, respectively. The reflection characteristics of the reflectarray 6 were analyzed using HFSS.

To understand the acceptable range of incident angles, a similar analysis was performed when the angle was changed in 2° intervals in the range of -20°≦θix≦20°.

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

Figure 15 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 Example 2 and Comparative Example 2.

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

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

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

The number of divisions in the reflection control region 5 was set to 3, and the size of the unit cell in the x-axis and y-axis directions was set to 4.121 mm. The shape of the element pattern was a cross patch in which two square patches crossed at right angles in the xy plane. Here, the element lengths and element widths were different in each element pattern in the reflection control region 5, and the element lengths and element widths in the x-axis and y-axis directions 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.

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.

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 equation (9). The element lengths l were lx1 = ly1 = 2.051 mm, lx2 = ly2 = 3.614 mm, and lx3 = ly3 = 2.815 mm, and the element widths were wx1 = wy1 = 1.427 mm, wx2 = wy2 = 1.521 mm, and wx3 = wy3 = 1.699 mm, respectively.

Reflectarray 6 has 8 x 6 reflection control areas arranged in the x-axis and y-axis directions, with a size of 98.904 mm x 24.726 mm in the xy plane. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto reflectarray 6 at θix = -60° and θrx = 0°.

To understand the acceptable range of incident angles, a similar analysis was performed when the angle was changed in 2° increments in the range -80°≦θix≦-40°.

Figure 16 shows the analysis results of the reflectarray 6 obtained in Example 3. In Figure 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.

(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.

To understand the acceptable range of incident angles, a similar analysis was performed when the angle was changed in 2° intervals in the range of -20°≦θix≦20°.

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

Figure 17 shows the comparison results of the amount of change in power that can be received at a specific reflection angle θrx when the angle of incidence is changed in Example 3 and Comparative Example 3.

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

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

The operating frequency was set to 28 GHz, the target reflection characteristics (target reflection characteristics) were set to θix = -70°, θrx = 0°, 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).

The number of divisions in the reflection control region 5 was set to 3, and the size of the unit cell in the x-axis and y-axis directions was set to 3.798 mm. The shape of the element pattern was a cross patch in which two square patches crossed at right angles in the xy plane. Here, the element lengths and element widths were different in each element pattern in the reflection control region 5, and the element lengths and element widths in the x-axis and y-axis directions 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.

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.

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 equation (9). The element lengths l were lx1 = ly1 = 2.353 mm, lx2 = ly2 = 3.308 mm, and lx3 = ly3 = 2.786 mm, and the element widths were wx1 = wy1 = 1.500 mm, wx2 = wy2 = 1.500 mm, and wx3 = wy3 = 1.500 mm, respectively.

Reflectarray 6 has reflection control areas arranged in the x-axis and y-axis directions in a matrix of 8 x 6, with a size of 91.152 mm x 22.788 mm in the xy plane. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto reflectarray 6 at θix = -70° and θrx = 0°.

To understand the acceptable range of incident angles, a similar analysis was performed when the angle was changed in 2° intervals in the range -90°≦θix≦-50°.

Figure 19 shows the analysis results of the reflectarray 6 obtained in Example 4. In Figure 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.

(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.

To understand the acceptable range of incident angles, a similar analysis was performed when the angle was changed in 2° intervals in the range of -20°≦θix≦20°.

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

Figure 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 Example 4 and Comparative Example 4.

From the results in Figure 21, the allowable incident angle range was 15.3° in Example 4 and 5.5° in Comparative Example 4. As a result of checking the ease of installation, in Example 4, even when the reflect array was moved 45 cm, the change in received power was within -3 dB in the direction of the receiving angle that satisfied formula (1), whereas in Comparative Example 4, the change was greater than -3 dB. Furthermore, as a result of checking the reception stability, in Example 4, the received power was stable in a range of allowable incident angles greater than 5.5°, whereas in Comparative Example 4, the received power was unstable in a range of allowable incident angles of 5.5° or less.

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

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

The operating frequency was set to 4.85 GHz, the target reflection characteristics (target reflection characteristics) were set to θix = -70°, θrx = 0°, 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).

The number of divisions in the reflection control region 5 was set to 4, and the size of the unit cell in the x-axis and y-axis directions was set to 16.445 mm. The shape of the element pattern was a cross patch in which two square patches crossed at right angles in the xy plane. Here, the element lengths and element widths were different in each element pattern in the reflection control region 5, and the element lengths and element widths in the x-axis and y-axis directions 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.

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.

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 = 14.000 mm, lx2 = ly2 = 14.000 mm, lx3 = ly3 = 14.000 mm, and lx4 = ly4 = 14.000 mm, and the element widths were wx1 = wy1 = 8.303 mm, wx2 = wy2 = 5.887 mm, wx3 = wy3 = 11.538 mm, and wx4 = wy4 = 9.400 mm, respectively.

Reflectarray 6 has reflection control areas arranged in the x-axis and y-axis directions in a matrix of 8 x 6, with a size of 206.240 mm x 38.670 mm in the xy plane. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto reflectarray 6 at θix = -70° and θrx = 0°.

To understand the acceptable range of incident angles, a similar analysis was performed when the angle was changed in 2° intervals in the range -90°≦θix≦-50°.

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

(Comparative Example 5)
A reflectarray similar to the reflectarray described in Example 5 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.

To understand the acceptable range of incident angles, a similar analysis was performed when the angle was changed in 2° intervals in the range of -20°≦θix≦20°.

Figure 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.

Figure 25 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 for each of Example 5 and Comparative Example 5.

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

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

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

The number of divisions in the reflection control region 5 was set to 3, and the size of the unit cell in the x-axis and y-axis directions was set to 2.355 mm. The shape of the element pattern was a cross patch in which two square patches crossed at right angles in the xy plane. Here, the element lengths and element widths were different in each element pattern in the reflection control region 5, and the element lengths and element widths in the x-axis and y-axis directions 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.

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.

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 equation (9). The element lengths l were lx1 = ly1 = 1.700 mm, lx2 = ly2 = 1.700 mm, lx3 = ly3 = 1.700 mm, and lx4 = ly4 = 14.000 mm, and the element widths were wx1 = wy1 = 1.362 mm, wx2 = wy2 = 1.741 mm, and wx3 = wy3 = 1.538 mm, respectively.

Reflectarray 6 has 8 x 6 reflection control areas arranged in the x-axis and y-axis directions, with a size of 62.184 mm x 15.546 mm in the xy plane. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto reflectarray 6 at θix = -45° and θrx = 0°.

To understand the acceptable range of incident angles, a similar analysis was performed when the angle was changed in 2° increments in the range -65°≦θix≦-25°.

Figure 26 shows the analysis results of the reflectarray 6 obtained in Example 6. In Figure 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.

(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.

To understand the acceptable range of incident angles, a similar analysis was performed when the angle was changed in 2° intervals in the range of -20°≦θix≦20°.

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

Figure 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 for Example 6 and Comparative Example 6.

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

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

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

The number of divisions in the reflection control region 5 was set to 3, and the size of the unit cell in the x-axis and y-axis directions was set to 1.772 mm. The shape of the element pattern was a cross patch in which two square patches crossed at right angles in the xy plane. Here, the element lengths and element widths were different in each element pattern in the reflection control region 5, and the element lengths and element widths in the x-axis and y-axis directions 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.

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.

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 equation (9). The element lengths l were set to lx1 = ly1 = 1.310 mm, lx2 = ly2 = 1.570 mm, and lx3 = ly3 = 1.459 mm, and the element widths were set to wx1 = wy1 = 1.100 mm, wx2 = wy2 = 1.100 mm, and wx3 = wy3 = 1.100 mm.

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

To understand the acceptable range of incident angles, a similar analysis was performed when the angle was changed in 2° intervals in the range -90°≦θix≦-50°.

Figure 29 shows the analysis results of the reflectarray 6 obtained in Example 7. In Figure 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° was reflected in the desired direction of θrx = 0°, and the RCS was -8.84 dBsm.

(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.

To understand the acceptable range of incident angles, a similar analysis was performed when the angle was changed in 2° intervals in the range of -20°≦θix≦20°.

Figure 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.

Figure 31 shows the comparison results of the amount of change in power that can be received at a specific reflection angle θrx when the angle of incidence is changed for Example 7 and Comparative Example 7.

From the results in Figure 31, the allowable incident angle range was 15.1° for Example 7 and 5.4° for Comparative Example 7. As a result of checking the ease of installation, in Example 7, even when the reflect array was moved 45 cm, the change in received power was within -3 dB in the direction of the receiving angle that satisfied formula (1), whereas in Comparative Example 7, the change was greater than -3 dB. Furthermore, as a result of checking the reception stability, in Example 7, the received power was stable in a range of allowable incident angles greater than 5.5°, whereas in Comparative Example 7, the received power was unstable in a range of allowable incident angles of 5.5° or less.

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 was no significant difference in the allowable incident angle range depending on the frequency.

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

The operating frequency was set to 28 GHz, the target reflection characteristics (target 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).

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 and y-axis directions was set to 4.058 mm. The shape of the element pattern was a cross patch in which two square patches crossed at right angles 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 and y-axis directions 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.

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.

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 = 2.897 mm, lx2 = ly2 = 3.079 mm, lx3 = ly3 = 3.621 mm, lx4 = ly4 = 1.885 mm, lx5 = ly5 = 2.530 mm, and lx6 = ly6 = 2.743 mm, and the element widths were wx1 = wy1 = 1.500 mm, wx2 = wy2 = 1.500 mm, wx3 = wy3 = 1.500 mm, wx1 = wy1 = 1.500 mm, wx2 = wy2 = 1.500 mm, and wx3 = wy3 = 1.500 mm.

Reflectarray 6 has reflection control areas arranged in the x-axis and y-axis directions in a matrix of 8 x 6, with a size of 194.784 mm x 146.008 mm in the xy plane. HFSS was used to analyze the reflection characteristics when polarized waves parallel to the y-axis were irradiated onto reflectarray 6 at θix = 70° and θrx = -30°.

To grasp the acceptable range of incident angles, a similar analysis was performed when the angle was changed in 2° intervals in the range 50°≦θix≦90°.

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

(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.

To understand the acceptable range of incident angles, a similar analysis was performed when the angle was changed in 2° intervals in the range of -20°≦θix≦20°.

Figure 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.

Figure 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 for Example 8 and Comparative Example 8.

From the results in Figure 34, the allowable incident angle range was 8.3° in Example 8 and 2.5° in Comparative Example 8. As a result of checking the ease of installation, in Example 8, even when the reflect array was moved 45 cm, the change in received power was within -3 dB in the direction of the receiving angle that satisfied formula (1), whereas in Comparative Example 8, the change was greater than -3 dB. Furthermore, as a result of checking the reception stability, in Example 8, the received power was stable in a range of allowable incident angles greater than 5.5°, whereas in Comparative Example 8, the received power was unstable in a range of allowable incident angles of 5.5° or less.

（態様２）
前記リフレクトアレイは誘電体層の片面に素子があり、誘電体層の素子とは反対側の面にグランド層を有している態様１に記載のリフレクトアレイ。
（態様３）
前記素子がクロスパッチ構造である態様２に記載のリフレクトアレイ。
（態様４）
前記リフレクトアレイは３ＧＨｚ～６０ＧＨｚの電磁波を反射させる態様１から３のいずれか一つに記載のリフレクトアレイ。
（態様５）
発信器から一次放射された電磁波が前記リフレクトアレイに当たり、前記リフレクトアレイから二次放射された電磁波を受信器に届ける電磁波反射システムであって、前記リフレクトアレイが態様１～４のいずれか一つに記載のリフレクトアレイである、電磁波反射システム。
（態様６）
電磁波を反射させるリフレクトアレイの設置方法であって、
前記リフレクトアレイは、位相を制御する反射制御領域を有し、
前記反射制御領域は、長辺の長さをＬ、反射する電磁波の波長をλ、入射角度をθｉ、反射角度をθｒとした時に、下記の式（１）を満たし、
前記入射角度θｉは４５°以上７０°以下の範囲であり、かつ前記入射角度θｉと前記反射角度θｒは下記の式（２）の関係を満たすように、前記リフレクトアレイを支持体に固定する、前記リフレクトアレイの設置方法。

（態様７）
態様６に記載の前記リフレクトアレイは、態様１から４のいずれか一つに記載のリフレクトアレイである、リフレクトアレイの設置方法。 [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 within the scope of the gist of the present invention. The following describes possible aspects of the present invention, but the present invention is not limited to these.
(Aspect 1)
A reflectarray that reflects electromagnetic waves, the reflectarray having a reflection control region that controls a phase, the reflection control region 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, and 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.

(Aspect 2)
2. The reflectarray according to claim 1, wherein the reflectarray has elements on one side of a dielectric layer and a ground layer on the side of the dielectric layer opposite the elements.
(Aspect 3)
The reflect array according to aspect 2, wherein the element has a cross patch structure.
(Aspect 4)
The reflectarray according to any one of aspects 1 to 3, wherein the reflectarray reflects electromagnetic waves of 3 GHz to 60 GHz.
(Aspect 5)
An electromagnetic wave reflection system in which an electromagnetic wave primarily radiated from a transmitter hits the reflectarray and an electromagnetic wave secondarily radiated from the reflectarray is delivered to a receiver, the reflectarray being the reflectarray according to any one of aspects 1 to 4. The electromagnetic wave reflection system.
(Aspect 6)
A method for installing a reflect array that reflects electromagnetic waves, 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:
The method for installing the reflectarray includes fixing the reflectarray to a support so 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).

(Aspect 7)
A method for installing a reflectarray, wherein the reflectarray according to aspect 6 is the reflectarray according to any one of aspects 1 to 4.

1, ₁ 1 -1 _n , 1d ₁ -1d ₃ , 1e ₁ -1e ₃ , 1a-1c, 1 ^x ₁ -1 ^x _n , 1 ^y
_1-1 ^y _n element pattern,
2 dielectric layer,
3. Ground layer,
4 _, 4 ₁ -4 _n , 4 a - 4 c, 4 ^x ₁ -4 ^x _n , 4 ^y ₁ -4 ^yn unit cells;
5 reflection control area,
6, 6 ₁ - 6 ₂ reflect array,
200, 201 Wall,
300 transmitter,
400 receiver,
500 Cover,
501 Building (shield),
600 Support 601 Support position adjustment jig

Claims (7)

A reflect array that reflects electromagnetic waves,
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:
The incident angle |θi| is in the range of 45° or more and 70° or less, and the incident angle θi and the reflection angle θr satisfy the relationship of the following formula (2), and an incident allowable angle range Δθi is in the range of more than 5.5° and 16° or less.

The reflectarray according to claim 1, wherein the reflectarray has elements on one side of a dielectric layer and a ground layer on the side of the dielectric layer opposite the elements. The reflect array according to claim 2, wherein the elements are cross patches. The reflectarray according to any one of claims 1 to 3, which reflects electromagnetic waves of 3 GHz to 60 GHz. An electromagnetic wave reflection system in which an electromagnetic wave radiated primarily from a transmitter is incident on the reflectarray and an electromagnetic wave radiated secondarily from the reflectarray is received by a receiver, the reflectarray being a reflectarray according to any one of claims 1 to 3. A method for installing a reflect array that reflects electromagnetic waves, 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 reflectarray, comprising fixing the reflectarray to a support so 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).

A method for installing a reflectarray, the reflectarray described in claim 6 being the reflectarray described in claim 1 or 2.

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