Reflectarray

Abstract

The purpose of the present invention is to provide a technology that makes stable communication and motion detection possible even when the incidence angle or reflection angle with respect to an incident or reflected beam of a reflectarray deviates from design. For this purpose, a reflectarray according to the present invention is characterized by having multiple types of reflection control regions in which a plane wave from a design incidence angle θi satisfying formula (1) is most strongly reflected at a design reflection angle θr satisfying formula (2), wherein, in downlink communication (radiation wave), the plane wave incident in an angular range of ±α degrees satisfying formula (3) around a design center incidence angle [θi0]d is reflected such that the average value of reflection intensity in an angular range of ±α degrees around a design center reflection angle [θr0]d is higher by 5 dB or more than the average value of reflection intensity in an angular range of -90 to 90 degrees excluding the angular range, and a variation coefficient C[θr]d of reflection intensity derived from formula (4) for an arbitrary reflection angle [θr]d within the angular range is 0.6 or less.

Description

Reflectarray

[0001] The present invention relates to a reflectarray.

[0002] The advancement of digitalization in society has dramatically increased data transmission speeds in wireless communications, resulting in increasingly higher frequencies of electromagnetic waves (hereinafter referred to as "radio waves"). However, as the frequency of electromagnetic waves increases, they tend to propagate more directional. This makes them less susceptible to blind spots, such as areas where communication is impossible, such as in the shadows of buildings. For these reasons, increasing the number of base stations is necessary to achieve widespread 5G and 6G communications. However, the high cost of installing additional base stations poses a challenge, making it difficult to rapidly increase the number of base stations. Furthermore, millimeter-wave radar (sensors) using high-frequency electromagnetic waves, capable of highly accurate distance measurement and motion detection, is utilized in a variety of fields, including mobility, robotics, security, and healthcare. For example, in mobility, millimeter-wave radar is used in automotive radars for advanced driver assistance systems and autonomous driving technology, accurately measuring the position, speed, and distance of other vehicles and pedestrians, enabling safe vehicle distance maintenance and obstacle avoidance. In healthcare, millimeter-wave sensors are used as non-contact sensors for monitoring and medical monitoring. They can detect human movement, falls, and subtle changes in heart rate and breathing, even in dark places and through obstacles. While improved performance is required for these applications, issues remain, such as beam directionality, obstacles, and reduced detection accuracy due to multipath interference. In recent years, reflectarrays have been proposed as a technology for controlling the direction of electromagnetic waves to address these issues with 5G and 6G communications and millimeter-wave radar. Reflectarrays (electromagnetic wave reflectors) are components that reflect electromagnetic waves. Reflectarrays are not limited to those that provide symmetrical reflection (with equal angles of incidence and reflection), but also include those that provide asymmetrical reflection (with angles of incidence and reflection different from each other), those that retroreflect electromagnetic waves in the direction of incidence, those that scatter electromagnetic waves in multiple directions, and those that focus electromagnetic waves at specific locations.

[0003] Patent Document 1 discloses a frequency-selective reflector (reflectarray) that reflects electromagnetic waves of a specific frequency band in a direction different from the regular reflection direction, and that can widen or narrow the reflected beam of a plane wave incident from a uniform incident direction by arranging a main region and multiple sub-regions with different reflection directions. Patent Document 2 also discloses a reflectarray that enables communication at multiple incident and reflection angles without reducing directional gain by arranging multiple supercells, each of which is composed of an array of first elements and second elements.

[0004] International Publication No. 2023 / 027195 Japanese Patent Application Laid-Open No. 2023-22427

[0005] However, while conventional reflectarrays function to reflect electromagnetic waves of a specific frequency band incident at a designed angle of incidence in a direction different from the specular reflection direction, they often do not function properly for incident waves at angles other than the designed angle of incidence. Furthermore, as the size of a reflectarray increases, the reflected beam becomes sharper and the irradiation area of ​​the reflected beam becomes narrower. Due to these characteristics of reflectarrays, in 5G and 6G communications, communication stability can be compromised if the angle of incidence or reflection of the reflectarray's incident or reflected beam deviates from the design, resulting in issues such as (a) a deviation in the installation position or installation angle of the reflectarray, (b) a deviation in the terminal position, or (c) an insufficient reception power of the terminal due to the temporary presence of an obstacle such as a person or object in the incident or reflected beam. Millimeter-wave radar (sensors) also suffer from the issue of impaired motion detection stability for similar reasons.

[0006] Patent Document 1 discloses a function for adjusting the reflected beam profile of a frequency-selective reflector to widen the beam width of a reflected wave for a plane wave incident at a predetermined design angle of incidence, but does not describe providing a similar function for plane waves incident at angles other than the design angle of incidence. Patent Document 1 also discloses a function for widening the reflected beam of a spherical wave for a spherical wave incident, but it sets the reflection direction vector of each divided region differently while correcting differences in the incident direction vector of the spherical incident wave, which is uniquely determined for each divided region, and does not describe the effects of incident waves from directions deviating from the unique incident direction vector. Patent Document 2 describes enabling communication using multiple incident and reflection angles, but does not recognize the issue of ensuring communication stability even when the incident angle or reflection angle of the incident or reflected beam deviates from the design. Therefore, an object of the present invention is to provide a technology that enables stable communication and motion detection even when the incident angle or reflection angle of the incident or reflected beam of a reflectarray deviates from the design.

[0007] In order to solve the above problems, one representative reflectarray of the present invention has a plurality of types of reflection control regions that most strongly reflect a plane wave from an arbitrary design incident angle θi that satisfies formula (1) to an arbitrary design reflection angle θr that satisfies formula (2) for an electromagnetic wave in a specific frequency band, In downstream communication (or radiation wave), the design central incident angle [θi ０ ]d. The plane wave incident within the angle range of ±α degrees (hereinafter referred to as the "downward incident angle range ±α") that satisfies the formula (3) is reflected at the design central reflection angle [θr ０ ]d (hereinafter referred to as "downward reflection angle range ±α"), the average value of the reflection intensity (bistatic RCS) in the angle range of ±α degrees centered on the downward reflection angle range ±α is 5 dB or more higher than the average value of the reflection intensity in the angle range of -90 degrees to 90 degrees excluding the downward reflection angle range ±α, and when the reflection intensity of the plane wave from the incident angle [θi]d to the reflection angle [θr]d is σ[θi]d[θr]d, the coefficient of variation C of the reflection intensity derived from equation (4) for any reflection angle [θr]d within the downward reflection angle range ±α is [θｒ]ｄis 0.6 or less.

[0008] According to the present invention, stable communication and moving object detection are possible even when the incident angle or reflection angle of the incident or reflected beam of the reflectarray deviates from the design. Problems, configurations, and effects other than those described above will become clear from the description of the following embodiments.

[0009] FIG. 1 is a cross-sectional view showing an example of the layer structure of a reflectarray. FIG. 2 is a diagram showing an example of an element pattern shape. FIG. 3 is an example of a schematic diagram showing an enlarged view of a reflection control region portion. FIG. 4 is a schematic diagram explaining characteristic 1 of a single reflectarray. FIG. 5 is a schematic diagram explaining characteristic 2 of a single reflectarray. FIG. 6 is a schematic diagram explaining characteristic 3 of a single reflectarray. FIG. 7 is a schematic diagram showing an example of a failure in radio wave relay using a single reflectarray. FIG. 8 is a schematic diagram explaining functions realized by a reflectarray according to this embodiment. FIG. 9A is a schematic diagram showing an overall image of incident and reflection of downstream communication radio waves (or emitted waves) in the reflectarray of embodiment 1. FIG. 9B is a schematic diagram showing an overall image of incident and reflection of upstream communication radio waves (or received waves) in the reflectarray of embodiment 2. FIG. 10 is a schematic diagram showing the arrangement of reflection control regions (groups) in the reflectarray of example 1. Fig. 11 is a graph showing the reflection patterns (bistatic RCS) of the reflectarrays of Example 1 and Comparative Examples 1 and 2. Fig. 12 is a graph showing the reflection patterns (bistatic RCS) of the reflectarrays of Example 2 and Comparative Example 3.

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to this embodiment. In addition, in the description of the drawings, the same parts are designated by the same reference numerals.

[0011] In the following description, an xyz coordinate system is applied, and the reflectarray is formed on the xy plane. The positive direction of the z axis is sometimes referred to as upward, and the negative direction as downward. A view of the xy plane viewed from above the z axis (planar view) is called a plan view, and a view of a plane cut by a plane parallel to the z axis viewed from a perpendicular direction (cross-section) is called a cross-sectional view. The shape of the reflectarray in the xy plane is arbitrary, but in the following description, the reflectarray is assumed to be the simplest rectangle, and is formed so that each side of the reflectarray is parallel to the x and y axes, respectively.

[0012] In the following description, the term "surface" may refer not only to the surface of a plate-like member, but also to the interface of a layer contained in the plate-like member that is approximately parallel to the surface of the plate-like member. Furthermore, the terms "upper surface" and "lower surface" refer to the surface shown at the top or bottom of the drawing when the plate-like member or a layer contained in the plate-like member is illustrated.

[0013] In the following description, electromagnetic waves (radio waves) are assumed to be plane waves, but the term "plane waves" also includes electromagnetic waves whose wavefronts can be practically considered to be plane at far-field distances. In this disclosure, electromagnetic waves (radio waves) are sometimes simply referred to as "plane waves." Although theoretically, wavefronts extend infinitely, practically, wavefronts can be considered to be plane at far-field distances. This property is used in various fields of physics and engineering, and its application is also possible within the scope of this disclosure.

[0014] <Reflectarray Configuration> First, the configuration of the reflectarray will be described. Fig. 1 is a cross-sectional view showing an example of the layer configuration of a reflectarray. As shown in Fig. 1, the reflectarrays 4 and 40 have a configuration in which at least an element pattern 1, a dielectric layer 2, and a ground layer 3 are stacked in a direction from the +z-axis direction to the -z-axis direction. In the following description, the configuration consisting of the three layers of the element pattern 1, the dielectric layer 2, and the ground layer 3 will be referred to as the "basic configuration."

[0015] In practice, it is preferable to laminate one or more layers (additional functional layers 5) having various functions on the element pattern 1 side or the ground layer 3 side of the basic configuration of the reflectarray, or on both sides. The lamination method on the element pattern 1 side may be to completely fill the gaps between the elements, or to cover the top surfaces of the elements while leaving the gaps between the elements. Examples of the additional functional layer 5 include a design layer that takes the aesthetics into consideration, an installation layer that allows the electromagnetic wave reflector to be easily installed on a wall, ceiling, support, etc., a protective layer that protects the basic configuration, and a functional layer that imparts various functions. Furthermore, if necessary, an adhesion improving layer may be formed between the element pattern 1 and the dielectric layer 2, between the ground layer 3 and the dielectric layer 2, and between the dielectric layer 2 and the element pattern 1 and the additional functional layer 5 to improve adhesion. The adhesion improving layer is composed of an adhesive. The adhesive may be a water-dispersion adhesive, a solution-based adhesive, a solvent-free adhesive, or a solid-based adhesive. The aforementioned additional functional layer and adhesion improving layer may be collectively referred to as the functional layer.

[0016] (Element Pattern) The element pattern 1 is provided to asymmetrically reflect incident electromagnetic waves and reflect them in a direction different from that of symmetric reflection. The thickness of the element pattern is, for example, 10 nm or more and 105 μm or less. The element pattern 1 preferably has a surface resistance of 100 Ω / □ or less. The material used for the element pattern 1 may be, for example, a conductive material. The same material as that used for the ground layer 3 may be used as the material. A conductive inorganic or organic material may be formed on the dielectric layer. From the viewpoints of flexibility, film formation, stability, sheet resistance, and low cost, it is preferable to use a film formed by vapor deposition, which is a formation method described below, as the element pattern 1.

[0017] The shape of the element pattern 1 may be, but is not limited to, a cross patch. FIG. 2 is a diagram showing an example of the element pattern shape. As shown in FIG. 2, a reflectarray may be formed using element patterns 1 of any shape that reflects radio waves, such as a continuous film, a mesh, or a punched shape. For example, instead of the cross patch ( FIG. 2( a)), a cubic patch ( FIG. 2( b)), a cylindrical patch ( FIG. 2( c)), a triangular prism patch ( FIG. 2( d)), a Jerusalem cross patch ( FIG. 2( e)), a plurality of parallel conductive patterns ( FIG. 2( f)), a ring-shaped conductive pattern ( FIG. 2( g)), or an element pattern ( FIG. 2( h)) that combines a plurality of these may be used.

[0018] A case where the element pattern 1 is a cross patch will be described. A cross patch refers to a shape in which two rectangular patches intersect at right angles in the xy plane. The length of the element pattern of the cross patch is referred to as the element length, and the width of the element pattern of the cross patch is referred to as the element width. The reflection phase of the unit cell is controlled by varying either the element length or the element width, or both. When the element length is fixed, it is desirable to set the element length value as large as possible within the unit cell. By setting it large, it becomes easier to obtain desired reflection phase characteristics. Furthermore, when the element width is fixed, it is desirable to set the element width value as large as possible within the unit cell. Setting the element width value large makes the slope of the reflection phase gentler, thereby improving processing accuracy during processing. Note that the element length is not limited to being set for a cross patch element pattern, but can also be set for element patterns having other shapes. Furthermore, the element length can be set to a common length within the reflection control region, or it can be set to a different length for each element pattern included in the reflection control region.

[0019] The element pattern 1 can be formed by forming a conductive material over the entire surface of the dielectric layer 2 to form a continuous film, followed by processing to form the element pattern, or by directly forming an element pattern layer on the dielectric layer. For metals, methods for forming a continuous film of a conductive material over the entire surface of the dielectric layer 2 can be selected from dry coating, such as sputtering or vapor deposition, or wet coating, such as plating or gravure coating using metallic ink, or die coating. Alternatively, a rolled metal plate can be bonded to the dielectric layer. Similarly, a continuous film can be formed by dry coating if the material is an inorganic oxide material, or wet coating if the material is an organic material. Painting or spraying methods can also be used.

[0020] The element pattern is formed by removing unnecessary portions of the formed continuous film using a removal process such as dry etching, wet etching, or cutting. When removing the element pattern by etching, the edges of the element pattern constituting the reflect array may be rounded (in other words, may become rounded), pinholes may occur, the cross-sectional shape may become forward or reverse tapered, or undercut or overetching may occur. While such shape changes are expected to occur during the etching process, the reflection phase characteristics are acceptable as long as the direction of the main beam of the reflected electromagnetic waves in the basic configuration is within a range of approximately ±5° of the designed reflection angle. Formation by cutting, printing, dry coating, plating, painting, or spraying is also acceptable.

[0021] The element pattern can be directly formed on the dielectric layer by printing using letterpress printing, lithographic printing, intaglio printing, stencil printing, transfer printing, or the like, or by masking the dielectric layer except for the element pattern portion with masking tape or a masking agent, and then forming the element pattern using dry coating, plating, painting, or spraying. The cross-sectional shape of the element pattern is preferably a forward tapered shape that widens from the top to the bottom. The forward tapered shape increases the surface area of ​​the element pattern, which increases the adhesion with the functional layer when the functional layer described below is laminated, making it possible to suppress the inclusion of air bubbles.

[0022] The material of the element pattern 1 may be the same as that of the ground layer 3, or a different material may be used. For example, at least one of the ground layer and the element pattern may be made of Cu or Al. Cu has excellent conductivity, which reduces conductor loss. Al has low density, is lightweight, and is inexpensive, allowing for the formation of a lightweight and inexpensive reflect array.

[0023] When the element pattern 1 is mesh-shaped, the line width of the mesh is preferably 5 μm or more and 30 μm or less, and more preferably 6 μm or more and 15 μm or less. The line spacing of the mesh is preferably 50 μm or more and 500 μm or less, and more preferably 100 μm or more and 300 μm or less. Furthermore, when the wavelength at the operating frequency is λ, the line spacing of the mesh is preferably 0.5 × λ or less, more preferably 0.1 × λ or less, and even more preferably 0.01 × λ or less. If the line spacing of the mesh is 0.5 × λ or less, performance can be ensured. Furthermore, the line spacing of the mesh may be 0.001 × λ or more. When a metal mesh or a transparent conductive material is used, the reflect array exhibits visible light transparency, making it possible to maintain the appearance after installation. When the element pattern is mesh-shaped or a transparent conductive material is used, the reflect array exhibits visible light transparency, making it possible to maintain the appearance after installation.

[0024] When the element pattern 1 is in the form of a thin film, adhesion with the additional function layer and the adhesion improving layer is improved, and the flexibility of the reflectarray can be improved, thereby enabling use on curved surfaces and roll-to-roll production processes. When the element pattern is formed using a thin film, its thickness is preferably greater than the skin depth calculated from the following equation (9): where d is the skin depth, ω is the angular frequency, μ is the magnetic permeability of the material, and σ is the electrical conductivity of the material. In order to increase the reflection efficiency of radio waves, it is necessary to reduce radio wave loss caused by the element, and therefore it is preferable that the surface roughness of the element is small.

[0025] (Dielectric) In addition to simple resins, the dielectric may be a composite material in which paper, glass fiber, carbon fiber, etc. are impregnated with resin. Examples of simple 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 Examples of suitable dielectric materials include 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), and cycloolefin polymer (εr = 2.3 to 2.5). Here, εr indicates the relative dielectric constant. In particular, polyethylene (PS), polyethylene terephthalate (PET), and cycloolefin polymer (COP) are preferred due to their low cost and versatility. The dielectric layer can be a single layer or multiple layers. The dielectric layer may also be made of foamed materials made from the above materials. As the foam, a foam with high flexibility is preferably used.

[0026] Examples of composite materials include composite materials of paper / phenolic resin, paper / epoxy resin, glass / epoxy resin, and glass / fluororesin. Other examples include the use of a mixture containing resin components together, or a mixture containing a dielectric compound and a resin component, from the viewpoint of adjusting the dielectric constant. The dielectric constant of a 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, using the Maxwell-Garnett law. In a mixture of dielectric A with a dielectric constant εa and dielectric B with a dielectric constant εb, when the volume fraction of dielectric A is δa, the dielectric constant εm of the mixture is expressed by the following relational expression (10): Examples of dielectric compounds include barium titanate (εr = 250 to 20,000), titanium oxide (εr = 83 to 183), lead zirconate titanate, strontium tantalate bismuthate, bismuth ferrite, etc. When a transparent dielectric is used, the reflectarray exhibits visible light transmittance, making it possible to maintain the appearance after installation.

[0027] The relative dielectric constant of the dielectric layer 2 is preferably in the range of 1 or more and 20 or less, more preferably in the range of 1 or more and 10 or less, and even more preferably in the range of 2 or more and 4 or less. When the relative dielectric constant is within the above range, it tends to be easier to obtain the desired reflection phase characteristics in the reflectarray. Furthermore, the dielectric loss tangent is preferably in the range of 0.00005 or more and 0.01 or less, and more preferably in the range of 0.00005 or more and 0.001 or less. When it is within the above range, a reflectarray with low dielectric loss can be produced.

[0028] The dielectric layer 2 can be formed by, for example, wet coating such as die coating, comma coating, or gravure coating, melt extrusion such as the T-die method or inflation method, calendar film formation, solution casting, or heat pressing. Alternatively, a co-extrusion method in which multiple resins are extruded into multiple layers to form a film may be used.

[0029] The thickness of the dielectric layer 2 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, making it difficult to design the reflectarray. On the other hand, if it is too thick, it tends to become difficult to ensure the reflection phase, lose flexibility, and increase the total thickness of the reflectarray, 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, setting the thickness of the dielectric layer to a few μm or more and 100 μm or less makes it easy to design the reflectarray.

[0030] (Ground Layer) The ground layer 3 is provided to reflect electromagnetic waves that reach the reflect array 4. It is also used to support and protect the dielectric layer 2. The ground layer is made of a conductive material such as an inorganic oxide material, a metal material, or a conductive organic material. The thickness of the ground layer is, for example, 10 nm to 105 μm.

[0031] For example, inorganic oxide materials and metal materials include indium tin oxide (ITO), indium zinc oxide (IZO), zinc aluminum oxide (AZO), gallium zinc oxide (GZO), antimony tin oxide, Ag, Al, Au, Pt, Pd, Cu, Co, Cr, In, Ag—Cu, Cu—Au, and Ni. Nanoparticles or nanowires containing at least one of these materials may also be used. Conductive organic materials include polythiophene derivatives, polyacetylene derivatives, polyaniline derivatives, polypyrrole derivatives, carbon nanotubes, and graphene. Cu and Al are particularly preferred from the standpoints of material cost, conductivity, and film formation. Furthermore, 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 also be fabricated using ITO or a mixture of polyethylenedioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS) (PEDOT / PSS). The above materials can be used in the form of a continuous film, a mesh, a punched shape, or a periodic structure.

[0032] Here, "mesh" refers to a state in which a conductor has a mesh-like opening (opening) on ​​its plane. When the conductor is formed in a mesh shape, the mesh may be rectangular or rhombic. When the mesh is formed in a rectangular shape, the mesh is preferably square. Square meshes provide good design. A random shape formed by a self-organizing method is also acceptable. A random shape can be used to 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 3 is mesh-shaped or when a transparent conductive material is used, the reflect array exhibits visible light transparency, allowing the reflect array to maintain its appearance after installation. When the ground layer 3 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 mesh line spacing 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 mesh line spacing is 0.5×λ or less, performance can be ensured. Furthermore, the mesh line spacing may be 0.001×λ or more.

[0033] When a metal material is used, the ground layer 3 can be formed by dry coating such as sputtering or vapor deposition; wet coating such as gravure coating or die coating, or surface treatment such as plating. Alternatively, a rolled metal plate can be used as the ground layer. When an inorganic oxide material is used, the ground layer can be formed by dry coating. When an organic material is used, the ground layer can be formed by wet coating. Alternatively, the ground layer can be formed by painting or spraying. When the ground layer 3 is formed as a thin film by plating or vapor deposition, the flexibility of the reflectarray can be improved, thereby enabling its use on curved surfaces and roll-to-roll production processes. When the ground layer 3 is formed as a thin film, its thickness is preferably greater than the skin depth calculated from Equation (9), as with the element pattern. Furthermore, reducing the loss caused by the ground layer can be considered to increase the electromagnetic wave reflection efficiency. Therefore, a small surface roughness of the ground layer is preferable.

[0034] When the ground layer 3 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, thereby imparting the function of transmitting frequencies other than the operating frequency. Furthermore, when a structure in which holes are periodically provided where no conductive material is present is used, it is possible to design a reflect array that asymmetrically reflects the operating frequency while transmitting only specific frequencies.

[0035] In the present disclosure, surface resistance is measured in accordance with JIS-K-7194. The surface resistance measurement method can be appropriately selected from the four-terminal method, two-terminal method, four-probe method, dielectric method, eddy current method, etc. The surface resistance value of the ground layer can be measured using, for example, Loresta GP MCP-T610 (trade name, manufactured by Mitsubishi Chemical Analytech Co., Ltd.).

[0036] (Additional Functional Layer) The function of the additional functional layer 5 can be selected as needed. Examples of additional functions include anti-degradation properties, design properties, protection and scratch resistance, waterproofing, gas and water vapor barrier properties, flame retardancy, non-combustibility, self-extinguishing properties, weather resistance, stain resistance, antibacterial and antiviral properties, chemical resistance, deodorizing properties, and adhesive properties. One of these functions may be added, or a combination of multiple functions may be added. The thickness of the additional functional layer is, for example, 5 μm or more and 6 mm or less. Examples of methods for laminating a sheet-like additional functional layer include lamination and extrusion lamination. Examples of methods for applying a liquid additional functional layer include, but are not limited to, printing, coating, dry lamination, and wet lamination. Furthermore, if the additional functional layer does not have adhesive properties or adhesion properties, an adhesion-improving layer (adhesive) can be used to adhere the additional functional layer to the reflectarray.

[0037] [Weather Resistance] Possible causes of deterioration of reflectarrays include oxidation and absorption of water vapor due to exposure to the atmosphere, and alteration due to light (ultraviolet rays) such as sunlight. In order to prevent deterioration due to oxygen and water vapor, it is possible to provide a layer with excellent gas barrier properties, such as a barrier film, on the surface of the reflectarray. In addition, to prevent deterioration due to oxygen in particular, it is necessary to provide a layer with an oxygen permeability of the functional layer of 500 cc / m or more. ２ It is preferable that the permeability is 1 / 4 atm / day or less. If this condition can be met, films may be laminated, or an overcoat layer may be applied by dry coating or wet coating. These layers may be single layers, or multiple layers may be combined or laminated. Examples of barrier films include simple films such as ethylene-vinyl alcohol copolymer resins, co-extruded multilayer nylon (Ny) films, and wet-coated films coated with vinylidene chloride (PVDC) or polyvinyl alcohol (PVA). In addition, to prevent deterioration of the dielectric layer, antioxidants, deterioration inhibitors, and antioxidant materials may be added when forming the dielectric layer. Similarly, to prevent deterioration due to water vapor, a water vapor permeability of 300 g / m ２It is preferable to provide a layer having a luminance of 1000 u / s or less. To protect against light from sunlight, etc., it is possible to provide a film having UV-cutting properties or a layer having light-shielding properties. In addition, an ultraviolet scattering agent, an ultraviolet absorber, or a light stabilizer may be added. Examples of UV-cutting films include vinyl chloride resins and polyolefin resins.

[0038] [Design] When a reflectarray is installed on the exterior or interior of a building, for example, it may be possible to impart a design to it so that it blends in with the space. Specifically, the design can be imparted by attaching a designed sheet material to the reflectarray using an adhesive, or by welding and attaching a sheet material to the reflectarray by applying heat and pressure. Examples include decorative sheets in which a printed pattern and an embossed surface pattern are harmonized by laminating a base sheet, a base pattern layer, and a transparent thermoplastic resin layer in this order, and decorative sheets in which a color similar to that of real wood or stone is achieved by laminating a pattern layer, a transparent resin layer, and a surface protection layer in this order.

[0039] [Protection and Scratch Resistance] Protection and scratch resistance refers to the function of preventing scratches on the reflectarray and preventing deterioration of the reflectarray itself. Methods for imparting such functions include coating the reflectarray to increase its surface hardness or laminating a synthetic resin film. Evaluation of protection and scratch resistance is carried out using a pencil hardness test based on JIS K5600-5-4, and it is preferable that the hardness is H or higher. In addition, a load of 1,000 gf / cm is used using steel wool (#0000). ２It is preferable that when rubbed with a material, scratches do not occur up to 1000 reciprocating strokes. Examples of synthetic resins include polyethylene terephthalate, cycloolefin polymer, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polymethyl methacrylate, polyester, polyformaldehyde, polyamide, polyphenylene ether, vinylidene chloride, polyvinyl acetate, polyvinyl acetal, AS resin, ABS resin, acrylic resin, fluororesin, nylon resin, polyacetal resin, polycarbonate resin, polyamide resin, and polyurethane resin.

[0040] [Flame retardancy, non-combustibility, self-extinguishing properties] A method of imparting flame retardancy or non-combustibility to a reflectarray is to layer on it non-combustible, semi-non-combustible, or flame-retardant materials that have been certified as fireproof as stipulated in the Building Standards Act. Examples include flame-retardant fibers, flame-retardant plastics, non-combustible paints, and flame-retardant paints. Flame-retardant fibers include halogen-based compounds, phosphorus-based compounds, vinylon fibers, polyetherimide fibers, aramid fibers, polyester fibers, and vinylon fibers. Flame-retardant plastics include plastic materials to which halogen-based, phosphorus-based, or inorganic flame retardants such as aluminum hydroxide and magnesium hydroxide have been added. Furthermore, examples of materials that have self-extinguishing properties include nylon, polycarbonate, and polyvinyl chloride.

[0041] [Anti-fouling, antibacterial, and anti-viral properties] One method of imparting anti-fouling properties to a reflectarray is to laminate or coat it with a hydrophilic or water-repellent substrate. Photocatalytic materials and silica-based materials can be used as hydrophilic materials. Fluorocarbon resin-based, silicone-based, and other materials can be used as water-repellent materials. Antibacterial and anti-viral materials can include photocatalytic materials, chlorine-based materials, organic materials containing cationic polymers, and materials containing metals such as silver and zinc. Formation methods include laminating these materials as films, using them in coating processes, or mixing them when forming a dielectric layer.

[0042] (Adhesion Improvement Layer) The adhesion improvement layer is a layer with adhesive strength that bonds layers together. The adhesion improvement layer may be composed of two or more layers or may be composed of a combination of multiple materials. In this embodiment, the adhesion improvement layer bonds the ground layer and the dielectric layer, or the dielectric layer and the element pattern, or the dielectric layer, the element pattern, and the additional function layer, and is composed of an adhesive. The adhesive may be a water-dispersion adhesive, a solution-based adhesive, a solventless adhesive, or a solid-based adhesive. Examples of adhesives include epoxy resin-based adhesives, polyvinyl acetate-based adhesives, nitrile rubber-based adhesives, phenolic resin-based adhesives, vinyl acetate-based adhesives, chloroprene rubber-based adhesives, acrylic resin-based adhesives, polyvinyl alcohol resin-based adhesives, silicone rubber-based adhesives, styrene-butadiene rubber-based adhesives, and urethane-based adhesives. In addition to the adhesive, the adhesion improvement layer may also contain any synthetic resin or other material or any other component. The thickness of the adhesion improvement layer is, for example, 5 μm to 500 μm. If the additional functional layer does not have adhesiveness or tackiness, it can be attached to the reflectarray using an adhesion improving layer. The term "functional layer" is a general term that includes single or multiple additional functional layers, single or multiple adhesion improving layers, or layers in which single or multiple additional functional layers and adhesion improving layers are stacked.

[0043] (Installation layer) The installation layer is a layer for fixing the reflectarray to the support. For example, an adhesive layer, a sticky layer, or a magnet can be used if the support is made of metal. When a magnet is used, the position and angle of the reflectarray can be easily changed.

[0044] (Support) The reflectarray is installed on a support. The support may be a newly installed panel or pole, or an existing sign, wall, ceiling, etc. It is also possible to use such a support. The support preferably has a mechanism that can adjust the angle of the reflectarray in the vertical or horizontal direction, and more preferably has a mechanism that can move the position of the reflectarray up, down, left, and right. The reflectarray is installed on the support and used as a reflectarray device.

[0045] The reflectarray may also be attached to human skin, clothing, or a wearable device using an installation layer.

[0046] <Reflectarray Design> Next, the design of the reflectarray will be described. (Reflection Control Area) The reflection control area is the smallest area that can reflect electromagnetic waves incident on that area in a predetermined direction. The reflection control area includes not only a two-dimensional area parallel to the area where the electromagnetic waves are incident, but also a layer structure formed in a direction perpendicular to the area.

[0047] Furthermore, a unit cell refers to an area obtained by dividing the reflection control area. A unit cell includes one element pattern. Two or more unit cells exist in one reflection control area. The size of the side of only one unit cell in the x-axis direction is defined as Ux, and the size of the side of only one unit cell in the y-axis direction is defined as Uy. In one reflection control area, the size (length) of a side of multiple unit cells lined up in the x-axis direction is defined as Sx.

[0048] FIG. 3 is an example of a schematic diagram showing an enlarged reflection control region portion. FIG. 3(a) is a perspective view of the reflection control region 6. FIG. 3(b) is a cross-sectional view (FIG. 3(b-1)) of the reflection control region 6 in the xz plane cut by the y direction Uy / 2, and a schematic diagram (FIG. 3(b-2)) showing the design incident angle θi and the design reflection angle θr. FIG. 3(c) is a cross-sectional view of an arbitrary unit cell of the reflection control region 6 in the yz plane cut by the x direction Ux / 2. An element pattern 1 having an element side surface is formed on one xy plane of the dielectric layer 2, and a ground layer 3 is formed on the other xy plane. When the unit cells are obtained by dividing the reflection control region into n equal parts along a predetermined direction, Ux is Sx / n, where n is an integer equal to or greater than 2 (in the example of FIG. 3, the reflection control region is composed of three rectangular unit cells whose long side in the x-axis direction is divided into thirds).

[0049] The reflection control area is designed according to the following procedure. First, the length Sx of the long side of the reflection control area is determined by the following formula (11). Here, Sx is the length of the long side of the reflection control area, λ is the wavelength of the electromagnetic wave applied to the reflectarray (hereinafter also referred to as the "wavelength at the operating (design) frequency"), θi is the angle of incidence, and θr is the angle of reflection. The angle of incidence θi and the angle of reflection θr are values ​​measured in the xz plane. Here, the direction parallel to the z axis is defined as θi = θr = 0°, the angle of rotation in the positive direction of the x axis is defined as θi = θr = 0 to 90°, and the angle of rotation in the negative direction is defined as θi = θr = 0 to -90° (see FIG. 3(b-2)). Next, the reflection phase required in each reflection control area is calculated using the following equation (12). Here, Zs(x) is a function of the surface impedance in the x-direction in the xy plane of the reflection control area, and represents the case where lossless reflection is realized. Also, 120π is the impedance of the incident wave. The equation for the surface impedance is as follows: Here, Φr(x) represents the reflection phase, which is the phase of the reflection coefficient, as shown in the following equation (14). From each equation, the element shape is determined for each position of the unit cell so as to satisfy the reflection phase (deflection angle of R) shown in the following equation (15). In other words, by determining the angle of incidence θi, the angle of reflection θr, and the wavelength λ of the electromagnetic wave, it is possible to calculate the value of the reflection phase at the coordinate in the long side direction of the reflection control region. After the reflection phase is calculated by the above method, the shape of the element pattern is changed so as to satisfy the reflection phase in each unit cell, and a simulation is performed to optimize the shape of the element pattern. When an electromagnetic wave is incident on the element pattern, the relationship between the shape of the element pattern and the reflection phase can be calculated by a simulation using, for example, an electromagnetic analysis tool (High Frequency Structure Simulator: HFSS) or the like.

[0050] (Reflection control region group) A group of reflection control regions is called a reflection control region group. Reflection control region groups include those composed of a group of single reflection control regions (hereinafter also referred to as "single reflection control region group", although this also includes a single reflection control region), and those composed of a combination of multiple types of single reflection control region groups (hereinafter also referred to as "composite reflection control region group"). The reflectarray 40 that is the subject of this embodiment is composed of composite reflection control regions, and is distinguished from reflectarrays 4 composed of single reflection control region groups (hereinafter also referred to as "single reflectarray"). When the reflectarray 40 is composed of composite reflection control region groups, each single reflection control region group that constitutes the composite reflection control region group is arranged so as to be parallel to at least one or both of the x-axis and y-axis.

[0051] <Characteristics of Reflectarrays> The following describes the characteristics exhibited when electromagnetic waves are incident on and reflected from a single reflectarray. As described above, the reflectarray is designed to have an incident angle θi and a reflection angle θr (such a single reflectarray is sometimes denoted as R(θi, θr)). In the following description, the propagation direction of an electromagnetic wave that is incident on a reflectarray of R(θi, θr) at an incident angle θi and reflected at a reflection angle θr is referred to as the forward direction (downstream communication / radiated wave), and the propagation direction of an electromagnetic wave that is incident on the reflectarray at an incident angle θr and reflected at a reflection angle θi is referred to as the reverse direction (upstream communication / received wave). That is, in downstream communication (radiated wave), "incident angle = designed incident angle" and "reflection angle = designed reflection angle," and in upstream communication (received wave), "incident angle = designed reflection angle" and "reflection angle = designed incident angle." When it is desired to clarify whether a certain design incident angle θi is the incident angle for downstream communication or the reflection angle for upstream communication, the subscripts d and u are sometimes added, such as [θi]d for the former and [θi]u for the latter. Similarly, when it is desired to clarify whether a certain design reflection angle θr is the reflection angle for downstream communication (radiated wave) or the incident angle for upstream communication (received wave), the former is sometimes written as [θr]d and the latter as [θr]u. In 5G and 6G communications, the forward direction (downstream communication) generally assumes radio waves propagating in the direction from the base station → reflectarray → terminal, and the reverse direction (upstream communication) assumes radio waves propagating in the direction from the terminal → reflectarray → base station. Furthermore, in millimeter-wave radar (sensor), the forward direction (emission wave) generally refers to radio waves propagating from the radio wave transmitter to the reflectarray to the target, and the reverse direction (received wave) refers to radio waves propagating from the target to the reflectarray to the radio wave receiver. When a reflectarray with retroreflection properties is installed on the target to strengthen the received wave, the "design incident angle = design reflection angle." In this disclosure, unless there is a need to distinguish between applications such as communication and sensors in radio wave propagation, the terms "downstream communication (emission wave)," "upstream communication (received wave)," etc. will be used.

[0052] Fig. 4 is a schematic diagram illustrating characteristic 1 of a single reflectarray. As shown in Fig. 4(a), for a reflectarray 4 of R(θi, θr), radio waves incident at an incident angle [θi]d in downstream communication are reflected most strongly in the direction of a reflection angle [θr]d, and as shown in Fig. 4(b), radio waves incident at an incident angle [θr]u in upstream communication are reflected most strongly in the direction of a reflection angle [θi]u (characteristic 1 of a reflectarray).

[0053] Fig. 5 is a schematic diagram illustrating characteristic 2 of a single reflectarray. As shown in Fig. 5(a), when a radio wave is incident on a reflectarray 4 of R(θi, θr) at an incident angle [θi-α]d that is shifted by several degrees (α degrees) from θi in downstream communication, the radio wave is most strongly reflected in the direction of a reflection angle [θr+α]d that is shifted by several degrees (α degrees) from θr, and as shown in Fig. 5(b), when a radio wave is incident on a reflectarray 4 of R(θi, θr) at an incident angle [θr+α]u that is shifted by several degrees (α degrees) from θr in upstream communication, the radio wave is strongly reflected in the direction of a reflection angle [θi-α]u that is shifted by several degrees (α degrees) from θi (characteristic 2 of a reflectarray).

[0054] Fig. 6 is a schematic diagram illustrating characteristic 3 of a single reflectarray. Fig. 6(a) shows how radio waves are incident on and reflected from a reflectarray 4 of a conventional size of several tens of centimeters square, but in the case of radio waves in the high frequency band used for 5G, as shown in Fig. 6(b), a reflectarray 4 larger than the conventional size of several tens of centimeters square is generally used, in which case the gain increases in principle and the reflected beam by the reflectarray exhibits the characteristic of becoming sharper (characteristic 3 of a reflectarray).

[0055] These characteristics of a single reflectarray cause problems when relaying radio waves. Figure 7 is a schematic diagram showing an example of a failure in radio wave relay using a single reflectarray in 5G / 6G communications. Due to characteristics 2 and 3 of a single reflectarray, in downstream communications, the terminal cannot obtain sufficient received power if (a) the installation position or installation angle of the reflectarray is shifted (see Figure 7(a)), (b) the terminal position is shifted (see Figure 7(b)), or (c) an obstacle such as a person or object temporarily exists in the incoming reflected beam (see Figure 7(c)). Furthermore, due to characteristic 1 of a single reflectarray, communication failure occurs in upstream communications, as in downstream communications, in that the base station cannot obtain sufficient received power.

[0056] <Functions of the Reflectarray of the Embodiment> The reflectarray of the present embodiment has been developed in consideration of the above-described circumstances. FIG. 8 is a schematic diagram illustrating the functions realized by the reflectarray of the present embodiment. First, as shown in FIG. 8( a), the reflectarray 40 has a function of widening the allowable angle range (described below) of the incident beam for downstream communication (Function 1). Second, as shown in FIG. 8( b), the reflectarray 40 has a function of widening the width of the reflected beam for downstream communication (Function 2). Third, as shown in FIG. 8( c), the reflectarray 40 has a function of achieving Functions 1 and 2 in both uplink and downlink communication (Function 3). These Functions 1 to 3 make it possible to provide terminal users with an extremely stable communication environment. Similarly, it makes it possible to provide sensor users with extremely stable moving object detection even in millimeter-wave radar (sensors).

[0057] <Configuration of Reflectarray of Embodiment> Next, the configuration of the reflectarray 40 of this embodiment that realizes the above functions will be described. The reflectarray 40 of this embodiment has a composite reflection control area group formed by combining multiple types of single reflection control area groups that most strongly reflect plane waves from an arbitrary design angle of incidence θi that satisfies formula (1) to an arbitrary design angle of reflection θr that satisfies formula (2) for electromagnetic waves in a specific frequency band. The composite reflection control area group is preferably formed by juxtaposing three or more single reflection control area groups with different design angles of incidence or design reflection angles in the x-axis direction. The manner in which they are juxtaposed may be formed by arranging separate single reflectarrays side by side, or may be formed integrally on a common dielectric layer, and is not particularly limited.

[0058] 9A is a schematic diagram showing an overall image of incident and reflected downstream communication radio waves (radiated waves) in the reflectarray of embodiment 1. In the reflectarray 40, which is a composite reflection control region group, the design incident and reflection angle of the single reflection control region group 4-0 located at the center is defined as the design central incident angle θi ０ and the design central reflection angle θr ０ 9A, it is preferable that the design incident and reflection angles of the single reflection control regions arranged around it are all shifted by the same amount from the design central incident and reflection angle. For example, as shown in FIG. 9A, ０ , θr ０ ) reflection control area group 4-0 is arranged, and on both sides of it, (θi ０ -α, θr ０ -α) and the reflection control area group 4-1 of R(θi+α, θr ０ The positions of reflection control area group 4-1 and reflection control area group 4-2 may be reversed.

[0059] In the reflect array 40 of the first embodiment, in downstream communication (radiated wave), as shown in FIG. 9A, the design central incident angle [θi ０ ]d strikes all of the reflection control area groups (4-0, 4-1, 4-2) that make up the reflect array 40 at an incident angle [θi ０]d and are reflected asymmetrically by each reflection control area group. At the far-field distance, the reflected waves from each reflection control area group are combined and reflected at the design central reflection angle [θr ０ ]d is a plane wave with a beam width of ±β degrees (described later). Similarly, the design central incident angle [θi ０ ]d, other plane waves incident from an angle range of ±α degrees are reflected by the design central reflection angle [θr ０ ]d, it becomes a plane wave with a beam width of ±β degrees (described later).

[0060] (Embodiment 1-1) In the reflect array 40 of embodiment 1-1, in downstream communication (radiation wave), the design central incident angle [θi ０ ]d, and a plane wave is incident within an angle range of ±α degrees ("downward incident angle range ±α") that satisfies the following formula (3). ０ ]d in the angle range of ±α degrees ("downstream reflection angle range ±α"). Here, "strong reflection" means that when radio waves incident within the downstream incident angle range ±α are reflected, the average value of the reflection intensity (bistatic RCS [sm]) within the downstream reflection angle range ±α is 5 dB or more higher than the average value of the reflection intensity within the angle range of -90 degrees to 90 degrees excluding the downstream reflection angle range ±α. Furthermore, in the reflectarray 40 of embodiment 1-1, when the reflection intensity (RCS [sm]) of the plane wave from the incident angle [θi]d of the downstream communication (radiation wave) to the reflection angle [θr]d is σ[θi]d[θr]d, the reflection intensity variation coefficient C [θｒ]ｄThe coefficient of variation is characterized by being 0.6 or less. Here, the coefficient of variation is an index showing the relative variation in data, and is calculated by dividing the standard deviation of the reflection intensity at each reflection angle within the downward reflection angle range ±α for incident waves from the downward incidence angle range ±α by the average, thereby deriving the degree of variation in reflection intensity at each reflection angle due to deviations in the incidence angle. j in equation (4) is a variable corresponding to each analysis angle when the incidence angle range of -α to α degrees is divided by 1 degree, and the number of analysis angles is 2α + 1. It is also possible to derive the coefficient of variation by replacing equation (4) with an integral using j as a continuous variable. A smaller coefficient of variation means a smaller degree of variation in reflection intensity due to differences in the incidence angle.

[0061] As described above, in the reflectarray 40 of embodiment 1-1, plane wave radio waves incident within the downstream incident angle range ±α are strongly reflected within the downstream reflection angle range ±α, and the coefficient of variation, which indicates the degree of variation in the reflection intensity of radio waves reflected within the downstream reflection angle range ±α for all radio waves incident within the downstream incident angle range ±α, is kept at 0.6 or less. The angle range ±α in this case is called the allowable incident angle range. Therefore, it can be said that the reflectarray 40 of embodiment 1-1 has the function of widening the allowable incident angle range for downstream communication (radiated waves) to any value of α that satisfies equation (3) (Function 1, see FIG. 8( a) and the like).

[0062] (Embodiment 1-2) In addition to the functions of embodiment 1-1, the reflectarray 40 of embodiment 1-2 reflects any plane wave incident in the downstream incident angle range ±α in downstream communication (radiated wave) at a design central reflection angle [θr ０ ]d as the center and can be reflected in an angle range of ±β degrees (hereinafter referred to as the "downstream reflection angle range ±β") that satisfies the following formula (6) (see FIG. 9A). Here, "reflected in a spread" means that when a radio wave incident at an arbitrary incident angle [θi]d within the downstream incident angle range ±α is reflected, the diffusion degree d of the reflection pattern (bistatic RCS [sm]) derived from the following formula (7) is within the downstream reflection angle range ±β. [θｉ]ｄ This means that the value is 0.6 or more. Here, the uniformity of the reflection directional characteristics of radio waves in a metamaterial diffuse reflector is defined as the diffusion coefficient. Specifically, the autocorrelation coefficient of the RCS for each reflection direction for an incident wave from a certain direction is derived. k is a variable corresponding to each analysis angle when the reflection angle range of -β to β degrees is divided by 1 degree, and the number of analysis angles is 2β + 1. It is also possible to derive the diffusion coefficient by replacing equation (7) with an integral using k as a continuous variable. Generally, for perfect diffuse reflection that is uniform in all directions, dθ = 1, and for perfect specular reflection, dθ = 0. Therefore, a higher diffusion coefficient means that the reflection intensity is spread evenly over a wider range. Therefore, the reflectarray 40 of embodiment 1-2 has the function of uniformly widening the width of the reflected beam in downstream communication (radiated wave) within the downstream reflection angle range of ±β (function 2, see FIG. 8(b) and the like).

[0063] [Embodiment 2] Fig. 9B is a schematic diagram showing an overall image of incident and reflection of upstream communication radio waves (received waves) in a reflectarray of embodiment 2. The reflectarray 40 is the same as that used in downstream communication (radiated waves). In upstream communication (received waves), as shown in Fig. 9B, the design central reflection angle [θr ０ ]u strikes all of the reflection control area groups (4-0, 4-1, 4-2) that make up the reflect array 40 at an incident angle [θr ０ ]u and are reflected asymmetrically by each reflection control area group. At the far-field distance, the reflected waves from each reflection control area group are combined and reflected at the design central incident angle [θi ０ ]u is a plane wave with a beam width of ±β degrees. Similarly, any other plane wave incident from the downward reflection angle range ±α is reflected from the design central incident angle [θi ０ ]u becomes a plane wave with a beam width of ±β degrees.

[0064] (Embodiment 2-1) In addition to the functions of embodiment 1-1, the reflectarray 40 of embodiment 2-1 strongly reflects a plane wave incident within the downstream reflection angle range ±α to the downstream incident angle range ±α in upstream communication (received wave). Here, "strong reflection" means that, similar to downstream communication (radiated wave), when a radio wave incident within the downstream reflection angle range ±α is reflected, the average value of the reflection intensity (bistatic RCS) within the downstream incident angle range ±α is 5 dB or more higher than the average value of the reflection intensity within the angle range from -90 degrees to 90 degrees excluding the downstream incident angle range ±α. Furthermore, the reflectarray 40 of embodiment 2-1 has a reflection intensity variation coefficient C , which is derived from the following equation (5) at any reflection angle [θi]u within the downstream incident angle range ±α, where σ[θr]u[θi]u is the reflection intensity (RCS[sm]) of a plane wave from an incident angle [θr]u in upstream communication (received wave) to a reflection angle [θi]u: [θｉ]ｕ The variation coefficient is 0.6 or less. The meaning of the variation coefficient is the same as that of the downstream communication (radiated wave), so details are omitted here. Similar to downstream communication (radiated waves), the reflect array 40 of embodiment 2-1 can be said to have the function of expanding the allowable incident angle range in upstream communication (received waves) to any value of α that satisfies equation (3) (function 3, see Figure 8 (c) etc.).

[0065] (Embodiment 2-2) In addition to the functions of embodiment 1-1, the reflectarray 40 of embodiment 2-2 reflects any plane wave incident in the downstream reflection angle range ±α in upstream communication (received wave) at a design central incident angle [θi ０ ]u, which satisfies Equation (6) (see FIG. 9B). Here, "reflecting with a spread" means that when radio waves incident at any incident angle [θr]u within the downstream reflection angle range ±α are reflected, the diffusion factor d[θr]u of the reflection pattern (bistatic RCS) derived from Equation (8) below is 0.6 or greater within the upstream reflection angle range ±β. The meaning of diffusion factor is the same as in the case of downstream communication (radiated waves), so details will be omitted. In this way, the reflect array 40 of embodiment 2-2 has the function of uniformly widening the width of the reflected beam in upstream communication (received wave) within the upstream reflection angle range ±β (function 3, see Figure 8 (c) etc.).

[0066] <Examples> An example (Example 1) and comparative examples (Comparative Example 1 and Comparative Example 2) relating to a reflectarray that performs asymmetric reflection with different angles of incidence and reflection, and an example (Example 2) and comparative example (Comparative Example 3) relating to a reflectarray that retroreflects electromagnetic waves in the incident direction will be described. The reflection characteristic results described in the examples and comparative examples were analyzed using finite element analysis software (HFSS) manufactured by Ansys. (Example 1) FIG. 10 is a schematic diagram of the arrangement of reflection control regions (groups) in the reflectarray of Example 1. The reflectarray 40 in Example 1 has three types of reflection control region groups 4-0, 4-1, and 4-2 arranged parallel to the x-axis direction such that the reflection control region groups 4-1 and 4-2 are located on both sides of the reflection control region group 4-0, and each reflection control region group has multiple reflection control regions (6-0, 6-1, 6-2) arranged parallel to the x-axis and y-axis directions. Here, the reflection control areas 6-0, 6-1, and 6-2 have a design incident reflection angle (θi ０ , θr ０ ), R(θi ０ -α, θr ０ −α), (θi ０ +α, θr ０ +α), the length Sx of the long side of the reflection control region is also different. On the other hand, in order to prevent misalignment of the element pattern in the y-axis direction, the lengths of the short sides of the reflection control regions 6-0, 6-1, and 6-2 (= the length of one side of the unit cell) are unified to the longest Uy. This makes it possible to facilitate processing of the reflectarray.

[0067] The reflectarray was constructed using 0.018 mm (18 μm) thick copper for the element pattern and ground layer, and a 0.764 mm thick glass / fluororesin composite material for the dielectric. The copper conductivity was 5.8 × 10^7 siemens / m, the real part of the dielectric constant was 2.6, and tan δ was 0.0025. The operating frequency was 28 GHz, the design incident reflection angle was set for each reflection control region group, and the x-axis size Sx of the reflection control region was determined using equation (11). The number of divisions of the reflection control region was set to 3, and the y-axis size Uy (= Sx / 3) of the reflection control region in reflection control region groups 4-0, 4-1, and 4-2 was unified to the largest value. The element shape was a cross patch in the xy plane, with two square patches orthogonal to each other. Here, the element lengths of each element pattern within the reflection control region were the same, with only the element widths differing. Each of reflection control region groups 4-0, 4-1, 4-2 has four reflection control regions 6-0, 6-1, 6-2 arranged in the x-axis direction, and an optimum number arranged in the y-axis direction. Specific specifications are shown in Table 1.

[0068] The coefficients of variation in downstream communication (radiated wave) and upstream communication (received wave) in Example 1 are shown in Table 2. In downstream communication (radiated wave), the design central incident angle [θi ０ ]d, the angle of incidence range of -5 to +5 degrees (α = 5) is divided into 1 degree increments, and the design central reflection angle [θr ０ ]d, the reflection was strong in the angular range of -5 to +5 degrees with 45 degrees as the center. Furthermore, as shown in Table 2, the coefficient of variation Cθ ​​of the reflection intensity (bistatic RCS) derived from equation (4) at each reflection angle when the angle range is divided by 1 degree was 0.6 or less for all analysis angles. Similarly, for uplink communication (received wave), the coefficient of variation Cθ ​​of the reflection intensity (bistatic RCS) derived from equation (4) at each reflection angle when the angle range is divided by 1 degree was 0.6 or less for all analysis angles. ０ ]u, which is 45 degrees, is the center, and the incident angle range of -5 to +5 degrees (α = 5) is divided into 1 degree increments. For all plane waves incident at each analysis angle (analysis angle number 11), the design central incident angle [θi ０]u, the reflection intensity was strong in the angle range of -5 to +5 degrees, with 0 degrees as the center. Furthermore, as shown in Table 2, the coefficient of variation Cθ ​​of the reflection intensity (bistatic RCS) at each reflection angle when this angle range is divided by 1 degree was 0.6 or less at all analysis angles.

[0069] The diffusion rates in downstream communication (radiated wave) and upstream communication (received wave) in Example 1 are shown in Table 3. As shown in Table 3, in downstream communication (radiated wave), the design central incident angle [θi ０ ]d, the allowable angle range of -5 to +5 degrees is divided into 1 degree increments, and the plane wave is incident at each angle of incidence, ０ ]d, the divergence dθ of the reflection pattern (bistatic RCS) derived from equation (7) using the analysis angle (number of analysis angles: 21) when the reflection angle range (β = 10) of -10 to +10 degrees is divided in 1-degree increments with 45 degrees as the center, was 0.6 or more for all incident angles. As shown in Table 3, in the uplink communication (received wave), the divergence dθ of the reflection pattern (bistatic RCS) was 0.6 or more for all incident angles. ０ ]u, which is 45 degrees as the center, and the allowable angle range of -5 to +5 degrees is divided into 1 degree increments, and the plane wave is incident at each angle of incidence, ０ The diffusivity dθ of the reflection pattern (bistatic RCS) derived from equation (8) using the analysis angle (number of analysis angles: 21) when the reflection angle range of −10 to +10 degrees (β=10) centered at 0 degrees, which is u, is divided by 1 degree was 0.6 or more at all angles of incidence.

[0070] Comparative Example 1 The reflectarray of Comparative Example 1 was composed of a single reflection control region group, and similarly to Example 1, the number of divisions of the reflection control region was set to 3, and the size Uy (= Sx / 3) of the reflection control region in the y-axis direction was determined. Furthermore, in Comparative Example 1, the reflectarray had a total of 432 reflection control regions arranged in the x-axis and y-axis directions (12 x 36). Specific specifications are shown in Table 1. The coefficient of variation Cθ ​​of the reflection intensity (bistatic RCS) in uplink and downlink communication was derived using the same method as in Example 1, and as shown in Table 2, it was greater than 0.6 at all analysis angles for both uplink and downlink communication. Furthermore, the diffusivity dθ of the reflection pattern (bistatic RCS) in uplink and downlink communication was derived using the same method as in Example 1, and as shown in Table 3, it was less than 0.6 at all incident angles for both uplink and downlink communication.

[0071] Comparative Example 2 The reflectarray of Comparative Example 2 is composed of composite reflection control region groups, but the design incident / reflection angles of each reflection control region group 4-0, 4-1, and 4-2 are different from those of Example 1. However, as in Example 1, the number of divided reflection control regions is set to three, and the size Uy (= Sx / 3) of the reflection control region in the y-axis direction within the reflection control region groups 4-0, 4-1, and 4-2 is unified to the largest value. Specific specifications are shown in Table 1. When the coefficient of variation Cθ ​​of the reflection intensity (bistatic RCS) in uplink and downlink communication was derived using the same method as in Example 1, it was greater than 0.6 at some analysis angles for both uplink and downlink communication, as shown in Table 2. Furthermore, when the diffusivity dθ of the reflection pattern (bistatic RCS) in uplink and downlink communication was derived using the same method as in Example 1, it was less than 0.6 at some angles of incidence for uplink communication (received waves) and at all angles of incidence for downlink communication (emitted waves), as shown in Table 3.

[0072] Table 1 shows the specifications of the reflect arrays in Example 1, Comparative Example 1, and Comparative Example 2.

[0073] Table 2 shows the coefficient of variation Cθ ​​of the reflect arrays in Example 1, Comparative Example 1, and Comparative Example 2.

[0074] Table 3 shows the diffusivity dθ of the reflect arrays in Example 1, Comparative Example 1, and Comparative Example 2.

[0075] 11 is a graph showing the reflection patterns (bistatic RCS) of the reflectarrays of Example 1 and Comparative Examples 1 and 2. The graph on the right side of the downstream communication (radiated wave) shows the design central reflection angle [θr ０ ]d (45 degrees) and the right graph of the upstream communication (received wave) is an enlarged view of the reflection pattern in the angular range of ±β (β = 10) centered on the design central incident angle [θi ０ 11 is an enlarged view of the reflection pattern in the angular range of ±β (β = 10) centered at ]u (0 degrees). As shown in FIG. 11 , Example 1, Comparative Example 1, and Comparative Example 2 asymmetrically reflect radio waves with directivity in the 45-degree direction in downstream communication (radiated waves), and the analysis results show that the reflection intensity in the ±5-degree range is 5 dB or more higher than the reflection intensity in other reflection directions. Similarly, in upstream communication (received waves), the analysis results show that radio waves are asymmetrically reflected with directivity in the 0-degree direction, and the reflection intensity in the ±5-degree range is 5 dB or more higher than the reflection intensity in other reflection directions. Furthermore, it can be seen that the width of the asymmetric reflected beam in Comparative Example 1 is narrow, and the reflection intensity clearly varies depending on the incident angle. The width of the asymmetric reflected beam in Comparative Example 2 is relatively wide, but it can be seen that the reflection intensity clearly varies depending on the incident angle, as in Comparative Example 1. Furthermore, it can be seen that the spread width of the reflected beam in both Comparative Examples 1 and 2 is smaller in upstream communication (received waves) than in downstream communication (radiated waves). In contrast to this, in Example 1, the width of the asymmetric reflected beam is wide for both uplink and downlink communications, and it is clear that the degree of variation in reflection intensity due to the angle of incidence is small.

[0076] (Example 2) Similar to Example 1, reflectarray 40 of Example 2 has three types of reflection control region groups 4-0, 4-1, 4-2 arranged in parallel in the x-axis direction such that reflection control region groups 4-1, 4-2 are arranged on both sides of reflection control region group 4-0, as shown in the schematic diagram of the arrangement of reflection control region(s) in Figure 10, and each reflection control region group has a plurality of reflection control regions (6-0, 6-1, 6-2) arranged in parallel in the x-axis and y-axis directions. Here, reflection control regions 6-0, 6-1, 6-2 have a design incident reflection angle (θi ０ , θr ０), R(θi ０ -α, θr ０ −α), (θi ０ +α, θr ０ +α), the length Sx of the long side of the reflection control region is also different. On the other hand, in order to prevent misalignment of the element pattern in the y-axis direction, the lengths of the short sides of the reflection control regions 6-0, 6-1, and 6-2 (= the length of one side of the unit cell) are unified to the longest Uy. This makes it possible to facilitate processing of the reflectarray.

[0077] The reflectarray was constructed using 0.035 mm (35 μm) thick copper for the element pattern and ground layer, and 0.600 mm thick epoxy resin for the dielectric. The copper conductivity was 5.8 × 10^7 siemens / m, the real part of the dielectric's relative permittivity was 4.175, and tan δ was 0.014. The operating frequency was 24.15 GHz, the design incident reflection angle was set for each reflection control region group, and the x-axis size Sx of the reflection control region was determined using equation (11). The number of divisions of the reflection control region was set to 3, and the y-axis size Uy (= Sx / 3) of the reflection control region in reflection control region groups 4-0, 4-1, and 4-2 was unified to the largest value. The element shape was a cross patch in the xy plane, with two square patches orthogonal to each other. Here, the element lengths of each element pattern within the reflection control region were the same, with only the element widths differing. Each of reflection control region groups 4-0, 4-1, 4-2 has four reflection control regions 6-0, 6-1, 6-2 arranged in the x-axis direction, and an optimum number arranged in the y-axis direction. Specific specifications are shown in Table 4.

[0078] The coefficient of variation in Example 2 is shown in Table 5. In Example 2, the design central incident angle [θi ０ ]d and the design central reflection angle [θr ０ ]u is equal, and the radio wave is retroreflected. ０ ]d, the incident angle range of -5 to +5 degrees (α = 5) is divided into 1 degree increments, and the design central reflection angle [θr ０]d, the reflection intensity was strong in the angle range of -5 to +5 degrees, with -45 degrees as the center. Furthermore, as shown in Table 5, the coefficient of variation Cθ ​​of the reflection intensity (bistatic RCS) at each reflection angle when this angle range is divided by 1 degree was 0.6 or less at all analysis angles.

[0079] The diffusion factor of Example 2 is shown in Table 6. As shown in Table 6, the design central incident angle [θi ０ For plane waves incident at each incident angle obtained by dividing the allowable angle range of -5 to +5 degrees in increments of 1 degree, with -45 degrees being the center, which is the design central reflection angle [θr0]d, the diffusivity dθ of the reflection pattern (bistatic RCS) derived from equation (7) using the analysis angle (number of analysis angles: 21) when the reflection angle range of -10 to +10 degrees (β = 10) is divided in increments of 1 degree, with -45 degrees being the center, which is the design central reflection angle [θr0]d, was 0.6 or more at all incident angles.

[0080] (Comparative Example 3) The reflectarray of Comparative Example 3 was composed of a single reflection control region group, and as in Example 2, the number of divisions of the reflection control region was set to 3, and the size Uy (= Sx / 3) of the reflection control region in the y-axis direction was determined. Furthermore, in Comparative Example 3, the reflectarray had 12 x 36 reflection control regions arranged in the x-axis and y-axis directions, for a total of 432 regions. Specific specifications are shown in Table 4. The coefficient of variation Cθ ​​of the reflection intensity (bistatic RCS) was derived using the same method as in Example 2, and was greater than 0.6 at some analysis angles, as shown in Table 5. The diffusivity dθ of the reflection pattern (bistatic RCS) was derived using the same method as in Example 2, and was less than 0.6 at all incident angles, as shown in Table 6.

[0081] Table 4 shows the specifications of the reflect arrays in Example 2 and Comparative Example 3.

[0082] Table 5 shows the coefficient of variation Cθ ​​of the reflectarrays in Example 2 and Comparative Example 3.

[0083] Table 6 shows the diffusion degree dθ of the reflect arrays in Example 2 and Comparative Example 3.

[0084] 12 is a graph showing the reflection patterns (bistatic RCS) of the reflectarrays of Example 2 and Comparative Example 3. The graph shows ... reflection patterns (bistatic RCS) of the reflectarrays of Example 2 and Comparative Example 3 are shown in FIG. ０ 12 is an enlarged view of the reflection pattern in the angular range of ±β (β = 10) centered at d (-45 degrees). As shown in Figure 12, Example 2 and Comparative Example 3 retroreflect radio waves with directionality in the -45 degree direction, and the analysis results show that the reflection intensity in the ±5 degree range is 5 dB or more higher than the reflection intensity in other reflection directions. Furthermore, it can be seen that the width of the asymmetric reflected beam in Comparative Example 3 is narrow, and the reflection intensity clearly varies depending on the angle of incidence. In contrast, it can be seen that the width of the retroreflected beam in Example 2 is wide, and the degree of variation in reflection intensity depending on the angle of incidence is also small.

[0085] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention. For example, it goes without saying that combinations of embodiments 1-1 to 2-2 are possible.

[0086] The present invention is not limited to the following embodiments, but may be embodied in various ways: (Embodiment 1) A reflection control area includes a plurality of types of reflection control regions that most strongly reflect a plane wave from an arbitrary design incident angle θi that satisfies formula (1) to an arbitrary design reflection angle θr that satisfies formula (2) for electromagnetic waves in a specific frequency band; In downstream communication (radiated wave), the design central incident angle [θi ０ ]d, and the plane wave is incident within an angle range of ±α degrees (hereinafter referred to as the "downward incident angle range ±α") that satisfies the formula (3), and the plane wave is reflected by the design central reflection angle [θr ０]d (hereinafter referred to as "downward reflection angle range ±α"), the average value of the reflection intensity (bistatic RCS) in the angle range of ±α degrees centered on the downward reflection angle range ±α is 5 dB or more higher than the average value of the reflection intensity in the angle range of -90 degrees to 90 degrees excluding the downward reflection angle range ±α, and, when the reflection intensity of a plane wave from an incident angle [θi]d to a reflection angle [θr]d is σ[θi]d[θr]d, the coefficient of variation C of the reflection intensity derived from equation (4) for any reflection angle [θr]d within the downward reflection angle range ±α [θｒ]ｄ is 0.6 or less. (Aspect 2) In upstream communication (received wave), a plane wave incident within the downstream reflection angle range ±α is strongly reflected within the downstream incidence angle range ±α such that the average value of the reflection intensity (bistatic RCS) within the downstream incidence angle range ±α is 5 dB or more higher than the average value of the reflection intensity within an angle range from -90 degrees to 90 degrees excluding the downstream incidence angle range ±α, and, when the reflection intensity of the plane wave from the incidence angle [θr]u to the reflection angle [θi]u is σ[θr]u[θi]u, the coefficient of variation C of the reflection intensity (bistatic RCS) derived from equation (5) for any reflection angle [θi]u within the downstream incidence angle range ±α is [θｉ]ｕ The reflect array according to aspect 1, wherein (Aspect 3) In downstream communication (radiated wave), a plane wave incident at an arbitrary incident angle [θi]d within the downstream incident angle range ±α is reflected at a design central reflection angle [θr ０ ]d, the diffusivity d of the reflection pattern (bistatic RCS) derived from Equation (7) in the angular range of ±β degrees that satisfies Equation (6) [θｉ]ｄ 3. The reflect array according to aspect 1 or 2, wherein the reflector array reflects light with a spread such that the spread is 0.6 or more. (Aspect 4) In upstream communication (received wave), a plane wave incident at an arbitrary incident angle [θr]u within the downstream reflection angle range ±α is reflected back to the design central incident angle [θi ０4. The reflectarray according to any one of aspects 1 to 3, wherein the reflector reflects with a spread such that the diffusivity d[θr]u of the reflection pattern (bistatic RCS) derived from equation (8) is 0.6 or more in an angular range of ±β degrees centered on θr]u and satisfying equation (6). (Aspect 5) The reflect array according to any one of Aspects 1 to 4, characterized in that it is configured with a reflection control region group including at least three types of reflection control regions having different design angles of incidence θi and design angles of reflection θr. (Aspect 6) The design angles of incidence and design angles of reflection θr are respectively set to the design central incident angle θi ０ And the design central reflection angle θr ０ , design angle of incidence θi ０ -α degrees and design reflection angle θr ０ -α, design angle of incidence θi ０ +α degrees and design reflection angle θr ０+α degrees. (Aspect 7) The reflectarray according to Aspect 5 or 6, characterized in that the reflector has a layer configuration in which an element pattern, a dielectric layer, and a ground layer are laminated in this order, the reflection control region has at least two unit cells in which the length of the short side Uy is equal in any of the reflection control region groups, and one element pattern is disposed in each unit cell. (Aspect 8) The reflectarray according to Aspect 7, characterized in that it further includes an adhesion improving layer. (Aspect 9) The reflectarray according to Aspect 7 or 8, characterized in that it further includes a functional layer. (Aspect 10) The reflectarray according to any one of Aspects 7 to 9, characterized in that the element pattern has a cross patch shape. (Aspect 11) The reflectarray according to any one of Aspects 7 to 9, characterized in that the shape of the element pattern includes a cross patch, and in the reflection control region, the element width in the x-axis direction and / or the element width in the y-axis direction of the element pattern differs for each of the element patterns disposed in at least two unit cells. (Aspect 12) The reflectarray according to any one of Aspects 7 to 11, wherein the ground layer has a form of a continuous film, a mesh, a punched shape, or a periodic structure. (Aspect 13) The reflectarray according to any one of Aspects 7 to 12, wherein the dielectric constant of the dielectric layer is equal to or greater than 1 and equal to or less than 20. (Aspect 14) The reflectarray according to any one of Aspects 1 to 13, wherein the reflectarray is disposed on a support. (Aspect 15) The reflectarray according to any one of Aspects 1 to 13, wherein the reflectarray is attached to human skin, clothing, or a wearing tool by an installation layer.

[0087] REFERENCE SIGNS LIST 1...element pattern, 2...dielectric layer, 3...ground layer, 4, 40...reflector array, 5...additional function layer, 6...reflection control area

Claims

1. For electromagnetic waves in a specific frequency band, the reflector has multiple types of reflection control regions that most strongly reflect a plane wave from an arbitrary design incident angle θi that satisfies formula (1) to an arbitrary design reflection angle θr that satisfies formula (2), In downstream communication (radiated wave), the design central incident angle [θi ０ ]d. The plane wave incident within the angle range of ±α degrees (hereinafter referred to as the "downward incident angle range ±α") that satisfies the formula (3) is reflected by the design central reflection angle [θr ０ ]d (hereinafter referred to as "downward reflection angle range ±α"), the average value of the reflection intensity (bistatic RCS) in the angle range of ±α degrees centered on the downward reflection angle range ±α is 5 dB or more higher than the average value of the reflection intensity in the angle range of -90 degrees to 90 degrees excluding the downward reflection angle range ±α, and, when the reflection intensity of the plane wave from the incident angle [θi]d to the reflection angle [θr]d is σ[θi]d[θr]d, the variation coefficient C of the reflection intensity derived from equation (4) for any reflection angle [θr]d within the downward reflection angle range ±α [θｒ]ｄ is 0.6 or less.

2. In upstream communications (received waves), a plane wave incident within the downstream reflection angle range ±α is strongly reflected within the downstream incidence angle range ±α so that the average value of the reflection intensity (bistatic RCS) within the downstream incidence angle range ±α is 5 dB or more higher than the average value of the reflection intensity within the angle range from -90 degrees to 90 degrees excluding the downstream incidence angle range ±α, and, when the reflection intensity of a plane wave from an incidence angle [θr]u to a reflection angle [θi]u is σ[θr]u[θi]u, the coefficient of variation C of the reflection intensity (bistatic RCS) derived from equation (5) for any reflection angle [θi]u within the downstream incidence angle range ±α is [θｉ]ｕ The reflect array according to claim 1 , wherein the reflect array has a refractive index of 0.6 or less.

3. In downstream communication (radiated wave), a plane wave incident at any incident angle [θi]d within the downstream incident angle range ±α is reflected at the design central reflection angle [θr ０ ]d, the diffusivity d of the reflection pattern (bistatic RCS) derived from Equation (7) in the angular range of ±β degrees that satisfies Equation (6) [θｉ]ｄ The reflect array according to claim 1, wherein the reflector reflects light with a spread such that the λ / 2 is 0.6 or more.

4. In the upstream communication (received wave), a plane wave incident at any incident angle [θr]u within the downstream reflection angle range ±α is reflected at the design central incident angle [θi ０ 2. The reflectarray according to claim 1, wherein the reflector reflects with a spread such that the diffusivity d[θr]u of the reflection pattern (bistatic RCS) derived from equation (8) is 0.6 or more in an angular range of ±β degrees centered on θr]u and satisfying equation (6).

5. In downstream communication (radiated wave), a plane wave incident at any incident angle [θi]d within the downstream incident angle range ±α is reflected at the design central reflection angle [θr ０ ]d, the diffusivity d of the reflection pattern (bistatic RCS) derived from Equation (7) in the angular range of ±β degrees that satisfies Equation (6) [θｉ]ｄ is 0.6 or more, and In the upstream communication (received wave), a plane wave incident at an arbitrary incident angle [θr]u within the downstream reflection angle range ±α is reflected back to the design central incident angle [θi ０ ]u, the reflectarray according to claim 2, characterized in that the reflector reflects with a spread such that the diffusivity d[θr]u of the reflection pattern (bistatic RCS) derived from equation (8) is 0.6 or more in an angular range of ±β degrees centered on θr]u and satisfying equation (6).

6. A reflect array according to any one of claims 1 to 5, characterized in that it is composed of a reflection control region group including at least three types of reflection control regions with different design angles of incidence θi and design angles of reflection θr.

7. The design angle of incidence and the design angle of reflection are respectively the design central angle of incidence θi ０ And the design central reflection angle θr ０ , design angle of incidence θi ０ -α degrees and design reflection angle θr ０ -α, design angle of incidence θi ０ +α degrees and design reflection angle θr ０ 7. The reflect array according to claim 6, wherein the reflector is configured with the reflection control region group including three types of reflection control regions, each of which has a different angle of incidence, i.e., +α degrees.

8. The reflect array according to claim 6, characterized in that it has a layer structure in which an element pattern, a dielectric layer, and a ground layer are laminated in this order, the reflection control area has the same length of short side Uy in any reflection control area group and has at least two unit cells, and one of the element patterns is arranged in each unit cell.

9. The reflect array according to claim 8, further comprising an adhesion improving layer.

10. The reflect array according to claim 8, further comprising a functional layer.

11. The reflect array according to claim 8, wherein the shape of the element pattern is a cross patch.

12. The reflect array according to claim 8, wherein the shape of the element pattern includes a cross patch, and within the reflection control region, the element width in the x-axis direction and / or the element width in the y-axis direction of the element pattern differs for each of the element patterns arranged in at least two unit cells.

13. The reflect array according to claim 8, wherein the ground layer is in the form of a continuous film, a mesh, a punched shape, or a periodic structure.

14. The reflect array according to claim 8, wherein the dielectric layer has a relative dielectric constant of 1 or more and 20 or less.

15. The reflectarray according to any one of claims 1 to 5, characterized in that the reflectarray is disposed on a support.

16. The reflectarray according to any one of claims 1 to 5, characterized in that the reflectarray is attached to human skin, clothing, or a wearing device by an installation layer.

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