JP7525030B1 - Reflect Array Unit - Google Patents

Abstract

[Problem] The present invention aims to provide a reflectarray unit that can freely design the reflection angle, can deliver radio waves over a wide range in space (widening), and has a high yield rate. [Solution] The reflectarray unit of the present invention is characterized in that a plurality of reflectarrays, each including an element pattern, a dielectric layer, and a ground layer, are arranged on a plane, a unit space exists between the reflectarrays, the reflectarrays include at least one reflection control area, and the reflection control area is the same for all of the reflectarrays. The length of the unit space may be at least 1/3 of the length of the reflection control area, and is preferably a natural number multiple of the length of the reflection control area. In addition to reflectarrays arranged at the four corners of a square, a configuration in which a reflectarray is arranged in the center is also included. [Selected Figure] Figure 1

Description

The present invention relates to a reflect array unit.

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

Among these techniques, a reflector using a cross-shaped reflecting element has been developed. Patent Document 1 discloses the following points.
The metasurface reflector includes a dielectric substrate, a metal ground plane provided on the bottom surface of the dielectric substrate that does not transmit any polarized waves in any direction through the metasurface reflector, and a plurality of supercells having two or more types of cross-shaped metal resonators with different arm lengths. The supercells having the metal resonators are formed on the top surface of the dielectric substrate and are arranged with a period of a diffraction grating that reflects vertically polarized waves and horizontally polarized waves of an incident wave and reflects an extraordinary wave of an electromagnetic wave at a specified frequency with a required phase.

In Patent Document 2, a multi-beam reflectarray including first and second array groups is developed.
The first array group includes a plurality of first element arrays, and the second array group includes a plurality of second element arrays, each of the first and second element arrays includes a plurality of elements aligned in a predetermined direction, and the phase difference of radio waves reflected by each of two of the plurality of elements is designed to be proportional to the product of the distance between the two elements and the value of a trigonometric function for the reflection angle by the elements, so that the reflection angle when radio waves of a predetermined wavelength are reflected by the first array group differs from the reflection angle when radio waves of the predetermined wavelength are reflected by the second array group, resulting in a multi-beam reflect array.

In Patent Document 3, a structure having a radio wave reflector is developed.
By providing a curvature to the reflecting surface and creating a structure in which the intensity of the reflected wave when the incident wave is specularly reflected is -30 dB or more compared to the incident wave, radio waves can be transmitted over a wide range of space.

In Patent Document 4, an electromagnetic wave reflecting device has been developed that includes a panel having a reflecting surface that reflects radio waves in a desired band selected from a frequency band of 1 GHz to 170 GHz, and a support that supports the panel.
The support is made of a conductive frame and a slit that receives the edge of the panel. The panel is placed in the slit and an electromagnetic wave reflector is used to improve radio wave propagation for mobile communications both indoors and outdoors.

JP 2021-48465 A Patent No. 5480855 International Publication No. 2022/163813 International Publication No. 2022/196338

Metal reflectors are specular reflectors, so there are limitations to where they can be installed to reflect radio waves from a base station and deliver them to dead zones (areas where communication is not possible). By contrast, a normal reflectarray (metasurface reflector) can be made to reflect radio waves in a direction different from specular reflection (asymmetric reflection) by adjusting the element pattern, allowing freedom in the installation position and angle when delivering radio waves to dead zones.

However, while it is possible to increase the reflection strength by connecting reflectarrays (metasurface reflectors) and increasing their area, there is a problem in that the directionality of the reflected waves increases and the reflection area becomes narrower, making it impossible to deliver radio waves over a wide area to blind zones. Patent documents 1, 3, and 4 do not even disclose any recognition of this issue.

Furthermore, in reflectarrays with element patterns, if dimensional errors occur in the element patterns, the reflection phase in each region tends to vary significantly from the design value, and the reflection intensity in the desired direction may decrease. In addition, if the reflectarray is made up of multiple array groups, the design becomes complicated and causes a decrease in the yield rate during manufacturing. Patent Document 2 discloses the use of two types of reflectors with different reflection angles to address the problem of narrowing the beam area, but this complicates the design and poses the risk of a decrease in the yield rate.

The present invention aims to provide a reflectarray unit that can freely design the reflection angle, can deliver radio waves over a wide area of space (wide area), and has a high yield rate.

To solve the above problems, one representative reflectarray unit of the present invention is characterized in that multiple reflectarrays each including an element pattern, a dielectric layer, and a ground layer are arranged in a plane, a unit space exists between the reflectarrays, the reflectarrays include at least one reflection control area, and the reflection control area is the same for all the reflectarrays.

According to the present invention, it is possible to provide a reflectarray unit that can freely design the reflection angle, can deliver radio waves to a wide range in space (wide area), and has a high yield rate.
Problems, configurations and effects other than those described above will become apparent from the description of the following embodiments.

FIG. 1 is a plan view showing an example of the configuration of a reflect array unit according to the first embodiment. FIG. 2 is a cross-sectional view showing an example of the configuration of the reflect array unit according to the first embodiment. FIG. 3 is a perspective view showing the configuration of the reflect array unit. FIG. 4 is a diagram showing an example of the arrangement of the functional layer 7. As shown in FIG. FIG. 5 is a diagram showing another example of the arrangement of the functional layers. FIG. 6 is a diagram showing an example of the arrangement of unit cells according to the direction in which asymmetric reflection is to be generated. FIG. 7 is a diagram showing an example of the arrangement of unit cells according to the direction in which asymmetric reflection is to be generated. FIG. 8 is a diagram showing an example of the arrangement of unit cells according to the direction in which asymmetric reflection is to be generated. FIG. 9 is a plan view showing an example of the configuration of the reflect array unit according to the second embodiment. FIG. 10 is a cross-sectional view showing an example of the configuration of the reflect array unit according to the second embodiment. FIG. 11 is a schematic diagram showing an example of installation of a reflect array in the prior art. FIG. 12 is a schematic diagram showing an example of installation of a reflect array in an embodiment of the present invention. FIG. 13 is a plan view and a diagram showing reflection characteristics of a unit reflectarray according to Comparative Example 1. In FIG. FIG. 14 is a diagram showing a plan view and reflection characteristics of the reflect array according to the second comparative example. FIG. 15 is a diagram showing a plan view and reflection characteristics of the reflect array according to the third comparative example. FIG. 16 is a diagram illustrating a plan view and reflection characteristics of the reflect array unit according to the first embodiment. FIG. 17 is a diagram illustrating a plan view and reflection characteristics of the reflect array unit according to the second embodiment. FIG. 18 is a diagram illustrating a plan view and reflection characteristics of the reflect array unit according to the third embodiment. FIG. 19 is a diagram illustrating a plan view and reflection characteristics of the reflect array unit according to the fourth embodiment. FIG. 20 is a diagram illustrating a plan view and reflection characteristics of the reflect array unit according to the fifth embodiment. FIG. 21 is a diagram illustrating a plan view and reflection characteristics of a reflect array unit according to Example 6. FIG. 22 is a diagram illustrating a plan view and reflection characteristics of the reflect array unit according to the seventh embodiment. FIG. 23 is a plan view and a diagram showing reflection characteristics of the reflect array unit according to the eighth embodiment. FIG. 24 is a diagram showing a plan view and reflection characteristics of a reflect array unit according to a ninth embodiment. FIG. 25 is a diagram showing a plan view and reflection characteristics of the reflect array unit according to the tenth embodiment. FIG. 26 is a diagram showing a plan view and reflection characteristics of the reflect array unit according to the eleventh embodiment. FIG. 27 is a diagram showing a plan view and reflection characteristics of a reflect array unit according to Example 12. FIG. 28 is a diagram showing a plan view, a cross-sectional view, and reflection characteristics of a reflect array unit according to a thirteenth embodiment. FIG. 29 is a diagram showing a plan view, a cross-sectional view, and reflection characteristics of a reflect array unit according to Example 14. FIG. 30 is a diagram showing a plan view, a cross-sectional view, and reflection characteristics of a reflect array unit according to a fifteenth embodiment. FIG. 31 is a diagram showing a plan view, a cross-sectional view, and reflection characteristics of a reflect array unit according to Example 16.

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

(Explanation of terms)
In this disclosure, a "reflectarray (electromagnetic wave reflector)" is a component that reflects electromagnetic waves and is capable of asymmetric reflection in which the angle of incidence and the angle of reflection are different.
A "reflector array unit (electromagnetic wave reflector assembly)" is an assembly of multiple reflector arrays, and is a component that reflects electromagnetic waves in multiple directions, with the main component being asymmetric reflection, in which the angle of incidence and the angle of reflection differ.
In the following description, it is assumed that an xyz coordinate system is applied and the reflect array is disposed on an xy plane (sometimes simply referred to as a "plane").

A "reflection control area" refers to a part of the area that constitutes the reflectarray. The reflection control area is the smallest area that can reflect electromagnetic waves incident on that area in a specified direction. The reflectarray is composed of one or more reflection control areas. The reflection control area includes not only a two-dimensional area in which the electromagnetic waves are incident in a direction parallel to the area, but also a layer structure formed in a direction perpendicular to the area.
Moreover, the term "unit cell" refers to an area obtained by dividing the reflection control area, and includes one element pattern.

"θi" indicates the angle of incidence of the incident wave. The angle of incidence in the x-axis direction is θix, and the angle of incidence in the y-axis direction is θiy. Furthermore, "θr" indicates the angle of reflection of the reflected wave. The angle of reflection in the x-axis direction is θrx, and the angle of reflection in the y-axis direction is θry.
The angle θx in the x-axis direction is expressed as a positive angle (0° to 180°) when it spreads from the +z-axis direction toward the +x-axis direction, and as a negative angle (0° to -180°) when it spreads from the +z-axis direction toward the -x-axis direction. Similarly, the angle θy in the y-axis direction is expressed as a positive angle (0° to 180°) when it spreads from the +z-axis direction toward the +y-axis direction, and as a negative angle (0° to -180°) when it spreads from the +z-axis direction toward the -y-axis direction.

Regarding the element length of an element pattern (element), the element length in the x-axis direction is denoted as lx, and the element length in the y-axis direction is denoted as ly. In addition, the element width in the x-axis direction is denoted as wx, and the element width in the y-axis direction is denoted as wy.

[First embodiment]
(Reflectarray unit configuration)
The configuration of the reflect array unit 30 according to the first embodiment will be described with reference to Figures 1 and 2. Figure 1 is a plan view showing an example of the configuration of the reflect array unit 30 according to the first embodiment. Also, Figure 2 is a cross-sectional view showing an example of the configuration of the reflect array unit 30 according to the first embodiment. The reflect array unit 30 is an assembly in which a plurality of reflect arrays 20 are arranged on a plane, with a unit space between adjacent reflect arrays. By having a unit space 6 between adjacent reflect arrays 20, asymmetric reflection is the main component, and electromagnetic waves can be reflected in a plurality of other directions.

More specifically, a reflection with a radar scattering cross section RCS of -15 dBsm or more can be obtained at two or more angles excluding the range of ±1 degree of the reference asymmetric reflection (described below), and the RCS of the reflection occurring at a peak angle other than the peak angle at which the RCS is maximum is within 10 dBsm of the maximum value. This makes it possible to deliver electromagnetic waves to the entire area even if the blind zone is large, stabilizing communication connections and communication speeds.

The unit space 6 is preferably an air layer or a resin layer with a dielectric constant of 1 to 1.5. If the unit space 6 is made of a conductive material, specular reflection will be mixed in addition to asymmetric reflection, causing unwanted multipath reflection.

(Reflectarray configuration)
The reflect array 20 is composed of one or more reflection control regions 5 formed by periodically arranging a plurality of element patterns 1 on a plane, and the direction of asymmetric reflection can be set to a desired value (asymmetric reflection set to a desired value is also called "reference asymmetric reflection"). The reflect array 20 includes at least an element pattern (element) 1, a dielectric layer 2, and a ground layer (ground plate) 3. The number of reflection control regions 5 included in the reflect array 20 may be appropriately set according to the desired reflection intensity, and FIG. 1 illustrates an example of a reflect array 20 composed of three reflection control regions 5. In this disclosure, unless otherwise specified, the reflect array 20 composed of three reflection control regions 5 will be described, but the configuration of the reflect array 20 is not limited to this.

Next, the configuration of the reflect array 20 will be described in more detail with reference to FIG. 3. FIG. 3 is a perspective view showing the configuration of the reflect array 20. The reflect array 20 of FIG. 3 generates a predetermined asymmetric reflection of electromagnetic waves along the x-axis. The reflect array 20 of FIG. 3 has a configuration in which a plurality of reflection control regions identical to the reflection control region 5 are arranged in the x-axis and y-axis directions, and in FIG. 3, the reflection control region 5 is shown by a solid line as a representative of the reflection control regions included in the reflect array 20. The reflection control region 5 includes unit cells 4 ₁ , 4 ₂ , 4 ₃ , ..., 4 _n (hereinafter, when the unit cells are not specified, they are also referred to as "unit cells 4". n is a positive integer of 2 or more). The unit cells 4 are parts obtained by dividing the reflection control region 5 at equal intervals along the x-axis direction. n is the number of divisions when the reflection control region is divided into unit cells in the x-axis direction. If the size (length) of the unit cell 4 in the x-axis direction is sx, the size in the y-axis direction is sy, and the size of the reflection control region 5 in the x-axis direction is Lx and the size in the y-axis direction is Ly, then sx=Lx/n and sy=Ly. Note that in FIG. 3, the reflection control region 5 is configured by n unit cells 4 aligned in the x-axis direction, and the reflect array 20 includes a plurality of reflection control regions 5, but the present disclosure is not limited to such a configuration. The reflection control region may be configured by unit cells aligned in the y-axis, or may include unit cells aligned in the x-axis and y-axis. The configuration of the reflection control region will be described later.

(Configuration of element pattern)
An element pattern is formed on the surface of the unit cell 4 facing the +z-axis direction. Using the division number n, the unit cells are expressed as unit cell ₄₁ , unit cell ₄₂ , ..., unit cell _4n . An element pattern ₁₁ is formed in the unit cell _41. An element pattern ₁₂ is formed in _the unit cell 42. An element pattern ₁₃ is formed in the unit cell 43. _An element pattern _1n is formed in the unit cell _4n .
In addition, the element patterns are arranged at equal intervals in the reflection control region and between adjacent regions of the same reflection control region. Specifically, when the size of the closest interval (hereinafter also referred to as "gap") between adjacent element patterns in the x-axis direction for each element pattern in the reflection control region 5 is gx, the element patterns ₁₁ to _1n are arranged at equal intervals of gx in the reflection control region 5. In addition, when the gap between the element pattern 1n in the reflection control region 5 and the element pattern _1x1 of the reflection control region 5x (shown by a broken line, including the unit cell ^4x1 in _which the element pattern _1x1 is formed, the unit cell ^4x2 in which _{the element pattern 1x2 is formed, ... and the unit cell 4xn in which the element pattern 1xn is formed) adjacent to the reflection control region 5 in the x} ^- _axis ^{direction is Gx ,} Gx and gx are equal in FIG. 3.
In addition, ^the gap between the element pattern of reflection control region 5 and the element pattern of reflection control region 5y (shown by dashed ^lines , including unit cell ^4y1 in which element pattern _1y1 is formed, unit cell _4y2 in which element pattern ^1y2 is formed, ... _unit ^{cell 4yn in} which element pattern _1yn is formed) adjacent to reflection control region ₅ in the y-axis direction _is uniform and shown as Gy in Figure 3.

In the reflection control region, each element pattern has a shape slightly different from the other element patterns. Here, the shapes of the element patterns shown in element patterns 1 ₁ to 1 _n are sometimes called cross patches. The cross patch refers to a shape in which two square patches are orthogonal to each other in the xy plane. The element pattern 1 ₁ has a shape in which a square patch having an element length lx1, which is the size in the x-axis direction, and an element width wy1, which is the size in the y-axis direction, and a square patch having an element length ly1, which is the size in the y-axis direction, and an element width wx1, which is the size in the x-axis direction, are orthogonal to each other with a common center of gravity. Similarly, the element pattern 1 _n has a shape in which a square patch having an element length lxn and an element width wyn, and a square patch having an element length lyn and an element width wxn, are orthogonal to each other with a common center of gravity. The method of setting the element length and element width will be described later.

(Explanation of each configuration, design method)
(Layer configuration)
The layer structure of the reflect array 20 will be described with reference to FIG. 4 and FIG. 5. FIG. 4 and FIG. 5 are diagrams showing an example of the layer structure of the reflect array 20. The reflect array 20 has a structure in which at least the element pattern 1, the dielectric layer 2, and the ground layer 3 are stacked in a direction from the +z-axis direction to the -z-axis direction. In the following description, a structure consisting of three layers, the element pattern 1, the dielectric layer 2, and the ground layer 3, is referred to as a "basic structure". In practice, it is preferable that the reflect array 20 has a single or multiple layers having various functionalities (hereinafter also referred to as "functional layers") stacked on the element pattern 1 side or the ground layer 3 side of the basic structure, or on both sides. In the following description, when layers included in the reflect array other than the element pattern 1, the dielectric layer 2, and the ground layer 3 are shown without specifying the type of layer, they may be referred to as "functional layers".

If necessary, a layer for improving the adhesion between the element pattern 1 and the dielectric layer 2, or between the ground layer 3 and the dielectric layer 2, may be formed. A layer used for purposes other than improving the adhesion may also be formed. Note that intermediate products generated during the manufacturing process of the reflect array 20 may be formed in layers and remain on the reflect array 20.

Examples of functional layers include a design layer that is designed to take into consideration the scenery of the area where the reflectarray 20 is installed, an installation layer that allows the reflectarray 20 to be easily installed on a support such as a wall or ceiling, a protective layer that protects the basic structure, and an adhesive layer for laminating each layer.

Figure 4 is a diagram showing an example of the arrangement of the functional layer 7. The lamination method on the element pattern 1 side may be such that the functional layer 7 is laminated so as to fill the gaps between the multiple element patterns 1 as in the reflect array 20a (Figure 4 (a)), the functional layer 7 may be laminated so as to contact the upper surface of the element pattern 1 while maintaining the gaps between the multiple element patterns 1 as in the reflect array 20b (Figure 4 (b)), or the functional layer 7 may be laminated so as not to contact the upper surface of the element pattern 1 as in the reflect array 20c (Figure 4 (c)). Note that when the reflect arrays 20a to 20c have a common configuration except for the functional layer 7, the reflect arrays 20a to 20c have different reflection characteristics. Therefore, it is also possible to change the characteristics of the reflect array by changing the lamination method of the functional layer 7.

Figure 5 shows another example of the arrangement of functional layers. In Figure 5, an example of the arrangement of functional layers is shown, which is a protective layer 8, an adhesive layer 9, a design layer 10, and an installation layer 11. Figure 5(a) shows a reflectarray 20d in which a protective layer 8 is laminated to cover the element pattern 1 and the ground layer 3, and further includes a design layer 10 on the element pattern 1 side via an adhesive layer 9, and an installation layer 11 on the ground layer side via an adhesive layer 9. Figure 5(b) shows a reflectarray 20e in which an installation layer 11 is provided on the ground layer side via an adhesive layer 9, and a design layer 10 is provided on the element pattern 1 side with a gap therebetween.

(Reflection Control Area)
The reflect array 20 includes at least one reflection control area. The properties of the reflect array can be changed depending on how the reflection control areas are arranged. For example, when an electromagnetic wave of a certain wavelength is incident at a certain incident angle, it is possible to give the reflect array a characteristic of reflecting in a single direction by periodically arranging reflection control areas with a common reflection direction. In addition, when an electromagnetic wave of a certain wavelength is incident at a certain incident angle, it is also possible to give the reflect array a characteristic of scattering the electromagnetic wave in multiple directions by configuring a reflect array including reflection control areas with different reflection directions. In addition, it is also possible to give the reflect array a characteristic of collecting electromagnetic waves at a specific location by shifting the reflection direction by a predetermined angle for each reflection control area. The frequency that is expected to be applied to the reflect array at the time of design is hereinafter referred to as the "operating frequency".

The size Lx of the reflection control area in the x-axis direction is determined, for example, by equation (1), where λ is the wavelength of the operating frequency, θix is the x-axis component of the incident angle of the electromagnetic wave incident on the reflection control area, and θrx is the x-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control area. When θix ≠ −θrx,

In addition, the size Ly of the reflection control area in the y-axis direction is determined, for example, by equation (2), where θiy is the y-axis component of the incident angle of the electromagnetic wave incident on the reflection control area, and θry is the y-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control area. When θiy ≠ -θry,

(Relationship between unit cell and reflection phase)
The relationship between the unit cell and the reflection phase will be described with reference to Figs. 6 to 8. Figs. 6 to 8 are diagrams showing an example of the arrangement of unit cells according to the direction in which asymmetric reflection is generated. The reflection control region 5 has at least two unit cells. Here, Fig. 6(a) shows the direction of the electromagnetic wave (incident wave) incident on the reflect array 20f and the direction of the electromagnetic wave (reflected wave) reflected from the reflect array 20f. In other words, the arrow drawn with a thick solid line indicates the traveling direction of the wave front, the arrow toward the reflect array 20f indicates the traveling direction of the wave front of the incident wave, and the arrow away from the reflect array 20f indicates the traveling direction of the wave front of the reflected wave. Also, Fig. 6(b) shows a plan view of the reflect array 20f seen from the z-axis direction. The relationship between (a) and (b) in Figs. 7 and 8 is similar to that between (a) and (b) in Fig. 6.

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

When it is desired to make the reflect array 20f perform asymmetric reflection only along the x-axis direction (θix ≠ -θrx as shown in FIG. 6(a)), unit cells showing different reflection phases are arranged along the x-axis direction in the reflection control area 5a (FIG. 6(b)). The reflection control area 5a has a division number n = 3 and has three unit cells arranged in the x-axis direction. The size Lx of the reflection control area 5a in the x-axis direction is determined by formula (1), and the size of the unit cell in the x-axis direction is Lx/3. In the case where the y-axis component of the reflection angle is symmetric reflection (θiy = -θry) as represented in this example, Ly does not need to be determined by formula (2) and can take any value. However, for ease of design, a square unit cell whose size is determined by Lx and the division number n is used for convenience, and Ly is set equal to Lx/3.

Similarly, when it is desired to make the reflect array 20g perform asymmetric reflection only along the y-axis direction (θiy ≠ -θry as shown in FIG. 7(a)), unit cells exhibiting different reflection phases are arranged along the y-axis direction in the reflection control region 5b (FIG. 7(b)). Here, m (m is a positive integer of 2 or more) is the number of divisions when dividing the reflection control region into unit cells in the y-axis direction. The reflection control region 5b has three unit cells arranged in the y-axis direction, with the number of divisions m=3. The size Ly of the reflection control region 5b in the y-axis direction is determined by equation (2), and the size of the unit cell in the y-axis direction is Ly/3. Since the x-axis component of the reflection angle is a symmetric reflection, Lx does not need to be determined by equation (1) and can be any value. However, for ease of design, a square unit cell whose size is determined by Ly and the number of divisions m is used for convenience, and Lx is set equal to Ly/3.

FIG. 8(a) shows the relationship between the reflect array and the electromagnetic wave, FIG. 8(a1) shows the case where the electromagnetic wave is projected onto the zx plane, and FIG. 8(a2) shows the case where the electromagnetic wave is projected onto the zy plane. When it is desired to make the reflect array 20h perform asymmetric reflection in both the x-axis direction and the y-axis direction (θix≠-θrx as shown in FIG. 8(a1) and θiy≠-θry as shown in FIG. 8(a2)), unit cells with different reflection phases are arranged in the x-axis direction in the reflection control region 5c, and unit cells with different reflection phases are also arranged in the y-axis direction (FIG. 8(b)). The reflection control region 5c includes nine unit cells, three unit cells arranged in the x-axis direction and three unit cells arranged in the y-axis direction. The number of divisions in the reflection control region 5c can also be expressed as 3×3=9, using the number of divisions n=3 in the x-axis direction and the number of divisions m=3 in the y-axis direction. The size Lx of the reflection control region 5c in the x-axis direction is determined by formula (1), and the size Ly of the reflection control region 5c in the y-axis direction is determined by formula (2). The size of the unit cell in the x-axis direction is determined by Lx and n, and is Lx/3. The size of the unit cell in the y-axis direction is determined by Ly and m, and is Ly/3. Both the x-axis component and the y-axis component of the incident wave are reflected asymmetrically. Therefore, the x-axis component of the reflected wavefront in the traveling direction is different from the x-axis component of the incident wavefront in the traveling direction, and the y-axis component of the reflected wavefront in the traveling direction is different from the y-axis component of the incident wavefront in the traveling direction (FIG. 8(a)).
Note that gx indicates the gap in the x-axis direction between the element patterns in the reflection control region 5c. gy indicates the gap in the y-axis direction between the element patterns in the reflection control region 5c. The spacing gx between the element patterns in the x-axis direction is equal, and the spacing gy between the element patterns in the y-axis direction is equal. Although the case where gx and gy are different is shown, gx and gy may be equal.
Furthermore, Gx indicates the gap between the element pattern of reflection control area 5c and the element pattern of the reflection control area adjacent to reflection control area 5c in the x-axis direction. Gy indicates the gap between the element pattern of reflection control area 5c and the element pattern of the reflection control area adjacent to reflection control area 5c in the y-axis direction. When a reflection control area identical to reflection control area 5c is adjacent to reflection control area 5c in the y-axis direction (or x-axis direction) without changing its position in the x-axis direction (or y-axis direction), gx is equal to Gx, and gy is equal to Gy.

(Distribution of reflection phase in reflection control area, distribution of surface impedance)
The distribution of the reflection phase in the reflection control area is determined to follow, for example, formulas (3) and (4). Here, the wavelength of the operating frequency is λ (m), the x-axis component of the incident angle of the electromagnetic wave incident on the reflection control area is θix, the y-axis component is θiy, the x-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control area is θrx, the y-axis component is θry, the reflection phases at arbitrary coordinates x1 and x2 parallel to the x-axis in the reflection control area are φx1 and φx2, respectively, the distance between the coordinates x1 and x2 is dx, and the reflection phase difference between Φx1 and Φx2 is ΔΦx. In addition, the reflection phases at arbitrary coordinates y1 and y2 parallel to the y-axis are φy1 and φy2, respectively. When the reflection control area is to perform asymmetric reflection along the x-axis direction, it is preferable that formula (3) is satisfied, and when the reflection control area is to perform asymmetric reflection along the y-axis direction, it is preferable that formula (4) is satisfied. Furthermore, when it is intended that the reflection control region perform asymmetric reflection in both the x-axis direction and the y-axis direction, it is preferable that the region satisfy both formula (3) and formula (4).

Also, instead of the reflection phase, the distribution of the surface impedance can be applied to the reflection control area. In this case, the distribution of the surface impedance is expressed by, for example, formula (5) and formula (6). Here, Zsx is the surface impedance distribution parallel to the x-axis direction of the reflection control area, Zsy is the surface impedance distribution parallel to the y-axis direction of the reflection control area, and _η1 is the impedance of the incident wave. Also, the x-axis component of the incidence angle of the electromagnetic wave incident on the reflection control area is θix, the y-axis component is θiy, the x-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control area is θrx, and the y-axis component is θry.
Note that x1 and x2 indicate x coordinates as relative coordinates within the reflection control area, and any coordinates within the reflection control area can have a reference x = 0. Similarly, y1 and y2 indicate y coordinates as relative coordinates within the reflection control area, and any coordinates within the reflection control area can have a reference y = 0.
Moreover, _k1 is the wave number of the reflected wave. j indicates an imaginary unit. When the reflection control area is to perform asymmetric reflection along the x-axis direction, it is preferable that the formula (5) is satisfied, and when the reflection control area is to perform asymmetric reflection along the y-axis direction, it is preferable that the formula (6) is satisfied. When the reflection control area is to perform asymmetric reflection in both the x-axis direction and the y-axis direction, it is preferable that both the formula (5) and the formula (6) are satisfied.

Other surface impedance distributions are expressed by, for example, formula (7) and formula (8). When the reflection control area is intended to perform asymmetric reflection only along the x-axis direction, it is preferable that formula (7) is satisfied, and when the reflection control area is intended to perform asymmetric reflection only along the y-axis direction, it is preferable that formula (8) is satisfied. Furthermore, when the reflection control area is intended to perform asymmetric reflection in both the x-axis and y-axis directions, it is preferable that formulas (7) and (8) are satisfied simultaneously.

The above formulas (3) to (8) are examples of design formulas used when designing the distribution of the reflection phase and the distribution of the surface impedance. The present disclosure is not limited to the use of formulas (3) to (8), and other design formulas can be selected as appropriate.

[Second embodiment]
The configuration of the reflect array unit 30 according to the second embodiment will be described with reference to Figures 9 and 10. Figure 9 is a plan view showing an example of the configuration of the reflect array unit 30 according to the second embodiment. Also, Figure 10 is a cross-sectional view showing an example of the configuration of the reflect array unit 30 according to the second embodiment. Since the configuration is the same as that of the first embodiment except that a plurality of reflect arrays 20 are arranged on a support body 12 with unit spaces 6 therebetween to form the reflect array unit 30, a detailed description will be omitted.
The support 12 is made of a dielectric material such as resin, and is preferably a medium with a dielectric constant close to that of air (dielectric constant 1). The hardness of the support may be adjusted appropriately depending on the location where the reflect array unit is to be installed. If the support is set to a predetermined standard size, it can be easily transported and attached to a wide range of materials such as indoor and outdoor building materials, roads, and communication equipment.

<Example>
Fig. 11 is a schematic diagram showing an example of installation of a reflectarray in the prior art. Fig. 12 is a schematic diagram showing an example of installation of a reflectarray in an embodiment of the present invention. An incident wave transmitted from a base station 31 is asymmetrically reflected by a reflectarray unit 30, and can deliver radio waves to a radio wave region 34 in a blind zone 33 caused by a radio wave shield 32. In the prior art, the radio wave region 34 is narrowed (Fig. 11), whereas when the reflectarray unit 30 according to the embodiment of the present invention is used, the radio wave region 34 can be widened, and radio waves can be delivered to a wider range of blind zones than in the prior art.

Simulations in the examples and comparative examples were performed using the finite element method, and calculations were performed assuming that a plane wave was irradiated onto the reflect array unit.
In a real environment, the base station and the reflectarray unit can be appropriately installed taking into account the distance between them so that the reflectarray unit is irradiated with a plane wave. Similarly, the distance between the reflectarray unit and the blind zone can also be appropriately determined so that the reflected wave from the reflectarray unit is a plane wave.
The distance at which a plane wave is generated may be determined based on the far-field distance. For example, when the reflectarray unit is square, the far-field distance x is ^2d2 /λ, where d is the length of one side of the reflectarray unit parallel to the plane formed by the incident wave of the base station and the normal line of the reflectarray unit, and λ is the wavelength. As a specific example, when the reflectarray unit has d=0.3 m and the base station has a frequency of 4.6 GHz, the reflectarray unit and the base station or the blind zone may be separated by 2.76 m or more. However, the above example is a guideline, and the effect of the present invention may not be obtained even if the distance between the reflectarray unit and the base station or the blind zone is shorter than the far-field distance.

素子パターン１およびグランド層３に厚み０．０１８ｍｍの銅を、誘電体層２に厚み０．７６４ｍｍのＣＧＰ－５００を用いた単位リフレクトアレイ２０を構成した。ただし、銅の導電率は５．８×１０＾７ｓｉｅｍｅｎｓ／ｍとし、誘電体層２の比誘電率の実部は２．６、ｔａｎδは０．００２５とした。 Examples and comparative examples will be described below.
(Comparative Example 1)
First, comparative example 1 will be described regarding a reflectarray (hereinafter referred to as a "unit reflectarray") that constitutes the reflectarray unit that is the subject of the embodiment and serves as a unit when arranging them at a distance. Table 1 shows configuration data of the unit reflectarray according to comparative example 1. FIG. 13 is a diagram showing a plan view and reflection characteristics of the unit reflectarray according to comparative example 1. FIG. 13(a) is the plan view, and FIG. 13(b) shows the reflection characteristics. The cross section of the unit reflectarray according to comparative example 1 is similar to the cross section of the reflectarray 20 in FIG. 2. In the following description, the reference symbols for the same parts will be omitted.

A unit reflectarray 20 was constructed using copper with a thickness of 0.018 mm for the element pattern 1 and the ground layer 3, and CGP-500 with a thickness of 0.764 mm for the dielectric layer 2. However, the conductivity of copper was set to 5.8×10^7 siemens/m, the real part of the relative dielectric constant of the dielectric layer 2 was set to 2.6, and tan δ was set to 0.0025.

The operating frequency was set to 27.2 GHz, the target reflection characteristics (target reflection characteristics) were set to θix = 33°, θrx = 0°, θiy = 0°, and θry = 0°, and the size Lx of the reflection control area 5 in the x-axis direction was determined to be 20.238 mm using equation (1).

The number of divisions of the reflection control region 5 was set to 3, and the size of the unit cell in the x-axis direction and the y-axis direction was set to 6.746 mm. The shape of the element pattern was set to a cross patch in which two square patches were orthogonal to each other in the xy plane. Here, only the element width was different in each element pattern in the reflection control region 5, and specifically, the element length was set to lx1=lx2=lx3=ly1=ly2=ly3=3.25 mm, and the element widths in the same element pattern were set to wx1=wy1, wx2=wy2, and wx3=wy3. The reflection phase of the unit cell relative to the element width w was analyzed using HFSS.
In unit cell p, the element length in the x-axis direction is lxp, the element length in the y-axis direction is lyp, the element width in the x-axis direction is wxp, and the element width in the y-axis direction is wyp. However, when lxp and lyp are equal, the subscripts x and y are omitted, when wxp and wyp are equal, the subscripts x and y are omitted, and when the unit cell is not specified, the subscript p may be omitted.

Next, based on the analysis results of the unit cells, the element width w in each unit cell was determined so as to conform to the impedance distribution of equation (8). The element widths w were set to wl = 1.582 mm, w2 = 2.955 mm, and w3 = 0.319 mm.

As shown in FIG. 13(a), the reflect array 20 has 1 x 3 identical reflection control regions 5 arranged in the x-axis and y-axis directions (resulting in 3 x 3 unit cells in the x-axis and y-axis directions), resulting in a size of 20.238 mm square in the xy plane. The reflection characteristics when polarized waves parallel to the x-axis are irradiated onto the reflect array 20 at θix = 33° and θiy = 0° were analyzed using HFSS.

Figure 13 (b) is a diagram showing the reflection characteristics of the unit reflectarray 20 according to Comparative Example 1. The horizontal axis is the reflection angle θry, and the vertical axis is the RCS (radar cross section). The RCS is a value that essentially corresponds to the intensity of the reflected wave. The electromagnetic wave incident at θix = 33° was reflected at its maximum value in the desired θrx = 0° direction (reference asymmetric reflection direction), and the RCS was -19.12 dBsm.

In evaluating the reflection characteristics of the following examples and comparative examples, as described above, a reflection with a radar scattering cross section RCS of -15 dBsm or more can be obtained at any two or more angles excluding the range of ±1 degree of the reference asymmetric reflection, and the RCS of the reflection occurring at a peak angle other than the peak angle at which the RCS is maximum is determined to be within 10 dBsm of the maximum value. If the reflection characteristics satisfy the pass criteria, reflected light having a peak of a predetermined intensity is generated in directions other than the reference asymmetric reflection direction, making it possible to widen the radio wave range 34 with sufficient intensity overall.
In Comparative Example 1, the value of the peak intensity in the reference asymmetric reflection direction where the RCS is maximum does not even reach -15 dBsm, and so the sample is rejected.

(Comparative Example 2)
14A and 14B are diagrams showing a plan view and reflection characteristics of the reflect array according to Comparative Example 2. Fig. 14A is the plan view, and Fig. 14B is the reflection characteristics.
As shown in FIG. 14A, Comparative Example 2 is similar to Comparative Example 1 except that the reflectarray has a configuration in which 2×2 unit reflectarrays 20 are arranged closely together.
In addition, when the analysis was performed using the HFSS, as shown in FIG. 14(b), the electromagnetic wave incident at θix=33° was reflected with a maximum value in the desired direction of θrx=0° (reference asymmetric reflection direction), and the RCS was −6.97 dBsm.
In Comparative Example 2, reflected light having a peak at an angle different from the reference asymmetric reflection direction (-18.01 dBsm at -25°) is generated, but since the difference with the maximum value is greater than 10 dBsm, it is rejected.

(Comparative Example 3)
15A and 15B are diagrams showing a plan view and reflection characteristics of the reflect array according to Comparative Example 3. Fig. 15A is the plan view, and Fig. 15B is the reflection characteristics.
As shown in FIG. 15A, Comparative Example 3 is similar to Comparative Example 1 except that the reflectarray has a configuration in which 3×3 unit reflectarrays 20 are arranged closely together.
In addition, when the analysis was performed using the HFSS, as shown in FIG. 15(b), the electromagnetic wave incident at θix=33° was reflected with a maximum value in the desired direction of θrx=0° (reference asymmetric reflection direction), and the RCS was 0.26 dBsm.
In Comparative Example 3, reflected light having peaks at angles other than the reference asymmetric reflection direction (-12.26 dBsm at -15°, -13.01 dBsm at 15°) is generated, but in either case the difference from the maximum value is greater than 10 dBsm, so it is rejected.

Next, an embodiment of the reflect array unit will be described.
In the following description, the length of the unit space between reflectarrays refers to the average distance of the gap between adjacent reflectarrays that are spaced apart.
Example 1
16A and 16B are diagrams illustrating a plan view and reflection characteristics of the reflect array unit according to Example 1. Fig. 16A is the plan view, and Fig. 16B is the reflection characteristics.
16A, the reflectarray unit 30 according to Example 1 is composed of an assembly of unit reflectarrays arranged with a unit space of 0.5 unit reflectarrays, as opposed to the reflectarray of Comparative Example 2 which is an array of 2 x 2 unit reflectarrays 20. The length of the unit space between each unit reflectarray 20 is 10.119 mm, and the length of one side of the external shape of the reflectarray unit 30 is 50.595 mm.
Some of the incident light irradiated to the reflect array unit 30 as a plane wave is transmitted through the unit space, but when analyzed using HFSS, the reflection characteristics were such that the electromagnetic wave incident at θix = 33° was split into two reflected lights from the reflected light at θrx = 0°, which is the reference asymmetric reflection direction, as shown in Figure 16 (b).

As shown in Figure 16 (b), the peaks of the two reflected lights are seen at RCS -8.39 dBsm at -9° and -8.59 dBsm at 9°. Therefore, since there are two or more reflected lights with peak intensity of RCS of -15 dBsm or more at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, and the difference between the maximum value and the other RCS is within 10 dBsm, it passes.

Example 2
17A and 17B are diagrams illustrating a plan view and reflection characteristics of the reflect array unit according to Example 2. Fig. 17A is the plan view, and Fig. 17B is the reflection characteristics.
17A, the reflectarray unit 30 according to Example 2 is composed of an assembly of unit reflectarrays arranged with a unit space of 0.75 unit reflectarrays, as opposed to the reflectarray of Comparative Example 2 which is an array of 2 x 2 unit reflectarrays 20. The length of the unit space between each unit reflectarray 20 is 15.1785 mm, and the length of one side of the external shape of the reflectarray unit 30 is 55.6545 mm.
Some of the incident light irradiated to the reflect array unit 30 as a plane wave is transmitted through the unit space, but when analyzed using HFSS, as shown in Fig. 17(b), the electromagnetic wave incident at θix = 33° was split into three reflected lights from the reflected light at θrx = 0°, which is the reference asymmetric reflection direction, as shown in Fig. 17(b). Note that the characteristics show a behavior between the reflection characteristics of Example 1 (Fig. 16(b)) and the reflection characteristics of Example 3 (Fig. 18(b)) described later.

As shown in Figure 17(b), the three reflected light peaks are seen at RCS-9.14 dBsm at -12°, -7.26 dBsm at 4°, and -14.63 dBsm at 20°. Therefore, since there are two or more reflected lights with peak intensity of RCS of -15 dBsm or more at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, and the difference between the maximum value and the other RCS is within 10 dBsm, it passes.

Example 3
18A and 18B are diagrams illustrating a plan view and reflection characteristics of a reflect array unit according to Example 3. Fig. 18A is a plan view, and Fig. 18B is a diagram illustrating reflection characteristics.
18A, the reflectarray unit 30 according to Example 3 is composed of an assembly of unit reflectarrays arranged with a unit space of one unit reflectarray therebetween, as opposed to the reflectarray of Comparative Example 2 which is an array of 2 x 2 unit reflectarrays 20. The length of the unit space between each unit reflectarray 20 is 20.238 mm, and the length of one side of the external shape of the reflectarray unit 30 is 60.714 mm.
Some of the incident light irradiated to the reflect array unit 30 as a plane wave is transmitted through the unit space, but when analyzed using HFSS, as shown in Fig. 18(b), the electromagnetic wave incident at θix = 33° showed reflection characteristics in which the reflected light at θrx = 0°, which is the reference asymmetric reflection direction, was split into three reflected lights. In particular, compared to Comparative Example 3, which has the same length on one side of the outer shape but has no unit space, the effect of the presence of the unit space on the broadening of the reflection characteristics was clearly shown.

As shown in Figure 18 (b), the three reflected light peaks are seen at RCS-9.81 dBsm at -15°, -6.80 dBsm at 0°, and -10.58 dBsm at 14°. Therefore, since there are two or more reflected lights with an RCS peak intensity of -15 dBsm or more at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, and the difference between the maximum value and the other RCS is within 10 dBsm, it passes.

Example 4
19A and 19B are diagrams illustrating a plan view and reflection characteristics of a reflect array unit according to Example 4. Fig. 19A is a plan view, and Fig. 19B is a diagram illustrating reflection characteristics.
19A, the reflectarray unit 30 according to Example 4 is composed of an assembly of unit reflectarrays arranged with a unit space of 1.5 unit reflectarrays, as opposed to the reflectarray of Comparative Example 2 which is an array of 2 x 2 unit reflectarrays 20. The length of the unit space between each unit reflectarray 20 is 30.357 mm, and the length of one side of the external shape of the reflectarray unit 30 is 70.833 mm.
Some of the incident light irradiated to the reflect array unit 30 as a plane wave is transmitted through the unit space, but when analyzed using HFSS, as shown in Fig. 19(b), the electromagnetic wave incident at θix = 33° was split into four reflected lights from the reflected light at θrx = 0°, which is the reference asymmetric reflection direction, as shown in Fig. 19(b). Note that the behavior of the characteristics is between the reflection characteristics of Example 3 (Fig. 18(b)) and the reflection characteristics of Example 5 (Fig. 20(b)) described later.

As shown in Figure 19 (b), the peaks of the four reflected lights are seen at RCS-11.43 dBsm at -18°, -7.49 dBsm at -6°, -7.59 dBsm at 6°, and -12.53 dBsm at 18°. Therefore, since there are two or more reflected lights with peak intensity of RCS of -15 dBsm or more at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, and the difference between the maximum value and the other RCS is within 10 dBsm, it passes.

Example 5
20A and 20B are diagrams illustrating a plan view and reflection characteristics of the reflect array unit according to Example 5. Fig. 20A is a plan view, and Fig. 20B is a diagram illustrating reflection characteristics.
20A, the reflectarray unit 30 according to Example 5 is composed of an assembly of unit reflectarrays arranged with a unit space of two unit reflectarrays therebetween, as opposed to the reflectarray of Comparative Example 2 which is an array of 2 x 2 unit reflectarrays 20. The length of the unit space between each unit reflectarray 20 is 40.476 mm, and the length of one side of the external shape of the reflectarray unit 30 is 80.952 mm.
Some of the incident light irradiated to the reflect array unit 30 as a plane wave is transmitted through the unit space, but when analyzed using HFSS, the reflection characteristics showed that the electromagnetic wave incident at θix = 33° was split into five reflected lights from the reflected light at θrx = 0°, which is the reference asymmetric reflection direction, as shown in Figure 20 (b).

As shown in Figure 20 (b), the five reflected light peaks are seen at RCS-13.04 dBsm at -21°, -8.48 dBsm at -10°, -7.00 dBsm at 0°, -8.59 dBsm at 10°, and -14.21 dBsm at 20°. Therefore, since there are two or more reflected lights with an RCS peak intensity of -15 dBsm or more at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, and the difference between the maximum value and the other RCS is within 10 dBsm, it passes.

Example 6
21A and 21B are diagrams illustrating a plan view and reflection characteristics of a reflect array unit according to Example 6. Fig. 21A is a plan view, and Fig. 21B is a diagram illustrating reflection characteristics.
As shown in FIG. 21A, the reflectarray unit 30 of Example 6 has a configuration in which a unit reflectarray is added to the center of the reflectarray unit of Example 3, which is configured with a unit space for one unit reflectarray.
Some of the incident light irradiated to the reflectarray unit 30 as a plane wave is transmitted through the unit space, but when analyzed using HFSS, as shown in Fig. 21(b), the reflection direction (peak angle) indicating the peak intensity of the reflected light split into three was almost the same as in Example 3. On the other hand, the RCS at 0° was larger than the value in Example 3, and it is presumed that reflection from the central unit reflectarray contributed.

As shown in Figure 21 (b), the three reflected light peaks are seen at RCS-12.35 dBsm at -15°, -4.87 dBsm at 0°, and -13.11 dBsm at 15°. Therefore, since there are two or more reflected lights with peak intensity of RCS of -15 dBsm or more at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, and the difference between the maximum value and the other RCS is within 10 dBsm, it passes.

(Example 7)
22A and 22B are diagrams illustrating a plan view and reflection characteristics of a reflect array unit according to Example 7. Fig. 22A is a plan view, and Fig. 22B is a diagram illustrating reflection characteristics.
As shown in FIG. 22A, the reflectarray unit 30 of the seventh embodiment has a configuration in which a unit reflectarray is added to the center of the reflectarray unit of the fourth embodiment, which is configured with a unit space of 1.5 unit reflectarrays.
Some of the incident light irradiated to the reflect array unit 30 as a plane wave is transmitted through the unit space, but when analyzed using HFSS, as shown in Fig. 22(b), the reflection direction (peak angle) showing the peak intensity of the reflected light split into four was almost the same as in Example 4. On the other hand, the RCS at angles less than -15° decreased compared to the value in Example 4, and the RCS at angles greater than 15° tended to increase compared to the value in Example 4.

As shown in Figure 22 (b), the peaks of the four reflected lights are seen at RCS-14.11 dBsm at -18°, -5.53 dBsm at -6°, -10.15 dBsm at 6°, and -10.55 dBsm at 18°. Therefore, since there are two or more reflected lights with an RCS peak intensity of -15 dBsm or more at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, and the difference between the maximum value and the other RCS is within 10 dBsm, it passes.

(Example 8)
23A and 23B are diagrams illustrating a plan view and reflection characteristics of a reflect array unit according to Example 8. Fig. 23A is a plan view, and Fig. 23B is a diagram illustrating reflection characteristics.
As shown in Figure 23 (a), the reflect array unit 30 of Example 8 has a configuration in which a unit reflect array is added to the center of the reflect array unit of Example 5, which is configured with a unit space equivalent to two unit reflect arrays.
Some of the incident light irradiated to the reflect array unit 30 as a plane wave is transmitted through the unit space, but when analyzed using HFSS, as shown in Fig. 23(b), the reflection direction (peak angle) indicating the peak intensity of the reflected light divided into five was almost the same as in Example 5. On the other hand, the RCS near 0° and ±20° decreased compared to the value in Example 5, and the RCS near ±10° tended to increase compared to the value in Example 5.

As shown in Figure 23(b), the peaks of the five reflected lights are seen at RCS-15.68 dBsm at -21°, -6.46 dBsm at -10°, -9.56 dBsm at 0°, -6.1 dBsm at 10°, and -16.82 dBsm at 21°. Therefore, since there are two or more reflected lights with an RCS peak intensity of -15 dBsm or more at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, and the difference between the maximum value and the other RCS is within 10 dBsm, it passes.

Example 9
24A and 24B are diagrams illustrating a plan view and reflection characteristics of a reflect array unit according to Example 9. Fig. 24A is a plan view, and Fig. 24B is a diagram illustrating reflection characteristics.
24A, the reflectarray unit 30 according to the ninth embodiment has an increased number of reflectarrays while leaving a unit space of one unit reflectarray, and has a configuration in which the reflectarray unit according to the third embodiment, which is spaced apart by a unit space of one unit reflectarray, is arranged in the center, and reflectarrays are arranged at the four corners extending diagonally apart by a space of one unit reflectarray. The length of one side of the external shape of the reflectarray unit 30 according to the present embodiment is 141.666 mm.
Some of the incident light irradiated to the reflect array unit 30 as a plane wave is transmitted through the unit space, but when analyzed using HFSS, as shown in Fig. 24(b), the reflection directions (peak angles) showing the peak intensities of the reflected light split into three were almost the same as in Example 3. On the other hand, the RCS of each peak angle showed a tendency to increase compared to the value in Example 3.

As shown in Figure 24 (b), the three reflected light peaks are seen at RCS-4.18 dBsm at -16°, -0.78 dBsm at 0°, and -5.00 dBsm at 16°. Therefore, since there are two or more reflected lights with peak intensity of RCS of -15 dBsm or more at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, and the difference between the maximum value and the other RCS is within 10 dBsm, it passes.

Example 10
25A and 25B are diagrams illustrating a plan view and reflection characteristics of a reflect array unit according to Example 10. Fig. 25A is the plan view, and Fig. 25B is the reflection characteristics.
25A, the reflectarray unit 30 according to Example 10 has an increased number of reflectarrays while leaving a unit space for one unit reflectarray as in Example 9, and has a configuration in which two unit reflectarrays are added to each of the four sides of the outer shape with a unit space for one unit between them, as compared to the reflectarray unit according to Example 9. The length of one side of the outer diameter of the reflectarray unit 30 of this example is 141.666 mm.
Some of the incident light irradiated to the reflect array unit 30 as a plane wave is transmitted through the unit space, but when analyzed using HFSS, as shown in Fig. 24(b), the reflection directions (peak angles) showing the peak intensities of the reflected light split into three were almost the same as in Examples 3 and 9. On the other hand, the RCS of each peak angle showed a tendency to increase compared to the values in Examples 3 and 9.

As shown in Figure 24 (b), the three reflected light peaks are seen at RCS 2.03 dBsm at -16°, 5.33 dBsm at 0°, and 0.99 dBsm at 16°. Therefore, since there are two or more reflected lights with peak intensity of RCS of -15 dBsm or more at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, and the difference between the maximum value and the other RCS is within 10 dBsm, it passes.

(Example 11)
26A and 26B are diagrams illustrating a plan view and reflection characteristics of a reflect array unit according to Example 11. Fig. 26A is a plan view, and Fig. 26B is a diagram illustrating reflection characteristics.
26A, the reflectarray unit 30 of Example 11 has a configuration in which the reflectarray unit of Example 3 arranged in the center is removed from the reflectarray unit of Example 9. The length of the unit space between each unit reflectarray 20 is 101.19 mm, and the length of one side of the outer shape of the reflectarray unit 30 is 141.666 mm.
Some of the incident light irradiated to the reflect array unit 30 as a plane wave is transmitted through the unit space, but when analyzed using HFSS, as shown in Figure 26 (b), there was a tendency for a large number of reflected lights with approximately the same peak intensity to be generated, rather than being divided into reflected lights with significant peak intensities as in Examples 3, 9, and 10.

As shown in Figure 26 (b), the three reflected light peaks corresponding to Examples 3, 9, and 10 are seen at RCS-10.29 dBsm at -16°, -6.90 dBsm at 0°, and -11.05 dBsm at 16°. Therefore, since there are two or more reflected lights with an RCS peak intensity of -15 dBsm or more at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, and the difference between the maximum value and the other RCS is within 10 dBsm, it passes.

Example 12
27A and 27B are diagrams illustrating a plan view and reflection characteristics of a reflect array unit according to Example 12. Fig. 27A is the plan view, and Fig. 27B is the reflection characteristics.
As shown in Figure 27 (a), the reflect array unit 30 of Example 12 has a configuration in which two reflect array units of Example 1, which are spaced apart by a unit space of 0.5 unit reflect arrays, are combined and arranged in the second and fourth quadrants of the xy plane, and two reflect array units of Example 3, which are spaced apart by a unit space of one unit reflect array, are combined and arranged in the first and third quadrants of the xy plane, so that there is a unit space of one unit reflect array between them.
Some of the incident light irradiated to the reflect array unit 30 as a plane wave is transmitted through the unit space, but when analyzed using HFSS, it was found that the reflection characteristics were a superposition of the reflection characteristics of Examples 1 and 3, as shown in Figure 27 (b).

As shown in Figure 27(b), the three reflected light peaks corresponding to Examples 3, 9, and 10 are seen at RCS 0.52 dBsm at -15°, -0.68 dBsm at 0°, and -0.14 dBsm at 14°. Therefore, since there are two or more reflected lights with an RCS peak intensity of -15 dBsm or more at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, and the difference between the maximum value and the other RCS is within 10 dBsm, it passes.

An example of the second embodiment including the support 12 will now be described.
(Example 13)
Fig. 28 is a diagram showing a plan view, a cross-sectional view, and reflection characteristics of a reflect array unit according to Example 13. Fig. 28(a-1) is a plan view, Fig. 28(a-2) is a cross-sectional view, and Fig. 28(b) is the reflection characteristics.
28(a-1) and (a-2), the reflectarray unit 30 according to Example 13 has a configuration in which the reflectarray unit of Example 3, which is spaced apart by a unit space equivalent to one unit reflectarray, is arranged on a support 12. The support 12 is made of styrofoam made of polystyrene, and has a thickness of 30 mm, a dielectric constant ε' = 1.02, and tan δ = 0. The configuration other than the support is the same as that of Example 3.
Some of the incident light irradiated to the reflect array unit 30 as a plane wave passes through the unit space and the support body. However, when analyzed using HFSS, as shown in Figure 28 (b), the reflection characteristics such as the reflection direction (peak angle) and RCS indicating the peak intensity of the reflected light split into three were almost unchanged from those in Example 3.

As shown in Figure 28 (b), the three reflected light peaks are seen at RCS-9.71 dBsm at -15°, -6.41 dBsm at 0°, and -10.39 dBsm at 14°. Therefore, since there are two or more reflected lights with peak intensity of RCS of -15 dBsm or more at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, and the difference between the maximum value and the other RCS is within 10 dBsm, it passes.

(Example 14)
Fig. 29 is a plan view, a cross-sectional view, and a diagram showing reflection characteristics of a reflect array unit according to Example 14. Fig. 29(a-1) is a plan view, Fig. 29(a-2) is a cross-sectional view, and Fig. 29(b) is the reflection characteristics.
29(a-1) and (a-2), the reflectarray unit 30 according to Example 14 has a configuration in which the reflectarray unit of Example 3, which is spaced apart by a unit space equivalent to one unit reflectarray, is arranged on a support 12. The support 12 is an acrylic plate made of acrylic, with a thickness of 30 mm, a dielectric constant ε' = 3.3, and tan δ = 0. The configuration other than the support is the same as that of Example 3.
Some of the incident light irradiated to the reflect array unit 30 as a plane wave passes through the unit space portion and the support body. When analyzed using HFSS, as shown in Figure 29(b), the reflection direction (peak angle) indicating the peak intensity of the reflected light divided into three was almost the same as in Example 3, but the peak intensity in the reference asymmetric reflection direction (0°) decreased and the RCS in the specular reflection direction (33°) increased, indicating an overall tendency for reflection to dissipate.

As shown in Figure 29 (b), the three reflected light peaks are seen at RCS-6.91 dBsm at -15°, -7.42 dBsm at -1°, and -11.51 dBsm at 14°. Therefore, since there are two or more reflected lights with peak intensity of RCS of -15 dBsm or more at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, and the difference between the maximum value and the other RCS is within 10 dBsm, it passes.

(Example 15)
30A and 30B are diagrams showing a plan view, a cross-sectional view, and reflection characteristics of a reflect array unit according to Example 15. Fig. 30(a-1) is a plan view, Fig. 30(a-2) is a cross-sectional view, and Fig. 30(b) is the reflection characteristics.
30(a-1) and (a-2), the reflectarray unit 30 according to Example 15 has a configuration in which the reflectarray unit of Example 3, which is spaced apart by a unit space equivalent to one unit reflectarray, is arranged on a support 12. The support 12 is made of styrofoam made of polystyrene, and has a thickness of 5 mm, a dielectric constant ε' = 1.02, and tan δ = 0. The configuration other than the support is the same as that of Example 3.
Some of the incident light irradiated to the reflect array unit 30 as a plane wave passes through the unit space and the support body. However, when analyzed using HFSS, as shown in Figure 30 (b), the reflection characteristics such as the reflection direction (peak angle) and RCS indicating the peak intensity of the reflected light split into three were almost unchanged from those in Example 3.

As shown in Figure 30 (b), the three reflected light peaks are seen at RCS-9.48 dBsm at -15°, -6.39 dBsm at 0°, and -10.57 dBsm at 14°. Therefore, since there are two or more reflected lights with peak intensity of RCS of -15 dBsm or more at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, and the difference between the maximum value and the other RCS is within 10 dBsm, it passes.

(Example 16)
31 is a diagram showing a plan view, a cross-sectional view, and reflection characteristics of a reflect array unit according to Example 16. Fig. 31(a-1) is a plan view, Fig. 31(a-2) is a cross-sectional view, and Fig. 31(b) is the reflection characteristics.
31(a-1) and (a-2), the reflectarray unit 30 according to Example 16 has a configuration in which the reflectarray unit of Example 3, which is spaced apart by a unit space equivalent to one unit reflectarray, is arranged on a support 12. The support 12 is an acrylic plate made of acrylic, with a thickness of 5 mm, a dielectric constant ε' = 3.3, and tan δ = 0. The configuration other than the support is the same as that of Example 3.
Some of the incident light irradiated to the reflect array unit 30 as a plane wave passes through the unit space portion and the support body. When analyzed using HFSS, as shown in Figure 31(b), the reflection direction (peak angle) indicating the peak intensity of the reflected light divided into three was almost the same as in Example 3, but the peak intensity in the reference asymmetric reflection direction (0°) decreased and the RCS in the specular reflection direction (33°) increased, indicating an overall tendency for reflection to dissipate.

As shown in Figure 31 (b), the three reflected light peaks are seen at RCS-9.49 dBsm at -15°, -5.99 dBsm at -1°, and -9.91 dBsm at 14°. Therefore, since there are two or more reflected lights with peak intensity of RCS of -15 dBsm or more at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, and the difference between the maximum value and the other RCS is within 10 dBsm, it passes.

(Discussion)
In the above examples, when a unit space for p reflectarrays is mentioned, it actually means p times the length of the reflection control area included in the reflectarray (however, the length of the reflection control area means the length (Lx) in the direction in which the multiple unit cells included in the reflection control area are arranged). Therefore, according to the results of the examples, for a reflectarray unit in which the length of the unit space is 0.75 (3/4) of the length of the reflection control area, reflected light with sufficient peak intensity is generated so as to split before and after the reflection angle in the reference asymmetric reflection direction, realizing a wide area, so that a similar effect can be achieved if it is at least 1/3 or more of the length of the reflection control area. And as the length of the unit space increases, there is a tendency for the number of reflected lights split before and after the reference asymmetric reflection direction to increase, making it possible to deliver reflected waves over a wider area.

In particular, when the length of the unit space is n times (n is a natural number) the length of the reflection control area, reflected light having a peak intensity is generated in a direction similar to the reference asymmetric reflection direction, which makes design easier and is preferable (Examples 3 and 5).
In contrast, when the length of the unit space is (n+1/2) times (n is 0 or a natural number) the length of the reflection control area, reflected light having a peak intensity in the reference asymmetric reflection direction does not occur, and reflected light having approximately the same peak intensity tends to occur at angles before and after that (Examples 1 and 4).

When the length of the unit space is n times (n is a natural number) the length of the reflection control area, and a reflectarray is placed at the center of the reflectarray unit in addition to the reflectarrays at the four corners of a square arrangement, the peak intensity in the reference asymmetric reflection direction may increase (Example 6).

When the number of reflectarrays arranged was increased while keeping the length of the unit space constant, the peak reflection intensity tended to increase as the number of reflectarrays increased (Examples 9 and 10).

The reflection characteristics of a reflectarray unit configured by mixing and arranging reflectarray units with different unit space lengths is a superposition of the reflection characteristics of each of the constituent reflectarrays (Example 12).

For reflectarray units equipped with supports, if the dielectric constant of the support is a high value of around 3.3, the reflection characteristics show a tendency for the peak intensity in the reference asymmetric reflection direction to decrease and the RCS in the regular reflection direction to increase, resulting in an overall tendency for reflection to dissipate, so it is desirable for the dielectric constant to be between 1 and 1.5 (Examples 13 to 16). Furthermore, any dielectric material such as a resin with a dielectric constant within this numerical range can be used as the material to fill the unit space.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and various modifications are possible within the scope of the present invention. For example, the configuration of the unit reflectarray is not limited to the examples of the element pattern, unit cell, reflection control region, etc. described in Comparative Example 1. Furthermore, the reflectarray unit is not necessarily limited to arranging multiple reflectarrays on a plane, and it is also possible to arrange them on a curved surface within the scope of the spirit of the present invention.

The following are some possible embodiments of the present invention, but the present invention is not limited to these.
(Aspect 1)
A plurality of reflect arrays each including an element pattern, a dielectric layer, and a ground layer are arranged on a plane;
There is a unit space between the reflectarrays,
The reflect array includes at least one reflection control area,
The reflection control area is the same for all of the reflectarrays.
(Aspect 2)
2. The reflect array unit according to claim 1, wherein the length of the unit space is equal to or greater than 1/3 of the length of the reflection control area.
(Aspect 3)
2. The reflect array unit according to claim 1, wherein the length of the unit space is a natural number multiple of the length of the reflection control area.
(Aspect 4)
The reflect array unit according to any one of aspects 1 to 3, wherein the unit spaces have the same length.
(Aspect 5)
The reflectarray unit according to any one of aspects 1 to 4, comprising, in addition to the reflectarrays arranged at the four corners of a square, the reflectarray arranged in the center.
(Aspect 6)
The reflect array unit according to any one of aspects 1 to 5, wherein the reflect array is disposed on a support.
(Aspect 7)
The reflect array unit according to aspect 6, wherein the support has a relative dielectric constant of 1 or more and 1.5 or less.
(Aspect 8)
the shape of the element pattern includes a cross patch;
The reflect array unit according to any one of aspects 1 to 7, wherein, in the reflection control region, a first element width wx which is a width in the x-axis direction of the element pattern and/or a second element width wy which is a width in the y-axis direction of the element pattern differs for each of the element patterns arranged in at least two unit cells.

1 _{, 1 1} -1 _n , 1 ^x ₁ -1 ^x _n , 1 ^y ₁ -1 ^yn ... element pattern,
2...Dielectric layer,
3...Ground layer,
4 _, 4 ₁ -4 _n , 4 ^x ₁ -4 ^x _n , 4 ^y ₁ -4 ^yn ... unit cell,
5, 5a-5c, 5x, 5y...reflection control area,
6...Unit space 7 Functional layer,
8 protective layer,
9 adhesive layer,
10 Design layer,
11 Installation layer,
12... Support 20, 20a-20h... Reflect array 30... Reflect array unit 31... Base station 32... Radio wave shield 33... Dead zone 34... Radio wave area

Claims (6)

A plurality of reflect arrays each including an element pattern, a dielectric layer, and a ground layer are arranged on a plane;
There is a unit space between the reflectarrays,
The reflect array includes at least one reflection control area,
The reflection control area is the same for all of the reflectarrays,
A reflect array unit , wherein the length of the unit space is equal to or greater than 1/3 or a natural number multiple of a size of the reflection control area in a direction in which a plurality of unit cells are arranged . The reflect array unit according to claim 1 , wherein the unit spaces have the same length. The reflect array unit according to claim 1 , further comprising a reflect array disposed at a center in addition to the reflect arrays disposed at the four corners of a square. The reflect array unit according to claim 1 , wherein the reflect array is disposed on a support. The reflect array unit according to claim 4 , wherein the support has a relative dielectric constant of 1 or more and 1.5 or less. the shape of the element pattern includes a cross patch;
2. The reflect array unit according to claim 1, wherein, in the reflection control region, a first element width wx that is a width in the x-axis direction of the element pattern and/or a second element width wy that is a width in the y-axis direction of the element pattern differs for each of the element patterns arranged in at least two unit cells.

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