Reflect array unit

Abstract

To provide a reflectarray unit that allows flexible design of a reflection angle, is capable of delivering radio waves to a wide spatial area (widening the coverage), and achieves a high yield.SOLUTION: In the reflectarray unit, multiple reflectarrays each including an element pattern, a dielectric layer, and a ground layer are arranged in a plane. Unit spaces are present between the reflectarrays. Each reflectarray includes at least one reflection control region, where the reflection control regions are identical across all the reflectarrays. A length of the unit space may be equal to or greater than one third of a length of the reflection control region, and preferably is a natural number multiple of the length of the reflection control region. The invention includes a configuration where, in addition to reflectarrays at the four corners in a square arrangement, another reflectarray is arranged at the center.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a reflectarray unit.

Background Art

[0002] With the progress of digitalization in society, the data communication speed in wireless communication has improved dramatically, and the electromagnetic waves have become higher in frequency accordingly. However, since electromagnetic waves become more rectilinear as the frequency increases, blind spots where electromagnetic waves cannot penetrate into the shadows of buildings and other areas where communication is impossible are likely to occur. 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 quickly increase the number of base stations. In recent years, technologies for controlling the direction of electromagnetic waves have attracted attention in order to solve these problems.

[0003] Among such technologies, 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 layer provided on the bottom surface of the dielectric substrate that does not transmit the metasurface reflector for all polarization directions, and a plurality of supercells having two or more types of cross-shaped metal resonators with different arm lengths. The supercells having metal resonators are formed on the upper surface of the dielectric substrate, reflect the vertical polarization wave and the horizontal polarization wave of the incident wave, and are arranged at the diffraction grating period that anomalously reflects the electromagnetic wave at a required phase at a predetermined frequency.

[0004] Patent Document 2 has developed a multi-beam reflectarray including first and second array groups. The first array group includes a plurality of first element arrays, 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 the radio waves reflected by each of two elements among the plurality of elements is designed to be proportional to the product of the distance between the two elements and the value of the trigonometric function with respect to the reflection angle by the elements, so that when radio waves of a predetermined wavelength are reflected by the first array group, the reflection angle is different from the reflection angle when the radio waves of the predetermined wavelength are reflected by the second array group, and it can be a multi-beam reflect array.

[0005] In Patent Document 3, a structure having a radio wave reflector has been developed. By making the structure such that the intensity of the reflected wave when the incident wave is specularly reflected is -30 dB or more with respect to the incident wave by providing curvature to the reflecting surface, radio waves can be delivered to a wide range of space.

[0006] In Patent Document 4, an electromagnetic wave reflection device including a panel having a reflecting surface that reflects radio waves in a desired band selected from the frequency band of 1 GHz to 170 GHz and a support that supports the panel has been developed. The support is composed of a conductive frame and a slit that receives the end of the panel. By installing the panel in the slit, the radio wave propagation of mobile communication is improved indoors and outdoors by the electromagnetic wave reflection device.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0008] In order to achieve specular reflection, the installation position of the metal reflector for reflecting the radio waves of the base station and delivering the radio waves to a dead zone (an area where communication is impossible) is limited. On the other hand, a normal reflectarray (metasurface reflector) can be reflected in a direction different from specular reflection (asymmetric reflection) by adjusting the pattern of the elements, and there is freedom in the installation position and angle when delivering radio waves to the dead zone.

[0009] However, the reflectarray (metasurface reflector) can increase the reflection intensity as the area is increased by connecting them. However, there is a problem that the directivity of the reflected wave increases and the reflection area becomes narrower, so radio waves cannot be delivered to a wide area with respect to the dead zone. Patent Documents 1, 3, and 4 do not disclose the recognition of the problem in this regard at all.

[0010] Furthermore, in a reflectarray having an element pattern, if a dimensional error occurs in the element pattern, the reflection phase in each region tends to change greatly from the designed value, and the reflection intensity in the desired direction may decrease. In addition, when it consists of a plurality of array groups, the design becomes complicated and it causes a decrease in the yield rate during manufacturing. Patent Document 2 discloses that two types of reflectors with different reflection angles are used in combination for the problem of narrowing, but the design becomes complicated and there is a risk of a decrease in the yield rate.

[0011] Therefore, an object of the present invention is to provide a reflectarray unit that can freely design the reflection angle, can deliver radio waves to a wide range of space (wide area), and has a high yield rate.

Means for Solving the Problems

[0012] To solve the above problems, one of the representative reflect array units of the present invention has a plurality of reflect arrays including element patterns, dielectric layers, and ground layers arranged in a plane. There is a unit space between the reflect arrays. The reflect array includes at least one reflection control region, and all the reflection control regions are the same in all the reflect arrays.

Advantages of the Invention

[0013] According to the present invention, it is possible to freely design the reflection angle, deliver radio waves to a wide range of space (wide area), and provide a reflect array unit with a high yield rate. Problems, configurations, and effects other than those described above will be clarified by the description in the following embodiments for implementation.

Brief Description of the Drawings

[0014]

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[0015] 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. When there are multiple components with the same or similar functions, they may be described using the same reference numeral with different subscripts. When there is no need to distinguish between these multiple components, the subscripts may be omitted. 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.

[0016] (Terminology explanation) In the present disclosure, a "reflectarray (electromagnetic wave reflector)" is a member that reflects electromagnetic waves and is capable of asymmetric reflection where the incident angle and the reflection angle are different. A "reflectarray unit (aggregate of electromagnetic wave reflectors)" is an aggregate of a plurality of reflectarrays, and is a member that mainly consists of asymmetric reflection where the incident angle and the reflection angle are different among the reflected waves of electromagnetic waves, and reflects electromagnetic waves in a plurality of directions. In the following description, an xyz coordinate system is applied, and it is assumed that a reflectarray is arranged on the xy plane (sometimes simply referred to as the "plane").

[0017] A "reflection control region" refers to a part of the region constituting the reflectarray. The reflection control region is the smallest region capable of reflecting the electromagnetic waves incident on that region in a predetermined direction. And the reflectarray is configured by combining one or more reflection control regions. When referring to the reflection control region, it shall include not only a two-dimensional region where the electromagnetic waves are in a direction parallel to the incident region, but also a layer structure formed in a direction perpendicular to the region. Also, a "unit cell" refers to a region obtained by dividing the reflection control region. One element pattern is included in the unit cell.

[0018] "θi" represents the incident angle of the incident wave. Let the incident angle in the x-axis direction be θix and the incident angle in the y-axis direction be θiy. Also, "θr" represents the reflection angle of the reflected wave. Let the reflection angle in the x-axis direction be θrx and the reflection angle in the y-axis direction be θry. Also, the angle θx in the x-axis direction is represented by a positive angle (from 0° to 180°) when it spreads in the direction from the +z-axis direction to the +x-axis direction, and is represented by a negative angle (from 0° to -180°) when it spreads in the direction from the +z-axis direction to the -x-axis direction. Similarly, the angle θy in the y-axis direction is represented by a positive angle (from 0° to 180°) when it spreads in the direction from the +z-axis direction to the +y-axis direction, and is represented by a negative angle (from 0° to -180°) when it spreads in the direction from the +z-axis direction to the -y-axis direction.

[0019] Regarding the element length of the 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. Regarding the element width, the element width in the x-axis direction is wx, and the element width in the y-axis direction is denoted as wy.

[0020] [First Embodiment] (Configuration of Reflect Array Unit) Referring to FIGS. 1 and 2, the configuration of the reflect array unit 30 according to the first embodiment will be described. FIG. 1 is a plan view showing an example of the configuration of the reflect array unit 30 according to the first embodiment. FIG. 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 in a plane and have 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.

[0021] More specifically, reflections with a radar 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 (described later), and the RCS of the reflection occurring at a peak angle different from the peak angle at which the RCS is the maximum value is within 10 dBsm of the maximum value. Thereby, even when the area of the blind zone is large, electromagnetic waves can be delivered to the entire area, and communication connection and communication speed can be stabilized.

[0022] The unit space 6 is preferably an air layer or a resin layer having a dielectric constant of 1 or more and 1.5 or less. If the unit space 6 is a conductive material, in addition to asymmetric reflection, specular reflection is mixed, which causes unnecessary multipath reflection.

[0023] (Configuration of Reflect Array) The reflectarray 20 is composed of one or more reflection control regions 5 formed by periodically arranging multiple element patterns 1 on a plane, and is capable of setting the direction of asymmetric reflection to a desired value (asymmetric reflection set to a desired value is sometimes referred to as a "reference asymmetric reflection"). The reflectarray 20 includes at least element patterns (elements) 1, a dielectric layer 2, and a ground layer (base plate) 3. The number of reflection control regions 5 included in the reflectarray 20 may be set appropriately depending on the desired reflection intensity, and FIG. 1 shows an example of a reflectarray 20 composed of three reflection control regions 5. Unless otherwise specified in this disclosure, the description will be given using a reflectarray 20 composed of three reflection control regions 5, but the configuration of the reflectarray 20 is not limited to this.

[0024] Next, the configuration of the reflectarray 20 will be described in more detail with reference to Fig. 3. Fig. 3 is a perspective view showing the configuration of the reflectarray 20. The reflectarray 20 in Fig. 3 generates a predetermined asymmetric reflection of electromagnetic waves along the x-axis. The reflectarray 20 in 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 reflectarray 20. The reflection control region 5 includes unit cells 41, 42, 43, ... 4 n(Hereinafter, when a unit cell is referred to without specifying it, it may be referred to as a "unit cell 4," where n is a positive integer of 2 or more.) The unit cells 4 are portions 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 and 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 lined up in the x-axis direction, and the reflectarray 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 lined up in the y-axis, or may include unit cells lined up in the x-axis and y-axis. The configuration of the reflection control region will be described later.

[0025] (Element pattern configuration) An element pattern is formed on the surface of the unit cell 4 facing the +z-axis direction. Using the division number n, unit cell 41, unit cell 42, ..., unit cell 4 n The element pattern 11 is formed in the unit cell 41. The element pattern 12 is formed in the unit cell 42. The element pattern 13 is formed in the unit cell 43. n Element pattern 1 n is formed. Furthermore, the element patterns are arranged at equal intervals within the reflection control area and between adjacent areas of the same reflection control area. Specifically, for each element pattern within reflection control area 5, if the size of the closest interval (hereinafter also referred to as "gap") between adjacent element patterns in the x-axis direction is gx, then within reflection control area 5, n In addition, element pattern 1 in reflection control area 5 is n and a reflection control region 5x (shown by a broken line, element pattern 1) adjacent to the reflection control region 5 in the x-axis direction. x Unit cell 4 in which 1 was formed x 1. Element pattern 1 xUnit cell 4 in which 2 is formed x 2, … element pattern 1 x n Unit cell 4 in which is formed x n including the element pattern 1 of (). x When the gap between 1 is Gx, in FIG. 3, Gx and gx are equal. Note that the element pattern of the reflection control region 5 and the reflection control region 5y (shown by a broken line, element pattern 1 y Unit cell 4 in which 1 is formed y 1, element pattern 1 y Unit cell 4 in which 2 is formed y 2, … element pattern 1 y n Unit cell 4 in which is formed y n including the gap between the element patterns of (). In FIG. 3, it is uniform and shown as Gy.

[0026] Within the reflection control region, each element pattern has a slightly different shape from other element patterns. Here, the shape of the element pattern from element pattern 11 to element pattern 1 n shown may be referred to as a cross patch. A cross patch refers to a shape in which two rectangular patches are orthogonal in the xy plane. Element pattern 11 has a rectangular patch with an element length lx1 which is the size in the x-axis direction and an element width wy1 which is the size in the y-axis direction, and a rectangular patch with an element length ly1 which is the size in the y-axis direction and an element width wx1 which is the size in the x-axis direction, having a shape in which they are orthogonal with the common position of the centers of gravity. Similarly, element pattern 1 n has a rectangular patch with an element length lxn and an element width wyn, and a rectangular patch with an element length lyn and an element width wxn, having a shape in which they are orthogonal with the common position of the centers of gravity. The method for setting the element length and element width will be described later.

[0027] (Explanation of each configuration, design method) (Layer configuration) The layer structure of the reflectarray 20 will be described with reference to Figures 4 and 5. Figures 4 and 5 are diagrams showing an example of the layer structure of the reflectarray 20. The reflectarray 20 has a structure 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, a three-layer structure consisting of the element pattern 1, the dielectric layer 2, and the ground layer 3 will be referred to as the "basic structure." In practice, the reflectarray 20 preferably has one or more layers having various functions (hereinafter also referred to as "functional layers") stacked on either the element pattern 1 side or the ground layer 3 side of the basic structure, or on both sides. In the following description, layers included in the reflectarray other than the element pattern 1, the dielectric layer 2, and the ground layer 3 will sometimes be referred to as "functional layers" when the type of layer is not specified.

[0028] 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. Also, a layer used for a purpose other than improving the adhesion may be formed. Note that intermediate products generated in the manufacturing process of the reflectarray 20 may be formed in layers and remain on the reflectarray 20.

[0029] Examples of functional layers include a design layer that is designed to take into consideration the landscape of the area where the reflect array 20 is installed, an installation layer that makes it easy to install the reflect array 20 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.

[0030] FIG. 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 fills the gaps between the plurality of element patterns 1, as in the reflectarray 20a (FIG. 4(a)), or such that the functional layer 7 is in contact with the upper surface of the element pattern 1 while maintaining the gaps between the plurality of element patterns 1, as in the reflectarray 20b (FIG. 4(b)), or such that the functional layer 7 is not in contact with the upper surface of the element pattern 1, as in the reflectarray 20c (FIG. 4(c)). When the reflectarrays 20a to 20c have a common configuration except for the functional layer 7, the reflectarrays 20a to 20c each have different reflection characteristics. Therefore, the characteristics of the reflectarray can be changed by changing the lamination method of the functional layer 7.

[0031] Fig. 5 is a diagram showing another example of the arrangement of functional layers. Fig. 5 shows an example of the arrangement of functional layers, including a protective layer 8, an adhesive layer 9, a design layer 10, and an installation layer 11. Fig. 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. Fig. 5(b) shows a reflectarray 20e in which an installation layer 11 is on the ground layer side via an adhesive layer 9, and a design layer 10 on the element pattern 1 side separated by an air gap.

[0032] (Reflection control area) The reflect array 20 includes at least one reflection control region. By changing the arrangement of the reflection control regions, the properties of the reflect array can be altered. For example, when electromagnetic waves of a certain wavelength are incident at a certain incident angle, by periodically arranging reflection control regions with a common reflection direction, the reflect array can be given the property of reflecting in a single direction. Also, when electromagnetic waves of a certain wavelength are incident at a certain incident angle, by configuring a reflect array that includes reflection control regions with different reflection directions, the property of scattering electromagnetic waves in multiple directions can also be given. Further, by configuring such that the reflection direction is shifted by a predetermined angle for each reflection control region, the property of concentrating electromagnetic waves at a specific location can also be given. At the design time, the frequency planned to be applied to the reflect array is hereinafter referred to as the "operating frequency".

[0033] The size Lx of the reflection control region in the x-axis direction is determined, for example, by Equation (1) when the wavelength of the operating frequency is λ, the x-axis component of the incident angle of the electromagnetic wave incident on the reflection control region is θix, and the x-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control region is θrx, and θix ≠ -θrx.

Equation

[0034] Also, the size Ly of the reflection control region in the y-axis direction is determined, for example, by Equation (2) when the y-axis component of the incident angle of the electromagnetic wave incident on the reflection control region is θiy, and the y-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control region is θry, and θiy ≠ -θry.

Equation

[0035] (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 examples of unit cell arrangements 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 reflectarray 20f and the direction of the electromagnetic wave (reflected wave) reflected from the reflectarray 20f. In other words, the thick solid arrows indicate the traveling direction of the wavefront, the arrow pointing toward the reflectarray 20f indicates the traveling direction of the wavefront of the incident wave, and the arrow pointing away from the reflectarray 20f indicates the traveling direction of the wavefront of the reflected wave. Also, FIG. 6(b) shows a plan view of the reflectarray 20f as seen from the z-axis direction. The relationships between (a) and (b) in FIGS. 7 and 8 are similar to those between (a) and (b) in FIG. 6.

[0036] The unit cells have the effect of reflecting incident electromagnetic waves with a predetermined phase difference. Because each unit cell in the reflection control region exhibits a different reflection phase, the wavefront of the reflected wave generated in the reflection control region 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, where the angle of incidence and the angle of reflection are equal.

[0037] When reflectarray 20f is to be caused to perform asymmetric reflection only along the x-axis direction (θix ≠ -θrx as shown in FIG. 6(a)), unit cells exhibiting different reflection phases along the x-axis direction are arranged in reflection control region 5a (FIG. 6(b)). Reflection control region 5a has three unit cells arranged along the x-axis direction, with the number of divisions n=3. The size Lx of reflection control region 5a in the x-axis direction is determined by equation (1), and the size of the unit cell in the x-axis direction is Lx / 3. When 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 equation (2) and can take any value. However, for ease of design, a square unit cell whose size is determined by Lx and the number of divisions n is used for convenience, and Ly is set equal to Lx / 3.

[0038] Similarly, when reflectarray 20g is intended to perform asymmetric reflection only along the y-axis direction (θiy ≠ -θry as shown in Figure 7(a)), unit cells exhibiting different reflection phases are arranged along the y-axis direction in reflection control region 5b (Figure 7(b)). Here, m (m is a positive integer greater than or equal to 2) is the number of divisions when dividing the reflection control region into unit cells in the y-axis direction. 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 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. Because the x-axis component of the reflection angle is symmetric reflection, Lx does not need to be determined by equation (1) and can take any value. However, for ease of design, a square unit cell whose size is determined by Ly and the number of divisions m is used for convenience, and Lx is set equal to Ly / 3.

[0039] FIG. 8(a) shows the relationship between the reflectarray 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 attempting to cause the reflectarray 20h to perform asymmetric reflection in either the x-axis direction or the y-axis direction (θix≠-θrx as shown in FIG. 8(a1) and θiy≠-θry as shown in FIG. 8(a2)), within the reflection control region 5c, unit cells with different reflection phases are arranged in the x-axis direction, 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 with 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 in the x-axis direction n = 3 and the number of divisions in the y-axis direction m = 3. The size Lx of the reflection control region 5c in the x-axis direction is determined by Equation (1), and the size Ly in the y-axis direction is determined by Equation (2). The size of the unit cell in the x-axis direction is determined from Lx and n and is Lx / 3. The size of the unit cell in the y-axis direction is determined from Ly and m and is Ly / 3. Both the x-axis component and the y-axis component of the incident wave are asymmetrically reflected. For this reason, the x-axis component of the propagation direction of the reflected wavefront is different from the x-axis component of the propagation direction of the incident wavefront, and the y-axis component of the propagation direction of the reflected wavefront is different from the y-axis component of the propagation direction of the incident wavefront (FIG. 8(a)). Note that gx indicates the gap in the x-axis direction between the element patterns within the region of the reflection control region 5c. gy indicates the gap in the y-axis direction between the element patterns within the region of the reflection control region 5c. The intervals gx between the element patterns in the x-axis direction are equal, and the intervals gy between the element patterns in the y-axis direction are equal. Although cases where gx and gy are different are shown, gx and gy may also be equal. Further, Gx represents the gap between the element pattern of the reflection control region 5c and the element pattern of the reflection control region adjacent to the reflection control region 5c in the x-axis direction. Gy represents the gap between the element pattern of the reflection control region 5c and the element pattern of the reflection control region adjacent to the reflection control region 5c in the y-axis direction. When a reflection control region identical to the reflection control region 5c is adjacent in the y-axis direction (or x-axis direction) without changing its position in the x-axis direction (or y-axis direction), gx and Gx are equal, and gy and Gy are equal.

[0040] (Distribution of reflection phase and distribution of surface impedance within the reflection control region) The distribution of the reflection phase within the reflection control region is determined, for example, in accordance with Expressions (3) and (4). Here, let the wavelength of the operating frequency be λ (m), the x-axis component of the incident angle of the electromagnetic wave incident on the reflection control region be θix, the y-axis component be θiy, the x-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control region be θrx, the y-axis component be θry, the reflection phases at arbitrary coordinates x1 and x2 parallel to the x-axis within the reflection control region be φx1 and φx2 respectively, the distance between the coordinates x1 and x2 be dx, and the reflection phase difference between Φx1 and Φx2 be ΔΦx. Also, let the reflection phases at arbitrary coordinates y1 and y2 parallel to the y-axis be φy1 and φy2 respectively. When attempting to cause asymmetric reflection along the x-axis direction in the reflection control region, it is preferable to satisfy Expression (3). When attempting to cause asymmetric reflection along the y-axis direction in the reflection control region, it is preferable to satisfy Expression (4). Also, when attempting to cause asymmetric reflection in both the x-axis direction and the y-axis direction in the reflection control region, it is preferable to satisfy either Expression (3) or Expression (4). [Number] [Number]

[0041] Further, instead of the reflection phase, the distribution of the surface impedance can also be applied within the reflection control region. In that case, the distribution of the surface impedance is represented by, for example, Equation (5) and Equation (6). Here, Zsx is the surface impedance distribution parallel to the x-axis direction of the reflection control region, Zsy is the surface impedance distribution parallel to the y-axis direction of the reflection control region, and η1 is the impedance of the incident wave. Also, let the x-axis component of the incident angle of the electromagnetic wave incident on the reflection control region be θix, the y-axis component be θiy, the x-axis component of the reflection angle of the electromagnetic wave reflected from the reflection control region be θrx, and the y-axis component be θry. Note that x1 and x2 indicate the x-coordinates as relative coordinates within the reflection control region, and the reference x = 0 can be taken at any coordinate in the reflection control region. Similarly, y1 and y2 indicate the y-coordinates as relative coordinates within the reflection control region, and the reference y = 0 can be taken at any coordinate in the reflection control region. Also, k1 is the wave number of the reflected wave. j represents the imaginary unit. When attempting to cause asymmetric reflection along the x-axis direction in the reflection control region, it is preferable to satisfy Equation (5). When attempting to cause asymmetric reflection along the y-axis direction in the reflection control region, it is preferable to satisfy Equation (6). Also, when attempting to cause asymmetric reflection in both the x-axis direction and the y-axis direction in the reflection control region, it is preferable to satisfy either Equation (5) or Equation (6). [Number] [Number]

[0042] As other distributions of the surface impedance, they are represented by, for example, Equation (7) and Equation (8). When attempting to cause asymmetric reflection only along the x-axis direction in the reflection control region, it is preferable to satisfy Equation (7). When attempting to cause asymmetric reflection only along the y-axis direction in the reflection control region, it is preferable to satisfy Equation (8). Also, when attempting to cause asymmetric reflection in both the x-axis direction and the y-axis direction in the reflection control region, it is preferable to satisfy Equation (7) and Equation (8) simultaneously.

Number

Number

[0043] Note that, from the above formula (3) to formula (8), it shows an example of the design formula used when designing the distribution of the reflection phase and the distribution of the surface impedance. The present disclosure is not limited to the case of using these formulas (3) to (8), and other design formulas can be appropriately selected.

[0044] [Second Embodiment] Referring to FIGS. 9 and 10, the configuration of the reflectarray unit 30 according to the second embodiment will be described. FIG. 9 is a plan view showing an example of the configuration of the reflectarray unit 30 according to the second embodiment. FIG. 10 is a cross-sectional view showing an example of the configuration of the reflectarray unit 30 according to the second embodiment. It is different from the first embodiment in that a plurality of reflectarrays 20 are arranged on the support 12 with the unit space 6 interposed therebetween to form the reflectarray unit 30, and since the other configurations are the same, detailed description is omitted. The support 12 is made of a dielectric such as resin, and a medium having a dielectric constant close to that of air (dielectric constant 1) is preferable. And the hardness of the support may be appropriately adjusted according to the place where the reflectarray unit is installed. If the support is set to a standard size of a predetermined size, it can be easily transported and attached to a wide range of members such as indoor and outdoor building materials, roads, and communication equipment.

[0045] <Example> FIG. 11 is a schematic diagram showing an installation example of a reflect array in the prior art. And FIG. 12 is a schematic diagram showing an installation example of a reflect array in an embodiment of the present invention. The incident wave transmitted from the base station 31 can be asymmetrically reflected by the reflect array unit 30 and reach the radio wave region 34 in the dead zone 33 generated by the radio wave shielding object 32. In the prior art, the radio wave region 34 is narrowed (FIG. 11), whereas when the reflect array 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 dead zones than in the prior art.

[0046] The simulations in the examples and comparative examples were performed by the finite element method, and the calculations were performed assuming that the reflect array unit was irradiated with a plane wave. In the actual environment, the base station and the reflect array unit may be appropriately installed in consideration of the distance between the base station and the reflect array unit so that the reflect array unit is irradiated with a plane wave. Similarly, for the distance between the reflect array unit and the dead zone, each may be appropriately installed so that the reflected wave of the reflect array unit becomes a plane wave. The distance to become a plane wave may be based on the far-field distance. For example, when the reflect array unit is square, for the length d of one side of the reflect array unit parallel to the plane formed by the incident wave of the base station and the normal of the reflect array unit, and the wavelength λ, the far-field distance x = 2d 2 / λ. As a specific example, in the case of a reflect array unit with d = 0.3 m and a base station with a frequency of 4.6 GHz, the distance between the reflect array unit and the base station and the dead zone may be 2.76 m or more. However, the above example is for reference, and the effects of the present invention are not necessarily not obtained just because the distance between the reflect array unit and the base station or the dead zone is shorter than the far-field distance.

[0047] Examples and comparative examples will be described below. (Comparative Example 1) First, a reflect array unit targeted in the examples is configured, and Comparative Example 1 regarding a reflect array (hereinafter referred to as "unit reflect array") which is a unit when spaced apart and arranged will be described. Table 1 is configuration data of the unit reflect array according to Comparative Example 1. Also, FIG. 13 is a plan view of the unit reflect array according to Comparative Example 1 and a diagram showing reflection characteristics. FIG. 13(a) is a plan view, and FIG. 13(b) is reflection characteristics. Note that the cross-section of the unit reflect array according to Comparative Example 1 is the same as the cross-sectional view of the reflect array 20 in FIG. 2. In the following description, the reference numerals of the same parts are omitted.

Table 1

[0048] The operating frequency was set to 27.2 GHz, the target reflection characteristics (desired reflection characteristics) were set to θix = 33°, θrx = 0°, θiy = 0°, θry = 0°, and the size Lx in the x-axis direction of the reflection control region 5 was determined to be 20.238 mm by using Equation (1).

[0049] The number of divisions of the reflection control region 5 was set to 3, and the sizes in the x-axis direction and y-axis direction of the unit cell were set to 6.746 mm. The shape of the element pattern was a cross patch in which two square patches were orthogonal in the xy plane. Here, it was assumed that only the element width differed in each element pattern within the reflection control region 5. Specifically, the element lengths were lx₁ = lx₂ = lx₃ = ly₁ = ly₂ = ly₃ = 3.25 mm, and the element widths within the same element pattern were wx₁ = wy₁, wx₂ = wy₂, wx₃ = wy₃. The reflection phase of the unit cell with respect to the element width w was analyzed using HFSS. In the unit cell p, let the element length in the x-axis direction be lxp, the element length in the y-axis direction be lyp, the element width in the x-axis direction be wxp, and the element width in the y-axis direction be wyp. However, when lxp and lyp are equal, the subscripts x and y can be omitted; when wxp and wyp are equal, the subscripts x and y can be omitted; and when the unit cell is not specified, the subscript p may be omitted.

[0050] Next, based on the analysis results of the unit cell, the element width w in each unit cell was determined to follow 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, respectively.

[0051] As shown in FIG. 13(a), the reflectarray 20 has the same reflection control regions 5 arranged in 1×3 in the x-axis direction and 1×3 in the y-axis direction (as a result, the unit cells are arranged in 3×3 in the x-axis direction and 3×3 in the y-axis direction), and thus the size in the xy plane is 20.238 mm square. The reflection characteristics when the reflectarray 20 is irradiated with a polarized wave parallel to the x-axis at θix = 33° and θiy = 0° were analyzed using HFSS.

[0052] FIG. 13(b) is a diagram showing the reflection characteristics of the unit reflectarray 20 according to Comparative Example 1. The horizontal axis represents the reflection angle θry, and the vertical axis represents the RCS (radar cross section). The RCS is a value substantially corresponding to the intensity of the reflected wave. The electromagnetic wave incident at θix = 33° was reflected at a maximum value in the desired direction of θrx = 0° (reference asymmetric reflection direction), and the RCS was -19.12 dBsm.

[0053] In evaluating the reflection characteristics of the following examples and comparative examples, as described above, it is determined to be qualified if reflections with an RCS of -15 dBsm or more can be obtained at any two or more angles excluding the range of ±1° of the reference asymmetric reflection, and the RCS of the reflections occurring at a peak angle different from the peak angle at which the RCS becomes the maximum value is within 10 dBsm of the maximum value. If the reflection characteristics meet the passing criteria, reflected light having a peak of a predetermined intensity is generated in directions other than the reference asymmetric reflection direction, and it becomes possible to widen the radio wave region 34 with sufficient intensity as a whole. In Comparative Example 1, since the peak intensity value of the reference asymmetric reflection direction where the RCS is maximum does not reach -15 dBsm in the first place, it fails.

[0054] (Comparative Example 2) FIG. 14 is a plan view of the reflectarray according to Comparative Example 2 and a diagram showing the reflection characteristics. FIG. 14(a) is a plan view, and FIG. 14(b) is the reflection characteristics. As shown in FIG. 14(a), Comparative Example 2 is the same as Comparative Example 1 except that it has a configuration in which two 2×2 unit reflectarrays 20 are laid out. When analyzed using HFSS, as shown in FIG. 14(b), the electromagnetic wave incident at θix = 33° is reflected at the maximum value in the desired θrx = 0° direction (reference asymmetric reflection direction), and its RCS is -6.97 dBsm. In Comparative Example 2, reflected light having a peak at an angle different from the reference asymmetric reflection direction is generated (-18.01 dBsm at -25°), but since the difference from the maximum value is greater than 10 dBsm, it fails.

[0055] (Comparative Example 3) FIG. 15 is a plan view of the reflectarray according to Comparative Example 3 and a diagram showing the reflection characteristics. FIG. 15(a) is a plan view, and FIG. 15(b) is the reflection characteristics. As shown in FIG. 15(a), Comparative Example 3 is the same as Comparative Example 1 except that it has a configuration in which three 3×3 unit reflectarrays 20 are laid out. When analyzed using HFSS, as shown in FIG. 15(b), the electromagnetic wave incident at θix = 33° is reflected at the maximum value in the desired θrx = 0° direction (reference asymmetric reflection direction), and its RCS is 0.26 dBsm. In Comparative Example 3, reflected light having a peak at an angle different from the reference asymmetric reflection direction is generated (-12.26 dBsm at -15°, -13.01 dBsm at 15°), and in both cases, since the difference from the maximum value is greater than 10 dBsm, it fails.

[0056] Next, examples related to the reflectarray unit will be described. In the following description, the length of the unit space between the reflect arrays means the average distance of the gaps generated between adjacent reflect arrays arranged at intervals. (Example 1) FIG. 16 is a plan view of a reflect array unit according to Example 1 and a diagram showing reflection characteristics. FIG. 16(a) is a plan view, and FIG. 16(b) is the reflection characteristics. As shown in FIG. 16(a), the reflect array unit 30 according to Example 1 is composed of an aggregate of unit reflect arrays arranged with a unit space for 0.5 unit reflect arrays open with respect to the reflect array of Comparative Example 2 in which 2×2 unit reflect arrays 20 are laid out. The length of the unit space between each unit reflect array 20 is 10.119 mm, and the length of one side of the outer shape of the reflect array unit 30 is 50.595 mm. The incident light irradiated on the reflect array unit 30 with a plane wave is partially transmitted through the unit space portion. However, when analyzed using HFSS, as shown in FIG. 16(b), the electromagnetic wave incident at θix = 33° showed a reflection characteristic of being divided into two reflected lights from the reflected light in the reference asymmetric reflection direction of θrx = 0°.

[0057] As shown in FIG. 16(b), the peaks of the two reflected lights are observed at RCS of -8.39 dBsm at -9° and -8.59 dBsm at 9°. Therefore, it is considered qualified because there are two or more reflected lights having a peak intensity with an RCS of -15 dBsm or more at angles excluding the range of ±1° in the reference asymmetric reflection direction, and the difference between the maximum value and the RCS of the others is within 10 dBsm.

[0058] (Example 2) FIG. 17 is a plan view of a reflect array unit according to Example 2 and a diagram showing reflection characteristics. FIG. 17(a) is a plan view, and FIG. 17(b) is the reflection characteristics. As shown in Fig. 17(a), the reflect array unit 30 according to Example 2 is composed of an aggregate of unit reflect arrays arranged with a unit space for 0.75 unit reflect arrays left open with respect to the reflect array of Comparative Example 2 in which 2×2 unit reflect arrays 20 are laid out. The length of the unit space between each unit reflect array 20 is 15.1785 mm, and the length of one side of the outer shape of the reflect array unit 30 is 55.6545 mm. Some of the incident light irradiated on the reflect array unit 30 with a plane wave passes through the unit space portion. However, when analyzed using HFSS, as shown in Fig. 17(b), the electromagnetic wave incident at θix = 33° exhibited a reflection characteristic of being divided into three reflected lights from the reflected light in the reference asymmetric reflection direction of θrx = 0°. As a characteristic, a behavior between the reflection characteristic of Example 1 (Fig. 16(b)) and the reflection characteristic of Example 3 (Fig. 18(b)) described later can be seen.

[0059] As shown in Fig. 17(b), the peaks of the three reflected lights are observed at RCS of -9.14 dBsm at -12°, -7.26 dBsm at 4°, and -14.63 dBsm at 20°. Therefore, at angles excluding the range of ±1 degree in the reference asymmetric reflection direction, there are two or more reflected lights having a peak intensity with an RCS of -15 dBsm or more, and since the difference between the maximum value and the RCS of the others is within 10 dBsm, it is considered qualified.

[0060] (Example 3) Fig. 18 is a plan view and a diagram showing the reflection characteristic of the reflect array unit according to Example 3. Fig. 18(a) is a plan view, and Fig. 18(b) is a reflection characteristic. As shown in Fig. 18(a), the reflect array unit 30 according to Example 3 is composed of an aggregate of unit reflect arrays arranged with a unit space for 1 unit reflect array left open with respect to the reflect array of Comparative Example 2 in which 2×2 unit reflect arrays 20 are laid out. The length of the unit space between each unit reflect array 20 is 20.238 mm, and the length of one side of the outer shape of the reflect array unit 30 is 60.714 mm. The incident light irradiated on the reflectarray unit 30 by the plane wave partially transmits through the unit space part. However, when analyzed using HFSS, as shown in Fig. 18(b), the electromagnetic wave incident at θix = 33° exhibits a reflection characteristic of being divided into three reflected lights from the reflected light in the reference asymmetric reflection direction of θrx = 0°. In particular, when compared with Comparative Example 3 having the same side length of the outer shape and no unit space, the influence of the presence of the unit space on the broadening of the reflection characteristic was remarkably shown.

[0061] As shown in Fig. 18(b), the peaks of the three reflected lights are observed at -9.81 dBsm of RCS at -15°, -6.80 dBsm at 0°, and -10.58 dBsm at 14°. Therefore, at angles excluding the range of ±1° in the reference asymmetric reflection direction, there are two or more reflected lights having a peak intensity with an RCS of -15 dBsm or more, and since the difference between the maximum value and the RCS of the others is within 10 dBsm, it is considered qualified.

[0062] (Example 4) Fig. 19 is a plan view and a diagram showing the reflection characteristic of the reflectarray unit according to Example 4. Fig. 19(a) is a plan view, and Fig. 19(b) is the reflection characteristic. As shown in Fig. 19(a), the reflectarray unit 30 according to Example 4 is composed of an aggregate of unit reflectarrays arranged with a unit space for 1.5 unit reflectarrays open with respect to the reflectarray of Comparative Example 2 in which two by two unit reflectarrays 20 are laid out. The length of the unit space between each unit reflectarray 20 is 30.357 mm, and the length of one side of the outer shape of the reflectarray unit 30 is 70.833 mm. The incident light irradiated on the reflectarray unit 30 by the plane wave partially transmits through the unit space part. However, when analyzed using HFSS, as shown in Fig. 19(b), the electromagnetic wave incident at θix = 33° exhibits a reflection characteristic of being divided into four reflected lights from the reflected light in the reference asymmetric reflection direction of θrx = 0°. Note that the behavior is between the reflection characteristic of Example 3 (Fig. 18(b)) and the reflection characteristic of Example 5 (Fig. 20(b)) described later.

[0063] As shown in FIG. 19(b), the peaks of the four reflected lights are found at -11.43 dBsm of RCS at -18°, -7.49 dBsm at -6°, -7.59 dBsm at 6°, and -12.53 dBsm at 18°. Therefore, at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, there are two or more reflected lights having a peak intensity with an RCS of -15 dBsm or more, and since the difference between the maximum value and the RCS of the others is within 10 dBsm, it is considered qualified.

[0064] (Example 5) FIG. 20 is a plan view and a diagram showing reflection characteristics of a reflect array unit according to Example 5. FIG. 20(a) is a plan view, and FIG. 20(b) is the reflection characteristics. As shown in FIG. 20(a), the reflect array unit 30 according to Example 5 is composed of an aggregate of unit reflect arrays arranged with a unit space for two unit reflect arrays left open with respect to the reflect array of Comparative Example 2 in which two by two unit reflect arrays 20 are laid out. The length of the unit space between each unit reflect array 20 is 40.476 mm, and the length of one side of the outer shape of the reflect array unit 30 is 80.952 mm. The incident light irradiated on the reflect array unit 30 with a plane wave may pass through the unit space portion, but when analyzed using HFSS, as shown in FIG. 20(b), the electromagnetic wave incident at θix = 33° showed a reflection characteristic of being divided into five reflected lights from the reflected light at θrx = 0°, which is the reference asymmetric reflection direction.

[0065] As shown in FIG. 20(b), the peaks of the five reflected lights are found at -13.04 dBsm of RCS at -21°, -8.48 dBsm at -10°, -7.00 dBsm at 0°, -8.59 dBsm at 10°, and -14.21 dBsm at 20°. Therefore, at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, there are two or more reflected lights having a peak intensity with an RCS of -15 dBsm or more, and since the difference between the maximum value and the RCS of the others is within 10 dBsm, it is considered qualified.

[0066] (Example 6) FIG. 21 is a plan view of the reflect array unit according to Example 6 and a diagram showing reflection characteristics. FIG. 21(a) is a plan view, and FIG. 21(b) is the reflection characteristics. As shown in FIG. 21(a), the reflect array unit 30 according to Example 6 has a configuration in which a unit reflect array is added to the center of the reflect array unit according to Example 3 configured with a unit space for one unit reflect array left open. The incident light irradiated on the reflect array unit 30 by a plane wave may transmit through the unit space portion. However, when analyzed using HFSS, as shown in FIG. 21(b), the reflection directions (peak angles) indicating the peak intensities of the reflected light divided into three were almost the same as those in the case of Example 3. On the other hand, the RCS at 0° was larger than the value of Example 3, and it is presumed that the reflection from the central unit reflect array contributed.

[0067] As shown in FIG. 21(b), the peaks of the three reflected lights are found at an RCS of -12.35 dBsm at -15°, -4.87 dBsm at 0°, and -13.11 dBsm at 15°. Therefore, it meets the requirements because there are two or more reflected lights having a peak intensity with an 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 RCS of the others is within 10 dBsm.

[0068] (Example 7) FIG. 22 is a plan view of the reflect array unit according to Example 7 and a diagram showing reflection characteristics. FIG. 22(a) is a plan view, and FIG. 22(b) is the reflection characteristics. As shown in FIG. 22(a), the reflect array unit 30 according to Example 7 has a configuration in which a unit reflect array is added to the center of the reflect array unit according to Example 4 configured with a unit space for 1.5 unit reflect arrays left open. The incident light irradiated on the reflectarray unit 30 by a plane wave may be transmitted through the unit space portion. However, when analyzed using HFSS, as shown in Fig. 22(b), the reflection directions (peak angles) indicating the peak intensities of the four divided reflected lights were almost the same as those 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.

[0069] As shown in Fig. 22(b), the peaks of the four reflected lights are found at -18° with an RCS of -14.11 dBsm, -6° with -5.53 dBsm, 6° with -10.15 dBsm, and 18° with -10.55 dBsm. Therefore, at angles excluding the range of ±1 degree from the reference asymmetric reflection direction, there are two or more reflected lights having a peak intensity with an RCS of -15 dBsm or more, and since the difference between the maximum value and the RCS of the others is within 10 dBsm, it is considered qualified.

[0070] (Example 8) Fig. 23 is a plan view of the reflectarray unit according to Example 8 and a diagram showing the reflection characteristics. Fig. 23(a) is the plan view, and Fig. 23(b) is the reflection characteristics. As shown in Fig. 23(a), the reflectarray unit 30 according to Example 8 has a configuration in which a unit reflectarray is added to the center of the reflectarray unit according to Example 5, with a unit space for two unit reflectarrays left open. The incident light irradiated on the reflectarray unit 30 by a plane wave may be transmitted through the unit space portion. However, when analyzed using HFSS, as shown in Fig. 23(b), the reflection directions (peak angles) indicating the peak intensities of the five divided reflected lights were almost the same as those in Example 5. On the other hand, the RCS near 0°, ±20° decreased compared to the value in Example 5, and the RCS near ±10° tended to increase compared to the value in Example 5.

[0071] As shown in Fig. 23(b), the peaks of the five reflected lights are found at an RCS of -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, at angles excluding the range of ±1° from the reference asymmetric reflection direction, there are two or more reflected lights having a peak intensity with an RCS of -15 dBsm or more, and since the difference between the maximum value and the RCS of the others is within 10 dBsm, it is considered qualified.

[0072] (Example 9) Fig. 24 is a plan view and a diagram showing the reflection characteristics of the reflector array unit according to Example 9. Fig. 24(a) is a plan view, and Fig. 24(b) is the reflection characteristics. As shown in Fig. 24(a), the reflector array unit 30 according to Example 9 has an increased number of reflector arrays while leaving a unit space for one unit reflector array, and the reflector array unit according to Example 3 that leaves a unit space for one unit reflector array is arranged in the center, and further reflector arrays are arranged at the four corners extended with a unit space for one unit reflector array along the diagonal. The length of one side of the outer shape of the reflector array unit 30 in this example is 141.666 mm. The incident light irradiated on the reflector array unit 30 with a plane wave partially transmits through the unit space portion. However, when analyzed using HFSS, as shown in Fig. 24(b), the reflection directions (peak angles) showing the peak intensities of the three divided reflected lights were almost the same as those in the case of Example 3. On the other hand, the RCS at each peak angle showed a tendency to increase compared to the value of Example 3.

[0073] As shown in Fig. 24(b), the peaks of the three reflected lights are found at an RCS of -4.18 dBsm at -16°, -0.78 dBsm at 0°, and -5.00 dBsm at 16°. Therefore, at angles excluding the range of ±1° from the reference asymmetric reflection direction, there are two or more reflected lights having a peak intensity with an RCS of -15 dBsm or more, and since the difference between the maximum value and the RCS of the others is within 10 dBsm, it is considered qualified.

[0074] (Example 10) FIG. 25 is a plan view of a reflect array unit according to Example 10 and a diagram showing reflection characteristics. FIG. 25(a) is a plan view, and FIG. 25(b) is the reflection characteristics. As shown in FIG. 25(a), the reflect array unit 30 according to Example 10 is obtained by increasing the number of reflect arrays while leaving a unit space for one unit reflect array in the same manner as in Example 9. For the reflect array unit according to Example 9, a configuration is adopted in which two unit reflect arrays are added to each of the four outer sides with a unit space for one unit reflect array left. The length of one side of the outer diameter of the reflect array unit 30 of this example is 141.666 mm. The incident light irradiated on the reflect array unit 30 by a plane wave may pass through the unit space portion. However, when analyzed using HFSS, as shown in FIG. 24(b), the reflection directions (peak angles) indicating the peak intensities of the reflected light divided into three were almost the same as those in Examples 3 and 9. On the other hand, the RCS at each peak angle tended to increase compared to the values in Examples 3 and 9.

[0075] As shown in FIG. 24(b), the peaks of the three reflected lights are found at an RCS of 2.03 dBsm at -16°, 5.33 dBsm at 0°, and 0.99 dBsm at 16°. Therefore, there are two or more reflected lights having a peak intensity with an RCS of -15 dBsm or more at angles excluding the range of ±1 degree in the reference asymmetric reflection direction, and since the difference between the maximum value and the RCS of the others is within 10 dBsm, it is considered qualified.

[0076] (Example 11) FIG. 26 is a plan view of a reflect array unit according to Example 11 and a diagram showing reflection characteristics. FIG. 26(a) is a plan view, and FIG. 26(b) is the reflection characteristics. 26(a), the reflectarray unit 30 according to Example 11 has a configuration in which the reflectarray unit according to Example 3, which is placed in the center, is removed from the reflectarray unit according to 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 onto 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 separated into reflected lights with significant peak intensities as in Examples 3, 9, and 10.

[0077] As shown in Figure 26(b), the three peaks of reflected light corresponding to Examples 3, 9, and 10 are found at an RCS of -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, the test passes.

[0078] Example 12 27A and 27B are diagrams showing 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 reflectarray unit 30 of Example 12 is configured by combining and arranging two reflectarray units of Example 1, which are spaced apart by a unit space of 0.5 unit reflectarrays, in the second and fourth quadrants of the xy plane, and two reflectarray units of Example 3, which are spaced apart by a unit space of one unit reflectarray, in the first and third quadrants of the xy plane, so that there is a unit space of one unit reflectarray between them. Although some of the incident light irradiated on the reflectarray unit 30 with a plane wave passes through the unit space portion, when analyzed using HFSS, as shown in Fig. 27(b), the reflection characteristics were found to be a superposition of the reflection characteristics of Example 1 and Example 3.

[0079] As shown in Fig. 27(b), the peaks of the three reflected lights corresponding to Examples 3, 9, and 10 are found at -15° with an RCS of 0.52 dBsm, 0° with -0.68 dBsm, and 14° with -0.14 dBsm. Therefore, at angles excluding the range of ±1° from the reference asymmetric reflection direction, there are two or more reflected lights having a peak intensity with an RCS of -15 dBsm or more, and since the difference between the maximum value and the RCS of the others is within 10 dBsm, it is considered qualified.

[0080] Examples of the second embodiment provided with the support 12 will be described below. (Example 13) Fig. 28 is a plan view, a cross-sectional view, and a view showing the reflection characteristics of the reflectarray 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. As shown in Fig. 28(a-1)(a-2), the reflectarray unit 30 according to Example 13 has a configuration in which the reflectarray unit of Example 3 with a unit space for one unit reflectarray is arranged on the support 12. The support 12 is a styrofoam made of polystyrene, with a thickness of 30 mm, a dielectric constant ε' = 1.02, and tanδ = 0. The configuration other than the support is the same as that of Example 3. Although some of the incident light irradiated on the reflectarray unit 30 with a plane wave passes through the unit space portion and the support, when analyzed using HFSS, as shown in Fig. 28(b), the reflection characteristics such as the reflection direction (peak angle) and RCS indicating the peak intensities of the three separated reflected lights were almost the same as those in the case of Example 3.

[0081] As shown in Fig. 28(b), the peaks of the three reflected lights are found at -9.71 dBsm of RCS at -15°, -6.41 dBsm at 0°, and -10.39 dBsm at 14°. Therefore, at angles excluding the range of ±1° from the reference asymmetric reflection direction, there are two or more reflected lights having a peak intensity with an RCS of -15 dBsm or more, and since the difference between the maximum value and the RCS of the others is within 10 dBsm, it is considered qualified.

[0082] (Example 14) Fig. 29 is a plan view, a cross-sectional view, and a view showing the reflection characteristics of the 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. As shown in Fig. 29(a-1) and (a-2), the reflect array unit 30 according to Example 14 has a configuration in which the reflect array unit of Example 3 with a unit space for one unit reflect array is arranged on the 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 tanδ = 0. The configuration other than the support is the same as that of Example 3. The incident light irradiated on the reflect array unit 30 by a plane wave partially passes through the unit space portion and the support. However, when analyzed using HFSS, as shown in Fig. 29(b), the reflection directions (peak angles) showing the peak intensities of the three divided reflected lights were almost the same as those in the case of Example 3, but overall, there was a tendency for the reflection to dissipate, such as a decrease in the peak intensity in the reference asymmetric reflection direction (0°) and an increase in the RCS in the specular reflection direction (33°).

[0083] As shown in Fig. 29(b), the peaks of the three reflected lights are found at -6.91 dBsm of RCS at -15°, -7.42 dBsm at -1°, and -11.51 dBsm at 14°. Therefore, at angles excluding the range of ±1° from the reference asymmetric reflection direction, there are two or more reflected lights having a peak intensity with an RCS of -15 dBsm or more, and since the difference between the maximum value and the RCS of the others is within 10 dBsm, it is considered qualified.

[0084] (Example 15) FIG. 30 is a plan view, a cross-sectional view, and a view showing reflection characteristics of the reflectarray 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. As shown in FIGS. 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 with a unit space for one unit reflectarray is arranged on a support 12. The support 12 is a styrofoam made of polystyrene, having 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. The incident light irradiated on the reflectarray unit 30 with a plane wave partially passes through the unit space portion and the support. However, when analyzed using HFSS, as shown in FIG. 30(b), the reflection characteristics such as the reflection direction (peak angle) and RCS indicating the peak intensity of the reflected light divided into three are almost the same as those in the case of Example 3.

[0085] As shown in FIG. 30(b), the peaks of the three reflected lights are found at -15° with an RCS of -9.48 dBsm, 0° with -6.39 dBsm, and 14° with -10.57 dBsm. Therefore, it is considered qualified because there are two or more reflected lights having a peak intensity with an RCS of -15 dBsm or more at angles excluding the range of ±1° from the reference asymmetric reflection direction, and the difference between the maximum value and the RCS of the others is within 10 dBsm.

[0086] (Example 16) FIG. 31 is a plan view, a cross-sectional view, and a view showing reflection characteristics of the reflectarray 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. As shown in FIGS. 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 with a unit space for one unit reflectarray is arranged on a support 12. The support 12 is an acrylic plate made of acrylic, having 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 in Example 3. The incident light irradiated on the reflectarray unit 30 by the plane wave may pass through the unit space portion and the support. However, when analyzed using HFSS, as shown in Fig. 31(b), the reflection directions (peak angles) indicating the peak intensities of the three split reflected lights were almost the same as those in Example 3. However, the peak intensity in the reference asymmetric reflection direction (0°) decreased, and the RCS in the specular reflection direction (33°) increased, showing a tendency for the reflection to dissipate overall.

[0087] As shown in Fig. 31(b), the peaks of the three reflected lights are observed at -9.49 dBsm for the RCS at -15°, -5.99 dBsm at -1°, and -9.91 dBsm at 14°. Therefore, at angles excluding the range of ±1 degree in the reference asymmetric reflection direction, there are two or more reflected lights having a peak intensity with an RCS of -15 dBsm or more, and since the difference between the maximum value and the RCS of the others is within 10 dBsm, it is considered qualified.

[0088] (Discussion) In the above embodiments, when referring to the unit space for p reflectarray units, it actually means p times the length of the reflection control region included in the reflectarray (however, the length of the reflection control region means the length (Lx) in the direction in which a plurality of unit cells included in the reflection control region are arranged). Therefore, according to the results of the embodiments, for a reflectarray unit in which the length of the unit space is 0.75 (3 / 4) of the length of the reflection control region, reflected lights having sufficient peak intensities are generated so as to split before and after the reflection angle in the reference asymmetric reflection direction, and wide area coverage is realized. Therefore, the same effect can be achieved if it is at least 1 / 3 or more of the length of the reflection control region. And as the length of the unit space increases, the number of reflected lights splitting before and after the reference asymmetric reflection direction tends to increase, making it possible to deliver the reflected wave to a wider area.

[0089] Particularly, when the length of the unit space is n times (n is a natural number) the length of the reflection control region, reflected lights having peak intensities in the same direction as the reference asymmetric reflection direction are generated, making the design easier and 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 with a peak intensity does not occur in the reference asymmetric reflection direction, and reflected light with approximately the same peak intensity tends to occur at angles before and after that (Examples 1 and 4).

[0090] 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 the square arrangement, the peak intensity in the reference asymmetric reflection direction may increase (Example 6).

[0091] 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).

[0092] The reflection characteristics of a reflectarray unit configured by mixing and arranging reflectarray units with unit space lengths of different lengths is a superposition of the reflection characteristics of each of the constituent reflectarrays (Example 12).

[0093] In the case of a reflectarray unit equipped with a support, if the dielectric constant of the support is a high value of about 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 specular reflection direction to increase, resulting in an overall tendency for reflection to dissipate, so the dielectric constant is preferably between 1 and 1.5 (Examples 13 to 16). Furthermore, any dielectric such as resin with a dielectric constant within this range can be used as the material to fill the unit space.

[0094] The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present invention. For example, the configuration of the unit reflect array is not limited to the examples of the element pattern, unit cell, reflection control region, etc. described in Comparative Example 1. Further, the reflect array unit is not necessarily limited to arranging a plurality of reflect arrays in a plane, and it is also possible to arrange them on a curved surface within the scope of the gist of the present invention.

[0095] Aspects that can be the content of the present invention are described below, but are not limited thereto. (Aspect 1) A plurality of reflect arrays including an element pattern, a dielectric layer, and a ground layer are arranged in a plane, A unit space exists between the reflect arrays, The reflect array includes at least one reflection control region, The reflection control region is the same in all the reflect arrays, and a reflect array unit characterized by this. (Aspect 2) The reflect array unit according to Aspect 1, wherein the length of the unit space is 1 / 3 or more of the length of the reflection control region. (Aspect 3) The reflect array unit according to Aspect 1, wherein the length of the unit space is a natural number multiple of the length of the reflection control region. (Aspect 4) The reflect array unit according to any one of Aspects 1 to 3, wherein the lengths of the unit spaces are all the same. (Aspect 5) The reflect array unit according to any one of Aspects 1 to 4, including the reflect array arranged at the center in addition to the reflect arrays at the four corners arranged in a square. (Aspect 6) The reflect array unit according to any one of Aspects 1 to 5, wherein the reflect array is arranged on a support. (Aspect 7) 7. The reflect array unit according to claim 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, within the reflection control region, a first element width wx that is the width of the element pattern in the x-axis direction and / or a second element width wy that is the width of the element pattern in the y-axis direction differs for each of the element patterns arranged in at least two unit cells. [Explanation of symbols]

[0096] 1, 11-1 n , 1 x 1-1 x n , 1 y 1-1 y n ...element pattern, 2...Dielectric layer, 3...Ground layer, 4, 41-4 n , 4 x 1-4 x n , 4 y 1-4 y n ...unit cell, 5, 5a-5c, 5x, 5y...reflection control area, 6...Unit space 7 functional layers, 8 protective layer, 9 adhesive layer, 10 design layer, 11 installation layer, 12...Support 20, 20a-20h...Reflectarray 30...Reflect Array Unit 31...Base station 32...Radio wave shielding object 33...Blind zone 34...Radio wave area

Claims

1. A plurality of reflect arrays each including an element pattern, a dielectric layer, and a ground layer are arranged in a plane; There is a unit space between the reflectarrays, The reflectarray includes at least one reflection control area, The reflect arrays are arranged at four corners of a square, A reflectarray unit characterized in that reflection characteristics can be obtained such that reflections with a radar scattering cross section (RCS) of -15 dBsm or more can be obtained at any two or more angles excluding a range of ±1 degree of a reference asymmetric reflection, and the RCS of reflections occurring at peak angles other than the peak angle at which the RCS is maximum is within 10 dBsm of the maximum value.

2. The reflection control area is the same for all of the reflectarrays, 2. The reflect array unit according to claim 1, wherein the length of the unit space is equal to or greater than one-third or a natural number multiple of the size of the reflection control region in the direction in which the unit cells are arranged.

3. The reflect array unit according to claim 1 , wherein the unit spaces have the same length.

4. The reflectarray unit according to claim 1 , further comprising a reflectarray disposed at a center in addition to the reflectarrays disposed at the four corners of the square.

5. The reflect array unit according to any one of claims 1 to 4, wherein the reflect array is disposed on a support.

6. The reflect array unit according to claim 5 , wherein the relative dielectric constant of the support is 1 or more and 1.5 or less.

7. the shape of the element pattern includes a cross patch; 5. The reflect array unit according to claim 1, wherein, in the reflection control region, a first element width wx that is a width of the element pattern in the x-axis direction and / or a second element width wy that is a width of the element pattern in the y-axis direction differs for each of the element patterns arranged in at least two unit cells.

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