WO2025197863A1

WO2025197863A1 - Frequency-selective reflecting member

Info

Publication number: WO2025197863A1
Application number: PCT/JP2025/010278
Authority: WO
Inventors: Jumpei IMAI; Ryosuke KOTAKA; Shinpei Kondo
Original assignee: Toppan Holdings Inc
Current assignee: Toppan Holdings Inc
Priority date: 2024-03-19
Filing date: 2025-03-17
Publication date: 2025-09-25
Anticipated expiration: 2026-09-19
Also published as: JP2025144547A

Abstract

The present invention is directed to a technique for effectively controlling a reflection direction of a radio wave in a target band so as to realize asymmetric reflection and for regularly reflecting a radio wave in an off-target band. In a frequency-selective reflecting member according to the present invention, a frequency-selective plate including a stacked body in which two or more pattern layers and one or more dielectric layers are alternately stacked, and a radio-wave reflecting member are assembled with a functional gap in between, and a functional gap size is greater than or equal to G_min determined by an expression (1), where λ (mm) is a target wavelength appropriately selected in a target band. Further, the frequency-selective plate is designed so as to include a transmission band at least in a millimeter-wave band, and such that a width of a first transmission band is ±1.8% or less to a center wavelength, and a width of a second transmission band is ±2.3% or less to the center wavelength.

Description

FREQUENCY-SELECTIVE REFLECTING MEMBER

The present invention relates to a frequency-selective reflecting member.

The progress of digitalization in societies dramatically improves a data communication speed in wireless communication, and a frequency of an electromagnetic wave (hereinafter, also referred to as a "radio wave") has been increased along therewith. However, rectilinearity of the electromagnetic wave is increased as the frequency is increased. Thus, the electromagnetic wave does not run around to a rear side of a building and the like, and a dead zone where communication is not performable is easily generated.
For such a reason, it is necessary to increase the number of base stations in order to realize 5G/6G communication in a wide range. However, to increase the number of base stations, a large amount of costs is necessary, and it is accordingly difficult to promptly increase the number of base stations. In recent years, to solve such issues, a technique for controlling a reflection direction of the electromagnetic wave has attracted attention.

Patent Literature 1 describes a technique relating to a reflect array configured by combining one or more reflection control regions. When asymmetric reflection in which an incident angle and a reflection angle of the electromagnetic wave are different from each other is realized using the reflect array, it is possible to deliver the electromagnetic wave to the dead zone where the electromagnetic wave is conventionally hard to be delivered.
As a radio-wave reflecting member controlling the reflection direction of the radio wave, there are a static radio-wave reflecting member in which a plurality of element patterns are previously arranged and designed so as to realize a predetermined phase difference as described in Patent Literature 1, and a dynamic radio-wave reflecting member in which a phase difference of the radio wave is electrically variably adjusted.

Japanese Patent No. 7384308

In the existing radio-wave reflecting member, however, control of the reflection direction of the radio wave in a target band is mainly concerned, and a situation where the reflection direction of the radio wave in a band around the target band is simultaneously changed is not concerned. Such a situation makes it difficult to finely cope with needs and a specification for each band in terms of communication, antenna installation, and the like. For example, in a case where a reflection direction of a radio wave of a communication carrier A is controlled, influence is applied to a reflection direction of a radio wave of a communication carrier B allocated to a band that is close thereto, which generates an issue that it is not possible to cope with needs for individual reflection control. As a specific example, there are a 24 GHz band (i) (24.25 GHz to 24.45 GHz), a 24 GHz band (ii) (24.75 GHz to 25.25 GHz), a 26 GHz band (i) (24.25 GHz to 27.5 GHz), a 26 GHz band (ii) (24.75 GHz to 27.5 GHz), a 28 GHz band (27.5 GHz to 28.35 GHz), a 37 GHz band (37.6 GHz to 38.6 GHz), a 39 GHz band (38.6 GHz to 40.0 GHz), and a 47 GHz band (47.2 GHz to 48.2 GHz), and needs for controlling the reflection direction for each allocated band are expected. However, Patent Literature 1 does not describe that it should be recognized as an issue to control the reflection direction only for the predetermined band.

Therefore, the present invention is directed to a technique for effectively controlling a reflection direction of a radio wave in a target band so as to realize asymmetric reflection and for regularly reflecting a radio wave in an off-target band.

To solve the above-described issues, in a representative embodiment of a frequency-selective reflecting member according to the present invention, a frequency-selective plate including a stacked body in which two or more pattern layers and one or more dielectric layers are alternately stacked, and a radio-wave reflecting member are assembled with a functional gap in between, and a functional gap size is greater than or equal to G_min determined by an expression (1),
where λ (mm) is a target wavelength appropriately selected in a target band.

According to the embodiment of the frequency-selective reflecting member of the present invention, the reflection direction of the radio wave in the target band can be effectively control so as to realize asymmetric reflection, and the radio wave in the off-target band can be regularly reflected. As an example, the reflection direction of the radio wave in any one band allocated in a millimeter-wave band can be controlled, while the radio wave in the other band in the millimeter-wave band can be regularly reflected. Alternatively, the reflection direction of the radio wave in the entire millimeter-wave band can be controlled, while the radio wave in the other band such as a Sub-6 band can be regularly reflected.
Issues, configurations, and effects other than those described above are clarified by the following description of an embodiment.

FIG. 1 is diagrams illustrating definition of angles and coordinate axes. FIG. 2 is a cross-sectional view schematically illustrating a configuration of a frequency-selective reflecting member. FIG. 3 is a schematic diagram illustrating traveling states of a radio wave entering the frequency-selective reflecting member and a radio wave reflected by the frequency-selective reflecting member. FIG. 4 is a cross-sectional view illustrating a basic configuration of a frequency-selective plate. FIG. 5 is cross-sectional views each illustrating a configuration example of the frequency-selective plate including functional layers. FIG. 6 is plan views each illustrating an example of a pattern shape. FIG. 7 is graphs each illustrating ideal transmission characteristics of the frequency-selective plate that allows a radio wave in a predetermined frequency band to pass therethrough. FIG. 8 is diagrams each illustrating an example of a shape of a conductive pattern in an independent pattern structure after etching. FIG. 9 is diagrams each illustrating action of the frequency-selective reflecting member with respect to an incident radio wave in a case where a functional gap size is less than or equal to G_max. FIG. 10 is diagrams each illustrating action of the frequency-selective reflecting member with respect to an incident radio wave in a case where the functional gap size is greater than G_max. FIG. 11 is cross-sectional views each illustrating an example of the frequency-selective reflecting member using the frequency-selective plate as a radome. FIG. 12 is a cross-sectional view illustrating an example of the frequency-selective reflecting member in which radio wave absorbers are installed in side surfaces of the radome. FIG. 13 is plan views each illustrating a pattern shape of a pattern layer in a unit cell of a frequency-selective plate in Example 1. FIG. 14 is graphs each illustrating transmission characteristics of the frequency-selective plate in Example 1. FIG. 15 is a partial cross-sectional view of a radio-wave reflecting member in Example 1. FIG. 16 is plan views each illustrating the radio-wave reflecting member in Example 1. FIG. 17 is a graph illustrating reflection characteristics when a y-axis polarized wave is applied to the radio-wave reflecting member in Example 1 at θ_ix = 0° and θ_iy = 0°. FIG. 18 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to the frequency-selective reflecting member in Example 1 at θ_ix = 0° and θ_iy = 0°. FIG. 19 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to a frequency-selective reflecting member in Example 2 at θ_ix = 0° and θ_iy = 0°. FIG. 20 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to a frequency-selective reflecting member in Example 3 at θ_ix = 0° and θ_iy = 0°. FIG. 21 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to a frequency-selective reflecting member in Example 4 at θ_ix = 0° and θ_iy = 0°. FIG. 22 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to a radio-wave reflecting member in Example 5 at θ_ix = 0° and θ_iy = 0°. FIG. 23 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to a frequency-selective reflecting member in Example 5 at θ_ix = 0° and θ_iy = 0°. FIG. 24 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to a frequency-selective reflecting member in Comparative example 1 at θ_ix = 0° and θ_iy = 0°. FIG. 25 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to a frequency-selective reflecting member in Comparative example 2 at θ_ix = 0° and θ_iy = 0°. FIG. 26 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to a frequency-selective reflecting member in Comparative example 3 at θ_ix = 0° and θ_iy = 0°. FIG. 27 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to a frequency-selective reflecting member in Comparative example 4 at θ_ix = 0° and θ_iy = 0°. FIG. 28 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to a frequency-selective reflecting member in Comparative example 5 at θ_ix = 0° and θ_iy = 0°. FIG. 29 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to a frequency-selective reflecting member in Comparative example 6 at θ_ix = 0° and θ_iy = 0°.

An embodiment of a frequency-selective reflecting member according to the present invention is described below with reference to drawings. The present invention is not limited by the embodiment. Further, in description of the drawings, the same parts are denoted by the same reference numerals.

(Description of Terms)
In disclosure of the present embodiment, a "frequency-selective plate" is a member that can allow a radio wave in a predetermined frequency band to pass therethrough or reflect the radio wave in the predetermined frequency band. The frequency-selective plate may have a flat surface shape or a curved surface shape.
In the disclosure of the present embodiment, a "radio-wave reflecting member" indicates general members that can control a reflection direction of the radio wave, and examples thereof include a reflector that statically/dynamically controls the reflection direction of the radio wave, and a scattering plate that expands the reflection direction of the radio wave.

In the following description, an xyz coordinate system is applied, the frequency-selective reflecting member is formed on an xy plane, and the frequency-selective plate, a functional gap, and the radio-wave reflecting member that are components of the frequency-selective reflecting member are stacked along a z-axis direction. A diagram when the xy plane is viewed from the z-axis (in planar view) is referred to as a plan view, and a diagram when a cross-section parallel to the z-axis is viewed from a direction perpendicular to the cross-section (in cross-sectional view) is referred to as a cross-sectional view.
FIG. 1 is diagrams illustrating definition of angles and coordinate axes. An incident angle of an incident wave is denoted by θi. An incident angle in an x-axis direction is denoted by θ_ix, and an incident angle in a y-axis direction is denoted by θ_iy. A reflection angle of a main beam of a reflected wave is denoted by θ_r. A reflection angle in the x-axis direction is denoted by θ_rx, and a reflection angle in the y-axis direction is denoted by θ_ry. FIG. 1(a) illustrates a state where a radio wave made incident at the incident angle θ_ix in the x-direction is reflected at the reflection angle θ_rx in the x-axis direction, and FIG. 1(b) illustrates a state where a radio wave made incident at the incident angle θ_iy in the y-axis direction is reflected at the reflection angle θ_ry in the y-axis direction.
　Further, the angle θ_x in the x-axis direction expanded from the +z-axis direction to the +x-axis direction is represented as a positive angle (0 degrees to 180 degrees), whereas the angle θ_x in the x-axis direction expanded from the +z-axis direction to the -x-axis direction is represented as a negative angle (0 degrees to -180 degrees). Likewise, the angle θ_y in the y-axis direction expanded from the +z-axis direction to the +y-axis direction is represented as a positive angle (0 degrees to 180 degrees), whereas the angle θ_y in the y-axis direction expanded from the +z-axis direction to the -y-axis direction is represented as a negative angle (0 degrees to -180 degrees). Unless otherwise noted, θ_ix = θ_iy = 0° is satisfied.

(Frequency-Selective Reflecting Member)
FIG. 2 is a cross-sectional view schematically illustrating a configuration of the frequency-selective reflecting member. A frequency-selective reflecting member 4 has a configuration in which a frequency-selective plate 1, a functional gap 2, and a radio-wave reflecting member 3 are stacked. The frequency-selective plate 1 and the radio-wave reflecting member 3 are basically stacked so as to share a gravity center on the xy plane; however, the gravity center of the frequency-selective plate 1 and the gravity center of the radio-wave reflecting member 3 may be shifted from each other within a range not changing characteristics. Further, in a case where a size of the radio-wave reflecting member 3 on the xy plane is smaller than a size of the frequency-selective plate 1 on the xy plane, a radio wave absorber corresponding to a size difference is preferably installed on a plane flush with the radio-wave reflecting member 3.

FIG. 3 is a schematic diagram illustrating traveling states of a radio wave entering the frequency-selective reflecting member and a radio wave reflected by the frequency-selective reflecting member. Only a radio wave in a target band (solid arrow) passes through the frequency-selective plate 1, and is changed in reflection direction by the radio-wave reflecting member 3. Thereafter, the radio wave passes through the frequency-selective plate 1 again and is emitted to an outside. On the other hand, a radio wave in the other band (dashed arrow) does not pass through the frequency-selective plate 1, and is regularly reflected as with a metal body. Regular reflection used herein indicates that θ_i = -θ_r is substantially satisfied, and a difference between the angles on both sides is within ±10 degrees.

(Configuration of Frequency-Selective Plate)
FIG. 4 is a cross-sectional view illustrating a basic configuration of the frequency-selective plate. The frequency-selective plate 1 at least includes two or more pattern layers 5 (5-1, 5-2, ..., 5-n+1 in case of n+1 pattern layers 5), and one or more dielectric layers 6 (6-1, 6-2, ..., 6-n in case of n dielectric layers 6). The frequency-selective plate 1 is a stacked body (basic configuration) in which the pattern layers 5 and the dielectric layers 6 are alternately stacked. Basically, the number of parameters contributing to electric action is increased as the number of stacked layers is increased. This makes it possible to more precisely control transmission characteristics. Gaps in the pattern layers 5 may be filled with the dielectric layers 6, or the gaps may be maintained. Characteristics of the frequency-selective plate 1 can be changed by changing a specification of the above-described basic configuration.

As necessary, a layer for improving adhesion force of each of the pattern layers 5 and the dielectric layers 6 may be provided between each of the pattern layers 5 and the corresponding dielectric layer 6. Further, a layer used for application other than improvement of the adhesion force may be provided. Note that an intermediate product generated in a process of manufacturing the frequency-selective plate 1 may be formed in a layer shape, and may remain in the frequency-selective plate.

In the frequency-selective plate 1, one or a plurality of layers each having various types of functionalities (hereinafter, also referred to as "functional layers") are preferably stacked on one or both surfaces of the basic configuration based on applications. Examples of the functional layer include a design layer designed in consideration of a scenery of a place where the frequency-selective plate 1 is installed, an installation layer for facilitating installation of the frequency-selective plate on a wall, a ceiling, a window, or a support such as a radome, a protective layer for protecting the basic configuration, and a bonding layer and an adhesion layer for stacking the basic configuration and the functional layer, for stacking the functional layers, or for bonding the basic configuration or the functional layer to an adherend.
As a stacking method for stacking the functional layer on the basic configuration, the gap of any pattern layer 5 may be filled with the functional layer, or the gap may be maintained. The characteristics of the frequency-selective plate 1 can be changed by changing the stacking method.

FIG. 5 is cross-sectional views each illustrating a configuration example of the frequency-selective plate including the functional layers. FIG. 5(a) illustrates the frequency-selective plate 1 in which the basic configuration includes three pattern layers 5 and two dielectric layers 6, a protective layer 7 is stacked on each of the both surfaces of the basic configuration, and an installation layer 9 is provided on one of outside surfaces through a bonding layer 8.
FIG. 5(b) illustrates the frequency-selective plate 1 in which the basic configuration includes two pattern layers 5 and one dielectric layer 6, the protective layer 7 is stacked on each of both surfaces of the basic configuration, a design layer 10 is provided on one of outside surfaces through the bonding layer 8, and the installation layer 9 is provided on the other outside surface through the bonding layer 8.

(Pattern Layer of Frequency-Selective Plate)
Each pattern layer 5 includes a conductive pattern and a gap, and a structure is classified into a continuous pattern structure in which a specific shape is removed from a uniform conductor, and an independent pattern structure in which conductors each having a specific shape are independently arranged like islands.

In the following, in a case where the pattern layer 5 has the continuous pattern structure, the pattern indicates a portion of the gap, whereas in a case where the pattern layer 5 has the independent pattern structure, the pattern indicates a portion of the conductive pattern. Therefore, in a case of the same pattern shape, the continuous pattern structure and the independent pattern structure have complementary relationship. The pattern layer 5 includes one or more patterns having specific shape and size.

The structures of the two or more pattern layers 5 included in the frequency-selective plate 1 may be only the continuous pattern structures, only the independent pattern structures, or a combination of the continuous pattern structure and the independent pattern structure. In each of the cases, the pattern shapes of the pattern layers 5 may be the same as or different from each other. The layers having different pattern structures are preferably stacked because the target transmission band of the frequency-selective plate can be made narrow.

FIG. 6 is plan views each illustrating an example of the pattern shape. However, the pattern shape is not limited to these examples. Various shapes can be applied as the pattern shape (see FIGS. 6(a) to 6(h)), and the transmission characteristics of the radio wave are changed depending on the shape and the size. For example, to obtain similar transmission characteristics from the radio wave in which an electric field direction is parallel to the x-axis (x-axis polarized wave) and the radio wave in which an electric field direction is parallel to the y-axis (y-axis polarized wave), it is necessary to make the pattern shape line symmetrical about the x-axis and the y-axis such that the same pattern shape is applied to the polarized waves. As described above, the shape having high symmetry can be applied to more polarized waves. The frequency-selective plate 1 includes two or more pattern layers 5, and the pattern shape having high symmetry is preferably adopted in more pattern layers 5.

Each pattern layer 5 may include a plurality of patterns having the same shape and the same size, or may mixedly include patterns different in shape and size. Further, in arrangement of the patterns, the pattern layer 5 may be sectioned into unit cells, a pattern may be formed in each unit cell, and the patterns may be arranged at equal intervals or at intervals partially changed.

In the present embodiment, a difference among occupancies of the conductive patterns of the pattern layers 5 is preferably 75 points or less, more preferably 50 points or less, and further preferably 25 points or less. A percentage of an area of the conductive pattern to an entire area of the frequency-selective plate 1 as viewed from the z-axis direction is referred to as the occupancy (%), and the difference of the occupancy (%) is referred to as a point (may also be referred to as, for example, a percentage point (%pt)). In a case where the difference among the occupancies of the conductive patterns of the two or more pattern layers 5 is within the above-described value, difference of stress applied from the conductive patterns to the respective dielectric layers 6 is small, and the frequency-selective plate 1 can be maintained flat. The effect remarkably appears in a case where each dielectric layer 6 has a small thickness and has high flexibility.
　To adjust the occupancy area of the conductive pattern, the pattern shape or the size is changed. In addition, the conductive pattern may be formed in a mesh shape with specific intervals within a range not affecting radio wave characteristics of the frequency-selective plate. Alternatively, a gap having a specific shape may be provided as a dummy pattern in the conductive pattern of the continuous pattern structure.

(Transmission Characteristics of Frequency-Selective Plate)
The radio wave in an operation band (hereinafter, also referred to as a "target band") passes through the frequency-selective plate 1, and is changed in reflection direction by the radio-wave reflecting member 3. Thereafter, the radio wave passes through the frequency-selective plate 1 again, and is emitted to the outside. In other words, it is assumed that the radio wave in the operation band passes through the frequency-selective plate 1 twice, and an incident angle to the frequency-selective plate 1 is varied every time. If a transmittance is low in a transmission band, radio wave intensity is drastically reduced by twice transmission. Further, in a case where the characteristics are largely changed relative to change in incident angle, the transmittance may be reduced at the incident angle at any of incidence from the outside to the frequency-selective plate 1 and incidence from the radio-wave reflecting member 3 to the frequency-selective plate 1.

The transmittance of the frequency-selective plate 1 is described below. In the present embodiment, a band where a transmittance difference from a maximum transmittance is within 3 dB is defined as a first transmission band, and a band where the transmittance different from the maximum transmittance is within 6 dB is defined as a second transmission band. The maximum transmittance is preferably high, is -10 dB or more, preferably -6 dB or more, more preferably -3 dB or more, and further preferably -1 dB or more. Further, a difference between the first and second transmission bands is preferably small, and this is equal to a fact that the transmittance is steeply reduced over an outside of the transmission band. In addition, the transmittance on the outside of the second transmission band is preferably low, is -6 dB or less, preferably -10 dB or less, and more preferably -20 dB or less.
Practically, the target band is desirably included in at least the second transmission band of the frequency-selective plate 1, and is more desirably included in the first transmission band.

FIG. 7 is graphs each illustrating ideal transmission characteristics of the frequency-selective plate that allows the radio wave in a predetermined frequency band to pass therethrough. FIG. 7 illustrates characteristics when θ_ix = θ_iy = 0° is satisfied; however, the characteristics are preferably not changed even in a case where the angle is varied.
Although rectangular transmission characteristics illustrated in FIG. 7 are ideal, but mountain-like transmission characteristics are actually obtained. In this case, a steep mountain indicates high frequency selectivity. Therefore, to define the steepness of the mountain, two positions on a hillside are defined as the first transmission band and the second transmission band as described above.

In FIG. 7(a), the first and second transmission bands are substantially equal to each other, and are 27.0 GHz to 29.5 GHz. When the transmission band is converted to a wavelength, the wavelength is 10.16 mm to 11.10 mm, and when the wavelength is converted to a transmission band width to a center wavelength, the transmission band width is ±4.42%. The transmittance in the first and second transmission bands is close to 0 dB, and the transmittance on the outside of the second transmission band is -20 dB or less. A physical phenomenon may occur based on the wavelength. Therefore, if the transmission band width is defined based on the frequency, the transmission band width for the radio wave is different between a low frequency band and a high frequency band. Thus, the transmission band width is defined based on the wavelength.

In FIG. 7(b), the first and second transmission bands are substantially equal to each other, and are 27.0 GHz to 27.4 GHz. When the transmission band is converted to a wavelength, the wavelength is 10.94 mm to 11.10 mm, and when the wavelength is converted to a transmission band width to the center wavelength, the transmission band width is ±0.74%. The transmittance in the first and second transmission bands is close to 0 dB, and the transmittance on the outside of the second transmission band is -20 dB or less.

In FIG. 7(c), the first and second transmission bands are substantially equal to each other, and are 38.6 GHz to 40.0 GHz. When the transmission band is converted to a wavelength, the wavelength is 7.49 mm to 7.77 mm, and when the wavelength is converted to a transmission band width to the center wavelength, the transmission band width is ±1.8%. The transmittance in the first and second transmission bands is close to 0 dB, and the transmittance on the outside of the second transmission band is -20 dB or less.

In FIG. 7(d), the first and second transmission bands are substantially equal to each other, and are 24.25 GHz to 24.45 GHz. When the transmission band is converted to a wavelength, the wavelength is 12.26 mm to 12.36 mm, and when the wavelength is converted to a transmission band width to the center wavelength, the transmission band width is ±0.5%. The transmittance in the first and second transmission bands is close to 0 dB, and the transmittance on the outside of the second transmission band is -20 dB or less.

The frequency-selective plate 1 can be designed so as to allow the radio wave in an entire millimeter-wave band to pass therethrough, or can be designed so as to allow the radio wave in a 24 GHz band (i) (24.25 GHz to 24.45 GHz), a 24 GHz band (ii) (24.75 GHz to 25.25 GHz), a 26 GHz band (i) (24.25 GHz to 27.5 GHz), a 26 GHz band (ii) (24.75 GHz to 27.5 GHz), a 28 GHz band (27.5 GHz to 28.35 GHz), a 37 GHz band (37.6 GHz to 38.6 GHz), a 39 GHz band (38.6 GHz to 40.0 GHz), and a 47 GHz band (47.2 GHz to 48.2 GHz) to pass therethrough individually or in combination.

Further, the frequency band is not limited to the millimeter-wave band (20 GHz to 300 GHz), and the frequency-selective plate 1 can be applied to a Sub-6 band (3.6 GHz to 4.9 GHz) used for 5G/6G, and a terahertz band (0.1 THz to 10 THz).

For example, in a case where the target band is the 28 GHz band (27.5 GHz to 28.35 GHz), the first transmission band is preferably 27.5 GHz to 28.35 GHz. When the first transmission band is converted to a wavelength, the wavelength is 10.57 mm to 11.90 mm, and the transmission band width to the center wavelength (10.74 mm) is ±1.6%. At this time, the second transmission band may be 27.3 GHz to 28.6 GHz. When the second transmission band is converted to a wavelength, the wavelength is 10.50 mm to 10.98 mm, and the transmission band width to the center wavelength (10.74 mm) is ±2.3%. Accordingly, in this case, it is sufficient to use the frequency-selective plate 1 in which the width of the first transmission band is ±1.6% or less to the center wavelength and the width of the second transmission band is ±2.3% or less to the center wavelength.

Likewise, in a case where the target band is the 24 GHz band (i) (24.25 GHz to 24.45 GHz), it is sufficient to use the frequency-selective plate 1 in which the width of the first transmission band is ±0.5% or less to the center wavelength and the width of the second transmission band is ±1.3% or less to the center wavelength. In a case where the target band is the 24 GHz band (ii) (24.75 GHz to 25.25 GHz), it is sufficient to use the frequency-selective plate 1 in which the former is ±1.0% or less and the latter is ±1.8% or less. In a case where the target band is the 26 GHz band (i) (24.25 GHz to 27.5 GHz), it is sufficient to use the frequency-selective plate 1 in which the former is ±6.3% or less and the latter is ±7.1% or less. In a case where the target band is the 26 GHz band (ii) (24.75 GHz to 27.5 GHz), it is sufficient to use the frequency-selective plate 1 in which the former is ±5.3% or less and the latter is ±6.0% or less. In a case where the target band is the 37 GHz band (37.6 GHz to 38.6 GHz), it is sufficient to use the frequency-selective plate 1 in which the former is ±1.4% or less and the latter is ±1.9% or less. In a case where the target band is the 39 GHz band (38.6 GHz to 40.0 GHz), it is sufficient to use the frequency-selective plate 1 in which the former is ±1.8% or less and the latter is ±2.3% or less. In a case where the target band is the 47 GHz band (47.2 GHz to 48.2 GHz), it is sufficient to use the frequency-selective plate 1 in which the former is ±1.1% or less and the latter is ±1.5% or less.

The transmission characteristics of the frequency-selective plate 1 described above are realized by adjusting the sizes of the patterns and the intervals of the patterns in the pattern layers 5, and physical properties (such as thicknesses and permittivities) of the dielectric layers 6. The frequency-selective plate generally has a plurality of transmission bands in, for example, a band corresponding to a substantially integral multiple of the wavelength of the transmission band. In other words, the frequency-selective plate may have a transmission band other than the target band. However, the band other than the target band is normally out of a band where the reflection direction is controlled by the radio-wave reflecting member. Thus, no problem exists.

The incident angle to the frequency-selective plate 1 is described below. There is not only a case where the radio wave enters the frequency-selective plate 1 along the negative direction of the z-axis, but also a case where the radio wave obliquely enters the frequency-selective plate 1. In addition, even at the same oblique incident angle, characteristics are different depending on a polarized wave. Thus, it is necessary to consider the polarized wave. For example, a case where a polarized wave in which an electric field direction is parallel to the x-axis enters the frequency-selective plate 1 from an oblique direction on the xz plane, and a case where a polarized wave in which an electric field direction is parallel to the y-axis enters the frequency-selective plate 1 are assumed. Even in the case where the radio wave obliquely enters the frequency-selective plate 1 as described above, the transmission characteristics are preferably not largely changed as compared with the case where the radio wave enters the frequency-selective plate 1 along the negative direction of the z-axis.
More specifically, with respect to the incident angle of 0 degrees to 60 degrees, a shift amount of the center wavelength in the first transmission band is preferably within 10%, and a change width of the maximum transmittance is preferably within 6 dB (shift amount is ratio obtained by dividing difference of center wavelengths before and after incident angle of radio wave is shifted, by center wavelength before shift). Further, the transmission characteristics are preferably not changed between a case where the radio wave along a positive direction of the z-axis enters the frequency-selective plate 1 and the case where the radio wave along the negative direction of the z-axis enters the frequency-selective plate 1.

(Method of Designing Frequency-Selective Plate)
A method of designing the frequency-selective plate 1 is described. Note that, in step 4, manpower saving and time reduction can be realized by using an optimization technique.
(Step 1) First, the target band and an off-target band are determined.
(Step 2) A layer configuration is determined. More specifically, the number of pattern layers and dielectric layers to be stacked in the basic configuration, and a thickness and material physical property of each of the layers are determined. In a case where the functional layer is stacked, a thickness and material physical property of the functional layer are also determined.
(Step 3) A structure (continuous pattern structure or independent pattern structure) and a pattern shape of each pattern layer are determined.
(Step 4) Appropriate parameters relating to the pattern shape are set as design parameters.
(Step 5) The design parameters are adjusted so as to develop target transmission characteristics.

(Method of Manufacturing Frequency-Selective Plate)
As a main method of manufacturing the basic configuration of the frequency-selective plate 1, the conductive pattern is formed by performing cutting, etching (dry etching or wet etching), or the like on a copper-clad laminate used for a printed circuit board and the like, or on a dielectric layer in which a metal film is formed on one or both surfaces by dry coating of a vapor deposition method or a sputtering method, plating processing, wet coating, or the like.

FIG. 8 is diagrams each illustrating an example of a shape of the conductive pattern in the independent pattern structure after etching. FIG. 8(a) is a plan view of the conductive pattern, and FIGS. 8(b) to 8(d) are cross-sectional views each illustrating the conductive pattern. In a case of using the etching method, corner rounding (FIG. 8(a)) or a pin hole may be generated in a conductive pattern 11. Further, it is assumed that, in a cross-sectional view of the conductive pattern 11, a forward taper (FIG. 8(b)), a reverse taper (FIG. 8(c)), or rounding (FIG. 8(d)) is formed. In the case of using the etching method, the cross-sectional shape of the conductive pattern 11 is preferably the forward tapered shape that is a shape in which a bottom of the conductive pattern 11 is widened as going in the negative direction of the z-axis. When the conductive pattern 11 has the forward tapered shape, entrance of air hardly occurs in stacking of the functional layer, which makes it possible to suppress change of the transmission characteristics and deterioration of adhesion force.
In a case where the above-described shape change occurs, the transmission characteristics may be shifted from the designed characteristics; however, the shift can be eliminated by designing the transmission characteristics again in consideration of the shape change.
　In the case of cutting, a dimensional error of the conductive pattern 11 is generally about ±100 μm. In the case of etching, the dimensional error of the conductive pattern 11 is generally about ±50 μm.

As another manufacturing method, a method of directly forming the conductive pattern 11 on each dielectric layer 6 is usable. The conductive pattern 11 can be printed using letterpress printing, planographic printing, intaglio printing, stencil printing, transfer printing, or the like. Further, the conductive pattern 11 can be formed in such a manner that a portion of the dielectric layer 6 other than the conductive pattern 11 is masked with a masking tape, a masking agent, or the like, and the conductive pattern 11 is formed by dry coating, plating processing, painting, or a spraying method.

To stack the functional layer on the basic configuration, bonding, printing/coating, and extrusion molding are usable. As bonding, for example, dry lamination, wet lamination, heat lamination, or extrusion lamination is usable, but bonding is not limited thereto.

(Conductive Pattern in Frequency-Selective Plate)
As a material of the conductive pattern 11, a material having conductivity such as an inorganic oxide material, a metal material, and an organic material having conductivity is used.
Examples of the inorganic oxide material and the metal material include indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), tin antimony oxide, Ag, Al, Au, Pt, Pd, Cu, Co, Cr, In, Ag-Cu, Cu-Au, and Ni. Further, nanoparticles or a nanowire containing at least one of these materials may be used. Examples of the organic material having conductivity include a polythiophene derivative, a polyacetylene derivative, a polyaniline derivative, a polypyrrole derivative, a carbon nanotube, and graphene. In particular, in terms of a material cost, conductivity, and film-forming property, Cu or Al is preferable. In addition, to reflect the electromagnetic wave, a surface resistance value of a ground layer is desirably 100 Ω/sq. or less. As long as the condition can be satisfied, a frequency-selective plate having transparency can be fabricated by using ITO, a mixture (PEDOT/PSS) of polyethylene dioxythiophene (PEDOT) and polystyrene sulfonic acid (PSS).
In a case where a transparent conductive material is used for the conductive pattern 11, the frequency-selective plate shows visible light permeability, which makes it possible to maintain scenery after installation of the frequency-selective plate.

In a case of using the metal material, the method of forming the conductive pattern 11 can be selected from dry coating such as a sputtering method and a vapor deposition method, wet coating using ink of the metal material such as gravure coating and die coating, and surface processing such as plating processing. Alternatively, as the conductive pattern 11, a rolled metal plate may be used. In a case of using the inorganic oxide material, dry coating is selectable as the method of forming the conductive pattern 11. In a case of using the organic material, wet coating is selectable as the method of forming the conductive pattern 11. In addition, the conductive pattern 11 may be formed by painting or a spraying method.

In a case where a form of the conductive pattern 11 is a thin film formed by plating processing, a vapor deposition method, or the like, flexibility of the frequency-selective plate 1 can be improved. This enables use on a curved surface, and execution of a roll-to-roll production process.

In a case where the conductive pattern 11 is formed using the thin film, a thickness thereof is preferably greater than a skin depth calculated from an expression (4).
where d is the skin depth, ω is an angular frequency, μ is a permeability of a material, and σ is an electric conductivity of the material.
To enhance the transmittance of the transmission band, radio wave loss by the conductive pattern 11 is reduced. Therefore, a surface roughness of the conductive pattern 11 is preferably small.

(Dielectric Body in Frequency-Selective Plate)
In addition to single resin and glass, a composite material in which paper, glass fibers, carbon fibers, or the like is impregnated with resin is usable for each dielectric layer 6.
Examples of the single resin include polyethylene (εr = 2.2 to 2.4), polypropylene (εr = 2.0 to 2.6), polystyrene (εr = 2.4 to 2.6), polyvinyl chloride (εr = 2.8 to 8.0), AS resin (εr = 2.6 to 3.1), ABS resin (εr = 2.4 to 4.1), polyethylene terephthalate (εr = 2.9 to 3.0), acrylic resin (εr = 2.7 to 4.5), urethane resin (εr = 4.0 to 7.1), epoxy resin (εr = 2.5 to 6.0), nylon (εr = 3.0 to 5.0), polyimide (εr = 2.4 to 2.7), fluorine resin (εr = 2.0 to 2.6), polycarbonate (εr = 2.9 to 8.9), polyphenylene ether (εr = 2.8 to 8.2), polyphenylene sulfide (εr = 3.2 to 4.6), polyvinylidene fluoride (εr = 6.4 to 10.0), polyethylene naphthalate (εr = 2.9), phenol resin (εr = 3.0 to 12.0), and cycloolefin polymer (εr = 2.3 to 2.5). Here, er indicates a relative permittivity. In particular, polyethylene terephthalate (PET) is preferably used because polyethylene terephthalate (PET) is inexpensive and excellent in versatility. Further, the dielectric layer 6 may be a single layer or a multi-layer. A foam of any of the above-described materials may be used for the dielectric layer 6. As the foam, a foam having high flexibility is preferably used.
As the composite material, for example, a composite material of paper/phenol resin, paper/epoxy resin, glass/epoxy resin, or glass/fluorine resin is usable.

In addition, in terms of adjustment in permittivity, a mixture containing resin components or a mixture containing a dielectric compound and a resin component is usable. The relative permittivity of the mixture can be adjusted based on selection and a content of the dielectric compound.
The relative permittivity of the mixture can be predicted using, for example, a Maxwell-Garnett model. In a case where, in a mixture of a dielectric body A having a relative permittivity ε_a and a dielectric body B having a relative permittivity ε_b, a volume fraction of the dielectric body A is δ_a, a relative permittivity ε_m of the mixture is expressed by a relational expression (5),

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

In a case of using a dielectric body having transparency, the frequency-selective plate shows visible light permeability, which makes it possible to maintain scenery after installation of the frequency-selective plate.

A dielectric loss tangent of the dielectric layer 6 is preferably within a range of 0.00005 or more and 0.01 or less, and is preferably within a range of 0.00005 or more and 0.001 or less. When the dielectric loss tangent of the dielectric layer 6 is within the above-described range, transmittance of the transmission band can be enhanced.

The dielectric layer 6 can be formed by, for example, wet coating such as die coating, comma coating, and gravure coating, a melt extrusion method such as a T-die method and an inflation method, a calendar film forming method, a solution casting method, and a heat press method. Alternatively, a coextrusion method that extrudes a plurality of resins into a multi-layer to form a film may be used.

In a case where the dielectric layer 6 has a small thickness, flexibility of the frequency-selective plate 1 can be improved. This enables use on a curved surface, and execution of a roll-to-roll production process. A thickness of the dielectric layer is 5 mm or less, preferably 1 mm or less, more preferably 0.5 mm or less, and further preferably 0.1 mm or less.
A bending elastic modulus (JIS K7171) of the frequency-selective plate 1 is preferably 20 GPa or less, more preferably 10 GPa or less, and further preferably 5 GPa or less. When the bending elastic modulus is within the above-described range, the frequency-selective plate 1 has flexibility. When the frequency-selective plate 1 has flexibility, for example, even in a case where the frequency-selective plate 1 is wound around a core having an inner diameter of 6 inches and a thickness of 8 mm, and is maintained for one minute, appearance abnormality such as wrinkles and folding hardly occurs. Therefore, use of the frequency-selective plate 1 on a curved surface is facilitated.

(Radio-Wave Reflecting Member)
A configuration of the radio-wave reflecting member 3 is not particularly limited as long as the member has a function of controlling the reflection direction of the radio wave. In a case where static control is performed, for example, a configuration in which a ground layer, a dielectric layer, and element patterns are stacked, phase control of a reflected radio wave is performed for each of the element patterns slightly different in shape, thereby realizing reflection in a predetermined direction is considered. In a case where dynamic control is performed, for example, a configuration in which a ground layer, a liquid crystal layer, and element patterns are stacked, and orientation of liquid crystal is electrically controlled to perform phase control of the reflected radio wave for each of the element patterns, thereby realizing reflection in a predetermined direction is considered.

Distribution of the reflection phase in the radio-wave reflecting member is determined so as to follow, for example, expressions (6) and (7). A wavelength of an operation frequency (hereinafter, also referred to as a "target wavelength") is denoted by λ(mm), an x-axis component of an incident angle of a radio wave entering the radio-wave reflecting member is denoted by θ_ix, a y-axis component is denoted by θ_iy, an x-axis component of a reflection angle of an electromagnetic wave reflected by the radio-wave reflecting member is denoted by θ_rx, a y-axis component is denoted by θ_ry, reflection phases at coordinates x1 and x2 parallel to the x-axis in the radio-wave reflecting member are respectively denoted by φ_x1 and φ_x2, a distance between the coordinates x1 and x2 is denoted by Δx, and a reflection phase difference between Φx1 and Φx2 is denoted by ΔΦx. In addition, reflection phases at coordinates y1 and y2 parallel to the y-axis are respectively denoted by φ_y1 and φ_y2, a distance between the coordinates y1 and y2 is denoted by Δy, and a reflection phase difference between Φy1 and Φy2 is denoted by ΔΦy. To cause the radio-wave reflecting member to perform asymmetric reflection along the x-axis direction, the expression (6) is preferably satisfied. To cause the radio-wave reflecting member to perform asymmetric reflection along the y-axis direction, the expression (7) is preferably satisfied. To cause the radio-wave reflecting member to perform asymmetric reflection in both the x-axis direction and the y-axis direction, both the expression (6) and the expression (7) are preferably satisfied.

(Functional Gap)
The functional gap 2 means a space between the conductive pattern 11 of the pattern layer 5 closest to the radio-wave reflecting member 3 in the frequency-selective plate 1 and the element pattern in the radio-wave reflecting member 3. A functional gap size means a closest distance therebetween. The functional gap 2 has a role of securing the distance therebetween, and the gap or the dielectric body is present therein.
In a case where the functional gap 2 is absent or in a case where the functional gap size is excessively small, electric interaction between the frequency-selective plate 1 and the radio-wave reflecting member 3 is increased, and shift occurs in a resonance frequency and the like. As a result, characteristics of each of the members are changed from original characteristics. In addition, in a case where the functional gap size is excessively small, a wave surface of the radio wave immediately after passing through the frequency-selective plate 1 is disturbed, and the radio-wave reflecting member 3 may not exhibit the original reflection characteristics to such a wave surface. The present inventor found that the functional gap size (G_min) minimally necessary for developing effects of the present embodiment is expressed by the expression (1).

The functional gap size is not particularly limited as long as the functional gap size is G_min or more expressed by the expression (1); however, to maximize the effects of the frequency-selective plate 1, the functional gap size is preferably equal to G_maxx and G_maxy respectively calculated from the expression (2) and the expression (3), or a smaller value thereof (hereinafter, referred to as G_max) or less. In the expressions, L_fx and L_fy are lengths in the x-axis direction and the y-axis direction of the frequency-selective plate 1, respectively, and L_rx and L_ry are lengths in the x-axis direction and the y-axis direction of the radio-wave reflecting member 3, respectively. Further, θ_ix and θ_iy are an x-axis component and a y-axis component of an incident angle θ_i of the incident wave, respectively.

FIG. 9 is diagrams each illustrating action of the frequency-selective reflecting member with respect to the incident radio wave in a case where the functional gap size is G_max or less. As illustrated in FIG. 9(a), the incident wave in the target band that is allowed to pass through the frequency-selective plate 1 is reflected by the radio-wave reflecting member 3 without hindrance, whereas as illustrated in FIG. 9(b), the incident wave outside the target band is blocked by the frequency-selective plate 1 and cannot reach the radio-wave reflecting member 3. Thus, the radio wave outside the target band is avoided from being mixed into the radio wave in the target band.

FIG. 10 is diagrams each illustrating action of the frequency-selective reflecting member with respect to the incident radio wave in a case where the functional gap size is greater than G_max. As illustrated in FIG. 10(a), the incident wave in the target band is reflected by the radio-wave reflecting member 3 without hindrance, whereas as illustrated in FIG. 10(b), a part of the incident wave outside the target band is regularly reflected by the frequency-selective plate 1 and is not mixed into the radio wave in the target band, but a remaining part of the radio wave reaches the radio-wave reflecting member 3, and is randomly multiply reflected in a space of the gap. Thus, a risk of emitting noise to the outside of the frequency-selective reflecting member 4 is generated, which is not desirable.
However, even in the case where the functional gap size is greater than G_max, the radio wave that does not pass through the frequency-selective plate but directly abuts on the radio-wave reflecting member can be blocked by installing a member that prevents entering of the radio wave, such as a radio wave absorber (described below) on a side surface of the frequency-selective reflecting member.

In the functional gap 2, a gap or a dielectric body is present. The dielectric body may be the functional layer provided in the frequency-selective plate 1. In a case where a permittivity of the dielectric body is large, frequency characteristics of the single radio-wave reflecting member 3 and the frequency characteristics of the single frequency-selective plate 1 are easily changed. Further, in a case where a dielectric loss tangent is large, reflection efficiency of the radio wave is lowered. Therefore, a material having a low permittivity and a low dielectric loss tangent is preferably used for the dielectric body.

In addition to single resin and glass, a composite material in which paper, glass fibers, carbon fibers, or the like is impregnated with resin is usable for the dielectric body. In addition, foam resin may be used. In a case of a foamed shape, a foaming rate is normally about several times to about hundred times; however, a low permittivity and a low dielectric loss tangent are easily realized when the foaming rate is higher.
Examples of the foam resin include polystyrene foam, polyurethane foam, polyethylene foam, polypropylene foam, EVA foam, PET resin foam, phenol foam, silicone foam, polyvinyl chloride foam, urea foam, acrylic foam, polyimide foam, EPDM foam, melamine resin foam, epoxy foam, melamine foam, ABS foam, and fluorine resin foam.

(Radome)
The frequency-selective reflecting member 4 can be improved in weatherability by being wholly or partially assembled in a radome. The radome is a cover for protecting an antenna and a radio wave control member. At this time, the frequency-selective plate 1 can be used as the radome. FIG. 11 is cross-sectional views each illustrating an example of the frequency-selective reflecting member using the frequency-selective plate as the radome. FIG. 11(a) illustrates an example in which the frequency-selective plate 1 is assembled in a radome 12. FIG. 11(b) illustrates an example in which the frequency-selective plate 1 is bonded to an inside of the radome 12. FIG. 11 illustrates the frequency-selective reflecting member 4 that covers the radio-wave reflecting member 3 by the radome 12 including the frequency-selective plate 1.

The radome 12 may have any of a flat surface shape, a columnar surface shape, a spherical surface shape, and the like. When a honeycomb structure is adopted inside the radome 12, mechanical strength can be enhanced. In a case where the frequency-selective plate 1 is installed in a curved surface shape, angle change when the radio wave enters the frequency-selective plate 1 from the outside and angle change when the radio wave is reflected by the radio-wave reflecting member 3 and then enters the frequency-selective plate 1 again can be suppressed.

FIG. 12 is a cross-sectional view illustrating an example of the frequency-selective reflecting member in which radio wave absorbers are installed in side surfaces of the radome. When radio wave absorbers 13 are installed in side surfaces of the radome 12, it is possible to block the radio wave that does not pass through the frequency-selective plate 1 but directly abuts on the radio-wave reflecting member 3.

Examples of a material of the radome 12 include single resin, and resin containing an additive, glass fibers, or carbon fibers. Loss of the radio wave by the radome can be reduced as dielectric loss tangent of the material is lower. Examples of a type of the above-described resin include polyamide resin, polyester resin, polypropylene resin, polystyrene resin, polycarbonate resin, modified polyphenylene ether resin, and acrylic resin.
The loss of the radio wave by the radome 12 is 3 dB or less, preferably 2 dB or less, and more preferably 1 dB or less.

(Protective Layer)
To prevent oxidative deterioration, physical flaws and peelings of an element and a ground plate, a film or a sheet having gas barrier property, water vapor barrier property, water resistance, wear resistance, and scratch resistance is used for the protective layer 7.
In a case where indoor use of the frequency-selective plate 1 is assumed, the protective layer having antimicrobial property, antiviral property, contamination resistance, and the like is preferably used. In a case where outdoor use of the frequency-selective plate 1 is assumed, weatherability is required. Therefore, a layer containing an UVA (ultraviolet absorber) or a HALS (light stabilizer) may be used. The protective layer may be stacked with a bonding layer or an adhesion layer, or may be directly bonded to the basic configuration by heat sealing depending on a material.

(Installation Layer)
The installation layer 9 is a layer for fixing the frequency-selective plate 1 to a support. For example, in a case where the support is made of metal, a magnet is usable. In a case of using the magnet, it is possible to easily change a position and an angle of the frequency-selective plate.

(Design Layer)
The design layer 10 is a layer for imparting design to the front surface of the frequency-selective plate 1. For example, in a case where the frequency-selective plate 1 is used for an architectural decoration material such as wall paper, the design layer 10 may be further provided in order to realize harmony with a space. In a case where the frequency-selective plate 1 is used as a white board, a functional film may be used as the design layer 10. The function of the protective layer 7 may be imparted to the design layer 10.

Example

Examples and Comparative examples are described below. An object of the frequency-selective reflecting member 4 is to realize asymmetric reflection at a target frequency, and to prevent asymmetric reflection at an off-target frequency. In Examples, such characteristics were evaluated as "frequency-selective reflecting performance". More specifically, at the target frequency, an angle at which asymmetric reflection by the single radio-wave reflecting member 3 became maximum was denoted by θ, reflection intensity was denoted by a_tgt. (dBsm or dB), reflection intensity at the angle θ of the frequency-selective reflecting member 4 at the target frequency was denoted by b_tgt. (dBsm or dB), and reflection intensity at the angle θ of the frequency-selective reflecting member at the off-target frequency was denoted by b_off-tgt. (dBsm or dB). At this time, in a case where the expression (8) was satisfied, the frequency-selective reflecting performance was evaluated to be acceptable (good), and otherwise, the frequency-selective reflecting performance was evaluated to be unacceptable (poor).
The target frequency and the off-target frequency were selected, for example, in the following manner. In a case where the frequency-selective reflecting member 4 was set so as to operate in the 28 GHz band, but so as not to operate in the Sub-6 band, an appropriate frequency in the 28 GHz band was selected as the target frequency, and an appropriate frequency in the Sub-6 band was selected as the off-target frequency. In Examples and Comparative examples, the target frequency was set to 28 GHz, and the off-target frequency was set to 27 GHz and 29 GHz.
　Results of the reflection characteristics described in Examples and Comparative examples are results obtained by performing analysis by using finite element method analysis software (HFSS) manufactured by Ansys Inc., except for Example 5 that is an actual measurement result.

<Structure and Characteristics of Frequency-Selective Plate>
The frequency-selective plate 1 included two pattern layers 5 and one dielectric layer 6. Copper having a thickness of 0.18 mm was used for the conductive patterns of the pattern layers 5, and polystyrene resin having a thickness of 0.110 mm was used for the dielectric layer 6. An electric conductivity of copper was 5.8 × 10^7 siemens/m, a real part of a relative permittivity of the polystyrene resin was 2.428, and tanδ was 0.000667.

FIG. 13 is plan views each illustrating a pattern shape of the pattern layer in a unit cell of the frequency-selective plate in Example 1. FIG. 13(a) illustrates a pattern shape of a pattern layer 5-1, and FIG. 13(b) illustrates a pattern shape of a pattern layer 5-2 (see FIGS. 4 and 5). The pattern layer 5-1 had the continuous pattern structure, and had a cross-shaped gap. The pattern layer 5-2 had the independent pattern structure, and had an annular conductive pattern.
As details of parameters, a unit cell size Ux of each of the pattern layers 5-1 and 5-2 in the x-axis direction was 5.000 mm, and a unit cell size Uy in the y-axis direction was 5.000 mm. In the pattern layer 5-1, a length Lx of the cross shape in the x-axis direction was 2.397 mm, a length Ly of the cross shape in the y-axis direction was 2.397 mm, a width Wx of the cross shape in the x-axis direction was 0.291 mm, and a width Wy of the cross shape in the y-axis direction was 0.291 mm. In the pattern layer 5-2, an inner diameter R of the annular shape was 0.686 mm, and a width Wc of the annular shape was 0.295 mm.
When the frequency-selective reflecting member 4 was configured, 32 frequency-selective plates 1 were arranged in each of the x-axis direction and the y-axis direction such that the unit cells of the pattern layers 5-1 and 5-2 were aligned in a planar view, and a size on the xy plane was 160.00 mm × 160.00 mm.

FIG. 14 is graphs each illustrating transmission characteristics of the frequency-selective plate in Example 1. FIG. 14(a) illustrates a result when the x-axis polarized wave was applied from 0 degrees (θ_ix = 0°, θ_iy = 0°) and 45 degrees (θ_ix = 45°, θ_iy = 0°). FIG. 14(b) illustrates a result when the y-axis polarized wave was applied from 0 degrees (θ_ix = 0°, θ_iy = 0°) and 45 degrees (θ_ix = 45°, θ_iy = 0°). Analysis was performed on a structure in which the unit cells were infinitely arranged on the xy plane.

As illustrated in FIG. 13, since the pattern shape of each of the pattern layers 5-1 and 5-2 was line symmetrical about the x-axis and the y-axis, a result in a case of 0° incidence was equivalent between the both polarization directions. The transmission band was included in at least the 28 GHz band, the width of the first transmission band was ±1.4%, and the width of the second transmission band was ±3.2%. Further, the maximum transmittance in the transmission band was -1.3 dB.
Further, in a case of 45° incidence, a shift amount of the center wavelength in the first transmission band was 0.2% in the x-axis polarized wave, and was 0.6% in the y-axis polarized wave that were low values.

<Structure and Characteristics of Radio-Wave Reflecting Member>
The radio-wave reflecting member 3 was designed such that the radio wave of 28 GHz (wavelength of 10.7 mm) as a target was asymmetrically reflected at 0° incidence (θ_ix = 0°, θ_iy = 0°) and 45° reflection (θ_rx = 45°, θ_ry = 0°). The structure and the characteristics are described below.

FIG. 15 is a partial cross-sectional view of the radio-wave reflecting member in Example 1. The radio-wave reflecting member 3 was configured by stacking a ground layer 14, a dielectric layer 15, and element patterns 16 along the positive direction of the z-axis. The shape of the radio-wave reflecting member 3 on the xy plane was a square shape in which each side had a length of 60.56 mm, and each side was parallel to the x-axis or the y-axis. Copper having a thickness of 0.018 mm was used for the ground layer and the element patterns, and polystyrene resin having a thickness of 0.110 mm was used for the dielectric layer. An electric conductivity of copper was 5.8 × 10^7 siemens/m, a real part of a relative permittivity of the polystyrene resin was 2.428, and tand was 0.000667.

FIG. 16 is plan views each illustrating the radio-wave reflecting member in Example 1. 256 element patterns 16 in total were arranged along the x-axis direction and the y-axis direction while a distance between gravity centers was maintained to 3.785 mm (see FIG. 16(a)). Each of the element patterns 16 adopted a cross shape in which two rectangles were orthogonal to each other with a common gravity center on the xy plane, and the shapes of the element patterns 16 were slightly changed in the x-axis direction. More specifically, four element patterns adjacent in the x-axis direction were defined as one cycle (see FIG. 16(b)), and the four patterns defined as one cycle were relatedly arranged along the x-axis direction. In the y-axis direction, the element patterns having the same shape were arranged.

In a case where, in an n-th element pattern in the above-described one cycle, a long side of the cross shape in the x-axis direction was denoted by lxn, a short side was denoted by wxn, a long side of the cross shape in the y-axis direction was denoted by lyn, and a short side was denoted by wyn, shape parameters of each of the element patterns were lx1 = 3.500 mm, wx1 = 2.158 mm, ly1 = 3.500 mm, wy1 = 2.093 mm, lx2 = 3.500 mm, wx2 = 2.421 mm, ly2 = 3.500 mm, wy2 = 2.419 mm, lx3 = 3.500 mm, wx3 = 2.662 mm, ly3 = 3.500 mm, wy3 = 2.702 mm, lx4 = 3.500 mm, wx4 = 1.404 mm, ly4 = 3.500 mm, and wy4 = 1.398 mm.

FIG. 17 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to the radio-wave reflecting member in Example 1 at θ_ix = 0° and θ_iy = 0°. In a case of the radio wave of 28 GHz, reflection in a direction of θ_rx = 45° was observed. Even in a case of the radio waves of 27 GHz and 29 GHz that were shifted by ±1 GHz from 28 GHz, similar reflection characteristics were observed.

<Structure and Characteristics of Frequency-Selective Reflecting Member>
The frequency-selective reflecting member 4 was configured by assembling the above-described frequency-selective plate 1 and the above-described radio-wave reflecting member 3 with the functional gap 2 in between. Polystyrene foam in which a foaming rate was 80 times, and a real part of a relative permittivity and tand were both zero was applied to the functional gap 2. A size of the polystyrene foam on the xy plane was 160.00 mm × 160.00 mm that corresponded to the size of the frequency-selective plate 1. The polystyrene foam, the frequency-selective plate 1, and the radio-wave reflecting member 3 were stacked with the common gravity center on the xy plane. Further, the functional gap size was 0.09λ(0.96 mm) while a target wavelength λ(10.7 mm) was defined.

FIG. 18 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to the frequency-selective reflecting member in Example 1 at θ_ix = 0° and θ_iy = 0°. In the case of the radio wave of 28 GHz, reflection in the direction of θ_rx = 45° was observed. On the other hand, in the case of the radio waves of 27 GHz and 29 GHz that were shifted by ±1 GHz from 28 GHz, reflection in the direction of θ_rx = 45° was not observed, and reflection in a direction of θ_rx = 0° (regular reflection) was dominant. The frequency-selective reflecting performance calculated from the expression (8) was evaluated to be acceptable. The result indicated that the operation band of the frequency-selective reflecting member 4 was narrow as compared with the radio-wave reflecting member 3. Therefore, by using the frequency-selective reflecting member 4, influence applied to the bands around the target band can be reduced as compared with the existing technique.

In Example 2, only the functional gap size of the frequency-selective reflecting member in Example 1 was changed to 0.10λ(1.07 mm). The other configurations were similar to the configurations in Example 1. Thus, description thereof is omitted.
FIG. 19 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to the frequency-selective reflecting member in Example 2 at θ_ix = 0° and θ_iy = 0°. As in Example 1, in the case of the radio wave of 28 GHz, reflection in the direction of θ_rx = 45° was observed. On the other hand, in the case of the radio waves of 27 GHz and 29 GHz that were shifted by ±1 GHz from 28 GHz, reflection in the direction of θ_rx = 45° was not observed, and reflection in the direction of θ_rx = 0° (regular reflection) was dominant. The frequency-selective reflecting performance calculated from the expression (8) was evaluated to be acceptable. The result indicated that the effect of the frequency-selective reflecting member 4 was developed even in the case where the gap size was 0.10λ.

In Example 3, only the functional gap size of the frequency-selective reflecting member in Example 1 was changed to 0.93λ (10 mm). The other configurations were similar to the configurations in Example 1. Thus, description thereof is omitted.
FIG. 20 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to the frequency-selective reflecting member in Example 3 at θ_ix = 0° and θ_iy = 0°. As in Examples 1 and 2, in the case of the radio wave of 28 GHz, reflection in the direction of θ_rx = 45° was observed. On the other hand, in the case of the radio waves of 27 GHz and 29 GHz that were shifted by ±1 GHz from 28 GHz, reflection in the direction of θ_rx = 45° was not observed, and reflection in the direction of θ_rx = 0° (regular reflection) was dominant. The frequency-selective reflecting performance calculated from the expression (8) was evaluated to be acceptable. The result indicated that the effect of the frequency-selective reflecting member 4 was developed even in the case where the gap size was 0.93λ.

In Example 4, only the functional gap size of the frequency-selective reflecting member in Example 1 was changed to 4.67λ (50 mm). The other configurations were similar to the configurations in Example 1. Thus, description thereof is omitted.
FIG. 21 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to the frequency-selective reflecting member in Example 4 at θ_ix = 0° and θ_iy = 0°. As in Examples 1 to 3, in the case of the radio wave of 28 GHz, reflection in the direction of θ_rx = 45° was observed. On the other hand, in the case of the radio waves of 27 GHz and 29 GHz that were shifted by ±1 GHz from 28 GHz, reflection in the direction of θ_rx = 45° was not observed, and reflection in the direction of θ_rx = 0° (regular reflection) was dominant. The frequency-selective reflecting performance calculated from the expression (8) was evaluated to be acceptable. The result indicated that the effect of the frequency-selective reflecting member 4 was developed even in the case where the gap size was 4.67λ.

Example 5 that is an actual measurement result is described.
The structure of the frequency-selective plate 1 was the same as in Example 1 except that the thickness of the dielectric layer 6 was 0.115 mm, and a real part of a relative permittivity of the polystyrene resin was 2.42.
The details of the pattern layers 5-1 and 5-2 of the frequency-selective plate 1 were the same as in Example 1 except that, in the pattern layer 5-1 (see FIG. 13(a)), the length Lx of the cross shape in the x-axis direction was 2.551 mm, the length Ly of the cross shape in the y-axis direction was 2.551 mm, the width Wx of the cross shape in the x-axis direction was 0.243 mm, and the width Wy of the cross shape in the y-axis direction was 0.243 mm, and in the pattern layer 5-2 (see FIG. 13(b)), the inner diameter R of the annular shape was 0.610 mm, and the width Wc of the annular shape was 0.289 mm.
When the frequency-selective reflecting member 4 was configured, 20 frequency-selective plates 1 were arranged in each of the x-axis direction and the y-axis direction such that the unit cells of the pattern layers 5-1 and 5-2 were aligned in a planar view, and a size on the xy plane was 100 mm × 100 mm.
A bending elastic modulus of the frequency-selective plate 1 was measured.
Measurement Condition
Type of test: 3-point bending test
Model of universal tester: AG-10TD (manufactured by Shimazu Corporation)
Sample size: 30 mm × 60 mm
Load cell: 50 N
Test speed: 1 mm/min
Test result 9.7 GPa (average of results of three measurements)
The structure of the radio-wave reflecting member 3 was the same as in Example 1.

FIG. 22 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to the radio-wave reflecting member in Example 5 at θ_ix = 0° and θ_iy = 0°. In the case of the radio wave of 28 GHz, reflection in the direction of θ_rx = 45° was observed. Even in the case of the radio waves of 27 GHz and 29 GHz that were shifted by ±1 GHz from 28 GHz, similar reflection characteristics were observed.

Actual measurement of the reflection intensity in Example 5 was performed using a S-parameter S21 (dB). The S-parameter S21 indicates a ratio of reception power to transmission power irrespective of a far field and a near field. The S-parameter S21 measured in the near field was adopted because a reflection object and a reception antenna were not sufficiently separated in the actual measurement. On the other hand, an RCS is used as a physical amount indicating reflection characteristics of the reflection object in the far field where the reflection object and the reception antenna are sufficiently separated.
　As a specific measurement method, a reflection object to be measured was placed in a compact resin system, a planar wave was applied to the reflection object, and angular scanning was performed on the reception antenna on the xz plane separated by 0.5 m in radius from the reflection object to measure reflection intensity. In the compact resins system, a reflection mirror was installed in a radio wave darkroom, and an incident wave was converted from a spherical wave into a planar wave by the reflection mirror.

The frequency-selective reflecting member 4 was configured by assembling the above-described frequency-selective plate 1 and the above-described radio-wave reflecting member 3 with the functional gap 2 in between. The frequency-selective reflecting member 4 was the same as in Embodiment 1 except that the size of the functional gap 2 on the xy-plane was set to 100 mm × 100 mm that corresponded to the size of the frequency-selective plate 1. Further, the functional gap size was 4.67λ (50 mm) while a target wavelength λ (10.7 mm) was defined.

FIG. 23 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to the frequency-selective reflecting member in Example 5 at θ_ix = 0° and θ_iy = 0°. As in Examples 1 to 4, in the case of the radio wave of 28 GHz, reflection in the direction of θ_rx = 45° was observed. On the other hand, in the case of the radio waves of 27 GHz and 29 GHz that were shifted by ±1 GHz from 28 GHz, reflection in the direction of θ_rx = 45° was not observed. The frequency-selective reflecting performance calculated from the expression (8) was evaluated to be acceptable. It was confirmed from the result of the actual measurement that the effect of the frequency-selective reflecting member 4 was developed in the case where the gap size was 4.67λ.

Comparative Example 1

In Comparative example 1, only the functional gap size of the frequency-selective reflecting member in Example 1 was changed to 0.00λ (0.00 mm). The other configurations were similar to the configurations in Example 1. Thus, description thereof is omitted.
FIG. 24 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to the frequency-selective reflecting member in Comparative example 1 at θ_ix = 0° and θ_iy = 0°. Even in a case of any frequency, only reflection in the direction of θ_rx = 0° (regular reflection) occurred, and reflection in the direction of θ_rx = 45° (asymmetric reflection) did not occur. The frequency-selective reflecting performance calculated from the expression (8) was evaluated to be inacceptable. It is considered that this is because the functional gap 2 was absent, electric interaction between the frequency-selective plate 1 and the radio-wave reflecting member 3 was accordingly enhanced, and characteristics of the radio-wave reflecting member 3 were changed from original characteristics. Therefore, it was shown that, in the case where the functional gap 2 is absent, the effect of the frequency-selective reflecting member 4 is not developed.

Comparative Example 2

In Comparative example 2, only the functional gap size of the frequency-selective reflecting member in Example 1 was changed to 0.01λ (0.11 mm). The other configurations were similar to the configurations in Example 1. Thus, description thereof is omitted.
FIG. 25 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to the frequency-selective reflecting member in Comparative example 2 at θ_ix = 0° and θ_iy = 0°. Even in the case of any frequency, only reflection in the direction of θ_rx = 0° (regular reflection) occurred, and reflection in the direction of θ_rx = 45° (asymmetric reflection) did not occur. The frequency-selective reflecting performance calculated from the expression (8) was evaluated to be inacceptable. It is considered that this is because the functional gap size was excessively small, electric interaction between the frequency-selective plate 1 and the radio-wave reflecting member 3 was enhanced, or a wave surface of the radio wave immediately after the radio wave passed through the frequency-selective plate 1 was disturbed, and accordingly, characteristics of the radio-wave reflecting member 3 were changed from original characteristics. Therefore, it was shown that, in the case where the functional gap size is small as described above, the effect of the frequency-selective reflecting member 4 is not developed.

Comparative Example 3

In Comparative example 3, only the functional gap size of the frequency-selective reflecting member in Example 1 was changed to 0.05λ (0.54 mm). The other configurations were similar to the configurations in Example 1. Thus, description thereof is omitted.
FIG. 26 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to the frequency-selective reflecting member in Comparative example 3 at θ_ix = 0° and θ_iy = 0°. Even in the case of any frequency, only reflection in the direction of θ_rx = 0° (regular reflection) occurred, and reflection in the direction of θ_rx = 45° (asymmetric reflection) did not occur. The frequency-selective reflecting performance calculated from the expression (8) was evaluated to be inacceptable. It is considered that this is because the functional gap size was excessively small, electric interaction between the frequency-selective plate 1 and the radio-wave reflecting member 3 was enhanced, or a wave surface of the radio wave immediately after the radio wave passed through the frequency-selective plate 1 was disturbed, and accordingly, characteristics of the radio-wave reflecting member 3 were changed from original characteristics. Therefore, it was shown that, in the case where the functional gap size is small as described above, the effect of the frequency-selective reflecting member 4 is not developed.

Comparative Example 4

In Comparative example 4, only the functional gap size of the frequency-selective reflecting member in Example 1 was changed to 0.06λ (0.64 mm). The other configurations were similar to the configurations in Example 1. Thus, description thereof is omitted.
FIG. 27 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to the frequency-selective reflecting member in Comparative example 4 at θ_ix = 0° and θ_iy = 0°. The asymmetric reflection (θ_rx = 45°) occurred at the target frequency, but the asymmetric reflection also occurred at the off-target frequency. The frequency-selective reflecting performance calculated from the expression (8) was evaluated to be inacceptable. It is considered that this is because the functional gap size was excessively small, electric interaction between the frequency-selective plate 1 and the radio-wave reflecting member 3 was enhanced, or a wave surface of the radio wave immediately after the radio wave passed through the frequency-selective plate 1 was disturbed, and accordingly, characteristics of the radio-wave reflecting member 3 were changed from original characteristics. Therefore, it was shown that, in the case where the functional gap size is small as described above, the effect of the frequency-selective reflecting member 4 is not developed.

Comparative Example 5

In Comparative example 5, only the functional gap size of the frequency-selective reflecting member in Example 1 was changed to 0.07λ (0.75 mm). The other configurations were similar to the configurations in Example 1. Thus, description thereof is omitted.
FIG. 28 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to the frequency-selective reflecting member in Comparative example 5 at θ_ix = 0° and θ_iy = 0°. The asymmetric reflection (θ_rx = 45°) occurred at the target frequency, but the asymmetric reflection also occurred at the off-target frequency. The frequency-selective reflecting performance calculated from the expression (8) was evaluated to be inacceptable. It is considered that this is because the functional gap size was excessively small, electric interaction between the frequency-selective plate 1 and the radio-wave reflecting member 3 was enhanced, or a wave surface of the radio wave immediately after the radio wave passed through the frequency-selective plate 1 was disturbed, and accordingly, characteristics of the radio-wave reflecting member 3 were changed from original characteristics. Therefore, it was shown that, in the case where the functional gap size is small as described above, the effect of the frequency-selective reflecting member 4 is not developed.

Comparative Example 6

In Comparative example 6, only the functional gap size of the frequency-selective reflecting member in Example 1 was changed to 0.08λ (0.86 mm). The other configurations were similar to the configurations in Example 1. Thus, description thereof is omitted.
FIG. 29 is a graph illustrating reflection characteristics when the y-axis polarized wave is applied to the frequency-selective reflecting member in Comparative example 6 at θ_ix = 0° and θ_iy = 0°. The asymmetric reflection (θ_rx = 45°) occurred at the target frequency, but the asymmetric reflection also occurred at the off-target frequency. The frequency-selective reflecting performance calculated from the expression (8) was evaluated to be inacceptable. It is considered that this is because the functional gap size was excessively small, electric interaction between the frequency-selective plate 1 and the radio-wave reflecting member 3 was enhanced, or a wave surface of the radio wave immediately after the radio wave passed through the frequency-selective plate 1 was disturbed, and accordingly, characteristics of the radio-wave reflecting member 3 were changed from original characteristics. Therefore, it was shown that, in the case where the functional gap size is small as described above, the effect of the frequency-selective reflecting member 4 is not developed.

Table 1 summarizes the results in Examples and Comparative examples.
　Unit of reflection intensity in Examples 1 to 4 and Comparative examples 1 to 6 is dBsm.
　Unit of reflection intensity in Example 5 is dB.
　Frequencies a_28 GHz and b_28 GHz respectively correspond to a_tgt. and b_tgt. in the expression (8), and frequencies b_27 GHz and b_29 GHz both correspond to b_off-tgt.
　As obvious from Table 1, a significant difference of the frequency-selective reflecting performance is observed between the case where the functional gap size is 0.09λ or more and the case where the functional gap size is less than 0.09λ. It is found from the fact that, by providing the functional gap having the functional gap size of 0.09λ or more in the frequency-selective reflecting member having the target wavelength λ (mm), the effect of the frequency-selective reflecting member can be developed.

Although the embodiment of the present invention is described above, the present invention is not limited to the above-described embodiment, and can be variously changed without departing from the spirit of the present invention. For example, the frequency-selective plate is not limited to the frequency-selective plate that selectively allows the radio wave of the target wavelength to pass therethrough, and may be a frequency-selective plate that selectively reflects the radio wave of the target wavelength.

Aspects that may be included in the present invention are described below. However, the aspects are not limited thereto.
(Aspect 1)
A frequency-selective reflecting member, in which
a frequency-selective plate including a stacked body in which two or more pattern layers and one or more dielectric layers are alternately stacked, and a radio-wave reflecting member are assembled with a functional gap in between, and
a functional gap size is greater than or equal to G_min determined by an expression (1),
where λ (mm) is a target wavelength appropriately selected in a target band.
(Aspect 2)
The frequency-selective reflecting member according to aspect 1, in which
the frequency-selective plate includes a transmission band at least in a millimeter-wave band,
a width of a first transmission band is ±6.3% or less to a center wavelength, and
a width of a second transmission band is ±7.1% or less to the center wavelength.
(Aspect 3)
The frequency-selective reflecting member according to aspect 1, in which
the frequency-selective plate includes a transmission band at least in a millimeter-wave band,
a width of a first transmission band is ±1.8% or less to a center wavelength, and
a width of a second transmission band is ±2.3% or less to the center wavelength.
(Aspect 4)
　The frequency-selective reflecting member according to any one of aspects 1 to 3, in which a maximum transmittance in a transmission band of the frequency-selective plate is -3 dB or more.
(Aspect 5)
　The frequency-selective reflecting member according to any one of aspects 1 to 4, in which, in the frequency-selective plate, a shift amount of a center wavelength in a first transmission band is within 10% with respect to an incident angle of 0 degrees to 60 degrees.
(Aspect 6)
　The frequency-selective reflecting member according to any one of aspects 1 to 5, in which the frequency-selective plate includes a stacked body in which two pattern layers and one dielectric layer are alternately stacked.
(Aspect 7)
　The frequency-selective reflecting member according to any one of aspects 1 to 5, in which the frequency-selective plate includes a stacked body in which three pattern layers and two dielectric layers are alternately stacked.
(Aspect 8)
　The frequency-selective reflecting member according to any one of aspects 1 to 7, in which
　each of the pattern layers of the frequency-selective plate includes a conductive pattern and a gap, and has a continuous pattern structure that is a structure obtained by removing a specific shape from a uniform conductor or an independent pattern structure that is a structure in which conductors each having a specific shape are independently disposed like islands.
(Aspect 9)
　The frequency-selective reflecting member according to aspect 8, in which the frequency-selective plate includes a pattern layer having the continuous pattern structure and a pattern layer having the independent pattern structure.
(Aspect 10)
　The frequency-selective reflecting member according to aspect 9, in which
　the gap of the continuous pattern structure has a cross shape, and
　the conductive pattern of the independent pattern structure has an annular shape.
(Aspect 11)
　The frequency-selective reflecting member according to any one of aspects 8 to 10, in which, in the frequency-selective plate, a difference among occupancies of the conductive patterns of the pattern layers is 75 points or less.
(Aspect 12)
　The frequency-selective reflecting member according to any one of aspects 1 to 11, in which at least one of the pattern layers of the frequency-selective plate is sectioned into unit cells, and each unit cell has a pattern formed therein.
(Aspect 13)
　The frequency-selective reflecting member according to any one of aspects 1 to 12, in which a bending elastic modulus of the frequency-selective plate is 20 GPa or less.
(Aspect 14)
　The frequency-selective reflecting member according to any one of aspects 1 to 13, in which the frequency-selective plate has a curved surface shape.
(Aspect 15)
　The frequency-selective reflecting member according to any one of aspects 1 to 14, in which the frequency-selective plate includes a protective layer.
(Aspect 16)
　The frequency-selective reflecting member according to any one of aspects 1 to 15, in which the frequency-selective plate includes a design layer.
(Aspect 17)
　The frequency-selective reflecting member according to any one of aspects 1 to 16, in which the frequency-selective plate includes an installation layer.
(Aspect 18)
　The frequency-selective reflecting member according to any one of aspects 1 to 17, in which the functional gap size is equal to G_maxx and G_maxy respectively calculated from an expression (2) and an expression (3), or a smaller value of G_maxx and G_maxy or less.
(Aspect 19)
　A frequency-selective reflecting member with a radome obtained by assembling whole or a part of the frequency-selective reflecting member according to any one of aspects 1 to 18, in a radome.
(Aspect 20)
　The frequency-selective reflecting member with a radome according to aspect 19, further including radio wave absorbers on side surfaces of the radome.

1 Frequency-selective plate
2 Functional gap
3 Radio-wave reflecting member
4 Frequency-selective reflecting member
5 (5-1, ..., 5-n+1) Pattern layer
6 (6-1, ..., 6-n) Dielectric layer
7 Protective layer
8 Bonding layer
9 Installation layer
10 Design layer
11 Conductive pattern
12 Radome
13 Radio wave absorber
14 Ground layer
15 Dielectric layer
16 Element pattern

Claims

　A frequency-selective reflecting member, wherein
　a frequency-selective plate including a stacked body in which two or more pattern layers and one or more dielectric layers are alternately stacked, and a radio-wave reflecting member are assembled with a functional gap in between, and
　a functional gap size is greater than or equal to G_min determined by an expression (1),
where λ (mm) is a target wavelength appropriately selected in a target band.
　The frequency-selective reflecting member according to claim 1, wherein
　the frequency-selective plate includes a transmission band at least in a millimeter-wave band,
　a width of a first transmission band is ±6.3% or less to a center wavelength, and
　a width of a second transmission band is ±7.1% or less to the center wavelength.
　The frequency-selective reflecting member according to claim 1, wherein
　the frequency-selective plate includes a transmission band at least in a millimeter-wave band,
　a width of a first transmission band is ±1.8% or less to a center wavelength, and
　a width of a second transmission band is ±2.3% or less to the center wavelength.
　The frequency-selective reflecting member according to claim 1, wherein a maximum transmittance in a transmission band of the frequency-selective plate is -3 dB or more.
　The frequency-selective reflecting member according to claim 1, wherein, in the frequency-selective plate, a shift amount of a center wavelength in a first transmission band is within 10% with respect to an incident angle of 0 degrees to 60 degrees.
　The frequency-selective reflecting member according to claim 1, wherein the frequency-selective plate includes a stacked body in which two pattern layers and one dielectric layer are alternately stacked.
　The frequency-selective reflecting member according to claim 1, wherein the frequency-selective plate includes a stacked body in which three pattern layers and two dielectric layers are alternately stacked.
　The frequency-selective reflecting member according to claim 1, wherein
　each of the pattern layers of the frequency-selective plate includes a conductive pattern and a gap, and has a continuous pattern structure that is a structure obtained by removing a specific shape from a uniform conductor or an independent pattern structure that is a structure in which conductors each having a specific shape are independently disposed like islands.
　The frequency-selective reflecting member according to claim 8, wherein the frequency-selective plate includes a pattern layer having the continuous pattern structure and a pattern layer having the independent pattern structure.
　The frequency-selective reflecting member according to claim 9, wherein
　the gap of the continuous pattern structure has a cross shape, and
　the conductive pattern of the independent pattern structure has an annular shape.
　The frequency-selective reflecting member according to claim 8, wherein, in the frequency-selective plate, a difference among occupancies of the conductive patterns of the pattern layers is 75 points or less.
　The frequency-selective reflecting member according to claim 1, wherein at least one of the pattern layers of the frequency-selective plate is sectioned into unit cells, and each unit cell has a pattern formed therein.
　The frequency-selective reflecting member according to claim 1, wherein a bending elastic modulus of the frequency-selective plate is 20 GPa or less.
　The frequency-selective reflecting member according to claim 1, wherein the frequency-selective plate has a curved surface shape.
　The frequency-selective reflecting member according to claim 1, wherein the frequency-selective plate includes a protective layer.
　The frequency-selective reflecting member according to claim 1, wherein the frequency-selective plate includes a design layer.
　The frequency-selective reflecting member according to claim 1, wherein the frequency-selective plate includes an installation layer.
　The frequency-selective reflecting member according to claim 1, wherein the functional gap size is equal to G_maxx and G_maxy respectively calculated from an expression (2) and an expression (3), or a smaller value of G_maxx and G_maxy or less.
　A frequency-selective reflecting member with a radome obtained by assembling whole or a part of the frequency-selective reflecting member according to claim 1, in a radome.
　The frequency-selective reflecting member with a radome according to claim 19, further comprising radio wave absorbers on side surfaces of the radome.