Reflecting panel and electromagnetic wave reflecting device

Abstract

The invention provides a reflection panel and an electromagnetic wave reflection device which have the advantages of metasurface and specular reflection. The reflective panel is provided with: a first panel that specularly reflects an electromagnetic wave of a desired frequency band selected from a frequency band of 1 GHz to 300 GHz (inclusive); and a second panel having a metasurface in which reflection characteristics are controlled, and the interval between the first panel and the second panel in the direction perpendicular to the panel surface is at least 0.0 mm and less than 100.0 mm.

Description

Technical Field

[0001] The present invention relates to a reflection panel and an electromagnetic wave reflection device. Background Art

[0002] In the fifth-generation (hereinafter referred to as "5G") mobile communication standard, high-speed and large-capacity communication can be expected. However, since radio waves with strong directivity are used, there may be places where radio waves are difficult to reach. In places such as factories where there are a large number of metal machines, and places such as building blocks where there are many reflections from walls or street trees, a method for enabling radio waves to reach a target terminal device or wireless device is required. The same requirement also applies to places such as medical sites, event venues, and large commercial facilities where there are points (NLOS: Non-Line-Of-Sight) where the base station antenna cannot be seen. A structure in which an electromagnetic reflection device is arranged along at least a part of a production line has been proposed (for example, refer to Patent Document 1).

[0003] In recent years, a reflecting surface having an artificial surface called a "metasurface" has been developed. The metasurface is formed of periodic structures or patterns thinner than the wavelength and is designed to reflect radio waves in a desired direction (for example, refer to Non-Patent Document 1). Since the metasurface can achieve a desired reflection angle while maintaining a planar configuration structure, it can effectively function as a reflector even in an environment where there is not enough space to install a large number of electromagnetic wave reflection panels.

[0004] Patent Document 1: International Publication No. 2021 / 199504

[0005] Non-Patent Document 1: Diaz-Rubio et al., Sci.Adv.2017:3:e1602714 1 Summary of the Invention

[0006] Generally speaking, the larger the size of the reflector, the greater the gain, and the better the radio wave reflection effect and the improvement effect of the propagation environment. However, the reflector of the metasurface requires precise processing of a metal layer and a resin layer smaller than the wavelength of the radio waves of 5G, and the general size is about 150 mm to 500 mm on each side. In addition, different from the mirror reflection surface, it is difficult for the metasurface to make the electrode reflection efficiency close to 100%. For these reasons, sometimes the reflection efficiency and the propagation environment cannot be sufficiently improved only by the reflector of the metasurface. On the other hand, for the reflector using mirror reflection, there are many material options for the conductive layer as the functional layer, and there are also fewer size restrictions. In the case of mirror reflection, a large-sized panel can be easily manufactured, and the reflection characteristics are also good, and a sufficient propagation environment improvement effect can be produced. However, due to the positional relationship with the base station, it can only reflect in the direction of regular reflection and cannot control the reflection angle, so the installation location is easily limited. One of the purposes of the present invention is to provide a reflection panel and an electromagnetic wave reflection device that combine the advantages of the metasurface and mirror reflection.

[0007] In one embodiment, the reflection panel has:

[0008] a first panel that performs mirror reflection on electromagnetic waves in a desired frequency band selected from the frequency band of 1 GHz or higher and 300 GHz or lower; and

[0009] a second panel having a metasurface with controlled reflection characteristics,

[0010] The distance between the first panel and the second panel in the direction perpendicular to the panel surface is 0.0 mm or more and less than 100.0 mm.

[0011] A reflection panel and an electromagnetic wave reflection device that combine the advantages of the metasurface and mirror reflection are realized. Description of the Drawings

[0012] Figure 1 is a schematic diagram of an electromagnetic wave reflection device using the reflection panel of the embodiment.

[0013] Figure 2 is a side view of the reflection panel.

[0014] Figure 3 is a schematic diagram of an electromagnetic wave reflection fence formed by combining multiple electromagnetic wave reflection devices.

[0015] Figure 4A is a perspective view showing an example of a holding portion that holds the second panel.

[0016] Figure 4B is Figure 4A a side view schematic diagram of

[0017] Figure 5This is a diagram showing another example of the holding part for holding the second panel.

[0018] Figure 6 This is a diagram showing Figure 5 a structural example of a frame for holding the second panel in

[0019] Figure 7 This is a diagram showing the holding state of adjacent reflective panels held by a frame.

[0020] Figure 8 This is a diagram showing yet another example of the holding part for holding the second panel.

[0021] Figure 9 This is a schematic diagram of the layer structure of the first panel.

[0022] Figure 10 This is a plan schematic diagram of the metasurface of the second panel.

[0023] Figure 11 This is a diagram showing an example of a unit pattern constituting the metasurface.

[0024] Figure 12 This is a schematic diagram of the layer structure of the second panel.

[0025] Figure 13 This is a diagram showing the analysis space of the second panel. Detailed implementation mode

[0026] In the implementation mode, a reflective panel that combines the advantages of both a metasurface and specular reflection is achieved by combining the first panel that utilizes specular reflection and the second panel of the metasurface. The first panel that utilizes specular reflection does not require fine pattern processing and is easy to fabricate into a large-area panel. The second panel with a metasurface is disposed on one surface of the first panel. The second panel is disposed at a prescribed interval, specifically an interval of 0.0 mm or more and less than 100.0 mm, from the surface of the first panel on the incident side of the electromagnetic wave to the first panel. When observed from the electromagnetic wave incident on the first panel, the second panel is located in front of the first panel.

[0027] The second panel is preferably held so as to be movable or detachable on the incident surface side of the first panel, and the second panel can be installed according to the installation location of the reflective panel, and the position of the second panel can be adjusted above the first panel. The planar size of the second panel can also be smaller than that of the first panel, and a plurality of second panels can be disposed on the incident surface side of the first panel.

[0028] Hereinafter, with reference to the drawings, the structure of the reflection panel of the embodiment and the electromagnetic wave reflection device using the reflection panel will be described. The following-described embodiment is an example for embodying the technical idea of the present invention and does not limit the present invention. For ease of understanding of the invention, the sizes, positional relationships, etc. of the respective components shown in the respective drawings are sometimes exaggerated. In the following description, the same names or reference numerals are given to the same components or functions, and repeated descriptions are sometimes omitted.

[0029] <Structure of Reflection Panel and Electromagnetic Wave Reflection Device>

[0030] Figure 1 is a schematic diagram of an electromagnetic wave reflection device 60 using the reflection panel 30 of the embodiment, Figure 2 is a side view of the reflection panel 30. In Figure 1 and Figure 2 coordinate systems, the plane on which the electromagnetic wave reflection device 60 is provided is set as the XY plane, the height direction orthogonal to the XY plane is set as the Z direction, and the thickness direction of the reflection panel 30 is set as the Y direction. The electromagnetic wave reflection device 60 is provided at a desired location indoors and outdoors and reflects electromagnetic waves of a specified frequency selected from a frequency band of 1 GHz or higher and 300 GHz or lower, and as an example, from 1 GHz or higher and 170 GHz or lower, by the reflection panel 30.

[0031] The reflection panel 30 has: a first panel 10 that uses specular reflection; and a second panel 20 that has a metasurface with controlled reflection characteristics. The interval G in the direction perpendicular to the panel surface between the first panel and the second panel is 0.0 mm or more and less than 100.0 mm. When the interval G is 0.0 mm, the second panel 20 is in contact with the surface of the first panel 10. The state where the first panel 10 is in contact with the second panel 20 means a state where there is no air layer that substantially changes the dielectric constant between the two panels, and the gaps caused by the microscopic unevenness of the panel surface can be ignored. The metasurface with controlled reflection characteristics reflects the incident electromagnetic waves at a reflection angle different from the incident angle. In a good structural example, the second panel 20 is supported relative to the first panel 10 so as to be movable or detachable. For example, the second panel 20 is suspended by a transparent fishing line or a polymer wire and is arranged at a desired position within the plane of the first panel 10 within the above interval G. A specific example of the holding structure of the second panel 20 relative to the first panel 10 will be described later.

[0032] The electromagnetic wave reflection device 60 has a reflection panel 30 and a frame 50 that holds the reflection panel 30. The frame 50 holds both ends of the first panel 10 of the reflection panel 30. The electromagnetic wave reflection device 60 may also have a top frame 57 that holds the upper end of the reflection panel 30 and a bottom frame 58 that holds the lower end. The entire perimeter of the reflection panel 30, more specifically, the entire perimeter of the first panel 10, is held by the frame 50, the top frame 57, and the bottom frame 58. Due to its positional relationship with respect to the top frame 57 and the bottom frame 58, the frame 50 may also be referred to as a "side frame". Although the top frame 57 and the bottom frame 58 are not essential, by providing the top frame 57 and the bottom frame 58, the mechanical strength and safety during the handling, assembly, installation of the first panel, and the installation of the second panel 20 can be ensured.

[0033] When the electromagnetic wave reflection device 60 is made to stand independently indoors or outdoors, feet 56 may be provided. Although in Figure 1 's example, the feet 56 support the lower end of the frame 50, the feet 56 may also be connected to the bottom frame 58. It may also be configured such that the feet 56 can be fixed to the ground or road surface through components such as screws. Movable components such as casters may also be provided on the feet 56 so that it can be moved to the installation location. Instead of providing the feet 56, the entire perimeter of the reflection panel 30 may be surrounded by a frame and inclinedly installed with respect to walls, ceilings, floors, etc.

[0034] As Figure 2 shown, the second panel 20 of the reflection panel 30 is arranged at a prescribed interval G in a direction perpendicular to the panel surface with respect to the first panel 10. The interval G is set in the range of 0.0 mm or more and less than 100.0 mm from the viewpoint of maintaining a high power reflection efficiency of the reflection panel 30. If the interval G is 100.0 mm or more, reflection, scattering, etc. occur in the space between the first panel 10 and the second panel 20, resulting in a decrease in the power reflection efficiency of the second panel 20. As a result, the power reflection efficiency of the entire reflection panel 30 decreases beyond the allowable range. The details of this basis will be described later.

[0035] In order to movably hold the second panel 20 on the surface of the first panel 10, it is preferable to minimize the physical contact between the first panel 10 and the second panel 20 during the movement of the position of the second panel 20. After the position of the second panel 20 is determined, the second panel 20 may be brought into contact with the first panel 10 for holding. This is because the thinner the air layer between the first panel 10 and the second panel 20, the less the influence on the designed reflection characteristics of the second panel 20.

[0036] Figure 3 is a schematic diagram of an electromagnetic wave reflection fence 100 formed by connecting a plurality of electromagnetic wave reflection devices 60. InFigure 3 In the example, the electromagnetic wave reflection devices 60-1, 60-2, and 60-3 are connected in the lateral (X) direction by the frame 50. The electromagnetic wave reflection devices 60-1, 60-2, and 60-3 each have reflection panels 30-1, 30-2, and 30-3 (sometimes collectively referred to as "reflection panel 30" as appropriate). In the reflection panel 30-1 and the reflection panel 30-2, a second panel 20-1 and a second panel 20-2 are respectively installed on the first panel 10-1 and the first panel 10-2. The second panel 20-1 and the second panel 20-2 can be installed at the same position on the first panel 10-1 and the first panel 10-2 according to the incoming direction and the direction to be reflected of the electromagnetic wave, or can be installed at different positions. The planar (length × width) dimension and the reflection characteristics of the second panel 20-1 can be the same as or different from those of the second panel 20-2. If the dimension of the panel is defined by length × width × thickness, the planar dimension refers to the length × width dimension. The planar dimension of the first panel 10 also represents the length × width size of the panel.

[0037] Although the reflection panel 30-3 of the electromagnetic wave reflection device 60-3 is used in a state where the second panel 20 is removed, the second panel 20 can also be installed at a desired position on the first panel 10-3 in the same manner as the reflection panels 30-1 and 30-2. The number of the connected electromagnetic wave reflection devices 60 is not limited to three, and an electromagnetic wave reflection fence 100 formed by connecting two devices can be assembled, or four or more devices can be connected. Preferably, when connecting a plurality of electromagnetic wave reflection devices 60 in the lateral (X) direction, at least a part of the frame 50 is formed by a conductor to make the reflection potential continuous between the adjacent first panel 10-1 and the first panel 10-2, or between the first panel 10-2 and the first panel 10-3.

[0038] A plurality of independent electromagnetic wave reflection devices 60 that are not connected can also be arranged in a desired orientation to surround a desired space. A single electromagnetic wave reflection device 60 and an electromagnetic wave reflection fence 100 can also be combined, or two or more electromagnetic wave reflection fences 100 can be combined to form a specified space. In any case, the second panel 20 can be arranged at a desired position above the desired first panel 10.

[0039] <Retention structure of the second panel>

[0040] Figure 4A is a perspective view of the reflection panel 30A having a retention portion 31A for retaining the second panel 20, Figure 4B is Figure 4ASide view. The holding part 31A has a first part 311 that can move in the first direction of the first panel 10, and a second part 312 that supports the second panel 20 and can change its length in the second direction of the first panel 10. The first part 311 is movably mounted at a desired position on the edge of the first panel 10. The first part 311 has a hook shape that hooks onto the upper end of the first panel 10 or the top frame 57A, and can slide in the lateral direction (X direction) of the reflecting panel 30A.

[0041] The second part 312 extends from the end of the first part 311 on the side opposite to the hook, and supports the second panel 20. The end of the second part 312 is fitted into a hole or slit 21 (hereinafter simply referred to as "hole 21") provided in the second panel 20 to support the second panel 20. The fitting portion of the hole 21 and the second part 312 can also be strengthened by an adhesive. The second part 312 can slide relative to the first part 311 in the second direction (in this example, the Z direction), whereby the holding part 31A can change its length in the Z direction. A lock or latch can also be provided at regular intervals on the second part 312. For ease of illustration, the first part 311 and the second part 312 are depicted as first-stage sliding members, but they can also be second-stage or higher-stage sliding members. For example, the second part 312 can be configured as a hollow housing structure, and a rod of the third part can slide inside the second part 312.

[0042] The entire holding part 31A is transparent with respect to the wavelength of the electromagnetic wave reflected by the first panel 10 and the second panel 20. The first part 311 and the second part 312 of the holding part 31A preferably have the same dielectric constant and dielectric loss tangent as the dielectric layer used for the first panel 10 and the second panel 20, so as to minimize the influence on the reflection characteristics of the first panel 10 and the second panel 20. Even when an adhesive is applied to the fitting portion, the adhesive preferably has the same dielectric constant and dielectric loss tangent as the dielectric layer of the first panel 10 and the second panel 20.

[0043] Although in Figure 4A and Figure 4B the example shown, the holding part 31A hooks onto the top frame 57A, it can also be on the bottom frame 58 (refer to Figure 1)The guide rail for holding the first part 311 is set to be slidable. In this case, the second part 312 supports the second panel 20 from below and extends in the height (+Z) direction. Alternatively, the holding part 31A can also be formed to be slidable relative to the frame 50 that holds the side edge of the reflective panel 30A. In this case, the first part 311 slides in the longitudinal direction of the reflective panel 30A, and the second part 312 expands and contracts in the transverse direction of the reflective panel 30A. Regardless of which structure, the second panel 20 is held movably relative to the first panel 10.

[0044] In Figure 4A and Figure 4B In the structural example, the interval G between the first panel 10 and the second panel is determined by the thickness of the top frame 57A and the thickness of the first part 311 of the holding part 31A. It is also possible to pre-measure the interval at which the power reflection efficiency is optimal with respect to the operating frequency and design the thickness of the top frame 56A and the thickness of the first part 311. By using the holding part 31A, the first panel 10 and the second panel 20 can be carried separately during handling, and the second panel 20 can be assembled relative to the first panel 10 at a desired position on-site.

[0045] Figure 5 The holding part 31B for holding the second panel 20 is shown. The holding part 31B has a first part 313 that can move in the first direction of the first panel 10, and a second part 312 that supports the second panel 20 and can change its length in the second direction of the first panel 10. In Figure 5 In the example, the first part 313 has a hook shape that can be slidably hooked in the slit 522 of the top frame 57B that covers the upper end of the first panel 10.

[0046] The second part 312 extends from the end of the first part 313 on the side opposite to the hook and supports the second panel 20. The end of the second part 312 is fitted into the hole 21 provided in the second panel 20 to support the second panel 20. The fitting part between the hole 21 and the second part 312 can also be strengthened with an adhesive. The second part 312 can slide relative to the first part 313 in the height direction (Z direction), whereby the holding part 31B can change its length in the Z direction. Locks or latches can also be provided at regular intervals on the second part 312.

[0047] The entire holding portion 31B is transparent with respect to the electromagnetic waves reflected by the first panel 10 and the second panel 20. The first portion 313 and the second portion 312 of the holding portion 31A preferably have the same dielectric constant and dielectric loss tangent as the dielectric layer used for the first panel 10 and the second panel 20, minimizing the influence on the reflection characteristics of the first panel 10 and the second panel 20. Even when an adhesive is applied to the fitting portion, the adhesive preferably has the same dielectric constant and dielectric loss tangent as the dielectric layer of the first panel 10 and the second panel 20.

[0048] Although in Figure 5 the example, the holding portion 31B is hooked on the slit 522 of the top frame 57B and can slide in the X direction, a guide rail for sliding the first portion 313 can be provided on the bottom frame 58, or it can be formed to be able to slide relative to the frame 50 that holds the side edges of the reflection panel 30B. By using the holding portion 31B, the first panel 10 and the second panel 20 can be carried separately during handling, and the second panel 20 can be assembled relative to the first panel 10 at a desired position on-site.

[0049] Figure 6 Shows a structural example of the top frame 57B. This figure is a cross-sectional view taken along the Figure 5 YZ plane. The top frame 57B has a main body 520, slits 521 and 522 formed on both sides in the long axis direction of the main body 520, chambers 523 and 524 communicating with the slits 521 and 522 respectively, and grooves 525 and 526 provided in the chambers 523 and 524. The upper end of the first panel 10 is inserted into the slit 521 and fixed by being fitted into the groove 525. The opposite slit 522 is used as a guide rail for sliding the first portion 313 of the holding portion 31B. The top frame 57B can also be of the same shape as the frame 50 that holds adjacent reflection panels 30 to each other.

[0050] Figure 7 Shows the state where the first panel 10-1 and the first panel 10-2 adjacent to each other are held by a frame 50 having the same shape as the top frame 57B. The first panel 10-1 and the first panel 10-2 are inserted deep into the grooves 525 and 526 (refer to Figure 6 ) and stably held. From the viewpoint of making the reflection potentials of the adjacent first panel 10-1 and the first panel 10-2 continuous, at least a part of the frame 50, particularly the central part of the main body 520 extending between the grooves 525 and 526, is formed of a good conductor. In contrast, the top frame 57B that receives the holding portion 31B can also be entirely formed of a non-conductor such as resin.

[0051] By using the top frame 57B to install the holding part 31B, the second panel 20 can be held in an adjustable position relative to the first panel 10. The first panel 10 and the second panel 20 can be carried separately during transportation, and the second panel 20 can be assembled relative to the first panel 10 at a desired position on site.

[0052] Figure 8 Indicates the holding part 31C for holding the second panel 20. The holding part 31C has a first part 315 that can move in the first direction of the first panel 10, a second part 312 that extends from the end of the first part 315 and can change its length in the second direction of the first panel 10, and a socket 34 that holds the second panel 20 at the end of the second part 312. The first part 315 is movably installed at a desired position on the edge of the first panel 10. In Figure 8 the example, the first part 315 has a hook shape that can be slidably hooked on the slit 522 of the top frame 57B covering the upper end of the first panel 10.

[0053] The second part 312 extends from the end of the first part 315 opposite to the hook, and the length in the major axis direction can be changed. The end of the second part 312 and the upper end of the second panel 20 are supported by the socket 34. The second part 312 can slide relative to the first part 315 in the height direction (Z direction), whereby the holding part 31B can change its length in the Z direction. Locks or latches can also be provided at regular intervals on the second part 312.

[0054] The entire holding part 31C including the socket 34 is transparent to the electromagnetic waves reflected by the first panel 10 and the second panel 20. The first part 315, the second part 312, and the socket 34 of the holding part 31C preferably have the same dielectric constant and dielectric loss tangent as the dielectric layer used for the first panel 10 and the second panel 20, minimizing the influence on the reflection characteristics of the first panel 10 and the second panel 20.

[0055] Although in Figure 8 the example, the holding part 31C is hooked on the slit 522 of the top frame 57B and can slide in the X direction, a guide rail for sliding the first part 315 can be provided on the bottom frame 58, or it can be formed to be slidable relative to the frame 50 that holds the side edge of the reflective panel 30C. By using the holding part 31C, the first panel 10 and the second panel 20 can be carried separately during transportation, and the second panel 20 can be assembled relative to the first panel 10 at a desired position on site.

[0056] Although in Figures 4A to 8In this case, the holding portion 31 is installed using the top frame 57, the bottom frame 58, or the frame 50 that surrounds the reflection panel 30. However, if there are no problems with the strength and safety of the reflection panel 30, the holding portion 31 can also be directly installed on the edge of the reflection panel 30.

[0057] <Layer Structure of Reflection Panel>

[0058] Figure 9 This shows the layer structure in the thickness direction (Y direction) of the first panel 10. The first panel 10 includes a conductive layer 11 and a dielectric layer 14 or 15 that is joined to at least one surface of the conductive layer 11 via an adhesive layer 12 or 13. In Figure 9 In the example, the conductive layer 11 is sandwiched between the dielectric layers 14 and 15 via the adhesive layers 12 and 13.

[0059] The conductive layer 11 is the surface that forms the reflection surface of the first panel 10 and is formed of a metal material suitable for specular reflection. As the material of the conductive layer 11, good conductors such as Cu, Ni, SUS, Ag, and Au can be used. The conductive layer 11 has a thickness of 10 μm or more and 200 μm or less, preferably 50 μm or more and 150 μm or less, so as to function sufficiently as a reflection surface for specularly reflecting electromagnetic waves of the target frequency.

[0060] In order to guide the incident electromagnetic waves to the conductive layer 11, the transmittance of the adhesive layer 12 and the adhesive layer 13 with respect to the operating frequency is 60% or more, preferably 70% or more, more preferably 80% or more. The adhesive layer 12 and the adhesive layer 13 can also be formed of vinyl acetate resin, acrylic resin, cellulose resin, aniline resin, ethylene resin, silicone resin, or other resin materials. When the adhesive layer 12 and the adhesive layer 13 are to have durability and moisture resistance that can withstand outdoor use, ethylene-vinyl acetate (EVA) copolymer or cycloolefin polymer (COP) can also be used. The thickness of the adhesive layers 12 and 13 is a thickness that can reliably bond and hold the dielectric layers 14 and 15 to the conductive layer 11, for example, 10 μm or more and 400 μm or less. The adhesive layer 12 and the adhesive layer 13 have a relative dielectric constant and a dielectric loss tangent suitable for achieving the target reflection characteristics based on the conductive layer 11.

[0061] The dielectric layer 14 and the dielectric layer 15 are insulating polymer films such as polycarbonate, cycloolefin polymer (COP), polyethylene terephthalate (PET), and fluororesin. In order to make the total amount of the first panel 10 as light as possible while maintaining the strength of the first panel 10, the thicknesses of the dielectric layer 14 and the dielectric layer 15 can be selected in the range greater than 1.0 mm and 10.0 mm or less. If the thickness of the conductive layer 11 is set to 100.0 μm, the ratio of the thicknesses of the dielectric layer 14 and the dielectric layer 15 to the thickness of the conductive layer 11 is greater than 10 and 80 or less. By setting the ratio of the thicknesses of the dielectric layer 14 and the dielectric layer 15 to the thickness of the conductive layer 11 within this range, the first panel 10 has mechanical strength sufficient to withstand outdoor use and can achieve the target reflection characteristics. In a situation where mechanical strength is prioritized, the ratio of the dielectric material to the thickness of the conductive layer 11 can also be increased within a range that does not hinder the reflection characteristics.

[0062] Figure 10 Shows the layer structure in the thickness direction (Y direction) of the second panel 20. The second panel 20 has a dielectric layer 215, a conductive layer 214 held on one surface of the dielectric layer 215 through an adhesive layer 213, and a protective layer 212 covering the conductive layer 214. The dielectric layer 215 is an insulating polymer film such as polycarbonate, cycloolefin polymer (COP), polyethylene terephthalate (PET), and fluororesin, and has a thickness of about 0.3 mm to 1.0 mm. The dielectric layer 215 may be any material with a relative permittivity and a dielectric loss tangent suitable for achieving the target reflection characteristics. A ground layer 216 is formed on the surface of the dielectric layer 215 opposite to the conductive layer 214.

[0063] The conductive layer 214 forms the metasurface of the second panel 20, that is, the surface whose reflection characteristics are artificially controlled. The conductive layer 214 has a predetermined pattern formed by metal patches 211 made of a good conductor such as Cu, Ni, Ag, Au, etc. The thickness of the conductive layer 214 is such that it can reflect incident electromagnetic waves in the designed direction with sufficient strength. For example, it has a thickness of 10 μm to 50 μm. The adhesive layer 213 is a material capable of carrying and fixing the metal patches 211 to the dielectric layer 215, and thermoplastic resins such as vinyl acetate resin, acrylic resin, cellulose resin, and silicone resin can also be used. The thickness of the adhesive layer 213 is about 5 μm to 50 μm.

[0064] The protective layer 212 covering the conductive layer 214 preferably has durability and moisture resistance, and for example, ethylene-vinyl acetate (EVA) copolymer or cycloolefin polymer (COP) can be used. The thickness of the protective layer 212 is 10 μm to 400 μm. The protective layer 212 can also be formed by an adhesive layer to fix a dielectric substrate such as polycarbonate to the surface of the protective layer 212.

[0065] <Evaluation of the Reflective Panel>

[0066] Combination Figure 9 The first panel 10 shown and Figure 10 The second panel 20 shown are used to evaluate the reflection characteristics of the reflective panel 30. It can be inferred that the interval G between the first panel 10 and the second panel 20, that is, the thickness of the air layer, affects the characteristics of the reflective panel 30. The reflection characteristics are evaluated by varying the interval G in various ways.

[0067] Figure 11 A model representing the conductive pattern of the conductive layer 214 for the second panel 20. The model for evaluating the conductive layer 214 includes a periodic arrangement of unit cells (also referred to as "super cells") 210. The unit cells 210 are arranged in 6 rows in the X direction and 36 rows in the Z direction to form a metasurface that reflects electromagnetic waves at an angle different from the incident angle. The X direction and the Z direction are Figure 1 the same as the X direction and the Z direction of

[0068] Figure 12 It is a schematic diagram showing the structure of the unit cell 210. The unit cell 210 is formed by six metal patches 211a, 211b, 211c, 211d, 211e, and 211f (sometimes collectively referred to as "metal patches 211" appropriately). The widths (W) of the metal patches 211a to 211f are equal, and the lengths (L) are different respectively, but the central axes of the lengths (L) are aligned. The pitch in the X direction is constant. The phase of the reflection is controlled by the shapes, sizes, and the intervals in the X direction of the metal patches 211a to 211f, and a reflected light beam is formed in a desired direction by the overlap of the reflected waves. In this example, the peak of the reflected wave of the electromagnetic wave designed to be perpendicularly incident (incident angle 0°) appears in the direction 50° from the normal.

[0069] In the evaluation method, relative to Figure 9 the first panel 10, it is held at a prescribed interval G Figures 10 to 12The second panel 20 shown. Using general three-dimensional electromagnetic field simulation software, a plane wave of 28.0 GHz is incident at an incident angle of 0°, and the scattering cross-sectional area of the reflected wave is analyzed. The scattering cross-sectional area, that is, the radar cross section (RCS: Rader Cross Section), is used as an index representing the ability to reflect incident electromagnetic waves.

[0070] In the case of a metasurface that reflects at a reflection angle different from the incident angle, the calculated power reflection efficiency needs to be corrected. The first panel 10 has a specular reflection surface and reflects electromagnetic waves in the same direction with respect to normal incidence. In contrast, the metasurface of the second panel 20 reflects electromagnetic waves in a direction different from the incident angle. The power reflection efficiency of the metasurface is a value obtained by dividing the power reflection efficiency obtained from the gain value by the correction value. From the viewpoint of improving the radio wave environment using the reflection panel 30, the power reflection efficiency is 65% or more, preferably 70% or more, and more preferably 75%. When the power reflection efficiency is less than 65%, it is difficult to obtain a sufficient effect of improving the radio wave environment.

[0071] If the reflected electric field on the lossless metasurface determined by the Figure 11 model pattern is set as E MR , and the reflected electric field on the ideal conducting plate is set as E PEC , then the correction value ε p is set as |E MR / E PEC | 2 . |E MR / E PEC | is expressed as

[0072]

[0073] Or is expressed as

[0074]

[0075] Here, θ is the incident angle to the metasurface, is the reflection angle in the case of equivalent normal reflection. If the reflection angle of the metasurface is set as θ = 50° or θr = 50°, and the incident angle is set as θi = 0°, the reflection angle of normal reflection, then the correction value ε p is 0.7826.

[0076] Figure 13 Denotes the analysis space 101 for electromagnetic wave simulation. Set the thickness direction of the Figure 10 layer structure as the Y direction, and set the Figure 11The width direction of the metal patch 211 of the model is set as the X direction, and the length direction is set as the Z direction. The analysis space 101 is expressed as (dimension in the X direction) × (dimension in the Z direction) × (dimension in the Y direction). When the frequency of the incident electromagnetic wave is 28.0 GHz, the dimensions of the analysis space 101 are 83.9 mm × 192.6 mm × 3.7 mm. The boundary condition is the design where electromagnetic wave absorbers 102 are arranged around the analysis space 101.

[0077] <Example 1>

[0078] Example 1 is Example 1. As the first panel 10, a panel with a planar size of 1.0 m in length and 2.0 m in width and having Figure 9 a layer structure is used. As the outermost dielectric layers 14 and 15, polycarbonate sheets with a length of 1.0 m, a width of 2.0 m, and a thickness of 2.0 mm are used. Through adhesive layers 12 and 13 made of ethylene-vinyl acetate with a thickness of 400 μm, two polycarbonate sheets are bonded to both sides of a conductive layer 11 formed by a stainless-steel mesh with a thickness of 100 μm.

[0079] As the second panel 20, a panel with a planar size of 0.7 m in length and 0.7 m in width and having Figure 10 a layer structure and Figure 11 a conductive pattern is used. As the dielectric layer 215, a polycarbonate sheet with a length of 0.7 m, a width of 0.7 m, and a thickness of 0.7 mm is used. On one side of the polycarbonate sheet, a ground layer 216 is set with an Ag-based multilayer film having a thickness of 0.36 mm. On the other side of the polycarbonate sheet, via an adhesive layer 213 with a thickness of 0.01 mm, a conductive layer 214 including a metal patch 211 formed by a copper foil with a thickness of 0.03 mm is set. A protective layer 212 made of EVA with a thickness of 400 μm is set to cover the conductive layer 214.

[0080] With respect to the first panel 10, the second panel 20 is arranged at an interval G = 0.0 mm. The gain value (peak of the reflection waveform) at 50° of the RCS curve when the electromagnetic wave incident at an incident angle of 0° is reflected at a reflection angle of 50° is -1.5297 dB. The power reflection efficiency after correcting this gain value with a correction value ε p = 0.7826 is 77.2%. When the interval G is 0.0 mm, a high power reflection efficiency exceeding 75% can be obtained.

[0081] <Example 2>

[0082] Example 2 is Embodiment 2. The structures and shapes of the first panel 10 and the second panel 20 are the same as those in Example 1. The second panel 20 is arranged at an interval G = 1.0 mm with respect to the first panel 10. The gain value (peak of the reflection waveform) at 50° of the RCS curve when the electromagnetic wave incident at an incident angle of 0° is reflected at a reflection angle of 50° is -1.4541 dB. After correcting this gain value with the correction value ε p = 0.7826, the power reflection efficiency is 78.5%. When the interval G is 1.0 mm, a high power reflection efficiency exceeding 75% can be obtained.

[0083] <Example 3>

[0084] Example 3 is Embodiment 3. The structures and shapes of the first panel 10 and the second panel 20 are the same as those in Example 1. The second panel 20 is arranged at an interval G = 5.0 mm with respect to the first panel 10. The gain value (peak of the reflection waveform) at 50° of the RCS curve when the electromagnetic wave incident at an incident angle of 0° is reflected at a reflection angle of 50° is -1.7936 dB. After correcting this gain value with the correction value ε p = 0.7826, the power reflection efficiency is 72.6%. When the interval G is 5.0 mm, a high power reflection efficiency exceeding 70% can be obtained.

[0085] <Example 4>

[0086] Example 4 is Embodiment 4. The structures and shapes of the first panel 10 and the second panel 20 are the same as those in Example 1. The second panel 20 is arranged at an interval G = 10.0 mm with respect to the first panel 10. The gain value (peak of the reflection waveform) at 50° of the RCS curve when the electromagnetic wave incident at an incident angle of 0° is reflected at a reflection angle of 50° is -1.7661 dB. After correcting this gain value with the correction value ε p = 0.7826, the power reflection efficiency is 73.1%. When the interval G is 10.0 mm, a high power reflection efficiency exceeding 70% can be obtained.

[0087] <Example 5>

[0088] Example 5 is Embodiment 5. The structures and shapes of the first panel 10 and the second panel 20 are the same as those in Example 1. The second panel 20 is arranged at an interval G = 20.0 mm with respect to the first panel 10. The gain value (peak of the reflection waveform) at 50° of the RCS curve when the electromagnetic wave incident at an incident angle of 0° is reflected at a reflection angle of 50° is -1.4887 dB. After correcting this gain value with the correction value ε p = 0.7826, the power reflection efficiency is 77.9%. When the interval G is 20.0 mm, a high power reflection efficiency exceeding 75% can be obtained.

[0089] <Example 6>

[0090] Example 6 is Example 6. The structures and shapes of the first panel 10 and the second panel 20 are the same as those in Example 1. The second panel 20 is arranged at an interval G = 50.0 mm with respect to the first panel 10. The gain value (peak of the reflection waveform) at 50° of the RCS curve when the electromagnetic wave incident at an incident angle of 0° is reflected at a reflection angle of 50° is -1.8146 dB. With the correction value ε p = 0.7826, the power reflection efficiency after correcting this gain value is 72.3%. When the interval G is 50.0 mm, a high power reflection efficiency exceeding 70% can be obtained.

[0091] <Example 7>

[0092] Example 7 is Example 7. The structures and shapes of the first panel 10 and the second panel 20 are the same as those in Example 1. The second panel 20 is arranged at an interval G = 90.0 mm with respect to the first panel 10. The gain value (peak of the reflection waveform) at 50° of the RCS curve when the electromagnetic wave incident at an incident angle of 0° is reflected at a reflection angle of 50° is -1.7730 dB. When correcting this gain value with the correction value ε p = 0.7826, the power reflection efficiency is 73.0%. When the interval G is 90.0 mm, a high power reflection efficiency exceeding 70% can be obtained.

[0093] <Example 8>

[0094] Example 8 is Comparative Example 7. The structures and shapes of the first panel 10 and the second panel 20 are the same as those in Example 1. The second panel 20 is arranged at an interval G = 100.0 mm with respect to the first panel 10. The gain value (peak of the reflection waveform) at 50° of the RCS curve when the electromagnetic wave incident at an incident angle of 0° is reflected at a reflection angle of 50° is -2.2818 dB. With the correction value ε p = 0.7826, the power reflection efficiency after correcting this gain value is 64.9%. When the interval G is 100.0 mm, the power reflection efficiency is less than 65%, and it is difficult to expect sufficient improvement of the radio wave environment.

[0095] Based on the results of Examples 1 to 8, in the direction perpendicular to the panel surface of the reflection panel 30, the interval G between the first panel 10 and the second panel 20 is preferably 0.0 mm or more and less than 100.0 mm. By maintaining the second panel 20 at an interval G from the first panel 10, incident electromagnetic waves can be reflected with sufficient reflection intensity in the designed direction. By holding the second panel 20 so as to be movable within the plane of the first panel 10, the second panel 20 can be adjusted to the optimal position according to the arrival direction and the direction in which the waves are to be reflected. With respect to one first panel 10, two or more second panels 20 can also be held while maintaining the above interval G range. By using multiple second panels 20, the region of non-normal reflection can be expanded. The first panel 10, which is easily formed into a large-area specular reflection, can, for example, hold multiple second panels 20 so as to be movable with respect to a 3.0 m × 3.0 m first panel 10. By using the first panel 10, a large-area panel with a power reflection efficiency close to 100% is used to expand the region where the radio wave propagation environment can be improved. By using the second panel 20, the radio wave propagation environment in the region that cannot be covered by specular reflection can be improved.

[0096] As described above, the embodiments of the present disclosure have been described, but the present disclosure is not limited to the above embodiments. As the second part 312 of the holding portion 31, a winding type transparent wire can be used instead of the slider mechanism and combined with the transparent hook that forms the first part. If there are no problems with the mechanical strength and safety of the reflection panel 30, only any one of the top frame 57, the bottom frame 58, and the frame 50 as the side frame can be used. When connecting multiple electromagnetic wave reflection devices 60, from the viewpoint of making the reflection potential continuous between the first panels 10 of adjacent reflection panels 30, it is preferable that at least a part of the frame 50 is formed of a conductor, specifically, the part connecting the edges of two adjacent first panels 10. When using a single electromagnetic wave reflection device 60 alone, the side frame 50 can also be used to hold the second panel 20 so as to be movable relative to the first panel 10.

[0097] The above disclosure may include the following forms.

[0098] (Item 1) A reflection panel, wherein,

[0099] It has:

[0100] A first panel that specularly reflects electromagnetic waves in a desired frequency band selected from the frequency band of 1 GHz or more and 300 GHz or less; and

[0101] A second panel having a metasurface with controlled reflection characteristics,

[0102] The distance between the above-mentioned first panel and the above-mentioned second panel in the direction perpendicular to the panel surface is 0.0 mm or more and less than 100.0 mm.

[0103] (Item 2) The reflecting panel according to Item 1, wherein

[0104] The above-mentioned second panel is arranged on the incident side of the above-mentioned electromagnetic wave to the above-mentioned first panel.

[0105] (Item 3) The reflecting panel according to Item 1 or 2, wherein

[0106] The planar size of the above-mentioned second panel is smaller than the planar size of the above-mentioned first panel.

[0107] (Item 4) The reflecting panel according to any one of Items 1 to 3, wherein

[0108] The above-mentioned second panel is movably or detachably held with respect to the above-mentioned first panel.

[0109] (Item 5) The reflecting panel according to any one of Items 1 to 4, wherein

[0110] It has a holding part that can be movably or detachably mounted on a part of the edge of the above-mentioned first panel and holds the above-mentioned second panel.

[0111] (Item 6) The reflecting panel according to Item 5, wherein

[0112] The above-mentioned holding part has a first part that can move in a first direction along a first edge of the above-mentioned first panel, and a second part that supports the above-mentioned second panel and can change its length in a second direction different from the above-mentioned first direction.

[0113] (Item 7) An electromagnetic wave reflecting device, wherein

[0114] It includes:

[0115] A reflecting panel that reflects electromagnetic waves in a desired frequency band selected from the frequency band of 1 GHz or more and 300 GHz or less; and

[0116] A frame that holds the above-mentioned reflecting panel;

[0117] The above-mentioned reflecting panel has a first panel that specularly reflects the above-mentioned electromagnetic waves, and a second panel that has a metasurface with controlled reflection characteristics,

[0118] The distance between the above-mentioned first panel and the above-mentioned second panel in the direction perpendicular to the panel surface of the above-mentioned reflecting panel is 0.0 mm or more and less than 100.0 mm.

[0119] (Item 8) The electromagnetic wave reflection device according to Item 7, wherein

[0120] The second panel is disposed on the incident side of the electromagnetic wave to the first panel.

[0121] (Item 9) The electromagnetic wave reflection device according to Item 7 or 8, wherein

[0122] The planar size of the second panel is smaller than the planar size of the first panel.

[0123] (Item 10) The electromagnetic wave reflection device according to any one of Items 7 to 9, wherein

[0124] The second panel is movably or detachably held with respect to the first panel.

[0125] (Item 11) The electromagnetic wave reflection device according to any one of Items 7 to 10, wherein

[0126] The frame includes a top frame that holds the upper end of the first panel, a side frame that holds the side end of the first panel, or a bottom frame that holds the lower end of the first panel,

[0127] The second panel is movably or detachably held with respect to the first panel by a part of the top frame, the side frame, or the bottom frame.

[0128] (Item 12) The electromagnetic wave reflection device according to Item 11, wherein

[0129] There is a holding portion that holds the second panel with respect to the first panel,

[0130] The holding portion has: a first portion that can move in a first direction along the top frame, the side frame, or the bottom frame, and a second portion that supports the second panel and can change its length in a second direction different from the first direction.

[0131] This application claims priority based on Japanese Patent Application No. 2022-204383 filed on December 21, 2022, and includes the entire contents of the Japanese patent application.

[0132] Explanation of reference numerals

[0133] 10, 10-1, 10-2, 10-3... The first panel; 11... Conductive layer; 12, 13... Adhesive layer; 14, 15... Dielectric layer; 20, 20-1, 20-2, 20-3... The second panel; 30, 30-1, 30-2, 30-3... Reflective panel; 31A, 31B, 31C... Holding part; 34... Socket; 60, 60-1, 60-2, 60-3... Electromagnetic wave reflection device; 50... Frame (side frame); 56... Foot; 57, 57A, 57B... Top frame; 58... Bottom frame; 60, 60-1, 60-2... Electromagnetic wave reflection device; 100... Electromagnetic wave reflection fence; 210... Unit cell; 211, 211a~211f... Metal patch; 212... Protective layer; 213... Adhesive layer; 214... Conductive layer; 215... Dielectric layer; 216... Ground layer; 311, 313, 315... The first part; 312... The second part; 520... Main body; 521, 522... Slit.

Claims

1. A reflective panel, wherein, it has: a first panel that specularly reflects electromagnetic waves in a desired frequency band selected from the frequency band of 1 GHz or more and 300 GHz or less; and a second panel having a metasurface with controlled reflection characteristics, the distance between the first panel and the second panel in the direction perpendicular to the panel surface is 0.0 mm or more and less than 100.0 mm.

2. The reflective panel according to claim 1, wherein, the second panel is disposed on the incident side of the electromagnetic waves to the first panel.

3. The reflective panel according to claim 1, wherein, the planar size of the second panel is smaller than the planar size of the first panel.

4. The reflective panel according to claim 1, wherein, the second panel is movably or detachably held relative to the first panel.

5. The reflective panel according to claim 1, wherein, it has a holding portion that is movably or detachably mounted on a part of the edge of the first panel and holds the second panel.

6. The reflective panel according to claim 5, wherein, the holding portion has a first part that can move in a first direction along a first edge of the first panel, and a second part that supports the second panel and can change its length in a second direction different from the first direction.

7. An electromagnetic wave reflection device, wherein, it includes: a reflective panel that reflects electromagnetic waves in a desired frequency band selected from the frequency band of 1 GHz or more and 300 GHz or less; and a frame that holds the reflective panel; the reflective panel has a first panel that specularly reflects the electromagnetic waves and a second panel having a metasurface with controlled reflection characteristics, the distance between the first panel and the second panel in the direction perpendicular to the panel surface of the reflective panel is 0.0 mm or more and less than 100.0 mm.

8. The electromagnetic wave reflection device according to claim 7, wherein, the second panel is disposed on the incident side of the electromagnetic waves to the first panel.

9. The electromagnetic wave reflection device according to claim 7, wherein, the planar size of the second panel is smaller than the planar size of the first panel.

10. The electromagnetic wave reflection device according to claim 7, wherein, the second panel is movably or detachably held relative to the first panel.

11. The electromagnetic wave reflection device according to claim 7, wherein, the frame includes a top frame that holds the upper end of the first panel, a side frame that holds the side end of the first panel, or a bottom frame that holds the lower end of the first panel, the second panel is movably or detachably held relative to the first panel by a part of the top frame, the side frame, or the bottom frame.

12. The electromagnetic wave reflection device according to claim 11, wherein, it has a holding portion that holds the second panel relative to the first panel, The holding part has: a first part capable of moving in a first direction along the top frame, the side frame, or the bottom frame, and a second part that supports the second panel and is capable of changing its length in a second direction different from the first direction.

Images