Metamaterial Device and Transparent Member

Abstract

A metamaterial device of this invention is a metamaterial device in which a millimeter wave and sunlight enter, including a reconfigurable intelligent surface portion configured to beamform the millimeter wave, and a solar cell portion formed by a solar panel configured to convert the sunlight into electric power. The reconfigurable intelligent surface portion includes a metamaterial layer formed by metamaterial cells arranged in an array, the metamaterial cell comprises a metamaterial element, a dielectric filling portion arranged around the metamaterial element, and an active element configured to electrically control the metamaterial cell, and the active element is electrically connected to the solar panel.

Description

Metamaterial Device and Transparent Member

[0001] The present invention relates to a metamaterial device including a solar cell, and a transparent member.

[0002] To implement a further increase of the speed and capacity of wireless communication systems, utilization of a high-frequency band such as a millimeter-wave band is expected (for example, non-patent literature 1). However, when the frequency of a radio wave becomes high, wireless communication quality deteriorates due to the influence of shielding (for example, non-patent literature 2). As a technique for solving the problem, beamforming has received attention, which changes a radiation pattern and a radiation direction by adjusting the phase of an incident electromagnetic wave to avoid an obstacle.

[0003] In the millimeter-wave frequency band, beamforming using a Reconfigurable Intelligent Surface (to be referred to as "RIS" hereinafter) device has been extensively studied. As an example, the RIS device is made of a metamaterial (for example, non-patent literature 3). A metamaterial has an artificial structure and is configured to acquire properties from a subwavelength cell and imitate the atomic structure of a natural material. With a specific metamaterial cell configuration, an electromagnetic wave can be manipulated at a desired frequency via control of various characteristics such as the reflectance, permeability, and permittivity of the material.

[0004] Beamforming can dynamically be controlled by incorporating an active element such as a diode or a transistor in the metamaterial device. Hence, a power supply is needed to dynamically control beamforming.

[0005] On the other hand, a solar cell converts incident energy of light into electricity (electric power) by a photoelectric effect (for example, non-patent literature 4 and 5). Individual solar cells form a solar panel.

[0006] [NPL 1] W. Hong et al., "The Role of Millimeter-Wave Technologies in 5G / 6G Wireless Communications", IEEE Journal of Microwaves, January, 2021, Vol. 1, Issue 1, p. 101-122. [NPL 2] Theodore S. Rappaport et al., "Wideband Millimeter-Wave Propagation Measurements and Channel Models for Future Wireless Communication System Design", IEEE Transaction on communications, September, 2015, Vol. 63, No. 9, p. 3029-3056. [NPL 3] Iyemeh Uchendu and James Kelly, "Survey of Beam Steering Techniques Available for Millimeter Wave Applications", Progress In Electromagnetics Research B, 2016, Vol. 68, 35-54, p.35-54. [NPL 4] Athil S. Al-Ezzi, and Mohamed Nainar M. Ansari, "Photovoltaic Solar Cells: A Review", July 8, 2022, <URL: https: / / doi.org / 10.3390 / asi5040067>. [NPL 5] Fatima Rehman et al., "Fourth-generation solar cells: a review", Energy Advances, September, 2023, Vol. 2, No. 9, p. 1239-1262.

[0007] In beamforming using RIS devices, to cope with attenuation of a signal reception region and signals caused by an increase of an operating frequency, more RIS devices are necessary. As a result, power consumption increases.

[0008] Also, to install more RIS devices, a wider space (area) is needed.

[0009] In addition, to install more solar panels, a wider space (area) is needed.

[0010] In order to solve the above-described problems, according to the present invention, there is provided a metamaterial device in which a millimeter wave and sunlight enter, comprising a reconfigurable intelligent surface portion configured to beamform the millimeter wave, and a solar cell portion formed by a solar panel configured to convert the sunlight into electric power, wherein the reconfigurable intelligent surface portion comprises a metamaterial layer formed by metamaterial cells arranged in an array, the metamaterial cell comprises a metamaterial element, a dielectric filling portion arranged around the metamaterial element, and an active element configured to electrically control the metamaterial cell, and the active element is electrically connected to the solar panel.

[0011] According to the present invention, there is also provided a metamaterial device in which a millimeter wave and sunlight enter, comprising a reconfigurable intelligent surface portion configured to beamform the millimeter wave, and a solar cell portion formed by a solar panel configured to convert the sunlight into electric power, wherein the reconfigurable intelligent surface portion comprises a metamaterial layer formed by metamaterial cells arranged in an array, the metamaterial cell comprises a metamaterial element, and a dielectric filling portion arranged around the metamaterial element, and the reconfigurable intelligent surface portion is arranged on the solar panel.

[0012] According to the present invention, it is possible to reduce power consumption and provide a sustainable metamaterial device and transparent member.

[0013] Fig. 1 is a schematic view showing the configuration of a metamaterial device according to the first embodiment of the present invention;Fig. 2A is a schematic view showing the configuration of a solar cell portion in the metamaterial device according to the first embodiment of the present invention;Fig. 2B is a schematic view showing an example of the configuration of the solar cell portion in the metamaterial device according to the first embodiment of the present invention;Fig. 2C is a schematic view showing an example of the configuration of the solar cell portion in the metamaterial device according to the first embodiment of the present invention;Fig. 3A is a schematic view showing the configuration of a RIS portion in the metamaterial device according to the first embodiment of the present invention;Fig. 3B is a schematic view showing an example of the configuration of a metamaterial cell in the RIS portion in the metamaterial device according to the first embodiment of the present invention;Fig. 3C is a schematic view showing examples of the configuration of the metamaterial cell in the RIS portion in the metamaterial device according to the first embodiment of the present invention;Fig. 4A is a schematic plan view showing the configuration of the metamaterial device according to the first embodiment of the present invention;Fig. 4B is a schematic plan view showing an example of the configuration of the metamaterial device according to the first embodiment of the present invention;Fig. 4C is a schematic plan view showing an example of the configuration of the metamaterial device according to the first embodiment of the present invention;Fig. 4D is a schematic plan view showing an example of the configuration of the metamaterial device according to the first embodiment of the present invention;Fig. 5 is a schematic view for explaining the operation of the metamaterial device according to the first embodiment of the present invention;Fig. 6 is a schematic view showing the configuration of electrical connection of the metamaterial device according to the first embodiment of the present invention;Fig. 7A is a schematic plan view showing the configuration of a metamaterial device according to the second embodiment of the present invention;Fig. 7B is a schematic plan view showing an example of the configuration of the metamaterial device according to the second embodiment of the present invention;Fig. 7C is a schematic plan view showing an example of the configuration of the metamaterial device according to the second embodiment of the present invention;Fig. 8A is a schematic view showing the configuration of a metamaterial device according to the third embodiment of the present invention;Fig. 8B is a schematic plan view showing the configuration of the metamaterial device according to the third embodiment of the present invention;Fig. 9 is a schematic view showing a configuration to which the metamaterial device according to the first embodiment of the present invention is applied;Fig. 10 is a schematic view showing a configuration to which the metamaterial device according to the second embodiment of the present invention is applied;Fig. 11 is a schematic view showing a configuration to which the metamaterial device according to the second embodiment of the present invention is applied; andFig. 12 is a schematic view showing a configuration to which the metamaterial device according to the third embodiment of the present invention is applied.

[0014] <First Embodiment> A metamaterial device according to the first embodiment of the present invention will be described with reference to Figs. 1 to 6.

[0015] <Configuration of Metamaterial Device> A metamaterial device 10 according to this embodiment is a Reconfigurable Intelligent Surface (to be referred to as "RIS" hereinafter) device including a solar cell. As shown in Fig. 1, the metamaterial device 10 includes a RIS portion 11 and a solar cell portion 12. The metamaterial device 10 may have, on the surface of the RIS portion 11, a protective layer (made of, for example, glass) (not shown) that prevents a damage.

[0016] The solar cell portion 12 is a silicon-based solar panel. As shown in Fig. 2A, the silicon-based solar panel includes, sequentially from the lower surface of the solar cell portion 12, a conductive contact layer 1201, p-type Si 1202, an absorption layer 1203, n-type Si 1204, conductive stripes 1205 of a metal, and protective glass 1206. The conductive stripes 1205 of a metal are arranged on the surface of the n-type Si 1204. The surface 1204 of the n-type Si and the conductive stripes 1205 of a metal are covered with the protective glass 1206 such that these are protected from external factors such as dust, moisture, and physical damages.

[0017] As shown in Fig. 2B, the solar cell portion 12 may be a polymer-based solar panel. The polymer-based solar panel includes, sequentially from the lower surface, a conductive electrode 1211, a thin semiconductor polymer blend 1212 made of p- and n-type semiconductor polymers, a conductive polymer 1213 such as PEDOT:PSS, a conductive ITO (Indium Tin Oxide) film 1214, and protective glass 1215.

[0018] Alternatively, as shown in Fig. 2C, the solar cell portion 12 may be a perovskite-based solar panel. The perovskite-based solar panel includes, sequentially from the lower surface, a conductive contact electrode 1221 of a metal, a hole transporting layer 1222, a perovskite material 1223, an electron transporting layer 1224, a transparent electrode 1225 of ITO or the like, and protective glass 1226.

[0019] The RIS portion 11 is a reflection-type RIS device. The RIS portion 11 is arranged on the surface of the protective glass of the solar cell portion (solar panel) 12.

[0020] As shown in Fig. 3A, the RIS device 11 sequentially includes a metamaterial layer 111, a dielectric spacer layer 112, and a reflection layer 113.

[0021] The metamaterial layer 111 is made of a metasurface on which conductive metamaterial cells 114 of subwavelength are periodically arranged.

[0022] The subwavelength metamaterial cells 114 are arranged in an array and resonate at a predetermined millimeter-wave frequency (30 to 500 GHz).

[0023] Fig. 3B shows an example of the configuration of the metamaterial cell 114. The metamaterial cell 114 includes a metamaterial element 115, a dielectric filling portion 116, and a lumped active element 117. The active element 117 may be electrically connected to the solar cell portion (solar panel) 12.

[0024] The metamaterial element 115 is made of a conductive material that exhibits high optical transparency (degree of being optically transparent), for example, a conductive oxide (for example, INTO or AZO) or a conductive polymer (for example, PEDOT:PSS).

[0025] Here, "optically transparent" includes "transparent to light necessary for generating electric power in the solar cell portion 12". Alternatively, it includes "transparent within the wavelength range of light absorbed by an active layer (for example, an absorption layer) in the solar cell portion 12". For example, the material may be transparent to visible light. Alternatively, the material may be transparent to light in the infrared range or ultraviolet range.

[0026] The dielectric filling portion 116 is made of nonconductive dielectric materials of various types, for example, polyethylene or polytetrafluoroethylene (PTFE).

[0027] The lumped active element 117 is an element that responds to an externally applied electric control signal such as a voltage, an electric field, or a current. For example, it may be a diode or a transistor.

[0028] In the metamaterial cell 114, the metamaterial element 115 has a gap 118 (length: g). The gap 118 forms a gap capacitance Cg.

[0029] The lumped active element 117 has a variable lumped capacitance CLand is connected to the gap 118.

[0030] An equivalent capacitance Ceqof the metamaterial element 115 is the sum of the gap capacitance Cgand the variable lumped capacitance CLof the active element 117.

[0031] A control signal is applied via a bias line and changes the variable lumped capacitance CLof the active element 117. The equivalent capacitance Ceqof the metamaterial element 115 is thus changed. By the change of the capacitance, the transmission characteristics (the transmission intensity and the transmission phase) of the metamaterial cell 114 change. Thus, in the metamaterial cell 114, the change of the equivalent capacitance Ceqor relative permittivity of the metamaterial element 115 can be induced, and reflection or transmission of an incident millimeter wave can be controlled.

[0032] For example, the metamaterial cell 114 has a size (a × b) = 300 μm × 300 μm and a gap length g = 60 μm, and the metamaterial element 115 has a width w = 30 μm.

[0033] The size of the metamaterial cell 114 may fall within the range of a square whose side is λ / 2 long, or within the range of a square whose side is λ / 20 or more and λ / 2 or less long. For example, at 30 GHz, the size of the metamaterial cell 114 may fall within the range of a square whose side is 0.5 mm or more and 5 mm or less long. At 100 GHz, the size may fall within the range of a square whose side is 0.12 mm or more and 1.5 mm or less long. At 300 GHz, the size may fall within the range of a square whose side is 50 μm or more and 500 μm or less long. The thickness of the metamaterial cell 114 may be 50 μm or more and 2 mm or less.

[0034] Fig. 3B shows an example in which the metamaterial cell 114 includes the metamaterial element 115 having an H shape, but the present invention is not limited to this. For example, configurations of the metamaterial cells 114 shown in Fig. 3C may be used.

[0035] An example in which two-dimensional metamaterial elements are used in the metamaterial cell 114 has been described. However, three-dimensional metamaterial elements in which a plurality of metamaterial elements are stacked may be used.

[0036] Also, an example in which active control based on the lumped capacitive element is used in the metamaterial cell 114 has been described. However, another control method based on a liquid crystal, a thermal material, or the like may be used.

[0037] The dielectric spacer layer 112 occupies most of the volume of the RIS device 11. Like the above-described dielectric filling portion 116, the dielectric spacer layer 112 is made of nonconductive dielectric materials of various types, for example, polyethylene or polytetrafluoroethylene (PTFE).

[0038] Like the metamaterial cell 114, the reflection layer 113 is a thin film made of a material that is optically transparent and has conductivity.

[0039] The minimum thickness of the reflection film on the bottom surface has a value more than a surface skin thickness δ, and is represented by

[0040]

[0041] Here, ρ is the low resistivity of the material, μ0is the permeability of a free space (μ0= 4π × 10-7H / m), μris the relative permeability (normally, 1), and f0is the frequency of the electromagnetic wave. For example, in a case where a thin ITO film is used, if the operating frequency is 300 GHz, ρ is about 0.1 mΩcm, μris about 1, and the surface skin thickness δ is about 0.9 μm. Hence, the thickness of the reflection layer 113 may be larger than the value obtained by equation (1).

[0042] Thus, the metamaterial device 10 includes the RIS portion 11 and the solar cell portion 12 in a direction vertical to the surface on which the metamaterial cells 114 are arranged. In the metamaterial device 10, the reflection layer 113 of the RIS portion 11 may be directly arranged on the surface of the protective layer of the solar cell portion 12. In this configuration, the protective layer of the solar cell portion 12 functions as the carrier substrate of the RIS device 11.

[0043] In the metamaterial device 10, to pass sunlight up to the active layer (absorption layer) and generate a photovoltaic effect and DC power, the solar cell portion 12 includes an optically transparent surface layer.

[0044] In addition, the RIS portion 11 is also optically transparent to sunlight to prevent unnecessary reflection or absorption of sunlight.

[0045] In this configuration,, if the RIS portion 11 is of a transmission type, that is, passes a millimeter wave, no beamformed millimeter wave can exit because the solar cell portion 12 includes a conductive electrode and a semiconductor film that absorbs the electromagnetic wave.

[0046] Hence, the RIS portion 11 in the metamaterial device 10 is formed by a reflection-type RIS device.

[0047] Also, in the metamaterial device 10, a transmission-type RIS device may be used by redesigning the structure of the solar cell, for example, the electrode shape, the electrode cover, or the like, or by reducing the operating frequency of the RIS device 11.

[0048] In the metamaterial device 10, the RIS portion 11 may be arranged at a predetermined interval by making the lower surface of the RIS portion 11 (for example, the lower surface of the reflection layer 113) face the surface of the solar cell portion 12 (or the surface of the protective layer). In this configuration, a carrier substrate may be arranged between the RIS portion 11 and the solar cell portion 12.

[0049] Figs. 4A to 4D show examples of the configuration of the metamaterial device 10.

[0050] In the metamaterial device 10, the solar cell portion 12 is formed by a solar panel having a predetermined size. For example, it may have a typical structure of a commercially available solar panel.

[0051] In the metamaterial device 10, the RIS portion 11 is formed on the entire surface of the solar panel 12 (Fig. 4A) or in a limited region of the solar panel 12 (Fig. 4B). The area of the solar panel 12 covered with the RIS device 11 depends on many factors associated with the complexity of channels of beamforming (the number of beams to be simultaneously controlled), the size of an incident beam, the power of an incident beam, and the like.

[0052] In the metamaterial device 10, as shown in Fig. 4C, a plurality of separated RIS devices 11 may operate independently of each other.

[0053] Also, as shown in Fig. 4D, the surface area of the solar panel 12 may be smaller than the surface area of the RIS portion 11 of the device.

[0054] Average energy generated by the solar panel 12 depends on an effective sunshine duration related to the place or time. Normally, in terms of peak time, the solar panel 12 having a size of 1 m2generates 0.2 to 0.3 kWh per hour.

[0055] The power consumption of the RIS device 11 depends on the configuration of the RIS device 11. For example, in a configuration in which a varactor diode is used as the active element in the metamaterial layer 111 of the RIS device 11, since the varactor diode operates by a reverse bias, the leakage current in operation falls within the range of nanoampere at an operating voltage of 1 to 2 V, and very little current flows. As a result, power consumption per single diode falls within the range of nanowatt or microwatt. Hence, the total power consumption of the RIS device 11 is much lower than power generated by the solar panel 12.

[0056] In addition, for example, a liquid crystal thin film may be used as the active element in the metamaterial layer 111. In this configuration, since no current flows to the liquid crystal matrix, power consumption is very low. For the sake of comparison, the power consumption of a liquid crystal display whose size is 1 m2falls within the range of 30 W or less, including the power consumption in the transistor and the display.

[0057] As shown in Fig. 5, in the metamaterial device 10, the RIS portion 11 interferes with an electromagnetic wave 1 used in wireless communication, and the solar cell portion 12 interferes with sunlight 2.

[0058] The electromagnetic wave 1 is reflected by the RIS portion 11 and never enters the metamaterial device 10 through the reflection layer 113 of the RIS portion 11.

[0059] The sunlight 2 passes through the optically transparent RIS portion 11 and the protective glass of the solar cell portion 12 and propagates to the absorption layer (active layer) of the solar cell portion 12. As a result, electric power is generated by the photoelectric effect.

[0060] Fig. 6 shows an example of electrical connection between the metamaterial device 10 and peripheral devices.

[0061] The metamaterial device 10 includes a solar cell charge controller (to be referred to as a "charge controller" hereinafter) 141, a battery 142, an inverter 143, and a RIS controller 144. The metamaterial device 10 is also connected to a DC-driven device (a device to which DC power is supplied) 145, an AC-driven device 146, and an external power grid 3.

[0062] In the solar cell portion (solar panel) 12 of the metamaterial device 10, a DC current is generated under irradiation of sunlight. The generated DC current is supplied to the charge controller 141. The charge controller 141 controls the flow of the current (energy) as needed.

[0063] The DC current is charged in the battery 142 via the charge controller 141. Also, the DC current is supplied to the DC-driven device 145 via the charge controller 141.

[0064] The inverter 143 converts the DC current into an AC current. The AC current is supplied to the RIS controller 144. The AC current is supplied to the AC-driven device 146. An unused AC current (energy) is transmitted to the power grid 3.

[0065] The RIS controller 144 operates by the AC current or the DC current in accordance with the type of the controller or the operation principle of the RIS device. In the metamaterial device 10, the RIS controller 144 operates by the AC current supplied from the inverter 143 or the power grid 3. If the RIS device 11 uses the DC current for the active operation, for example, if the RIS device 11 performs the active operation by applying a negative bias to various channels of the device, the AC current supplied to the RIS controller 144 is rectified and converted into a DC current. In the RIS device 11, reflection of an incident beam is actively controlled via control of different channels. Here, the channels are defined by rows and columns in the array-like arrangement (metasurface) of the metamaterial cells.

[0066] The RIS controller 144 may operate by the DC current (a broken line in Fig. 6).

[0067] According to the metamaterial device of this embodiment, since the electric power generated by the solar cell can be supplied to the RIS device, it is possible to reduce power consumption and implement a sustainable device. In addition, the installation space can be reduced by integrating the RIS device and the solar cell into one device.

[0068] <Second Embodiment> A metamaterial device according to the second embodiment of the present invention will be described with reference to Figs. 7A to 7C.

[0069] <Configuration of Metamaterial Device> A metamaterial device 20 according to this embodiment includes a RIS portion 11 and a solar cell portion 12.

[0070] The RIS portion 11 is formed by a reflection-type RIS device and arranged on a side surface of the solar panel 12. In other words, the metamaterial device 20 includes the RIS portion 11 and the solar cell portion 12 in parallel to a surface on which metamaterial cells 114 are arranged.

[0071] In the first embodiment, it is sometimes difficult to directly form the RIS device 11 on the surface of the solar panel 12 because of problems in fabrication or problems in the consistency of optical characteristics.

[0072] In this embodiment, the RIS device 11 is arranged adjacent to the solar panel 12. The RIS device 11 operates by energy generated from the solar panel 12 or a power grid 3. Also, it is possible to maintain the original functions of the RIS device 11 and the solar panel 12.

[0073] Figs. 7A to 7C show examples of the configuration of the metamaterial device 20. As shown in Fig. 7A, the RIS device 11 is arranged on the side surface of the main body of the solar panel 12. Both devices are incorporated in the same frame.

[0074] Also, as shown in Fig. 7B, the RIS device 11 may be arranged in a region surrounding the solar panel 12. The RIS device 11 operates based on the same principle as in other forms.

[0075] Also, as shown in Fig. 7C, the RIS device 11 may be arranged at the center and surrounded by the small solar panel 12. This configuration is advantageous for a RIS device using a private power source.

[0076] According to the metamaterial device of this embodiment, since the electric power generated by the solar cell can be supplied to the RIS device, it is possible to reduce power consumption and easily implement a sustainable device

[0077] <Third Embodiment> A metamaterial device according to the third embodiment of the present invention will be described with reference to Figs. 8A and 8B.

[0078] <Configuration of Metamaterial Device> As shown in Figs. 8A and 8B, a metamaterial device 30 according to this embodiment includes a RIS portion 11 and a solar cell portion 12.

[0079] The RIS portion 11 is formed by a reflection- RIS device. The reflection-type RIS device 11 is a passive device that is not actively controlled, and does not need an external power source or signal controller.

[0080] In a simple beamforming operation, dynamic control of the RIS device 11 is not necessary.

[0081] The RIS device 11 is an optically transparent passive device, and to extend a radio signal reception range, attached to the existing solar panel 12 without adding a new installation place.

[0082] The RIS device 11 may be, for example, a hard device based on glass (Fig. 8A), or may be a flexible device based on polymer epoxy resin (Fig. 8B). In both cases, the RIS device 11 is installed in a predetermined place of the solar panel 12 and then mounted on the surface of the protective glass of the solar panel 12.

[0083] According to the metamaterial device of this embodiment, it is possible to implement a sustainable device without needing dynamic control of the RIS device. In addition, the installation space can be reduced by integrating the RIS device and the solar cell into one device.

[0084] <First Example> A metamaterial device according to the first example of the present invention will be described with reference to Fig. 9.

[0085] Fig. 9 shows an example of application of the metamaterial device according to this example. As the metamaterial device, the metamaterial device according to the first embodiment is used.

[0086] A metamaterial device 10 is installed on the roof of a detached house. Alternatively, in a configuration using a transmission-type solar panel, the metamaterial device may be installed on a window. Otherwise, the metamaterial device may be installed in solar power plants of various types in a wireless communication region.

[0087] In the metamaterial device 10, an incident electromagnetic wave 1_1 is reflected from a RIS portion (RIS device) 11 to another node in a wireless network (reflected electromagnetic wave 1_2).

[0088] Depending on time in a day, weather conditions, the power consumption of the device, and the like, the RIS device 11 operates by energy supplied from the solar panel 12 or an external power grid 3.

[0089] As shown in Fig. 9, the energy generated by the solar panel 12 is transmitted to an inverter 143 configured to convert a direct current (DC) into an alternating current (AC) via a charge controller 141 of the solar cell. The AC power is used by a device or the like in the house (household). In addition, the AC power is transmitted to the power grid 3.

[0090] The charge controller 141 operates by the AC power or DC power depending on the type of the controller (FPGA, PLC, or the like) and the structure of the RIS device 11.

[0091] As the metamaterial device, the metamaterial device according to the second embodiment may be used.

[0092] <Second Example> A metamaterial device according to the second example of the present invention will be described with reference to Figs. 10 and 11.

[0093] Fig. 10 shows an example of a wireless communication system to which a metamaterial device according to this example is applied. As the metamaterial device, the metamaterial device according to the first embodiment is used.

[0094] The metamaterial device 10 includes a RIS portion 11 and a solar cell portion 12. The solar cell portion 12 is formed by the solar panel 12 that converts incident sunlight into energy. The RIS portion 11 is formed by a reflection-type metamaterial beamformer that controls propagation of an electromagnetic wave.

[0095] As shown in Fig. 10, the wireless communication system includes a first metamaterial device and a second metamaterial device. A first metamaterial device 10_1 is an optically opaque device, and the solar panel 12 is not transparent. The first metamaterial device 10_1 is formed based on a normally used solar panel. A second metamaterial device 10_2 is an optically transparent device, and the solar panel 12 is transparent.

[0096] As shown in Fig. 10, a millimeter wave 1_1 is radiated from a base station 4 to the first metamaterial device 10_1 installed on the roof of a detached house. The millimeter wave 1_1 is beamformed via controllable reflection from the RIS portion 11 of the first metamaterial device 10_1 and propagates to the second metamaterial device 10_2 incorporated in a window 6 of a building. The millimeter wave 1_1 is beamformed by the second metamaterial device 10_2 and reflected to a user device 7.

[0097] Similarly, a millimeter wave 1_2 is radiated from a high altitude platform station (HAPS) (also called a "high altitude pseudo-satellite") 5. The millimeter wave 1_2 is radiated to the metamaterial device 10_1 on the roof of a detached house. The millimeter wave 1_2 is beamformed by the first metamaterial device 10_1 and reflected to the metamaterial device 10_2. The millimeter wave 1_2 is beamformed by the second metamaterial device 10_2 and reflected to the user device 7.

[0098] Simultaneously, during irradiation of sunlight 2, the solar panel 12 of each metamaterial device converts the sunlight into electric power used for active control of the RIS device 11. Remaining converted electric power is charged in a battery or transmitted to a power grid.

[0099] As an example, the second metamaterial device 10_2 is optically transparent and is attached to the glass window 6 in an office building or a high-rise building, as shown in Fig. 11. The second metamaterial device 10_2 may be attached to a transparent construction member such as a window or wall made of a resin.

[0100] Alternatively, the second metamaterial device 10_2 may be attached to a transparent member such as a wall in a moving body such as an automobile.

[0101] In the second metamaterial device 10_2, the solar panel 12 is a device that is optically transparent to sunlight or the like and converts incident sunlight into electricity.

[0102] The solar panel 12 may pass at least a part of incident sunlight. For example, in the solar panel 12, light in a partially wavelength range (for example, 700 to 2,500 nm) of sunlight may be absorbed by an active layer, and light in the remaining wavelength range (for example, 350 to 700 nm) may pass through the active layer. Alternatively, in the solar panel 12, a plurality of active layers such as absorption layers may be arranged in a plane, and sunlight may pass through a region where no active layer is arranged.

[0103] The RIS device 11 is a device that is optically transparent to sunlight or the like and is used for beamforming of an electromagnetic wave in the millimeter-wave band.

[0104] The RIS device 11 is a reflection-type device, and reflects the incident electromagnetic wave 1_1 to a desired direction based on a dynamically applied control signal (reflected electromagnetic wave 1 _2). Alternatively, the RIS device 11 may be a transmission-type device. In case of transmission-type device, the electromagnetic wave that enters the RIS device 11 and passes through it passes through the solar panel 12 and is beamformed into the building (transmitted electromagnetic wave 1_3).

[0105] As the metamaterial device, the metamaterial device according to the second or third embodiment may be used.

[0106] <Third Example> A metamaterial device according to the third example of the present invention will be described with reference to Fig. 12.

[0107] The metamaterial device according to this embodiment includes a reflection-type RIS device 11 and is mounted on a high altitude platform station (HAPS) (also called a "high altitude pseudo-satellite"). As the metamaterial device, the metamaterial device according to the first embodiment is used.

[0108] Along with the increase of the speed and capacity of networks, HAPS that is a device high altitude long endurance capable of providing a communication service, like an artificial satellite, has been developed. The HAPS includes a base station that transmits a radio signal. Electric power is supplied by sunlight energy to the HAPS and stored in a machine body (airplane).

[0109] In the metamaterial device, the RIS device 11 is used as a control means of signal propagation, and mounted together with a solar panel 12 configured to generate electric power for the operation of the HAPS.

[0110] Assuming that the HAPS has a form of a small airplane 5_1, the RIS device 11 and the solar panel 12 are mounted in the structure of wings, as shown in Fig. 11. For example, the RIS device 11 is mounted on the lower surface portion of each wing. On the other hand, the solar panel 12 is mounted on the upper surface portion of each wing. Here, the upper-side surface of the wing (the surface on the sun side) in normal flight of the small airplane 5_1 is an upper surface, and the lower-side surface (the surface on the ground side) is a lower surface.

[0111] If the HAPS (small airplane) 5_1 and a low orbit satellite or high orbit satellite 5 need to communicate, the RIS device 11 may be formed on the upper surface of the solar panel 12 on the upper surface of each wing. In this configuration, the RIS on the upper surface of the wing functions as a node in communication between satellites.

[0112] In the metamaterial device, a RIS device controller operates using a DC current generated from the solar panel 12 mounted on the HAPS.

[0113] As the metamaterial device, the metamaterial device according to the second or third embodiment may be used.

[0114] In the embodiments of the present invention, in the configuration of a metamaterial device, and the like, an example of the structures, dimensions, and materials of the constituent parts has been described, but the present invention is not limited to these. It is only necessary to exhibit the function of the metamaterial device and obtain the effect.

[0115] Note that the present invention is not limited the above-described embodiments, and it is obvious that many modifications and combinations can be done by any person ordinarily skilled in the art without departing from the technical scope of the present invention.

[0116] Some or all of the above-described exemplary embodiments can also be described as in the following supplementary notes but are not limited to the followings.

[0117] (Supplementary Note 1) There is provided a metamaterial device in which a millimeter wave and sunlight enter, comprising a reconfigurable intelligent surface portion configured to beamform the millimeter wave, and a solar cell portion formed by a solar panel configured to convert the sunlight into electric power, wherein the reconfigurable intelligent surface portion comprises a metamaterial layer formed by metamaterial cells arranged in an array, the metamaterial cell comprises a metamaterial element, a dielectric filling portion arranged around the metamaterial element, and an active element configured to electrically control the metamaterial cell, and the active element is electrically connected to the solar panel.

[0118] (Supplementary Note 2) In the metamaterial device according to Supplementary Note 1, the metamaterial element has a gap, and the active element is connected to the gap.

[0119] (Supplementary Note 3) In the metamaterial device according to Supplementary Note 1 or 2, the reconfigurable intelligent surface portion further comprises, sequentially from the metamaterial layer, a spacer layer made of a dielectric, and a reflection layer configured to reflect the millimeter wave.

[0120] (Supplementary Note 4) In the metamaterial device according to any one of Supplementary Notes 1 to 3, the reconfigurable intelligent surface portion and the solar cell portion are arranged in a direction vertical to a surface on which the metamaterial cells are arranged.

[0121] (Supplementary Note 5) In the metamaterial device according to Supplementary Note 4, the reconfigurable intelligent surface portion is transparent within a wavelength range of light necessary for generating the electric power in the solar cell portion.

[0122] (Supplementary Note 6) The metamaterial device according to any one of Supplementary Notes 1 to 5 further comprises a solar cell charge controller to which a DC current generated by the solar panel is input, a battery to which a part of the DC current is input from the solar cell charge controller, an inverter to which a remaining part of the DC current is input from the solar cell charge controller and which is configured to convert the remaining part of the DC current into an AC current, and a RIS controller to which a part of the AC current is input and which is configured to control the active element.

[0123] (Supplementary Note 7) There is provided a metamaterial device in which a millimeter wave and sunlight enter, comprising a reconfigurable intelligent surface portion configured to beamform the millimeter wave, and a solar cell portion formed by a solar panel configured to convert the sunlight into electric power, wherein the reconfigurable intelligent surface portion comprises a metamaterial layer formed by metamaterial cells arranged in an array, the metamaterial cell comprises a metamaterial element, and a dielectric filling portion arranged around the metamaterial element, and the reconfigurable intelligent surface portion is arranged on the solar panel.

[0124] (Supplementary Note 8) There is provided a transparent member to which a metamaterial device defined according to any one of Supplementary Notes 1 to 7 and 9 is attached, wherein a reconfigurable intelligent surface portion is transparent within a wavelength range of light necessary for generating electric power in a solar cell portion, and the solar cell portion passes at least a part of the sunlight.

[0125] (Supplementary Note 9) In the metamaterial device according to any one of Supplementary Notes 1 to 3 and 6, the reconfigurable intelligent surface portion is arranged on a side surface of the solar cell portion.

[0126] (Supplementary Note 10) There is provided a high altitude platform station including a wing, comprising a metamaterial device according to any one of Supplementary Notes 1 to 7 and 9, wherein a solar cell portion is arranged on a surface of the wing, and a reconfigurable intelligent surface portion is arranged on at least one of an upper surface and a lower surface of the wing.

[0127] The present invention can be applied to a wireless communication apparatus and system.

[0128] 10...metamaterial device 11...reconfigurable intelligent surface portion 111...metamaterial layer 114...metamaterial cell 115...metamaterial element 116...dielectric filling portion 117...active element 12...solar cell portion

Claims

1. A metamaterial device in which a millimeter wave and sunlight enter, comprising: 　　　　　　　a reconfigurable intelligent surface portion configured to beamform the millimeter wave; and 　　　　　　　a solar cell portion formed by a solar panel configured to convert the sunlight into electric power, 　　　　　　　wherein the reconfigurable intelligent surface portion comprises 　　　　　　　a metamaterial layer formed by metamaterial cells arranged in an array, 　　　　　　　the metamaterial cell comprises: 　　　　　　　a metamaterial element; 　　　　　　　a dielectric filling portion arranged around the metamaterial element; and 　　　　　　　an active element configured to electrically control the metamaterial cell, and 　　　　　　　the active element is electrically connected to the solar panel.

2. The metamaterial device according to claim 1, wherein the metamaterial element has a gap, and 　　　　　　　the active element is connected to the gap.

3. The metamaterial device according to claim 1 or 2, wherein the reconfigurable intelligent surface portion further comprises, sequentially from the metamaterial layer, a spacer layer made of a dielectric, and a reflection layer configured to reflect the millimeter wave.

4. The metamaterial device according to claim 1 or 2, wherein the reconfigurable intelligent surface portion and the solar cell portion are arranged in a direction vertical to a surface on which the metamaterial cells are arranged.

5. The metamaterial device according to claim 4, wherein the reconfigurable intelligent surface portion is transparent within a wavelength range of light necessary for generating the electric power in the solar cell portion.

6. The metamaterial device according to claim 1 or 2, further comprising: 　　　　　　　a solar cell charge controller to which a DC current generated by the solar panel is input; 　　　　　　　a battery to which a part of the DC current is input from the solar cell charge controller; 　　　　　　　an inverter to which a remaining part of the DC current is input from the solar cell charge controller and which is configured to convert the remaining part of the DC current into an AC current; and 　　　　　　　a RIS controller to which a part of the AC current is input and which is configured to control the active element.

7. A metamaterial device in which a millimeter wave and sunlight enter, comprising: 　　　　　　　a reconfigurable intelligent surface portion configured to beamform the millimeter wave; and 　　　　　　　a solar cell portion formed by a solar panel configured to convert the sunlight into electric power, 　　　　　　　wherein the reconfigurable intelligent surface portion comprises 　　　　　　　a metamaterial layer formed by metamaterial cells arranged in an array, 　　　　　　　the metamaterial cell comprises: 　　　　　　　a metamaterial element; and 　　　　　　　a dielectric filling portion arranged around the metamaterial element, and 　　　　　　　the reconfigurable intelligent surface portion is arranged on the solar panel.

8. A transparent member to which a metamaterial device defined in claim 1 or 7 is attached, 　　　　　　　wherein a reconfigurable intelligent surface portion is transparent within a wavelength range of light necessary for generating electric power in a solar cell portion, and 　　　　　　　the solar cell portion passes at least a part of the sunlight.

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