Radio wave propagation control member and antenna system

Abstract

Provided are a radio wave propagation control member that can two-dimensionally widen a beam width and an antenna system.　A radio wave propagation control member according to the present invention includes a substrate and a metal layer that is provided on the substrate. As seen in plan view, the metal layer has a plurality of rectangular regions. Each rectangular region has a band-like pattern that is formed by the metal layer. When λ0 is the wavelength in free space of radio waves that are to arrive at the metal layer, the length of the short sides of the rectangular regions is no more than 2λ0. The band-like pattern of each of the rectangular regions refracts the radio waves in a prescribed direction. The directions in which the band-like patterns of the plurality of rectangular regions refract the radio waves are different from each other.

Description

Radio wave propagation control member and antenna system

[0001] The present disclosure relates to a radio wave propagation control member and an antenna system.

[0002] A conventional reflectarray transmits radio waves from a base station used for communication to a receiving area, and the reflector has a plurality of reflectors, each having identical cells arranged at a predetermined interval, and at least two of the plurality of reflectors have identical cells arranged at different intervals and have different reflection angles, thereby forming a receiving area. The reflectors are of a transmission type that can be attached to glass (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2022-108025

[0004] However, there is no disclosure of a specific configuration that can be used when the reflector of the reflectarray is a transmission type. In general, there is no known configuration for adjusting the beam width in a transmission type, particularly for expanding the beam width two-dimensionally.

[0005] Therefore, an object of the present invention is to provide a radio wave propagation control member and an antenna system that can widen the beam width two-dimensionally.

[0006] A radio wave propagation control member according to an embodiment of the present disclosure includes a base and a metal layer provided on the base, the metal layer having a plurality of rectangular regions in a plan view, each of the rectangular regions having a band-like pattern formed by the metal layer, and the rectangular regions are configured to define a wavelength in free space of a radio wave arriving at the metal layer as λ ０ Then, the length of the short side is 2λ ０ The band-shaped pattern of each rectangular area refracts the radio waves in a predetermined direction, and the directions in which the radio waves are refracted by the band-shaped patterns of the plurality of rectangular areas are different from one another.

[0007] It is possible to provide a radio wave propagation control member and an antenna system that can widen the beam width two-dimensionally.

[0008] 1 is a diagram showing an example of the configuration of a window glass provided with a radio wave propagation control member of an embodiment. FIG. 1 is a diagram showing an example of the path of a component of radio waves radiated from a base station antenna that passes through the center of a rectangular area. FIG. 2 is a diagram showing an example of the path of a component of radio waves radiated from a base station antenna that passes through the center of a rectangular area. FIG. 3 is a diagram showing an example of the path of a component of radio waves radiated from a base station antenna that passes through the center of a rectangular area. FIG. 4 is a diagram showing an example of the intensity distribution of radio waves incident on a propagation control layer in a simulation. FIG. 5 is a diagram showing an example of a simulation result of a simulation model of the propagation control layer and the intensity of radio waves at a position sufficiently distant from the radio wave propagation control member in the +Z direction. FIG. 6 is a diagram showing an example of a simulation result of a simulation model of the propagation control layer and the intensity of radio waves at a position sufficiently distant from the radio wave propagation control member in the +Z direction. FIG. 7 is a diagram showing an example of a simulation result of a simulation model of the propagation control layer and the intensity of radio waves at a position sufficiently distant from the radio wave propagation control member in the +Z direction. FIG. 7 is a diagram showing an example of a simulation model of the propagation control layer and a simulation result of the intensity of radio waves at a position sufficiently distant from the radio wave propagation control member in the +Z direction. FIG. 8 is a diagram showing an example of a simulation model of the propagation control layer and a simulation result of the intensity of radio waves at a position sufficiently distant from the radio wave propagation control member in the +Z direction. FIG. 9 is a diagram showing an example of the overall configuration of a propagation control layer made of a Fresnel zone plate. FIG. 10 is a diagram showing an example of a conductor 120A included in a frequency selective surface. FIG. 11 is a diagram showing an example of an experimental result using the propagation control layer shown in FIG.

[0009] Hereinafter, embodiments to which the radio wave propagation control member and antenna system of the present disclosure are applied will be described. In the following, the same elements will be denoted by the same reference numerals, and duplicated descriptions may be omitted.

[0010] In the following description, the XYZ coordinate system is defined. The direction parallel to the X axis (X direction), the direction parallel to the Y axis (Y direction), and the direction parallel to the Z axis (Z direction) are perpendicular to each other. For ease of explanation, the -Z direction may be referred to as the lower side or bottom, and the +Z direction may be referred to as the upper side or top. Planar view refers to viewing from the XY plane. In the following description, the length, width, thickness, etc. of each part may be exaggerated to make the configuration easier to understand. Terms such as parallel, right angle, orthogonal, horizontal, vertical, and up and down are intended to allow for deviations that do not impair the effects of the embodiments. The X direction is an example of a first axis direction, and the Y direction is an example of a second axis direction.

[0011] In the following description, "radio waves" refers to a type of electromagnetic wave, and generally, electromagnetic waves below 3 THz are called radio waves. Hereinafter, electromagnetic waves emitted from outdoor base stations or relay stations will be referred to as "radio waves," and electromagnetic waves in general will be referred to as "electromagnetic waves." In addition, in the following, "millimeter waves" or "millimeter wave band" will include not only the frequency band of 30 GHz to 300 GHz, but also the quasi-millimeter wave band of 24 GHz to 30 GHz.

[0012] The radio waves received and propagated by the radio wave propagation control member and antenna system of the embodiment are preferably in the millimeter wave band of the fifth generation mobile communication system (5G) or in the frequency band of 0.7 GHz to 100 GHz, including Sub-6. Furthermore, the radio waves received and propagated by the radio wave propagation control member and antenna system of the embodiment may be Long Term Evolution (LTE), LTE-Advanced (LTE-A), or Ultra Mobile Broadband (UMB). Furthermore, the radio waves received and propagated by the radio wave propagation control member and antenna system of the embodiment may be IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.20, Ultra-Wideband (UWB), Bluetooth (registered trademark), Low Power Wide Area (LPWA), or the like. Unless otherwise specified, the following description will use millimeter wave band radio waves as an example.

[0013] 1 is a diagram showing an example of the configuration of a window glass 10 provided with a radio wave propagation control member 100 according to an embodiment. The window glass 10 is provided in a window of a building (not shown). The −Z direction side of the window glass 10 is the indoor side of the building, and the +Z direction side of the window glass 10 is the outdoor side of the building.

[0014] As an example, the radio wave propagation control member 100 is provided on the indoor main surface of the window glass 10, but it may also be provided on the outdoor main surface of the window glass 10. A base station BS is provided on the indoor side of the building in which the window glass 10 is provided. The base station BS has a base station antenna 50. The antenna system 200 of the embodiment includes the base station antenna 50 and the radio wave propagation control member 100 provided on the window glass 10.

[0015] Base station BS emits a beam of radio waves from base station antenna 50. The beam of radio waves arrives at radio wave propagation control member 100. Building walls act as a barrier to millimeter-wave band radio waves, blocking them or significantly attenuating them, but millimeter-wave band radio waves can pass through window glass 10. Therefore, radio waves that have passed through radio wave propagation control member 100 pass through window glass 10 and propagate to the outside of the building. Note that, hereinafter, the beam of radio waves may be simply referred to as a beam.

[0016] <Configuration of radio wave propagation control member 100> Radio wave propagation control member 100 includes a base 110 and a propagation control layer 120. In Fig. 1, the area where propagation control layer 120 is provided is indicated by a dashed line, and a plurality of rectangular regions 121 included in propagation control layer 120 are also shown. Fig. 1 shows, as an example, 36 rectangular regions 121 arranged in 6 rows x 6 columns, that is, six in the X direction (six columns) and six in the Y direction (six rows).

[0017] <Base 110> The base 110 is formed of any material that is transparent to radio waves radiated from the base station BS and can support the propagation control layer 120. Being transparent to the radiated radio waves means, for example, that the transmission loss is 10 dB or less. The base 110 being transparent to the radiated radio waves means that the transmission loss of the substrate is 10 dB or less, preferably 6 dB or less, more preferably 3 dB or less, and even more preferably 1 dB or less. The base 110 may also be transparent to visible light. "Transparent" to visible light means that the visual transmittance is at least 40% or more, preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more. As an example, a glass plate is used as the base 110. Examples of glass plates that satisfy the above conditions include soda-lime glass, alkali-free glass, Pyrex (registered trademark) glass, and quartz glass.

[0018] A resin substrate (resin film) may also be used as the base 110. Examples of resin materials that satisfy the above conditions include acrylic resins such as polymethyl methacrylate, cycloolefin resins, polycarbonate resins, and polyethylene terephthalate (PET).

[0019] As one example, a propagation control layer 120 realized by a metal layer is formed on the outdoor surface of the base 110. The base 110 provided with such a propagation control layer 120 is attached to the indoor main surface of the window glass 10 with an adhesive, for example. The adhesive may be applied to the entire surface of the propagation control layer 120 facing the window glass 10. The propagation control layer 120 may also be formed on the indoor surface of the base 110. In this case, the propagation control layer 120 is located on the surface opposite to the surface of the base 110 that is attached to the window glass 10, and therefore the outdoor surface of the base 110 and the indoor main surface of the window glass 10 may be attached with an adhesive.

[0020] <Paths of Radio Waves by Propagation Control Layer 120> In Fig. 1, six arrows indicate the paths of components of radio waves radiated from the base station antenna 50 that are incident on the centers of six rectangular regions 121. In addition to Fig. 1, Figs. 2A to 2C are used to explain the paths of radio waves. Figs. 2A to 2C are diagrams showing examples of paths of components of radio waves radiated from the base station antenna 50 that pass through the centers of the rectangular regions 121. Figs. 1 and 2A to 2C show paths of components of radio waves radiated from the base station antenna 50 that are incident on the centers of the rectangular regions 121 and then emitted, but below these paths will be simply described as paths of radio waves.

[0021] 2A to 2C omit window glass 10 and show base station antenna 50 and radio wave propagation control member 100. In the description of Figures 2A to 2C , rectangular region 121 of propagation control layer 120 included in radio wave propagation control member 100 is assumed to exist along the XY plane as shown in Figure 1 .

[0022] 2A shows the path of radio waves in the XZ plane (horizontal plane), and FIGS. 2B and 2C show the path of radio waves in the YZ plane. The YZ plane shows a cross section of the radio wave propagation control member 100 as seen from the side. For ease of understanding, the path of radio waves is shown as a path passing through the center of each rectangular region 121.

[0023] 1 shows six radio wave paths propagating from base station antenna 50 to rectangular areas 121 in six columns and the fourth row from the top of radio wave propagation control member 100. Radio waves also propagate to rectangular areas 121 in the first to third rows and the fifth and sixth rows from the top of radio wave propagation control member 100, but for ease of understanding, only the fourth row is shown in FIG.

[0024] 2A shows, in a horizontal plane view, the paths of six radio waves that are incident on the six rectangular regions 121 in the fourth row. The angles of incidence and emergence of the six radio wave paths when passing through the centers of the six rectangular regions 121 with respect to the radio wave propagation control member 100 are different from one another. Furthermore, the angles of incidence and emergence of the radio waves when passing through the centers of the respective rectangular regions 121 with respect to the radio wave propagation control member 100 are, for example, equal. Furthermore, the paths of the six radio waves that pass through the six rectangular regions 121 in the first to third rows and the fifth and sixth rows from the top of the radio wave propagation control member 100 are equal to the paths of the six radio waves that pass through the six rectangular regions 121 in the fourth row shown in FIG. 2A.

[0025] The paths of the six radio waves actually represent the paths of components of radio waves having a wider beam width that pass through the center of rectangular region 121. For this reason, the angles of incidence and emergence of the six radio wave paths with respect to radio wave propagation controlling member 100 when passing through the centers of six rectangular regions 121 are different from one another, making it possible to widen the beam width two-dimensionally.

[0026] 2B also shows the paths of six radio waves incident on six rectangular regions 121 in the first to sixth rows in a YZ side view. The six radio waves are incident at different angles when they enter the centers of the six rectangular regions 121 in the first to sixth rows, but the exit angles when they exit to the outdoors from the six rectangular regions 121 in the first to sixth rows are, for example, equal. The radio wave propagation control member 100 refracts each radio wave so that the angles of incidence and exit angles of the six radio waves have the relationship described above. The paths of the six radio waves in a YZ side view shown in FIG. 2B are, for example, equal in the six rectangular regions 121 in the first to sixth columns of each row.

[0027] 2B , as an example, six radio waves are emitted downward outdoors from the six rectangular regions 121 in the first to sixth rows, allowing millimeter waves such as those of a fifth-generation mobile communication system (5G) to reach below the window glass 10 on which the radio wave propagation control member 100 is provided. For example, if the window glass 10 is located at a high position, such as on the second floor or higher of a building, radio waves emitted from a base station BS provided inside the building can be supplied to mobile terminals such as smartphones and tablet computers carried by people on the ground outside the building, such as on a road or in a plaza. In other words, a communication area can be provided in which mobile terminals such as smartphones and tablet computers carried by people on the ground outside the building, such as on a road or in a plaza, can communicate with the base station BS provided inside the building.

[0028] FIG. 2C also shows a modified example of the paths of six radio waves incident on the six rectangular regions 121 in the first to sixth rows in a YZ side view. In FIG. 2C , similar to FIG. 2B , the six radio waves are incident at different angles when they hit the centers of the six rectangular regions 121 in the first to sixth rows. In FIG. 2C , the six radio waves are emitted to the outdoors from the six rectangular regions 121 in the first to sixth rows at different exit angles, and the six radio waves propagate to approximately the same position in a YZ side view. The radio wave propagation control member 100 refracts each radio wave so that the angles of incidence and exit angles of the six radio waves have the relationship described above. Furthermore, the paths of the six radio waves in a YZ side view shown in FIG. 2C are, for example, the same for the six rectangular regions 121 in the first to sixth columns of each row.

[0029] In Figure 2C , as an example, six radio waves are emitted from the six rectangular regions 121 in the first to sixth rows to approximately the same position below the outdoor side, allowing millimeter waves such as those of a fifth-generation mobile communication system (5G) to reach below the window glass 10 on which the radio wave propagation control member 100 is provided. In Figure 2C , radio waves can be concentrated in an area that is narrower in width in the Z direction than in Figure 2B . For example, if the window glass 10 is located at a high position, such as on the second floor or higher of a building, a mobile terminal such as a smartphone or tablet computer carried by a person on the ground outside the building, such as on a road or in a plaza, can communicate with a base station BS provided inside the building, providing a communication area that is narrower in width in the Z direction.

[0030] 2B and 2C, the radio wave propagation control member 100 is described as refracting radio waves downward, but the radio wave propagation control member 100 may refract radio waves in directions other than downward. Therefore, by using the radio wave propagation control member 100, radio waves can be refracted in various directions.

[0031] <Simulation> As an example, propagation control layer 120 of radio wave propagation control member 100 as described above can be realized by a Fresnel lens. Here, the results of a simulation in which propagation control layer 120 shown in FIG. 1 is realized by a Fresnel lens will be described.

[0032] Fig. 3 is a diagram showing an example of the intensity distribution of radio waves incident on the propagation control layer 120 in a simulation. In Fig. 3, the dimension in the X direction (-150 mm to 150 mm) and the dimension in the Y direction (-150 mm to 150 mm) represent the range in which the propagation control layer 120 exists when viewed from the XY plane. The multiple rectangular regions 121 of the propagation control layer 120 are arranged in the range of -150 mm to 150 mm in the X direction and -150 mm to 150 mm in the Y direction. The position where the X coordinate and the Y coordinate are 0 mm is the center of the propagation control layer 120 when viewed from the XY plane.

[0033] In the simulation, the frequency of the radio wave is, for example, 28 GHz (wavelength λ ０ = 11 mm). As an example, the center of the base station antenna 50 was set at a position of (X, Y, Z) = (0 m, 0 m, -0.5 m). In other words, the center of the base station antenna 50 was placed at a position 0.5 m in the -X direction with respect to the center of the propagation control layer 120.

[0034] Furthermore, the simulation conditions were set so that the incident angle and the outgoing angle of the radio wave are equal when viewed from the XZ plane as shown in FIG. 2A when passing through the propagation control layer 120. Furthermore, the simulation conditions were set so that the outgoing angle of the radio wave is an elevation angle of -60 degrees when viewed from the YZ side as shown in FIG. 2B when passing through the propagation control layer 120. The elevation angle is the angle between a certain direction vector viewed from the origin and its projection onto a horizontal plane (XZ plane) with the center of the propagation control layer 120 as the origin of the XYZ coordinate system. The sign of the elevation angle is positive in the +Y direction from the horizontal plane (XZ plane). For example, the Y direction is an elevation angle of +90 degrees, and the -Y direction is an elevation angle of -90 degrees. Furthermore, the following description will use an azimuth angle. The azimuth angle is the angle between the Z axis and the projection of a certain direction vector viewed from the origin onto the horizontal plane (XZ plane) with the center of the propagation control layer 120 as the origin of the XYZ coordinate system. The sign of the azimuth angle is positive when the counterclockwise direction from the Z axis to the X axis when viewing the horizontal plane (XZ plane) from the +Y direction. For example, the X direction is an azimuth angle of +90 degrees, and the -X direction is an azimuth angle of -90 degrees.

[0035] When radio waves were emitted in the +Z direction from the base station antenna 50 arranged as described above, the intensity distribution shown in Fig. 3 was obtained on the XY plane. When viewed from the XY plane, the radio wave intensity distribution showed a distribution in which the intensity was strongest at the center of the propagation control layer 120 and gradually weakened as it went outward in the radial direction.

[0036] 4A to 4C are diagrams showing a simulation model of the propagation control layer 120 and an example of the simulation results of the intensity of radio waves at a position sufficiently distant from the radio wave propagation control member 100. In each of FIGS. 4A to 4C, the left side shows the Fresnel lens pattern (simulation model) of the propagation control layer 120 used in the simulation. In the Fresnel lens pattern, the white parts are areas where the phase of the radio waves (transmitted waves) that have passed through the propagation control layer 120 is +180 degrees, and the black parts are areas where the phase of the transmitted waves is -180 degrees. The areas with a gradation between white and black are areas where the phase of the transmitted waves is delayed as the color becomes darker. In each of FIGS. 4A to 4C, the right side shows the intensity distribution of radio waves that have passed through the propagation control layer 120 composed of the Fresnel lens on the left. The intensity distribution shown on the right side was calculated as an intensity distribution obtained at a position sufficiently distant from the radio wave propagation control member 100. In the intensity graph on the right, the horizontal axis represents the azimuth angle, and the vertical axis represents the elevation angle. Note that the position where both the azimuth angle and the elevation angle are 0 degrees is the position on the Z axis.

[0037] 4A to 4C show the Fresnel lens pattern (left side) and the radio wave intensity distribution (right side) when the propagation control layer 120 is not divided in the Y direction but is divided in the X direction to provide multiple rectangular regions 121. That is, each rectangular region 121 is a strip-shaped rectangular region 121 having a length of 300 mm in the Y direction and a length in the X direction obtained by dividing a 300 mm section into multiple sections.

[0038] Furthermore, when dividing propagation control layer 120 in the X direction, the division was performed so that the angular difference (angle difference in the azimuth angle direction) between adjacent paths connecting base station antenna 50 and the center of each rectangular region 121 in the XY plane view was less than 1 degree in FIG. 4A , 1 degree in FIG. 4B , and 5 degrees in FIG. 4C . An angular difference of 1 degree between adjacent paths in the XZ plane view corresponds to an angular difference of 1 degree between adjacent paths among the six paths shown in FIG. 2A . An angular difference of 5 degrees between adjacent paths in the XZ plane view corresponds to an angular difference of 5 degrees between adjacent paths among the six paths shown in FIG. 2A . Furthermore, an angular difference of less than 1 degree between adjacent paths in the XZ plane view means that the angular difference between adjacent paths among the six paths shown in FIG. 2A is less than 1 degree.

[0039] In the radio wave intensity distribution shown on the right side of Figure 4A, it was confirmed that the radio wave intensity was high (approximately 20 dBi) below the center where the azimuth and elevation angles were 0 degrees, and that the intensity was greater in the direction of an elevation angle of -60 degrees. This coincided with the radio wave emission angle (-60 degrees elevation angle) set in the simulation conditions. Furthermore, in the azimuth angle direction, it was confirmed that the intensity tended to be greater at the center (0 degrees) side than at both ends (±90 degrees) up to the region where the absolute value of the elevation angle was small (approximately -25 degrees). No null points were confirmed within the region of high radio wave intensity (approximately 20 dBi or more).

[0040] In the radio wave intensity distribution shown on the right side of Figure 4B, similar to Figure 4A, it was confirmed that the radio wave intensity was high (approximately 20 dBi) below the center where the azimuth and elevation angles were 0 degrees, and the intensity was higher in the direction of an elevation angle of -60 degrees. This coincided with the radio wave emission angle (-60 degrees elevation angle) set in the simulation conditions. Furthermore, in the azimuth angle direction, a tendency was confirmed where the intensity was higher at the center (0 degrees) side than at both ends (±90 degrees) up to the region where the absolute value of the elevation angle was small (approximately -25 degrees). Compared to Figure 4A, the uniformity of the radio wave intensity was slightly reduced, but no null points were confirmed in the region where the radio wave intensity was high (approximately 20 dBi or more).

[0041] Furthermore, although not shown in Figures 4A to 4C, a simulation using multiple rectangular regions 121 in which the propagation control layer 120 was divided so that the angular difference between adjacent paths when viewed in the XZ plane (angle difference in the azimuth direction) was 2 degrees also yielded results that were approximately the same as those in Figure 4B, and almost no null points were observed in areas where the radio wave strength was high (approximately 20 dBi or more).

[0042] In the radio wave intensity distribution shown on the right side of Figure 4C, below the center where the azimuth angle and elevation angle are 0 degrees, we were able to confirm areas where the radio wave intensity was high (approximately 20 dBi), particularly in the direction of an elevation angle of -60 degrees, but we also confirmed that streaky null points occurred.

[0043] From the above, it has been found that by using a plurality of rectangular regions 121 obtained by dividing propagation control layer 120 so that the angular difference between adjacent paths when viewed from the XZ plane (angle difference in the azimuth angle direction) is 2 degrees or less, it is possible to provide a communication area below window glass 10 on the outdoor side of a building. Note that here, the simulation results in which radio waves are refracted downward at the output side of radio wave propagation control member 100 have been described. However, by setting the elevation angle or azimuth angle of the output angle of the radio waves in any direction under the simulation conditions, a pattern of propagation control layer 120 for refracting the radio waves in that direction can be obtained, and it is thought that the radio waves are refracted in that direction.

[0044] 5A to 5C are diagrams showing an example of a simulation model of the propagation control layer 120 and simulation results of the intensity of radio waves at a position sufficiently distant from the radio wave propagation control member 100. In each of FIGS. 5A to 5C, the left side shows the Fresnel lens pattern (simulation model) of the propagation control layer 120 used in the simulation. In each of FIGS. 5A to 5C, the right side shows the intensity distribution of radio waves transmitted through the propagation control layer 120 composed of the Fresnel lens on the left. The intensity distribution shown on the right is calculated as an intensity distribution obtained at a position sufficiently distant from the radio wave propagation control member 100. For the intensity on the right side, the horizontal axis represents the azimuth angle, and the vertical axis represents the elevation angle. Note that the position where the azimuth angle and the elevation angle are both 0 degrees is the position on the Z axis.

[0045] 5A to 5C show a Fresnel lens pattern (left side) and a radio wave intensity distribution (right side) when a plurality of rectangular regions 121 are provided by dividing the propagation control layer 120 in the X direction and the Y direction. That is, each rectangular region 121 is a rectangular region 121 whose length in the X direction is obtained by dividing a section of 300 mm into a plurality of sections, and whose length in the Y direction is obtained by dividing a section of 300 mm into a plurality of sections. As an example, the divisions in the X direction and the Y direction are equal.

[0046] Furthermore, when dividing propagation control layer 120 in the X direction and Y direction, the division was performed so that, for paths connecting base station antenna 50 and the center of each rectangular region 121 in the XY plane view, the angular difference between adjacent paths in the XZ plane view (angular difference in the azimuth angle direction) and the angular difference between adjacent paths in the YZ plane view (angular difference in the elevation angle direction) are both less than 1 degree in Fig. 5A, 1 degree in Fig. 5B, and 5 degrees in Fig. 5C. An angular difference of 1 degree between adjacent paths in the XZ plane view and the XZ plane view corresponds to an angular difference of 1 degree between adjacent paths of the six paths shown in Fig. 2A and an angular difference of 1 degree between adjacent paths of the six paths shown between base station antenna 50 and radio wave propagation control member 100 in Fig. 2B. An angular difference of 5 degrees between adjacent paths when viewed in the XZ plane corresponds to an angular difference of 5 degrees between adjacent paths of the six paths shown in Fig. 2A and an angular difference of 5 degrees between adjacent paths of the six paths shown in Fig. 2B between base station antenna 50 and radio wave propagation control member 100. Furthermore, an angular difference of less than 1 degree between adjacent paths when viewed in the XZ plane corresponds to an angular difference of less than 1 degree between adjacent paths of the six paths shown in Fig. 2A and an angular difference of less than 1 degree between adjacent paths of the six paths shown in Fig. 2B between base station antenna 50 and radio wave propagation control member 100.

[0047] In the radio wave intensity distribution shown on the right side of Figure 5A, it was confirmed that the radio wave intensity was high (approximately 20 dBi) below the center where the azimuth and elevation angles were 0 degrees, and that the intensity was greater in the direction of an elevation angle of -60 degrees. This coincided with the radio wave emission angle (-60 degrees elevation angle) set in the simulation conditions. Furthermore, in the azimuth angle direction, it was confirmed that the intensity tended to be greater at the center (0 degrees) side than at both ends (±90 degrees) up to the region where the absolute value of the elevation angle was small (approximately -25 degrees). No null points were confirmed in the region where the radio wave intensity was high (approximately 20 dBi or more).

[0048] In the radio wave intensity distribution shown on the right side of Figure 5B, similar to Figure 5A, it was confirmed that the radio wave intensity was high (approximately 20 dBi) below the center where the azimuth and elevation angles were 0 degrees, and the intensity was high in the direction of an elevation angle of -60 degrees. This coincided with the radio wave emission angle (-60 degrees elevation angle) set in the simulation conditions. Furthermore, in the azimuth angle direction, a tendency was confirmed where the intensity was higher at the center (0 degrees) side than at both ends (±90 degrees) up to the region where the absolute value of the elevation angle was small (approximately -25 degrees). Compared to Figure 5A, the uniformity of the radio wave intensity was slightly reduced, but no null points were confirmed in the region where the radio wave intensity was high (approximately 20 dBi or more).

[0049] Furthermore, although not shown in Figures 5A to 5C, a simulation using multiple rectangular regions 121 in which the propagation control layer 120 was divided so that the angular difference between adjacent paths when viewed in the XZ plane (angle difference in the azimuth direction) was 2 degrees also yielded results that were approximately the same as those in Figure 5B, and almost no null points were observed in areas where the radio wave strength was high (approximately 20 dBi or more).

[0050] In the radio wave intensity distribution shown on the right side of Fig. 5C, below the center where the azimuth angle and elevation angle are 0 degrees, areas where the radio wave intensity is high (about 20 dBi) were confirmed, particularly in the direction of an elevation angle of -60 degrees, but it was also confirmed that streaky null points occurred. In the radio wave intensity distribution shown in Fig. 5C, compared to the radio wave intensity distribution shown in Fig. 4C, the distribution appears to have an increased number of streaky null points existing in the azimuth angle direction (the horizontal direction on the right side of Fig. 5C).

[0051] From the above, it has been found that by using a plurality of rectangular regions 121 obtained by dividing propagation control layer 120 so that the angular difference between adjacent paths when viewed in the XZ plane (angle difference in the azimuth angle direction) is 2 degrees or less and the angular difference between adjacent paths when viewed in the YZ plane (angle difference in the elevation angle direction) is 2 degrees or less, it is possible to provide a communication area below window glass 10 on the outdoor side of a building. Note that here, the simulation results in which radio waves are refracted downward at the output side of radio wave propagation control member 100 have been described. However, by setting the elevation angle or azimuth angle of the output angle of the radio waves in any direction under the simulation conditions, a pattern of propagation control layer 120 for refracting the radio waves in that direction can be obtained, and it is thought that the radio waves are refracted in that direction.

[0052] <Summary of Simulation Results> From the simulation results shown in Figures 4A to 4C and Figures 5A to 5C, it was found that by using multiple rectangular areas 121 into which the propagation control layer 120 is divided so that the angular difference between adjacent paths when viewed in the XZ plane or the YZ plane is 2 degrees or less, it is possible to provide a communication area below the outdoor side of the window glass 10 of a building.

[0053] In this way, a communication area can be provided below the outdoor side of window glass 10 of a building when propagation control layer 120 realized by a Fresnel lens having the pattern shown on the left side of Figures 4A, 4B, 5A, and 5B is used.

[0054] The Fresnel lens pattern shown on the left side of FIGS. 4A and 4B includes a plurality of rectangular regions 121 obtained by dividing the propagation control layer 120 in the X direction without dividing it in the Y direction, and the wavelength in free space of the radio wave arriving at the propagation control layer 120 is λ ０ Then, the length of the short side (length in the X direction) is 2λ ０ The rectangular regions 121 are arranged in the X and Y directions. There is no particular limitation on the length of the long side of the rectangular regions 121 (length in the Y direction).

[0055] 5A and 5B includes a plurality of rectangular regions 121 obtained by dividing the propagation control layer 120 in the X direction and the Y direction, and the wavelength in free space of the radio wave arriving at the propagation control layer 120 is set to λ０ Then, the length of the short side is 2λ ０ The length of the long side (length in the Y direction) is also 2λ ０ The rectangular regions 121 are arranged in the X and Y directions. When the lengths of the short and long sides are the same, the rectangular region 121 becomes a square.

[0056] Each of the multiple rectangular regions 121 included in the Fresnel lens pattern shown on the left side of Figures 4A, 4B, 5A, and 5B has a band-like pattern, and the band-like pattern of each rectangular region 121 refracts radio waves downward (in a predetermined direction), with the directions of radio wave refraction by the band-like patterns of the multiple rectangular regions 121 being different from one another. In Figures 4A and 5A, the band-like pattern of each rectangular region 121 is band-like within each rectangular region 121 so as to correspond to the portion below the center of the concentric Fresnel lens pattern, and is also band-like across adjacent rectangular regions 121 in the X direction. In other words, the band-like patterns of adjacent rectangular regions 121 are connected to each other. This is also approximately the same in Figures 4B and 5B. Note that the length of the rectangular region 121 in Figure 4A in the X direction is approximately 1 mm, i.e., approximately 0.09λ. ０ The length of the rectangular region 121 in the X direction in FIG. 4B is about 9 mm, that is, about 0.81λ ０ The length of the rectangular region 121 in FIG. 5A in the X and Y directions is about 1 mm, that is, about 0.09λ. ０ The length of the rectangular region 121 in FIG. 5B in the X and Y directions is about 9 mm, that is, about 0.81λ ０ When the angle difference between adjacent paths is 2 degrees, the length of the rectangular region 121 in the X direction is about 17 mm, that is, about 1.55λ ０ Since the rectangular area 121 is divided with the azimuth angle and elevation angle set to a constant value, the farther it is from the origin, the longer the lengths in the X and Y directions. As a result, the length in the X direction (length of the short side) of the rectangular area 121 is 1.5λ ０ More preferably, λ is equal to or less than λ ０ More preferably, it is 0.5λ or less. ０ Even more preferably, it is 0.1λ or less. ０It has been found that it is even more preferable that the length of the rectangular region 121 in the Y direction (the length of the long side) is as follows:

[0057] Furthermore, the angle formed by the propagation directions of radio waves passing through adjacent rectangular areas 121, expressed as the angle formed by paths passing through the centers of the rectangular areas 121, is 2 degrees or less.

[0058] Furthermore, the belt-like patterns of adjacent rectangular regions 121 are arranged in a curved line. In particular, as shown in Figures 4A and 5A, when the angular difference is less than 1 degree, the Fresnel lens pattern is a continuous curved line pattern of the belt-like patterns of adjacent rectangular regions 121.

[0059] Furthermore, the difference in the direction of incidence of radio waves incident on adjacent rectangular areas 121 from the base station antenna 50 is 2 degrees or less.

[0060] <Propagation control layer 120 configured with a Fresnel zone> Fig. 6A is a diagram showing an example of the overall configuration of the propagation control layer 120 configured with a Fresnel zone plate. Fig. 6A also shows the base 110 on which the propagation control layer 120 is formed. The base 110 on which the propagation control layer 120 is formed is configured with a Fresnel zone plate, not a Fresnel lens. The propagation control layer 120 configuring the Fresnel zone is an example of a metal layer.

[0061] Propagation control layer 120 shown in Fig. 6A is composed of a metal layer formed on the surface of base 110. Propagation control layer 120 shown in Fig. 6A has, as an example, a length of 2000 mm in the X direction and a length of 400 mm in the Y direction.

[0062] FIG. 6B is a diagram showing an example of a conductor 120A included in a frequency selective surface (FSS). The conductor 120A is an example of a unit pattern conductor. FIG. 6B shows three adjacent conductors 120A as an example. In FIG. 6B, the black portions are portions made of metal. Each conductor 120A is provided in a square unit cell 120U, which is a unit region. Three adjacent conductors 120A are arranged within three adjacent unit cells 120U.

[0063] The conductor 120A has a shape in which linear conductors extending along the four sides of the unit cell 120U are added to the ends of plus-shaped conductors extending in the X and Y directions. The four linear conductors extending along the four sides are separated from each other at the four corners of the unit cell 120U. As an example, the line width of each linear portion of the conductor 120A is 0.1 mm, and the length of the unit cell 120U in the X and Y directions is 1.5 mm. That is, the pitch between adjacent conductors 120A in the X direction is 1.5 mm. The length of the linear conductors extending along the four sides of the unit cell 120U is 1.0 mm, and the gap between adjacent conductors 120A is, for example, 0.13 mm.

[0064] Each conductor 120A is made of zinc oxide (ZnO), tin oxide (SnO ２ The conductors 120A may be formed of a transparent conductive film such as tin-doped indium oxide (ITO) or indium oxide-tin oxide (IZO), a metal nitride such as titanium nitride (TiN) or chromium nitride (CrN), or a low-e film for low-e (low emissivity) glass. Each conductor 120A may be formed of a mesh-like metal thin film such as copper, nickel, or gold.

[0065] The propagation control layer 120 shown in Fig. 6A is an arrangement of a large number of conductors 120A as shown in Fig. 6B. The shape of the conductors 120A shown in Fig. 6B is merely an example, and the propagation control layer 120 may include conductors 120A having various shapes. Since the amount of delay that the conductors 120A cause to delay radio waves varies depending on their shape, arranging conductors 120A of various shapes can refract radio waves. Note that the metal layers included in the conductors 120A may be two or more layers.

[0066] The outer edges of the unit cells 120U of adjacent conductors 120A are in contact with each other. For example, by arranging the three unit cells 120U shown in FIG. 6B so that the corners of their outer edges are in contact with each other, a band-shaped pattern as shown in FIG. 6A can be realized. The band-shaped pattern of the propagation control layer 120 shown in FIG. 6A forms a metasurface in which multiple unit pattern conductors are arranged.

[0067] Each rectangular region 121 includes, for example, a plurality of unit cells 120U. Therefore, the plurality of conductors 120A form a band-like pattern within each rectangular region 121. The plurality of conductors 120A forming a band-like pattern means that the outer edges of adjacent unit cells 120U included in the plurality of unit cells 120U for the plurality of conductors 120A are in contact with each other.

[0068] Furthermore, by connecting the strip patterns of adjacent rectangular regions 121 to each other, a continuous strip pattern is obtained across the entire propagation control layer 120 having a large size, such as 2000 mm in the X direction and 400 mm in the Y direction, as shown in FIG. 6A . The strip patterns of adjacent rectangular regions 121 being connected to each other means that the outer edges of the unit cells 120U located at the boundary between the adjacent rectangular regions 121 are in contact with each other. In particular, as the size of each rectangular region 121 becomes smaller, the strip patterns of adjacent rectangular regions 121 tend to be smoothly connected to each other. Furthermore, by connecting the strip patterns of adjacent rectangular regions 121 smoothly to each other, the strip patterns of adjacent rectangular regions 121 are arranged in a curved line.

[0069] Note that, as the size of each rectangular region 121 is reduced, each rectangular region 121 may include one unit cell 120U. In other words, each rectangular region 121 may include one conductor 120A. In such a case, it is sufficient that a plurality of rectangular regions 121, each including one conductor 120A, are arranged, and radio waves refracted by the plurality of conductors 120A propagate in a plurality of refraction directions, as shown in, for example, FIGS. 2A to 2C .

[0070] <Experimental Results> Figure 7 is a diagram showing an example of the experimental results using the propagation control layer 120 shown in Figure 6. The propagation control layer 120 shown in Figure 6 was provided on window glass 10 on the fifth floor of a building, and radio waves were emitted from base station antenna 50 installed indoors on the fifth floor of the building. The intensity distribution of the radio waves was measured within an area 35 m x 11 m and 1.2 m above the ground, 3 m away from the building, and expressed as a cumulative distribution function (CDF) of the received power. In Figure 7, the solid line shows the measurement result when the propagation control layer 120 was provided on the window glass 10, and the dashed line shows the measurement result when the propagation control layer 120 was not provided on the window glass 10 for comparison.

[0071] As an example, when comparing at a CDF level of 0.5, it was confirmed that the strength of the radio wave increases by about 5 dB when the propagation control layer 120 is provided compared to when there is no propagation control layer 120. When the CDF is about 0.1 or more, it was confirmed that the strength of the radio wave increases when there is the propagation control layer 120 compared to when there is no propagation control layer 120.

[0072] From the results of this experiment, it was confirmed that the propagation control layer 120 provided on the window glass 10 can refract radio waves downward.

[0073] Although the above description has been given of an embodiment in which the propagation control layer 120 is made of a metal layer, the base 110 and the propagation control layer 120 may be integrated into a Fresnel lens.

[0074] <Effects> The radio wave propagation control member 100 includes a base 110 and a propagation control layer 120 provided on the base 110. The propagation control layer 120 has a plurality of rectangular regions 121 in a planar view. Each rectangular region 121 has a band-shaped pattern formed by the propagation control layer 120. The rectangular regions 121 are configured to reduce the wavelength in free space of the radio waves arriving at the propagation control layer 120 to λ ０ Then, the length of the short side is 2λ ０ The band-shaped pattern of each rectangular area 121 refracts radio waves in a predetermined direction, and the refraction directions of the radio waves due to the multiple band-shaped patterns are different from each other. In this way, the refraction directions of the radio waves due to the multiple band-shaped patterns are different from each other, making it possible to widen the beam width two-dimensionally. The length of the short side of the rectangular area 121 is 1.5λ. ０ More preferably, λ is equal to or less than λ ０ More preferably, it is 0.5λ or less. ０ Even more preferably, it is 0.1λ or less. ０ It is even more preferred that:

[0075] Therefore, it is possible to provide the radio wave propagation controlling member 100 that can widen the beam width two-dimensionally. As an example, it is preferable that almost no null points can be confirmed in an area where the radio wave strength is high (approximately 20 dBi or more).

[0076] The rectangular regions 121 are arranged in the X direction (first axis direction) and the Y direction (second axis direction) in a plan view of the propagation control layer 120, and the length of the long side of the rectangular regions 121 is 2λ ０ Therefore, the plane size of the rectangular area 121 can be reduced, null points are less likely to occur, and a stable communication area can be generated in a predetermined direction.

[0077] Furthermore, the strip patterns of adjacent rectangular areas 121 may be connected to each other, which makes it possible to generate a wider range of stable communication areas in a predetermined direction with fewer null points.

[0078] Furthermore, the angle formed by the propagation directions of radio waves passing through adjacent rectangular areas 121 may be 2 degrees or less. This makes it difficult for null points to occur, and a stable communication area can be generated in a predetermined direction.

[0079] Furthermore, the strip patterns of adjacent rectangular areas 121 may be arranged in a curved line, which makes it possible to generate a wider range of stable communication areas in a predetermined direction with fewer null points.

[0080] The belt-like pattern may also be made of a metal mesh, which makes it possible to realize a colorless and transparent radio wave propagation controlling member 100 that is difficult to see with the naked eye using a transparent belt-like pattern.

[0081] Furthermore, the propagation control layer 120 may be a transparent conductive layer or a Low-E film, which allows for the realization of a colorless and transparent radio wave propagation control member 100 that is difficult to see with a transparent stripe pattern.

[0082] The band-shaped pattern may form a metasurface in which a plurality of unit pattern conductors are arranged. Therefore, by utilizing the band-shaped pattern formed by the metasurface, it is possible to provide the radio wave propagation controlling member 100 that can more freely widen the beam width in two dimensions.

[0083] Furthermore, base 110 may be a glass plate. This allows propagation control layer 120 to be easily formed, and makes it possible to provide radio wave propagation controlling member 100 that can widen the beam width two-dimensionally. Furthermore, if the glass plate is transparent, radio wave propagation controlling member 100 that is difficult to see and is colorless and transparent can be realized.

[0084] Furthermore, base 110 may be a resin film. This allows propagation control layer 120 to be easily formed, and radio wave propagation control member 100 that can expand the beam width two-dimensionally can be provided. Furthermore, if the resin film is transparent, radio wave propagation control member 100 that is difficult to see and colorless and transparent can be realized.

[0085] Furthermore, base 110 may be a resin film, and radio wave propagation control member 100 may be installed on window glass 10. Therefore, propagation control layer 120 can be easily installed on window glass 10, and radio wave propagation control member 100 can be provided that can expand the beam width two-dimensionally through window glass 10.

[0086] The radio waves may be radio waves in the Sub-6 band or millimeter wave band. It is possible to provide a radio wave propagation controlling member 100 that is compatible with communications in the Sub-6 band or millimeter wave band and is capable of widening the beam width two-dimensionally.

[0087] Moreover, radio wave propagation controlling member 100 includes base 110 and propagation control layer 120 provided on base 110, propagation control layer 120 having a plurality of rectangular regions 121 in plan view, each rectangular region 121 having a metal pattern configured by propagation control layer 120, and rectangular region 121 defining a wavelength in free space of radio waves arriving at propagation control layer 120 as λ ０ Then, the length of the short side is 2λ ０ The radio waves refracted by the metal patterns of the rectangular regions 121 may be configured to propagate in a plurality of refraction directions.

[0088] As the size of each rectangular region 121 is reduced, each rectangular region 121 may include one conductor 120A. In such a case, it is sufficient that a plurality of rectangular regions 121, each including one conductor 120A, are arranged, and radio waves refracted by the plurality of conductors 120A propagate in a plurality of refraction directions, as shown in, for example, Figures 2A to 2C.

[0089] Therefore, it is possible to provide a radio wave propagation controlling member 100 that can widen the beam width two-dimensionally.

[0090] The antenna system 200 includes a base station antenna 50 installed indoors and the radio wave propagation control member 100 installed on the window glass 10. This allows the beam width of the radio waves to be widened two-dimensionally.

[0091] Therefore, it is possible to provide an antenna system 200 that can widen the beam width two-dimensionally.

[0092] Furthermore, in antenna system 200, the difference in the incident direction of radio waves incident from base station antenna 50 on adjacent rectangular areas 121 may be 2 degrees or less. When the difference in the incident direction is 2 degrees or less, the difference in the emission direction of radio waves that have passed through propagation control layer 120 also becomes small, making it difficult for null points to occur and enabling a stable communication area to be generated in a specified direction.

[0093] The above describes exemplary radio wave propagation control members and antenna systems according to the present disclosure. However, the present disclosure is not limited to the specifically disclosed embodiments, and various modifications and changes are possible without departing from the scope of the claims.

[0094] This international application claims priority based on Japanese Patent Application No. 2023-010464, filed on January 26, 2023, the entire contents of which are incorporated herein by reference.

[0095] REFERENCE SIGNS LIST 10 Window glass BS Base station 50 Base station antenna 100 Radio wave propagation control member 110 Base body 120 Propagation control layer (an example of a metal layer) 120A Conductor (an example of a unit pattern conductor) 120U Unit cell 121 Rectangular area 200 Antenna system

Claims

1. a substrate; a metal layer provided on the substrate; Including, the metal layer has a plurality of rectangular regions in a plan view, each rectangular region having a strip-shaped pattern formed by the metal layer; The rectangular area is defined by the wavelength in free space of the radio waves arriving at the metal layer, λ ０ Then, the length of the short side is 2λ ０ is as follows: The strip-shaped pattern of each rectangular area refracts the radio wave in a predetermined direction, The radio wave propagation control member, wherein the directions of refraction of the radio waves by the strip-shaped patterns of the plurality of rectangular regions are different from each other.

2. the plurality of rectangular regions are arranged in a first axis direction and a second axis direction in a plan view of the metal layer, The length of the long side of the rectangular area is 2λ ０ 2. The radio wave propagation control member according to claim 1, wherein:

3. The radio wave propagation control member according to claim 1 or 2, wherein the strip patterns of the adjacent rectangular regions are connected to each other.

4. 3. The radio wave propagation control member according to claim 1, wherein the angle formed between the propagation directions of radio waves passing through adjacent rectangular regions is 2 degrees or less.

5. The radio wave propagation control member according to claim 1 or 2, wherein the strip patterns of the adjacent rectangular regions are arranged in a curved line.

6. 3. The radio wave propagation control member according to claim 1, wherein the band-shaped pattern is made of a metal mesh.

7. 3. The radio wave propagation control member according to claim 1, wherein the metal layer is a transparent conductive layer or a Low-E film.

8. The radio wave propagation control member according to claim 1 or 2, wherein the strip-shaped pattern forms a metasurface in which a plurality of unit pattern conductors are arranged.

9. 3. The radio wave propagation control member according to claim 1, wherein the substrate is a glass plate.

10. 3. The radio wave propagation control member according to claim 1, wherein the substrate is a resin film.

11. the substrate is a resin film, The radio wave propagation control member according to claim 1 or 2, wherein the radio wave propagation control member is installed on a window glass.

12. 3. The radio wave propagation control member according to claim 1, wherein the radio waves are radio waves in the Sub-6 band or millimeter wave band.

13. a substrate; a metal layer provided on the substrate; Including, the metal layer has a plurality of rectangular regions in a plan view, each rectangular region having a metal pattern formed by the metal layer; The rectangular area is defined by the wavelength in free space of the radio waves arriving at the metal layer, λ ０ Then, the length of the short side is 2λ ０ is as follows: The radio wave propagation control member, wherein the radio waves refracted by the metal pattern in the plurality of rectangular regions propagate in a plurality of refraction directions.

14. a base station antenna installed indoors; The radio wave propagation control member according to claim 12 provided on a window glass; an antenna system including:

15. 15. The antenna system according to claim 14, wherein a difference in the direction of incidence of radio waves incident on adjacent rectangular areas from the base station antenna is 2 degrees or less.