Method for constructing wireless communication system, and metasurface

Abstract

This method for constructing a wireless communication system comprises: a first step for specifying, respectively as a first direction and a second direction, a direction of a first base station and a direction of a second base station as viewed from a planned installation position of a metasurface that guides a wireless signal from the first base station to the second base station; a second step for selecting, from a plurality of metasurfaces prepared in advance, a metasurface having characteristics that make it possible to guide the wireless signal from the first direction in the second direction, or for or newly creating said metasurface; and a third step for installing the metasurface selected or created in the second step at the planned installation position.

Description

Method for constructing a wireless communication system and metasurface

[0001] The present invention relates to a method for constructing a wireless communication system and a metasurface.

[0002] A wireless communication system including a first base station, a second base station, and a metasurface that guides a wireless signal from the first base station to the second base station is known (Non-Patent Document 1). In constructing such a wireless communication system, the first base station is fixed and the metasurface is installed. Then, a receiver that receives the wireless signal is moved within an area where the second base station can be installed to search for a position where the reception intensity of the wireless signal is strong. As a result of the search, if there is a position where the reception intensity is strong, the second base station is installed at that position.

[0003] Adam Pander, et al., “Multilayer-laminated optically transparent 300-GHz-band transmissive beamforming metasurface for wireless communication”, Optics Express, Vol. 32, Issue 14, pp. 24772-24786, (2024).

[0004] In constructing the above wireless communication system, if a position where the reception intensity of the wireless signal is strong is not found within the area where the second base station can be installed, the metasurface is replaced and the search for a position where the reception intensity is strong by the receiver is performed again. Therefore, in constructing a conventional wireless communication system, it is laborious. In addition, in a conventional metasurface, since the refraction direction (emission direction of the wireless signal) of the wireless signal is realized by a single metasurface, it may be laborious to design and / or fabricate the metasurface.

[0005] An object of the present invention is to reduce the labor of constructing a wireless communication system or the labor of designing and / or fabricating a metasurface.

[0006] The method for constructing a wireless communication system according to the present invention comprises: a first step of identifying the direction of the first base station and the direction of the second base station as the first direction and the second direction, respectively, as viewed from the planned installation location of a metasurface that guides a wireless signal from the first base station to the second base station; a second step of selecting a metasurface having the characteristic of being able to guide the wireless signal arriving from the first direction to the second direction from a plurality of pre-prepared metasurfaces or creating a new one; and a third step of installing the metasurface selected or created in the second step at the planned installation location.

[0007] The above configuration reduces the effort required to build a wireless communication system.

[0008] The metasurface according to the present invention comprises a first phase gradient metasurface having a phase gradient along a first direction in a plan view, and a second phase gradient metasurface superimposed on the first phase gradient metasurface, having a phase gradient along a second direction different from the first direction in a plan view.

[0009] According to the above configuration, the effort required for designing and / or fabricating metasurfaces is reduced.

[0010] Figure 1 is a diagram showing the configuration of a wireless communication system constructed according to an embodiment of the present invention. Figure 2 is a flowchart of a method for constructing a wireless communication system according to an embodiment of the present invention. Figure 3 is a perspective view of a direction detector used in the construction method of Figure 2. Figure 4 is a perspective view of a direction detector used in the construction method of Figure 2. Figure 5 is a perspective view showing the direction detectors of Figures 3 and 4 placed at the planned installation location of the metasurface. Figure 6 is a diagram illustrating a method for determining the directions (elevation angles) of existing and new base stations as seen from the planned installation location of the metasurface. Figure 7 is a diagram illustrating a method for determining the directions (azimuth angles) of existing and new base stations as seen from the planned installation location of the metasurface. Figure 8 is a schematic plan view of a phase gradient metasurface. Figure 9 is a schematic diagram showing how a wireless signal passes through the metasurface of Figure 8. Figure 10 is a schematic diagram showing two phase gradient metasurfaces constituting a metasurface to be placed at the planned installation location. Figure 11 is a schematic plan view of a metasurface according to a modified example. Figure 12 is a schematic diagram showing an obstacle between the planned installation location and an existing base station. Figure 13 is a schematic diagram showing how a portion of the radio signal from the existing base station is reflected by the structure and interferes with the radio signal that reaches the planned installation location of the metasurface directly from the existing base station. Figure 14 is a perspective view of a modified direction detector.

[0011] (Embodiment) This embodiment will be described below. In the following description, the upward direction (towards the ceiling) will be referred to as the Y direction, and the horizontal direction as the XZ direction. The XYZ directions are orthogonal to each other.

[0012] In this embodiment, a wireless communication system 10 is constructed as shown in Figure 1. The wireless communication system 10 comprises a base station 11, a base station 12, and a metasurface 13. Base stations 11 and 12 are configured to communicate with each other. That is, base stations 11 and 12 are configured so that one transmits a radio signal to the other. The metasurface 13 is configured to guide the radio signal from one of the base stations 11 and 12 to the other. In the example in Figure 1, a radio signal SG1 is transmitted from base station 11. The metasurface 13 changes the direction of travel of the radio signal SG1 arriving from base station 11. This change guides the radio signal SG1 to base station 12.

[0013] The wireless signal SG1 is an electromagnetic wave, such as a radio wave, that transmits the information (e.g., packets) to be sent and received. To accommodate the increased capacity of wireless communication, examples of electromagnetic waves include millimeter waves (e.g., 28 GHz) or high-frequency electromagnetic waves exceeding 100 GHz.

[0014] Base stations 11 and 12 include not only general base stations but also relay devices that relay radio signals such as the radio signal SG1. Examples of relay devices include Wi-Fi relay devices that receive, amplify, and transmit Wi-Fi radio waves.

[0015] The installation locations for base stations 11 and 12 and the metasurface 13 are arbitrary. Here, base station 11 is installed on any structure outdoors, and base station 12 is installed on the ceiling 93 of a building. The metasurface 13 is installed by attaching it to a window 92 on the wall 91 of a building, for example. The metasurface 13 may be configured as the window itself, for example. Note that in Figure 1, only a portion of the wall and only a portion of the ceiling are depicted as wall 91 and ceiling 93, respectively.

[0016] In this embodiment, the wireless communication system 10 is constructed using the construction method shown in Figure 2. Here, the base station 11 is already in place, and the base station 12 and metasurface 13 are newly installed. It can also be considered that the wireless communication system constructed here consists only of the newly installed base station 12 and metasurface 13. As will be described later, if only the metasurface 13 is newly installed, the constructed wireless communication system may consist only of the metasurface 13.

[0017] In the construction method shown in Figure 2, first, the builder of the wireless communication system 10 determines the planned installation location of the metasurface 13 and the installable area of ​​the base station 12 (step S11). For example, the builder checks the site conditions where the wireless communication system 10 will be introduced and determines the specific planned installation locations and installable areas of the base station 12 and the metasurface 13. Here, it is assumed that the planned installation location of the metasurface 13 is determined to be the window 92, and the installable area of ​​the base station 12 is determined to be the area 93A of the ceiling 93.

[0018] Subsequently, the builder identifies the planned installation location of the metasurface 13, i.e., the directions of base stations 11 and 12 as seen from the window 92 (step S12). The direction of base station 11 is the direction to the installation location of base station 11, and the direction of base station 12 is the direction to the area where base station 12 can be installed. A direction detector 20, as shown in Figures 3 and 4, is used for this identification.

[0019] As shown in Figures 3 and 4, the direction detector 20 includes a direction indicator 21, support members 22A and 22B, protractors 23A and 23B, indicator members 24A and 24B, guide parts 25A and 25B, retaining member 26, and support member 27. Note that the front-to-back, left-to-right, and up-and-down directions shown in Figures 3 and 4 are for convenience only and do not indicate the mounting direction of the direction detector 20.

[0020] The direction indicator 21 emits a directional visible light L (for example, laser light) in a straight line from its tip. The direction indicator 21 indicates a direction using this visible light L. An example of a direction indicator 21 is a laser pointer. The direction detector 20 is configured to detect the direction the direction indicator 21 is pointing, in other words, the direction of the visible light irradiation. This direction is represented by the elevation angle, which is the rotation angle around the axis C1 extending in the left-right direction, and the azimuth angle, which is the rotation angle around the axis C2 extending in the up-down direction.

[0021] The turn signal 21 is rotatably supported by support members 22A and 22B. Support member 22A supports one end of the turn signal 21 so that the turn signal 21 rotates around axis C1 as the axis of rotation. Support member 22A has, for example, a hinge mechanism as a mechanism for rotating the turn signal 21. One end of support member 22B is rotatably connected to the center of the turn signal 21. The other end of support member 22B is rotatably connected to indicator member 24A. Support member 22B extends and retracts while rotating relative to the turn signal 21 and indicator member 24A, depending on the rotation angle, or elevation angle, of the rotation of the turn signal 21 around axis C1. Support member 22B is supported at two points by support members 22A and 22B.

[0022] The protractor 23A extends in the forward, backward, left, and right directions and is used to measure the azimuth angle of the direction indicator 21. The protractor 23A has multiple scales 23AA formed on it by printing or other means, for example, indicating azimuth angles within a range of ±90 degrees with the forward direction being 0 degrees. In the drawing, each scale 23AAA is arranged at 45-degree intervals, but the actual scales 23AA are finely marked to allow for the measurement of detailed azimuth angles (the same applies to the scales 23BA described later).

[0023] The scale 23AA of the protractor 23A is indicated by the tapered tip of the indicator member 24A. The indicator member 24A is fixed to the protractor 23A so as to be rotatable around axis C2. Axis C2 passes through the left-right center of the chord portion (straight portion at the rear end) of the semicircular protractor 23A and extends in the vertical direction. For example, a cylindrical projection is formed at the left-right center of the chord portion of the protractor 23A with axis C2 as its central axis, while a circular through-hole is provided at the rear end of the indicator member 24A into which the cylindrical projection is inserted. Due to the engagement between the inner surface of the through-hole and the outer surface of the projection, the indicator member 24A rotates on the protractor 23A with the projection as the center of rotation, or in other words, with axis C2 as the axis of rotation.

[0024] A support member 22A, which supports the turn signal 21, is fixed to the rear end of the indicator member 24A in a way that prevents rotation. As a result, the turn signal 21 and the indicator member 24A rotate together around axis C2. Due to this integrated rotation, the azimuth angle of the turn signal 21 is measured by the position indicated by the tip of the indicator member 24A on the scale 23AA or between adjacent scales 23AA.

[0025] The protractor 23A has an arc-shaped slit 23AB centered on a point on axis C2. A cylindrical guide portion 25A, which protrudes from the lower surface of the indicator member 24A, is inserted into the slit 23AB. The rotation of the indicator member 24A around axis C2 is guided by this guide portion 25A and the slit 23AB. In addition, a plate-shaped retaining element 26, which is wider than the slit 23AB, is fixed to the lower end of the guide portion 25A. This retaining element 26 prevents the guide portion 25A from coming out of the slit 23AB, that is, prevents the indicator member 24A from falling out of the protractor 23A.

[0026] Multiple plate-shaped support members 27 are fixed to the side of the indicator member 24A. The support members 27 support the protractor 23B. The protractor 23B rotates together with the indicator member 24A (and the direction indicator 21). The protractor 23B extends in the vertical and horizontal directions and is used to measure the elevation angle of the direction indicator 21. The protractor 23B is provided with multiple scales 23BA, for example, by printing, which indicate elevation angles with the forward direction being 0 degrees and the upward direction being 90 degrees.

[0027] The protractor 23B has an arc-shaped slit 23BB formed in it, centered on a point on axis C1. A cylindrical guide portion 25B, which protrudes from the side of the turn signal 21, is inserted into the slit 23BB. As described above, the turn signal 21 can rotate around axis C1 as its axis of rotation. The guide portion 25B and the slit 23BB guide the rotation of the turn signal 21 around axis C1.

[0028] An indicator member 24B is fixed to the end of the guide section 25B opposite to the direction indicator 21. The direction indicator 21 and the indicator member 24B are positioned with a protractor 23B in between. The direction indicator 21 and the indicator member 24B rotate together around axis C1. The tapered tip of the indicator member 24B points to the scale 23BA of the protractor 23B or the area between them. Due to the integrated rotation of the direction indicator 21 and the indicator member 24B, the elevation angle of the direction indicator 21 is measured by the position indicated by the tip of the indicator member 24B at the scale 23BA or between adjacent scales 23BA.

[0029] In step S12 of Figure 2, the builder uses the direction detector 20 to determine the planned installation location of the metasurface 13, that is, the directions of base stations 11 and 12 as seen from the window 92. Specifically, when determining the direction of base station 11, the builder places the direction detector 20 in the center of the base station 11 side of the window 92, and when determining the direction of base station 12, the direction detector 20 is placed in the center of the base station 12 side of the window 92. The latter arrangement is shown in Figure 5. In Figure 5, the direction detector 20 is positioned such that the left, up, and forward directions in Figures 3 and 4 coincide with the +X, +Y, and +Z directions in Figure 1, respectively. Furthermore, the direction detector 20 is positioned such that the origin where its axis C1 and axis C2 intersect coincides with the center of the window 92's surface. When determining the direction of the base station 11, the direction detector 20 is positioned such that the left, up, and forward directions in Figures 3 and 4 coincide with the -X, +Y, and -Z directions in Figure 1, respectively.

[0030] When determining the direction of the base station 11, the builder operates a direction detector 20, which is fixed in the center of the base station 11 side of the window 92, to change the orientation of the direction indicator 21 and shine visible light L (for example, the laser beam from a laser pointer) onto the base station 11. The irradiation of this visible light L is schematically shown in Figures 6 and 7. In Figures 6 and 7, only the direction indicator 21 of the direction detector 20 is shown as a dotted-dotted block. The builder reads the elevation angle and azimuth angle, which are the orientation of the direction indicator 21 when the visible light L hits the base station 11, using protractors 23A and 23B and indicator members 24A and 24B. These elevation angles and azimuth angles become the elevation angle φ1 and azimuth angle θ1, which represent the direction of the base station 11 as seen from the window 92, i.e., the planned installation position of the metasurface 13. The azimuth angle θ1 is the direction along the second virtual plane (the XZ plane and the plane in the front-back, left-right, and right directions) that is perpendicular to the metasurface 13 installed at the planned installation location. The first and second virtual planes are perpendicular in this case.

[0031] Similarly, the builder operates a direction detector 20 fixed in the center of the base station 12-side face of window 92 to determine the direction of the base station 12. As shown in Figures 6 and 7, the direction of the base station 12 determined in this case is the direction of the area where the base station 12 can be installed, and therefore has a certain angular range. The builder reads the elevation angle and azimuth angle when visible light L is irradiated onto multiple locations on the outer edge of the area where the base station 12 can be installed, using protractors 23A and 23B and indicator members 24A and 24B. The read elevation angle and azimuth angle become the elevation angle φ2 and φ3 (Figure 6) and azimuth angle θ2 and θ3 (Figure 7), respectively, which represent the direction of the base station 12. The direction of the base station 12 is determined as the ranges of elevation angle φ2 to φ3 and azimuth angle θ2 to θ3. Elevation angles φ2 and φ3 are directions along the first virtual plane (YZ plane and plane in the up, down, front, and back directions). The azimuth angles θ2 and θ3 are directions along the second virtual plane (the XZ plane and the plane in the front, back, left, and right directions). If the area where the base station 12 can be installed is rectangular, the builder may specify the direction of the base station 12 as the range from the minimum elevation angle to the maximum elevation angle and the range from the minimum azimuth angle to the maximum azimuth angle, among the four elevation angles and azimuth angles obtained by irradiating each of the four corners of the area where the base station 12 can be installed.

[0032] After step S12, the builder selects from a plurality of pre-prepared metasurfaces or creates a new metasurface 13 to be actually installed, which has the characteristic of being able to guide the radio signal SG1 arriving from the direction of the base station 11 (existing) identified in step S12 to the direction of the base station 12 (new) identified in step S12 (in this case, the area in which the base station 12 can be installed) when installed at the planned installation location, i.e., window 92 (step S13).

[0033] Here, we will describe the details of the metasurface that can be selected or fabricated as metasurface 13. As will be described later, the metasurface that can be selected or fabricated as metasurface 13 consists of a combination of two metasurfaces. Hereafter, one metasurface will be referred to as metasurface 100, and the details of this metasurface 100 will be described. As shown in Figure 8, the metasurface 100 has a finite number of regions A to H arranged vertically and arranged horizontally at a finite number of periodic intervals. A unit cell UC, such as a ring resonator, of the same structure is formed in each region A. In Figure 8, the unit cell UC is schematically depicted by a dotted circle in only some of the regions A. This unit cell is also called unit cell A. The same applies to regions B to H. The shapes of the unit cells A to H (unit cells B to H are not shown) arranged in regions A to H are all different. Each of the unit cells A to H shifts the phase of the incoming radio signal SG1 by a shift amount corresponding to its shape. Here, the metasurface 100 is of the transmissive type.

[0034] In the metasurface 100, the difference in the shift amounts of adjacent unit cells in the horizontal direction is set to be the same. Specifically, the difference in the shift amounts between adjacent unit cells A and B, phase_B - phase_A, between adjacent unit cells B and C, phase_C - phase_B, ..., and between adjacent unit cells A and H, phase_H - phase_A are all the same. For example, each difference phase_diff can be set to -π / 4. In other words, when the shift amount phase_A of unit cell A is used as the reference, the relative shift amounts of each unit cell are: B: (-π / 4) × 1, C: (-π / 4) × 2, D: (-π / 4) × 3, E: (-π / 4) × 4, F: (-π / 4) × 5, G: (-π / 4) × 6, H: (-π / 4) × 7. The number of different types of unit cells that can be arranged horizontally varies depending on each difference phase_diff. When each difference phase_diff = -π / 6, there are 12 different types of unit cells.

[0035] A metasurface 100 with the same phase_diff for each unit cell is called a phase gradient metasurface. The relationship between the incident angle θin and exit angle θout (see Figure 9) of the radio signal SG1 arriving at this metasurface 100 as a phase gradient metasurface, and the phase_diff (phase_B - phase_A, etc.) difference of the shift amounts of adjacent unit cells, is given by, for example, the following equation (1). Here, for the sake of explanation, it is assumed that the source of the radio signal SG1 (base station 11, etc.) is far from the metasurface 100 and that the radio signal SG1 is a plane wave. d is the distance between adjacent unit cells in the horizontal direction in Figure 8, and λ is the wavelength of the radio signal SG1.

[0036] The metasurface 100 is a phase gradient metasurface in which unit cells of the same shape are arranged vertically and unit cells of different shapes are arranged horizontally. Therefore, it has a phase gradient in which the amount of phase shift of the transmitted wireless signal SG1 changes along the horizontal direction. When this metasurface 100 is viewed in plan as shown in Figure 8, the direction of propagation of the wireless signal SG1 incident on the metasurface 100 from the back does not change vertically, but only horizontally. In other words, the refraction direction of the wireless signal SG1 is only horizontal.

[0037] In equation (1) above, phase_diff does not change because the metasurface 100 is a static metasurface with fixed transmission characteristics. Therefore, in this case, when the incident angle θin of the wireless signal SG1 changes, the exit angle θout changes. For example, when d = λ / 4 and phase_diff = -π / 4, if θin = 0°, then θout = 30°, but if θin = 15°, then θout = 49°.

[0038] Table 1 below shows the relationship between the incident angle θin and the exit angle θout in a metasurface 100 having d = λ / 4 and phase_diff = -π / 4.

[0039] Table 2 below shows the relationship between the incident angle θin and the exit angle θout in the metasurface 100 having d = λ / 4 and phase_diff = -π / 6.

[0040] As can be seen from Tables 1 and 2, in the same metasurface 100, there is a one-to-one relationship between the incident angle θin and the exit angle θout. On the other hand, the relationship between the incident angle θin and the exit angle θout will be different between metasurfaces 100 with different d and / or phase_diff. Therefore, in this embodiment, multiple types of metasurfaces 100 are prepared, each with different characteristics for changing the direction of propagation of the wireless signal SG1 by varying d and / or phase_diff, that is, by varying the spacing and / or shape of the unit cells.

[0041] In step S13 above, the builder derives the emission angle θout for each of the multiple types of metasurfaces 100 prepared as described above, when the incidence angle θin is the azimuth angle θ1 of the base station 11 identified in step S12. This derivation may be performed using equation (1) above, or a pre-prepared table showing the relationship between the incidence angle θin and the emission angle θout may be referred to. Equation (1) and the table above represent the characteristics of the metasurface 100. In other words, the emission angle θout is derived based on the characteristics of the metasurface 100. The characteristics used to derive the emission angle θout may be pre-prepared information other than those in (1) and the table above. Subsequently, the builder selects the metasurface 100 in which the derived emission angle θout falls within the range of azimuth angles θ2 to θ3 of the base station 12 identified in step S12 as the azimuth angle metasurface 100A (Figure 10). Similarly, the builder derives the emission angle θout for each of the multiple metasurfaces 100 when the elevation angle φ1 of the base station 11 identified in step S12 is taken as the incidence angle θin. Then, the builder selects the metasurface 100 whose derived emission angle θout falls within the range of elevation angles φ2 to φ3 of the base station 12 identified in step S12 as the elevation angle metasurface 100B (Figure 10).

[0042] As shown in FIG. 10, the selected metasurfaces 100A and 100B are overlapped such that their longitudinal directions are orthogonal to each other, thereby obtaining a metasurface having the property of being able to guide the radio signal SG1 from the direction of the base station 11 to the direction of the base station 12 (here, the installable area of the base station 12). The obtained metasurface is installed as the metasurface 13 of the wireless communication system 10 as described later (see FIG. 10). The metasurface 13 is installed in the window 92 such that the longitudinal direction of the metasurface 100 for azimuth angle coincides with the Y direction, and the lateral direction of the metasurface 100 for elevation angle coincides with the Y direction. Thereby, the metasurface 13 installed in the window 92 can emit, that is, guide, the radio signal SG1 from the base station 11 toward the direction (installable area) of the base station 12. By obtaining the metasurface 13 by overlapping the metasurfaces 100A and 100B, for example, if m metasurfaces are prepared, then from the m×m combinations of two metasurfaces, that is, the m×m candidates of the metasurface 13, the metasurface 13 having the above property is selected.

[0043] Here, the metasurface that is a selection candidate for the azimuth-angle metasurface 100A and the metasurface that is a selection candidate for the elevation-angle metasurface 100B are made the common metasurface 100, and one is rotated 90° with respect to the other and used, but the two selection candidates may be prepared separately. For example, when the unit cell of the metasurface 100 is polarization-independent, it is preferable to make the selection candidates for the metasurfaces 100A and 100B common. For example, when the unit cell of the metasurface 100 has polarization dependence on the radio signal SG1, it is preferable to prepare the selection candidates for the metasurfaces 100A and 100B separately. Making the selection candidates common can reduce the types of metasurfaces to be prepared.

[0044] In step S12, in addition to the above selection (for example, if there are no metasurfaces that satisfy the current conditions among the selection candidates), or instead of the above selection, a new metasurface may be created with the respective directions of base stations 11 and 12 identified in step S11 as the incident angle and reflection angle. Specifically, a metasurface 100A is designed and manufactured with the azimuth angle θ1 of base station 11 as the incident angle θin and an angle within the range of azimuth angles θ2 to θ3 of base station 12 as the outgoing angle θout. A metasurface 100B is designed and manufactured with the elevation angle φ1 of base station 11 as the incident angle θin and an angle within the range of elevation angles φ2 to φ3 of base station 12 as the outgoing angle θout. By overlapping the manufactured metasurfaces 100A and 100B, a metasurface 13 is created. The outgoing angles θout of metasurfaces 100A and 100B are determined during the design phase and are determined by the characteristics of the designed metasurfaces 100A and 100B.

[0045] After step S13 in Figure 2, the builder determines the direction of emission of the radio signal SG1 from the base station 11 to the selected or fabricated metasurface 13 when it is installed in the window 92, which is the planned installation location (step S14). This emission direction is the direction where the emission angle θout of the metasurface 100A derived or designed above is the azimuth angle, and the emission angle θout of the metasurface 100B derived or designed above is the elevation angle. In other words, the emission direction is determined from the characteristics of the metasurface 13, rather than being actually measured. The determination of the emission direction of the radio signal SG1 from the metasurface 13 is performed, for example, before the metasurface 13 is actually installed in the planned installation location.

[0046] After that, the constructor again places the direction detector 20 at the center of the surface of the window 92 on the base station 12 side (step S15). Then, the constructor adjusts the orientation of the direction indicator 21 so that the azimuth angle and elevation angle that can be read by the graduated scales 23A and 23B and the indicating members 24A and 24B match the emission direction specified in step S14 (step S16). In step S15, the direction detector 20 after adjusting the orientation of the direction indicator 21 may be placed on the window 92. That is, the order of steps S15 and S16 is arbitrary. The direction indicator 21 after orientation adjustment emits visible light L. This visible light L hits a part of the installable area 93A of the ceiling 93. The position where this visible light L hits becomes the center position of the guiding destination of the radio signal SG1 by the metasurface 13 installed on the window 92. Therefore, the constructor installs the base station 12 here (step S17). Also, the constructor installs the metasurface 13 on the window 92 which is also the planned installation position (step S18). Step S17 may be performed simultaneously with or before step S16.

[0047] For example, when θ1 = 30°, θ2 = 45°, θ3 = 65°, φ1 = 15°, φ2 = 40°, φ3 = 60°, for the azimuth angle, the metasurface 100 with phase_diff = -π / 6 is selected, and for the elevation angle, the metasurface 100 with phase_diff = -π / 4 is selected. Also at this time, the detailed direction of the base station 12 from the metasurface 13 is azimuth angle = 56°, elevation angle = 49°, and the installation location of the base station 12 is determined by the direction indicator 21 set at this angle.

[0048] (Modification 1) The metasurface 13 may be a stack of three or more metasurfaces, or it may be a single metasurface. The angle formed by the directions of the phase gradients of the multiple metasurfaces may be set to an angle other than 90°. An example of a metasurface 13 composed of a single metasurface is shown in Figure 11 as metasurface 100C. Metasurface 100C has a phase gradient of phase_diff = -π / 4 set in an oblique direction. When the metasurface 13 is composed of a single metasurface, the number of types of metasurfaces that need to be prepared in advance increases. For example, when using two metasurfaces, if m types of metasurfaces are prepared as candidate selections for the azimuth angle and n types of metasurfaces are prepared as candidate selections for the elevation angle, then m + n types can be prepared as the emission direction of the wireless signal SG1. When using a single metasurface, m × n types of metasurfaces are required to obtain the same type of emission direction. Therefore, it is preferable for the metasurface 13 to consist of a combination of multiple metasurfaces. Furthermore, as described above, by making the selection candidates common to each of the multiple metasurfaces, the number of types of metasurfaces that need to be prepared can be further reduced.

[0049] (Modification 2) Consider the case where there is an obstacle 201 between the window 92, which is the planned installation location for the metasurface 13, and the base station 11, as shown in Figure 12, and the case where there is significant interference between the radio signal SG1 arriving directly from the base station 11 to the window 92 and the reflected waves of the radio signal SG1 due to the surrounding structures 202, as shown in Figure 13. In the former case, the base station 11 cannot be seen from the window 92. In other words, visible light L does not reach the base station 11. In the latter case, the direction in which the received strength of the radio signal SG1 arriving at the window 92 is strong does not coincide with the direction of the base station 11.

[0050] In such cases, the direction detector 20 is changed to the direction detector 50 shown in Figure 14. The direction detector 50 has the same configuration as the direction detector 20, but instead of a direction indicator 21, it has a directional antenna 51 such as a horn antenna. When the builder determines the direction of the base station 11, the base station 11 emits a radio signal SG1 and changes the orientation of the directional antenna 51. The builder determines the azimuth angle and elevation angle when the received strength of the radio signal SG1 by the directional antenna 51 is strongest as the azimuth angle θ1 and elevation angle φ1.

[0051] The position of the base station 11 can be determined without using the direction detectors 20 and 50. For example, geometric positional information of the base station 11 (e.g., a set that can determine the position in three dimensions, such as latitude, longitude, and altitude) can be obtained, and geometric positional information of the window 92, which is the planned installation location of the metasurface 13, can also be obtained. The direction of the base station 11 can also be calculated from the positional relationships based on this positional information. For example, if the position of the base station 11 as seen from the metasurface 13 is shown in an xyz Cartesian coordinate system from the obtained geometric positional information, the direction can be obtained using a general Cartesian coordinate to spherical coordinate transformation (for example, equations (2) and (3) below).

[0052] Furthermore, if the base station 11 is sufficiently far from the window 92, the radio signal SG1 can be considered as an electromagnetic incoming wave of perfectly parallel light.

[0053] This modified version can also be applied to determining the direction of base station 12. In particular, it can be applied when base station 12 is already in place, as in the modified version described later.

[0054] (Modification 3) Depending on the positional relationship between base stations 11 and 12 and the metasurface 13, it may be possible to reach base station 12 by changing only the elevation angle of the radio signal SG1 from base station 11 without changing the azimuth angle. In such cases, the metasurface 13 may be composed only of the metasurface 100B for the elevation angle. Similarly, it may be possible to reach base station 12 by changing only the azimuth angle of the radio signal SG1 from base station 11 without changing the elevation angle. In such cases, the metasurface 13 may be composed only of the metasurface 100A for the azimuth angle.

[0055] (Modification 4) Direction detectors 20 and 50 may be configured to detect the depression angle in addition to, or instead of, the elevation angle of the direction indicator 21 and the directional antenna 51. Alternatively, the direction indicator 21 and the directional antenna 51 may be equipped with sensors that detect their own tilt, which is the elevation angle and / or depression angle. In this case, the elevation angle and / or depression angle are measured by these sensors. In this case, the protractor 23B and the guide unit 25B are unnecessary.

[0056] (Modification 5) The planned installation location of the metasurface 13 does not have to be a surface perpendicular to the ground, such as the surface of the window 92. Even in such a case, by aligning the left, right, up, down, front, and back directions of the direction detectors 20 and 50 with the XYZ directions, where the surface direction of the metasurface 13 assumed to be actually installed is the XY direction, the directions of the base stations 11 and 12 as seen from the planned installation location of the metasurface 13 can be accurately determined by the direction detectors 20 and 50.

[0057] (Modification 6) Base station 12 may be installed in addition to or instead of base station 11. In this case, the direction of base station 12 is determined by a single elevation angle φ2 and azimuth angle θ2. In this case, a metasurface is selected for the elevation angle, where the exit angle when the incident angle is elevation angle φ1 is approximately the same as the elevation angle φ2, and a metasurface is selected for the azimuth angle, where the exit angle when the incident angle is azimuth angle θ1 is approximately the same as the azimuth angle θ2. Approximately the same includes not only the exit angle being the same as the elevation angle or azimuth angle, but also the exit angle being within a certain range centered on the elevation angle or azimuth angle. In this modification, the processing from step S14 onwards is unnecessary. For example, if θ1 = 30°, θ2 = 45°, φ1 = 15°, and φ2 = 49°, then a metasurface 100 with phase_diff = -π / 6 is selected for the azimuth angle, and a metasurface 100 with phase_diff = -π / 4 is selected for the elevation angle. Only one metasurface may be selected. In addition to or instead of the selection, new metasurfaces may be designed and manufactured.

[0058] (Modification 7) Base stations 11 and 12 may both be newly constructed. In this case, the direction of base station 11 will be the direction of the area where base station 11 is to be installed. Then, a metasurface is selected or created that has a combination of incident and exit angles that fall within the angular range of base station 11 and the angular range of base station 12, respectively. After that, steps S15 to S17 in Figure 2 may be performed for each of base station 11 and base station 12.

[0059] (Modification 8) The metasurface 13 may consist of any metasurface other than the phase gradient metasurface, for example, one or more metasurfaces having any phase distribution or intensity distribution. The metasurface 13 may also be of the reflective type.

[0060] (Modification 9) The distance from the planned installation location of the metasurface 13 to the base stations 11 and 12 is specified in addition to the above directions, and in addition to the function of guiding the radio signal SG1, a metasurface 13 may be selected or manufactured that has the function of a focusing lens with the said distance as its focal length. The distance is measured, for example, by a direction indicator 21 with a distance measuring function (such as a laser pointer with a distance measuring function).

[0061] (Note) Methods and configurations that use all or part of the above embodiments and modifications as examples are described below.

[0062] (Note 1) A method for constructing a wireless communication system, comprising: a first step of identifying the direction of the first base station and the direction of the second base station as the first direction and the second direction, respectively, as viewed from the planned installation location of a metasurface that guides a wireless signal from the first base station to the second base station; a second step of selecting a metasurface having the characteristic of being able to guide the wireless signal from the first direction to the second direction from a plurality of pre-prepared metasurfaces or creating a new one; and a third step of installing the metasurface selected or created in the second step at the planned installation location.

[0063] This method allows for the installation of a metasurface capable of guiding radio signals from the first base station to the second base station, based on the orientation of the two base stations. Therefore, the need to replace the metasurface, which may be required in conventional methods, is eliminated, reducing the effort involved in constructing a wireless communication system.

[0064] (Note 2) A method for constructing a wireless communication system as described in Note 1, further comprising: (1) The first direction is the direction of the location of the existing first base station; (2) The second direction is the direction of the area in which the second base station can be installed; (4) The fourth step of identifying the emission direction of the wireless signal when the first direction of the metasurface selected or manufactured in the second step is the incidence direction of the wireless signal; and (5) The fifth step of emitting visible light having directionality in the emission direction from the planned installation location and installing the second base station in the area in which the visible light hits.

[0065] This method allows for the determination of the installation location of the second base station using visible light, which is a simpler method than the conventional method described above that uses a receiver to locate the second base station. This reduces the effort required to construct a wireless communication system.

[0066] (Note 3) The fifth step is a method for constructing a wireless communication system as described in Note 2, comprising: an arrangement step of arranging a device having a light source that emits visible light and a measuring mechanism capable of measuring the direction of the light source at the planned installation location; an adjustment step of adjusting the direction of the light source so that the direction measured by the measuring mechanism coincides with the emission direction; and an emission step of emitting visible light from the light source of the device installed at the planned installation location in the direction adjusted by the adjustment step, thereby emitting the visible light from the planned installation location in the emission direction.

[0067] An example of the device is a direction detector 20. An example of the light source is a direction indicator 21. An example of the measuring mechanism includes protractors 23A and 23B and indicator members 24A and 24B. The measuring mechanism may include sensors that detect the elevation angle and / or depression angle, which are the inclination angles of the direction indicator 21 and the directional antenna 51. An example of the adjustment step is to adjust the orientation of the light source so that the combination of azimuth angle and elevation angle and / or depression angle that can be measured by the measuring mechanism matches the combination of azimuth angle and elevation angle and / or depression angle that represents the emission direction. The order of the placement step and the adjustment step is arbitrary.

[0068] According to the above method, the installation location of the second base station can be easily indicated using visible light, and the effort required to construct the wireless communication system is reduced.

[0069] (Note 4) The method for constructing a wireless communication system according to any one of Notes 1 to 3, wherein the first direction is the direction of the location of the existing first base station, and in the first step, the direction of emission of directional light emitted from the planned installation location when it strikes the first base station is identified as the first direction.

[0070] The first step may be performed using the apparatus described in Appendix 3. In this case, the direction of the light source measured by the measuring mechanism of this apparatus becomes the direction of light emission.

[0071] According to the above method, the first direction can be easily identified, and the effort required to build a wireless communication system is reduced.

[0072] (Note 5) The method for constructing a wireless communication system according to any one of Notes 1 to 4, wherein the first direction is represented by a first angle and a second angle along a first virtual plane and a second virtual plane, respectively, that are orthogonal to the metasurface when it is installed at the planned installation location, the second direction is represented by a third angle and a fourth angle along the first virtual plane and the second virtual plane, respectively, and the metasurface when it is installed at the planned installation location includes a first phase gradient metasurface having a first phase gradient along the first virtual plane and a second phase gradient metasurface having a second phase gradient along the second virtual plane.

[0073] An example of the first virtual plane is the YZ plane (a vertical plane perpendicular to the horizontal plane) in Figure 1. An example of the first and third angles along the first virtual plane is the elevation angle and / or depression angle. An example of the second virtual plane is the XZ plane (horizontal plane) in Figure 1. An example of the second and fourth angles along the second virtual plane is the azimuth angle. An example of the first phase gradient along the first virtual plane is the phase gradient along the Y direction, more specifically, the phase gradient in which the amount of shift changes along the Y direction. An example of the second phase gradient along the second virtual plane is the phase gradient along the X direction, more specifically, the phase gradient in which the amount of shift changes along the X direction. An example of the first and second phase gradient metasurfaces is the metasurfaces 100A and 100B described above. The first and second virtual planes do not have to be orthogonal.

[0074] According to the above method, the first and second directions are decomposed into two types of angles, and the refraction direction of the wireless signal of the metasurface is also realized by the first phase gradient metasurface and the second phase gradient metasurface, which have the direction of these two types of angles as the refraction direction. This makes it easy to handle the first direction, the second direction, and the refraction direction of the metasurface, reducing the effort required to construct a wireless communication system. Furthermore, by combining the first phase gradient metasurface and the second phase gradient metasurface, many metasurfaces can be realized with a small number of types of first and second phase gradient metasurfaces.

[0075] (Note 6) The method for constructing the wireless communication system described in Note 5, wherein the first virtual plane and the second virtual plane are orthogonal.

[0076] This makes it easier to handle the first direction, the second direction, and the refraction direction of the metasurface compared to the case where the first and second virtual surfaces are not orthogonal, thereby reducing the effort required to build a wireless communication system.

[0077] (Note 7) A method for constructing a wireless communication system according to any one of Notes 1 to 6, wherein in the first step, the distance from the planned installation location to the second base station is further specified, and in the second step, a metasurface having the characteristics that enable the guidance of the wireless signal from the first direction to the second direction and having the distance as the focal length (more specifically, the focal length on the second base station side) is selected or manufactured.

[0078] This method makes it possible to improve the received strength of the radio signal at the second base station.

[0079] In addition, instead of or in addition to Appendix 7, the first step may further specify the distance from the planned installation location to the first base station, and the second step may select or create a metasurface having the characteristics that enable the radio signal arriving from the first direction to be guided in the second direction, and the distance being the focal length on the first base station side.

[0080] (Note 8) A metasurface comprising: a first phase gradient metasurface having a phase gradient along a first direction in a plan view; and a second phase gradient metasurface superimposed on the first phase gradient metasurface, having a phase gradient along a second direction different from the first direction in a plan view.

[0081] With this configuration, the refraction direction (emission direction) of electromagnetic waves such as the above-mentioned wireless signals of the metasurface can be realized by a combination of the first phase gradient metasurface and the second phase gradient metasurface, making the design and / or manufacture of the metasurface easier than that of a single-piece metasurface. This is especially true when the first direction and the second direction are orthogonal. The above plan view refers to the view of the metasurface from its thickness direction (the direction in which the first and second phase gradient metasurfaces are superimposed). The phase gradient along the first direction refers to a mode in which the amount of phase shift of transmitted or reflected electromagnetic waves changes along the first direction, and the phase gradient along the second direction refers to a mode in which the amount of phase shift of transmitted or reflected electromagnetic waves changes along the second direction.

[0082] (Scope of the Invention) The present invention is not limited to the embodiments and modifications described above. For example, the present invention includes various modifications to the embodiments and modifications described above that can be understood by those skilled in the art within the scope of the technical concept of the present invention. The configurations listed in the embodiments and modifications described above can be combined as appropriate to the extent that they do not contradict each other. It is also possible to delete any of the above configurations.

[0083] 10... Wireless communication system, 11, 12... Base station, 13... Metasurface, 20, 21... Direction indicator, 22A, 22B... Support member, 23A, 23B... Protractor, 23AB, 23BB... Slit, 24A, 24B... Indicator member, 25A, 25B... Guide section, 27... Support member, 50... Direction detector, 51... Directional antenna, 91... Wall, 92... Window, 93... Ceiling, 93A... Installable area, 100, 100A-100C... Metasurface, 201... Obstacle, 202... Structure, C1... Axis, C2... Axis, L... Visible light, UC... Unit cell.

Claims

1. A method for constructing a wireless communication system, comprising:

1. A first step of identifying the direction of the first base station and the direction of the second base station as the first direction and the second direction, respectively, as viewed from the planned installation location of a metasurface that guides a wireless signal from the first base station to the second base station; 2. A second step of selecting a metasurface having the characteristic of being able to guide the wireless signal from the first direction to the second direction from a plurality of pre-prepared metasurfaces or creating a new one; and 3. Installing the metasurface selected or created in the second step at the planned installation location.

2. A method for constructing a wireless communication system according to claim 1, further comprising:

2. The first direction is the direction of the location of an existing first base station; the second direction is the direction of an area in which the second base station can be installed; a fourth step of identifying the emission direction of the wireless signal when the first direction of the metasurface selected or manufactured in the second step is the incidence direction of the wireless signal; and a fifth step of emitting visible light having directionality in the emission direction from the planned installation location and installing the second base station in the area in which the visible light hits.

3. The fifth step is a method for constructing a wireless communication system according to claim 2, comprising: a placement step of arranging a device having a light source that emits visible light and a measuring mechanism capable of measuring the direction of the light source at the planned installation location; an adjustment step of adjusting the direction of the light source so that the direction measured by the measuring mechanism coincides with the emission direction; and an emission step of emitting visible light from the light source of the device installed at the planned installation location in the direction adjusted by the adjustment step, thereby emitting the visible light from the planned installation location in the emission direction.

4. The method for constructing a wireless communication system according to claim 1, wherein the first direction is the direction of the location of the existing first base station, and in the first step, the direction of emission of visible light when directional visible light emitted from the planned installation location strikes the first base station is identified as the first direction.

5. The method for constructing a wireless communication system according to claim 1, wherein the first direction is represented by a first angle and a second angle along a first virtual plane and a second virtual plane, respectively, that are orthogonal to the metasurface when installed at the planned installation location, the second direction is represented by a third angle and a fourth angle along the first virtual plane and the second virtual plane, respectively, and the metasurface when installed at the planned installation location includes a first phase gradient metasurface having a first phase gradient along the first virtual plane and a second phase gradient metasurface having a second phase gradient along the second virtual plane.

6. The method for constructing a wireless communication system according to claim 5, wherein the first virtual plane and the second virtual plane are orthogonal.

7. A method for constructing a wireless communication system according to claim 1, wherein the first step further specifies the distance from the planned installation location to the second base station, and the second step selects or creates the metasurface having the characteristics that enable the guidance of the wireless signal from the first direction to the second direction and having the distance as its focal length.

8. A metasurface comprising: a first phase gradient metasurface having a phase gradient along a first direction in a plan view; and a second phase gradient metasurface superimposed on the first phase gradient metasurface, having a phase gradient along a second direction different from the first direction in a plan view.

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