Radio wave transmission system and radio wave transmission method

Abstract

Provided are a radio wave transmission system and a radio wave transmission method wherein the incident direction and reflection direction of a reflection plate can be easily adjusted.　The radio wave transmission system comprises: a reflection plate the reflection direction of which can be moved in a scanning motion; a control unit that controls the reflection direction of the reflection plate; an antenna that is placed in a position fixed relative to the reflection plate and that can receive radio waves reflected by the reflection plate; and a storage unit. The control unit adjusts the reflection direction of the reflection plate so that reception power at the antenna increases. The control unit stores, in the storage unit, an incident phase distribution that is obtained on the basis of: a total phase distribution representative of the distribution of phase change amounts given by the reflection plate to an incident wave; and a first reflection phase distribution determined by the positional relationship between the antenna and the reflection plate. The control unit determines a target total phase distribution that is achieved by the incident phase distribution and a second reflection phase distribution corresponding to the positional relationship between the reflection plate and a target terminal positioned in a predetermined reflection direction relative to the reflection plate.

Description

Radio wave transmission system and radio wave transmission method

[0001] The present disclosure relates to a radio wave transmission system and a radio wave transmission method.

[0002] Conventionally, there has been a reflection direction control system that includes one or more reflectors having a plurality of reflecting elements that are capable of dynamically changing phase characteristics when reflecting radio waves, an arrival direction estimation unit that estimates the arrival direction of radio waves transmitted from a wireless terminal to the reflector, a phase control unit that controls the phase of the radio waves reflected by each of the plurality of reflecting elements so that the reflector reflects the radio waves transmitted from the arrival direction estimated by the arrival direction estimation unit in a predetermined direction, and a switching unit that switches between an antenna mode in which the reflector receives the radio waves whose arrival direction is estimated by the arrival direction estimation unit and a reflection mode in which the reflector reflects the radio waves in accordance with the control of the phase control unit (see, for example, Patent Document 1).

[0003] International Publication No. 2022 / 024233

[0004] However, adjusting the incident direction of radio waves from a wireless terminal (wave source) onto a reflector and the reflection direction of the radio waves reflected from the reflector onto a target in a predetermined direction is a very time-consuming task. In particular, when reflecting highly directional radio waves such as Sub-6 or millimeter wave band radio waves, the tolerance for adjusting the incident direction and reflection direction is small, and if the angle of the incident direction or reflection direction is off by a few degrees, the strength of the radio waves reaching the target will decrease significantly.

[0005] Therefore, an object of the present invention is to provide a radio wave transmission system and a radio wave transmission method that allow the incident direction and reflection direction of a reflector to be easily adjusted.

[0006] A radio wave transmission system according to an embodiment of the present disclosure includes a reflector capable of scanning its reflection direction, a control unit that controls the reflection direction of the reflector, an antenna installed at a fixed position relative to the reflector and capable of receiving radio waves reflected by the reflector, and a memory unit, wherein the control unit adjusts the reflection direction of the reflector so as to increase the received power at the antenna, stores in the memory an incident phase distribution obtained based on a total phase distribution that represents the distribution of phase changes that the reflector imparts to incident waves, obtained in the adjusted state, and a first reflected phase distribution determined by the positional relationship between the antenna and the reflector, and calculates a target total phase distribution realized by the incident phase distribution and a second reflected phase distribution that corresponds to the positional relationship between the reflector and a target terminal located in a predetermined reflection direction relative to the reflector.

[0007] It is possible to provide a radio wave transmission system and a radio wave transmission method that allow the incident direction and reflection direction of a reflector to be easily adjusted.

[0008] 1 is a diagram illustrating the operation of a radio wave transmission system according to an embodiment of the present disclosure; FIG. 1 is a block diagram illustrating an example of the configuration of a radio wave transmission system according to an embodiment; FIG. 2 is a diagram illustrating an example of a state in which the radio wave transmission system according to an embodiment is attached to a wall; FIG. 3 is a diagram illustrating an example of an arrangement of a plurality of cells of a reflector according to an embodiment; FIG. 4 is a diagram illustrating an example of the principle of adjusting a reflection angle in a reflector according to an embodiment; FIG. 5 is a diagram illustrating an example of the principle of adjusting a reflection angle in a reflector according to an embodiment; FIG. 6 is a diagram illustrating an example of the configuration of a cell of a reflector according to an embodiment; FIG. 7 is a diagram illustrating an example of a coupling state of a resonant element in a cell by turning on and off a PIN diode of a resonant element; FIG. 8 is a diagram illustrating an example of a coupling state of a resonant element in a cell by turning on and off a PIN diode of a resonant element; FIG. 9 is a diagram illustrating an example of a coupling state of a resonant element in a cell by turning on and off a PIN diode of a resonant element; FIG. 10 is a diagram illustrating an example of a coupling state of a resonant element in a cell by turning on and off a PIN diode of a resonant element; 1 is a diagram for explaining how to calculate the maximum distance between the reflector 100 and the target terminal; FIG. 2 is a diagram for explaining the Fresnel radius between the wave source and the antenna; FIG. 3 is a diagram for explaining the Fresnel radius between the wave source and the antenna; and FIG. 4 is a flowchart showing an example of processing executed by the control unit 5.

[0009] Hereinafter, embodiments to which the radio wave transmission system and radio wave transmission method 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 one another. 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 may be misaligned to the extent that they do not impair the effects of the embodiments.

[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 reflected by the reflector included in the radio wave transmission 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 1 GHz to 30 GHz including Sub-6. Furthermore, the radio waves reflected by the reflector included in the radio wave transmission system of the embodiment may be LTE (Long Term Evolution), LTE-Advanced (LTE-A), or UMB (Ultra Mobile Broadband). Furthermore, the radio waves reflected by the reflector included in the radio wave transmission system of the embodiment may be IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.20, UWB (Ultra-Wideband), Bluetooth (registered trademark), LPWA (Low Power Wide Area), or the like. As the frequency of the radio waves increases, propagation loss due to reflection and diffraction increases, making blind zones more likely to occur. Therefore, the reflector included in the radio wave transmission system of the embodiment is more suitable for communications using relatively high frequencies.Unless otherwise specified, the following description will be given using millimeter wave band and Sub-6 radio waves as examples.

[0013] <Embodiments> <Radio wave transmission system 10> FIG. 1 is a diagram illustrating the operation of a radio wave transmission system 10 according to an embodiment of the present disclosure.

[0014] The radio wave transmission system 10 according to the present disclosure is disposed, for example, on a wall or window of an outdoor building BD. The radio wave transmission system 10 includes a reflector 100 (see FIG. 2 ), which is a directivity control array called a Reconfigurable Intelligent Surface (RIS) that can adjust the directivity of a beam.

[0015] The type of building BD in which the radio wave transmission system 10 is installed is arbitrary, but may be, for example, a building in an area where high-rise buildings stand side by side. In areas where high-rise buildings stand side by side, dead zones (areas or spaces with poor communication environments, also called "dead zones") where radio waves do not reach properly are likely to occur. The radio wave transmission system 10 of the present disclosure delivers radio waves to dead zones by controlling the direction of the beam of reflected radio waves.

[0016] FIG. 1 schematically illustrates the radiation patterns of radio waves transmitted from a radio base station BS and radio waves R reflected from a radio wave transmission system 10. As shown in FIG. 1, a radio base station BS may be provided for wireless communication. The radio base station BS converts a signal from a network (not shown) such as the Internet into a radio signal and transmits the radio waves R, which are then received by a receiving terminal. The radio base station BS also receives the radio waves R transmitted by the receiving terminal, allowing the receiving terminal to access a network such as the Internet. The radio base station BS may be provided near the radio wave transmission system 10, approximately several tens of centimeters to several meters, or may be provided at a distance of approximately several tens of meters to several kilometers from the radio wave transmission system 10.

[0017] The radio wave transmission system 10 of the present disclosure delivers radio waves to blind areas blocked by buildings BD by changing the beam direction of the incident radio waves R and reflecting the beam in a specific direction or by generating multiple beams. In the following description, the radio waves are assumed to be plane waves unless otherwise specified.

[0018] As shown in FIG. 1 , the use of a radio wave transmission system 10 enables Internet communication by selecting an outdoor receiving terminal U1, U2, or U3. Specifically, for example, radio waves R transmitted from a radio base station BS at a certain time are reflected by the radio wave transmission system 10 and received by the outdoor receiving terminal U1, thereby establishing wireless communication with the receiving terminal U1. Radio waves R transmitted from the radio base station BS at a different time are reflected by the radio wave transmission system 10 and received by the outdoor receiving terminal U2, thereby establishing wireless communication with the receiving terminal U2. The same applies to the receiving terminal U3 as to the receiving terminals U1 and U2. Note that, although the case where the receiving terminals U1, U2, and U3 receive radio waves R will be described here, when the receiving terminals U1, U2, and U3 transmit radio waves R, the radio base station BS receives the radio waves R reflected by the radio wave transmission system 10.

[0019] 1 shows an example in which radio waves coming from a radio base station BS are reflected by a reflector 100 in addition to the radio wave transmission system 10, but radio waves coming from a radio relay station or the like may also be reflected by the reflector 100. Also, in FIG. 1, the receiving terminals U1, U2, and U3 are smartphones carried by users, but they may also be fixed receiving terminals that are fixed to a building or the like and do not move.

[0020] Fig. 2 is a block diagram showing an example of the configuration of the radio wave transmission system 10. Fig. 3 is a diagram showing an example of the state in which the radio wave transmission system 10 is attached to a wall 1. Fig. 2 shows a state in which the reflector 100 reflects radio waves arriving from the radio base station BS directly toward the receiving terminal U1. The receiving terminal U1 has an antenna for communication.

[0021] The radio wave transmission system 10 includes a reflector 100 and a control unit 5. The radio wave transmission method of this embodiment is realized by processing executed by the control unit 5 of the radio wave transmission system 10. The radio wave transmission system 10 includes an antenna used to set a total phase distribution that represents the distribution of multiple phase change amounts that change the phase of radio waves when multiple cells of the reflector 100 reflect the radio waves as incident waves, but the antenna is omitted in Figures 2 and 3. The total phase distribution represents the distribution of multiple phase change amounts that change the phase of radio waves when all multiple cells included in the reflector 100 reflect the radio waves as incident waves.

[0022] As an example, the antenna of the radio wave transmission system 10 is detachable, and is therefore assumed to be detached in Figures 2 and 3. Also, in Figure 2, it is assumed that the total phase distribution of the reflector 100 is appropriately set, so that the reflector 100 reflects radio waves R transmitted from the base station RS as a wave source, and the reflected radio waves R reach the user terminal U1. The configuration of the radio wave transmission system 10, including the antenna, and the process of setting the total phase distribution will be described later.

[0023] The control unit 5 is realized by, for example, an MCU (Micro Controller Unit), and includes a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), an input / output interface, an internal bus, etc. The control unit 5 operates based on a power supply voltage generated by a power supply generation unit (not shown).

[0024] When the radio waves reflected by the reflector 100 are in the millimeter wave band such as (5G) or in the frequency band of 1 GHz to 30 GHz including Sub-6, the radio waves used for communication between the user terminal U1 and the radio base station BS may be, for example, LTE, LTE-A, UMB, IEEE802.11 (Wi-Fi (registered trademark)), IEEE802.16 (WiMAX (registered trademark)), IEEE802.20, UWB, Bluetooth (registered trademark), or LPWA.

[0025] 3, the radio wave transmission system 10 (the reflector 100 and the control unit 5) is provided on the wall 1. Here, when the radio wave transmission system 10 is provided on the wall 1 of the building BD, the height from the ground is preferably 1 m to 14 m, and particularly preferably 2 m to 10 m, from the viewpoint of radio wave efficiency.

[0026] 3 shows an example in which the radio wave transmission system 10 is disposed on a wall 1, but the reflector 100 in the radio wave transmission system 10 may be disposed on the main surface of a window glass. When the reflector 100 is disposed on a window glass, it is preferable that the reflector substrate and resonant elements included in the reflector 100 are made of a transparent material with a luminous transmittance of 50% or more. When the reflector 100 is disposed on a window glass, the control unit 5 may be disposed away from the reflector 100 in another location, such as a wall portion adjacent to the window glass or a frame portion of the window glass.

[0027] Furthermore, the radio wave transmission system 10 of the present disclosure may be installed on an indoor wall or window glass. In this case, it contributes to reducing blind zones indoors. When the radio wave transmission system 10 is installed indoors, the height from the floor is preferably 0.5 m to 3 m, and particularly preferably 1 m to 2 m, from the viewpoint of radio wave efficiency.

[0028] <Configuration, Principle, and Operation of Reflector 100> Next, the configuration, principle, and operation of the reflector 100 will be described with reference to FIGS. 4 to 7D.

[0029] Fig. 4 is a diagram showing an example of an arrangement of a plurality of cells of the reflector 100. Fig. 4 illustrates a case where vertically polarized radio waves are reflected, but the same applies to horizontally polarized waves.

[0030] As shown in Fig. 4, the reflector 100 has a plurality of regularly arranged cells 110. The cells 110 are an example of a reflecting portion. The cells 110 are configured as repeating units, and for example, in Fig. 4, ten cells 110 are arranged in each of the X and Y directions.

[0031] The reflector 100 can adjust the reflection angle of the radio waves reflected by the reflector 100 to an angle other than specular reflection or to the angle of specular reflection by controlling the amount of phase change (phase change amount) when the radio waves are reflected by each cell 110. As an example, as shown in Fig. 4, the reflection angle of the reflected wave can be adjusted by arranging 10 cells 110 in each of the X direction and the Y direction.

[0032] The amount of phase change of each cell 110 of the reflector 100 can be controlled in a binary manner or in a multi-value manner having more than two values. The reflector 100 reflects radio waves in a desired reflection direction by controlling the amount of phase change of each cell 110 and adjusting the reflection angle when the reflector 100 reflects radio waves. Note that here, a case where the phase of radio waves is controlled in a binary manner will be described.

[0033] 4, the arrangement of the plurality of cells 110 is not limited to the array shape shown in Fig. 4, and may be, for example, randomly (irregularly) arranged without any regularity. Ten or more cells 110 are arranged in the X direction and the Y direction, and the number of cells arranged in the X direction and the Y direction is preferably 130 or less, and more preferably 100 or less.

[0034] Each cell 110 includes a resonator element 111 and resonator elements 112H and 112V. The cell 110 is an example of a reflector, the resonator element 111 is an example of a first resonator element, and the resonator elements 112H and 112V are each an example of a second resonator element. The resonator element 112H is used to change the amount of phase change imparted to horizontally polarized radio waves, and the resonator element 112V is used to change the amount of phase change imparted to vertically polarized radio waves. The resonator element 111 is a resonator element that can resonate independently at a predetermined resonant frequency. The resonator elements 112H and 112V each include a switching element that can electrically switch the resonant frequency in the horizontal and vertical directions between a first resonant frequency and a second resonant frequency, but this element is omitted from FIG. 4 . Details of the cell 110 will be described later using FIG. 6 .

[0035] Further, here, we will describe a configuration in which each cell 110 has a resonant element 111 and resonant elements 112H and 112V, but each cell 110 may also be configured to have a resonant element 111 and either one of resonant elements 112H and 112V.

[0036] When the switching element of the resonator element 112H is in the off state, the resonant frequency in the horizontal direction is the first resonant frequency, and when the switching element of the resonator element 112H is in the on state, the resonant frequency in the horizontal direction is the second resonant frequency. When the switching element of the resonator element 112V is in the off state, the resonant frequency in the vertical direction is the first resonant frequency, and when the switching element of the resonator element 112V is in the on state, the resonant frequency in the vertical direction is the second resonant frequency. Note that the first resonant frequencies in the horizontal and vertical directions may be different, and the first resonant frequencies in the horizontal and vertical directions may be different.

[0037] Hereinafter, switching the switching element of the resonant element 112H on and off will be referred to as turning the cell 110 on or off in the horizontal direction, and switching the switching element of the resonant element 112V on and off will be referred to as turning the cell 110 on or off in the vertical direction. Furthermore, when no particular distinction is made between the horizontal and vertical directions, switching the switching element of either the resonant element 112H or 112V on and off will be referred to as turning the cell 110 on or off.

[0038] By controlling the on / off of the cells 110, the angle at which the reflector 100 reflects the incident radio waves can be set to a desired horizontal or vertical direction. Details of turning the cells 110 on and off will be described later using Figures 6 and 7A to 7D. In Figure 4, on cells 110 are shown in white, and off cells are shown with dots. The cells 110 are active cells whose on / off is controlled by the control unit 5.

[0039] When controlling with more than two values, it is preferable to provide an electrically controlled phase shifter in each cell 110. The phase shifter is an example of a phase adjustment unit. It is preferable to use a liquid crystal or a ferroelectric material as the phase shifter. The phase shifter can change the phase of the radio wave to any value within a continuous range, making it suitable for multi-value control.

[0040] 5A and 5B are diagrams illustrating an example of the principle of adjusting the reflection angle at the reflector 100. The reflector 100 is an array called a RIS (Reconfigurable Intelligent Surface) that can adjust the beam directivity. In FIGS. 5A and 5B, d is the pitch in the X direction between adjacent cells 110. In FIGS. 5A and 5B, in order to easily understand the incidence and reflection of horizontally polarized radio waves in adjacent cells 110 in the XZ plane, the positions at which the radio waves enter the reflecting surface (the surface on the +Z direction side) of the reflector 100 and the positions at which the radio waves exit from the reflecting surface are shown shifted in the X direction.

[0041] The reflector 100 changes the phase of radio waves when reflecting them from each of the plurality of cells 110 arranged in an array, thereby adjusting the propagation direction of the beam that is the reflected wave.

[0042] 5A , the direction in which the radio waves are reflected by all the cells 110 included in one reflector 100 can be adjusted by setting, for each cell 110, the amount by which the cell 110 changes the phase (phase change amount) when reflecting radio waves, taking into account the spacing between the cells 110 in the X and Y directions, for radio waves incident on the reflecting surface (surface on the +Z direction side) of the reflector 100. The direction in which the radio waves are reflected by all the cells 110 is synonymous with the reflection angle of the reflector 100 as a whole.

[0043] For example, when a radio wave incident along the Z axis is reflected in the XZ plane, the reflection direction can be changed by adding a phase to each cell 110. In other words, the reflection direction of the radio wave can be changed by adding a phase to each location X on the reflector 100.

[0044] 5A, when a radio wave emitted from point F at coordinates (Xf, Yf, Zf) is incident on and reflected by point at coordinates (X, Y, 0) on the reflecting surface of reflector 100 and reaches point P at coordinates (Xp, Yp, Zp), the phase Ψ(X, Y) added to the radio wave by the reflecting surface of reflector 100 can be expressed by the following equation (1): where constant k is 2π / λ, and λ is the wavelength of the radio wave in free space.

[0045] The coordinates (Xp, Yp, Zp) are called a focus in the sense that they are the points where radio waves are gathered to receive them.

[0046]

[0047] In equation (1), the distribution of the phase Ψ(X, Y) added to the radio wave on the reflecting surface of the reflector 100 is nonlinear with respect to the position X. If point F and point P are sufficiently far apart, equation (1) can be approximated to a linear equation with respect to the coordinates X and Y on the reflecting surface.

[0048] 5B shows radio waves incident on adjacent cells 110 in the X and Y directions at a pitch d at a zenith angle θin and an azimuth angle φin, and radio waves reflected by the reflector 100 in the direction of a zenith angle θout and an azimuth angle φout, as viewed on the XZ plane. The zenith angle and the azimuth angle are represented by the zenith angle θ and the azimuth angle φ in FIG. 8, which will be described later.

[0049] When point F and point P are sufficiently far apart, as shown in Figure 5B, the radio waves incident on adjacent cells 110 at a pitch d are parallel, with the angles of incidence both being the zenith angle θin and the azimuth angle φin, and the radio waves reflected by the reflecting surface of the reflector 100 are also parallel, with the angles of reflection both being the zenith angle θout and the azimuth angle φout. In this case, the phase difference between the radio waves incident on adjacent cells 110 at a pitch d is, for example, d x sin θin x cos φin in the X direction, and the phase difference between the radio waves reflected by adjacent cells 110 at a pitch d is d x sin θout x cos φout. Also, although not shown in Figure 5B, the phase difference between the radio waves incident on adjacent cells 110 at a pitch d is, for example, d x sin θin x sin φin in the Y direction, and the phase difference between the radio waves reflected by adjacent cells 110 at a pitch d is d x sin θout x sin φout. By approximating equation (1) using the zenith angle θin and azimuth angle φin of incidence and the zenith angle θout and azimuth angle φout of reflection, and ignoring constant terms that do not depend on X and Y, the following equation (2) is obtained.

[0050]

[0051] By controlling the cells 110 so as to approximately realize the phase difference within the reflector 100 to realize the phase Ψ(X, Y) obtained in this manner, it is possible to reflect the radio waves incident on the reflector 100 in the desired direction. Note that when controlling the cells 110, even if the same value is added to the phase Ψ(X, Y) expressed by equation (1) for all the cells 110, the same result can be obtained, and the reflection angle of the reflector 100 as a whole does not change.

[0052] For example, by using a cell 110 that can continuously control the phase during reflection using a voltage, it is possible to realize the phase Ψ(X, Y) without any error, and the reflection direction at the reflector 100 can be changed.

[0053] Furthermore, by using the cell 110 that can control the amount of phase change during reflection using two values, namely, turning the voltage on and off, it is possible to approximately realize the phase Ψ(X, Y), and change the reflection direction at the reflector 100.

[0054] In order to add a phase Ψ(X, Y) to radio waves in each cell 110 that can be switched between an on state and an off state, it is sufficient to ensure a phase difference of approximately 180 degrees when reflected between the on state and the off state. For example, the phase Ψ(X, Y) is in the off state when it is between -90° and 90°, and in the on state when it is between -180° and -90° or between 90° and 180°, thereby roughly realizing the phase Ψ(X, Y). As a result, the reflection direction can be changed in each cell 110. This holds true for both equation (1) and equation (2).

[0055] The above-described selection of the ON state and the OFF state from the phase Ψ(X, Y) is merely an example, and the ON state and the OFF state may be selected within a range of 180° that does not overlap each other. For example, the OFF state may be from 20° to 180° or from −180° to −160°, and the ON state may be from −160° to 20°.

[0056] By doing this, the radio wave transmission system 10 can change the direction of the beam of radio waves emitted from a 5G base station, etc., and direct the beam in various directions or in any desired direction, or can create multiple beams.

[0057] 5A and 5B show radio waves reflected in the XZ plane, but as described above, the reflector 100 can also reflect radio waves in the YZ plane or in a plane that includes the Z axis and has an angle with respect to the XZ and YZ planes. Therefore, the reflector 100 is a reflector that can set the reflection angle to an angle other than specular reflection.

[0058] 4 shows an example of a state in which the on / off states of all cells 110 change in the X direction within each row, and the 10 cells 110 arranged in the Y direction within each column are all on or off, when reflecting vertically polarized radio waves. This corresponds to a case in which the on and off states are determined based on equation (2).

[0059] The arrangement of the cells 110 in the reflector 100 shown in FIG. 4 is an example, and the number of cells 110 provided in the array may be from several tens to several thousands.

[0060] <Configuration of Cell 110 Controlling Phase Change Amount Using Two Values: On and Off> FIG. 6 is a diagram showing an example of the configuration of the cell 110. The cell 110 controls the phase change amount in the horizontal or vertical direction using two values: on and off, and includes a resonant element 111 and resonant elements 112H and 112V adjacent to the resonant element 111. FIG. 6 also shows a substrate 101. The substrate 101 is the substrate 101 of the reflector 100 (see FIG. 4), and as an example, one reflector 100 includes one substrate 101. The size of the substrate 101 in a plan view is the size shown as the reflector 100 in FIG. 4. A ground layer is provided on the surface of the substrate 101 on the −Z direction side. The reflector 100 includes multiple cells 110. FIG. 6 shows a portion of the entire substrate 101 that corresponds to one cell 110. Although a configuration in which one reflector 100 includes one substrate 101 will be described, one reflector 100 may include a plurality of substrates 101. That is, one reflector 100 may have one substrate 101 for one or a plurality of cells 110.

[0061] The substrate 101 is, for example, a rectangular substrate in a planar view. The substrate 101 may be, for example, a flexible substrate made of a thin film of resin, or a rigid substrate that is not flexible. Flexibility refers to the ability of an object to bend without breaking to an extent that is visible from the outside. If the substrate 101 is a flexible substrate, it may be made of a flexible resin material such as fluorine, COP (Cyclo-Olefin Polymer), PET (Polyethylene terephthalate), PEN (Polyethylene naphthalate), polyimide, Peek (Polyether ether ketone), LCP (Liquid Crystal Polymer), or other composite materials. If the substrate 101 is a rigid substrate, it may be made of, for example, a substrate formed by bonding a core material to a prepreg made of glass cloth impregnated with epoxy resin or the like.

[0062] Furthermore, the substrate 101 may be formed of any material that is transparent to radio waves radiated from an outdoor base station or the like. "Transparent to the radiated radio waves" means, for example, that the transmission loss is 10 dB or less. "Substrate 101 is transparent to the radiated radio waves" means that the transmission loss of the substrate 101 is 10 dB or less, preferably 6 dB or less, more preferably 3 dB or less, and even more preferably 1 dB or less.

[0063] The substrate 101 may be transparent to visible light. "Transparent" to visible light means that the luminous transmittance is at least 40% or more, preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more.

[0064] As an example, a resin substrate (resin film) may be used as the substrate 101. Examples of resin materials that satisfy the above conditions include acrylic resins such as polymethyl methacrylate, cycloolefin resins, polycarbonate resins, and polyethylene terephthalate (PET). Alternatively, a glass plate may be used as the substrate 101. Examples of glass plates that satisfy the above conditions include soda-lime glass, alkali-free glass, Pyrex (registered trademark) glass, and quartz glass.

[0065] The resonator elements 111, 112H, and 112V are formed of a metal layer. If the substrate 101 is not formed of any material that is transparent to visible light, the metal layer can be formed of a metal thin film such as copper, nickel, or gold. If the substrate 101 is formed of any material that is transparent to visible light, the metal layer can be formed of a metal thin film such as zinc oxide (ZnO), tin oxide (SnO ２ The metal layer is preferably 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. Furthermore, when the substrate 101 is formed of any material that is transparent to visible light, the metal layer may be formed of a mesh-like metal thin film such as copper, nickel, or gold.

[0066] The resonator element 111 is a conductor having a square shape in a plan view. The resonator element 111 has an end side 111A extending along the X direction on the +Y direction side. Resonator elements 112H and 112V are parasitic on the resonator element 111. Since the resonator elements 112H and 112V are coupled to the resonator element 111 via electromagnetic field coupling, the resonator element 111 may be considered to be the main resonator element, and the resonator elements 112H and 112V to be parasitic resonators. The resonator element 112H is for horizontal polarization, and the resonator element 112V is for vertical polarization. The resonator elements 112H and 112V are positioned 90 degrees apart from the resonator element 111, with the resonator element 112H located on the +X direction side of the resonator element 111 and the resonator element 112V located on the +Y direction side of the resonator element 111, but have the same configuration.

[0067] The resonator element 112V has linear elements 112A and 112B and a PIN (p-intrinsic-n) diode 112C. The PIN diode 112C is an example of a switching element. The linear elements 112A and 112B extend parallel to the X direction. The linear element 112A is disposed on the +Y direction side of the end edge 111A of the resonator element 111, and the linear element 112B is disposed on the +Y direction side of the linear element 112A. The PIN diode 112C is provided between the linear elements 112A and 112B. As an example, the cathode of the PIN diode is connected to the linear element 112A, and the anode of the PIN diode 112C is connected to the linear element 112B.

[0068] RF chokes 113 and 114 are provided at the ends of the linear elements 112A and 112B on the −X direction side. The RF choke 113 is connected to a ground layer at ground potential (GND) on the back surface of the substrate 101, and the RF choke 114 is connected to a control terminal to which a control voltage BV is applied. The control voltage BV is applied from the control unit 5 (see FIG. 2).

[0069] In order to obtain electromagnetic field coupling between the resonant element 111 and the linear element 112A, the distance between the end side 111A of the resonant element 111 and the linear element 112A is preferably, for example, λe / 10 or less, and more preferably about λe / 30, where λe is the electrical length of the wavelength at the frequency of the radio wave reflected by the reflector 100.

[0070] Similar to the resonator element 112V, the resonator element 112H includes linear elements 112A and 112B and a PIN (p-intrinsic-n) diode 112C. The operation of the resonator element 112H is similar to that of the resonator element 112V, and therefore will not be described in detail here.

[0071] The lengths in the X and Y directions in a plan view of the region in which the resonant element 111 and the resonant elements 112H and 112V are provided in one cell 110 are 2λ or less. While the square-shaped resonant element 111 is shown in Fig. 6, if the dimensions in the X and Y directions are not constant, for example, when the resonant element 111 is elliptical, it is sufficient that the maximum lengths in the X and Y directions in a plan view of the region in which the resonant element 111 and the resonant elements 112H and 112V are provided in one cell 110 are 2λ or less.

[0072] 7A to 7D are diagrams showing an example of the coupling state of the linear elements 112A and 112B of the resonator elements 112H and 112V to the resonator element 111 in the cell 110 by turning on and off the PIN diodes 112C of the resonator elements 112H and 112V. 7A to 7B show the linear element 112A or the linear elements 112A and 112B coupled to the resonator element 111, and omit other configurations.

[0073] 7A shows a coupling state when the PIN diode 112C (see FIG. 6) of the resonator element 112V is turned on by the control voltage BV applied from the control unit 5 (see FIG. 2), and the PIN diode 112C (see FIG. 6) of the resonator element 112H is turned off by the control voltage BV. Therefore, the linear element 112B is connected to the linear element 112A of the resonator element 112V, and the linear element 112B is not connected to the linear element 112A of the resonator element 112H. As a result, as shown in FIG. 7A, the linear elements 112A and 112B of the resonator element 112V and the linear element 112A of the resonator element 112H are coupled to each other in the resonator element 111.

[0074] 7B shows the coupling state when the PIN diodes 112C (see FIG. 6) of the resonator elements 112V and 112H are turned off by the control voltage BV applied from the control unit 5 (see FIG. 2). Therefore, the linear element 112B is not connected to the linear element 112A of the resonator element 112V, and the linear element 112B is not connected to the linear element 112A of the resonator element 112H. As a result, as shown in FIG. 7B, the linear element 112A of the resonator element 112V and the linear element 112A of the resonator element 112H are coupled to each other in the resonator element 111.

[0075] 7C shows a coupling state when the PIN diode 112C (see FIG. 6) of the resonator element 112V is turned off by the control voltage BV applied from the control unit 5 (see FIG. 2), and the PIN diode 112C (see FIG. 6) of the resonator element 112H is turned on by the control voltage BV. Therefore, the linear element 112B is not connected to the linear element 112A of the resonator element 112V, and the linear element 112B is connected to the linear element 112A of the resonator element 112H. As a result, as shown in FIG. 7C, the linear element 112A of the resonator element 112V and the linear elements 112A and 112B of the resonator element 112H are coupled to each other in the resonator element 111.

[0076] 7D shows the coupling state when the PIN diodes 112C (see FIG. 6) of the resonator elements 112V and 112H are both turned on by the control voltage BV applied from the control unit 5 (see FIG. 2). Therefore, the linear element 112B is connected to the linear element 112A of the resonator element 112V, and the linear element 112B is connected to the linear element 112A of the resonator element 112H. As a result, as shown in FIG. 7D, the linear elements 112A and 112B of the resonator element 112V and the linear elements 112A and 112B of the resonator element 112H are coupled to the resonator element 111.

[0077] 7A and 7B , the difference is that in Fig. 7A , the linear elements 112A and 112B of the resonator element 112V are coupled to the resonator element 111, whereas in Fig. 7B , only the linear element 112A of the resonator element 112V is coupled to the resonator element 111. Comparing the coupled states in Fig. 7A and 7B , the length of the resonator element 112V is longer and its shape changes in the coupled state in Fig. 7A . Therefore, when the PIN diode 112C (see Fig. 6 ) of the resonator element 112V is turned on as in the coupled state shown in Fig. 7A , the resonant frequency of the resonator element 112V drops to the first resonant frequency compared to when the PIN diode 112C of the resonator element 112V is off as in the coupled state shown in Fig. 7B . Conversely, when the PIN diode 112C (see FIG. 6) of the resonant elements 112V and 112H is turned off as in the coupled state shown in FIG. 7B, the resonant frequency of the resonant element 112V increases to the second resonant frequency compared to the state in which the PIN diode 112C of the resonant element 112V is on as in the coupled state shown in FIG. 7A.

[0078] It is known that when two resonant elements having substantially the same resonant frequency are placed close to each other, their mutual interaction changes the reflection characteristics. When the resonant frequency of the resonant element 111 is substantially the same as either the first resonant frequency or the second resonant frequency of the resonant element 112V, switching the PIN diode 112C of the resonant element 112V on and off changes the overall shape (or length) of the resonant elements 111 and 112V, thereby changing the reflection characteristics of the cell 110.

[0079] The size of the resonator element 111 and the linear elements 112A and 112B of the resonator element 112V are set so that the difference in absolute value of the phase shift imparted to the vertically polarized incident radio wave when the PIN diode 112C of the resonator element 112V is off and on is approximately 180 degrees. By way of example, approximately 180 degrees means a value within a range of 180 degrees ±45 degrees. Because the resonator elements 111 and 112V are made of conductors, there may be errors in the phase shift due to manufacturing errors, etc. However, if the phase shift imparted to the vertically polarized incident wave can be changed by approximately 180 degrees (180 degrees ±45 degrees) by switching the PIN diode 112C of the resonator element 112V on and off, the reflection angle of the vertically polarized radio wave of the reflector 100 as a whole can be adjusted to an angle other than specular reflection. Specular reflection is regular reflection, which refers to reflection in a direction in which an equiphase surface is generated by reflection due to ordinary metal reflection or the like.

[0080] Furthermore, the resonator elements 112H and 112V have the same linear elements 112A and 112B, and operate in the same manner, except that the angle differs by 90 degrees in plan view. That is, the size of the resonator element 111 and the linear elements 112A and 112B of the resonator element 112H are set so that the difference in absolute value of the phase shift imparted to the horizontally polarized incident radio wave when the PIN diode 112C of the resonator element 112H is off and on is approximately 180 degrees. If the phase shift imparted to the horizontally polarized incident wave can be changed by approximately 180 degrees (180 degrees ±45 degrees) by switching the PIN diode 112C of the resonator element 112H on and off, the reflection angle of the horizontally polarized radio wave of the reflector 100 as a whole can be adjusted to an angle other than specular reflection.

[0081] The reflector 100 can switch the reflection angle (reflection direction) of vertically polarized or vertically polarized incident waves at the reflector 100 as a collection of all cells 110 by switching on and off the PIN diode 112C of the resonant element 112H or 112V of each cell 110. That is, the reflector 100 can binary-control the amount of phase change in the horizontal or vertical direction by the control unit 5 switching on and off the PIN diode 112C of the resonant element 112H or 112V of each cell 110, and can adjust the reflection angle to an angle other than specular reflection. Specular reflection refers to regular reflection, which is reflection in a direction that generates an equal phase plane due to reflection by ordinary metal reflection, etc. Note that the reflector 100 can also adjust the reflection angle to the angle of specular reflection.

[0082] For example, in the vertical direction, the phase change amount can be controlled in a binary manner so that the phase change amount of the cell 110 is 30 degrees when the PIN diode 112C of the resonant element 112V is turned off, and the phase change amount of the cell 110 is 210 degrees when the PIN diode 112C is turned on. In this case, the phase change amount of 30 degrees is an example of a first value, and the phase change amount of 210 degrees is an example of a second value. The difference between the phase change amount when the PIN diode 112C of the resonant element 112V is turned off and the phase change amount when it is turned on is 120 degrees to 240 degrees in absolute value. In other words, the difference between the first and second values ​​of the phase change amount is 180±60 degrees in absolute value. By setting the difference between the first and second values ​​of the phase change amount to a value within this range, taking into account variations due to manufacturing errors, etc., the phase change amount can be controlled in a binary manner, and the reflection angle can be adjusted to an angle other than specular reflection.

[0083] Therefore, when the PIN diodes 112C of all the cells 110 are turned off in the vertical direction, the difference in the amount of phase change of all the cells 110 is 0 degrees. In reality, there is some variation, so the difference in the amount of phase change is approximately 0 degrees. This also applies when the PIN diodes 112C of all the cells 110 are turned on in the vertical direction.

[0084] In addition, in the vertical direction, if there are cells 110 in which the PIN diode 112C of the resonant element 112V is off and cells 110 in which the PIN diode 112C is on, the difference in the phase change amount (for example, 30 degrees and 210 degrees) of all the cells 110 is 180 degrees. In reality, there is some variation, so the difference in the phase change amount is approximately 180 degrees.

[0085] This also applies to the horizontal direction. Here, as an example, the resonant element 111 is square-shaped, and the resonant elements 112H and 112V have a PIN diode 112C between the two linear elements 112A and 112B. However, the shape of the resonant element 111 is not limited to a square shape and may be any planar shape as long as it is capable of reflecting radio waves. The resonant elements 112H and 112V may have different configurations. The resonant elements 112H and 112V may have any configuration as long as their shape and length can be changed by switching them with the control unit 5. The resonant elements are not limited to the PIN diode 112C, and may be a MEMS (Micro Electro Mechanical Systems) switch, a varactor, or a transistor such as a FET (Field Effect Transistor).

[0086] <Polar Coordinate System> Figure 8 is a diagram showing the zenith angle θ and azimuth angle φ in a polar coordinate system. The reflector 100 is located at the origin of the XYZ coordinate system. More specifically, the origin of the XYZ coordinate system is located at the center of the reflecting surface of the reflector 100. The zenith angle θ is an angle with respect to the +Z direction, and the angle downward from the +Z direction as shown by the arrow is considered positive. The azimuth angle φ is an azimuth angle with respect to the +X direction in the XY plane, and the angle from the +X direction toward the +Y direction as shown by the arrow is considered positive. r is the radius vector, and is the distance from the origin to the receiving point G where the receiving terminal U1 is located. The reflection angle of the reflector 100 is expressed by the zenith angle θ and the azimuth angle φ.

[0087] <Overall Configuration of Radio Wave Transmission System 10> Fig. 9 is a diagram showing an example of the overall configuration of the radio wave transmission system 10. The radio wave transmission system 10 includes a reflector 100, a control unit 5, an antenna 120, a stay 125, a power meter 130, and a cable 135. Fig. 9 also shows a base station RS. Fig. 9 also shows a memory 5A included in the control unit 5. The memory 5A is an example of a storage unit.

[0088] The antenna 120 is an antenna capable of receiving radio waves reflected by the reflector 100, and is connected to the power measuring device 130. The antenna 120 is installed at a fixed position relative to the reflector 100 by a stay 125. When the antenna 120 is fixed to the reflector 100 by the stay 125, the positional relationship between the reflector 100 and the antenna 120 is fixed, and the position of the antenna 120 relative to the reflector 100 is known. The position of the antenna 120 relative to the reflector 100 is expressed by a radius vector r1, a zenith angle θ1, and an azimuth angle φ1 in a polar coordinate system with the center of the reflecting surface 100A of the reflector 100 as the origin. The center of the reflecting surface 100A is the center of the reflecting surface 100A in the X and Y directions.

[0089] The antenna 120 is located on the +Z direction side of the reflector 100. It is preferable that the antenna 120 has directivity in the -Z direction and does not have directivity in the direction in which the radio base station BS is located. This is because it is preferable that the antenna 120 does not receive power from the radio base station BS. A horn antenna or the like is a preferable example of such an antenna 120.

[0090] As an example, it is preferable that the antenna 120 fixed to the reflector 100 by the stay 125 is positioned on a normal line passing through the center of the reflecting surface 100A of the reflector 100. This is because the antenna 120 positioned on the normal line of the reflecting surface 100A is more likely to receive radio waves reflected in various directions by the reflector 100.

[0091] Moreover, as an example, the antenna 120 and the stay 125 are detachable from the reflector 100. A portion where the stay 125 to which the antenna 120 is attached is attached to the housing of the reflector 100 is an example of a fixing portion that fixes the antenna 120 to the reflector 100.

[0092] The antenna 120 and the stay 125 may be fixedly attached to the reflector 100 rather than being detachable from the reflector 100. The stay 125 is a fixture for attaching the antenna 120 to the reflector 100, and may have any shape or size as long as it is configured to suppress the influence on the incidence and reflection of radio waves on the reflector 100 and the reception of radio waves by the antenna 120.

[0093] The power meter 130 is connected to the antenna 120 and measures the power received by the antenna 120. The power meter 130 may be fixed to the antenna 120 or may be fixed to the stay 125. The power meter 130 is connected to the control unit 5 via a cable 135 and transmits (feeds back) data indicating the measured power to the control unit 5 via the cable 135. When the antenna 120 is detachable from the reflector 100, the power meter 130 may be configured to be detachable from the reflector 100 together with the antenna 120 and the stay 125, for example.

[0094] The cable 135 is provided to transmit data representing the power measured by the power meter 130 to the control unit 5. When the antenna 120 is detachable from the reflector 100, the cable 135 may be configured to be detachable from the control unit 5, for example. In this case, after the total phase distribution of the reflector 100 has been appropriately set, the antenna 120, the stay 125, the power meter 130, and the cable 135 can be removed, leaving the reflector 100 and the control unit 5. Note that instead of connecting the power meter 130 and the control unit 5 with the cable 135, data representing the power measured by the power meter 130 may be transmitted to the control unit 5 by, for example, short-range wireless communication between the power meter 130 and the control unit 5.

[0095] <Method for Setting Total Phase Distribution> The method for setting the total phase distribution described here is included in the radio wave transmission method executed by the radio wave transmission system 10.

[0096] Here, as shown in Fig. 2, a method for appropriately setting the total phase distribution of the reflector 100 so that the reflector 100 reflects radio waves R transmitted from the base station RS and the reflected radio waves R reach the user terminal U1 will be described. In the following, the user terminal U1 will be referred to as the target terminal, and the base station RS will be referred to as the wave source. The target terminal is not limited to a terminal used by a user such as the user terminal U1, but may be any receiver that receives radio waves reflected by the reflector 100. In addition, the wave source is not limited to a base station RS, but may be any device that emits or reflects radio waves that can be reflected by the reflector 100.

[0097] The total phase distribution represents the distribution of multiple phase change amounts that change the phase of radio waves when all of the multiple cells 110 included in the reflector 100 reflect the radio waves as incident waves. The total phase distribution can be divided into an incident phase distribution and a reflected phase distribution. The total phase distribution is a phase distribution that combines the incident phase distribution and the reflected phase distribution.

[0098] The reflection phase distribution is a phase distribution on the reflection side that is determined by the positional relationship between the reflector 100 and a receiving unit that receives radio waves reflected by the reflector 100. The receiving unit is, for example, an antenna 120 or a target terminal. The positional relationship between the reflector 100 and the receiving unit can be expressed by XYZ coordinates or by the radius vector r, zenith angle θ, and azimuth angle φ of polar coordinates.

[0099] The incident phase distribution can be obtained by subtracting the reflected phase distribution from the total phase distribution. The incident phase distribution is a phase distribution on the incident side that is determined by the positional relationship between the incident wave and the reflector 100. The positional relationship between the incident wave and the reflector 100 can be expressed by XYZ coordinates or the radial coordinate r, zenith angle θ, and azimuth angle φ of polar coordinates, so the incident phase distribution can be obtained without subtracting the reflected phase distribution from the total phase distribution.

[0100] The incident waves on the reflector 100 include direct path incident waves that arrive directly from the base station RS without being reflected by a wall or the like, and multipath incident waves that are reflected by a wall or the like. There may also be cases where an incident wave that is a composite of a direct path incident wave and one or more multipath incident waves is incident on the reflector 100. The incident waves that determine the incident phase distribution are the direct path incident wave, the multipath incident wave, or a composite wave of a direct path incident wave and one or more multipath incident waves that may be incident on the reflector 100.

[0101] In the method of setting the total phase distribution included in the radio wave transmission method executed by the radio wave transmission system 10, the position of the reflector 100 is fixed. That is, the position of the reflector 100 relative to the wave source is fixed. Although the position of the wave source is unknown, fixing the position of the reflector 100 fixes the position of the reflector 100 relative to the wave source, whose position is unknown.

[0102] Then, the following process is performed to obtain the incident phase distribution, and then the predetermined total phase distribution is obtained. The predetermined total phase distribution is the total phase distribution for reflecting the radio waves arriving from the wave source toward the target terminal by the reflector 100.

[0103] <Method of Determining Incident Phase Distribution> First, with the position of the reflector 100 fixed, the total phase distribution of the reflector 100 is adjusted by the control unit 5 to determine the total phase distribution that maximizes the received power at the antenna 120. That is, by adjusting the total phase distribution so that the reflector 100 reflects toward the antenna 120, the direction of arrival of the radio waves arriving from the wave source (the direction of arrival including multipath) is searched for.

[0104] Next, once the total phase distribution that maximizes the received power of the antenna 120 has been determined, an incident phase distribution is determined based on the first reflected phase distribution determined by the positional relationship between the antenna 120 and the reflector 100 and the determined total phase distribution, and is stored in memory 5 A. As an example, the incident phase distribution can be determined by subtracting the first reflected phase distribution from the determined total phase distribution.

[0105] <How to Calculate the Predetermined Total Phase Distribution> The incident phase distribution calculated with the position of the reflector 100 fixed is the incident phase distribution at the reflector 100 whose position is fixed relative to a wave source whose position is unknown, and therefore remains unchanged even if the reflection direction of the reflector 100 changes. Therefore, by combining the incident phase distribution calculated in this manner with a second reflection phase distribution determined by the positional relationship between the reflector 100 and the target terminal, it is possible to calculate the predetermined total phase distribution for reflecting radio waves arriving from the wave source toward the target terminal by the reflector 100. The positional relationship between the reflector 100 and the target terminal can be expressed in XYZ coordinates or polar coordinates with radius vector r, zenith angle θ, and azimuth angle φ, and therefore the second reflection phase distribution can be calculated.

[0106] 10A is a diagram showing an example of an incident phase distribution, a first reflection phase distribution, and a total phase distribution obtained by the radio wave transmission system 10. FIG. 10A shows an example of a result of a simulation performed using the radio wave transmission system 10.

[0107] (1) Incident phase distribution, (2) first reflected phase distribution, (3) total phase distribution, and (4) total phase distribution (binary) show the distribution of phases at positions corresponding to each cell in the reflector 100, in which 40 cells 110 are arranged in each of the X and Y directions. In (1) incident phase distribution, (2) first reflected phase distribution, and (3) total phase distribution, the position of 0 degrees phase is shown in white, the position of 359 degrees phase is shown in black, and the range between 0 degrees phase and 359 degrees phase is shown in monotone gradation. (4) Total phase distribution (binary) shows the distribution of on and off obtained by binarization. White indicates on cells 110, and black indicates off cells 110.

[0108] 10A are obtained by the control unit 5 of the radio wave transmission system 10 when the position of the wave source is unknown. When the position of the wave source is unknown, the positional relationship between the incident wave and the reflector 100 is unknown.

[0109] With the position of the reflector 100 fixed, (1) the incident phase distribution when radio waves arriving from a certain direction are incident on the reflector 100 is generated, and (2) the first reflected phase distribution is added to obtain (3) the total phase distribution. (1) The incident phase distribution when radio waves arriving from a certain direction are incident is an incident phase distribution determined by the positional relationship between the incident wave and the reflector 100 when radio waves (incident waves) from a certain incident direction are incident on the reflector 100.

[0110] (2) The first reflection phase distribution can be calculated based on the known positional relationship between the reflector 100 and the antenna 120. (2) The first reflection phase distribution may be calculated by the control unit 5 based on the known positional relationship between the reflector 100 and the antenna 120, or may be calculated in advance and stored in the memory 5A of the control unit 5.

[0111] While changing the incident direction relative to the reflector 100, an incident phase distribution (1) corresponding to the incident direction is generated, and the total phase distribution (3) obtained by adding the first reflected phase distribution (2) to the incident phase distribution (1) is binarized to obtain a total phase distribution (4) (binary). Then, the on / off distribution of each cell 110 of the reflector 100 is set using the total phase distribution (binary), and the received power of the antenna 120 is measured by the power meter 130.

[0112] In this way, an experiment was conducted in which (1) incident phase distribution was generated, (4) total phase distribution (binary), and the received power of antenna 120 was measured with power measuring device 130 while changing the zenith angle θ and the azimuth angle φ in increments of 0.5 degrees. (1) Incident phase distribution, (2) first reflected phase distribution, (3) total phase distribution, and (4) total phase distribution (binary) shown in Figure 10A are those obtained when the received power of antenna 120 was maximized as a result of the above experiment.

[0113] The (4) total phase distribution (binary) when the received power of the antenna 120 is maximized may be calculated as follows. That is, first, the (3) total phase distribution that realizes the (4) total phase distribution (binary) when the received power of the antenna 120 is maximized is calculated, and then the (2) first reflected phase distribution is subtracted from the (3) total phase distribution to calculate the (1) incident phase distribution. This calculation method also makes it possible to calculate the (1) incident phase distribution, (2) first reflected phase distribution, (3) total phase distribution, and (4) total phase distribution (binary) shown in FIG. 10A .

[0114] Next, for comparison, the incident phase distribution, the first reflection phase distribution, and the total phase distribution that can be obtained when the positional relationship between the incident wave and the reflector 100 is known will be described using Fig. 10B. Fig. 10B is a diagram showing an example of a simulation result for comparison. Similar to Fig. 10A, Fig. 10B shows (1) the incident phase distribution, (2) the first reflection phase distribution, (3) the total phase distribution, and (4) the total phase distribution (binary).

[0115] In the comparative experiment, the positional relationship between the incident wave and the reflector 100 is known, so the incident phase distribution can be calculated based on the positional relationship between the incident wave and the reflector 100. The calculated incident phase distribution is shown in (1) of Figure 10B. When compared with the incident phase distribution (1) of Figure 10A, it can be seen that the incident phase distribution (1) of Figure 10A is very similar to the incident phase distribution (1) of Figure 10B.

[0116] Furthermore, (2) the first reflection phase distribution is calculated based on the positional relationship between the reflector 100 and the antenna 120, and is therefore substantially the same as the first reflection phase distribution shown in (2) in FIG. 10A.

[0117] The (3) total phase distribution is obtained by adding the (1) incident phase distribution and the (2) first reflected phase distribution. The (3) total phase distribution shown in Figure 10B is a phase distribution obtained using the incident phase distribution calculated when the positional relationship between the incident wave and the reflector 100 is known. Compared with the (3) total phase distribution shown in Figure 10A, it can be seen that the (3) total phase distribution shown in Figure 10A is very similar to the (3) total phase distribution shown in Figure 10B.

[0118] Furthermore, the total phase distribution (binary) shown in (4) of FIG. 10B was obtained by performing binarization processing on the total phase distribution (3) shown in FIG. 10B.

[0119] The incident phase distribution included in the total phase distribution (binary) shown in (4) of Figure 10B was calculated under the conditions that the zenith angle θ of the incident angle of the incident wave on the reflector 100 is 30.0 degrees and the azimuth angle φ is 45.0 degrees.

[0120] In contrast, the incident angle of the incident wave on the reflector 100, represented by the incident phase distribution included in the total phase distribution (binary) shown in (4) of Fig. 10A, was a zenith angle θ of 30.0 degrees and an azimuth angle φ of 44.0 degrees. The zenith angle θ calculated by the radio wave transmission system 10 was the same as the theoretical value (30.0 degrees), and the deviation of the azimuth angle φ from the theoretical value (45.0 degrees) was 1 degree.

[0121] In this way, it was confirmed that the radio wave transmission system 10 can obtain the incident phase distribution with extremely high accuracy.

[0122] <Maximum Distance Between Reflector 100 and Target Terminal> The target terminal needs to be able to operate using radio waves reflected by the reflector 100. For this reason, the control unit 5 calculates the maximum distance between the reflector 100 and the target terminal at which the target terminal can receive the radio waves reflected by the reflector 100 with minimum received power, based on the radiated power at the wave source, the distance between the wave source and the reflector 100, the distance between the reflector 100 and the antenna 120, the received power at the antenna 120, and the minimum received power required at the target terminal.

[0123] 11 is a diagram for explaining how to determine the maximum distance between the reflector 100 and the target terminal. In addition to the reflector 100 and antenna 120, the wave source 20 and the target terminal 30 are also shown in FIG.

[0124] Radiation power P of the wave source 20 ０ , the distance r between the wave source 20 and the reflector 100 ０ , the received power P at the antenna 120 when the total phase distribution that maximizes the received power at the antenna 120 is obtained. １ , the distance r between the reflector 100 and the antenna 120 １ , and the minimum received power P required at the target terminal 30 ２If the distance r is known, the maximum distance r between the reflector 100 and the target terminal 30 at which the target terminal 30 can receive the radio wave reflected by the reflector 100 with the minimum reception power can be calculated. ２ Specifically, it is possible to obtain the following:

[0125] First, the distance r between the wave source 20 and the reflector 100 ０ When the size of the reflecting surface 100A of the reflector 100 is larger than twice the Fresnel radius between the wave source 20 and the antenna 120, the distance r between the wave source 20 and the reflector 100 is calculated using the following equation (3). ０ Equation (3) is the Friis equation.

[0126]

[0127] Furthermore, when the size of the reflecting surface 100A of the reflector 100 is smaller than twice the Fresnel radius between the wave source 20 and the antenna 120, the distance r between the wave source 20 and the reflector 100 is calculated using the following equation (4). ０ Equation (4) takes into account the radar cross section RCS.

[0128]

[0129] In formulas (3) and (4), G ０ is the gain of the wave source 20, G １ is the gain of the antenna 120, λ is the wavelength of the radio wave, η １ is a coefficient that represents the efficiency including the reflection loss and the angle factor. σ is the radar cross section RCS of the reflector 100, and σ=4πA ２ / λ ２ where A is the area of ​​the reflecting surface 100A of the reflector 100.

[0130] 12A and 12B , the Fresnel radius d between the wave source 20 and the antenna 120 will be described. Figures 12A and 12B are diagrams illustrating an example of the relationship between the Fresnel radius d between the wave source 20 and the antenna 120 and the size of the reflecting surface 100A of the reflector 100. Figures 12A and 12B show a linear path from the wave source 20 to the antenna 120 via the reflector 100, and a first Fresnel region surrounded by the Fresnel radius d is indicated by dots.

[0131] The Fresnel radius d between the wave source 20 and the antenna 120 is expressed by the following equation (5).

[0132]

[0133] 12A and 12B show the Fresnel radius d between the wave source 20 and the antenna 120. In Fig. 12A, the reflecting surface 100A of the reflector 100 is larger than a circle having a diameter twice the Fresnel radius d (2d), and in Fig. 12B, the reflecting surface 100A of the reflector 100 is smaller than a circle having a diameter twice the Fresnel radius d (2d).

[0134] 12A , when the reflecting surface 100A of the reflector 100 is larger than a circle having a diameter that is twice the Fresnel radius d (2d), the reflector 100 can reflect all of the radio waves arriving from the wave source 20 toward the antenna 120. On the other hand, when the reflecting surface 100A of the reflector 100 is smaller than a circle having a diameter that is twice the Fresnel radius d (2d), the reflector 100 will reflect only a portion of the components of the radio waves arriving from the wave source 20 that are located in the center of the Fresnel radius d toward the antenna 120.

[0135] Due to this difference, when the size of the reflecting surface 100A of the reflector 100 is larger than twice the Fresnel radius between the wave source 20 and the antenna 120, the distance r between the wave source 20 and the reflector 100 can be calculated using equation (3). ０ In addition, when the size of the reflecting surface 100A of the reflector 100 is smaller than twice the Fresnel radius between the wave source 20 and the antenna 120, the distance r between the wave source 20 and the reflector 100 can be calculated using equation (4). ０ All we need to do is find the answer.

[0136] In addition, when the size of the reflecting surface 100A of the reflector 100 is larger than twice the Fresnel radius between the wave source 20 and the target terminal 30, the radiation power P ０ , and the minimum received power P required at the target terminal 30 ２ If is known, the distance r calculated based on the formula (3) or the formula (4) can be calculated. ０Using the above, the maximum distance r between the reflector 100 and the target terminal 30 at which the target terminal 30 can receive the radio wave reflected by the reflector 100 with the minimum reception power is calculated using the following equation (6). ２ can be obtained.

[0137]

[0138] In formula (6), G ０ is the gain of the wave source 20, G ２ is the gain of the target terminal 30, η ２ is a coefficient that represents the efficiency including reflection loss and angle factor.

[0139] Furthermore, when the size of the reflecting surface 100A of the reflector 100 is smaller than twice the Fresnel radius between the wave source 20 and the target terminal 30, the maximum distance r between the reflector 100 and the target terminal 30 at which the target terminal 30 can receive the radio waves reflected by the reflector 100 with the minimum reception power is calculated using the following equation (7). ２ Equation (7) takes into account the radar cross section RCS.

[0140]

[0141] In formula (7), G ０ is the gain of the wave source 20, G ２ is the gain of the target terminal 30, λ is the wavelength of the radio wave, η ２ is a coefficient that represents the efficiency including the reflection loss and the angle factor. σ is the radar cross section RCS of the reflector 100, and σ=4πA ２ / λ ２ where A is the area of ​​the reflecting surface 100A of the reflector 100.

[0142] Here, the Fresnel radius between the wave source 20 and the target terminal 30 is expressed as r in equation (5) which expresses the Fresnel radius d between the wave source 20 and the antenna 120. １ r ２ It has been replaced with.

[0143] 13 is a flowchart showing an example of processing executed by the control unit 5. The control unit 5 starts processing in a state where the reflector 100 is fixed in a known position and the antenna 120 is attached to the reflector 100.

[0144] The control unit 5 sets an incident phase distribution (step S1) in order to search for the arrival direction of the incident wave on the reflector 100. When step S1 is performed for the first time, the incident phase distribution may be set to an initial value.

[0145] The control unit 5 binarizes the total phase distribution obtained by adding the reflected phase distribution to the incident phase distribution, and sets the on / off state of each cell 110 of the reflector 100 (step S2).

[0146] The control unit 5 causes the power measuring device 130 to measure the received power at the antenna 120 (step S3).

[0147] The control unit 5 determines whether all the incident directions have been searched (step S4). For example, the maximum incident direction may be determined in advance as a range of the zenith angle θ and the azimuth angle φ, and the control unit 5 may determine whether all the incident directions have been searched by performing the processes of steps S1 to S4 while changing the zenith angle θ and the azimuth angle φ in increments of a predetermined angle (for example, 0.5 degrees) in step S1.

[0148] If the control unit 5 determines that all incident directions have not been searched (S4: NO), the flow returns to step S1, and as a result, the processes of steps S1 to S4 are repeated.

[0149] When the control unit 5 determines in step S4 that all incident directions have been searched (S4: YES), it extracts the incident phase distribution included in the total phase distribution that maximizes the received power and stores it in the memory 5A (step S5).The incident phase distribution corresponding to the maximum received power can be extracted from the received power of the antenna 120 obtained by repeatedly performing the processes of steps S1 to S4.

[0150] The control unit 5 calculates the maximum distance between the reflector 100 and the target terminal 30 (step S6). The maximum distance between the reflector 100 and the target terminal 30 is the maximum distance between the reflector 100 and the target terminal 30 at which the target terminal 30 can receive the radio waves reflected by the reflector 100 with the minimum reception power.

[0151] The control unit 5 may determine whether the distance between the reflector 100 and the target terminal 30 is equal to or less than the maximum distance after step S6. In this process, data representing the distance between the reflector 100 and the target terminal 30 may be input to the control unit 5.

[0152] The control unit 5 obtains a target total phase distribution by combining the second reflected phase distribution according to the positional relationship between the reflector 100 and the target terminal 30 and the incident phase distribution stored in the memory 5A (step S7).

[0153] The control unit 5 generates a target total phase distribution (binary) by binarizing the target total phase distribution (step S8). By setting the on / off state of each cell 110 of the reflector 100 according to the target total phase distribution (binary), it is possible to reflect radio waves arriving at the reflector 100 from the wave source 20 to the target terminal 30, and to maximize the received power at the target terminal 30.

[0154] This completes the series of processes (END). Although the above description has been given of the form in which the maximum distance between the reflector 100 and the target terminal 30 is obtained in step S6, the series of processes does not necessarily have to include the process in step S6.

[0155] As described above, the radio wave transmission system 10 is installed at a fixed position relative to the reflector 100 and includes the antenna 120 capable of receiving radio waves reflected by the reflector 100, and the incident phase distribution is calculated in a state in which the reflection direction of the reflector 100 is adjusted so as to increase the received power at the antenna 120. The incident phase distribution is a phase distribution on the incident side determined by the positional relationship between the incident wave and the reflector 100, and is therefore a fixed phase distribution that is uniquely determined as long as the position of the reflector 100 is fixed.

[0156] Here, the radio waves incident on the reflector 100 include direct path incident waves that arrive directly from the wave source 20 and multipath incident waves that are reflected by walls, etc., so it is not easy to calculate the incident phase distribution. This is because various incident waves can exist, and it is not easy to calculate the positional relationship between the incident wave and the reflector 100.

[0157] On the other hand, the reflection phase distribution can be calculated because it is determined by the positional relationship between the reflector 100 and the target terminal 30.

[0158] Therefore, when setting the reflection direction from the fixed-position reflector 100 to the target terminal 30, the radio wave transmission system 10 obtains the incident phase distribution by adjusting the reflection direction of the reflector 100 using the antenna 120, which is placed at a fixed position relative to the reflector 100. The radio wave transmission system 10 also calculates the reflection phase distribution based on the positional relationship between the reflector 100 and the target terminal 30. The radio wave transmission system 10 then combines the incident phase distribution and the reflection phase distribution to easily obtain the target total phase distribution that maximizes the received power at the target terminal 30.

[0159] Because the conventional adjustment method cannot obtain the incident phase distribution, when setting the reflection direction of a reflector that reflects radio waves arriving from the wave source 20 toward the target terminal 30, it is necessary to simultaneously adjust both the incident direction of the radio waves on the reflector and the reflection direction of the radio waves from the reflector, which requires a huge amount of work. In particular, when reflecting highly directional radio waves such as Sub-6 or millimeter wave band radio waves, the tolerance for adjustment of the incident direction and reflection direction is small, and if the angle of the incident direction or reflection direction is off by a few degrees, the strength of the radio waves reaching the target terminal 30 drops significantly, making adjustment difficult even for experienced workers and requiring a huge amount of time and effort.

[0160] In contrast, in the radio wave transmission system 10, the reflection phase distribution can be calculated from the relative positions of the reflector 100 and the target terminal 30, and the incident phase distribution can be obtained by adjusting the reflection direction of the reflector 100 using the antenna 120. Therefore, the target total phase distribution can be easily obtained by simply combining the incident phase distribution and the reflection phase distribution. Because the radio wave transmission system 10 can use calculated values ​​for the reflection phase distribution, the effort required for adjustment is approximately half that of conventional adjustment methods.

[0161] Furthermore, if both the incident direction and the reflection direction are adjusted simultaneously without determining the incident phase distribution as in conventional adjustment methods, there is a risk of falling into a local solution in which the received power at the target terminal 30 is set to a local maximum value that is not the maximum. In contrast, the radio wave transmission system 10 uses the antenna 120 to determine the incident phase distribution that maximizes the received power at the antenna 120, thereby significantly reducing the possibility of falling into a local solution.

[0162] <Effects> The radio wave transmission system 10 includes a reflector 100 capable of scanning the reflection direction, a control unit 5 that controls the reflection direction of the reflector 100, an antenna 120 that is installed at a fixed position relative to the reflector 100 and is capable of receiving radio waves reflected by the reflector 100, and a memory 5A. The control unit 5 adjusts the reflection direction of the reflector 100 so that the received power at the antenna 120 is increased, and stores in the memory 5A an incident phase distribution obtained based on a total phase distribution that represents the distribution of phase changes that the reflector 100 imparts to the incident wave and a first reflection phase distribution that is determined by the positional relationship between the antenna 120 and the reflector 100. The control unit 5 calculates a target total phase distribution realized by the incident phase distribution and a second reflection phase distribution that is in accordance with the positional relationship between the reflector 100 and a target terminal that is located in a predetermined reflection direction relative to the reflector 100.

[0163] In this way, the reflected phase distribution can be calculated from the positional relationship between the reflector 100 and the target terminal 30, and the radio wave transmission system 10 can determine the incident phase distribution, so the target total phase distribution can be easily determined simply by combining the incident phase distribution and the reflected phase distribution.

[0164] Therefore, it is possible to provide a radio wave transmission system 10 in which the incident direction and reflection direction of the reflector 100 can be easily adjusted.

[0165] Furthermore, the antenna 120 is detachable from a fixing portion that fixes the antenna 120 to the reflector 100. Since the antenna 120 is no longer needed after the incident phase distribution is determined, the reflector 100 can be used with unnecessary parts removed. Furthermore, this improves the degree of freedom in selecting the reflection direction of the radio wave when determining the target total phase distribution.

[0166] Furthermore, since the antenna 120 is positioned in the normal direction to the reflecting surface of the reflector 100, it is possible to easily receive radio waves reflected in various directions by the reflector 100.

[0167] Furthermore, the control unit 5 adjusts the reflection direction by controlling the total phase distribution of the reflector 100 so as to increase the received power at the antenna 120, and finds the total phase distribution that maximizes the received power at the antenna 120. This makes it possible to find the incident phase distribution in a state where the received power at the antenna 120 is maximized, and to easily find the target total phase distribution that maximizes the received power at the target terminal 30.

[0168] The control unit 5 also controls the radiated power P ０ and the distance r between the wave source 20 and the reflector 100 ０ and the distance r between the reflector 100 and the antenna 120 １ and the received power P at the antenna 120 １ and the minimum received power P required at the target terminal 30. ２ Based on this, the target terminal 30 receives the radio wave reflected by the reflector 100 at a minimum reception power P ２ The maximum distance r between the reflector 100 and the target terminal 30 that can be received ２ Therefore, the maximum distance r ２ The position of the target terminal 30 relative to the reflector 100 can be set by taking into consideration the maximum distance r ２ Taking this into consideration, the position of the reflector 100 relative to the target terminal 30 can be set, and the location where the reflector 100 is installed can be determined depending on the position of the target terminal 30.

[0169] Furthermore, the control unit 5 determines whether the distance between the reflector 100 and the target terminal 30 is the maximum distance r ２ Therefore, the maximum distance r ２ Based on this, it can be determined whether the positional relationship between the reflector 100 and the target terminal 30 is appropriate.

[0170] Furthermore, the reflector 100 has a plurality of cells 110, and the control unit 5 electrically controls the amount of phase change that changes the phase of the radio waves in each of the plurality of cells 110, so that the amount of phase change in the reflector 100 can be changed to any value among continuous values, and the amount of phase change can be controlled in a multi-value manner.

[0171] The reflector 100 has a plurality of cells 110, and the control unit 5 sets the reflection phase of each of the plurality of cells 110 to one of two values. Therefore, by controlling the amount of phase change in a binary manner, it is possible to adjust the reflection angle to an angle other than specular reflection.

[0172] Since the difference between the first value and the second value is 120 degrees to 240 degrees, the reflection angle can be adjusted to an angle other than specular reflection by controlling the amount of phase change in a binary manner, taking into account variations due to manufacturing errors, etc.

[0173] Furthermore, since the radio waves are Sub-6 or millimeter wave band radio waves, it is possible to provide a radio wave transmission system 10 that can efficiently supply power to a receiving terminal when reflecting radio waves in frequency bands such as the fifth generation mobile communication system (5G) or Sub-6.

[0174] The radio wave transmission method is a radio wave transmission system including a reflector 100 capable of scanning the reflection direction, a control unit 5 that controls the reflection direction of the reflector 100, an antenna 120 that is installed at a fixed position relative to the reflector 100 and can receive radio waves reflected by the reflector 100, and a memory 5A, in which the control unit 5 adjusts the reflection direction of the reflector 100 so that the received power at the antenna 120 is increased, and stores in the memory 5A an incident phase distribution obtained based on a total phase distribution that represents the distribution of phase changes that the reflector 100 imparts to incident waves, obtained in the adjusted state, and a first reflection phase distribution that is determined by the positional relationship between the antenna 120 and the reflector 100, and calculates a target total phase distribution realized by the incident phase distribution and a second reflection phase distribution that corresponds to the positional relationship between the reflector 100 and a target terminal that is located in a predetermined reflection direction relative to the reflector 100.

[0175] In this way, since the radio wave transmission method can determine the incident phase distribution, the target total phase distribution can be easily determined by simply combining the reflected phase distribution, which can be calculated based on the positional relationship between the reflector 100 and the target terminal 30, with the incident phase distribution.

[0176] Therefore, it is possible to provide a radio wave transmission method that allows the incident direction and reflection direction of the reflector 100 to be easily adjusted.

[0177] The above describes exemplary radio wave transmission systems and radio wave transmission methods of the present disclosure, but the present disclosure is not limited to the specifically disclosed embodiments, and various modifications and variations are possible without departing from the scope of the claims.

[0178] This international application claims priority based on Japanese Patent Application No. 2022-176904, filed on November 4, 2022, the entire contents of which are incorporated herein by reference.

[0179] REFERENCE SIGNS LIST 1 Wall 1A Antenna U1, U2, U3 Receiving terminal 4 Communication unit 4A Antenna 5 Control unit 5A Memory (an example of a storage unit) 10 Radio wave transmission system 20 Wave source 30 Target terminal 30 100 Reflector 110 Cell (an example of a reflector) 111 Resonant element 111A End edge 112, 112H, 112V Resonant element 112A, 112B Linear element 112C PIN diode 120 Antenna 125 Stay 130 Power meter 135 Cable

Claims

1. A reflector capable of scanning in a reflection direction, A control unit that controls the reflection direction of the reflector, An antenna installed at a fixed position with respect to the reflector and capable of receiving radio waves reflected by the reflector, A storage unit Including, The control unit, Adjusts the reflection direction of the reflector so that the received power in the antenna increases, Stores in the storage unit the incident phase distribution obtained based on the total phase distribution representing the distribution of the amount of phase change given by the reflector to the incident wave and the first reflection phase distribution determined by the positional relationship between the antenna and the reflector in the adjusted state, A radio wave transmission system that obtains a target total phase distribution realized by a second reflection phase distribution corresponding to the positional relationship between a target terminal located in a predetermined reflection direction with respect to the reflector and the reflector and the incident phase distribution.

2. The radio wave transmission system according to claim 1, wherein the antenna is detachable from a fixing portion that fixes the antenna with respect to the reflector.

3. The radio wave transmission system according to claim 1, wherein the antenna is located on the normal line of the reflection surface of the reflector.

4. The control unit adjusts the reflection direction by controlling the total phase distribution of the reflector so that the received power in the antenna increases, and obtains the total phase distribution at which the received power in the antenna is maximized, according to any one of claims 1 to 3. The radio wave transmission system described in the item.

5. The control unit is based on the radiated power of a wave source that radiates or reflects the radio wave, the distance between the wave source and the reflector, the distance between the reflector and the antenna, the received power in the antenna, and the minimum required received power at the target terminal. The radio wave transmission system according to any one of claims 1 to 3, which obtains the maximum distance between the reflector and the target terminal at which the target terminal can receive the radio wave reflected by the reflector with the minimum received power.

6. The radio wave transmission system according to claim 5, wherein the control unit determines whether the distance between the reflector and the target terminal is equal to or less than the maximum distance.

7. The reflector has a plurality of reflecting portions, The control unit electrically controls the amount of phase change that changes the phase of the radio wave in each of the plurality of reflecting portions, according to any one of claims 1 to 3. The radio wave transmission system described in the item.

8. The reflector has a plurality of reflecting portions, The radio wave transmission system according to any one of claims 1 to 3, wherein the control unit sets the reflection phase of each of the plurality of reflection units to either a first value or a second value.

9. The radio wave transmission system according to claim 8, wherein the difference between the first value and the second value is 120 degrees to 240 degrees.

10. The radio wave transmission system according to any one of claims 1 to 3, wherein the radio wave is a Sub-6 or millimeter wave band radio wave.

11. A reflector capable of scanning the reflection direction, A control unit that controls the reflection direction of the reflector, An antenna installed at a position fixed to the reflector and capable of receiving radio waves reflected by the reflector, A storage unit In a radio wave transmission system including: The control unit Adjusts the reflection direction of the reflector so that the received power in the antenna increases, Stores in the storage unit the incident phase distribution obtained based on the total phase distribution representing the distribution of the amount of phase change given by the reflector to the incident wave and the first reflection phase distribution determined by the positional relationship between the antenna and the reflector, obtained in the adjusted state. A radio wave transmission method for obtaining a target total phase distribution realized by a second reflection phase distribution corresponding to the positional relationship between a target terminal located in a predetermined reflection direction with respect to the reflector and the reflector and the incident phase distribution.