Radio wave reflection device

Abstract

This radio wave reflection device comprises a radio wave reflection region that includes a plurality of reflection elements and in which the reflection angle of a radio wave and a first direction in which the radio wave is reflected are controlled by voltage applied to the plurality of reflection elements. The radio wave reflection region has a plurality of reflection element groups obtained by division along the first direction. The plurality of reflection element groups are disposed side by side in a second direction intersecting the first direction. A target reflection angle at which the radio wave is reflected is set for a reflection element group disposed at an intermediate position among the plurality of reflection element groups. The voltage is applied to the plurality of reflection elements such that the amount of change in the radio wave reflection angle set for two reflection element groups adjacent to each other increases from the reflection element group disposed at the intermediate position toward the reflection element groups disposed at both ends in the second direction.

Description

radio wave reflector

[0001] One embodiment of the present invention relates to a radio wave reflector capable of controlling the direction of propagation of reflected radio waves.

[0002] A phased array antenna device controls the directivity of radio waves while the antenna is fixed by adjusting the amplitude and phase of the high-frequency signal applied to each of the multiple antenna elements arranged in a planar manner. A phased array antenna device requires a phase shifter. A phased array antenna device using a phase shifter that utilizes the change in dielectric constant due to the orientation state of liquid crystal has been disclosed (see, for example, Patent Document 1).

[0003] Japanese Patent Application Publication No. 11-103201

[0004] Radio waves reflected by a phased array antenna system form a main lobe that is reflected in the desired angular direction and side lobes that are reflected in directions other than the main lobe. In a phased array antenna system, an increase in such side lobes can degrade the communication quality on the receiving end.

[0005] In view of these problems, one of the objectives of one embodiment of the present invention is to improve the communication quality using a radio wave reflector.

[0006] A radio wave reflector according to one embodiment of the present invention includes a plurality of reflecting elements and a radio wave reflection region that controls a first direction for reflecting radio waves and the reflection angle of radio waves by a voltage applied to the plurality of reflecting elements. The radio wave reflection region has a plurality of groups of reflecting elements divided along the first direction, and the plurality of groups of reflecting elements are arranged in a second direction intersecting the first direction. A target reflection angle for reflecting radio waves is set for the group of reflecting elements located in the middle of the plurality of groups of reflecting elements, and a voltage is applied to each of the plurality of reflecting elements such that the amount of change in the reflection angle of radio waves set for two adjacent groups of reflecting elements increases as one moves from the group of reflecting elements located in the middle toward the groups of reflecting elements located at both ends in the second direction.

[0007] This is a schematic deployed perspective view of a radio wave reflector according to one embodiment of the present invention. This is a circuit diagram of the reflecting unit. This is a plan view of a reflecting element used in a radio wave reflector according to one embodiment of the present invention. This is a diagram showing the cross-sectional structure between A1 and A2 in the plan view of the reflecting element shown in Figure 3. This is a diagram schematically showing how the propagation direction of reflected waves changes due to the radio wave reflector according to one embodiment of the present invention. This is a diagram showing the relationship between the angle at which radio waves are reflected by the reflecting element and the phase difference. This is a diagram explaining a method for deriving the phase difference from the angle at which radio waves are reflected by the reflecting element. This is a diagram explaining a group of reflecting elements in the radio wave reflection region. This is a diagram showing the reflection angle and phase difference of radio waves in the group of reflecting elements. This is a plan view of a radio wave reflector according to one embodiment of the present invention. This is a diagram showing the relationship between the position of the group of reflecting elements and the reflection angle of radio waves. This is a diagram showing the in-plane distribution of phase in the radio wave reflection region of a radio wave reflector according to one embodiment of the present invention. This is a diagram showing the in-plane distribution of phase in the radio wave reflection region of a conventional radio wave reflector. This is a diagram showing the relationship between the reflection angle and the reflection amplitude of radio waves. This is an end view of the reflecting unit. This is a diagram explaining a group of reflecting elements in the radio wave reflection region. This is a diagram showing the change in the reflection angle and phase of radio waves in the group of reflecting elements. This is a diagram explaining a group of reflecting elements in the radio wave reflection region. This diagram shows the change in the reflection angle and phase of radio waves in a group of reflective elements. This diagram shows the change in the reflection angle and phase of radio waves in a conventional radio wave reflection region.

[0008] The embodiments of the present invention will be described below with reference to the drawings and other materials. However, the present invention can be implemented in various forms without departing from its spirit, and is not to be interpreted as being limited to the embodiments described below.

[0009] While drawings may schematically represent the width, thickness, shape, etc., of each part to clarify the explanation, they are merely examples and do not limit the interpretation of the present invention. In this specification and in each drawing, elements having the same function as those described in previously shown drawings are denoted by the same reference numerals, and redundant explanations may be omitted.

[0010] In this specification, ordinal numbers are assigned for convenience to distinguish elements and do not indicate priority or order. Furthermore, the ordinal numbers used in this specification and drawings may differ from those described in the claims.

[0011] In this specification and its claims, when describing a configuration in which one structure is placed on top of another structure, unless otherwise specified, the term "on top of" includes both cases: one in which the other structure is placed directly on top of the other structure so as to be in contact with it, and another in which the other structure is placed above the other structure via yet another structure.

[0012] In this specification, expressions such as "α includes A, B, or C," "α includes any one of A, B, and C," and "α includes one selected from the group consisting of A, B, and C" do not exclude cases where α includes multiple combinations of A to C unless otherwise specified. Furthermore, these expressions do not exclude cases where α includes other elements.

[0013] 1. Overview of the Radio Wave Reflector The configuration of a radio wave reflector, one embodiment of the present invention, will be described below. The radio wave reflector 100 can control the direction of reflection and the reflection angle of radio waves using a metasurface. A metasurface is a type of artificial medium (metamaterial) that achieves arbitrary dielectric constant and permeability by periodically arranging structures that are small relative to the wavelength, and is an artificial surface with a two-dimensional periodic arrangement of structures. A metasurface has the characteristic of being able to control the reflection phase of radio waves incident on its surface. The radio wave reflector 100 is a so-called liquid crystal metasurface reflector, and is a device that exhibits the function of reflecting irradiated radio waves in an arbitrary direction by utilizing the change in dielectric constant caused by the change in orientation of the liquid crystal layer due to an electric field. Note that a radio wave reflector is also called an IRS (Intelligent Reflecting Surface), etc.

[0014] Figure 1 is a schematic exploded perspective view of a radio wave reflector 100 according to one embodiment of the present invention. In Figure 1, a first direction D1, a second direction D2 perpendicular to the first direction D1, and a third direction D3 perpendicular to the first direction D1 and the second direction D2 are shown. The radio wave reflector 100 has a radio wave reflection region RA provided on an array substrate 102 and a frame region FA surrounding the radio wave reflection region RA. Multiple reflection unit cells 160 are arranged in the first direction D1 and the second direction D2 within the radio wave reflection region RA. In the radio wave reflection region RA, incident radio waves can be reflected in any direction and angle using the reflection unit cells 160. The reflection unit cell 160 has a reflection element 140 and a switching element (not shown) electrically connected to the reflection element 140.

[0015] The reflective element 140 includes at least a driving electrode 142, a common electrode 152, and a liquid crystal layer (not shown) provided between the driving electrode 142 and the common electrode 152. The liquid crystal layer is sealed by a sealing material 154 provided between the array substrate 102 and the opposing substrate 104. The switching element and the driving electrode 142 are provided on the array substrate 102 side, and the common electrode 152 is provided on the opposing substrate 104 side.

[0016] A drive circuit (scan line drive circuit 106, signal line drive circuit 108) for driving the reflective unit cell 160 is provided in the frame region FA of the array substrate 102. A plurality of wirings (not shown) are further provided on the array substrate 102. The wirings electrically connect the drive circuits to the switching elements of the reflective unit cell 160, and at least a portion of them extends to the edge of the array substrate 102. The wirings are exposed at the edge of the array substrate 102 and form a plurality of terminal portions 110. A flexible printed circuit (FPC) substrate (not shown) is connected to the terminal portions 110. Various drive signals for driving the radio wave reflector 100 are supplied from an external circuit via the flexible printed circuit and the terminal portions 110, and based on these signals, the drive circuit generates a control signal for controlling the reflective unit cell 160 and supplies it to the reflective unit cell 160. Alternatively, the scan line drive circuit 106 and / or the signal line drive circuit 108 may be omitted, and control signals may be supplied directly from an external circuit to the reflection unit cell 160 via wiring.

[0017] 2. Circuit Diagram of the Reflective Unit Cell Figure 2 is a circuit diagram of the reflective unit cell 160. The reflective unit cell 160 is driven by a reflective element 140 and a switching element 120 electrically connected to the reflective element 140. The gate of the switching element 120 is connected to the scan line 117, the source is connected to the signal line 118, and the drain is connected to the drive electrode 142 of the reflective element 140. The scan line 117 and the signal line 118 are connected to the scan line drive circuit 106 and the signal line drive circuit 108, respectively, as shown in Figure 1. The switching (on and off) of the switching element is controlled by a scan signal applied to the scan line 117. When the switching element is turned on, the drive electrode 142 (see Figure 1) conducts with the signal line 118 and a control signal is applied. The switching element 120 is formed, for example, from a thin-film transistor. With this configuration, multiple drive electrodes 142 arranged in the first direction D1 can be selected row by row, and control signals with different voltage levels can be applied to each row.

[0018] 3. Configuration of the Reflecting Element Next, the configuration of the reflecting element 140 will be described with reference to Figures 3 to 6B. Note that the switching element 120 is not shown in Figures 3 to 6B. Figure 3 is a plan view of the reflecting element 140 used in the radio wave reflecting device 100 according to one embodiment of the present invention, as seen from above (the side into which the radio waves are incident). Figure 4 is a diagram showing the cross-sectional structure between A1 and A2 in the plan view of the reflecting element shown in Figure 3.

[0019] Figures 3 and 4 describe the case where radio waves are incident on the liquid crystal layer from the array substrate 102 side. As a reflecting element 140, the array substrate 102 can be considered as a dielectric layer forming a single layer. Therefore, the array substrate 102 is sometimes referred to as a dielectric layer. The driving electrode 142 is provided on the array substrate 102, and the common electrode 152 is provided on the opposing substrate 104. A first alignment film 144 is provided on the array substrate 102 so as to cover the driving electrode 142. A second alignment film 148 is provided on the opposing substrate 104 so as to cover the common electrode 152. The driving electrode 142 and the common electrode 152 are arranged facing each other, and a liquid crystal layer 146 is provided between them.

[0020] The drive electrode 142 functions as a patch electrode. Preferably, the shape of the drive electrode 142 is rotationally symmetric with respect to its center O. For example, the shape of the drive electrode 142 may be four-fold rotationally symmetric, having a square or rhombus shape in plan view. As a four-fold rotationally symmetric shape, it may be a quadrilateral with chamfered vertices or a quadrilateral with rounded vertices. Alternatively, the shape of the drive electrode 142 may be circular. Figure 3 shows the case where the drive electrode 142 is square in plan view. By having rotationally symmetric with respect to the center of the drive electrode 142, the anisotropy of the reflection of radio waves with respect to the vertical and horizontal polarization of the incident radio waves can be reduced. That is, the bias of vertical and horizontal polarization with respect to the planes of the first direction D1 and the second direction D2 in Figure 3 can be suppressed, and the vertical and horizontal polarizations can be reflected uniformly. There are no particular limitations on the shape of the common electrode 152; it has a shape that extends over substantially the entire surface of the opposing substrate 104, having a larger area than the driving electrode 142.

[0021] The reflective unit cell 160 functions as a reflector that reflects radio waves in a predetermined direction. Therefore, it is preferable that the reflective element 140 be configured so that the amplitude of the reflected radio waves is attenuated as little as possible. As is clear from the structure shown in Figure 4, when radio waves propagating in the air are reflected by the reflective element 140, the radio waves pass through the array substrate 102 twice. The array substrate 102 is preferably made of a dielectric material such as glass or resin.

[0022] The array substrate 102 and the opposing substrate 104 are arranged opposite each other with a gap between them. The liquid crystal layer 146 is provided to fill the area surrounded by the sealing material 154 (see Figure 1). The gap between the array substrate 102 and the opposing substrate 104 is 20 μm to 100 μm, for example, a gap of 75 μm. A driving electrode 142, a common electrode 152, a first alignment film 144, and a second alignment film 148 are provided between the array substrate 102 and the opposing substrate 104. Therefore, the gap between the first alignment film 144 and the second alignment film 148 provided on each of the array substrate 102 and the opposing substrate 104 becomes the thickness of the liquid crystal layer 146. Although not shown in Figure 4, a spacer may be provided between the array substrate 102 and the opposing substrate 104 to maintain a constant distance.

[0023] A control signal is applied to the drive electrode 142 to control the orientation of the liquid crystal molecules in the liquid crystal layer 146. The control signal is a DC voltage signal, or a polarity reversal signal in which positive DC voltage and negative DC voltage alternately reverse. A voltage at an intermediate level between ground and the polarity reversal signal is applied to the common electrode 152. When the control signal is applied to the drive electrode 142, the orientation state of the liquid crystal molecules contained in the liquid crystal layer 146 changes. A liquid crystal material with dielectric anisotropy is used for the liquid crystal layer 146. For example, nematic liquid crystal, smectic liquid crystal, cholestic liquid crystal, or discotic liquid crystal can be used as the liquid crystal layer 146. In a liquid crystal layer 146 with dielectric anisotropy, the dielectric constant changes with changes in the orientation state of the liquid crystal molecules. The reflecting element 140 can change the dielectric constant of the liquid crystal layer 146 by the control signal applied to the drive electrode 142. This allows the phase of the reflected wave to be delayed when reflecting radio waves.

[0024] There are no restrictions on the frequency band of radio waves reflected by the reflecting element 140; it may be the very high frequency (VHF), ultra-high frequency (UHF), super high frequency (SHF), submillimeter wave (THF), or extra high frequency (EHF) bands. Note that millimeter waves refer to the frequency band from 30 GHz to 300 GHz. In the fifth-generation communication standard known as 5G, the 26 GHz to 29 GHz band is also included, and frequencies above 26 GHz are sometimes collectively referred to as millimeter waves. For example, the radio wave reflector 100 can be used to reflect radio waves in the 400 MHz to 6.0 GHz band, the 2.5 GHz to 4.7 GHz band, and the 24 GHz to 50 GHz band. The liquid crystal molecules in the liquid crystal layer 146 change orientation in response to a control signal applied to the drive electrode 142, but they hardly follow the frequency of the radio waves incident on the drive electrode 142. Therefore, the reflector element 140 can control the phase of the reflected radio waves without being affected by the radio waves.

[0025] In the cross-sectional structure of the reflective element 140 shown in Figure 4, when the first alignment film 144 and the second alignment film 148 are horizontal alignment films, the long axes of the liquid crystal molecules are aligned horizontally with respect to the surfaces of the drive electrode 142 and the common electrode 152 by the first alignment film 144 and the second alignment film 148 when no control signal (voltage signal) is applied (also called the first state). When a control signal (voltage signal) is applied to the drive electrode 142 (also called the second state), the liquid crystal molecules are affected by the electric field and their long axes are aligned perpendicular to the surfaces of the drive electrode 142 and the common electrode 152. The angle at which the long axes of the liquid crystal molecules are aligned can also be adjusted to an intermediate direction between the horizontal and vertical directions, depending on the magnitude of the control signal applied to the drive electrode 142 (the magnitude of the voltage between the ground electrode and the patch electrode).

[0026] When liquid crystal molecules have positive dielectric anisotropy, the dielectric constant is higher in the second state than in the first state. Conversely, when liquid crystal molecules have negative dielectric anisotropy, the apparent dielectric constant is lower in the second state than in the first state. The liquid crystal layer 146 with dielectric anisotropy can also be considered a variable dielectric layer. The reflecting element 140 can control the phase of the reflected wave by delaying (or not delaying) it by utilizing the dielectric anisotropy of the liquid crystal layer 146.

[0027] Figure 5 schematically illustrates how the direction of propagation of a reflected wave changes due to two adjacent reflecting elements 140. The two reflecting elements 140 are adjacent in the first direction D1. That is, the two adjacent driving electrodes 142 are connected to different signal lines. When radio waves are incident on the two adjacent reflecting elements 140 with the same phase, different control signals (voltage V1 ≠ V2) are applied to the two adjacent reflecting elements 140, resulting in a larger phase change of the reflected wave due to one reflecting element 140 compared to the other. As a result, the phase of the reflected wave R1 reflected by one reflecting element 140 is different from the phase of the reflected wave R2 reflected by the other reflecting element 140 (in Figure 5, the phase of reflected wave R2 is ahead of the phase of reflected wave R1), and the direction of propagation of the reflected wave appears to change diagonally.

[0028] Figure 6A shows the relationship between the angle at which radio waves are reflected by the reflecting element 140 and the phase difference. Figure 6B shows how to derive the phase difference from the angle at which radio waves are reflected by the reflecting element 140. Figure 6A shows how radio waves are reflected by the surfaces of two adjacent reflecting elements 140. Here, let d be the pitch between the two adjacent reflecting elements 140, and let ΔΦ be the phase difference of the reflected waves. As shown in Figure 6A, it is assumed that the angle at which radio waves are reflected when no voltage is applied to the reflecting element 140 is perpendicular to the surface of the reflecting element 140 (θ = 0°). θ is the reflection angle of the radio waves reflected by the reflecting element 140. For the reflection angle θ of the radio waves, the right side is considered positive and the left side is considered negative, with the angle of the radio waves when no voltage is applied to the reflecting element 140 as the reference. The angle between the radio waves reflected by the reflecting element 140 and the wavefront of the radio waves is assumed to be right-angle. In this case, the phase difference ΔΦ can be expressed by a trigonometric function between the two adjacent reflecting elements. Although the detailed derivation method of the phase difference ΔΦ is omitted here, the phase difference ΔΦ can be expressed by the following equation (1), where d is the pitch of two adjacent reflecting elements, θ is the reflection angle of the radio wave, and λ is the wavelength.

[0029]

[0030] 4. Figure 19, a diagram of the configuration of a conventional radio wave reflection region RA, is a plan view illustrating the phase difference in a conventional radio wave reflection region RA. In Figure 19, the direction in which radio waves are reflected is assumed to be the first direction D1 (horizontal direction). As shown in Figure 19, the radio wave reflection region RA has multiple reflective elements 240 provided in the first direction D1 and the second direction D2. In Figure 19, in the radio wave reflection region RA, the reflection angles of radio waves in the second direction D2 are all the same, and the phase difference is 0°. The diagram shows how the phase change in the radio wave reflection region RA repeats from 0° to 360° along the direction in which radio waves are reflected.

[0031] As shown in FIG. 19, when the phase difference is 0° in a direction intersecting the direction in which radio waves are reflected, side lobes indicating radio waves radiated in a direction other than the main lobe indicating the direction in which radio waves are radiated tend to increase with respect to the main lobe. In a radio wave reflection device, an increase in side lobes may deteriorate the communication quality on the receiving side.

[0032] Therefore, in one embodiment of the present invention, one of the purposes is to reduce side lobes in the radio wave reflection device 100 to improve communication quality.

[0033] 5. Structure of Radio Wave Reflection Region RA In one embodiment of the present invention, the radio wave reflection region RA is divided into a plurality of reflection element groups along the same direction as the direction in which radio waves are reflected. Then, in each of the plurality of reflection element groups, the voltage applied to each of the plurality of reflection elements 140 is set so that the reflection angles of the reflected radio waves are different.

[0034] FIG. 7 is a plan view of the radio wave reflection device 100. The radio wave reflection region RA includes a plurality of reflection elements 140, and controls the direction in which radio waves are reflected and the reflection angle of the radio waves by the voltage applied to each of the plurality of reflection elements 140. The voltage applied to each of the plurality of reflection elements 140 is set based on the phase difference of the reflection element 140 set according to the angle at which radio waves are reflected by the above-described formula (1).

[0035] In FIG. 7, the direction in which radio waves are reflected corresponds to the first direction D1 (horizontal direction). The radio wave reflection region RA is divided into a plurality of reflection element groups 150a to 150e along the same direction (first direction D1) as the direction in which radio waves are reflected. In the present embodiment, the case where the number of the plurality of divided radio wave element groups in the radio wave reflection region RA is five will be described, but the number of the plurality of divided radio wave element groups is not particularly limited. In FIG. 6, the plurality of reflection element groups 150a to 150e are arranged side by side in a direction (second direction D2) intersecting the direction in which radio waves are reflected. In this specification and the like, the direction in which radio waves are reflected may be defined as the first direction, and the direction intersecting the direction in which radio waves are reflected may be defined as the second direction.

[0036] As shown in FIG. 7, in each of the plurality of reflection element groups 150a to 150e, a plurality of reflection elements 140 are arranged along the first direction D1 and the second direction D2. Also, the number 140 of the plurality of reflection elements included in each of the plurality of reflection element groups 150a to 150e is the same. In the reflection element groups 150a to 150e, the number of reflection elements 140 arranged along the first direction D1 is larger than the number of reflection elements 140 arranged along the second direction D2.

[0037] FIG. 8 is a schematic diagram showing the distribution of the phase difference with respect to the reflection angle of radio waves in the radio wave reflection region RA. In FIG. 8, as in the radio wave reflection region RA shown in FIG. 7, a plurality of reflection element groups 150a to 150e are provided. In the present embodiment, a voltage is applied to each of the plurality of reflection elements 140 so that the relationship between the position in the direction intersecting the direction in which the radio waves of the plurality of reflection element groups 150a to 150e are reflected and the reflection angle of the radio waves set for each of the plurality of reflection element groups 150a to 150e becomes non-linear. The position in the direction intersecting the direction in which the radio waves of the plurality of reflection element groups are reflected corresponds to the order from the reflection element group located at one end of the plurality of reflection element groups to the reflection element group located at the other end. In FIG. 8, the position of the reflection element group 150c corresponds to 0, and the position of the reflection element group 150e corresponds to 4. Also, a target reflection angle for reflecting radio waves with respect to the reflection element group 150a arranged in the middle among the plurality of reflection element groups 150a to 150e is set, and from the reflection element group 150a arranged in the middle, as going toward the reflection element groups 150c and 150e arranged at both ends in the second direction, a voltage is applied to each of the plurality of reflection elements 140 so that the amount of change in the reflection angle of the radio waves set for two adjacent reflection element groups increases.

[0038] In Figure 8, for example, the reflection angle θr of the target at the intermediate reflector group 150a is set to 45°. The reflection angles of radio waves at the reflector groups 150b and 150d adjacent to reflector group 150a are set to θr-a and θr+a, respectively. The reflection angles of radio waves at the reflector groups 150c and 150e adjacent to reflector groups 150b and 150d are set to θr-b and θr+b, respectively. The change in the reflection angle of radio waves between reflector group 150a and the mutually adjacent reflector groups 150b and 150d is angle a. The change in the reflection angle of radio waves between reflector groups 150b and 150d and the mutually adjacent reflector groups 150c and 150e is angle (b-a). In this case, the relationship between angle a and angle b is expressed as (b-a) > a. In this way, by setting the amount of change in the reflection angle of radio waves to increase for each of the multiple reflecting element groups 150a to 150e, it is possible to adjust the magnitude of the phase difference between two adjacent reflecting elements in the multiple reflecting elements of each reflecting element group 150a to 150e. For example, if θr = -45, then a = 1 and b = 3 should be set.

[0039] At this time, the phase difference ΔΦ of the reflected waves from two adjacent reflecting elements among the multiple reflecting elements 140 of the reflecting element group 150a to 150e is expressed by the above-mentioned equation (1), where d is the pitch of the two adjacent reflecting elements, θ is the reflection angle of the radio wave, and λ is the wavelength.

[0040] As shown in Figure 8, among the multiple reflector groups 150a to 150e, the intermediate reflector group 150a is set to a target reflection angle θr for reflecting radio waves. The reflection angles of the radio waves of the reflector groups 150b and 150d adjacent to reflector group 150a are gradually decreased. As will be explained in detail later, according to equation (1) above, the phase difference of the reflected waves from two adjacent reflectors in the intermediate reflector group 150a is smaller than the phase difference of the reflected waves from two adjacent reflectors in reflector groups 150b and 150c. Furthermore, the reflection angles of the radio waves of the reflector groups 150b and 150e adjacent to reflector group 150a are gradually increased. According to equation (1) above, the phase difference of the reflected waves from two adjacent reflectors in the intermediate reflector group 150a is larger than the phase difference of the reflected waves from two adjacent reflectors in reflector groups 150d and 150e.

[0041] Next, the relationship between the radio wave reflection angle set for each group of reflective elements 150a to 150e in the radio wave reflection region RA and the phase difference of the reflected waves of two adjacent reflective elements will be explained in more detail with reference to Figures 9 to 13. In Figures 9 to 13, the case in which multiple reflective elements 140 arranged in a single row are treated as one group of reflective elements 150 will be explained.

[0042] Figure 9 is a plan view of the radio wave reflector 100. An example in which the multiple reflecting elements 140 are arranged in a 24x24 grid in the radio wave reflection region RA will be described. The other configurations of the radio wave reflector 100 are the same as in Figure 1.

[0043] In Figure 9, the direction in which radio waves are reflected corresponds to the first direction D1 (horizontal direction). The radio wave reflection region RA is divided into 24 reflective element groups 150-0 to 150-23 along the same direction as the direction in which radio waves are reflected (first direction D1). The 24 reflective element groups 150-0 to 150-23 are arranged in a direction (second direction D2) that intersects or is perpendicular to the direction in which radio waves are reflected. In Figure 9, the position of reflective element group 150-0 corresponds to 0, and the position of reflective element group 150-23 corresponds to 23.

[0044] In the 24 reflective element groups 150-0 to 150-23, the reflection angle of radio waves at the intermediate reflective element groups 150-11 and 150-12 is set to 45°, which is the target reflection angle. Then, the reflection angles of radio waves for each reflective element group 150-0 to 150-23 are set so that the reflection angle of radio waves increases or decreases as you move away from the intermediate reflective element groups 150-11 and 150-12.

[0045] Figure 10 shows the relationship between the position [row] of the reflective element group in the second direction D2 and the reflection angle θ [°] of the radio waves. In the radio wave reflection region RA shown in Figure 10, the reflective element groups 150-11 and 150-12 in the 11th and 12th rows correspond to the reflective element groups placed in the middle. Therefore, the reflective element groups 150-11 and 150-12 in the 11th and 12th rows are set to the target reflection angle θr for reflecting radio waves. As you move from the reflective element groups 150-11 and 150-12 placed in the middle toward the reflective element groups 150-0 and 150-23 placed at both ends in the second direction D2, the amount of change in the radio wave reflection angle set for two adjacent reflective element groups increases.

[0046] In Figure 10, the change between the reflection angle of the radio waves set in the reflective element group 150-23 located at one end of the reflective element groups 150-0 and 150-23 located at both ends and the reflection angle of the target is +10°, and the change between the reflection angle of the radio waves set in the reflective element group 150-0 located at the other end and the reflection angle of the target is -10°. The present embodiment is not limited thereto, and the change between the reflection angle θ of the target and the reflective element groups 150-0 and 150-23 located at both ends may be θ = ±20° or less, or ±30° or less.

[0047] As shown in Figure 10, for the reflective element groups 150-0 to 150-11 from row 0 to row 11, the relationship between the row of the reflective element group and the reflection angle of the radio wave can be approximated by Equation 2: y = a(x - p) ２ +q...Formula (2)

[0048] Furthermore, for the reflective element groups 150-12 to 150-23 from row 12 to row 23, the relationship between the row of the reflective element group and the reflection angle of the radio wave can be approximated by equation 3: y = -a(x - p) ２ +q...Formula (3)

[0049] Here, a = 0.0755, p = 11.5, and q = 45. Here, q is related to the reflection angle of the target, and a and q are determined according to the number of reflective elements provided in the radio wave reflection region RA and the range of the radio wave reflection angle.

[0050] As shown in Figure 10, the relationship between the position of the reflector group 150-0 to 150-23 in the second direction (the row of the reflector group in Figure 10) and the reflection angle of the radio waves is nonlinear.

[0051] Figure 11 is a table showing the phase difference based on the position of the reflecting elements and the reflection angle of the radio waves in a radio wave reflector 100 according to one embodiment of the present invention. The phase difference Φ at each reflecting element 140 is calculated by the above-described equation (1). θry is the reflection angle of the radio waves set for each group of reflecting elements. The pitch d of the reflecting elements was set to 3.7 mm and λ = 10.71 mm, and the phase difference ΔΦ between two adjacent reflecting elements in the first direction D1 was calculated. The wavelength λ was calculated as electromagnetic wave propagation speed / frequency = (299792458 m / s) / (28 GHz) = 10.71 mm.

[0052] As shown in Figure 11, the phase difference of reflected waves from two adjacent reflecting elements in the intermediate reflecting element groups 150-11 and 150-12 is smaller than the phase difference of reflected waves from two adjacent reflecting elements in reflecting element group 150-0 located at one end, and larger than the phase difference of reflected waves from two adjacent reflecting elements in reflecting element group 150-23 located at the other end. As shown in Figure 11, focusing on the three reflecting elements 140 arranged in the 0th, 1st, and 2nd columns in the first row of the radio wave reflection region RA, the phase difference of the reflected wave from the 1st column reflecting element relative to the 0th column reflecting element is -102°, and the phase difference of the reflected wave from the 2nd column reflecting element relative to the 1st column reflecting element is -102°. In other words, the phase difference of reflected waves from two adjacent reflecting elements 140 in the first direction D1 of the reflecting element group 150a is -102°. Similarly, in row 11, the phase difference between the reflected waves of two adjacent reflecting elements 140 is -88°, and in row 23, the phase difference between two adjacent reflecting elements 140 is -72°. If the phase difference Φ given to a reflecting element exceeds 360°, it is set to (Φ - 360)° to have periodicity. For example, in Figure 11, the reflecting element in row 0 x column 12 is given a phase difference of -309°, and the adjacent reflecting element in row 0 x column 11 would normally be given a phase difference of -411°, but based on the aforementioned periodicity, a phase difference of -51° is given.

[0053] In this case, the voltage applied to each reflecting element 140 is controlled based on the phase difference of the reflected wave. There is a proportional relationship where the larger the voltage applied to the reflecting element 140, the larger the phase of the reflected wave. Therefore, the magnitude of the voltage set for each reflecting element 140 should be set based on the position of the reflecting element and its phase difference as shown in Figure 11. In Figure 11, when viewing the radio wave reflection region RA from the vertical and reflecting radio waves to the right, the phase difference increases from column 0 to column 23. In this case, the voltage applied to the reflecting element 140 increases as the phase difference increases. Also, when viewing the radio wave reflection region RA from the vertical and reflecting radio waves to the right, the phase difference decreases from column 0 to column 23. In this case, the voltage applied to the reflecting element 140 decreases as the phase difference decreases.

[0054] Table 1 sets the radio wave reflection angles of the reflection element groups 150-0, 150-5, 150-11, 150-17, and 150-23 to -35°, -42.7°, -45°, -48.2°, and -55°, respectively.

[0055]

[0056] The phase difference dP between elements in Table 1 ３５ , dP ４２．７ , dP ４５ , dP ４８．２ , dP ５５ satisfies the relationship dP ３５ < dP ４２．７ < dP ４５ < dP ４８．２ < dP ５５ Also, the relationship between the voltage differences dV between elements in Table 1 ３５ , dV ４２．７ , dV ４５ , dV ４８．２ , dV ５５ satisfies the relationship dV ３５ < dV ４２．７ < dV ４５ < dV ４８．２ < dV ５５

[0057] FIG. 12 is a table showing the positions of the reflection elements in the conventional radio wave reflection device 100 and the phase difference based on the radio wave reflection angle. The points that the radio wave reflection region RA has 24 rows × 24 columns of reflection elements 140, the pitch d of the reflection elements is 3.7 mm, and the frequency is 28 GHz (λ = 10.71 mm) are the same as in FIG. 11. The difference from FIG. 11 is that the radio wave reflection angles of the reflection elements in the direction intersecting the direction of reflecting the radio wave are the same. Under the above conditions, using the above formula (1), the phase difference ΔΦ between two adjacent reflection elements in the first direction D1 was calculated.

[0058] Based on the in-plane distribution of the phase settings shown in FIGS. 11 and 12, a simulation of the radio wave reflection angle and reflection intensity was performed. This simulation was performed using SIMULIA CST Studio Suite (manufactured by Dassault Systèmes).

[0059] Figure 13 shows the simulation results of the reflection angle and reflection intensity of radio waves for a radio wave reflector according to one embodiment of the present invention (see Example 1) and a conventional radio wave reflector (see Comparative Example 1). The X-axis represents the radio wave reflection angle θ, and the Y-axis represents the reflection intensity [dB]. In Figure 13, the peak of the reflection intensity at θ = -45 [deg] represents the main lobe, and the peaks of the reflection intensity at values ​​other than θ = -45 [deg] represent the side lobes. As shown in Figure 13, it was confirmed that the radio wave reflector according to one embodiment of the present invention reduces the side lobes compared to a conventional radio wave reflector.

[0060] As in Comparative Example 1, when the phase difference is 0° in the direction of reflection and the direction of intersection, the reflection direction for each line in the intersection direction becomes the same, so the main lobe and side lobes increase uniformly as a composite wave of all lines. In contrast, as in Example 1, by allowing a range of reflection angles in the intersection direction, the peak positions of both the main lobe and side lobes for each line are dispersed, so it is considered that the composite wave of all lines in this case is reduced compared to Comparative Example 1.

[0061] As described above, the radio wave reflector according to one embodiment of the present invention can reduce side lobes compared to conventional radio wave reflectors. This makes it possible to improve the communication quality of the radio wave reflector 100.

[0062] 6. End Face Structure of Reflective Unit Cell Figure 14 illustrates the end face structure of the reflective unit cell 160. In Figure 14, radio waves are incident from the array substrate 102 side. Therefore, in the reflective element 140, the driving electrode 142 functions as a patch electrode.

[0063] Each reflective element 140 is connected to an element circuit that includes at least one switching element 120. Each element circuit may include multiple transistors and may further include one or more capacitive elements. The element circuits including the switching elements 120 and the reflective elements 140 are provided on the array substrate 102 via an undercoat 112, either directly or in any configuration. The transistors included in the element circuit are not restricted in their structure and may be bottom-gate or top-gate transistors. Alternatively, the transistors may be dual-gate transistors having gate electrodes above and below a semiconductor film. The transistor illustrated in Figure 14 is a bottom-gate transistor and consists of a gate electrode 122, a gate insulating film 124 on the gate electrode 122, a semiconductor film 126 on the gate insulating film 124, and a pair of electrodes 128 and 130 on the semiconductor film 126. A planarization film 116 is provided on the switching element 120, and the reflective elements 140 are formed on it. As an optional configuration, interlayer insulating films 114 and 119 may be provided between the switching element 120 and the planarization film 116, or on the planarization film 116, respectively.

[0064] The drive electrode 142 of the reflective element 140 is electrically connected to the switching element 120 via an opening provided in the interlayer insulating film 114 or the planarization film 116. Various signals supplied from an external circuit are input to the terminal portion 110 and supplied to the reflective element 140 directly or via the drive circuit through wiring. As shown in Figure 14, a wiring pattern 134 is formed in the frame region FA. The wiring pattern 134 includes a plurality of wires. Although not shown in Figure 14, at least a portion of the wiring pattern 134 is connected to the terminal portion 110, and at least a portion of the wiring pattern 134 extends over the frame region FA. The wiring pattern 134 may be in the same layer as the gate electrode 122, or in the same layer as the electrodes 128 and 130. Alternatively, a portion of the wiring pattern 134 may be in the same layer as the gate electrode 122, and another portion may be in the same layer as the electrodes 128 and 130.

[0065] The gate electrode 122, gate insulating film 124, semiconductor film 126, electrodes 128 and 130, interlayer insulating films 114 and 119 and planarization film 116 covering the switching element 120, wiring pattern 134, and terminal portion 110 that constitute the switching element 120 can be formed using known materials and known methods as appropriate, so a detailed explanation will be omitted. Briefly, the gate electrode 122, electrodes 128 and 130, wiring pattern 134, and terminal portion 110 are formed by forming a film containing metals such as tantalum, molybdenum, titanium, and aluminum using sputtering or chemical vapor deposition (CVD), and then appropriately patterning it using a photolithography process. The semiconductor film 126 is formed as a film containing a group 14 element, such as silicon, or as a film containing an oxide of a group 13 element such as indium or gallium. The semiconductor film 126 can also be formed by applying sputtering or CVD. The gate insulating film 124, interlayer insulating films 114 and 119, undercoat 112, and overcoat 132 contain inorganic compounds such as silicon-containing inorganic compounds like silicon oxide and silicon nitride, and are formed by sputtering or CVD. The planarization film 116 contains polymers such as acrylic resin, epoxy resin, polyimide, polyamide, and silicon resin, and can be formed using wet film formation methods such as spin coating, inkjet printing, or printing as appropriate. By providing the planarization film 116, a reflective element 140 can be formed on a flat surface.

[0066] The driving electrode 142 of the reflective element 140 may include, for example, a metal such as copper, aluminum, tungsten, molybdenum, or titanium, or an alloy containing at least one of these metals. Alternatively, the driving electrode 142 may include a light-transmitting conductive oxide such as indium-zinc oxide (IZO) or indium-tin oxide (ITO). The driving electrode 142 may have a single-layer structure or a laminated structure in which layers of different compositions are stacked. For example, a laminated structure of a layer containing a conductive oxide and a layer containing the above-mentioned metal or alloy may be adopted. Alternatively, in order to impart light transmittance to the driving electrode 142 containing the metal or alloy, the driving electrode 142 may have a mesh shape.

[0067] The first alignment film 144, provided on multiple drive electrodes 142, is provided to control the orientation of liquid crystal molecules constituting the liquid crystal layer 146 provided thereon. The first alignment film 144 can be provided continuously across multiple reflective elements 140. In other words, the first alignment film 144 can be provided so as to be shared by all reflective elements 140 without being interrupted between adjacent reflective elements 140.

[0068] The first orientation film 144 contains a polymer such as polyimide or polyester. The first orientation film 144 is formed using a wet film formation method such as inkjet, spin coating, printing, or dip coating, and its surface is rubbed. Alternatively, the first orientation film 144 may be formed by photo-alignment treatment.

[0069] The liquid crystal layer 146 is sealed between the array substrate 102 and the opposing substrate 104 by a sealing material 154. The structure of the liquid crystal molecules contained in the liquid crystal layer 146 is not limited. Therefore, the liquid crystal molecules may be nematic liquid crystals, smectic liquid crystals, cholesteric liquid crystals, or chiral smectic liquid crystals. The thickness of the liquid crystal layer 146 is, for example, 10 μm or more and 100 μm or less, preferably 20 μm or more and 60 μm or less. Although not shown in the figures, spacers may be provided within the liquid crystal layer 146 to maintain this thickness throughout the entire radio wave reflector 100. However, if the above-described thickness of the liquid crystal layer 146 is adopted in a liquid crystal display device, it will be impossible to obtain the high responsiveness necessary to display moving images, and it will be extremely difficult to exhibit the function of a liquid crystal display device.

[0070] The second alignment film 148 is also provided to control the orientation of liquid crystal molecules and has the same configuration as the first alignment film 144. The second alignment film 148 can also be formed to extend continuously across adjacent reflective elements 140 and be shared by multiple reflective elements 140. The first alignment film 144 and the second alignment film 148 are arranged such that the direction in which the first alignment film 144 orients the liquid crystal molecules is parallel to that of the second alignment film 148. The liquid crystal molecules are oriented in a certain direction by the first alignment film 144 and the second alignment film 148.

[0071] The common electrode 152 is provided so as to overlap with the multiple reflecting elements 140. As described above, radio waves are incident from the array substrate 102 side. For this reason, it is preferable that the driving electrode 142 has a highly symmetrical shape such as a regular polygon or a circle in order to efficiently reflect both orthogonal components of the radio waves (vertical polarization and horizontal polarization). The size of the driving electrode 142 can be appropriately adjusted according to the wavelength of the radio waves to be reflected; for example, the length in the row direction and the length in the column direction can be appropriately selected from a range of 1 mm to 40 mm. A constant potential (common potential) is supplied to the common electrode 152 directly from an external circuit or via the signal line driving circuit 108.

[0072] Similar to the driving electrode 142, the common electrode 152 may also contain metals such as copper, aluminum, tungsten, molybdenum, or titanium, alloys containing at least one of these metals, or conductive oxides such as ITO or IZO. The common electrode 152 may have a single-layer structure or a laminated structure in which layers of different compositions are stacked. The common electrode 152 may also be formed by applying methods such as sputtering or CVD. The reflective element 140 may or may not transmit visible light. For example, visible light may be blocked by using a metal or alloy with a thickness that does not transmit visible light for the driving electrode 142 and the common electrode 152.

[0073] In the radio wave reflector 100, as described above, the first alignment layer 144 and the second alignment layer 148 are parallel in the direction in which they orient the liquid crystal molecules. Therefore, when no potential difference is applied between the driving electrode 142 and the common electrode 152, no longitudinal electric field is generated within the liquid crystal layer 146, and the liquid crystal molecules orient horizontally. The orientation of the liquid crystal layer 146 is the same between the reflecting elements 140, and therefore the dielectric constant is also constant within the liquid crystal layer 146, so the spread (phase) of the reflected wave generated when radio waves incident from the driving electrode 142 side are reflected off the surface of the driving electrode 142 does not change. As a result, the incident radio waves are specularly reflected by the radio wave reflector 100, and the reflected wave is given at the same exit angle as the incident angle.

[0074] In contrast, by controlling the voltage applied to the driving electrode 142 using an element circuit to create a potential difference between the driving electrode 142 and the common electrode 152, the generated longitudinal electric field causes the liquid crystal molecules to stand up and align vertically. At this time, if longitudinal electric fields of different intensities are generated between the reflecting elements 140, the dielectric constant of the liquid crystal layer 146 changes between the reflecting elements 140 according to the intensity of the longitudinal electric field. As a result, the phase of the reflected wave changes, and consequently, the reflection direction of the radio waves incident on the radio wave reflection region RA can be changed. The reflection direction can be arbitrarily controlled by changing the intensity of the longitudinal electric field formed on the reflecting elements 140.

[0075] Figures 1 to 14 illustrate the configuration of the radio wave reflector 100 when radio waves are incident from the array substrate 102 side, but the device is not limited to this configuration. The radio wave reflector 100 may also be configured when radio waves are incident from the opposing substrate 104 side. In this case, a common electrode that functions as a patch electrode can be provided on the opposing substrate 104 side.

[0076] 7. Reflecting Radio Waves in the Vertical Direction Next, we will explain the case where radio waves are reflected in the vertical direction within the radio wave reflection region RA. Figure 15 is a schematic plan view of the radio wave reflection region RA. In the radio wave reflection region RA, the direction in which radio waves are reflected corresponds to the second direction D2 (vertical direction). The radio wave reflection region RA is divided into a plurality of reflective element groups 150a to 150e along the same direction as the direction in which radio waves are reflected (second direction D2).

[0077] As shown in Figure 15, each of the multiple reflective element groups 150a to 150e has multiple reflective elements 140 arranged along a first direction D1 and a second direction D2. Also, the number of multiple reflective elements 140 in each of the multiple reflective element groups 150a to 150e is the same. In the reflective element groups 150a to 150e, the number of reflective elements 140 arranged along the second direction D2 is greater than the number of reflective elements 140 arranged along the first direction D1.

[0078] Figure 16 is a schematic diagram showing the distribution of phase difference with respect to the reflection angle of radio waves in the radio wave reflection region RA. In Figure 16, similar to the radio wave reflection region RA shown in Figure 15, a plurality of reflective element groups 150a to 150e are provided. A voltage is applied to each of the plurality of reflective elements 140 such that the relationship between the position of the plurality of reflective element groups 150a to 150e in a direction intersecting the direction in which the radio waves are reflected and the reflection angle of the radio waves set for each of the plurality of reflective element groups 150a to 150e is nonlinear. Here, the direction intersecting the direction in which the plurality of reflective element groups reflect the radio waves corresponds to the first direction D1.

[0079] In Figure 16, among the multiple reflector groups 150a to 150e, the reflector group 150a, which is positioned in the middle, is set to the target reflection angle θr. The reflection angles of radio waves in the reflector groups 150b and 150d adjacent to reflector group 150a are set to θr-a and θr+a, respectively. The reflection angles of radio waves in the reflector groups 150c and 150e adjacent to reflector groups 150b and 150d, respectively, are set to θr-b and θr+b. The change in the reflection angle of radio waves between reflector group 150a and the mutually adjacent reflector groups 150b and 150d is angle a. The change in the reflection angle of radio waves between reflector groups 150b and 150d and the mutually adjacent reflector groups 150c and 150e is angle (b-a). In this case, the relationship between angle a and angle b is expressed as (b-a) > a. In this way, by setting the amount of change in the reflection angle of radio waves to increase for each of the multiple reflecting element groups 150a to 150e, it is possible to adjust the magnitude of the phase difference between two adjacent reflecting elements in the multiple reflecting elements of each reflecting element group 150a to 150e.

[0080] At this time, the phase difference ΔΦ of the reflected waves from two adjacent reflecting elements among the multiple reflecting elements 140 of the reflecting element group 150a to 150e is expressed by the above-mentioned equation (1), where d is the pitch of the two adjacent reflecting elements, θ is the reflection angle of the radio wave, and λ is the wavelength.

[0081] As shown in Figure 15, among the multiple reflector groups 150a to 150e, the reflector group 150a positioned in the middle is set to the target reflection angle θr for reflecting radio waves. The reflection angles of radio waves of the reflector groups 150b and 150d adjacent to reflector group 150a are reduced. According to equation (1), the phase difference of the reflected waves from two adjacent reflectors in the intermediate reflector group 150a is smaller than the phase difference of the reflected waves from two adjacent reflectors in reflector groups 150b and 150c. Alternatively, the reflection angles of radio waves of the reflector groups 150b and 150e adjacent to reflector group 150a are increased. According to equation (1), the phase difference of the reflected waves from two adjacent reflectors in the intermediate reflector group 150a is larger than the phase difference of the reflected waves from two adjacent reflectors in reflector groups 150d and 150e.

[0082] 8. Reflecting Radio Waves at an Oblique Direction The case of reflecting radio waves at an oblique direction in the radio wave reflection region RA will be explained. Here, the oblique direction refers to the fourth direction D4 that intersects the first direction D1 and the second direction D2 on the same plane. Figure 17 is a schematic plan view of the radio wave reflection region RA. In the radio wave reflection region RA, the direction in which radio waves are reflected corresponds to the fourth direction D4 (vertical direction). The radio wave reflection region RA is divided into multiple groups of reflective elements 150a to 150e along the same direction as the direction in which radio waves are reflected (fourth direction D4). As shown in Figure 17, the number of reflective elements in the group of reflective elements located in the middle is greater than the number of reflective elements in the groups of reflective elements located at both ends.

[0083] Figure 18 is a schematic diagram showing the distribution of phase difference with respect to the reflection angle of radio waves in the radio wave reflection region RA. In Figure 18, similar to the radio wave reflection region RA shown in Figure 17, a plurality of reflective element groups 150a to 150e are provided. A voltage is applied to each of the plurality of reflective elements 140 such that the relationship between the position of the plurality of reflective element groups 150a to 150e in the direction intersecting the direction in which the radio waves are reflected and the reflection angle of the radio waves set for each of the plurality of reflective element groups 150a to 150e is nonlinear. Here, the direction intersecting the direction in which the plurality of reflective element groups reflect the radio waves corresponds to the fifth direction D5.

[0084] In Figure 18, among the multiple reflector groups 150a to 150e, the reflector group 150a, which is positioned in the middle, is set to the target reflection angle θr. The reflection angles of radio waves in the reflector groups 150b and 150d adjacent to reflector group 150a are set to θr-a and θr+a, respectively. The reflection angles of radio waves in the reflector groups 150c and 150e adjacent to reflector groups 150b and 150d, respectively, are set to θr-b and θr+b. The change in the reflection angle of radio waves between reflector group 150a and the mutually adjacent reflector groups 150b and 150d is angle a. The change in the reflection angle of radio waves between reflector groups 150b and 150d and the mutually adjacent reflector groups 150c and 150e is angle (b-a). In this case, the relationship between angle a and angle b is expressed as (b-a) > a. In this way, by setting the amount of change in the reflection angle of radio waves to increase for each of the multiple reflecting element groups 150a to 150e, it is possible to adjust the magnitude of the phase difference between two adjacent reflecting elements in the multiple reflecting elements of each reflecting element group 150a to 150e.

[0085] At this time, the phase difference ΔΦ of the reflected waves from two adjacent reflecting elements among the multiple reflecting elements 140 of the reflecting element group 150a to 150e is expressed by the above-mentioned equation (1), where d is the pitch of the two adjacent reflecting elements, θ is the reflection angle of the radio wave, and λ is the wavelength.

[0086] As shown in Figure 18, among the multiple reflector groups 150a to 150e, the reflector group 150a positioned in the middle is set to the target reflection angle θr for reflecting radio waves. The reflection angles of radio waves of the reflector groups 150b and 150d adjacent to reflector group 150a are reduced. According to equation (1) above, the phase difference of the reflected waves from two adjacent reflectors in the intermediate reflector group 150a is smaller than the phase difference of the reflected waves from two adjacent reflectors in reflector groups 150b and 150c. Alternatively, the reflection angles of radio waves of the reflector groups 150b and 150e adjacent to reflector group 150a are increased. According to equation (1) above, the phase difference of the reflected waves from two adjacent reflectors in the intermediate reflector group 150a is larger than the phase difference of the reflected waves from two adjacent reflectors in reflector groups 150d and 150e.

[0087] Figures 15 and 17 illustrate an example in which the reflective elements 140 provided in each reflective element group 150 are arranged in a direction that reflects radio waves and in a direction intersecting the direction that reflects radio waves. However, the reflective elements 140 provided in each reflective element group 150 may also be arranged only in the direction that reflects radio waves.

[0088] Figure 17 illustrates the case where the number of reflective elements in the intermediate reflective element group is greater than the number of reflective elements in the reflective element groups at both ends. However, the number of reflective elements in the intermediate reflective element group may be less than the number of reflective elements in the reflective elements at both ends. For example, in the radio wave reflection region RA shown in Figures 7 and 15, the number of rows or columns of reflective elements 140 in the intermediate reflective element group 150a may be less than the number of rows or columns of reflective elements 140 in the reflective element groups 150c and 150e at both ends.

[0089] The embodiments described above as examples of the present invention can be combined and implemented as appropriate, insofar as they do not contradict each other. Furthermore, any additions, deletions, or design modifications of components, or additions, omissions, or changes to processes based on the reflective elements or radio wave reflectors of each embodiment, made by those skilled in the art, are also included within the scope of the present invention, as long as they retain the essence of the present invention.

[0090] Any effects or benefits other than those brought about by the embodiments described above, if they are clear from the description herein or easily predictable to a person skilled in the art, are naturally considered to be brought about by the present invention.

[0091] 100: Radio wave reflector, 102: Array substrate, 104: Opposing substrate, 106: Scan line drive circuit, 108: Signal line drive circuit, 110: Terminal section, 114: Interlayer insulating film, 116: Planarization film, 117: Scan line, 118: Signal line, 119: Interlayer insulating film, 120: Switching element, 122: Gate electrode, 124: Gate insulating film, 126: Semiconductor film, 128: Electrode, 130: Electrode, 132: Overcoat, 134: Wiring pattern, 136: Undercoat, 140 : Reflecting element, 142: Driving electrode, 144: First alignment layer, 146: Liquid crystal layer, 148: Second alignment layer, 150a: Reflecting element group, 150b: Reflecting element group, 150c: Reflecting element group, 150d: Reflecting element group, 150e: Reflecting element group, 152: Common electrode, 154: Encapsulating material, 160: Reflecting unit cell, D1: First direction, D2: Second direction, D3: Third direction, FA: Frame region, FPC: Flexible printed circuit, O: Center, R1: Reflected wave, R2: Reflected wave, RA: Radio wave reflection region

Claims

1. A radio wave reflecting device comprising a plurality of reflecting elements and a radio wave reflection region that controls a first direction for reflecting radio waves and the reflection angle of the radio waves by a voltage applied to the plurality of reflecting elements, wherein the radio wave reflection region has a plurality of groups of reflecting elements divided along the first direction, the plurality of groups of reflecting elements are arranged in a second direction intersecting the first direction, a target reflection angle for reflecting the radio waves is set for a group of reflecting elements located in the middle of the plurality of groups of reflecting elements, and a voltage is applied to each of the plurality of reflecting elements such that the amount of change in the reflection angle of the radio waves set for two adjacent groups of reflecting elements increases as one moves from the group of reflecting elements located in the middle toward the groups of reflecting elements located at both ends in the second direction.

2. The radio wave reflecting device according to claim 1, wherein the change in the reflection angle of radio waves set at one end of the reflecting element group arranged at both ends and the reflection angle of the target is +10°, and the change in the reflection angle of radio waves set at the other end and the reflection angle of the target is -10°.

3. The radio wave reflector according to claim 2, wherein the phase difference of reflected waves from two adjacent reflecting elements in the intermediate group of reflecting elements is smaller than the phase difference of reflected waves from two adjacent reflecting elements in the group of reflecting elements located at one end, and larger than the phase difference of reflected waves from two adjacent reflecting elements in the group of reflecting elements located at the other end.

4. The radio wave reflector according to claim 1, wherein each of the plurality of reflecting element groups has the same number of reflecting elements.

5. The radio wave reflecting device according to claim 1, wherein the plurality of reflecting elements having each of the plurality of reflecting element groups are arranged in the first direction.

6. The radio wave reflecting device according to claim 1, wherein the plurality of reflecting elements having each of the plurality of reflecting element groups are arranged in the first direction and the second direction.

7. The radio wave reflector according to claim 1, wherein the number of reflecting elements in the intermediate group of reflecting elements is greater than the number of reflecting elements in the groups of reflecting elements located at both ends.

8. The radio wave reflector according to claim 2, wherein the number of reflecting elements in the intermediate group of reflecting elements is smaller than the number of reflecting elements in the multiple reflecting elements arranged at both ends.

9. The radio wave reflecting device according to claim 1, wherein each of the plurality of reflecting elements has a patch electrode, a common electrode, and a liquid crystal layer provided between the patch electrode and the common electrode.

10. The radio wave reflector according to claim 9, wherein a switching element is connected to the patch electrode.

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