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 a 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. The voltage is applied to the plurality of reflection elements such that the phase differences of reflected waves by two reflection elements adjacent in the first direction are mutually different, and the phase differences of reflected waves by two reflection elements adjacent in the second direction are 0° in the plurality of reflection element groups.

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] A phased array antenna system can reflect radio waves not only at one reflection angle but also at multiple reflection angles. However, when radio waves are reflected at multiple reflection angles, the full width at half maximum (FWHM) of each beam broadens. Thus, when radio waves are reflected at multiple reflection angles, there is a problem in that controlling the FWHM of the beam becomes difficult.

[0005] In view of these problems, one of the objectives of one embodiment of the present invention is to improve the controllability of the beam when reflecting radio waves at multiple reflection angles using a radio wave reflector.

[0006] A radio wave reflection device according to one embodiment of the present invention includes a plurality of reflective 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 reflective elements. The radio wave reflection region has a plurality of groups of reflective elements divided along the first direction, and the plurality of groups of reflective elements are arranged in a second direction intersecting the first direction. A voltage is applied to each of the plurality of reflective elements such that the phase difference of the reflected waves from two adjacent reflective elements in the first direction is different from that of the plurality of reflective elements, and the phase difference of the reflected waves from two adjacent reflective elements in the second direction is 0°.

[0007] Figure 1 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 reflection unit. This is a plan view of a reflective 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 reflective element shown in Figure 3. This is a diagram schematically showing how the propagation direction of reflected waves changes due to a 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 reflective 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 reflective element. This is a plan view 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 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 radio wave reflection angle and the received intensity. This is a diagram showing the relationship between the radio wave reflection angle and the received intensity. This is an end view of the reflection unit. This is a diagram explaining the group of reflective elements in the radio wave reflection region. 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 explaining the group of reflective elements in the radio wave reflection region. 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 diagram illustrates a group of reflective elements in the radio wave reflection region. This is an example of the voltage applied to each reflective element. This is another example of the voltage applied to each reflective element. This diagram shows the relationship between the radio wave reflection angle and the received signal strength. This diagram shows the change in the radio wave reflection angle and phase 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, 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: when one structure is placed directly on top of another structure so as to be in contact with it, and when another structure is placed above another 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 reflection unit cell 160 functions as a reflector that reflects radio waves in a predetermined direction. Therefore, it is preferable that the reflection element 140 is configured such that the amplitude of the reflected radio wave is not attenuated as much as possible. As is clear from the structure shown in FIG. 4, when radio waves propagating in the air are reflected by the reflection element 140, the radio waves pass through the array substrate 102 twice. The array substrate 102 is preferably formed of a dielectric material such as glass or resin.

[0022] The array substrate 102 and the counter substrate 104 are arranged to face each other with a gap therebetween. The liquid crystal layer 146 is provided so as to fill the region surrounded by the sealing material 154 (see FIG. 1). The gap between the array substrate 102 and the counter substrate 104 is 20 μm to 100 μm, and for example, has a gap of 75 μm. Between the array substrate 102 and the counter substrate 104, drive electrodes 142, common electrodes 152, a first alignment film 144, and a second alignment film 148 are provided. 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 counter substrate 104 becomes the thickness of the liquid crystal layer 146. Although not shown in FIG. 4, spacers for maintaining a constant interval may be provided between the array substrate 102 and the counter substrate 104.

[0023] A control signal for controlling the alignment of the liquid crystal molecules in the liquid crystal layer 146 is applied to the drive electrode 142. The control signal is a direct current voltage signal or a polarity inversion signal in which a positive direct current voltage and a negative direct current voltage alternately invert. A voltage at ground or an intermediate level of the polarity inversion signal is applied to the common electrode 152. When a control signal is applied to the drive electrode 142, the alignment state of the liquid crystal molecules contained in the liquid crystal layer 146 changes. A liquid crystal material having dielectric anisotropy is used for the liquid crystal layer 146. For example, nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal, or discotic liquid crystal is used as the liquid crystal layer 146. The liquid crystal layer 146 having dielectric anisotropy changes its dielectric constant due to a change in the alignment state of the liquid crystal molecules. The reflection element 140 can change the dielectric constant of the liquid crystal layer 146 by the control signal applied to the drive electrode 142. Thereby, when reflecting radio waves, the phase of the reflected wave can be delayed.

[0024] There is no limitation on the frequency band of the radio wave reflected by the reflection element 140, and it may be in the very high frequency (VHF) band, ultra-high frequency (UHF) band, super high frequency (SHF) band, sub-millimeter wave (THF), millimeter wave (EHF) band. The millimeter wave refers to the frequency band of 30 GHz to 300 GHz. In the fifth-generation communication standard called 5G, it also includes the 26 GHz band to 29 GHz band, and in some cases, the frequencies of 26 GHz and above are collectively called millimeter waves. For example, the radio wave reflection device 100 can be used for the reflection of radio waves in the 400 MHz to 6.0 GHz band, 2.5 GHz to 4.7 GHz band, and 24 GHz to 50 GHz band. The liquid crystal molecules of the liquid crystal layer 146 change their orientation in response to the control signal applied to the drive electrode 142, but hardly follow the frequency of the radio wave incident on the drive electrode 142. Therefore, the reflection element 140 can control the phase of the reflected radio wave without being affected by the radio wave.

[0025] In the cross-sectional structure of the reflection element 140 shown in FIG. 4, when the first alignment film 144 and the second alignment film 148 are horizontal alignment films, in a state where no control signal (voltage signal) is applied (also referred to as the first state), the long axes of the liquid crystal molecules are horizontally aligned 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. In a state where a control signal (voltage signal) is applied to the drive electrode 142 (also referred to as the second state), the liquid crystal molecules are affected by the electric field and the long axes are vertically aligned with respect 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 made to be in an intermediate direction between the horizontal direction and the vertical direction 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 20 of the configuration diagram of the conventional radio wave reflection region RA is a plan view illustrating the phase difference in the conventional radio wave reflection region RA. In Figure 20, the direction in which radio waves are reflected is assumed to be the first direction D1 (horizontal direction). As shown in Figure 20, the radio wave reflection region RA has a plurality of reflective elements 240 provided in the first direction D1 and the second direction D2.

[0031] In a conventional radio wave reflection region RA, as shown in Figure 20, when radio waves are reflected in two directions in the horizontal direction, each region where radio waves are reflected is divided into reflecting element groups 250a and 250b along the second direction D2 (vertical direction). Here, in reflecting element group 250a, the radio wave reflection angle θ １ With the angle set to -45°, the reflective element group 250b reflects the radio wave at the reflection angle θ. ２ Let's explain the case where the angle is 45°.

[0032] As shown in Figure 20, when the radio wave reflection region RA is reflected in two directions horizontally, the half-width of the peak of the normalized received intensity at θ = -45° is 9° (not shown). On the other hand, when the radio wave is reflected in only one direction horizontally at θ = -45° within the radio wave reflection region RA, the half-width of the peak of the normalized received intensity at θ = -45° is 4° (not shown).

[0033] Thus, in the radio wave reflection region RA, when radio waves are reflected at multiple reflection angles, the half-width of each beam tends to broaden compared to when radio waves are reflected in only one direction. Therefore, when radio waves are reflected at multiple reflection angles, there is a problem in that beam control becomes difficult.

[0034] Therefore, one of the objectives of one embodiment of the present invention is to improve the controllability of the beam when it is reflected by multiple reflecting elements using the radio wave reflector 100.

[0035] 5. Configuration of the Radio Wave Reflection Region RA In one embodiment of the present invention, the radio wave reflection region RA is divided into a plurality of reflective element groups along the same direction as the direction in which the radio waves are reflected. Then, in each of the plurality of reflective element groups, the voltage applied to each of the plurality of reflective elements 140 is set so that the reflection angle of the reflected radio waves differs.

[0036] Figure 7 is a plan view of the radio wave reflector 100. The radio wave reflection region RA includes a plurality of reflecting elements 140, and the direction and angle of reflection of radio waves are controlled by the voltage applied to the plurality of reflecting elements 140. The voltage applied to each of the plurality of reflecting elements 140 is set based on the phase difference of the reflecting elements 140, which is set according to the angle at which the radio waves are reflected, as shown in equation (1) above. An example in which the plurality of reflecting elements 140 are arranged in a 46x46 arrangement 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.

[0037] In Figure 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 reflective element groups 150a and 150b along the same direction as the direction in which radio waves are reflected (first direction D1). In this embodiment, the case in which there are two plurality of radio wave element groups divided in the radio wave reflection region RA is described, but the number of plurality of radio wave element groups divided is not particularly limited. In Figure 7, the plurality of reflective element groups 150a and 150b are arranged in a direction intersecting the direction in which radio waves are reflected (second direction D2). Note that in this specification, 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.

[0038] In Figure 7, each of the multiple reflective element groups 150a and 150b has multiple reflective elements 140 arranged along the first direction D1 and the second direction D2. In each of the multiple reflective element groups 150a and 150b, the number of multiple reflective elements 140 arranged in the first direction D1 is greater than the number of multiple reflective elements 140 arranged in the second direction D2. In Figure 7, the number of multiple reflective elements 140 in each of the multiple reflective element groups 150a and 150b is the same. An example is shown where reflective element group 150a has multiple reflective elements 140 arranged in 23 rows (rows 0 to 22) x 46 columns, and reflective element group 150b has multiple reflective elements 140 arranged in 23 rows (rows 23 to 45) x 46 columns. Furthermore, the reflective element group 150a reflects radio waves at -45° along the first direction D1, and the reflective element group 150b reflects radio waves at +45° along the first direction.

[0039] Figure 8 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 formula (1). In the reflecting element group 150a, θ = -45° is set, and in the reflecting element group 150b, θ = 45°. The pitch d of the reflecting elements is set to 1.9 mm and λ = 6.35 mm, and the phase difference ΔΦ between two adjacent reflecting elements in the first direction D1 is calculated. The wavelength λ was calculated as electromagnetic wave propagation speed / frequency = (299792458 m / s) / (47.2 GHz) = 6.35 mm.

[0040] As shown in Figure 8, focusing on the three reflective elements 140 arranged in the 0th, 1st, and 2nd rows in the first direction D1 of the reflective element group 150a, the phase difference of the reflected wave of the 1st row reflective element relative to the 0th row reflective element is -76°, and the phase difference of the reflected wave of the 2nd row reflective element relative to the 1st row reflective element is -76°. In other words, the phase difference of the reflected waves of two adjacent reflective elements 140 in the first direction D1 of the reflective element group 150a is -76°. Similarly, the phase difference of the reflected waves of two adjacent reflective elements 140 in the first direction D1 of the reflective element group 150b is 76°. In the two reflective element groups 150a and 150b, the phase differences of the reflected waves of two adjacent reflective elements in the first direction D1 are different. Furthermore, in each of the reflecting element groups 150a and 150b, the phase difference between the reflected waves of two adjacent reflecting elements in the second direction D2 is 0°.

[0041] 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 8. The voltage applied to each reflecting element 140 should be set so that the voltage increases from 0° to -360° depending on the reflection angle θ. For example, the reflecting element 140 in the first row x first column is supplied with a voltage corresponding to -88°, and the reflecting element 140 in the first row x second column is supplied with a voltage corresponding to -164°. If the phase difference Φ applied to the reflecting element exceeds 360°, it is set to have periodicity as (Φ - 360)°. For example, in Figure 8, the reflective element in the 1st row x 22nd column is given a phase difference of -322°, and the adjacent reflective element in the 1st row x 23rd column would normally be given a phase difference of -398°, but based on the aforementioned periodicity, a phase difference of -38° is given.

[0042] Furthermore, it is preferable that the absolute value of the average value of the phase difference between two adjacent reflective elements in the middle of a plurality of reflective elements aligned in the first direction D1 of the reflective element group 150a is the same as the absolute value of the average value of the phase difference between two adjacent reflective elements in the middle of a plurality of reflective elements aligned in the first direction D1 of the reflective element group 150b. For example, in Figure 8, the phase difference in the middle of the reflective element group 150a in the first direction D1 corresponds to the phase difference of the 22.5th column between the 22nd and 23rd columns in rows 0 to 22. Also, the phase difference located in the middle of the reflective element group 150b in the first direction D1 corresponds to the phase value of the 22.5th column between the 22nd and 23rd columns in rows 23 to 46. At this time, the phase difference of the 22.5th row of the reflective element group 150a is -180°, which is the average of the phase difference of the reflective element 140 in the 22nd row (-322°) and the phase difference of the reflective element 140 in the 23rd row (-38°). Similarly, the phase difference of the 22.5th row of the reflective element group 150b is -180°, which is the average of the phase difference of the reflective element 140 in the 22nd row (-38°) and the phase difference of the reflective element 140 in the 23rd row (-322°). Thus, in Figure 8, the absolute value of the average of the phase differences of two adjacent reflective elements in the middle of a plurality of reflective elements aligned in the first direction D1 of the reflective element group 150a is the same as the absolute value of the average of the phase differences of two adjacent reflective elements in the middle of a plurality of reflective elements aligned in the first direction D1 of the reflective element group 150b. In other words, when the reflective elements 140 of the reflective element group 150 are arranged in even rows or even columns, assuming a reflective element 140 between two adjacent reflective elements 140 located in the middle of the first direction D1 of the reflective element group 150a, and using the assumed reflective element 140 as a reference (phase difference of 0°), the phase difference between the two reflective elements adjacent to the assumed reflective element 140 is preferably within ±90°, and more preferably within ±45°. In Figure 8, the reflective elements 140 of the reflective element group 150a are in columns 0 to 45, and assuming a reflective element in the 22.5th column, which is in the middle of the first direction D1 of the reflective element group 150a, the phase difference of the reflective element in the 22nd column is -38°, and the phase difference of the reflective element in the 23rd column is -322°.In other words, using the midpoint of the reflective element group 150a and reflective element group 150b in the first direction D1 as a reference, the phase difference between adjacent reflective elements relative to the midpoint is ±38°, satisfying the condition of being within ±45°. This makes it possible to suppress deterioration of the reflection intensity distribution of the reflective element group 150a and reflective element group 150b.

[0043] Figure 9 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 conventional radio wave reflector 100. Similar to Figure 8, the radio wave reflection region RA is provided with 46 rows x 46 columns of reflecting elements 140, the pitch d of the reflecting elements is 1.9 mm, and the frequency is 47.2 GHz (λ = 6.35 mm). The difference from Figure 8 is that the radio wave reflection region RA is divided into two groups of reflecting elements along a direction intersecting the direction of radio wave reflection (second direction D2) (see Figure 20). In Figure 20, in each of the multiple reflecting element groups 250a and 250b, the number of multiple reflecting elements 240 aligned in the second direction D2 is greater than the number of multiple reflecting elements 240 aligned in the first direction D1. Under the above conditions, the phase difference ΔΦ between two adjacent reflecting elements in the first direction D1 was calculated using the equation (1) described above. As shown in Figure 9, the phase difference between two adjacent reflective elements 140 in the first direction D1 of the reflective element group 150a is -76°, and the phase difference between two adjacent reflective elements 140 in the first direction of the reflective element group 150b is 76°. The two reflective element groups 150a and 150b have different phase differences in the first direction D1.

[0044] Based on the in-plane distribution of phase settings shown in Figures 8 and 9, the reflection angle and reflection intensity of radio waves were calculated.

[0045] Figure 10 shows the simulation results of the radio wave reflection angle and reflection intensity of a radio wave reflector 100 according to one embodiment of the present invention. Figure 11 shows the simulation results of the radio wave reflection angle and reflection intensity of a conventional radio wave reflector. The X-axis represents the radio wave reception angle θ [deg], and the Y-axis represents the normalized reception intensity [dB]. In Figures 10 and 11, a peak in reflection intensity was observed at θ = ±45°. In Figure 11, the full width at half maximum (FWHM) of the peak reflection intensity at θ = ±45° was confirmed to be 9°, whereas in Figure 10, the FWHM of the peak reflection intensity at θ = ±45° was confirmed to be 4°.

[0046] In the radio wave reflector 100, the direction of radio waves can be controlled by applying a phase difference to the reflecting elements 140 in the direction in which the radio waves are reflected. In this case, by making the number of reflecting elements arranged in the direction in which the radio waves are reflected greater than the number of reflecting elements arranged in the direction intersecting the direction in which the radio waves are reflected, the full width at half maximum of the peak of the reflection intensity can be reduced. In conventional radio wave reflectors, the reflecting elements are divided into two groups along the direction intersecting the direction in which the radio waves are reflected (second direction D2). For example, if 46 rows x 46 columns of reflecting elements 140 are arranged in the radio wave reflection region RA, and the direction in which the radio waves are reflected is the first direction D1, the reflecting elements are divided into reflecting elements 140 from columns 0 to 22 and reflecting elements 140 from columns 23 to 45. In contrast, in the radio wave reflector 100 according to one embodiment of the present invention, the reflecting elements are divided into two groups along the direction in which the radio waves are reflected. For example, if a 46x46 array of reflective elements 140 is arranged in the radio wave reflection region RA, and the direction of radio wave reflection is the first direction D1, then the array is divided into two groups: reflective elements 140 from row 0 to row 22 and reflective elements 140 from row 23 to row 45. Compared with conventional radio wave reflection devices, the radio wave reflection device 100 according to one embodiment of the present invention has a larger number of reflective elements arranged in the direction of radio wave reflection within each group of reflective elements. This makes it possible to reduce the half-width of the peak reflection intensity.

[0047] As described above, the radio wave reflector 100 according to one embodiment of the present invention can narrow the half-width of the peak reflection intensity compared to conventional radio wave reflectors. This improves the controllability when the radio wave reflector 100 reflects a beam in multiple directions.

[0048] 6. End Face Structure of Reflective Unit Cell Figure 12 illustrates the end face structure of the reflective unit cell 160. In Figure 12, 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.

[0049] 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 the semiconductor film. The transistor illustrated in Figure 12 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.

[0050] 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 12, 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 12, 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 on the same layer as the gate electrode 122, or it may be on the same layer as the electrodes 128 and 130. Alternatively, a portion of the wiring pattern 134 may be on the same layer as the gate electrode 122, and another portion may be on the same layer as the electrodes 128 and 130.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] Figures 1 to 12 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.

[0062] 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 13 is a schematic plan view of the radio wave reflection region RA. We will explain an example in which the multiple reflective elements 140 are arranged in a 46x46 arrangement within the radio wave reflection region RA. The other configurations of the radio wave reflection device 100 are the same as in Figure 1. 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 multiple reflective element groups 150a and 150b along the same direction as the direction in which radio waves are reflected (second direction D2).

[0063] In Figure 13, each of the multiple reflector groups 150a and 150b has multiple reflectors 140 arranged along the first direction D1 and the second direction D2. The number of multiple reflectors 140 in each of the multiple reflector groups 150a and 150b is the same. In the reflector groups 150a and 150b, the number of reflectors 140 arranged along the second direction D2 is greater than the number of reflectors 140 arranged along the first direction D1. Here, in the reflector group 150a, the reflection angle θ of the radio wave... １With the angle set to -45°, the group of reflective elements 150b reflects the radio wave at the reflection angle θ. ２ Let's explain the case where the angle is 45°.

[0064] Figure 14 is a table showing the phase difference based on the position of the reflecting elements and the reflection angle of radio waves in a radio wave reflector 100 according to one embodiment of the present invention. The phase difference of the radio wave reflector 100 shown in Figure 14 can be calculated in the same manner as in Figure 8. In the radio wave reflection region RA, the reflecting elements 140 arranged in columns 0 to 22 are θ １ The reflecting elements 140, located in rows 23 to 45, reflect radio waves at -45°, θ ２ Assume that radio waves are reflected at an angle of 45°. The phase difference of the reflected wave at each reflecting element 140 can be calculated using the above-mentioned equation (1). In the case of the radio wave reflection region RA shown in Figure 14, the phase difference of the reflected wave differs between the two reflecting element groups 150a and 150b in the second direction D2. Also, in each of the reflecting element groups 150a and 150b, the phase difference of the reflected waves of two adjacent reflecting elements in the first direction D1 is 0°. In Figure 14, the reflecting elements 140 in reflecting element group 150a are rows 0 to 45. Assuming the reflecting element at row 22.5 is in the middle of the first direction D1 of reflecting element group 150a, the phase difference of the reflecting element at row 22 is -322°, and the phase difference of the reflecting element at row 23 is -38°. Furthermore, using the midpoint in the second direction D2 of the reflective element group 150a and reflective element group 150b as a reference, the phase difference between adjacent reflective elements relative to the midpoint is ±38°, satisfying the ±45° requirement. This makes it possible to suppress deterioration of the reflection intensity distribution of the reflective element group 150a and reflective element group 150b.

[0065] In this case, a voltage is applied to each of the multiple reflective element groups 150 such that the phase difference of the reflected waves from two adjacent reflective elements in the same direction as the direction in which the multiple reflective element groups 150 extend (second direction D2) is different from that of two adjacent reflective elements, and the phase difference of the reflected waves from two adjacent reflective elements in the direction intersecting the direction in which the multiple reflective element groups 150 extend (first direction D1) is 0°. For details of the voltage applied to each reflective element, please refer to the explanations in Figures 7 and 8.

[0066] In the radio wave reflection region RA shown in Figures 13 and 14, the region is divided into multiple groups of radio wave reflectors along the same direction as the direction in which the radio waves are reflected. The voltage applied to each of the multiple reflectors 140 is set so that the reflection angle of the reflected radio waves differs for each of the multiple reflectors. This makes it possible to reduce the half-width of the peak received intensity at each of the multiple reflectors. Therefore, the controllability of the beam when reflecting at multiple reflection angles can be improved.

[0067] 8. Reflecting radio waves in an oblique direction The case of reflecting radio waves in an oblique direction within 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.

[0068] Figure 15 is a schematic plan view of the radio wave reflection region RA. An example in which the multiple reflective elements 140 are arranged in a 46x46 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. In the radio wave reflection region RA, the direction of radio wave reflection corresponds to the fourth direction D4 (diagonal direction). The radio wave reflection region RA is divided into multiple reflective element groups 150a and 150b along the same direction as the direction in which the radio waves are reflected (fourth direction D4).

[0069] In FIG. 15, in each of the plurality of reflector element groups 150a and 150b, a plurality of reflector elements 140 are arranged along the first direction D1 and the second direction D2. In FIG. 14, the number of the plurality of reflector elements 140 included in the plurality of reflector element groups 150a may be different from the number of the plurality of reflector elements 140 included in the plurality of reflector element groups 150b. In the reflector element groups 150a and 150b, the number of reflector elements 140 arranged along the fourth direction D4 is larger than the number of reflector elements 140 arranged along the fifth direction D5 intersecting the fourth direction D4. In FIG. 15, the reflector elements 140 included in the reflector element group 150a are arranged above the diagonal line connecting the reflector elements 140(0, 45) to 140(45, 0), and the reflector elements 140 included in the reflector element group 150b are arranged below the diagonal line connecting the reflector elements 140(0, 45) to 140(45, 0). Here, in the reflector element group 150a, the reflection angle θ of the radio wave １ is set to -45°, and the reflector element group 150b is described for the case where the reflection angle θ of the radio wave ２ is set to 45°.

[0070] FIG. 16 is a table showing the phase difference based on the positions of the reflector elements and the reflection angle of the radio wave in the radio wave reflection device 100 according to an embodiment of the present invention. The phase difference of the radio wave reflection device 100 shown in FIG. 16 can be calculated in the same manner as in FIG. 8. In the radio wave reflection region RA, in the reflector element group 150a, the radio wave is reflected at θ １ = -45°, and in the reflector element group 150b, θ ２Assume that radio waves are reflected at an angle of 45°. The phase difference of the reflected waves at each reflecting element 140 can be calculated using equation (1) described above. In the case of the radio wave reflection region RA shown in Figure 16, the two reflecting element groups 150a and 150b have different phase differences in the fourth direction D4. Also, in each of the reflecting element groups 150a and 150b, the phase difference of the reflected waves of two adjacent reflecting elements in the fifth direction D5 is 0°. The intermediate reflecting element in the fourth direction D4 of reflecting element group 150a is positioned on the diagonal line connecting 140(0,0) to 140(45,45). As shown in Figure 16, the phase difference of the reflecting elements positioned on the diagonal line connecting 140(0,0) to 140(45,45) is 0°. The phase difference between adjacent reflective elements 140 in the fourth direction D4 of the reflective element group 150a and reflective element group 150b is ±54°, satisfying the condition of being within ±90°. This makes it possible to suppress deterioration of the reflection intensity distribution of the reflective element group 150a and reflective element group 150b.

[0071] In this case, a voltage is applied to each of the multiple reflective element groups 150 such that the phase difference of the reflected waves from two adjacent reflective elements in the same direction as the direction in which the multiple reflective element groups 150 extend (fourth direction D4) is different from that of two adjacent reflective elements, and the phase difference of the reflected waves from two adjacent reflective elements in the direction intersecting the direction in which the multiple reflective element groups 150 extend (fifth direction D5) is 0°. For details of the voltage applied to each reflective element, please refer to the explanations in Figures 7 and 8.

[0072] In the radio wave reflection region RA shown in Figures 15 and 16, the region is divided into multiple groups of radio wave reflectors along the same direction as the direction in which the radio waves are reflected. The voltage applied to each of the multiple reflectors 140 is set so that the reflection angle of the reflected radio waves differs for each of the multiple reflectors. This makes it possible to reduce the half-width of the peak received intensity at each of the multiple reflectors. Therefore, the controllability of the beam when reflecting at multiple reflection angles can be improved.

[0073] 9. Reflecting Radio Waves in Three or More Directions The case in which radio waves are reflected in three or more directions within the radio wave reflection region RA will be explained. Figure 17 is a schematic plan view of the radio wave reflection region RA. An example in which the multiple reflective elements 140 are arranged in a 46x46 arrangement within the radio wave reflection region RA will be explained. The other configurations of the radio wave reflector 100 are the same as in Figure 1. In the radio wave reflection region RA, the direction of radio wave reflection corresponds to the first direction D1. In Figure 18, the radio wave reflection region RA is divided into multiple reflective element groups 150a to 150f along the same direction as the direction in which the radio waves are reflected (first direction D1). In Figure 18, the multiple reflective element groups 150a to 150f are arranged in a direction intersecting the direction in which the radio waves are reflected (second direction D2).

[0074] In Figure 17, the reflection angles θ of the radio waves are set to -34°, -38°, -42°, -45°, -55°, and -58° for each of the reflecting element groups 150a to 150f, respectively.

[0075] Table 1 shows the reflection direction [°], the phase difference [°] between elements, and the voltage difference [V] between elements for the reflective element group 150a to 150f.

[0076]

[0077] Figures 18A and 18B show examples of voltages applied to each reflector element 140. The solid lines in Figures 18A and 18B show the relationship between the position of the reflector element 140 in the reflector element group 150a to 150f and the voltage. In Figures 18A and 18B, the reflector elements positioned in the middle of the reflector elements aligned in the first direction D1 of the reflector element group 150 refer to the reflector elements in the 22nd and 23rd rows. In the case of Figure 18A, the inter-element phase difference dP in Table 1. ３４ dP ３８ dP ４２ dP ４５ dP ５５ dP ５８ The relationship is dP ３４ <dP ５８ <dP ４５ <dP ３８ <dP ４２ <dP ５５This results in an irregular phase difference setting for each reflective element group 150, which worsens the vertical reflection intensity distribution. In other words, as shown in Figure 18A, the voltage magnitudes at the reflective element 140 located in the middle of the reflective element groups 150a to 150f become different. Consequently, the phase differences at the reflective element 140 located in the middle of the reflective element groups 150a to 150f also become different.

[0078] In the case of Figure 18B, the inter-element phase difference dP is shown in Table 1. ３４ dP ３８ dP ４２ dP ４５ dP ５５ dP ５８ The relationship is dP ３４ <dP ３８ <dP ４２ <dP ４５ <dP ５５ <dP ５８ The following conditions are met. Also, the inter-element voltage difference dV in Table 1 ３４ dV ３８ dV ４２ dV ４５ dV ５５ dV ５８ The relationship is dV ３４ <dV ３８ <dV ４２ <dV ４５ <dV ５５ <dV ５８ This satisfies the following condition. In this case, the phase difference settings of each reflective element group 150 become regular, improving the vertical reflection intensity distribution. In Figure 18B, the magnitude of the voltage at the reflective element 140 located in the middle of the reflective element groups 150a to 150f becomes approximately the same. As a result, the phase difference at the reflective element 140 located in the middle of the reflective element groups 150a to 150f also becomes approximately the same.

[0079] A table showing the phase difference based on the position of the reflecting elements and the reflection angle of radio waves in the radio wave reflector 100 is not shown in the figure, but it can be calculated in the same manner as in Figure 8. In the table in Figure 8, the reflection angles of radio waves for reflecting element groups 150a to 150f should be -34°, -38°, -42°, -45°, -55°, and -58°, respectively. In this case, with respect to the midpoint in the first direction D1 of reflecting element groups 150a to 150f as the reference point, the phase differences of the reflecting elements adjacent to each other with respect to the midpoint are ±46°, ±44°, ±38°, ±36°, ±33°, and ±30°. With respect to the midpoint in the first direction D1 as the reference point for reflecting element groups 150a to 150f, the range of phase differences of the reflecting elements adjacent to each other with respect to the midpoint is 46° - 30° = 16°, which can be made approximately the same.

[0080] Figure 19 shows the simulation results of the reflection angle and reflection intensity of radio waves in a radio wave reflector 100 according to one embodiment of the present invention. The X-axis represents the radio wave reception angle θ [deg], and the Y-axis represents the normalized reception intensity [dB]. In Figure 19, peaks in reflection intensity were observed at θ = -34°, -38°, -42°, -45°, -55°, and -58°. In Figure 19, it can also be considered as a single beam having a range from -38° to -58°. In this way, the beam width at half maximum can be reduced according to the radio wave reflection angle θ, so the beam width can be widened by setting multiple reflection angles θ according to the desired beam width.

[0081] In conventional methods, when the radio wave reflection region RA is divided, the peaks of each beam in the range of -34° to -58° become broad, and the combined beam also becomes broad. This reduces the received signal strength level of the radio waves in the radio wave reflection region RA. In contrast, as shown in Figure 19, the peaks of each beam in the range of -34° to -58° can be made steeper. This improves the received signal strength level of the radio waves in the radio wave reflection region RA.

[0082] Furthermore, when setting multiple reflection angles, the reflection intensity of radio waves may be low depending on the reflection angle. In this case, the number of reflecting elements 140 in the reflecting element group 150 with low radio wave reflection intensity may be increased compared to the number of reflecting elements in the other reflecting element groups 150. By adjusting the number of reflecting elements, the reflection intensity at multiple reflection angles can be made uniform. This improves the in-plane uniformity of the beam.

[0083] Figures 17 to 19 illustrate an example in which the group of reflective elements 150 in the radio wave reflection region RA is divided into multiple sections along the horizontal direction. However, the group is not limited to this; it may also be divided into multiple sections along the vertical direction or along the diagonal direction. Furthermore, while an example was described in which the group of reflective elements 150 consists of multiple reflective elements 140 arranged in multiple rows and multiple columns, the group is not limited to this; it may also consist of multiple reflective elements 140 arranged in one row horizontally, one column vertically, or one column diagonally.

[0084] 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.

[0085] 100: Radio wave reflector, 102: Array substrate, 104: Opposing substrate, 106: Scan line driving circuit, 108: Signal line driving 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: Reflector 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, 150f: 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 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, and a voltage is applied to each of the plurality of reflecting elements such that the phase difference of the reflected waves from two adjacent reflecting elements in the first direction is different from that of the plurality of reflecting elements, and the phase difference of the reflected waves from two adjacent reflecting elements in the second direction is 0°.

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

3. The radio wave reflecting device according to claim 1, wherein the plurality of reflecting element groups include a first reflecting element group and a second reflecting element group, and the number of reflecting elements in the first reflecting element group is different from the number of reflecting elements in the second reflecting element group.

4. The radio wave reflector according to claim 3, wherein the plurality of reflecting element groups further includes a third reflecting element group, and the number of reflecting elements in the third reflecting element group is greater than the number of reflecting elements in the first reflecting element group and the number of reflecting elements in the second reflecting element group.

5. The radio wave reflecting device according to claim 1, wherein each of the plurality of reflecting element groups comprises a first reflecting element, a second reflecting element, and a third reflecting element, and in the first direction, the phase difference of the second reflecting element with respect to the first reflecting element is the same as the phase difference of the third reflecting element with respect to the second reflecting element.

6. The radio wave reflecting device according to claim 3, wherein, if the number of reflecting elements arranged in the first direction of the first reflecting element group is even, a sixth reflecting element is assumed to be located between two adjacent fourth and fifth reflecting elements positioned in the middle of the first direction of the first reflecting element group, and the phase difference of the fourth reflecting element and the phase difference of the fifth reflecting element are within ±90° with respect to the phase difference of the sixth reflecting element.

7. 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.

8. The radio wave reflector according to claim 7, wherein the frequency of the radio waves incident on the patch electrode is 28 GHz or near thereon.

9. The radio wave reflector according to claim 7, wherein a switching element is connected to the patch electrode.

Images