Radio wave reflection system

Abstract

This system includes a radio wave reflection device and a display device. The radio wave reflection device comprises: a plurality of reflection elements that include a liquid crystal layer and reflect radio waves; a drive circuit that drives the plurality of reflection elements; and a plurality of lines that supply a signal output from the drive circuit to the plurality of reflection elements. The display device is connected to the plurality of lines, and performs display based on a voltage supplied to at least one of the plurality of lines.

Description

Radio wave reflection system

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

[0002] In the fifth-generation communication system (5G), millimeter-wave electromagnetic waves are used. Since electromagnetic waves have the property that their straight-line propagation property increases as the frequency increases, a blind zone where communication is impossible easily occurs in the shadow of buildings and the like. Although this problem can be solved by increasing the number of base stations, it is not realistic considering costs and securing installation locations. Therefore, a reflectarray (also called a radio wave reflector or a metasurface reflector) that can asymmetrically reflect electromagnetic waves (radio waves) of a specific frequency has been proposed. For example, a reflectarray in which a reflection surface of radio waves is formed by arranging reflection elements having a liquid crystal layer sandwiched between a pair of electrodes in a matrix is known (see Patent Document 1).

[0003] International Publication No. 2023 / 058399

[0004] When the above reflectarray reflects radio waves, it is impossible to visually recognize how the radio waves are reflected. Therefore, even if a malfunction occurs in a part of the reflectarray, it cannot be detected.

[0005] One object of an embodiment of the present invention is to provide a radio wave reflection system that can visually determine the presence or absence of an abnormality in a radio wave reflection device.

[0006] A system according to an embodiment of the present invention is a system including a radio wave reflection device and a display device, the radio wave reflection device including a liquid crystal layer, a plurality of reflection elements that reflect radio waves, a drive circuit that drives the plurality of reflection elements, and a plurality of wirings that supply signals output from the drive circuit to the plurality of reflection elements, and the display device being connected to the plurality of wirings and performing display based on a voltage supplied to at least one of the plurality of wirings.

[0007] This is a block diagram illustrating the outline of a radio wave reflection system according to one embodiment of the present invention. This is a circuit diagram showing the outline of a display device according to one embodiment of the present invention. This is a cross-sectional view showing the outline of a radio wave reflection device according to one embodiment of the present invention. This is a cross-sectional view showing the outline of a display device according to one embodiment of the present invention. This is a plan view of a reflector unit cell used in a radio wave reflection device according to one embodiment of the present invention. This is a cross-sectional structure of a reflector unit cell used in a radio wave reflection device according to one embodiment of the present invention. This is a diagram showing a state in which no voltage is applied between the patch electrode and the ground electrode in a reflector unit cell used in a radio wave reflection device according to one embodiment of the present invention. This is a diagram showing the state in which a voltage is applied between the patch electrode and the ground electrode in a reflector unit cell used in a radio wave reflection device according to one embodiment of the present invention. This is a diagram showing the configuration of a radio wave reflection device according to one embodiment of the present invention. This is a diagram schematically showing how the direction of propagation of reflected waves changes due to a radio wave reflection device according to one embodiment of the present invention. This is a diagram showing the configuration of a radio wave reflection device according to one embodiment of the present invention. This is a cross-sectional structure of a reflector unit cell in a radio wave reflection device according to one embodiment of the present invention.

[0008] Embodiments of the present invention will be described below with reference to the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described below. In order to make the explanation clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual embodiment, but the drawings are merely examples and do not limit the interpretation of the present invention. In this specification and each drawing, components similar to those described above in previously shown drawings are denoted by the same reference numerals (or numerals followed by a, b, etc.), and detailed explanations may be omitted as appropriate. Furthermore, the letters "First," "Second," etc., attached to each element are convenient indicators used to distinguish each element and have no further meaning unless specifically explained.

[0009] In this specification, the expression "above (or below)" one member or region of another member or region includes, unless otherwise specified, not only cases where the member or region is directly above (or directly below) the other member or region, but also cases where it is above (or below) the other member or region. That is, the above expression also includes cases where another component is included between one member or region and the other member or region.

[0010] 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 through C, unless otherwise specified. Furthermore, these expressions do not exclude cases where α includes other elements.

[0011] The configurations described below can be combined with each other, as long as they do not create technical inconsistencies.

[0012] Referring to Figures 1 to 12, a radio wave reflection system 10 according to one embodiment of the present invention will be described. In the following embodiment, a radio wave reflection system 10 equipped with a radio wave reflection device 20 and a display device 30 is shown as an example of a radio wave reflection system.

[0013] [1. Overview of the Radio Wave Reflection System 10] This is a block diagram illustrating an overview of a radio wave reflection system according to one embodiment of the present invention. As shown in Figure 1, the radio wave reflection system 10 comprises a radio wave reflection device 20, a display device 30, a flexible circuit board (FPC 40), and a printed circuit board 50. The radio wave reflection device 20 and the printed circuit board 50 are connected by the FPC 40. The display device 30 is provided on the printed circuit board 50. However, the display device 30 may be provided on the FPC 40 or at other locations.

[0014] The radio wave reflector 20 includes a plurality of reflecting elements 102, a gate line drive circuit 160, gate lines 162 (162-1, 162-2, 162-3), wiring 164 (164-1, 164-2, 164-3), a source line drive circuit 170, source lines 172 (172-1, 172-2, 172-3), wiring 174 (174-1, 174-2, 174-3), gate line switching elements 180 (180-1, 180-2, 180-3), and source line switching elements 190 (190-1, 190-2, 190-3).

[0015] In the following description, gate wires 162-1, 162-2, and 162-3 will simply be referred to as gate wire 162 unless there is a need to distinguish between them. Wirings 164-1, 164-2, and 164-3 will simply be referred to as wiring 164 unless there is a need to distinguish between them. Source wires 172-1, 172-2, and 172-3 will simply be referred to as source wire 172 unless there is a need to distinguish between them. Wirings 174-1, 174-2, and 174-3 will simply be referred to as wiring 174 unless there is a need to distinguish between them. Gate wire switching elements 180-1, 180-2, and 180-3 will simply be referred to as gate wire switching element 180 unless there is a need to distinguish between them. Source wire switching elements 190-1, 190-2, and 190-3 will simply be referred to as source wire switching element 190 unless there is a need to distinguish between them.

[0016] Multiple gate lines 162 extend in the X-axis direction. One end of each gate line 162 is connected to a gate line drive circuit 160, and the other end of each gate line 162 is connected to a gate line switching element 180. Multiple source lines 172 extend in the Y-axis direction. One end of each source line 172 is connected to a source line drive circuit 170, and the other end of each source line 172 is connected to a source line switching element 190. A reflector element 102 is provided between one gate line 162 and one source line 172. The reflector element 102 is controlled by the gate line drive circuit 160 and the source line drive circuit 170. Signals output from the gate line drive circuit 160 are supplied to the reflector element 102 via the gate line 162. Signals output from the source line drive circuit 170 are supplied to the reflector element 102 via the source line 172. The reflector element 102 is controlled by these signals.

[0017] In other words, all the selection transistors 134 constituting the reflective element 102 of the radio wave reflector 20 are provided between the gate line drive circuit 160 and the gate line switching element 180. Similarly, all of the selection transistors 134 are provided between the source line drive circuit 170 and the source line switching element 190. However, this embodiment is not limited to this configuration. The gate line switching element 180 may be connected to a location other than the other end of each gate line 162. The source line switching element 190 may be connected to a location other than the other end of each source line 172.

[0018] The reflective element 102 comprises a selection transistor 134 and a capacitive element C1. The gate terminal of the selection transistor 134 is connected to the gate line 162. The source terminal of the selection transistor 134 is connected to the source line 172. The drain terminal of the selection transistor 134 is connected to the first terminal of the capacitive element C1 (patch electrode 108 (see Figure 3) described later). The second terminal of the capacitive element C1 (ground electrode 110 (see Figure 3) described later) is grounded. As will be described in detail later, the capacitive element C1 is a capacitive element with a liquid crystal layer 114 (see Figure 3) as its dielectric. The reflective element 102 reflects radio waves. The reflective element 102 displaces the phase of the reflected radio waves by the orientation of the liquid crystal molecules contained in the liquid crystal layer 114. The source terminal and drain terminal of the selection transistor 134 may be swapped. That is, the drain terminal of the selection transistor 134 may be connected to the source line 172, or the source terminal of the selection transistor 134 may be connected to the first terminal of the capacitive element C1. The selection transistor 134 is sometimes referred to as the "first transistor."

[0019] The gate line switching element 180 is provided between the gate line 162 and the wiring 164, and controls the gate line 162 and the wiring 164 to be in a conductive or non-conductive state. Multiple gate line switching elements 180 are controlled in common. That is, each gate terminal of the multiple gate line switching elements 180 is connected to the same control line 182 and controlled by the same control circuit 184. The wiring 164 is connected to the display device 30. Therefore, it can be said that the gate line switching element 180 is provided between the gate line 162 and the display device 30. Furthermore, it can be said that there is no reflective element 102 provided between the gate line switching element 180 and the display device 30. The control circuit 184 is provided on the printed circuit board 50. The gate line switching element 180 is sometimes referred to as the "first switching element".

[0020] The source line switching element 190 is provided between the source line 172 and the wiring 174, and controls the state of conduction or non-conductivity between the source line 172 and the wiring 174. Multiple source line switching elements 190 are controlled in common. That is, the gate terminals of each of the multiple source line switching elements 190 are connected to the same control line 192 and are controlled by the same control circuit 194. The wiring 174 is connected to the display device 30. Therefore, it can be said that the source line switching element 190 is provided between the source line 172 and the display device 30. Furthermore, it can be said that there is no reflective element 102 provided between the source line switching element 190 and the display device 30. The control circuit 194 is provided on the printed circuit board 50. The source line switching element 190 is sometimes referred to as the "second switching element".

[0021] Figure 2 is a circuit diagram showing an overview of a display device according to one embodiment of the present invention. As shown in Figure 2, the display device 30 has a plurality of pixels 202. Each pixel 202 has a selection transistor 234 and a liquid crystal cell LC. In this embodiment, the display device 30 is a liquid crystal panel. The gate terminal of the selection transistor 234 is connected to a wiring 164 extending from the radio wave reflector 20. The source terminal of the selection transistor 234 is connected to a wiring 174 extending from the radio wave reflector 20. The selection transistor 234 is sometimes referred to as the "second transistor".

[0022] The drain terminal of the selection transistor 234 is connected to the first terminal of the liquid crystal cell LC (the pixel electrode 208, described later (see Figure 4)). The second terminal of the liquid crystal cell LC (the common electrode 210, described later (see Figure 4)) is grounded. The source terminal and drain terminal of the selection transistor 234 may be swapped. That is, the drain terminal of the selection transistor 234 may be connected to the wiring 174, or the source terminal of the selection transistor 234 may be connected to the first terminal of the liquid crystal cell LC.

[0023] In this embodiment, there is a one-to-one relationship between multiple gate lines 162 and multiple wirings 164. Similarly, there is a one-to-one relationship between multiple source lines 172 and multiple wirings 174. That is, the number of gate lines 162 is the same as the number of wirings 164. Similarly, the number of source lines 172 is the same as the number of wirings 174. Therefore, the number of reflective elements 102 is the same as the number of pixels 202. However, the number of gate lines 162 may be greater than the number of wirings 164. Similarly, the number of source lines 172 may be greater than the number of wirings 174. That is, the number of reflective elements 102 may be greater than the number of pixels 202. In this case, multiple gate lines 162 may be connected to one wiring 164. Similarly, multiple source lines 172 may be connected to one wiring 174.

[0024] In the above configuration, the gate line drive circuit 160 may be referred to as the "first drive circuit." The source line drive circuit 170 may be referred to as the "second drive circuit." The gate line 162 may be referred to as the "first wiring." The source line 172 may be referred to as the "second wiring." The wiring 164 may be referred to as the "third wiring." The wiring 174 may be referred to as the "fourth wiring." In this case, the reflective element 102 can be said to be controlled by the gate line drive circuit 160 (first drive circuit) and the source line drive circuit 170 (second drive circuit). The gate line 162 (first wiring) and the source line 172 (second wiring) can be said to be connected to the display device 30. The wiring 164 (third wiring) can be said to be connected to the gate line 162 (first wiring) via the gate line switching element 180 (first switching element). Wiring 174 (fourth wiring) can be said to be connected to source wire 172 (second wiring) via source wire switching element 190 (second switching element).

[0025] In this embodiment, a configuration in which the display device 30 is a liquid crystal display device is illustrated, but the configuration is not limited to this. For example, the display device 30 may be an organic EL display device, or a display device in which LEDs are arranged in a matrix. Alternatively, the display device 30 may be a light-emitting element connected to each of the wirings 164-1 to 164-3 and 174-1 to 174-3.

[0026] When the gate line switching element 180 is conducting and the same voltage is supplied to the gate line 162 and the wiring 164, the same voltage is supplied to the gate terminal of the selection transistor 134 and the gate terminal of the selection transistor 234. Similarly, when the source line switching element 190 is conducting and the same voltage is supplied to the source line 172 and the wiring 174, the same voltage is supplied to the source terminal of the selection transistor 134 and the source terminal of the selection transistor 234.

[0027] For example, if both the gate line switching element 180 and the source line switching element 190 are in a conductive state, and a voltage V1 is supplied to the gate line 162-1 to control the selection transistor 134 to a conductive state, and a voltage V2 that controls the orientation of the liquid crystal layer 114 contained in the capacitive element C1 is supplied to all the source lines 172-1, 172-2, and 172-3, then in the display device 30, all the selection transistors 234 connected to wiring 164-1 are controlled to a conductive state, and voltage V2 is supplied to wirings 174-1 to 174-3. Therefore, the three pixels 202 connected to wiring 164-1 are controlled to a display state (a state where they are displayed brightly). In other words, the display device 30 displays based on the voltage V1 supplied to wiring 164-1, one of the multiple wirings 164, and the voltage V2 supplied to wirings 174-1 to 174-3.

[0028] In this example, the display device 30 displays a voltage V1 supplied to one of the multiple wires 164, wire 164-1, and a voltage V2 supplied to multiple wires 174-1 to 174-3. As shown in Figures 1 and 2, when both the reflective element 102 and the pixels 202 are arranged in a 3x3 configuration, the display device 30 can visually recognize that voltage is being supplied to the reflective element 102.

[0029] On the other hand, even though the radio wave reflector 20 is controlled to supply voltage to all the reflecting elements 102 shown in Figure 1, if a malfunction prevents voltage from being supplied to the gate line 162-1, voltage will not be supplied to the wiring 164-1 either. As a result, the pixel 202 connected to the wiring 164-1 will be controlled to be hidden (displayed dimly). In other words, malfunctions occurring in the radio wave reflector 20 can be visually recognized by the display device 30.

[0030] Even if a malfunction occurs in the radio wave reflector 20 where voltage is not supplied to the gate line 162 or the source line 172, it is difficult to detect the malfunction based on the reflection of radio waves. On the other hand, as described above, since the display device 30 is connected to the radio wave reflector 20, malfunctions that occur in the radio wave reflector 20 can be displayed on the display device 30.

[0031] In this embodiment, a configuration is illustrated in which the display device 30 displays information based on both the wiring 164 connected to the gate line 162 and the wiring 174 connected to the source line 172, but the configuration is not limited to this. For example, the display device 30 may display information based on only the wiring 164 or only the wiring 174.

[0032] [2. Cross-sectional structure of the radio wave reflector 20] Figure 3 is a cross-sectional view showing an overview of the radio wave reflector according to one embodiment of the present invention. As shown in Figure 3, the radio wave reflector 20 includes a plurality of reflecting elements 102. The plurality of reflecting elements 102 are arranged in at least one direction. In Figure 3, the plurality of reflecting elements 102 are arranged in the Y-axis direction. The radio wave reflector 20 includes a dielectric substrate 104, a counter substrate 106, a patch electrode 108, a ground electrode (counter electrode) 110, a liquid crystal layer 114, a sealing material 128, a selection transistor 134, a terminal portion 126, and an FPC 40. The liquid crystal layer 114 contains liquid crystal molecules 116. A passivation layer 158 is provided between the patch electrode 108 and the dielectric substrate 104. As will be described in detail later, if the radio wave reflector 20 is biaxial reflection control, the radio wave reflector 20 includes a selection transistor 134, but if the radio wave reflector 20 is uniaxial reflection control, the radio wave reflector 20 does not need to include a selection transistor 134.

[0033] The reflective element 102 includes at least a patch electrode 108, a ground electrode 110, a liquid crystal layer 114, and a selection transistor 134. The patch electrode 108 is provided individually for each reflective element 102. The patch electrode 108 is provided on the dielectric substrate 104 side. The ground electrode 110 is provided opposite the patch electrode 108 and is common to multiple reflective elements 102. The ground electrode 110 is provided on the opposing substrate 106 side.

[0034] The liquid crystal layer 114 is provided between the patch electrode 108 and the ground electrode 110. The orientation of the liquid crystal molecules 116 contained in the liquid crystal layer 114 is controlled by the voltage supplied to the patch electrode 108 and the ground electrode 110. The sealing material 128 is provided so as to surround the periphery of the opposing substrate 106. In other words, the liquid crystal layer 114 is sealed by the dielectric substrate 104, the opposing substrate 106, and the sealing material 128. The patch electrode 108 and the ground electrode 110 are provided in the region surrounded by the sealing material 128. The thickness of the liquid crystal layer 114 is 10 μm or more and 50 μm or less.

[0035] The radio wave reflector 20 is divided into a radio wave reflection region 163 and a surrounding region 165. A patch electrode 108 and a ground electrode 110 are arranged in the radio wave reflection region 163. Radio waves incident on the radio wave reflector 20 from the dielectric substrate 104 side are reflected in the radio wave reflection region 163. When radio waves are reflected, the direction of propagation of the reflected radio waves can be controlled by controlling the voltage supplied between the patch electrode 108 and the ground electrode 110, thereby controlling the orientation of the liquid crystal molecules 116.

[0036] The selection transistor 134 is connected to the patch electrode 108. The orientation of the liquid crystal molecules 116 is controlled according to the driving state of the selection transistor 134. As will be described in detail later, the phase of the radio waves reflected by the radio wave reflector 20 is controlled by controlling the orientation of the liquid crystal molecules 116. This phase control of the radio waves controls the direction of propagation of the reflected radio waves.

[0037] The terminal portion 126 is provided at the end of the dielectric substrate 104. The terminal portion 126 may be made up of the same single layer as the patch electrode 108. The terminal portion 126 may be made up of the same single layer as part or all of the conductive layer constituting the selection transistor 134. The terminal portion 126 is connected to the gate line drive circuit 160 and the source line drive circuit 170 via wiring. The FPC 40 is connected to the terminal portion 126. The gate line drive circuit 160 and the source line drive circuit 170 drive the selection transistor 134 in response to control signals input from the outside via the FPC 40.

[0038] [3. Cross-sectional structure of the display device 30] Figure 4 is a cross-sectional view showing an overview of a display device according to one embodiment of the present invention. As shown in Figure 4, the display device 30 includes a plurality of pixels 202. The plurality of pixels 202 are arranged in at least one direction. In Figure 4, the plurality of pixels 202 are arranged in the Y-axis direction. The display device 30 includes an array substrate 204, a counter substrate 206, a pixel electrode 208, a common electrode 210, a liquid crystal layer 214, a sealing material 228, a selection transistor 234, a terminal portion 226, and an FPC 40. The liquid crystal layer 214 contains liquid crystal molecules 216. A passivation layer 258 is provided between the pixel electrode 208 and the array substrate 204.

[0039] Each pixel 202 includes at least a pixel electrode 208, a common electrode 210, a liquid crystal layer 214, and a selection transistor 234. Each pixel electrode 208 is provided individually for each pixel 202. The pixel electrode 208 is located on the array substrate 204 side. The common electrode 210 faces the pixel electrode 208 and is provided in common for multiple pixels 202. The common electrode 210 is located on the opposing substrate 206 side.

[0040] The liquid crystal layer 214 is provided between the pixel electrode 208 and the common electrode 210. The orientation of the liquid crystal molecules 216 contained in the liquid crystal layer 214 is controlled by the voltage supplied to the pixel electrode 208 and the common electrode 210. The sealing material 228 is provided so as to surround the periphery of the opposing substrate 206. In other words, the liquid crystal layer 214 is sealed by the array substrate 204, the opposing substrate 206, and the sealing material 228. The pixel electrode 208 and the common electrode 210 are provided in the region surrounded by the sealing material 228. The thickness of the liquid crystal layer 214 is 3 μm or more and 10 μm or less.

[0041] As described above, the thickness of the liquid crystal layer 114 in the radio wave reflector 20 is more than twice the thickness of the liquid crystal layer 214 in the display device 30.

[0042] [4. Reflective Element 102] FIGS. 5 and 6 show the reflective element 102 used in the radio wave reflection device according to an embodiment of the present invention. FIG. 5 shows a plan view of the reflective element 102 seen from above (the side where radio waves are incident), and FIG. 6 shows a cross-sectional view between A1 - A2 shown in the plan view.

[0043] As shown in FIGS. 5 and 6, the reflective element 102 includes a dielectric substrate 104, a counter substrate 106, a patch electrode 108, a ground electrode 110, a liquid crystal layer 114, a first alignment film 112a, and a second alignment film 112b. Among the reflective element 102, the dielectric substrate 104 may be regarded as one layer (dielectric layer). The patch electrode 108 is provided on the dielectric substrate 104. The ground electrode 110 is provided on the counter substrate 106. A first alignment film 112a is provided on the dielectric substrate 104 so as to cover the patch electrode 108. A second alignment film 112b is provided on the counter substrate 106 so as to cover the ground electrode 110. The patch electrode 108 and the ground electrode 110 are arranged to face each other, and a liquid crystal layer 114 is provided between them. A first alignment film 112a is interposed between the patch electrode 108 and the liquid crystal layer 114. A second alignment film 112b is interposed between the ground electrode 110 and the liquid crystal layer 114.

[0044] The patch electrode 108 preferably has a shape that is symmetric with respect to the vertical polarization and horizontal polarization of the incident radio waves. For example, the patch electrode 108 has a square or circular shape in plan view. FIG. 5 shows the case where the patch electrode 108 is square in plan view. The shape of the ground electrode 110 is not particularly limited, and the ground electrode 110 has a shape that spreads over substantially the entire surface of the counter substrate 106 so as to have a larger area than the patch electrode 108. There is no limitation on the material for forming the patch electrode 108 and the ground electrode 110. The patch electrode 108 and the ground electrode 110 are formed using a conductive metal or metal oxide. The dielectric substrate 104 may be provided with a wiring 118. The wiring 118 is connected to the patch electrode 108. A control signal is supplied to the patch electrode 108 by the wiring 118. When a plurality of reflector unit cells are arranged, the wiring 118 connects a certain patch electrode and the patch electrode adjacent to it.

[0045] As shown in Figure 6, a first alignment film 112a is provided between the patch electrode 108 and the liquid crystal layer 114 between the dielectric substrate 104 and the opposing substrate 106, and a second alignment film 112b is provided between the ground electrode 110 and the liquid crystal layer 114. A spacer may be provided between the dielectric substrate 104 and the opposing substrate 106 to maintain a constant distance.

[0046] A control signal is supplied to the patch electrode 108 to control the orientation of the liquid crystal molecules 116 in the liquid crystal layer 114. The control signal is either a DC voltage signal or a polarity reversal signal in which positive DC voltage and negative DC voltage alternately reverse. In the latter case, the ground electrode 110 is supplied with a voltage at ground level or a voltage at an intermediate level between the polarity reversal signals. By supplying the control signal to the patch electrode 108, the orientation state of the liquid crystal molecules contained in the liquid crystal layer 114 changes. A liquid crystal material having dielectric anisotropy is used for the liquid crystal layer 114. For example, nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal, or discotic liquid crystal can be used as the liquid crystal layer 114. In a liquid crystal layer 114 having dielectric anisotropy, the dielectric constant changes with changes in the orientation state of the liquid crystal molecules. The reflecting element 102 can change the dielectric constant of the liquid crystal layer 114 by the control signal supplied to the patch electrode 108, thereby delaying the phase of the reflected wave when reflecting radio waves.

[0047] The frequency band of the radio waves reflected by the reflective element 102 is the microwave (SHF: Super High Frequency) band. The orientation of the liquid crystal molecules 116 in the liquid crystal layer 114 changes in response to the control signal supplied to the patch electrode 108, but the orientation of the liquid crystal molecules 116 hardly follows the frequency of the radio waves irradiated onto the patch electrode 108. Therefore, the reflective element 102 is not affected by the radio waves and can control the phase of the reflected radio waves.

[0048] Figure 7 shows a state in which no voltage is supplied between the patch electrode 108 and the ground electrode 110 (referred to as the "first state"). Figure 7 shows the case where the first alignment film 112a and the second alignment film 112b are horizontal alignment films. In the first state, the major axis of the liquid crystal molecules 116 is horizontally aligned with respect to the surfaces of the patch electrode 108 and the ground electrode 110 by the first alignment film 112a and the second alignment film 112b. Figure 8 shows a state in which a control signal (voltage signal) is supplied to the patch electrode 108 (referred to as the "second state"). In the second state, the liquid crystal molecules 116 are affected by the electric field, and their major axes are aligned perpendicular to the surfaces of the patch electrode 108 and the ground electrode 110. The angle at which the major axis of the liquid crystal molecules 116 is aligned can also be aligned in a direction intermediate between the horizontal direction and the vertical direction depending on the magnitude of the control signal supplied to the patch electrode 108 (the magnitude of the voltage between the counter electrode and the patch electrode).

[0049] When the liquid crystal molecules 116 have positive dielectric anisotropy, the dielectric constant of the second state is larger than that of the first state. On the other hand, when the liquid crystal molecules 116 have negative dielectric anisotropy, the apparent dielectric constant of the second state is smaller than that of the first state. The liquid crystal layer 114 having dielectric anisotropy can also be regarded as a variable dielectric layer. The reflection element 102 can be controlled to delay (or not delay) the phase of the reflected wave by utilizing the dielectric anisotropy of the liquid crystal layer 114.

[0050] The reflection element 102 functions as a reflector that reflects radio waves in a predetermined direction. It is preferable that the amplitude of the radio waves reflected by the reflection element 102 is not attenuated as much as possible. As is clear from the structure shown in FIG. 6, when radio waves propagating in the air are reflected by the reflection element 102, the radio waves pass through the dielectric substrate 104 twice. The dielectric substrate 104 is formed of a dielectric material such as glass or resin, for example. When radio waves pass through the dielectric, the phase velocity of the radio waves changes. Therefore, in order to prevent the amplitude of the reflected wave from being attenuated, it is preferable that the thickness of the dielectric substrate 104 is equivalent to a thickness of 1 / 4 wavelength of the radio waves to be reflected.

[0051] [5. Control Method of Radio Wave Reflector 20] The radio wave reflector 20, in which the reflecting elements 102 are integrated, will be described with reference to Figures 9 to 12. The radio wave reflector 20 has two types of control methods: a single-axis reflection control method and a double-axis reflection control method. The respective control methods will be described below.

[0052] [5-1. Radio Wave Reflector A (Uniaxial Reflection Control)] Figure 9 shows the configuration of a radio wave reflector 20a according to one embodiment of the present invention. The radio wave reflector 20a has a reflector 120. The reflector 120 is composed of a plurality of reflecting elements 102. The plurality of reflecting elements 102 are arranged, for example, in the X-axis direction and the Y-axis direction. The reflecting elements 102 are arranged such that the patch electrodes 108 face the incident surface of the radio waves. The reflector 120 is flat, and the plurality of patch electrodes 108 are arranged in a matrix within this flat surface. The radio wave reflector 20a (uniaxial reflection control) shown in Figure 9 does not necessarily include a selection transistor 134. Therefore, two drive circuits such as the gate line drive circuit 160 and the source line drive circuit 170 as shown in Figure 1 are not necessary, and it can be controlled by one drive circuit 124 as shown below.

[0053] The radio wave reflector 20 has a structure in which multiple reflecting elements 102 are integrated on a single dielectric substrate 104. As shown in Figure 9, the radio wave reflector 20 has a structure in which a dielectric substrate 104 on which multiple patch electrodes 108 are arranged and a counter substrate 106 on which a ground electrode 110 is provided are stacked on top of each other, with a liquid crystal layer 114 provided between the two substrates. The reflector 120 is formed in the region where the multiple patch electrodes 108 and the ground electrode 110 overlap. For each patch electrode 108, the cross-sectional structure of the reflector 120 is the same as the structure of the reflecting element 102 shown in Figure 6. The dielectric substrate 104 and the counter substrate 106 are bonded together with a sealing material 128, and the liquid crystal layer 114 is provided in the region inside the sealing material 128.

[0054] The dielectric substrate 104 has a thickness corresponding to one-quarter wavelength of the reflected radio wave. The dielectric substrate 104 has a region facing the opposing substrate 106, as well as a peripheral region 122 that extends outward from the opposing substrate 106. The peripheral region 122 is provided with a drive circuit 124 and a terminal section 126. The drive circuit 124 outputs a control signal to the patch electrode 108. The terminal section 126 is a region that forms a connection with an external circuit, and the FPC 40 is connected to the terminal section 126. A signal to control the drive circuit 124 is input to the terminal section 126.

[0055] As described above, multiple patch electrodes 108 are arranged on the dielectric substrate 104 in the X-axis direction and the Y-axis direction. Multiple wirings 118 extending in the Y-axis direction are provided on the dielectric substrate 104. Each of the multiple wirings 118 is electrically connected to the multiple patch electrodes 108 arranged in the Y-axis direction. In other words, the multiple patch electrodes 108 arranged in the Y-axis direction are connected by the wirings 118. The reflector 120 has a configuration in which multiple rows of patch electrode arrays connected by the wirings 118 are arranged in the X-axis direction.

[0056] Multiple wires 118 arranged on the reflector 120 extend into the surrounding area 122 and are connected to the drive circuit 124. The drive circuit 124 outputs control signals that are supplied to the patch electrodes 108. The drive circuit 124 is capable of outputting control signals with different voltage levels to each of the multiple wires 118. As a result, the reflector 120 supplies control signals to each of the multiple patch electrodes 108 arranged in the X-axis and Y-axis directions, row by row (each patch electrode 108 arranged in the Y-axis direction).

[0057] In the radio wave reflector 20a, a control signal is supplied to each set of patch electrodes 108 arranged in the Y-axis direction. This controls the direction of reflection of the reflected waves of the radio waves incident on the reflector 120. In other words, the radio wave reflector 20a can control the direction of propagation of the reflected waves of the radio waves irradiated onto the reflector 120 in the left-right direction of the drawing, with the reflection axis RY parallel to the Y-axis direction as the center.

[0058] In the case of the radio wave reflector 20a shown in Figure 9, although not shown, a switching element similar to the gate line switching element 180 or source line switching element 190 shown in Figure 1 is provided at the end in the Y-axis direction (upper end in Figure 9), and the wiring 118 and the display device 30 are connected when this switching element is controlled to a conductive state.

[0059] Figure 10 schematically illustrates how the direction of propagation of a reflected wave changes due to the two reflecting elements 102. When radio waves are incident on the first reflecting element 102a and the second reflecting element 102b with the same phase, and different control signals (V1 ≠ V2) are supplied to the first reflecting element 102a and the second reflecting element 102b, the phase change of the reflected wave due to the second reflecting element 102b is greater than that of the first reflecting element 102a. As a result, the phase of the reflected wave R1 reflected by the first reflecting element 102a is different from the phase of the reflected wave R2 reflected by the second reflecting element 102b (in Figure 10, the phase of the reflected wave R2 is ahead of the phase of the reflected wave R1), and the direction of propagation of the reflected wave appears to change diagonally.

[0060] In Figure 9, the multiple patch electrodes 108 arranged in the Y-axis direction are electrically connected by wiring 118 and are electrically at the same potential. Therefore, it is conceivable to replace them with a continuous strip-shaped electrode in the Y-axis direction rather than a divided shape. However, since there is an appropriate range for the dimensions of the patch electrodes 108 depending on the wavelength of the reflected radio waves, if the patch electrodes 108 are strip-shaped, the sensitivity to the target wavelength will decrease, and the behavior will differ for vertical and horizontal polarization. For this reason, as shown in Figure 9, it is preferable that each patch electrode 108 has a shape that is symmetrical with respect to vertical and horizontal polarization (in Figure 9, the shape of the patch electrodes 108 is square, but the shape of the patch electrodes 108 may be circular), and that the multiple patch electrodes 108 are arranged in an array, with the multiple patch electrodes 108 arranged parallel to the reflection axis RY connected by wiring 118.

[0061] Although not shown in the figures, the dielectric substrate 104 of the radio wave reflector 20a shown in Figure 9 has a thickness equivalent to one-quarter of the wavelength of the target radio wave. This suppresses the attenuation of the amplitude of the reflected wave reflected by the radio wave reflector 20.

[0062] [5-2. Radio Wave Reflector B (Two-Axis Reflection Control)] The above-described radio wave reflector 20a has a single reflection axis RY, so the reflection angle can be controlled in the direction of rotation around the reflection axis RY. The following radio wave reflector 20b can perform two-axis reflection control. The following explanation will focus on the differences between it and the above-described radio wave reflector 20a.

[0063] Figure 11 shows the configuration of the radio wave reflector 20b according to this embodiment. The following description will focus on the differences between this device and the radio wave reflector 20a shown in Figure 9.

[0064] The radio wave reflector 20b has a plurality of wirings 118 extending in the Y-axis direction, as well as a plurality of wirings 132 extending in the X-axis direction, on the reflector 120. The plurality of wirings 118 and 132 are arranged to intersect with an insulating layer (not shown) in between. The plurality of wirings 118 are connected to a drive circuit 124, and the plurality of wirings 132 are connected to a drive circuit 130. The drive circuit 124 outputs a control signal, and the drive circuit 130 outputs a scanning signal. In this configuration, the drive circuit 130 and the drive circuit 124 correspond to the gate line drive circuit 160 and the source line drive circuit 170 in Figure 1, respectively. The wirings 132 and 118 correspond to the gate line 162 and the source line 172 in Figure 1, respectively. In Figure 9, the drive circuit 124 is shown as a configuration in which an IC chip or the like is mounted on a dielectric substrate 104. The drive circuit 130 is shown as a drive circuit using thin-film transistors formed on a dielectric substrate 104, similar to the selection transistor 134, but is not limited to this.

[0065] Figure 11 shows an enlarged inset of the arrangement of four patch electrodes 108 and two wires 118 and 132. A selection transistor 134 is provided at each of the four patch electrodes 108. The switching (conducting and non-conducting states) of the selection transistor 134 is controlled by a scanning signal supplied to the wire 132. When the selection transistor 134 becomes conductive, the patch electrode 108 becomes conductive with the wire 118, and a control signal is supplied to that patch electrode 108. The selection transistor 134 is formed, for example, by a thin-film transistor. With this configuration, multiple patch electrodes 108 arranged in the X-axis direction can be selected row by row, and control signals with different voltage levels can be supplied to each row.

[0066] The radio wave reflector 20b shown in Figure 11 can control the propagation direction of reflected waves in the left-right direction of the drawing, centered on a reflection axis VR parallel to the Y-axis direction, and can also control the propagation direction of reflected waves in the up-down direction of the drawing, centered on a reflection axis HR parallel to the X-axis direction. In other words, since the radio wave reflector 20 has a reflection axis VR parallel to the Y-axis direction and a reflection axis VH parallel to the X-axis direction, the reflection angle can be controlled in the direction with the reflection axis VR as the axis of rotation and in the direction with the reflection axis HR as the axis of rotation.

[0067] Figure 12 shows an example of a cross-sectional structure of a reflective element 102 in which a selection transistor 134 is connected to a patch electrode 108. The selection transistor 134 is provided on a dielectric substrate 104. The selection transistor 134 is a transistor and has a structure in which a first gate electrode 138, a second gate insulating layer 146, a semiconductor layer 142, a second gate insulating layer 146, and a second gate electrode 148 are stacked. An undercoat layer 136 may be provided between the first gate electrode 138 and the dielectric substrate 104. Wiring 118 is provided between the first gate insulating layer 140 and the second gate insulating layer 146. Wiring 118 is provided so as to be in contact with the semiconductor layer 142. A first connecting wire 144 is provided in the same layer as the conductive layer forming the wiring 118. The first connecting wire 144 is provided so as to be in contact with the semiconductor layer 142. The connection structure of the wiring 118 and the first connecting wiring 144 to the semiconductor layer 142 is such that one wiring is connected to the source of the transistor and the other wiring is connected to the drain.

[0068] A first interlayer insulating layer 150 is provided so as to cover the selection transistor 134. Wiring 132 is provided below the first interlayer insulating layer 150. Wiring 132 is connected to a second gate electrode 148 via contact holes formed in the first interlayer insulating layer 150. Although not shown, the first gate electrode 138 and the second gate electrode 148 are electrically connected to each other in a region that does not overlap with the semiconductor layer 142. Below the first interlayer insulating layer 150, a second connecting wire 152 is provided, made of the same conductive layer as wiring 132. The second connecting wire 152 is connected to the first connecting wire 144 via contact holes formed in the first interlayer insulating layer 150.

[0069] A second interlayer insulating layer 154 is provided so as to cover the wiring 132 and the second connecting wiring 152. Furthermore, a planarization layer 156 is provided so as to fill the step of the selection transistor 134. By providing the planarization layer 156, the patch electrode 108 can be formed without being affected by the arrangement of the selection transistor 134. A passivation layer 158 is provided below the flat surface of the planarization layer 156. The patch electrode 108 is provided below the passivation layer 158. The patch electrode 108 is connected to the second connecting wiring 152 via contact holes that penetrate the passivation layer 158, the planarization layer 156, and the second interlayer insulating layer 154. A first alignment film 112a is provided below the patch electrode 108.

[0070] The opposing substrate 106 includes a ground electrode 110 and a second alignment film 112b, similar to that in Figure 6. The dielectric substrate 104 and the opposing substrate are arranged such that the surface of the dielectric substrate 104 on which the selection transistor 134 and patch electrode 108 are provided faces the surface of the opposing substrate on which the ground electrode 110 is provided. A liquid crystal layer 114 is provided between these substrates. The thickness t of the liquid crystal layer 114 can be defined as the length from the surface of the patch electrode 108 on the liquid crystal layer 114 side to the surface of the ground electrode 110 on the liquid crystal layer 114 side. In this case, the thickness t of the liquid crystal layer 114 may include the thickness of at least one insulating layer (undercoat layer 136, first gate insulating layer 140, second gate insulating layer 146, first interlayer insulating layer 150, second interlayer insulating layer 154, planarization layer 156, passivation layer 158) between the patch electrode 108 and the dielectric substrate 104.

[0071] Each layer formed on the dielectric substrate 104 is formed using the following materials. The undercoat layer 136 is formed of, for example, a silicon oxide film. The first gate insulating layer 140 and the second gate insulating layer 146 are formed of, for example, a silicon oxide film, or a laminated structure of a silicon oxide film and a silicon nitride film. The semiconductor layer is formed of an oxide semiconductor containing silicon semiconductors such as amorphous silicon and polycrystalline silicon, or metal oxides such as indium oxide, zinc oxide, and gallium oxide. The first gate electrode 138 and the second gate electrode 148 may be composed of, for example, molybdenum (Mo), tungsten (W), or alloys thereof. The wiring 118, wiring 132, first connecting wiring 144, and second connecting wiring 152 are formed using metallic materials such as titanium (Ti), aluminum (Al), and molybdenum (Mo). For example, the gate electrode and wiring described above may be composed of a titanium (Ti) / aluminum (Al) / titanium (Ti) laminated structure or a molybdenum (Mo) / aluminum (Al) / molybdenum (Mo) laminated structure. The planarization layer 156 is formed of a resin material such as acrylic or polyimide. The passivation layer 158 is formed of, for example, a silicon nitride film. The patch electrode 108 and ground electrode 110 are formed of a metal film such as aluminum (Al) or copper (Cu), or a transparent conductive film such as indium tin oxide (ITO).

[0072] As shown in Figure 12, the wiring 132 is connected to the gate of a transistor used as a selection transistor 134, the wiring 118 is connected to one of the source and drain of the transistor, and the patch electrode 108 is connected to the other of the source and drain. This allows a predetermined patch electrode to be selected from among a plurality of patch electrodes 108 arranged in a matrix and supplied with a control signal. Furthermore, by providing a selection transistor 134 to each patch electrode 108 in the reflector 120, a control voltage can be supplied to each patch electrode 108 arranged in a horizontal row along the first direction (X-axis direction) or to each patch electrode 108 arranged in a vertical row along the second direction (Y-axis direction). With this configuration, for example, when the reflector 120 is upright, the reflection direction of the reflected wave can be controlled in the left-right and up-down directions.

[0073] The various configurations of the radio wave reflector and reflector unit exemplified as one embodiment of the present invention can be combined as appropriate, as long as they do not contradict each other. Configurations in which a person skilled in the art has added, deleted or modified components, or added, omitted or modified processes, based on the radio wave reflector and reflector unit disclosed in this specification and drawings, are also included in the scope of the present invention, as long as they retain the essence of the present invention.

[0074] Any effects or benefits other than those brought about by the embodiments disclosed herein are to be understood to be brought about by the present invention if they are clear from the description herein or can be easily predicted by a person skilled in the art.

[0075] 10: Radio wave reflection system, 20: Radio wave reflection device, 30: Display device, 40: FPC, 50: Printed circuit board, 102: Reflecting element, 102a: First reflecting element, 102b: Second reflecting element, 104: Dielectric substrate, 106: Opposing substrate, 108: Patch electrode, 110: Ground electrode (opposing electrode), 112a: First alignment layer, 112b: Second alignment layer, 114: Liquid crystal layer, 116: Liquid crystal molecule, 118: Wiring, 120: Reflector, 122: Peripheral region, 124: Drive circuit, 126: Terminal section, 128: Sealing material, 130: Drive circuit, 132: Wiring, 134: Selecting transistor, 136: Undercoat layer, 138: First gate electrode, 140: First gate insulating layer, 142: Semiconductor layer, 144: First connection wiring, 146: Second gate insulation layer, 148: Second gate electrode, 150: First interlayer insulation layer, 152: Second connection wiring, 154: Second interlayer insulation layer, 156: Planarization layer, 158: Passivation layer, 160: Gate line drive circuit, 162: Gate line, 163: Radio wave reflection region, 164: Wiring, 165: Peripheral region, 170: Source line drive circuit, 172: Source line, 174: Wiring, 180: Gate line switching element, 182: Control line, 184: Control circuit, 190: Source line switching element, 192: Control line, 194: Control circuit, 202: Pixel, 204: Array substrate, 206: Opposing substrate, 208: Pixel electrode, 210: Common electrode, 214: Liquid crystal layer, 216: Liquid crystal molecule, 226: Terminal section, 228: Sealing material, 234: Selecting transistor, 258: Passivation layer

Claims

1. A system including a radio wave reflector and a display device, wherein the radio wave reflector includes a plurality of reflecting elements that reflect radio waves and include a liquid crystal layer, a drive circuit that drives the plurality of reflecting elements, and a plurality of wires that supply signals output from the drive circuit to the plurality of reflecting elements, and the display device is connected to the plurality of wires and displays a voltage supplied to at least one of the plurality of wires.

2. The system according to claim 1, wherein the display device includes a liquid crystal panel, and when a voltage that changes the orientation of liquid crystal molecules contained in the liquid crystal layer of the reflective element is supplied to at least one of the plurality of wirings, the liquid crystal panel is displayed.

3. The system according to claim 1, wherein the radio wave reflection device comprises a plurality of switching elements provided between the plurality of wirings and the display device.

4. The system according to claim 3, wherein the reflective element is not provided between the plurality of switching elements and the display device.

5. The system according to claim 1, wherein the drive circuit includes a first drive circuit and a second drive circuit, the plurality of wirings include a first wiring that supplies a signal output from the first drive circuit to the plurality of reflective elements, and a second wiring that supplies a signal output from the second drive circuit to the plurality of reflective elements, the plurality of reflective elements are controlled by the first drive circuit and the second drive circuit, and the first wiring and the second wiring are connected to the display device.

6. The system according to claim 5, wherein each of the plurality of reflective elements includes a first transistor and a capacitive element with the liquid crystal layer as a dielectric, the first wiring is connected to the gate terminal of the first transistor, and the second wiring is connected to the source terminal or drain terminal of the first transistor.

7. The system according to claim 5, wherein the radio wave reflector includes a first switching element and a second switching element, the first switching element being provided between the first wiring and the display device, and the second switching element being provided between the second wiring and the display device.

8. The system according to claim 7, wherein the reflective element is not provided between the first switching element and the display device, and between the second switching element and the display device.

9. The system according to claim 1, wherein the drive circuit includes a first drive circuit and a second drive circuit, the plurality of wirings include a plurality of first wirings that supply signals output from the first drive circuit to the plurality of reflecting elements, and a plurality of second wirings that supply signals output from the second drive circuit to the plurality of reflecting elements, the radio wave reflector includes a first switching element and a second switching element, the display device comprises a plurality of third wirings, a plurality of fourth wirings, and a plurality of pixels, the plurality of third wirings are each connected to the plurality of first wirings via the first switching element, the plurality of fourth wirings are each connected to the plurality of second wirings via the second switching element, each of the plurality of pixels includes a second transistor and a liquid crystal cell, the plurality of third wirings are each connected to the gate terminals of the plurality of second transistors, and the plurality of fourth wirings are each connected to the source terminals or drain terminals of the plurality of second transistors.

10. The system according to claim 9, wherein the number of the plurality of reflective elements is the same as the number of the plurality of pixels.

11. The system according to claim 9, wherein the number of the plurality of reflective elements is greater than the number of the plurality of pixels.

12. The system according to claim 9, wherein the reflective element is not provided between the first switching element and the display device, and between the second switching element and the display device.

13. The system according to claim 9, wherein the thickness of the liquid crystal layer is twice or more the thickness of the liquid crystal cell.

14. The system according to claim 2, wherein the thickness of the liquid crystal layer is 30 μm or more and 50 μm or less, and the thickness of the liquid crystal portion of the liquid crystal panel is 3 μm or more and 10 μm or less.

15. The liquid crystal layer has a thickness of 30 μm or more and 50 μm or less, and the liquid crystal cell has a thickness of 3 μm or more and 10 μm or less, the system according to any one of claims 9 to 13.

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