Radio wave reflection device

Abstract

A radio wave reflection device according to the present invention has a first unit cell group and a second unit cell group that are provided between a first substrate and a second substrate and can resonate at different frequency bands. A plurality of first radio wave reflection elements that constitute the first unit cell group are arrayed in a first direction and a second direction that intersects the first direction with gaps therebetween, and a plurality of second radio wave reflection elements that constitute the second unit cell group are arrayed in the first direction and the second direction with gaps therebetween. Second patch electrodes of the second radio wave reflection elements are smaller than first patch electrodes of the first radio wave reflection elements.

Description

radio wave reflector

[0001] An embodiment of the present invention relates to a radio wave reflecting device that can control the traveling direction of reflected radio waves. In the following description, the radio wave reflecting device is also referred to as an Intelligent Reflecting Surface, or IRS.

[0002] Since liquid crystal molecules have dielectric anisotropy, the dielectric constant of the liquid crystal layer can be controlled by adjusting the electric field applied to the liquid crystal layer containing the liquid crystal molecules to control the orientation of the liquid crystal molecules. It is known that by utilizing this property, it is possible to provide a radio wave reflection device whose reflection characteristics can be controlled (see, for example, Patent Documents 1 and 2).

[0003] JP 11-103201 A JP 2019-530387 A

[0004] The radio wave reflecting device has unit cells arranged in a matrix, each of which is made up of a patch electrode, a bias electrode, and a liquid crystal layer disposed between the patch electrode and the bias electrode. The patch electrode is designed to have dimensions that allow it to resonate at a desired frequency. The radio wave reflecting device can dynamically change the resonant frequency by applying a voltage to the unit cell, but the frequency band that can be accommodated is limited by the dielectric anisotropy Δε of the liquid crystal.

[0005] In wireless communication technology, radio wave reflecting devices are required to be able to cover at least one channel band in a given communication frequency band. As frequency bands shift to higher frequencies, the bandwidth of each channel also becomes wider. As communication frequency bands shift to higher frequencies in the era of high-capacity communication, the bandwidth of each channel becomes wider, and therefore radio wave reflecting devices are also required to cover wider bands.

[0006] An object of one embodiment of the present invention is to provide a radio wave reflecting device that can cover a wider frequency band.

[0007] A radio wave reflecting device according to one embodiment of the present invention has a first unit cell group and a second unit cell group that are arranged between a first substrate and a second substrate and are each capable of resonating in response to a different frequency band, wherein a plurality of first radio wave reflecting elements that constitute the first unit cell group are arranged at a distance in a first direction and a second direction that intersects with the first direction, and a plurality of second radio wave reflecting elements that constitute the second unit cell group are arranged at a distance in the first direction and the second direction, and the size of the second patch electrode of the second radio wave reflecting element is smaller than the size of the first patch electrode of the first radio wave reflecting element.

[0008] FIG. 1 is a plan view showing the configuration of a radio wave reflecting device according to one embodiment of the present invention. FIG. 2 is a layout diagram of a unit cell included in the radio wave reflecting device according to one embodiment of the present invention. FIG. 3 is a graph showing the results of a simulation of the frequencies at which each patch electrode has sensitivity, for two patch electrodes of different sizes. FIG. 4 is a graph showing the results of a simulation of the change in phase versus dielectric constant for frequencies of 59 GHz, 60 GHz, and 61 GHz. FIG. 5 is a cross-sectional view of a unit cell included in a radio wave reflecting device according to one embodiment of the present invention. FIG. 6 is a layout diagram of patch electrodes and bias electrodes. FIG. 7 is a layout diagram of a unit cell included in a radio wave reflecting device according to one embodiment of the present invention. FIG. 8 is a layout diagram of a unit cell included in a radio wave reflecting device according to one embodiment of the present invention. FIG. 9 is a layout diagram of a unit cell included in a radio wave reflecting device according to one embodiment of the present invention. FIG. 10 is a result of a simulation of the sizes of four patch electrodes when frequencies from 57 GHz to 66 GHz are divided into four channels. FIG. 11 is a layout diagram of a unit cell included in a radio wave reflecting device according to one embodiment of the present invention. FIG. 12 is a layout diagram of patch electrodes and bias electrodes. FIG. 13 is a cross-sectional view of a unit cell included in a radio wave reflecting device according to one embodiment of the present invention. FIG. 14 is a layout diagram of a unit cell included in a radio wave reflecting device according to one embodiment of the present invention. FIG. 15 is a layout diagram of patch electrodes and bias electrodes. It is a layout diagram of a patch electrode and a bias electrode.It is a perspective view of a radio wave reflecting device according to an embodiment of the present invention ...

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in many different forms, and should not be construed as being limited to the description of the following exemplary embodiments. For clarity of explanation, the drawings may show schematic representations of the width, thickness, shape, etc. of each part compared to the actual form. However, these are merely examples and are not intended to limit the interpretation of the present invention. Furthermore, in this specification and each drawing, elements similar to those previously described with reference to the preceding drawings are designated by the same reference numerals (or reference numerals with A, B, etc. suffixed thereto), and detailed descriptions may be omitted as appropriate. Furthermore, the letters "first," "second," "-1," and "-2" attached to each element are convenient labels used to distinguish each element and have no further meaning unless otherwise specified.

[0010] In this specification, when a component or region is referred to as being "on (or under)" another component or region, unless otherwise specified, this includes not only the case where it is directly above (or directly under) the other component or region, but also the case where it is above (or under) the other component or region, i.e., the case where another component is included between the component or region and above (or under) the other component or region.

[0011] First Embodiment A radio wave reflecting device according to one embodiment of the present invention will be described with reference to FIGS.

[0012] 1 is a plan view showing the configuration of a radio wave reflecting device 10 according to one embodiment of the present invention. In this embodiment, a radio wave reflecting device 10 capable of two-axis reflection control will be described.

[0013] The radio wave reflecting device 10 has a radio wave reflecting region 106, a scanning line driving circuit 110, and driver ICs 112 and 114. The radio wave reflecting region 106 has unit cell groups 211 and 212 provided between the array substrate 102 and the counter substrate 104. The radio wave reflecting device 10 has a frame region 108 surrounding the radio wave reflecting region 106. The scanning line driving circuit 110 is provided in the frame region 108 between the array substrate 102 and the counter substrate 104. The driver ICs 112 and 114 are provided on the array substrate 102 in the frame region 108 exposed from the counter substrate 104. The array substrate 102 and the counter substrate 104 are sealed with a sealant 116. A liquid crystal layer (not shown in FIG. 1 ) is provided in the gap between the array substrate 102 and the counter substrate 104 sealed with the sealant 116.

[0014] A plurality of scanning lines 118 are connected to the scanning line driving circuit 110 along the x direction. The driver IC 112 functions as a control unit that supplies signals to the scanning line driving circuit 110. A plurality of signal lines 119 are connected to the driver IC 114 along the y direction that intersects with the x direction. The plurality of signal lines 119 are controlled by a signal line driving circuit incorporated in the driver IC 114.

[0015] The radio wave reflecting device 10 can control the direction of travel of the reflected waves of the radio waves irradiated onto the radio wave reflecting area 106 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 direction of travel of the 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, because the radio wave reflecting device 10 has a reflection axis VR parallel to the Y-axis direction and a reflection axis HR parallel to the X-axis direction, it can control the reflection angle in the direction about the reflection axis VR as the rotation axis and in the direction about the reflection axis HR as the rotation axis.

[0016] Typically, multiple unit cells are arranged in a matrix in the x and y directions in the radio wave reflection area. Each unit cell is composed of a radio wave reflection element and a switching element (also called a transistor) that controls the radio wave reflection element. The radio wave reflection element is composed of a patch electrode, a bias electrode facing the patch electrode, and a liquid crystal layer between the patch electrode and the bias electrode. When the patch electrode is connected to a transistor, the potential applied to the patch electrode can be controlled. The liquid crystal molecules are oriented according to the potential difference between the potential applied to the patch electrode connected to the transistor and the potential applied to the bias electrode, thereby changing the dielectric constant. This allows the phase of the radio wave reflected by the patch electrode to be controlled, thereby controlling the direction of travel of the reflected radio wave.

[0017] Furthermore, the resonant frequency that can be controlled by the unit cell depends on the size of the patch electrode of the radio wave reflecting element. Specifically, the resonant frequency that can be controlled by the unit cell increases as the size of the patch electrode decreases. Here, the size of the patch electrode refers to the length of one side of the patch electrode (also referred to as the length of the side parallel to the vibration direction of the electric field (E) of the radio wave).

[0018] In order to realize a radio wave reflecting device that can cover a wider frequency band, it is possible to bond together multiple radio wave reflecting areas for different channels. However, this method has problems such as increased costs due to the increased number of parts required to construct the radio wave reflecting device, increased power consumption, and an increase in the size of the radio wave reflecting device due to the larger frame.

[0019] One embodiment of the present invention provides a radio wave reflecting device that can cover a wider frequency band with fewer components.

[0020] The radio wave reflection area 106 is provided between the array substrate 102 and the counter substrate 104 and includes a unit cell group 211 and a unit cell group 212. The unit cell group 211 and the unit cell group 212 control different frequency bands. The arrangement of the unit cell group 212 is preferably rotationally symmetric with respect to the point where the reflection axis HR and the reflection axis VR intersect. For example, if the radio wave reflection area 106 shown in FIG. 1 is divided into four approximately square quarters, the unit cell groups 211 and 212 are arranged with four-fold rotational symmetry. The unit cell group 211 is provided in the upper left and lower right regions, and the unit cell group 212 is provided in the lower left and upper right regions. The unit cell groups 211 and 212 may also be arranged with two-fold rotational symmetry. The unit cell group 211 includes a plurality of unit cells 221 arranged in a matrix along directions that intersect with each other. Similarly, the unit cell group 212 includes a plurality of unit cells 222 arranged in a matrix along directions that intersect with each other.

[0021] FIG. 2 is an enlarged view of a region 130, a part of the radio wave reflecting region 106 shown in FIG. 1 . In the region 130, scanning lines 118-1 to 118-4 are provided along the x direction, and signal lines 119-1 to 119-4 are provided along the y direction. FIG. 2 shows the layout of a plurality of unit cells 221 included in a unit cell group 211 and a plurality of unit cells 222 included in a unit cell group 212. The plurality of unit cells 221 are arranged in the x direction and the y direction. Each unit cell 221 is composed of a radio wave reflecting element 231 and a switching element (transistor 241) that controls the radio wave reflecting element 231. The plurality of unit cells 222 are arranged in the x direction and the y direction. Each unit cell 222 is composed of a radio wave reflecting element 232 and a switching element (transistor 241) that controls the radio wave reflecting element 232.

[0022] The radio wave reflecting element 231 is composed of a patch electrode 251, a bias electrode 261 (not shown in FIG. 2 ) provided opposite the patch electrode 251, and a liquid crystal layer (not shown in FIG. 2 ) provided between the patch electrode 251 and the bias electrode 261. Similarly, the radio wave reflecting element 232 is composed of a patch electrode 252, a bias electrode 262 provided opposite the patch electrode 252, and a liquid crystal layer (not shown in FIG. 2 ) provided between the patch electrode 252 and the bias electrode 262. The radio wave reflecting element 231 and the radio wave reflecting element 232 differ in the sizes of the patch electrode 251 and the patch electrode 252.

[0023] The size of the patch electrode 252 is smaller than the size of the patch electrode 251. As described above, the resonant frequency that can be controlled by the unit cell increases as the size of the patch electrode decreases. Therefore, the radio wave reflecting element 232 can control a higher frequency than the radio wave reflecting element 231. Note that, in one embodiment of the present invention, the size of the radio wave reflecting element is determined according to the size of the patch electrode. Therefore, when the size of the patch electrode 252 is smaller than the size of the patch electrode 251, the size of the radio wave reflecting element 232 will be smaller than the size of the radio wave reflecting element 231.

[0024] Here, we will explain the results of a simulation of the frequencies (resonant frequencies) to which each patch electrode is sensitive for two patch electrodes of different sizes. The simulation conditions were as follows: the thickness of the glass substrate onto which the radio waves are incident was 1 mm, the pitch of the patch electrodes was 1.5 mm, and the relative dielectric constant of the liquid crystal layer was 3. The patch electrodes were available in two sizes: 1.24 mm square and 1.3 mm square. This simulation was performed using CST Studio Suite (manufactured by Dassault Systèmes).

[0025] 3 is a graph showing the results of a simulation of the frequencies at which each patch electrode has sensitivity for two patch electrodes of different sizes. The horizontal axis represents frequency [GHz], and the vertical axis represents reflection coefficient [dB]. When the patch electrode size is 1.3 mm square, the resonant frequency is 57.3 GHz. When the patch electrode size is 1.24 mm square, the resonant frequency is 60.2 GHz. In other words, when comparing the patch electrode sizes of 1.3 mm square and 1.24 mm square, the resonant frequencies are 2.9 GHz apart. However, in one embodiment of the present invention, the resonant frequencies of patch electrodes of different sizes only need to be at least 2 GHz apart.

[0026] Furthermore, it is preferable that the shape of each of the patch electrodes 251 and 252 is a shape that can accommodate the wide bandwidth of one channel. Being able to accommodate a wide bandwidth means that the amount of phase change for the bandwidth of one channel does not change significantly depending on the frequency.

[0027] Next, we will explain the results of a simulation of the amount of phase change versus dielectric constant for frequencies of 59 GHz, 60 GHz, and 61 GHz. The simulation conditions were: the thickness of the glass substrate onto which the radio waves are incident is 1 mm, the pitch of the patch electrodes is 1.5 mm, and the minimum and maximum relative dielectric constants of the liquid crystal layer are 2.5 and 3.5, respectively. The size of the patch electrodes is 1.25 mm square. This simulation was performed using CST Studio Suite (manufactured by Dassault Systèmes).

[0028] Figure 4 is a graph showing the results of a simulation of the phase change versus the dielectric constant for frequencies of 59 GHz, 60 GHz, and 61 GHz. The horizontal axis represents the dielectric constant of the liquid crystal layer, and the vertical axis represents Δθ [deg.]. As shown in Figure 4, it can be seen that the same amount of phase change is obtained at 60±1 GHz. Therefore, a 2 GHz band can be covered per channel.

[0029] When the communication frequency is in the 60 GHz band, four channels are provided with center frequencies ranging from 57.24 GHz to 65.88 GHz at intervals of 2.16 GHz. In one embodiment of the present invention, in order to provide a radio wave reflecting device 10 capable of covering such a wide frequency band, a unit cell group is formed using radio wave reflecting elements 231 and 232 of different sizes. The radio wave reflecting elements 231 and 232 control different frequency bands. Furthermore, the resonant frequency to which the patch electrode 251 is sensitive is preferably at least 2 GHz away from the resonant frequency to which the patch electrode 252 is sensitive. For example, if the radio wave reflecting elements 231 and 232 controlling different frequency bands are arranged in a staggered pattern, the radio wave reflecting element 231 will be adjacent to the radio wave reflecting elements 232 on the top, bottom, left, and right sides. If the radio wave reflecting element 231 is surrounded by radio wave reflecting elements 232 controlling different frequency bands, a phase difference will occur due to the difference in the dimensions of the patch electrodes.

[0030] Therefore, in one embodiment of the present invention, a unit cell group 211 is arranged in which a plurality of radio wave reflecting elements 231 of the same size are arranged closely together, and a unit cell group 212 is arranged in which a plurality of radio wave reflecting elements 232 are arranged closely together.

[0031] 1 , in the radio wave reflecting area 106, the area in which the unit cells are arranged is divided into four substantially square sections, and the unit cell groups 211 and 212 are adjacent to each other. Therefore, the radio wave reflecting element 231 arranged at the boundary between the unit cell groups 211 and 212 is adjacent to the radio wave reflecting element 232, but is also adjacent to at least two radio wave reflecting elements 231. In other words, it is possible to prevent the radio wave reflecting element 231 from being surrounded by radio wave reflecting elements 232 that control different resonance frequencies. This makes it possible to prevent a phase difference from occurring in the radio waves reflected at the boundary between the two unit cell groups, which would be caused by a difference in size between the radio wave reflecting elements 231 and 232.

[0032] In a plan view, the number of the plurality of radio wave reflecting elements 231 included in the unit cell group 211 may be the same as the number of the plurality of radio wave reflecting elements 232 included in the unit cell group 212. In addition, in a plan view, the interval at which the plurality of radio wave reflecting elements 231 are adjacent to one another may be different from the interval at which the plurality of radio wave reflecting elements 232 are adjacent to one another.

[0033] 5 shows a planar layout of bias electrodes 261 and 262 provided on the opposing substrate 104. As shown in FIG. 5, the bias electrode 261 is arranged to face a plurality of patch electrodes 251, and the bias electrode 262 is arranged to face a plurality of patch electrodes 252. In this embodiment, the number of bias electrodes 261 and 262 is the same as the number of unit cell groups 211 and 212. A common potential is applied to each of the bias electrodes 261 and 262. By providing a plurality of bias electrodes, the size of each of the bias electrodes 261 and 262 is reduced, and the in-plane voltage gradient is reduced.

[0034] Fig. 6 is a cross-sectional view of the radio wave reflecting region 106 and the frame region 108 in the radio wave reflecting device 10. Fig. 6 mainly shows the cross-sectional structure of the unit cell 221 arranged in the radio wave reflecting device 10. The cross-sectional structure of the unit cell 222 is the same as that of the unit cell 221 except for the size of the patch electrode 252. Therefore, for the configuration of the unit cell 222, refer to the description of the configuration of the unit cell 221. Note that in Fig. 6, the surface that reflects radio waves is on the array substrate 102 side.

[0035] Dielectric substrates are used for the array substrate 102 and the counter substrate 104. The array substrate 102 and the counter substrate 104 face each other, providing physical strength to the radio wave reflecting device 10 and providing a surface for disposing the radio wave reflecting element 231. The array substrate 102 and the counter substrate 104 may contain inorganic insulators such as glass or quartz, semiconductors such as silicon, polymers such as polyimide, polycarbonate, or polyester, or metals such as aluminum, copper, or stainless steel. If a conductive material such as metal is included, it is preferable to provide an undercoat 142 or an overcoat 164 on the surfaces on which the radio wave reflecting element 231 is provided, i.e., the surface of the array substrate 102 facing the counter substrate 104 and the surface of the counter substrate 104 facing the array substrate 102. The array substrate 102 and the counter substrate 104 may or may not be transparent to visible light. The array substrate 102 and the counter substrate 104 may also be flexible. The array substrate 102 and the counter substrate 104 are fixed to each other by a sealant 116 directly or via an alignment film 160 and an alignment film 162 (described later).

[0036] 6, the radio wave reflecting element 231 includes a patch electrode 251, an alignment film 160 on the patch electrode 251, a liquid crystal layer 136 on the alignment film 160, an alignment film 162 on the liquid crystal layer 136, and a bias electrode 261 on the alignment film 162. Radio waves are incident from the patch electrode 251 side.

[0037] The radio wave reflecting element 231 is connected to an element circuit including at least one transistor 241. Each element circuit may include multiple transistors and may further include one or multiple capacitive elements. As can be seen from FIG. 6 , the element circuit including the transistor 241 and the radio wave reflecting element 231 are provided on the array substrate 102 directly or via an undercoat 142 of any configuration. The transistor 241 included in the element circuit is not limited in its structure and may be a bottom-gate transistor or a top-gate transistor. Alternatively, the transistor 241 may be a dual-gate transistor having gate electrodes above and below the semiconductor film.

[0038] 6 is a bottom-gate transistor, and is composed of a gate electrode 144, a gate insulating film 146 on the gate electrode 144, a semiconductor layer 148 on the gate insulating film 146, and a pair of electrodes 150 and 152 on the semiconductor layer 148. A planarization film 156 is provided on the transistor 241, and a radio wave reflecting element 231 is formed thereon. As an optional configuration, interlayer insulating films 154 and 158 may be provided between the transistor 241 and the planarization film 156, or on the planarization film 156, respectively.

[0039] The bias electrode 261 of the radio wave reflecting element 231 is electrically connected to the transistor 241 through an opening provided in the interlayer insulating film 154, the planarizing film 156, or the like. Various signals supplied from an external circuit are input to the terminal portion 138 (see FIG. 1 ) and supplied to the radio wave reflecting element 231 via wiring, either directly or via a drive circuit. As shown in FIG. 6 , a wiring pattern 166 is formed in the frame region 108 (see FIG. 1 ). The wiring pattern 166 includes multiple wires. Although not shown in FIG. 6 , at least a portion of the wiring pattern 166 is connected to the terminal portion 138, and at least a portion of the wiring pattern 166 extends over the frame region 108. The wiring pattern 166 may be present in the same layer as the gate electrode 144, or may be present in the same layer as the electrodes 150 and 152. Alternatively, a portion of the wiring pattern 166 may be present in the same layer as the gate electrode 144, and another portion may be present in the same layer as the electrodes 150 and 152.

[0040] The gate electrode 144, gate insulating film 146, semiconductor layer 148, electrodes 150 and 152, interlayer insulating films 154 and 158 and planarizing film 156 covering the transistor 241, wiring pattern 166, and terminal portion 138 can be formed using known materials and by appropriately applying known methods, and detailed descriptions thereof will be omitted. Briefly, the gate electrode 144, electrodes 150 and 152, wiring pattern 166, and terminal portion 138 are formed by forming a film containing a metal such as tantalum, molybdenum, titanium, or aluminum using a sputtering method or a chemical vapor deposition (CVD) method, and then appropriately patterning the film using a photolithography process. The semiconductor layer 148 is formed as a film containing a Group 14 element such as silicon, or a film containing an oxide of a Group 13 element such as indium or gallium. The semiconductor layer 148 may also be formed by applying a sputtering method or a CVD method. The gate insulating film 146, the interlayer insulating films 154 and 158, the undercoat 142, and the overcoat 164 contain inorganic compounds such as silicon-containing inorganic compounds, such as silicon oxide and silicon nitride, and are formed by applying a sputtering method or a CVD method. The planarizing film 156 contains a polymer, such as an acrylic resin, an epoxy resin, a polyimide, a polyamide, or a silicone resin, and can be formed by appropriately using a wet film-forming method, such as a spin coating method, an inkjet method, or a printing method. By providing the planarizing film 156, the radio wave reflecting element 231 can be formed on a flat surface.

[0041] A patch electrode 251 is provided for each radio wave reflecting element 231. Therefore, the patch electrodes 251 are also arranged in a matrix shape having multiple rows and columns, and in each radio wave reflecting element 231, the patch electrode 251 overlaps with the bias electrode 261. The patch electrode 251 is electrically connected to the transistor 241, and a potential is applied to the patch electrode 251 via the transistor 241. Therefore, the multiple patch electrodes 251 are insulated from each other and from the patch electrode 252. As described above, radio waves are incident from the patch electrode 251 side. Therefore, it is preferable that the patch electrode 251 have a highly symmetrical shape, such as a regular polygon or a circle, so as to efficiently reflect both orthogonal components of the radio wave (vertical polarization and horizontal polarization). The size of the patch electrode 251 can be adjusted appropriately depending on the wavelength of the radio wave to be reflected. For example, the row and column lengths may be selected appropriately from a range of 1 mm to 40 mm. In this embodiment, the unit cell 222 is made to control a higher frequency than the unit cell 221 , so the size of the patch electrode 252 may be made smaller than the size of the patch electrode 251 .

[0042] The patch electrode 251 includes, for example, a metal such as copper, aluminum, tungsten, molybdenum, or titanium, or an alloy containing at least one of these metals. Alternatively, it may include a conductive oxide such as indium zinc oxide (IZO) or indium tin oxide (ITO). The patch electrode 251 may also have a single-layer structure. For example, it may have a laminated structure of a layer containing a conductive oxide and a layer containing the above-mentioned metal or alloy. Alternatively, the bias electrode 261 may have a mesh shape to impart light transmissivity to the bias electrode 261 containing a metal or alloy.

[0043] The alignment film 160 provided in contact with the plurality of patch electrodes 251 is provided to control the alignment of liquid crystal molecules constituting the liquid crystal layer 136 provided thereunder. The alignment film 160 can be provided continuously across the plurality of radio wave reflecting elements 231, 232. In other words, the alignment film 160 can be provided so as to be shared by all of the radio wave reflecting elements 231 without being divided between adjacent radio wave reflecting elements 231.

[0044] The bias electrode 261 is provided on the opposing substrate 104 side. Like the patch electrode 251, the bias electrode 261 includes, for example, a metal such as copper, aluminum, tungsten, molybdenum, or titanium, or an alloy containing at least one of these metals. Alternatively, the bias electrode 261 may include a light-transmitting conductive oxide such as indium zinc oxide (IZO) or indium tin oxide (ITO). The bias electrode 261 may have a single-layer structure or a layered structure in which layers of different compositions are stacked. For example, a layered structure of a layer containing a conductive oxide and a layer containing the above-mentioned metal or alloy may be employed. Alternatively, the bias electrode 261 may have a mesh shape to impart light transmittance to the metal or alloy-containing bias electrode 261.

[0045] The patch electrode 251 and the bias electrode 261 may be formed by applying a sputtering method, a CVD method, or the like. The radio wave reflecting element 231 may or may not transmit visible light. Therefore, visible light may be blocked by using a metal or alloy having a thickness that does not transmit visible light for the patch electrode 251 and the bias electrode 261. As shown in FIG. 5 , the size of the bias electrode 261 is not particularly limited as long as it is arranged so as to overlap with multiple patch electrodes 251 in the unit cell group 211. Therefore, the size of the bias electrode 262 may be the same as or smaller than the size of the bias electrode 261.

[0046] The alignment films 160 and 162 are provided to control the alignment of liquid crystal molecules. The alignment films 160 and 162 can be formed so that they are continuous across adjacent radio wave reflecting elements 231 and are shared by multiple radio wave reflecting elements 231. The alignment films 160 and 162 are arranged so that the direction in which the alignment film 160 aligns the liquid crystal molecules is parallel to that of the alignment film 162. The alignment films 160 and 162 align the liquid crystal molecules in a specific direction. The alignment films 160 and 162 contain polymers such as polyimide or polyester. The alignment films 160 and 162 are formed using a wet film formation method such as an inkjet method, a spin coating method, a printing method, or a dip coating method, and their surfaces are subjected to a rubbing treatment. Alternatively, the alignment films 160 and 162 may be formed by a photo-alignment treatment.

[0047] The liquid crystal layer 136 is sealed by a sealant 116 provided between the array substrate 102 and the counter substrate 104. The structure of the liquid crystal molecules contained in the liquid crystal layer 136 is not limited. Therefore, the liquid crystal molecules may be nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal, or chiral smectic liquid crystal. Because the radio wave reflecting elements 231 and 232 are provided in an area surrounded by the sealant 116, the dielectric constant of the liquid crystal layer of the radio wave reflecting element 231 is the same as the dielectric constant of the liquid crystal layer of the radio wave reflecting element 232. The thickness of the liquid crystal layer 136 is, for example, 10 μm to 100 μm, preferably 20 μm to 60 μm. Although not shown, spacers may be provided within the liquid crystal layer 136 to maintain this thickness throughout the entire radio wave reflecting device 10. Note that if the above-described thickness of the liquid crystal layer 136 is used in a liquid crystal display device, the high responsiveness required for displaying moving images cannot be achieved, making it extremely difficult to function as a liquid crystal display device.

[0048] In the radio wave reflecting device 10, as described above, the orientation directions of the alignment films 160 and 162 that align the liquid crystal molecules are parallel. Therefore, when no potential difference is applied between the bias electrode 261 and the patch electrode 251, no vertical electric field is generated in the liquid crystal layer 136, and the liquid crystal molecules are horizontally aligned. The orientation of the liquid crystal layer 136 is the same between the radio wave reflecting elements 231, and therefore the dielectric constant is also constant within the liquid crystal layer 136. As a result, the spread (phase) of the reflected wave generated when the radio wave incident from the patch electrode 251 side is reflected by the surface of the patch electrode 251 does not change. As a result, the incident radio wave is specularly reflected by the radio wave reflecting device 10, and a reflected wave is generated at an output angle that is the same as the angle of incidence.

[0049] In contrast, when the voltage applied to the patch electrode 252 is controlled using an element circuit to create a potential difference between the patch electrode 252 and the bias electrode 261, the liquid crystal molecules rise and become vertically oriented due to the generated vertical electric field. At this time, if vertical electric fields of different strengths are generated between the radio wave reflecting elements 231, the dielectric constant of the liquid crystal layer 136 changes between the radio wave reflecting elements 231 depending on the strength of the vertical electric field. As a result, the phase of the reflected wave changes, and accordingly, the reflection direction of the radio wave incident on the radio wave reflecting area 106 can be changed. The reflection direction can be freely controlled by changing the strength of the vertical electric field formed in the radio wave reflecting element 231.

[0050] In one embodiment of the present invention, the radio wave reflecting area 106 is divided into four substantially square sections, and the unit cell groups 211 and 212 are arranged adjacent to each other. The size of the unit cells 222 in the unit cell group 212 is smaller than the size of the unit cells 221 in the unit cell group 211. That is, the size of the patch electrode 252 in the unit cell 222 is smaller than the size of the patch electrode 251 in the unit cell 221. In this case, the resonant frequency to which the patch electrode 251 is sensitive is 2 GHz or more away from the resonant frequency to which the patch electrode 252 is sensitive. This allows the radio wave reflecting device 10 to control different frequency bands by using the unit cell groups 211 and 212.

[0051] In this way, by providing multiple unit cell groups capable of controlling different frequency bands in the radio wave reflecting device 10, it is possible to cover a wider frequency band. Furthermore, by providing multiple unit cell groups capable of controlling different frequency bands between the array substrate 102 and the opposing substrate 104, the number of components can be reduced, thereby reducing costs. Furthermore, since the multiple unit cell groups capable of controlling different frequency bands can be controlled by a drive circuit and a driver IC provided on the array substrate 102, power consumption can be reduced. Furthermore, since the frame area can be made smaller than when multiple radio wave reflectors are attached to the same substrate, the radio wave reflecting device 10 can be made more compact.

[0052] Furthermore, by preventing the radio wave reflecting element 231 from being surrounded by radio wave reflecting elements 232 that control different frequency bands, it is possible to prevent a phase difference from occurring due to differences in size.

[0053] [Modifications] The present invention is not limited to the above-described embodiment, and includes various other modifications. For example, the above-described embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to an embodiment having all of the described configurations. Other configurations may be added to, deleted from, or substituted for part of the configuration of the embodiment and part of the modifications described below. Modifications are described below.

[0054] (1) In the present embodiment, the radio wave reflecting area 106 is divided into four substantially square sections, with the unit cell groups 211 provided in the upper left and lower right sections and the unit cell groups 212 provided in the lower left and upper right sections. However, the layout of the unit cell groups 211 and 212 is not limited to this. The layout of the unit cell groups 211 and 212 can be changed as appropriate, as described below. In the following description, a case where a plurality of unit cell groups 212 capable of controlling different frequency bands are arranged will be described with reference to FIGS. 7 to 10. Note that, in FIGS. 7 to 10, as in FIG. 6, the radio wave reflecting element 231 will be described as having the patch electrode 252 electrically connected to the transistor 241, with the surface that reflects radio waves facing the array substrate 102.

[0055] FIG. 7 is a diagram illustrating an example of the layout of the unit cell groups 211 and 212. FIG. 7 is an enlarged view of a portion of the radio wave reflecting region 106. As shown in FIG. 7, the unit cell groups 211 and 212 may be arranged alternately in rows. The radio wave reflecting elements of the unit cell group 211 may be arranged in a single row, and the radio wave reflecting elements of the unit cell group 212 may also be arranged in a single row. Alternatively, although not shown, the unit cell groups 211 and 212 may be arranged alternately in columns. The radio wave reflecting elements of the unit cell group 211 may be arranged in a single column, and the radio wave reflecting elements of the unit cell group 212 may also be arranged in a single column.

[0056] FIG. 8 is a diagram illustrating an example of the layout of the unit cell groups 211 and 212. FIG. 8 is an enlarged view of an area corresponding to a region 130 of the radio wave reflecting area 106 shown in FIG. 1 . As shown in FIG. 8 , the unit cell groups 211 and 212 may be arranged alternately in multiple rows. The radio wave reflecting elements of the unit cell group 211 may be arranged in two or more rows, and the radio wave reflecting elements of the unit cell group 212 may also be arranged in two or more rows. However, it is preferable that the number of rows of the radio wave reflecting elements arranged in the unit cell groups 211 and 212 be the same. Alternatively, although not shown, the unit cell groups 211 and 212 may be arranged alternately in multiple columns. The radio wave reflecting elements of the unit cell group 211 may be arranged in two or more rows, and the radio wave reflecting elements of the unit cell group 212 may also be arranged in two or more rows.

[0057] Furthermore, the number of unit cell groups capable of controlling different frequency bands arranged in the radio wave reflecting area 106 may be three or more. FIG. 9 is an enlarged view of an area corresponding to region 130 of the radio wave reflecting area 106 shown in FIG. 1 . FIG. 9 is a diagram illustrating an example of the layout of four unit cell groups 211 to 214. When the radio wave reflecting area 106 is divided into four quarters, the unit cell group 211 may be arranged in the upper left, the unit cell group 212 in the upper right, the unit cell group 213 in the lower left, and the unit cell group 214 in the lower right. When three or more frequency bands are to be controlled, the multiple unit cell groups arranged in the radio wave reflecting area 106 do not necessarily need to be arranged rotationally symmetrically. For example, when three frequency bands are to be controlled, each unit cell group may be arranged in one row and three columns. When three or more frequency bands are to be controlled, it is preferable to arrange the unit cells so that they do not intermix in order to suppress interference caused by dimensional differences between the patch electrodes.

[0058] The patch electrodes 251 to 254 of the unit cell groups 211 to 214 are different in size from one another. This allows the unit cell groups 211 to 214 to control four different frequency bands. As shown in FIG. 9 , the patch electrode 251 is the largest, followed by the patch electrode 252, patch electrode 253, and patch electrode 254 in decreasing order. For example, when 57 GHz to 66 GHz are divided into four channels, the center frequencies of the four channels are 58.1 GHz, 60.4 GHz, 62.6 GHz, and 64.9 GHz. The sizes of the patch electrodes 251 to 254 are determined so that four channels are assigned to each of the unit cell groups 211 to 214.

[0059] Here, we will explain the results of simulating the sizes of the patch electrodes 251 to 254 when 57 GHz to 66 GHz are divided into four channels. The simulation conditions were: the thickness of the glass substrate onto which the radio waves are incident is 1 mm, the pitch of the patch electrodes is 1.5 mm, and the relative dielectric constant of the liquid crystal layer is 3. Under these conditions, the sizes of the patch electrodes 251 to 254 were simulated. This simulation was performed using CST Studio Suite (manufactured by Dassault Systèmes).

[0060] 10 shows the results of a simulation of the sizes of patch electrodes 251 to 254 when 57 GHz to 66 GHz are divided into four channels. The horizontal axis represents the length of one side of the patch electrode [mm], and the vertical axis represents the resonant frequency [GHz]. The lengths of one side of the patch electrodes for the four channels obtained by the simulation are shown in Table 1.

[0061]

[0062] As shown in Table 1, the patch electrodes 251 to 254 may be set to have sides of 1.28 mm, 1.23 mm, 1.19 mm, and 1.14 mm, respectively, in ascending order of length. In Fig. 9, the cross-sectional structure of the unit cells in the unit cell groups 211 to 214 is the same as that of the unit cell 221 shown in Fig. 6, except for the size of the patch electrodes. Therefore, for the configuration of the unit cells in the unit cell groups 211 to 214, the description of the configuration of the unit cell 221 may be referred to.

[0063] 9 illustrates an example in which the radio wave reflecting region 106 is divided into four and the unit cell groups 211 to 214 are arranged, but one embodiment of the present invention is not limited to this. In the radio wave reflecting region 106, the unit cell groups 211, 212, 213, and 214 may be arranged so as to be repeated in the order of rows or columns.

[0064] 7 to 10, for example, the unit period in which the plurality of radio wave reflecting elements 231 are arranged is different from the unit period in which the plurality of radio wave reflecting elements 232 are arranged. However, one embodiment of the present invention is not limited to this, and the unit period in which the plurality of radio wave reflecting elements 231 are arranged may be the same as the unit period in which the plurality of radio wave reflecting elements 232 are arranged. The unit period is the distance from the left end of a patch electrode to the left end of the patch electrode adjacent to the right.

[0065] FIG. 11 is a diagram illustrating an example of the layout of the unit cell groups 211 and 212. As shown in FIG. 11 , the interval between adjacent radio wave reflecting elements 231 is the same as the interval between adjacent radio wave reflecting elements 232. When the interval between adjacent radio wave reflecting elements 231 and the interval between adjacent radio wave reflecting elements 232 are set to be the same, patch electrodes of different sizes are arranged in a row and patch electrodes of different sizes are arranged in a column. Therefore, in order to make the interval between adjacent radio wave reflecting elements 231 and the interval between adjacent radio wave reflecting elements 232 the same, the scanning lines 118-1 to 118-4 and the signal lines 119-1 to 119-4 may be bent as appropriate. By making the unit period at which the radio wave reflecting elements 231 are arranged the same as the unit period at which the radio wave reflecting elements 232 are arranged, the area occupied by the unit cell group 212 in which the small-sized radio wave reflecting elements 232 are arranged may be smaller than the area occupied by the unit cell group 211. This allows the unit cell groups to be separated from each other, thereby reducing mutual influence.

[0066] In addition, for the arrangement of the unit cell groups 211 and 212 shown in Figure 8 and the unit cell groups 211 to 214 shown in Figure 9, the scanning line 118 and the signal line 119 may be bent so that the spacing between two adjacent patch electrodes 251 and the spacing between two adjacent patch electrodes 252 are the same.

[0067] 12 is a layout diagram of bias electrodes applicable to the multiple unit cell groups shown in FIGS. 2 and 7 to 10. In FIG. 12, a bias electrode 265 is provided so as to overlap with the unit cell groups 211 to 214. As shown in FIG. 12, multiple unit cell groups 211 to 214 can be controlled by one bias electrode 265. When controlling with one bias electrode 265, the number of wirings can be reduced.

[0068] Although not shown, a unit cell group 211 in which four unit cells 221 are arranged in a substantially square shape and a unit cell group 212 in which four unit cells 222 are arranged in a substantially square shape may be arranged in a lattice pattern (also called a houndstooth or checkerboard pattern). In the unit cell groups 211 and 212, the four unit cells are arranged in a substantially square shape, so that unit cells controlling different frequency bands can be prevented from being surrounded by each other even if they are close to each other. This makes it possible to prevent a phase difference from occurring due to a difference in the dimensions of the radio wave reflecting elements 231 and 232.

[0069] (2) In the present embodiment, an example has been described in which the surface that reflects radio waves is on the array substrate 102 side, but the present embodiment is not limited to this. The surface that reflects radio waves may be on the opposing substrate 104 side.

[0070] 13 is a diagram illustrating an example of the layout of the four unit cell groups 211 to 214. FIG. 14 is a planar layout of the bias electrodes 261 to 264 and the patch electrodes 251 to 254. The layout of the four unit cell groups 211 to 214 shown in FIG. 9 differs from the layout of the four unit cell groups 211 to 214 shown in FIG. 13 in that the transistors 241 to 244 are connected to the bias electrodes 261 to 264 rather than to the patch electrodes. The bias electrode 261 is electrically connected to the transistor 241, and a potential is applied to the bias electrode 261 via the transistor 241. Therefore, the multiple patch electrodes 251 are insulated from each other and are also insulated from the bias electrodes 262 to 263.

[0071] As shown in FIG. 14 , rectangular patch electrodes 251 to 254 are arranged for each of the radio wave reflecting elements 231 to 234, and the patch electrodes 251 to 254 are electrically connected to each other. The patch electrodes 251 to 254 function as common electrodes to which a common potential is applied. The sizes of the patch electrodes 251 to 254 decrease in the order of patch electrode 251, patch electrode 252, patch electrode 253, and patch electrode 254. Therefore, the sizes of the radio wave reflecting elements 231 to 234 shown in FIG. 13 also decrease in the order of radio wave reflecting element 231, radio wave reflecting element 232, radio wave reflecting element 233, and radio wave reflecting element 234. For the sizes of the patch electrodes 251 to 254, please refer to the descriptions of FIGS. 9 and 10 . Note that, as shown in FIG. 13 , the bias electrodes 261 to 264 may have the same size.

[0072] FIG. 15 is a cross-sectional view of the radio wave reflecting region 106 and the frame region 108 in the radio wave reflecting device 10A. FIG. 15 mainly shows the cross-sectional structure of the unit cell 221 disposed in the radio wave reflecting device 10A. The cross-sectional structure of the unit cell 222 is the same as that of the unit cell 221 except for the size of the patch electrode 252. Therefore, for the configuration of the unit cell 222, refer to the description of the configuration of the unit cell 221. Note that in FIG. 15, the surface that reflects radio waves faces the opposing substrate 104. The radio wave reflecting device shown in FIG. 15 differs from the radio wave reflecting device shown in FIG. 6 in that the transistor 241 is connected to the bias electrode 261 and the patch electrode 251 is provided on the opposing substrate 104 side. Since the other configurations are the same as those in FIG. 6, detailed description thereof will be omitted.

[0073] 16 shows a planar layout of the bias electrodes 261 to 264 and the patch electrodes 251 to 254. In Fig. 16, a common potential is applied to each of the patch electrodes 251 to 254. In this way, the common potential applied to the patch electrodes 251 to 255 may be controlled for each of the unit cell groups 211 to 214.

[0074] (3) In the present embodiment, an example has been described in which the sealant 116 is disposed so as to surround the entire radio wave reflection region 106, but this embodiment of the present invention is not limited to this. For example, each of the unit cell groups 211 to 214 may be surrounded by the sealant 116. In this case, different liquid crystal molecules may be used to form liquid crystal layers for each of the unit cell groups 211 to 214 that control different frequency bands.

[0075] FIG. 17 is a perspective view of a radio wave reflecting device 10B according to one embodiment of the present invention. The array substrate 102 and the counter substrate 104 are bonded together with a sealant 116. The sealant 116 is arranged to separate the unit cell groups 211-214. In other words, the sealant 116 surrounds each of the unit cell groups 211-214. In the radio wave reflecting device 10B shown in FIG. 17, liquid crystal layers 271-274 can be arranged using different liquid crystal molecules for each of the unit cell groups 211-214. The different liquid crystal molecules are, for example, liquid crystal molecules with different dielectric constants. The liquid crystal molecules may be appropriately selected from the liquid crystal molecules described in FIG. 6 according to the frequency bands controlled by the unit cell groups 211-214.

[0076] (4) A radio wave reflecting device according to one embodiment of the present invention may be provided with a radio wave absorbing pattern for absorbing radio waves. FIG. 18 is a perspective view of a radio wave reflecting device according to one embodiment of the present invention. The radio waves reflected by the radio wave reflecting device 10C include not only the desired reflected waves obtained from the unit cell groups 211-214, but also radio waves reflected at the boundary regions where the unit cell groups 211-214 are adjacent to each other. The radio waves reflected at the boundary regions where the unit cell groups 211-214 are adjacent to each other cannot be controlled. This reduces the amplitude of the reflected waves, resulting in a deterioration of the reflection characteristics.

[0077] 18, a radio wave absorbing pattern 281 is provided in the boundary region where the unit cell groups 211 to 214 are adjacent to each other. This makes it possible to absorb radio waves that are incident on regions other than the unit cell groups 211 to 214, thereby suppressing unintended reflection of radio waves. Therefore, it is possible to suppress reflection loss of reflected waves.

[0078] Although not shown in detail, the radio wave absorbing pattern 281 may be formed from the same conductive layer as the patch electrode 251 or the bias electrode 261. By forming the radio wave absorbing pattern 281 from the same conductive layer as the patch electrode 251 or the bias electrode 261, a pattern that absorbs radio waves is provided in proximity to the radio wave reflecting elements 231 and 232. For example, when the bias electrode 261 is provided on the counter substrate 104 side, the radio wave absorbing pattern 281 may be formed from the same conductive layer as the bias electrode 261 in the boundary region of the unit cell groups 211 to 214. Alternatively, when the patch electrode 251 is provided on the counter substrate 104 side, the radio wave absorbing pattern 281 may be formed from the same conductive layer as the patch electrode 251 in the boundary region of the unit cell groups 211 to 214. Alternatively, if the surface that reflects radio waves is the counter substrate 104, the radio wave absorbing pattern 281 may be formed in the boundary region of the unit cell groups 211 to 214 on the surface opposite to the surface on which the radio wave reflecting elements are provided of the counter substrate 104. Alternatively, if the surface that reflects radio waves is the array substrate 102, the radio wave absorbing pattern 281 may be formed on the surface opposite to the surface on which the radio wave reflecting elements are provided of the array substrate 102.

[0079] One example of a configuration of a radio wave reflecting device that suppresses reflection of radio waves in unintended areas is a configuration in which a radio wave absorber is provided on the outermost surface of the radio wave reflecting device. FIG. 19 is a perspective view of a radio wave reflecting device 10D according to one embodiment of the present invention. When the surface that reflects radio waves is the counter substrate 104, a radio wave absorber 282 may be provided in the boundary region between the unit cell groups 211-214 on the surface of the counter substrate 104 opposite the surface on which the radio wave reflecting elements are provided. The radio wave absorber 282 may be a film having radio wave absorption properties that is attached to the counter substrate 104. Alternatively, when the surface that reflects radio waves is the array substrate 102, the radio wave absorber 282 may be provided in the boundary region between the unit cell groups 211-214 on the surface on which the radio wave reflecting elements are provided. By providing the radio wave absorber 282, radio waves incident on areas other than the unit cell groups 211-214 can be absorbed, thereby suppressing unintended reflection of radio waves. This reduces reflection loss of reflected waves.

[0080] The radio wave reflecting devices 10, 10A to 10D illustrated as an embodiment of the present invention can be combined as appropriate as long as they are not mutually inconsistent. Furthermore, devices in which a person skilled in the art appropriately adds or deletes components or modifies the design, or adds or omits processes or modifies conditions based on the configuration of the radio wave reflecting devices 10, 10A to 10D disclosed in this specification and drawings, are also included in the scope of the present invention as long as they include the gist of the present invention.

[0081] Even if there are other effects and advantages different from those brought about by the aspects of the embodiments disclosed in this specification, those that are clear from the description in this specification or that can be easily predicted by a person skilled in the art are naturally understood to be brought about by the present invention.

[0082] 10: radio wave reflecting device, 102: array substrate, 104: opposing substrate, 106: radio wave reflecting area, 108: frame area, 110: scanning line driving circuit, 112: driver IC, 114: driver IC, 116: sealing material, 118: scanning line, 119: signal line, 136: liquid crystal layer, 138: terminal portion, 142: undercoat, 144: gate electrode, 146: gate insulating film, 148: semiconductor layer, 150: electrode, 152: electrode, 154: interlayer Insulating film, 156: planarizing film, 158: interlayer insulating film, 160: alignment film, 162: alignment film, 164: overcoat, 166: wiring pattern, 211 to 214: unit cell group, 221 to 224: unit cells, 231 to 234: radio wave reflecting elements, 241 to 244: transistors, 251 to 255: patch electrodes, 261 to 265: bias electrodes, 271 to 274: liquid crystal layer, 281: radio wave absorbing pattern, 282: radio wave absorber

Claims

1. A radio wave reflecting device comprising: a first unit cell group and a second unit cell group, each of which is arranged between a first substrate and a second substrate and is capable of resonating in a different frequency band; a plurality of first radio wave reflecting elements constituting the first unit cell group are arranged at a distance in a first direction and a second direction intersecting the first direction; a plurality of second radio wave reflecting elements constituting the second unit cell group are arranged at a distance in the first direction and the second direction; and the size of the second patch electrode of the second radio wave reflecting element is smaller than the size of the first patch electrode of the first radio wave reflecting element.

2. The radio wave reflecting device according to claim 1, wherein at the boundary between the first unit cell group and the second unit cell group, the first radio wave reflecting element is adjacent to the second radio wave reflecting element, and at least two first radio wave reflecting elements are adjacent to each other.

3. The radio wave reflecting device according to claim 1, wherein the number of the first radio wave reflecting elements in the first unit cell group is the same as the number of the second radio wave reflecting elements in the second unit cell group.

4. The radio wave reflecting device according to claim 1, wherein, in a plan view, the unit period at which the plurality of first radio wave reflecting elements are arranged is different from the unit period at which the plurality of second radio wave reflecting elements are arranged.

5. The radio wave reflecting device according to claim 1, wherein, in a plan view, the unit periodic interval at which the plurality of first radio wave reflecting elements are arranged is the same as the unit period at which the plurality of second radio wave reflecting elements are arranged.

6. The radio wave reflecting device according to claim 1, wherein a radio wave absorbing pattern is arranged so as to overlap the boundary region between said first unit cell group and said second unit cell group.

7. A radio wave reflecting device according to claim 1, wherein a radio wave absorber is provided on a second surface of the second substrate opposite to a first surface on which the first radio wave reflecting element and the second radio wave reflecting element are provided.

8. A radio wave reflecting device as described in claim 1, wherein the first radio wave reflecting element includes the first patch electrode, a first bias electrode overlapping the first patch electrode, and a first liquid crystal layer provided between the first patch electrode and the first bias electrode; the second radio wave reflecting element includes the second patch electrode, a second bias electrode overlapping the second patch electrode, and a second liquid crystal layer provided between the first patch electrode and the first bias electrode; and the size of the second patch electrode is smaller than the size of the second patch electrode.

9. The radio wave reflecting device according to claim 8, wherein the resonant frequency to which said first patch electrode is sensitive is separated by 2 GHz or more from the resonant frequency to which said second patch electrode is sensitive.

10. The radio wave reflecting device according to claim 8, further comprising a first transistor and a second transistor provided on the first substrate, the first transistor being connected to the first patch electrode and the second transistor being connected to the second patch electrode, and the first bias electrode and the second bias electrode being provided on the second substrate.

11. The radio wave reflecting device according to claim 10, wherein the first patch electrode is insulated from the second patch electrode.

12. The radio wave reflecting device according to claim 10, wherein the first bias electrode is electrically connected to the second bias electrode.

13. The radio wave reflecting device according to claim 8, further comprising a first transistor and a second transistor provided on the first substrate, the first transistor being connected to the first bias electrode and the second transistor being connected to the second bias electrode, and the first patch electrode and the second patch electrode being provided on the second substrate.

14. The radio wave reflecting device according to claim 13, wherein the first bias electrode is insulated from the second bias electrode.

15. The radio wave reflecting device according to claim 13, wherein the first patch electrode is electrically connected to the second patch electrode.

16. The radio wave reflecting device according to claim 8, wherein the dielectric constant of the first liquid crystal layer is the same as the dielectric constant of the second liquid crystal layer.

17. The radio wave reflecting device according to claim 8, wherein the dielectric constant of the first liquid crystal layer is different from the dielectric constant of the second liquid crystal layer.

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