Radio wave reflecting device

Abstract

The radio wave reflecting device includes a patch electrode, a common electrode, a liquid crystal layer sandwiched between the patch electrode and the common electrode, and a metal film disposed on the side of the common electrode opposite to the liquid crystal layer side, the metal film is disposed apart from the common electrode, and the patch electrode is disposed so as to overlap the metal film. The value obtained by multiplying the distance (T) between the common electrode and the metal film by the wavelength (lambda) of the radio waves irradiated to the patch electrode is set as x, and x may be 0.02-0.34 (inclusive). Further, x may be from 0.10 to 0.22 (inclusive).

Description

Technical Field

[0001] One embodiment of the present invention relates to a radio wave reflecting device. Background Art

[0002] As a phase shifter used in a phased array antenna device capable of electrically controlling directivity, a phase shifter using liquid crystal has been developed (see Patent Documents 1 and 2).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 11-103201

[0006] Patent Document 2: Japanese Patent Application No. 2019-530387 Summary of the invention

[0007] Problems to be solved by the invention

[0008] In a phased array antenna device, antenna elements connected to phase shifters are arranged in one dimension or two dimensions, and the dielectric constant of the liquid crystal needs to be adjusted in such a way that the phase difference of the signal input to the adjacent antenna elements is fixed. In addition, research is also being conducted on a reflector that can control the reflection direction using liquid crystal. The reflector is also a structure in which the reflection electrodes (patch electrodes) are arranged in one dimension or two dimensions, and the reflection phase can be controlled by adjusting the dielectric constant of the liquid crystal of each electrode portion by voltage, thereby setting the reflection direction of the radio wave to an arbitrary direction. It is preferred that the reflection amplitude of the reflector is high, but there is a problem that the reflection amplitude is small in the reflector using liquid crystal.

[0009] In view of such problems, one of the objects of one embodiment of the present invention is to provide a radio wave reflection device having a novel structure. Another object is to provide a radio wave reflection device having a high reflection gain.

[0010] Solutions to Solve Problems

[0011] An electric wave reflecting device according to one embodiment of the present invention comprises: a patch electrode, a common electrode, a liquid crystal layer sandwiched by the patch electrode and the common electrode, and a metal film arranged on the side of the common electrode opposite to the liquid crystal layer side, wherein the metal film is arranged separately from the common electrode, and the patch electrode is arranged to overlap with the metal film. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1A It is a plan view showing a unit cell of a reflector plate used in a radio wave reflecting device according to one embodiment of the present invention.

[0013] Figure 1BThe cross-sectional structure of a unit cell of a reflector used in a radio wave reflecting device according to an embodiment of the present invention is shown.

[0014] Figure 2A The figure shows a state where no voltage is applied between the patch electrode and the common electrode when the reflector unit cell used in the radio wave reflection device according to one embodiment of the present invention is in operation.

[0015] Figure 2B The following diagram shows a state in which voltage is applied to the patch electrode and the common electrode when the reflector unit cell used in the radio wave reflection device according to one embodiment of the present invention is in operation.

[0016] Figure 3 The results of measuring the reflection amplitude with respect to the distance between the common electrode and the metal film of the radio wave reflection device of this example are shown.

[0017] Figure 4 The cross-sectional structure of a unit cell of a reflector of a radio wave reflecting device according to one embodiment of the present invention is shown.

[0018] Figure 5 The cross-sectional structure of a unit cell of a reflector of a radio wave reflecting device according to one embodiment of the present invention is shown.

[0019] Figure 6 The structure of a radio wave reflection device according to one embodiment of the present invention is shown.

[0020] Figure 7 The following diagram schematically shows how the traveling direction of a reflected wave changes due to a radio wave reflecting device according to one embodiment of the present invention.

[0021] Figure 8 The structure of a radio wave reflection device according to one embodiment of the present invention is shown.

[0022] Fig. 9 The cross-sectional structure of a unit cell of a reflector in a radio wave reflecting device according to one embodiment of the present invention is shown. DETAILED DESCRIPTION

[0023] Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings, etc. Among them, the present invention can be implemented in a plurality of different ways, and is not limited to the contents of the following embodiments and is explained. In order to make the description clearer, there is a case where the width, thickness, shape, etc. of each part are schematically shown in the accompanying drawings compared with the actual state, but it is only an example and does not limit the interpretation of the present invention. In addition, in this specification and each figure, sometimes the same figure mark (or the figure mark of a, b, etc. is marked after the number) is marked for the same element as the element mentioned above with respect to the figure that has appeared, and the detailed description is appropriately omitted. And the text marked as "the 1st" and "the 2nd" for each element is a convenient mark for distinguishing each element, and does not have any meaning other than this unless otherwise specified.

[0024] In this specification, when a certain component or region is located "on (or below)" other components or regions, unless otherwise specified, it includes not only the case where it is located directly above (or directly below) other components or regions, but also the case where it is located above (or below) other components or regions, that is, it also includes the case where it is above (or below) other components or regions and there are other structural elements in between.

[0025] <First embodiment>

[0026] 1. Reflector unit

[0027] Figure 1A and Figure 1B A reflector unit cell 102 used in the radio wave reflection device according to one embodiment of the present invention is shown. Figure 1A is a plan view of the reflector unit cell 102 when viewed from above (the side where the radio wave is incident). Figure 1B A cross-sectional view taken along line A1 - A2 shown in the plan view is shown.

[0028] like Figure 1A and Figure 1B As shown, the reflector unit cell 102 includes a substrate 104 and a substrate 106, a patch electrode 108, a common electrode 110, a first orientation film 112a, a second orientation film 112b, a liquid crystal layer 114, and a metal film 116. The patch electrode 108 is provided on the substrate 104, and the common electrode 110 is provided on the substrate 106. The patch electrode 108 and the common electrode 110 are arranged in an opposing manner, and a liquid crystal layer 114 is arranged between the patch electrode 108 and the common electrode 110. The first orientation film 112a is provided on the substrate 104 between the patch electrode 108 and the liquid crystal layer 114, and the second orientation film 112b is provided on the substrate 106 between the common electrode 110 and the liquid crystal layer 114.

[0029] The substrate 106 has a first surface 106a and a second surface 106b opposite to the first surface 106a. A common electrode 110 is provided on the first surface 106a, and a metal film 116 is provided on the second surface 106b. The metal film 116 is arranged on the side of the common electrode 110 opposite to the liquid crystal layer 114 side, and is arranged separately from the common electrode 110. At this time, the distance between the first surface 106a and the second surface 106b and / or the distance between the common electrode 110 and the metal film 116 is set to T. In addition, the metal film 116 is arranged in a manner overlapping with the patch electrode 108, and is formed to have an area equal to or larger than that of the common electrode 110.

[0030] The patch electrode 108 preferably has a shape that is symmetrical with respect to the vertically polarized wave and the horizontally polarized wave of the irradiated radio wave, and has a square or circular shape in planar view. Figure 1A The patch electrode 108 is shown to be square in plan view. The shape of the common electrode 110 is not particularly limited, and may be expanded on the substrate 106 to have a larger area than the patch electrode 108. The materials used for the patch electrode 108 and the common electrode 110 are formed using, for example, conductive metals, metal oxide films, and the like.

[0031] In addition, the substrate 104 may be provided with a first wiring 118, which is directly or electrically connected to the patch electrode 108. The first wiring 118 can be used to apply a control signal to the patch electrode 108. In addition, the first wiring 118 can be used to connect the patch electrode 108 to the adjacent patch electrode 108 when a plurality of reflector units are arranged.

[0032] Although in Figure 1A and Figure 1B Although not shown in the figure, the substrate 104 and the substrate 106 are bonded together by a sealing material. At this time, the interval between the substrate 104 and the substrate 106 is 20 to 100 μm, for example, 50 μm. Since the patch electrode 108, the common electrode 110, the first orientation film 112a, and the second orientation film 112b are provided between the substrate 104 and the substrate 106, the interval between the first orientation film 112a and the second orientation film 112b provided on the substrate 104 and the substrate 106 is the thickness of the liquid crystal layer 114. In addition, although Figure 1B Although not shown in the figure, a spacer for maintaining a fixed interval may be provided between the substrate 104 and the substrate 106 .

[0033] A control signal for controlling the orientation of the liquid crystal molecules of the liquid crystal layer 114 is applied to the patch electrode 108. The metal electrode 116 is supplied with a potential independently of the supply of these signals and is in a floating state. The control signal is a DC voltage signal, or a polarity reversal signal in which a positive DC voltage and a negative DC voltage are alternately reversed. A voltage of an intermediate level of the ground or polarity reversal signal is applied to the common electrode 110. The orientation state of the liquid crystal molecules contained in the liquid crystal layer 114 changes by applying a control signal to the patch electrode 108. A liquid crystal material having dielectric anisotropy is used for the liquid crystal layer 114. For example, as the liquid crystal layer 114, nematic liquid crystal, smectic liquid crystal, cholesterol liquid crystal, and disc-shaped liquid crystal can be used. The liquid crystal layer 114 having dielectric anisotropy changes its dielectric constant according to the change in the orientation state of the liquid crystal molecules. The reflector unit cell 102 can change the dielectric constant of the liquid crystal layer 114 according to the control signal applied to the patch electrode 108, thereby delaying the phase of the reflected wave when reflecting the radio wave.

[0034] The frequency band of the radio wave reflected by the reflector unit cell 102 is a very high frequency (VHF) band, an ultra-high frequency (UHF) band, a microwave (SHF) band, a submillimeter wave (THF) band, and a millimeter wave (EHF) band. The liquid crystal molecules of the liquid crystal layer 114 change their orientation in response to the control signal applied to the patch electrode 108, but they hardly follow the frequency of the radio wave irradiated to the patch electrode 108. Therefore, the reflector unit cell 102 can control the phase of the reflected radio wave without being affected by the radio wave.

[0035] Figure 2A The state (referred to as "first state") in which no voltage is applied between the patch electrode 108 and the common electrode 110 is shown. At this time, the metal film 116 is in a floating state. Figure 2A The first and second alignment films 112a and 112b are horizontal alignment films. In the first state, the long axes of the liquid crystal molecules 114a are aligned horizontally with respect to the surfaces of the patch electrode 108 and the common electrode 110 by the first and second alignment films 112a and 112b. Figure 2BThe state (referred to as "second state") in which a control signal (voltage signal) is applied to the patch electrode 108 is shown. Here, the metal film 116 is also in a floating state. In the second state, the liquid crystal molecules 114a are acted upon by the electric field and the long axis is oriented perpendicularly to the surface of the patch electrode 108 and the common electrode 110. The angle of the long axis orientation of the liquid crystal molecules 114a can also be oriented in a direction intermediate between the horizontal direction and the vertical direction according to the magnitude of the control signal applied to the patch electrode 108 (the magnitude of the voltage between the counter electrode and the patch electrode).

[0036] When the liquid crystal molecules 114a have positive dielectric anisotropy, the dielectric constant of the second state becomes larger than that of the first state. In addition, when the liquid crystal molecules 114a have negative dielectric anisotropy, the apparent dielectric constant of the second state becomes 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 reflector unit cell 102 can utilize the dielectric anisotropy of the liquid crystal layer 114 to control the phase of the reflected wave to be delayed (or not delayed).

[0037] The reflector unit cell 102 is a reflector for reflecting radio waves in a predetermined direction. The reflector unit cell 102 preferably has a high amplitude of reflected waves (reflection amplitude) and preferably completely reflects the radio waves irradiated to the reflector unit cell 102. However, although the common electrode 110 has the function of reflecting the radio waves irradiated to the patch electrode 108, there is a case where the common electrode 110 does not completely reflect the irradiated radio waves. Here, if Figure 1B As shown in the structure, a metal film 116 is provided on the side of the common electrode 110 opposite to the liquid crystal layer 114. In addition, the metal film 116 is arranged separately from the common electrode 110. By arranging the metal film 116 in this way, the radio waves that are not reflected by the common electrode 110 can be reflected by the metal film 116. Therefore, the reflector unit cell 102 can increase the amplitude of the reflected wave.

[0038] Moreover, if Figure 1BAs shown in the structure, a metal film 116 is provided at a fixed distance T on the side of the common electrode 110 opposite to the liquid crystal layer 114 side. By providing the metal film 116 in this way, the metal film 116 can be used to reflect the radio waves that are not reflected by the common electrode 110. However, since the radio waves irradiated to the patch electrode 108 are reflected by the common electrode 110 or the metal film 116, it is necessary to study the distance T between the common electrode 110 and the metal film 116 to avoid attenuation of the amplitude of the radio waves reflected by the common electrode 110 and the reflected waves of the radio waves reflected by the metal film 116. In addition, the substrate 106 can be provided between the common electrode 110 and the metal film 116, and the common electrode 110 can be provided on the liquid crystal layer 114 side of the substrate 106, and the metal film 116 can be provided on the opposite side. Therefore, the substrate 106 can be as shown in FIG. Figure 1B As shown in , the distance T represents the thickness of the substrate 106 . In addition, as described above, the thickness of the substrate 106 also needs to be considered.

[0039] Figure 3 The results of measuring the reflection amplitude relative to the distance T between the common electrode 110 and the metal film 116 are shown. Figure 3 The results of the measurements shown were obtained using Figure 1B The structure of the reflector unit cell 102 shown is grids 1 to 3. For the patch electrodes 108 and the common electrode 110 of the grids 1 to 3, aluminum with a film thickness of 1.0 μm is used, and for the metal film 116, aluminum (Al) with a film thickness of 1.0 μm is used. Regarding the size of the patch electrodes 108, a square with a side length of 2.80 mm is used for grid 1, a square with a side length of 2.85 mm is used for grid 2, and a square with a side length of 2.90 mm is used for grid 3. Glass substrates are used for substrates 104 and 106. The radio waves irradiated to the patch electrodes of grids 1 to 3 are set to a wavelength (λ) of 10.7 mm in air at a frequency of 28 GHz.

[0040] Here, a value obtained by multiplying the distance T between the common electrode 110 and the metal film 116 by the wavelength λ of the radio wave irradiated to the patch electrode 108 , that is, a distance T×λ is denoted as x.

[0041] The amplitude (dB) of the reflected wave was measured for grids 1 to 3 when x (distance T×λ) = 0.00 (distance T = 0.00 mm), 0.11 (distance T = 0.50 mm), and 0.22 (distance T = 1.00 mm). In the measurement of x = 0, a reflection unit cell without the metal film 116 was used. In addition, the reflection amplitude (amplitude of the reflected wave) was measured using a vector network analyzer (MS46522B, manufactured by ANRITSU Corporation).

[0042] according to Figure 3From the curve graph and Table 1 shown in FIG. 1 , it can be seen that the reflection amplitude varies depending on x. In addition, the reflection amplitude is preferably greater than -10 dB. Figure 3 From the graph and Table 1, it can be seen that when x (distance T×λ) is 0.11 and 0.22, a reflection amplitude of -10 dB or more is obtained in grids 1 to 3. In addition, according to the curve fitting obtained from the measurement results ( Figure 3 The dotted line shown in the figure shows that the x for obtaining a reflection amplitude of -10 dB or more is 0.02 to 0.34. Therefore, x is preferably 0.02 to 0.34, and more preferably 0.10 to 0.22. By setting the distance T in such a range of x, the reflector unit cell 102 can further increase the amplitude of the reflected wave.

[0043] [Table 1]

[0044]

[0045] Regarding metal film 116, Figure 4 An example in which a metal film 116 is provided on a substrate 117 is shown. Specifically, an example in which the substrate 117 is provided opposite to the substrate 104 on the substrate 106 side is shown. The metal film 116 is provided on the substrate 117, and the substrates 106 and 117 are bonded in such a manner that the metal film 116 is arranged between the substrates 106 and 117. By this bonding, the distance T between the common electrode 110 provided on the substrate 106 and the metal film 116 provided on the substrate 117 becomes the thickness of the substrate 106. The substrate 117 can use the same substrate as the substrates 104 and 106.

[0046] exist Figure 4 , an example is shown in which the metal film 116 is provided on the substrate 117 , but the substrate 117 only needs to have radio wave reflectivity. For example, a foil having radio wave reflectivity such as aluminum or aluminum alloy may be used instead of the substrate 117 having the metal film 116 .

[0047] In this way, by providing the metal film 116 on the substrate 117 different from the substrate 106 , the step of forming the metal film 116 can be performed simultaneously with the step of manufacturing the reflector unit cell 102 , thereby shortening the manufacturing time of the reflector unit cell 102 .

[0048] Figure 5 An example is shown in which the frame 119 holding the reflector unit cell 102 has the function of the metal film 116. Specifically, an example is shown in which the frame 119 made of a material having radio wave reflectivity is provided so that the reflector unit cell 102 and the substrate 106 face each other.

[0049] like Figure 5 As shown, frame 119 is as Figure 5As shown, the common electrode 110 is arranged on the side opposite to the liquid crystal layer 114 in a manner facing the substrate 106. In addition, the frame 119 holds the substrate 104 and the substrate 106. In addition, the frame 119 is provided with an opening 119a through which the radio waves irradiating the patch electrode 108 and the radio waves reflected by the common electrode 110 and the metal film 116 pass. The opening 119a is Figure 5 In the cross-sectional view, the width is larger than that of the patch electrode 108. Furthermore, when the frame 119 is used for the radio wave reflection devices 100a and 100b described later, a plurality of reflection plate units 102 are used, but the opening 119a is not provided in each reflection plate unit 102, but only needs to be provided for a certain number of reflection plate units 102 according to the size of the radio wave reflection devices 100a and 100b. However, the number of openings 119a is not limited.

[0050] As described above, by providing the frame 119 instead of the metal film 116, the step of forming the metal film 116 can be omitted in the manufacturing process of the radio wave reflection device 100. In addition, by providing the frame 119 having a thickness greater than the film thickness of the metal film 116, the amplitude of the reflected wave equal to or greater than that of the metal film 116 can be easily obtained.

[0051] According to this embodiment, by providing the liquid crystal layer 114 between the patch electrode 108 and the common electrode 110 and providing the metal film 116 on the common electrode 110 side opposite to the patch electrode 108 so as to overlap with the patch electrode 108, the amplitude of the reflected wave of the reflector unit cell 102 can be increased, and the reflection loss (attenuation rate with respect to the irradiated radio wave) with respect to the radio wave irradiated to the patch electrode 108 can be reduced. Therefore, the reflection gain of the radio wave reflection device 100 becomes higher.

[0052] Furthermore, according to this embodiment, by providing a metal film 116 on a substrate 117 different from the substrate 106 on which the common electrode 110 is provided, or providing a frame 119 having radio wave reflectivity, and making the metal film 116 or the frame 119 face the substrate 106, the frame 119 can be added to the reflector unit cell 102. By adding these, the manufacturing process of the reflector unit cell 102 can be simplified and the time can be shortened.

[0053] 2. Radio wave reflection device

[0054] Next, the structure of the radio wave reflecting device in which the reflecting plate unit is integrated is shown.

[0055] 2-1. Radio wave reflection device A (single-axis reflection control)

[0056] Figure 6FIG. 1 shows a structure of a radio wave reflection device 100a according to an embodiment of the present invention. The radio wave reflection device 100a includes a reflection plate 120. The reflection plate 120 is composed of a plurality of reflection plate cells 102. The plurality of reflection plate cells 102 are arranged in a first direction ( Figure 6 The X-axis direction shown in FIG. 1 ) and the second direction intersecting the first direction ( Figure 6 The reflector unit 102 is arranged in the Y-axis direction shown in FIG. 1 . The patch electrodes 108 are arranged in a matrix on the reflector unit 102 so that the patch electrodes 108 face the incident surface of the radio wave. The reflector 120 is in the form of a flat plate, and a plurality of patch electrodes 108 are arranged in a matrix on the surface of the flat plate.

[0057] The radio wave reflection device 100 has a structure in which a plurality of reflection plate units 102 are integrated on a substrate 104. Figure 6 As shown in FIG. 1 , the radio wave reflection device 100 has a structure in which a substrate 104 on which a plurality of patch electrodes 108 are arranged overlaps with a substrate 106 on which a common electrode 110 and a metal film 116 are provided, and a liquid crystal layer (not shown) is provided between the two substrates. In this case, the surface of the substrate 106 on which the common electrode 110 is provided faces the liquid crystal layer (not shown). The reflector 120 is formed in the area where the plurality of patch electrodes 108, the common electrode 110 and the metal film 116 overlap. When observed from the perspective of each patch electrode 108, the cross-sectional structure of the reflector 120 is similar to that of FIG. Figure 1B The structure of the reflector unit cell 102 shown is the same. Figure 6 In the figure, the metal film 116 is arranged on the inner side of the sealing material 128 and overlaps with the reflector 120 in a plan view, but it can be arranged to overlap with the reflector 120 as long as it is larger than the reflector 120, and it can also be arranged to expand outward compared with the sealing material 128. The substrate 104 and the substrate 106 are bonded together by the sealing material 128, and the liquid crystal layer (not shown) is provided in the area inside the sealing material 128.

[0058] In addition, the metal film 116 may not be provided, but Figure 5 As shown, a frame 119 (not shown) is provided. The frame 119 is provided so that the reflector 120 is exposed, and the opening 119a of the frame 119 overlaps with the reflector 120. The frame 119 (not shown) can be provided to protect and hold the structure mounted on the radio wave reflection device 100a. The frame 119 (not shown) surrounds the substrate 104 and the substrate 106, and is configured to clamp the substrate 104 and the substrate 106 in a cross-sectional view. At this time, the opening 119a of the frame 119 can be provided in single or multiple according to the size of the radio wave reflection device 100a or the patch electrode 108.

[0059] The substrate 104 has a peripheral region 122 that is expanded outward from the substrate 106 in addition to the region facing the substrate 106. The peripheral region 122 is provided with a first drive circuit 124 and a terminal portion 126. The first drive circuit 124 outputs a control signal to the patch electrode 108. The terminal portion 126 is a region where a connection with an external circuit is formed, and, for example, a flexible printed circuit substrate (not shown) is connected. A signal for controlling the first drive circuit 124 is input to the terminal portion 126.

[0060] As described above, a plurality of patch electrodes 108 are arranged along the first direction (X-axis direction) and the second direction (Y-axis direction) on the substrate 104. In addition, a plurality of first wirings 118 extending in the second direction (Y-axis direction) are arranged on the substrate 104. The plurality of first wirings 118 are electrically connected to the plurality of patch electrodes 108 arranged in the second direction (Y-axis direction), respectively. In other words, the plurality of patch electrodes 108 arranged in the second direction (Y-axis direction) are connected by the first wirings 118. The reflector 120 has a structure in which a plurality of rows of a row of patch electrode arrays connected by the first wirings 118 are arranged in the first direction (X-axis direction).

[0061] The plurality of first wirings 118 disposed on the reflector 120 extend to the peripheral region 122 and are connected to the first drive circuit 124. The first drive circuit 124 outputs a control signal applied to the patch electrode 108. The first drive circuit 124 can output control signals of different voltage levels to the plurality of first wirings 118. Thus, in the reflector 120, a control signal is applied to each column (each patch electrode 108 arranged in the second direction (Y-axis direction)) for the plurality of patch electrodes 108 arranged in the first direction (X-axis direction) and the second direction (Y-axis direction).

[0062] The radio wave reflection device 100a applies a control signal to each group of the plurality of patch electrodes 108 arranged along the second direction (Y-axis direction), thereby being able to control the reflection direction of the reflected wave of the radio wave incident on the reflection plate 120. That is, the radio wave reflection device 100a can control the traveling direction of the reflected wave in the left-right direction of the drawing with respect to the radio wave irradiated on the reflection plate 120, with respect to the reflection axis VR parallel to the second direction (Y-axis direction).

[0063] Figure 7The diagram schematically shows that the traveling direction of the reflected wave changes when passing through two reflector cells 102. The diagram shows that when the radio wave is incident on the first reflector cell 102a and the second reflector cell 102b with the same phase, the phase of the reflected wave of the second reflector cell 102b changes more than that of the first reflector cell 102a due to the application of different control signals (V1≠V2) to the first reflector cell 102a and the second reflector cell 102b. As a result, the phase of the reflected wave R1 reflected by the first reflector cell 102a is different from the phase of the reflected wave R2 reflected by the second reflector cell 102b (in Figure 7 The phase of the reflected wave R2 is ahead of the phase of the reflected wave R1), and apparently the traveling direction of the reflected wave changes in the inclined direction.

[0064] In addition, Figure 7 In the embodiment, the plurality of patch electrodes 108 arranged along the second direction (Y-axis direction) are electrically connected by the first wiring 118 and are electrically equipotential, so it is also considered that the patch electrodes 108 are not divided into a plurality of parts but replaced with a strip electrode continuous along the second direction (Y-axis direction). However, the size of the patch electrode 108 has an appropriate range depending on the wavelength of the reflected radio wave, so if the electrode is in a strip shape, the sensitivity is reduced with respect to the target wavelength, and the behavior with respect to the vertically polarized wave and the horizontally polarized wave is different. Therefore, if Figure 7 As shown, the patch electrode 108 is preferably set to a shape that is symmetrical with respect to the vertically polarized wave and the horizontally polarized wave ( Figure 7 The plurality of patch electrodes 108 are arranged in an array (shown as a square, but may also be a circle), and are configured to have a structure in which a plurality of patch electrodes 108 arranged parallel to the reflection axis RY are connected by a first wiring 118.

[0065] 2-2. Radio wave reflection device B (dual-axis reflection control)

[0066] The electric wave reflection device 100a shown in the second embodiment can control the reflection angle in the direction of the rotation axis with the reflection axis RY because the reflection axis RY is a single axis. In contrast, this embodiment shows an example of an electric wave reflection device 100b that can perform dual-axis reflection control. In the following description, the part different from the second embodiment is described as the center.

[0067] Figure 8 The structure of the radio wave reflection device 100b of this embodiment is shown. Figure 5 The description will focus on the different parts of the radio wave reflection device 100a shown.

[0068] The radio wave reflection device 100b has a plurality of second wirings 132 extending in the first direction (X-axis direction) in addition to a plurality of first wirings 118 extending in the second direction (Y-axis direction) on the reflector 120. The plurality of first wirings 118 and the plurality of second wirings 132 are arranged in a manner of crossing each other with an insulating layer not shown. The plurality of first wirings 118 are connected to the first drive circuit 124, and the plurality of second wirings 132 are connected to the second drive circuit 130. The first drive circuit 124 outputs a control signal, and the second drive circuit 130 outputs a scanning signal.

[0069] Figure 8 An inset diagram showing an enlarged arrangement of four patch electrodes 108, two first wirings 118, and a second wiring 132 is shown. A switch element 134 is provided on each of the four patch electrodes 108. The switching (on and off) of the switch element 134 is controlled by a scanning signal applied to the second wiring 132. The patch electrode 108 to which the switch element 134 is turned on is conducted with the first wiring 118 and a control signal is applied. The switch element 134 is formed of, for example, a thin film transistor. According to such a structure, by selecting a plurality of patch electrodes 108 arranged in the first direction (X-axis direction) by row, control signals of different voltage levels can be applied to each row.

[0070] Figure 8 The radio wave reflection device 100b shown can control the traveling direction of the reflected wave irradiated to the reflecting plate 120 in the left and right directions of the drawing with the reflection axis VR parallel to the second direction (Y-axis direction) as the center, and can also control the traveling direction of the reflected wave in the up and down directions of the drawing with the reflection axis HR parallel to the first direction (X-axis direction) as the center. That is, the radio wave reflection device 100 has the reflection axis VR parallel to the second direction (Y-axis direction) and the reflection axis VH parallel to the first direction (X-axis direction), so it is possible to control the reflection angle in the direction with the reflection axis VR as the rotation axis and the direction with the reflection axis HR as the rotation axis.

[0071] Fig. 9An example of a cross-sectional structure of a reflector unit cell 102 in which a switching element 134 is connected to a patch electrode 108 is shown. The switching element 134 is provided on a substrate 104. The switching element 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. A primer layer 136 may be provided between the first gate electrode 138 and the substrate 104. A first wiring 118 is provided between the first gate insulating layer 140 and the second gate insulating layer 146. The first wiring 118 is provided in a manner in contact with the semiconductor layer 142. In addition, a first connecting wiring 144 is provided in the same layer as the conductive layer forming the first wiring 118. The first connecting wiring 144 is provided in a manner in contact with the semiconductor layer 142. The connection structure of the first wiring 118 and the first connection wiring 144 to the semiconductor layer 142 shows a structure in which one wiring is connected to the source of the transistor and the other wiring is connected to the drain.

[0072] The first interlayer insulating layer 150 is provided so as to cover the switching element 134. The second wiring 132 is provided on the first interlayer insulating layer 150. The second wiring 132 is connected to the second gate electrode 148 via a contact hole formed in the first interlayer insulating layer 150. In addition, 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. On the first interlayer insulating layer 150, a second connection wiring 152 is provided in the same conductive layer as the second wiring 132. The second connection wiring 152 is connected to the first connection wiring 144 via a contact hole formed in the first interlayer insulating layer 150.

[0073] The second interlayer insulating layer 154 is provided so as to cover the second wiring 132 and the second connection wiring 152. Furthermore, a planarizing layer 156 is provided so as to fill the step difference of the switch element 134. By providing the planarizing layer 156, the patch electrode 108 can be formed without being affected by the arrangement of the switch element 134. A passivation layer 158 is provided on the flat surface of the planarizing layer 156. The patch electrode 108 is provided on the passivation layer 158. The patch electrode 108 is connected to the second connection wiring 152 via a contact hole penetrating the passivation layer 158, the planarizing layer 156, and the second interlayer insulating layer 154. A first orientation film 112a is provided on the patch electrode 108.

[0074] The substrate 106 and Figure 1BSimilarly, a common electrode 110 and a second orientation film 112b are provided, and a metal film 116 is provided on the second surface opposite to the first surface 106a provided with the common electrode 110. The distance T between the common electrode 110 and the metal film 116 can be set to the thickness of the substrate 106. The surface of the substrate 104 provided with the switching element 134 and the patch electrode 108 is arranged to face the surface of the substrate 106 provided with the common electrode 110, and the liquid crystal layer 114 is provided therebetween.

[0075] Each layer formed on the substrate 104 is formed using the following materials. The base coat 136 is formed, for example, of a silicon oxide film. The first gate insulating layer 140 and the second gate insulating layer 146 are formed, for example, of a silicon oxide film or a stacked structure of a silicon oxide film and a silicon nitride film. The semiconductor layer is formed of a silicon semiconductor such as amorphous silicon and polycrystalline silicon, and an oxide semiconductor containing metal oxides such as indium oxide, zinc oxide, and gallium oxide. The first gate electrode 138 and the second gate electrode 148 can be formed, for example, of molybdenum (Mo), tungsten (W), or an alloy thereof. The first wiring 118, the second wiring 132, the first connecting wiring 144, and the second connecting wiring 152 are formed using metal materials such as titanium (Ti), aluminum (Al), and molybdenum (Mo). For example, it can be composed of a stacked structure of titanium (Ti) / aluminum (Al) / titanium (Ti), or a stacked structure of molybdenum (Mo) / aluminum (Al) / molybdenum (Mo). The planarization layer 156 is formed of a resin material such as acrylic acid and polyimide. The passivation layer 158 is formed of, for example, a silicon nitride film, etc. The patch electrode 108 and the common 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).

[0076] like Figure 8 As shown, the second wiring 132 is connected to the gate of the transistor used as the switching element 134, the first wiring 118 is connected to one of the source and the drain of the transistor, and the patch electrode 108 is connected to the other of the source and the drain, thereby selecting a predetermined patch electrode from a plurality of patch electrodes 108 arranged in a matrix and applying a control signal. In addition, by providing the switching element 134 to each patch electrode 108 in the reflector 120, a control voltage can be applied 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). For example, when the reflector 120 is upright, the reflection direction of the reflected wave can be controlled in the left-right direction and the up-down direction.

[0077] As described above, the radio wave reflection device 100 of one embodiment of the present invention has a metal film 116 formed on the side of the common electrode 110 forming the reflection plate 120 opposite to the liquid crystal layer, and the value of the distance T between the common electrode 110 and the metal film 116 multiplied by the wavelength λ of the radio wave irradiated to the patch electrode 108 is set to be greater than 0.02 and less than 0.34 or greater than 0.10 and less than 0.22, thereby improving the reflection gain.

[0078] As one embodiment of the present invention, the various structures of the radio wave reflection device and the reflection plate unit illustrated can be appropriately combined as long as they do not contradict each other. In addition, based on the radio wave reflection device and the reflection plate unit disclosed in this specification and the drawings, the scheme obtained by the technicians in this field by adding, deleting or changing the design of the structural elements, or the scheme obtained by adding, omitting or changing the conditions of the process, as long as they have the gist of the present invention, is included in the scope of the present invention.

[0079] Even if there are other effects different from the effects brought about by the embodiments disclosed in this specification, the effects that are clear from the description of this specification or the effects that can be easily predicted by those skilled in the art are of course interpreted as being brought about by the present invention.

[0080] Description of Reference Numerals

[0081] 100: radio wave reflection device, 100a: radio wave reflection device, 100b: radio wave reflection device, 102: reflection plate unit cell, 102a: first reflection plate unit cell, 102b: second reflection plate unit cell, 104: substrate, 106: substrate, 106a: first surface, 106b: second surface, 108: patch electrode, 110: common electrode, 112a: first orientation film, 112b: second orientation film, 114: liquid crystal layer, 114a: liquid crystal molecules, 116: metal film, 117: substrate, 118: first wiring, 119: frame, 119a: switch Mouth, 120: reflecting plate, 122: peripheral area, 124: first driving circuit, 126: terminal portion, 128: sealing material, 130: second driving circuit, 132: second wiring, 134: switching element, 136: primer layer, 138: first gate electrode, 140: first gate insulating layer, 142: semiconductor layer, 144: first connecting wiring, 146: second gate insulating layer, 148: second gate electrode, 150: first interlayer insulating layer, 152: second connecting wiring, 154: second interlayer insulating layer, 156: planarization layer, 158: passivation layer.

Claims

1. An electric wave reflection device, comprising: Patch electrodes; Common electrode; a liquid crystal layer sandwiched by the patch electrode and the common electrode; and a metal film disposed on the side of the common electrode opposite to the liquid crystal layer side, The metal film is configured separately from the common electrode. The patch electrode is arranged to overlap with the metal film.

2. The radio wave reflection device according to claim 1, wherein: The value obtained by multiplying the distance T between the common electrode and the metal film by the wavelength λ of the radio wave irradiated to the patch electrode is set as x, The x is not less than 0.02 and not more than 0.

34.

3. The radio wave reflection device according to claim 2, wherein: The x is not less than 0.10 and not more than 0.

22.

4. The radio wave reflection device according to claim 1, wherein: The common electrode is applied with a ground potential, The metal film is in a floating state.

5. The radio wave reflection device according to claim 2, wherein: Also having a substrate, The common electrode is located on the first surface of the substrate. The metal film is located on a second surface of the substrate opposite to the first surface. The substrate has a thickness that is the same as the distance T.

6. The radio wave reflection device according to claim 1, wherein: The liquid crystal layer is sandwiched by the plurality of patch electrodes and the common electrode.

7. An electric wave reflection device, comprising: Patch electrodes; Common electrode; a liquid crystal layer sandwiched by the patch electrode and the common electrode; a first substrate; and The metal film on the first substrate, The metal film is arranged on the common electrode side opposite to the patch electrode. The patch electrode is arranged to overlap with the metal film.

8. The radio wave reflection device according to claim 7, wherein: The value obtained by multiplying the distance T between the common electrode and the metal film by the wavelength λ of the radio wave irradiated to the patch electrode is set as x, The x is not less than 0.02 and not more than 0.

34.

9. The radio wave reflection device according to claim 8, wherein: The x is not less than 0.10 and not more than 0.

22.

10. The radio wave reflection device according to claim 7, wherein: The common electrode is applied with a ground potential, The metal film is in a floating state.

11. The radio wave reflection device according to claim 8, wherein: further comprising a second substrate, The second substrate is located between the common electrode and the metal film. The second substrate has a thickness equal to the distance T.

12. A radio wave reflection device comprising: Patch electrodes; Common electrode; a liquid crystal layer sandwiched by the patch electrode and the common electrode; and A frame opposite to the patch electrode.

13. The radio wave reflection device according to claim 12, wherein: The value obtained by multiplying the distance T between the common electrode and the frame by the wavelength λ of the radio wave irradiated to the patch electrode is set as x, The x is not less than 0.02 and not more than 0.

34.

14. The radio wave reflection device according to claim 13, wherein: The x is not less than 0.10 and not more than 0.

22.

15. The radio wave reflection device according to claim 12, wherein: The common electrode is applied with a ground potential, The frame is in a floating state.

16. The radio wave reflection device according to claim 13, wherein: A substrate is also provided. The substrate is located between the common electrode and the frame. The substrate has a thickness that is the same as the distance T.

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