Radio wave reflecting device

Abstract

The radio wave reflection device includes: a first substrate including a patch electrode, a strip-shaped wiring connected to the patch electrode, and a transistor electrically connected to the strip-shaped wiring; a second substrate including a facing electrode facing the patch electrode; and a liquid crystal layer between the first substrate and the second substrate. The strip-shaped wiring includes a first linear portion located in the same direction as the vibration direction of a polarized wave incident on the patch electrode, and a second linear portion intersecting the vibration direction of the polarized wave.

Description

Technical Field

[0001] One embodiment of the present invention relates to the structure of a radio wave reflection device using liquid crystal. Background Art

[0002] A phased array antenna controls the directivity of the antenna by adjusting the amplitude and phase of the high-frequency signals applied to a plurality of antenna elements arranged in a planar shape, respectively. In a phased array antenna, a phase shifter is used to control the phase of the high-frequency signal. As an example, a phased array antenna device using a phase shifter that utilizes the phenomenon that the dielectric constant of liquid crystal changes according to the applied voltage is disclosed (see Patent Document 1).

[0003] In addition, a radio wave reflection device that uses liquid crystal to control the reflection direction of radio waves in the same manner as a phased array antenna is known. For example, a radio wave reflector is disclosed, which forms a metasurface that reflects radio waves using a microstrip patch array sandwiching a liquid crystal layer (see Patent Document 2).

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Laid-Open No. 11-103201

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2019-530387 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] The radio wave reflection device disclosed in Patent Document 2 has a structure in which a liquid crystal layer is provided between a patch electrode and a counter electrode. The direction in which the radio wave reflection device reflects radio waves is controlled by the voltage applied to the patch electrode. In order to apply a bias voltage, a strip wiring is connected to the patch electrode. However, sometimes the reflection characteristics deteriorate due to the connection of the strip wiring to the patch electrode, which becomes a problem.

[0010] An object of one embodiment of the present invention is to provide a radio wave reflection device that can maintain the radio wave reflection characteristics well.

[0011] Means for Solving the Problems

[0012] A radio wave reflection device according to an embodiment of the present invention includes: a first substrate including a patch electrode, a strip wiring connected to the patch electrode, and a transistor electrically connected to the strip wiring; a second substrate including a counter electrode opposed to the patch electrode; and a liquid crystal layer between the first substrate and the second substrate, wherein the strip wiring includes a first straight portion located in the same direction as the vibration direction of the polarized wave incident on the patch electrode and a second straight portion crossing the vibration direction of the polarized wave. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1A is a top view showing a unit cell constituting a radio wave reflection device according to an embodiment of the present invention.

[0014] Figure 1B is a cross-sectional view showing a unit cell constituting a radio wave reflection device according to an embodiment of the present invention.

[0015] Figure 2 is a top view showing a unit cell constituting a radio wave reflection device according to an embodiment of the present invention.

[0016] Figure 3 is a top view showing a unit cell constituting a radio wave reflection device according to an embodiment of the present invention.

[0017] Figure 4 is a top view showing a unit cell constituting a radio wave reflection device according to an embodiment of the present invention.

[0018] Figure 5 is a top view showing the configuration of a radio wave reflection device according to an embodiment of the present invention.

[0019] Figure 6 is a cross-sectional view showing the configuration of a radio wave reflection device according to an embodiment of the present invention.

[0020] Figure 7 is a top view showing the structure of a unit cell with different connection positions of the strip wiring. DETAILED DESCRIPTION OF THE INVENTION

[0021] ​​​​​​​​Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention can be implemented in various different ways and should not be construed as being limited to the embodiments illustrated below. For the sake of clarity in the description, the lengths, widths, shapes, etc. of the respective parts are sometimes schematically shown in the drawings as compared with the actual form. However, this is an example for illustration and does not limit the interpretation of the present invention. In addition, in this specification and each drawing, sometimes the same reference signs (or signs such as a, b, etc. are appended after the numbers) are given to the elements that are the same as those already described with respect to the previously presented drawings, and the detailed description is appropriately omitted. Furthermore, the words marked as "first", "second", etc. for each element are convenient identifiers used to distinguish the elements and do not have any more meaning unless otherwise specified.

[0022] In this specification, when a certain member or region is "above (or below)" another member or region, unless otherwise particularly limited, it includes not only the case where it is directly above (or directly below) the other member or region, but also the case where it is above (or below) the other member or region, that is, it also includes the case where other constituent elements are included therebetween above (or below) the other member or region.

[0023] Figure 1A It shows a top view when observing the unit cell 101 constituting the radio wave reflection device of this embodiment from the front (the surface where radio waves are incident). Figure 1B It shows the Figure 1A longitudinal sectional view corresponding to the A - B line shown.

[0024] As Figure 1A and Figure 1B shown, the unit cell 101 includes a patch electrode 102, a counter electrode 104 (also referred to as a "ground electrode") disposed on the back surface of the patch electrode 102, a liquid crystal layer 110 between the patch electrode 102 and the counter electrode 104, and a transistor 108. The patch electrode 102 is provided on the first substrate 150, and the counter electrode 104 is provided on the second substrate 152. A first alignment film 112A is provided on the first substrate 150 so as to cover the patch electrode 102, and a second alignment film 112B is provided on the second substrate 152 so as to cover the counter electrode 104. The first substrate 150 and the second substrate 152 are arranged such that the patch electrode 102 and the counter electrode 104 face each other with a gap therebetween. The liquid crystal layer 110 is provided so as to fill the gap between the first substrate 150 and the second substrate 152. In addition, the transistor 108 is connected to a control signal line 114 and a selection signal line 116 provided on the first substrate 150.

[0025] Although in Figure 1BAlthough not shown, the first substrate 150 and the second substrate 152 are bonded together by a sealing material. The distance (cell gap) between the first substrate 150 and the second substrate 152 is 20 to 100 μm, for example, having a distance (cell gap) of 50 μm. A spacer for maintaining a constant distance may be provided between the first substrate 150 and the second substrate 152.

[0026] Figure 1A This shows an example where the patch electrode 102 is square. The shape of the patch electrode 102 when viewed from above is not limited and may also be rectangular, circular, elliptical, or a polygon with more sides than a quadrilateral. For example, the patch electrode 102 may also have a shape in which a part of the corners of a rectangle are cut off.

[0027] As Figure 1A shown, the patch electrode 102 has a first side 1021 and a third side 1023 located in the same direction as the first direction (in other words, a parallel or substantially parallel direction), and a second side 1022 and a fourth side 1024 located in the same direction as the second direction (in other words, a parallel or substantially parallel direction). The lengths of these sides are appropriately set according to the frequency (wavelength) of the radio wave applied to the radio wave reflection device. In addition, the shape of the patch electrode 102 is not limited to a square, and for the purpose of finely adjusting the reflection characteristics, the lengths of the first side 1021 and the third side 1023 may be different from the lengths of the second side 1022 and the fourth side 1024.

[0028] It should be noted that for ease of explanation, the first direction refers to the direction along Figure 1A the Y-axis shown, and the second direction refers to the direction along Figure 1A the X-axis shown. Therefore, the first direction and the second direction are in a cross (preferably orthogonal or substantially orthogonal) relationship.

[0029] The counter electrode 104 has an area larger than that of the patch electrode 102. The materials for forming the patch electrode 102 and the counter electrode 104 are not limited, and a simple metal, an alloy, or a conductive metal compound (for example, a conductive metal oxide) may be used.

[0030] The control signal line 114 extends in the first direction, and the selection signal line 116 extends in the second direction. The transistor 108 is disposed near the intersection of the control signal line 114 and the selection signal line 116. The transistor 108 is, for example, a thin film transistor. The structure of the transistor 108 is not limited, and various structures such as a top gate type and a bottom gate type may be applied. It should be noted that in Figure 1A the transistor 108 is represented by a circuit symbol.

[0031] The transistor 108 has a control terminal (gate), a first input / output terminal (one of the source and the drain), and a second input / output terminal (the other of the source and the drain). The control terminal (gate) of the transistor 108 is electrically connected to the selection signal line 116, the first terminal (one of the source and the drain) is connected to the control signal line 114, and the second terminal (the other of the source and the drain) is connected to the strip wiring 106.

[0032] It should be noted that when referring to one or the other of the source and the drain, when one corresponds to the source, the other corresponds to the drain, and when one corresponds to the drain, the other corresponds to the source.

[0033] The strip wiring 106 is formed of a thin linear conductive pattern extending from the patch electrode 102. Figure 1A It shows a structure in which one end of the strip wiring 106 is connected to the second side 1022 of the patch electrode 102 and the other end is connected to the transistor 108. As Figure 1A shown in the enlarged view inserted therein, the strip wiring 106 includes a first straight portion 1061 extending in the first direction from the connection portion with the patch electrode 102 and a second straight portion 1062 extending in the second direction from the first straight portion 1061. The first straight portion 1061 and the second straight portion 1062 are continuous conductive patterns. In the strip wiring 106, the end of the first straight portion 1061 is connected to the second side 1022 of the patch electrode 102, and the end of the second straight portion 1062 is electrically connected to the transistor 108. There is no limitation on the length of the strip wiring 106, and it preferably has a length of 1 / 2 times or 1 / 4 times the wavelength of the reflected radio wave. When the length of the first straight portion 1061 of the strip wiring 106 is set as L1 and the length of the second straight portion 1062 is set as L2, the length L2 of the second straight portion 1062 is longer than the length L1 of the first straight portion 1061.

[0034] A control signal for controlling the alignment state of the liquid crystal molecules of the liquid crystal layer 110 is applied to the control signal line 114, and a selection signal for making the transistor 108 conductive and non-conductive is applied to the selection signal line 116. When the transistor 108 is made conductive by the selection signal on the selection signal line 116, a prescribed voltage based on the control signal is applied to the patch electrode 102 via the transistor 108 from the control signal line 114.

[0035] The control signal applied to the patch electrode 102 is a DC voltage signal, or a polarity inversion signal in which a positive DC voltage and a negative DC voltage are alternately inverted. The counter electrode 104 is grounded, or is applied with a voltage at an intermediate level of the polarity inversion signal. By applying a control signal to the patch electrode 102, the alignment state of the liquid crystal molecules contained in the liquid crystal layer 110 changes. The liquid crystal layer 110 uses a liquid crystal material having dielectric anisotropy. For example, as the liquid crystal layer 110, nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal, or discotic liquid crystal is used.

[0036] By making the liquid crystal layer 110 have dielectric constant anisotropy, the dielectric constant changes according to the alignment state of the liquid crystal molecules. The radio wave reflection device changes the dielectric constants of the liquid crystal layer 110 respectively according to the control signals applied to the plurality of patch electrodes 102 arranged in a matrix, thereby changing the phase of the reflected wave to control the traveling direction of the reflected wave.

[0037] The frequency band of the radio wave reflected by the radio wave reflection device is the very high frequency (VHF) band, the ultra-high frequency (UHF) band, the super high frequency (SHF) band, the terahertz wave (THF) band, the millimeter wave (EHF) band, and the terahertz wave frequency band. The liquid crystal molecules of the liquid crystal layer 110 change their alignment state in response to the control signal applied to the patch electrode 102. However, they hardly follow the frequency of the radio wave incident on the patch electrode 102. Therefore, the radio wave reflection device can control the traveling direction of the reflected wave without being affected by the radio wave.

[0038] As described later, the radio wave reflection device has a configuration in which the unit cells 101 are arranged in a matrix, and has the function of reflecting linearly polarized waves (vertical polarized waves and horizontal polarized waves) and circularly polarized waves, and controlling the traveling direction of the reflected wave. Figure 1A This represents the case where the vibration direction of the incident linearly polarized wave is the same as the first direction (in other words, the parallel or substantially parallel direction) (the case of a vertical polarized wave). As Figure 1AAs shown, with respect to the vibration direction of the vertically polarized wave, the first side 1021 and the third side 1023 of the patch electrode 102 extend in the same direction (in other words, parallel or substantially parallel), and the second side 1022 and the fourth side 1024 intersect (preferably orthogonally or substantially orthogonally). In the strip wiring 106, the direction of the first straight portion 1061 is the same as the vibration direction of the vertically polarized wave (in other words, parallel or substantially parallel), and the second straight portion 1062 intersects the vibration direction of the vertically polarized wave (preferably orthogonally or substantially orthogonally).

[0039] As Figure 1A shown, it is known that if a vertically polarized wave is incident on the patch electrode 102, the density of the current generated in the patch electrode 102 becomes higher in the direction same as the vibration direction of the vertically polarized wave and near the ends of the patch electrode 102 (the regions along the first side 1021 and the third side 1023). When the vibration direction of the vertically polarized wave is in the same direction as the first direction (in other words, a parallel or substantially parallel direction), the current density of the first side 1021 and the third side 1023 of the patch electrode 102 is higher than that in other regions. Figure 1A Schematically shows the state where regions 1601 and 1602 with high current density are generated near the first side 1021 and the third side 1023. In the regions 1601 and 1602 with high current density, the current Ip flows in the same direction as the first direction (in other words, a parallel or substantially parallel direction).

[0040] Figure 7 Shows a reference example of the unit cell 301. With respect to Figure 1A the unit cell 101 shown, an example is shown where the structure and connection position of the strip wiring 306 are different. In the unit cell 301, the strip wiring 306 is connected to the corner where the first side 1021 and the second side 1022 of the patch electrode 102 intersect and extends in an inclined direction to be connected to the transistor 108. That is, the strip wiring 306 extends from the corner of the patch electrode 102 at an angle of 45 degrees in the direction of the transistor 108.

[0041] If a vertically polarized wave is incident on such a unit cell 301, then compared with Figure 1ASimilarly, in the example shown, high-current-density regions 1601 and 1602 are generated near the ends of the patch electrode 102 along the first side 1021 and the third side 1023. The strip wiring 306 is connected in such a way as to be directly connected to the high-current-density region 1601 among the patch electrodes 102. Therefore, the current Ip in the high-current-density region 1601 flows into the strip wiring 306. As a result, the intensity of the vertically polarized wave reflected with respect to the vertically polarized wave incident on the unit cell 301 is reduced. It is possible to consider dividing the current Ips flowing in the strip wiring 306 into a component in the same direction as the first direction (in other words, parallel or substantially parallel) and a component in the same direction as the second direction (in other words, parallel or substantially parallel direction). The presence of the current component in the same direction as the second direction (in other words, parallel or substantially parallel direction) means that a horizontally polarized wave is included in the reflected wave. In this way, the difference between the vertically polarized wave (main polarized wave) and the horizontally polarized wave (cross-polarized wave) becomes smaller, and good reflection characteristics cannot be obtained.

[0042] Table 1 shows the Figure 1A electromagnetic wave reflection device constituted by the unit cell 101 of the present embodiment shown (the connection of the strip wiring is at the central part of one side of the patch electrode), and the difference in received power between the main polarized wave and the cross-polarized wave of the electromagnetic wave reflection device constituted by the unit cell 301 shown as a reference example in Figure 7 . Figure 7 The electromagnetic wave reflection device shown has a structure in which the connection part of the strip wiring is provided at the end of the patch electrode. In Table 1, the liquid crystal applied voltage V0 represents the case of 0 V, and V1 represents the case of a voltage higher than V0. It should be noted that this measurement is performed by irradiating the electromagnetic wave reflection device with an electromagnetic wave and detecting the intensity of its reflected wave using a receiver. Regarding the electromagnetic wave reflection device constituted by the unit cell 301, a tendency was observed that the difference in received power between the main polarized wave and the cross-polarized wave becomes smaller according to the liquid crystal applied voltage. It is considered that the reason is that the received power of the unnecessary cross-polarized wave increases depending on the liquid crystal applied voltage, and it is judged that the reflection characteristics of the electromagnetic wave reflection device deteriorate. On the other hand, in the electromagnetic wave reflection device constituted by the unit cell 101, as a result, no large change was observed in the difference in received power between the main polarized wave and the cross-polarized wave regardless of the liquid crystal applied voltage. It is considered that this is because the generation of unnecessary cross-polarized waves is suppressed, and it is judged that good reflection characteristics are obtained.

[0043] [Table 1]

[0044]

[0045] In Figure 1AIn the unit cell 101 shown, the connection portion of the strip wiring 106 is located near the center of the second side 1022 of the patch electrode 102, and is set at a position where current does not directly flow from the high-current-density regions 1601 and 1602. The results in Table 1 show that with such a configuration, it is possible to prevent a reduction in the current generated by the vertically polarized wave, suppress the attenuation of the incident vertically polarized wave, increase the difference between the vertically polarized wave (main polarized wave) and the horizontally polarized wave (cross-polarized wave), and obtain good reflection characteristics.

[0046] The connection portion between the patch electrode 102 and the strip wiring 106 is preferably located at a position far from the high-current-density regions 1601 and 1602 and at the midpoint of the second side 1022 of the patch electrode 102. It should be noted that even if the connection position of the strip wiring 106 is slightly away from the midpoint of the second side 1022 of the patch electrode 102, the same effect can be expected. That is, in the second side 1022 of the patch electrode 102, as long as it is at a position that is at a distance DXL from the end of this side, the same effect can be expected. In other words, it can be said that it is preferable for the strip wiring 106 to be connected to the vicinity of the center of a side that intersects (preferably orthogonally or approximately orthogonally) the polarization direction (main polarized wave) of the radio wave in the patch electrode 102. Here, regarding the length DXL, it is preferably about one-fourth to one-fifth of the total length XL of the second side 1022 of the patch electrode 102.

[0047] As Figure 1A shown, when a vertically polarized wave is incident on the patch electrode 102, by connecting the strip wiring 106 to the second side 1022 that intersects the vibration direction of the vertically polarized wave, the attenuation of the reflected vertically polarized wave can be suppressed. In other words, when a linearly polarized wave is incident on the patch electrode 102, by connecting the strip wiring 106 at a position away from the end of the side that intersects the vibration direction of the linearly polarized wave, the current generated near the side of the patch electrode 102 in the same direction (in other words, the parallel or approximately parallel direction) as the vibration direction of the linearly polarized wave can be prevented from flowing into the strip wiring 106, and the attenuation of the reflected linearly polarized wave can be prevented.

[0048] Figure 2 Indicates with respect to Figure 1A the configuration shown, an example of a unit cell 101 with different connection positions of the strip wiring 106. Figure 2 And Figure 1A shown in the example, the vibration direction of the vertically polarized wave is the same direction as the first direction (in other words, the parallel or approximately parallel direction), and the strip wiring 106 is connected to the first side 1021 that is in the same direction as the vibration direction of the vertically polarized wave (in other words, the parallel or approximately parallel direction). As Figure 2As shown in the enlarged view inserted therein, the strip wiring 106 includes a first straight portion 1061 extending in the second direction from the connection portion with the patch electrode 102, and a second straight portion 1062 extending in the first direction from the first straight portion 1061. In the strip wiring 106, the end of the first straight portion 1061 is connected to the first side 1021 of the patch electrode 102, and the end of the second straight portion 1062 is electrically connected to the transistor 108. When the length of the first straight portion 1061 of the strip wiring 106 is set as L1 and the length of the second straight portion 1062 is set as L2, L1 is shorter than L2. There is no limitation on the length of the strip wiring 106, and it preferably has a length of 1 / 2 times or 1 / 4 times the wavelength of the reflected radio wave. In addition, the connection position of the strip wiring 106 with the first side 1021 of the patch electrode 102 is preferably a position departing from the end of the first side 1021 by a length DYL, and the length DYL is preferably about one-fourth to one-fifth of the total length YL of the first side 1021 of the patch electrode 102.

[0049] As Figure 2 shown, if a vertically polarized wave is incident on the patch electrode 102, regions with high current density are generated near the first side 1021 and the third side 1023. In the strip wiring 106, the first straight portion 1061 extends in the second direction, while the current Ip in the region 1601 with high current density flows in the first direction. The strip wiring 106 is connected to the region 1603 with high current density, but since the current Ip flows in the first direction, the current flowing into the first straight portion 1061 extending in the second direction becomes less. Even if a small amount of current flows from the region 1601 with high current density into the strip wiring 106, since the first straight portion 1061 intersecting the first direction is shorter and the second straight portion 1062 extending in the same direction as the first direction (in other words, parallel or substantially parallel direction) is longer, the influence of the horizontally polarized wave (cross-polarized wave) on the vertically polarized wave (main polarized wave) becomes smaller, and good reflection characteristics can be obtained.

[0050] Figure 3 Indicates the case where a horizontally polarized wave is incident as the main polarized wave in the same configuration as the unit cell 101 Figure 1A shown. That is, it indicates the case where the vibration direction of the polarized wave incident on the patch electrode 102 is in the same direction as the second direction (in other words, parallel or substantially parallel direction). In this case, regions 1603 and 1604 with high current density are generated near the second side 1022 and the fourth side 1024 of the patch electrode 102.

[0051] The strip wiring 106 is connected near the center of the second side 1022 of the patch electrode 102. As Figure 3As shown, in the strip wiring 106, the first straight portion 1061 extends in the first direction. In contrast, the current Ip in the region 1603 with a high current density flows in the second direction. And Figure 2 Similar to the example shown, the strip wiring 106 is connected to the region 1603 with a high current density, but since the current Ip flows in the second direction, the current flowing in the first straight portion 1061 becomes less.

[0052] As Figure 3 shown, by connecting the strip wiring 106 to one side in the same direction as the vibration direction of the polarized wave (in other words, the parallel or substantially parallel direction) and at the central portion of this side, it is also possible to suppress the reduction of the current generated in the patch electrode 102 due to the incidence of the polarized wave, where the strip wiring 106 forms a current path in a direction crossing (preferably orthogonal or substantially orthogonal) the vibration direction of the polarized wave. In addition, even if current flows into the strip wiring 106, since the second straight portion 1062 is longer than the first straight portion 1061 and extends in the same direction as the second direction (in other words, the parallel or substantially parallel direction), the current flows in the same direction (in other words, the parallel or substantially parallel direction) as the current Ip flowing in the patch electrode 102, so the effect of suppressing the attenuation of the reflected horizontally polarized wave can be expected.

[0053] It should be noted that although not shown, in the Figure 3 configuration shown, when the strip wiring 106 is connected to the first side 1021, the same effects as those of the Figure 1A configuration described with reference to can be obtained.

[0054] Figure 4 shows a manner in which a strip wiring 106B having a zigzag pattern is connected to the patch electrode 102. That is, the strip wiring 106B has a structure in which the portion corresponding to the first straight portion 1061 includes a plurality of first straight portions 1061, and the portion corresponding to the second straight portion 1062 includes a plurality of second straight portions 1062, and they are alternately arranged. The length of the strip wiring 106 preferably has a length of 1 / 2 times or 1 / 4 times the wavelength of the reflected radio wave. As Figure 4 shown, by the strip wiring 106B having a zigzag pattern, the wiring length can be freely adjusted in a limited area.

[0055] As Figure 4 shown, the strip wiring 106B can also be applied to the Figure 2 and Figure 3 unit cell 101 shown.

[0056] Figure 5A radio wave reflection device 100 in which unit cells 101 are arranged in a matrix in a first direction and a second direction. The radio wave reflection device 100 has the following structure: a first substrate 150 on which patch electrodes 102 are arranged and a second substrate 152 on which counter electrodes 104 are arranged are arranged to face each other, and a liquid crystal layer 110 (not shown) is provided therebetween. A transistor 108, a control signal line 114, and a selection signal line 116 are provided on the first substrate 150. The control signal line 114 and the selection signal line 116 are arranged to cross each other with an insulating layer (not shown) therebetween, and a transistor 108 is provided at the crossing portion. The first substrate 150 and the second substrate 152 are bonded by a sealing material arranged so as to surround a region where a plurality of patch electrodes 102 are arranged. The liquid crystal layer 110 (not shown) is enclosed in a region surrounded by the sealing material 118.

[0057] The radio wave reflection device 100 has a radio wave reflection surface 120. The radio wave reflection surface 120 has the following structure: a plurality of patch electrodes 102 are arranged on the incident side of the radio wave, and the counter electrodes 104 are arranged on the back side of the plurality of patch electrodes 102 with the liquid crystal layer 110 (not shown) therebetween. On the first substrate 150, a first drive circuit 122, a second drive circuit 124, and a terminal portion 126 are provided in a region outside the reflection surface 120. The first drive circuit 122 outputs a selection signal to the selection signal line 116, and the second drive circuit 124 outputs a control signal to the control signal line 114. The terminal portion 126 is a region for forming a connection with an external circuit, and a plurality of terminal electrodes 127 are arranged along an end portion of the first substrate 150. A flexible printed circuit board (not shown) is connected to the terminal portion 126, and signals and power for driving the first drive circuit 122 and the second drive circuit 124 are input from an external circuit.

[0058] The patch electrode 102 is electrically connected to the transistor 108 through a strip wiring 106. The connection between the patch electrode 102 and the strip wiring 106 is the same as the structure shown in Figure 1A In addition, the connection between the patch electrode 102 and the strip wiring 106 can also be replaced with the structures shown in Figure 2 , Figure 3 and Figure 4 The switching (switching between an on state and an off state) of the transistor 108 is controlled by a selection signal applied to the selection signal line 116. If the transistor 108 becomes in an on state, a voltage based on the control signal is applied from the control signal line 114 to the patch electrode 102. The plurality of patch electrodes 102 are respectively applied with a voltage based on the control signal via the transistor 108.

[0059] By applying voltages based on a prescribed control signal to the plurality of patch electrodes 102 respectively, the alignment state of the liquid crystal can be controlled for each unit cell 101 forming the reflecting surface 120. As a result, the radio wave (linearly polarized wave) incident on the reflecting surface 120 can be reflected in the left - right direction of the drawing with the reflection axis VR located in the same direction as the first direction (in other words, parallel or substantially parallel), and can also be reflected in the up - down direction of the drawing with the reflection axis HR located in the same direction as the second direction (in other words, parallel or substantially parallel). That is, the radio wave reflecting device 100 has a reflection axis VR located in the same direction as the first direction (in other words, parallel or substantially parallel) and a reflection axis VH located in the same direction as the second direction (in other words, parallel or substantially parallel). Therefore, the reflection angle can be controlled in the direction with the reflection axis VR as the rotation axis, the direction with the reflection axis HR as the rotation axis, and the inclined direction formed by combining them.

[0060] Figure 6 FIG. shows an example of a cross - sectional structure of a radio wave reflecting device 100 in which a transistor 108 is connected to a patch electrode 102. A transistor 108 and a patch electrode 102 are provided on a first substrate 150, and a counter electrode 104 is provided on a second substrate 152. The transistor 108 has a structure in which a first gate electrode 132, a first gate insulating layer 133, a semiconductor layer 134, a second gate insulating layer 137, and a second gate electrode 138 are stacked. A base insulating layer 130 may be provided between the first gate electrode 132 and the first substrate 150. A first input / output electrode 135 and a second input / output electrode 136 in contact with the semiconductor layer 134 are provided between the first gate insulating layer 133 and the second gate insulating layer 137.

[0061] A first interlayer insulating layer 139 is provided so as to cover the transistor 108. A control signal line 114 is provided on the first interlayer insulating layer 139. The control signal line 114 is connected to the first input / output electrode 135 through a contact hole penetrating the first interlayer insulating layer 139 and the second gate insulating layer 137. In addition, a connection wiring 140 is provided on the first interlayer insulating layer 139 and is connected to the second input / output electrode 136. Although not shown, the first gate electrode 132 is connected to a selection signal line 116 (not shown) formed of the same conductive layer. In addition, the second gate electrode 138 is connected to the first gate electrode 132 in a region not overlapping with the semiconductor layer 134.

[0062] A second interlayer insulating layer 141 is provided so as to cover the control signal line 114 and the connection wiring 140. In addition, a planarization layer 142 is provided so as to fill the step difference formed by the transistor 108. A passivation layer 143 is provided on the planarization layer 142, and a patch electrode 102 and a strip wiring 106 are provided on the passivation layer 143. The patch electrode 102 and the strip wiring 106 are formed of the same conductive layer. Figure 4 It represents a structure in which the strip wiring 106 is continuous from the patch electrode 102. The strip wiring 106 extends from the patch electrode 102 to the transistor 108, and is connected to the connection wiring 140 through a contact hole penetrating the passivation layer 143, the planarization layer 142, and the second interlayer insulating layer 141. In other words, the strip wiring 106 and the patch electrode 102 are provided on the same insulating layer (in Figure 4 the example shown, provided on the passivation layer 143), and the strip wiring 106 is connected to the transistor 108 via the contact hole.

[0063] A counter electrode 104 is provided on the second substrate 152. A first alignment film 112A is provided on the patch electrode 102 and the strip wiring 106, and a second alignment film 112B is provided on the counter electrode 104. A liquid crystal layer 110 is provided between the first substrate 150 and the second substrate 152.

[0064] The layers formed on the first substrate 150 are formed of the following materials. The base insulating layer 130 is formed of, for example, a silicon oxide film. The first gate insulating layer 133 and the second gate insulating layer 137 are formed of, for example, a silicon oxide film or a laminate of a silicon oxide film and a silicon nitride film. The semiconductor layer 134 is formed of a silicon semiconductor such as amorphous silicon or polycrystalline silicon, or an oxide semiconductor containing metal oxides such as indium oxide, zinc oxide, and gallium oxide. The first gate electrode 132 and the second gate electrode 138 can be formed of, for example, molybdenum (Mo), tungsten (W), or their alloy. The first input / output electrode 135, the second input / output electrode 136, the control signal line 114, and the connection wiring 140 are formed of a metal material such as titanium (Ti), aluminum (Al), or molybdenum (Mo). For example, they are formed of a laminate structure of titanium (Ti) / aluminum (Al) / titanium (Ti) or a laminate structure of molybdenum (Mo) / aluminum (Al) / molybdenum (Mo). The first interlayer insulating layer 139 and the second interlayer insulating layer 141 are formed of a silicon oxide film, a silicon oxynitride film, etc., and the passivation layer 143 is formed of a silicon nitride film. The planarization layer 142 is formed of a resin material such as acrylic or polyimide. The patch electrode 102, the strip wiring 106, and the counter electrode 104 are formed of a metal film such as aluminum (Al) or copper (Cu), or a transparent conductive film such as indium tin oxide (ITO).

[0065] As Figure 6As shown, by applying a selection signal to the first gate electrode 132 and the second gate electrode 138, the transistor 108 is turned on, and the control signal line 114 can be made conductive with the patch electrode 102 via the transistor 108. Further, by applying a voltage based on a control signal from the control signal line 114 to the patch electrode 102, the alignment state of the liquid crystal molecules in the liquid crystal layer 110 can be controlled. As a result, the dielectric constant of the liquid crystal layer 110 in the region sandwiched between the patch electrode 102 and the counter electrode 104 can be changed, and the phase of the reflected wave with respect to the electric wave (linearly polarized wave) incident from the first substrate 150 side can be controlled.

[0066] At this time, as described with reference to Figure 1A as described above, the strip wiring 106 is connected to one side of the patch electrode 102 and has a first straight portion 1061 and a second straight portion 1062, so that it is possible to suppress the direct inflow of the current generated at the side of the patch electrode 102 in the same direction as the vibration direction of the linearly polarized wave (in other words, the parallel or substantially parallel direction) into the transistor 108, and to suppress the attenuation of the reflected wave.

[0067] As described above, the radio wave reflection device 100 according to an embodiment of the present invention has a reflection surface 120 on which a plurality of patch electrodes 102 are arranged, and the current generated by the polarized wave does not directly flow into the strip wiring 106 for each patch electrode 102. Therefore, the difference between the polarization direction (main polarized wave) of the radio wave and the polarized wave (cross polarized wave) intersecting the main polarized wave can be increased, and good reflection characteristics can be obtained. According to such characteristics, even when a plurality of radio wave reflection devices 100 are combined to form a transmission path in the air, attenuation of the polarized wave can be suppressed, and good communication can be performed by the communication device.

[0068] It should be noted that, in the present embodiment, the case where the radio wave reflection device 100 reflects a linearly polarized wave (vertical polarized wave, horizontal polarized wave) has been described, but the same effects as those described above can also be obtained in the case of reflecting a circularly polarized wave.

[0069] The various configurations of the radio wave reflection device exemplified as an embodiment of the present invention can be appropriately combined as long as they do not contradict each other. In addition, a solution obtained by appropriately adding, deleting, or changing the design of the constituent elements, or a solution obtained by adding, omitting, or changing the conditions of the process by those skilled in the art based on the radio wave reflection device disclosed in this specification and the drawings, as long as it has the gist of the present invention, is included in the scope of the present invention.

[0070] Even for other effects different from those brought about by the embodiments disclosed in this specification, effects clearly known from the description of this specification or effects that can be easily predicted by those skilled in the art can of course be understood to be brought about by the present invention.

[0071] Description of Reference Numerals

[0072] 100: Radio wave reflection device, 101: Unit cell, 102: Patch electrode, 1021: First side, 1022: Second side, 1023: Third side, 1024: Fourth side, 104: Opposing electrode, 106: Strip wiring, 1061: First straight portion, 1062: Second straight portion, 108: Transistor, 110: Liquid crystal layer, 112: Alignment film, 114: Control signal line, 116: Selection signal line, 118: Sealing material, 120: Reflective surface, 122: First drive circuit, 124, Second drive circuit, 126: Terminal portion, 127: Terminal electrode, 130: Base insulating layer, 132: First gate electrode, 133: First gate insulating layer, 134: Semiconductor layer, 135: First input / output electrode, 136: Second input / output electrode, 137: Second gate insulating layer, 138: Second gate electrode, 139: First interlayer insulating layer, 140: Connection wiring, 141: Second interlayer insulating layer, 142: Planarization layer, 143: Passivation layer, 150: First substrate, 152: Second substrate, 1601: Region with high current density, 1602: Region with high current density, 301: Unit cell, 306: Strip wiring

Claims

1. A radio wave reflection device, characterized in that, having: a first substrate including a patch electrode, a strip wiring connected to the patch electrode, and a transistor electrically connected to the strip wiring; a second substrate including a counter electrode opposed to the patch electrode; and a liquid crystal layer between the first substrate and the second substrate, wherein the strip wiring includes a first straight portion located in a direction same as a vibration direction of a polarized wave incident on the patch electrode, and a second straight portion crossing the vibration direction of the polarized wave.

2. The radio wave reflection device according to claim 1, wherein, The patch electrode includes a first side extending in a first direction and a second side extending in a second direction crossing the first direction. When the vibration direction of the polarized wave is the same as the first direction, the strip wiring is connected to the second side.

3. The radio wave reflection device according to claim 2, wherein, In the strip wiring, the first straight portion extends in a direction same as the first direction, the second straight portion extends in a direction same as the second direction, and a length of the second straight portion is longer than a length of the first straight portion.

4. The radio wave reflection device according to claim 1, wherein, The patch electrode includes a first side extending in a first direction and a second side extending in a second direction crossing the first direction. When the vibration direction of the polarized wave is the same as the first direction, the strip wiring is connected to the first side.

5. The radio wave reflection device according to claim 4, wherein, In the strip wiring, a direction of the first straight portion is the same as the second direction, a direction of the second straight portion is the same as the first direction, and a length of the second straight portion is longer than a length of the first straight portion.

6. The radio wave reflection device according to claim 3 or 5, wherein, The first straight portion includes a plurality of first straight portions, and the second straight portion includes a plurality of second straight portions. The strip wiring has a meandering pattern.

7. The radio wave reflection device according to claim 1, wherein, The strip wiring and the patch electrode are provided on the same insulating layer, and the strip wiring is connected to the transistor via a contact hole.

8. The radio wave reflection device according to claim 2, wherein, When a length of the second side is set to L, the strip wiring is connected to the patch electrode at positions inward from both ends of the second side by a length more than L / 4.

9. The radio wave reflection device according to claim 4, wherein, When a length of the first side is set to L, the strip wiring is connected to the patch electrode at positions inward from both ends of the first side by a length more than L / 4.

10. The radio wave reflection device according to claim 1, wherein, The group of the patch electrode, the strip wiring, and the transistor are arranged in a matrix. In the radio wave reflection device, a plurality of control signal lines extending in the first direction and a plurality of selection signal lines extending in the second direction are further included in such a manner as to be connected to the transistors arranged in the matrix.

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