Radio wave absorbing device and radio wave absorbing system provided with same

Abstract

The radio wave absorbing device includes: a patch electrode; a counter electrode which faces the patch electrode and is made of a material different from that of the patch electrode; and a liquid crystal layer between the patch electrode and the counter electrode. Another radio wave absorbing device includes: a first patch electrode; a second patch electrode that can be controlled independently of the first patch electrode; a counter electrode that faces the first patch electrode and the second patch electrode; and a liquid crystal layer between the first patch electrode and the counter electrode and between the second patch electrode and the counter electrode. A first relative dielectric constant of the liquid crystal layer sandwiched between the first patch electrode and the counter electrode is different from a second relative dielectric constant of the liquid crystal layer sandwiched between the second patch electrode and the counter electrode.

Description

Technical Field

[0001] One embodiment of the present invention relates to an electromagnetic wave absorbing device capable of absorbing incident electromagnetic waves and an electromagnetic wave absorbing system having the electromagnetic wave absorbing device. Background Technology

[0002] In recent years, devices utilizing high frequencies of 10GHz to 100GHz have become widely used. This has led to problems such as radio wave crosstalk and congestion between multiple high-frequency devices. To address these issues, the demand for radio wave absorbing devices that reduce crosstalk and congestion has increased.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2022-047398 Summary of the Invention

[0006] Conventional radio wave absorption devices are designed to absorb radio waves of a specific frequency. Therefore, once a radio wave absorption device is installed, the frequency of the radio waves absorbed by the device cannot be changed. Furthermore, conventional radio wave absorption devices cannot switch between absorbing and reflecting radio waves.

[0007] One objective of one embodiment of the present invention is to provide an electromagnetic wave absorbing device capable of adjusting electromagnetic wave absorption performance.

[0008] An embodiment of the electromagnetic wave absorption device of the present invention includes: a patch electrode; a counter electrode opposite to the patch electrode and made of a different material than the patch electrode; and a liquid crystal layer between the patch electrode and the counter electrode.

[0009] An embodiment of the electromagnetic wave absorption device of the present invention includes: a first patch electrode; a second patch electrode that can be controlled independently of the first patch electrode; a counter electrode that is opposite to the first patch electrode and the second patch electrode; and a liquid crystal layer between the first patch electrode and the counter electrode and between the second patch electrode and the counter electrode, wherein the first relative permittivity of the liquid crystal layer sandwiched by the first patch electrode and the counter electrode is different from the second relative permittivity of the liquid crystal layer sandwiched by the second patch electrode and the counter electrode.

[0010] An embodiment of the present invention provides an electromagnetic wave absorption system comprising: the aforementioned electromagnetic wave absorption device; and a control device that controls the voltage supplied to the patch electrode and the counter electrode, wherein the control device controls the voltage supplied to the patch electrode and the counter electrode to vary the amount of electromagnetic wave absorption by the electromagnetic wave absorption device for electromagnetic waves of any frequency.

[0011] An embodiment of the present invention provides an electromagnetic wave absorption system comprising: the aforementioned electromagnetic wave absorption device; and a control device that controls the voltage supplied to the first patch electrode, the second patch electrode, and the counter electrode, wherein the control device controls the voltage supplied to the first patch electrode, the second patch electrode, and the counter electrode to vary the amount of electromagnetic wave absorption by the electromagnetic wave absorption device for electromagnetic waves of any frequency. Attached Figure Description

[0012] Figure 1 This is a cross-sectional view and a functional block diagram illustrating an embodiment of the electromagnetic wave absorption system of the present invention.

[0013] Figure 2 This is a cross-sectional view showing an outline of an electromagnetic wave absorbing device according to one embodiment of the present invention.

[0014] Figure 3A This is a top view of the absorption plate cell (unit structure) used in an electromagnetic wave absorption device according to one embodiment of the present invention.

[0015] Figure 3B This is the cross-sectional structure of the absorption plate cell used in an embodiment of the radio wave absorbing device of the present invention.

[0016] Figure 4A This diagram illustrates a state in which no control voltage is applied between the patch electrode and the counter electrode in the absorber cell used in an embodiment of the present invention.

[0017] Figure 4B This diagram illustrates the state in which a control voltage is applied between a patch electrode and a ground electrode in an absorption plate cell used in an electromagnetic wave absorption device according to one embodiment of the present invention.

[0018] Figure 5 This is a simulation result showing the relationship between the voltage supplied to the patch electrode and the ground electrode and the frequency band of the absorbed radio wave in an electromagnetic wave absorption device according to one embodiment of the present invention.

[0019] Figure 6 This represents the simulation results of the frequency band of the absorbed radio waves in the radio wave absorption device according to one embodiment of the present invention.

[0020] Figure 7 These are simulation results showing the relationship between the conductivity of the patch electrode and the ground electrode and the electromagnetic wave absorption in an electromagnetic wave absorption device according to one embodiment of the present invention.

[0021] Figure 8 This is a diagram illustrating the structure of an electromagnetic wave absorption device with a unified control method according to one embodiment of the present invention.

[0022] Figure 9 This is a diagram illustrating the structure of an electromagnetic wave absorption device with an independent control mode according to one embodiment of the present invention.

[0023] Figure 10 This is the cross-sectional structure of the absorption plate cell in an electromagnetic wave absorbing device according to one embodiment of the present invention.

[0024] Figure 11 This is a diagram illustrating a driving method for an electromagnetic wave absorption device according to one embodiment of the present invention.

[0025] Figure 12 This is a simulation result showing the relationship between the driving method of the electromagnetic wave absorption device and electromagnetic wave absorption in an electromagnetic wave absorption device according to one embodiment of the present invention.

[0026] Figure 13 This is a diagram illustrating a driving method for an electromagnetic wave absorption device according to one embodiment of the present invention.

[0027] Figure 14 This is a diagram illustrating a driving method for an electromagnetic wave absorption device according to one embodiment of the present invention.

[0028] Figure 15 This is a simulation result showing the relationship between the driving method of the electromagnetic wave absorption device and electromagnetic wave absorption in an electromagnetic wave absorption device according to one embodiment of the present invention.

[0029] Figure 16 This is a simulation result showing the relationship between the thickness of the substrate and the electromagnetic wave absorption in an electromagnetic wave absorption device according to one embodiment of the present invention.

[0030] Figure 17 This is a simulation result showing the relationship between the thickness of the liquid crystal layer and the electromagnetic wave absorption in an electromagnetic wave absorption device according to one embodiment of the present invention.

[0031] Figure 18 This is a cross-sectional view showing an outline of an electromagnetic wave absorbing device according to one embodiment of the present invention.

[0032] Figure 19 This is a top view showing the outline of the patch electrode of an electromagnetic wave absorbing device according to one embodiment of the present invention. Detailed Implementation

[0033] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention can be implemented in many different ways and is not limited to the description of the embodiments illustrated below. To make the description clearer, the width, thickness, shape, etc. of each part are sometimes shown schematically compared to the actual form, but this is only an example and does not limit the interpretation of the present invention. In this specification and the drawings, the same reference numerals are sometimes used for structures that are the same as those described in the previous drawings (or reference numerals such as a, b, etc. are used after the numbers), and detailed descriptions are appropriately omitted. Furthermore, the words "first" and "second" for each element are convenient identifiers used to distinguish each element and do not have any further meaning unless otherwise specified.

[0034] In this specification, the expression "above (or below)" a component or region relative to other components or regions, unless otherwise specified, includes not only cases where the component or region is directly above (or directly below) other components or regions, but also cases where it is located above (or below) other components or regions. The above expression also includes cases where other constituent elements are included between a component or region and other components or regions.

[0035] In this specification, expressions such as "α includes A, B, or C," "α includes any one of A, B, and C," and "α includes one selected from the group consisting of A, B, and C," unless otherwise specified, do not exclude the possibility that α includes multiple combinations of A to C. Furthermore, these expressions do not exclude the possibility that α includes other elements.

[0036] It should be noted that the following implementation methods can be combined with each other as long as they do not create technical contradictions.

[0037] [1. First Implementation]

[0038] Reference Figures 1-10 An embodiment of the electromagnetic wave absorption system 10 of the present invention will be described.

[0039] [1-1. Radio Wave Absorption System 10]

[0040] Figure 1 This is a cross-sectional view and functional block diagram illustrating an embodiment of the electromagnetic wave absorption system of the present invention. Figure 1 As shown, the electromagnetic wave absorption system 10 includes an electromagnetic wave absorption device 100, a control circuit 500, and a drive circuit 600.

[0041] The electromagnetic wave absorbing device 100 absorbs electromagnetic waves within a specified frequency band. Detailed structure of the electromagnetic wave absorbing device 100 will be described later. The electromagnetic wave absorbing device 100 includes a patch electrode, a counter electrode, and a liquid crystal layer. In the electromagnetic wave absorbing device 100, the orientation of the liquid crystal molecules contained in the liquid crystal layer is controlled by the voltage (control voltage) supplied to the patch electrode and the counter electrode. This orientation control controls the frequency band of the electromagnetic waves absorbed by the electromagnetic wave absorbing device 100.

[0042] The control circuit 500 outputs a control signal corresponding to the input set value (e.g., a frequency value). For example, when a user inputs a specified frequency value via the user interface provided by the radio wave absorption system 10, the control circuit 500 outputs a control signal to control the radio wave absorption device 100 to absorb radio waves of that frequency based on the input frequency value. For example, the control circuit 500 can generate the control signal by performing calculations using the input set value as a parameter. Alternatively, the control circuit 500 may also have a lookup table (LUT) that associates the set value with the control signal, and read the generated signal by referring to the LUT using the input set value.

[0043] The drive circuit 600 is connected to the control circuit 500 and the radio wave absorption device 100. The drive circuit 600 drives the radio wave absorption device 100 (supplying a drive voltage to the radio wave absorption device 100) based on the control signal output by the control circuit 500. That is, the drive circuit 600 supplies control voltage to the patch electrodes and counter electrodes of the radio wave absorption device 100 to absorb radio waves in the frequency band corresponding to the set value input by the user. When the radio wave absorption device 100 has multiple patch electrodes and counter electrodes, the drive circuit 600 can control the multiple patch electrodes and counter electrodes uniformly, control multiple patch electrodes in groups, or control multiple patch electrodes independently.

[0044] Sometimes, the control circuit 500 and the drive circuit 600 are collectively referred to as a "control device". In this case, the control device can control the voltage supplied to the patch electrode and the counter electrode. In other words, the control device controls the amount of absorption of the electromagnetic wave absorbing device 100 relative to electromagnetic waves of arbitrary frequency by controlling the voltage supplied to the patch electrode and the counter electrode. Further, the control device receives a set value related to the frequency of the electromagnetic wave absorbed by the electromagnetic wave absorbing device 100 via an interface, and controls the voltage supplied to the patch electrode and the counter electrode based on this set value.

[0045] [1-2. Electron wave absorbing device 100]

[0046] Figure 2 This is a cross-sectional view illustrating an embodiment of an electromagnetic wave absorbing device according to the present invention. Figure 2As shown, the electromagnetic wave absorbing device 100 includes a plurality of absorbing elements (absorbing plate cells 102). The plurality of absorbing plate cells 102 are arranged along at least one direction. Figure 2 In the device, multiple absorption plate cells 102 are arranged along the Y-axis. The electromagnetic wave absorption device 100 includes a dielectric substrate 104, a counter substrate 106, a patch electrode 108, a ground electrode 110, a liquid crystal layer 114, a sealing material 128, a switching element 134, a terminal portion 126, and a printed circuit board (FPC) 160. The liquid crystal layer 114 contains liquid crystal molecules 116. A passivation layer 158 is provided between the patch electrode 108 and the dielectric substrate 104.

[0047] In the radio wave absorbing device 100, the electrode located on the incident surface of the radio wave among the opposing electrodes (pattern electrode 108 and ground electrode 110) is called a "pattern electrode," and the electrode opposite to the patch electrode is called a "counter electrode." In this embodiment, the ground electrode 110 is equivalent to the counter electrode. When the radio wave is incident from the counter substrate 106 side, the electrode corresponding to the ground electrode 110 is called a patch electrode, as will be described later.

[0048] When the electromagnetic wave absorbing device 100 controls multiple absorption plate cells 102 individually or in groups, each absorption plate cell 102 includes a switching element 134. On the other hand, when the electromagnetic wave absorbing device 100 controls multiple absorption plate cells 102 uniformly, each absorption plate cell 102 may not include a switching element 134. See below for details.

[0049] Each absorber cell 102 includes at least a surface mount electrode 108, a ground electrode 110 (opposite electrode), a liquid crystal layer 114, and a switching element 134. The surface mount electrode 108 is independently provided for each absorber cell 102. The surface mount electrode 108 is located on the dielectric substrate 104 side. The ground electrode 110 is opposite to the surface mount electrode 108 and is shared with respect to multiple absorber cells 102. The ground electrode 110 is located on the opposing substrate 106 side. Detailed structure of the absorber cell 102 will be described later.

[0050] A liquid crystal layer 114 is disposed between the patch electrode 108 and the ground electrode 110. The orientation of the liquid crystal molecules 116 contained in the liquid crystal layer 114 is controlled by a control voltage supplied to the patch electrode 108 and the ground electrode 110. A sealing material 128 is disposed to surround the opposing substrate 106. In other words, the liquid crystal layer 114 is sealed by the sealing material 128. The patch electrode 108 and the ground electrode 110 are disposed in the area surrounded by the sealing material 128.

[0051] The material of the patch electrode 108 is different from the material of the ground electrode 110. The conductivity (or electrical conductivity) of the material constituting the patch electrode 108 is different from the conductivity of the material constituting the ground electrode 110. For example, the ratio of the conductivity of the material constituting the patch electrode 108 to the conductivity of the material constituting the ground electrode 110 is more than 10 times. The amount of electromagnetic waves absorbed by the electromagnetic wave absorbing device 100 is affected by the balance of the conductivity of the patch electrode 108 and the ground electrode 110, as detailed later. By giving the conductivity of the patch electrode 108 and the ground electrode 110 the aforementioned characteristics, the amount of electromagnetic waves absorbed by the electromagnetic wave absorbing device 100 can be increased.

[0052] The electromagnetic wave absorbing device 100 is divided into an electromagnetic wave absorbing region 162 and a surrounding peripheral region 164. The electromagnetic wave absorbing region 162 is the region where a patch electrode 108 and a ground electrode 110 are disposed. Electrons incident on the electromagnetic wave absorbing device 100 from the dielectric substrate 104 side are absorbed by the electromagnetic wave absorbing region 162. The orientation of the liquid crystal molecules 116 is controlled by supplying a control voltage between the patch electrode 108 and the ground electrode 110, so that the electromagnetic waves incident on the electromagnetic wave absorbing device 100 are absorbed by the patch electrode 108. That is, the patch electrode 108 functions as a receiving antenna for the incident electromagnetic waves. Since the reflection characteristics of this receiving antenna can be controlled according to the control voltage supplied between the patch electrode 108 and the ground electrode 110, the frequency band of the electromagnetic waves absorbed by the patch electrode 108 can be controlled by controlling the control voltage. Although not shown, a portion of the driving circuit 600 is disposed in the peripheral region 164.

[0053] Switching element 134 is connected to surface mount electrode 108. Switching element 134 is positioned near the incident surface of the radio wave, with surface mount electrode 108 as a reference. Switching element 134 is driven by drive circuit 600 (see reference). Figure 1 The orientation of the liquid crystal molecules 116 is controlled according to the driving state of the switching element 134. The frequency band of the radio waves absorbed by the radio wave absorption device 100 is controlled by controlling the orientation of the liquid crystal molecules 116, as detailed later.

[0054] Terminal portion 126 is provided at the end of dielectric substrate 104. Terminal portion 126 may also be constructed of the same layer as surface mount electrode 108. Terminal portion 126 may also be a layer that is part or all the same as the conductive layer constituting switching element 134. Terminal portion 126 is connected to switching element 134 via wiring. FPC 160 is connected to terminal portion 126. Drive circuit 600 drives switching element 134 according to control signals input from the outside via FPC 160.

[0055] [1-3. Absorbent Panel Cells]

[0056] Figure 3A and Figure 3B This is a top view of the absorption plate cell used in an electromagnetic wave absorption device according to one embodiment of the present invention. Figure 3A This is a top view of the absorption plate cell 102 as seen from above (on the side where the radio waves are incident). Figure 3B This is a sectional view between A1 and A2 shown in the top view.

[0057] like Figure 3A and Figure 3B As shown, the absorber cell 102 includes a dielectric substrate 104, a counter substrate 106, a patch electrode 108, a ground electrode 110, a liquid crystal layer 114, a first alignment film 112a, and a second alignment film 112b. In the absorber cell 102, the dielectric substrate 104 can also be considered as a single layer (dielectric layer). The patch electrode 108 is disposed on the dielectric substrate 104, and the ground electrode 110 is disposed on the counter substrate 106. The first alignment film 112a is disposed on the dielectric substrate 104 to cover the patch electrode 108. The second alignment film 112b is disposed on the counter substrate 106 to cover the ground electrode 110. The patch electrode 108 and the ground electrode 110 are arranged opposite each other, with the liquid crystal layer 114 disposed between them. The first alignment film 112a is located between the patch electrode 108 and the liquid crystal layer 114. The second alignment film 112b is located between the ground electrode 110 and the liquid crystal layer 114.

[0058] The patch electrode 108 preferably has a shape symmetrical with respect to the vertically polarized wave and the horizontally polarized wave of the incident electromagnetic wave. For example, the patch electrode 108 has a square or circular shape when viewed from above. Figure 3A This indicates that the patch electrode 108 is square when viewed from above. The shape of the ground electrode 110 is not particularly limited, and it has a shape that extends across approximately the entire surface of the opposing substrate 106, having an area larger than that of the patch electrode 108. The materials used to form the patch electrode 108 and the ground electrode 110 are not limited, except that the materials of the patch electrode 108 and the ground electrode 110 are different. The patch electrode 108 and the ground electrode 110 are formed using a conductive metal or metal oxide. A first wiring 118 is provided on the dielectric substrate 104. The first wiring 118 is connected to the patch electrode 108. The first wiring 118 is used when supplying a control voltage to the patch electrode 108. In the case where a plurality of absorber plate cells 102 are arranged in the electromagnetic wave absorption device 100, the first wiring 118 is used to connect a patch electrode 108 to an adjacent patch electrode 108.

[0059] Although not in Figure 3A and Figure 3BAs shown, the dielectric substrate 104 and the opposing substrate 106 are bonded together by a sealing material 128. The dielectric substrate 104 and the opposing substrate 106 are arranged opposite each other with a gap. The liquid crystal layer 114 is disposed in the area surrounded by the sealing material 128. The liquid crystal layer 114 is disposed to fill the gap between the dielectric substrate 104 and the opposing substrate 106.

[0060] For example, when the shape of the patch electrode 108 is a square with a side length of approximately 2 mm, the spacing between the dielectric substrate 104 and the opposing substrate 106 is 5 μm to 100 μm, 10 μm to 40 μm, or 15 μm to 25 μm. In other words, the ratio of the spacing between the dielectric substrate 104 and the opposing substrate 106 to the side length (approximately 2 mm) of the patch electrode 108 is 0.25% to 5%, 0.5% to 2%, or 0.75% to 1.25%.

[0061] A patch electrode 108, a ground electrode 110, a first alignment film 112a, and a second alignment film 112b are provided between the dielectric substrate 104 and the opposing substrate 106. Therefore, more precisely, the spacing between the first alignment film 112a and the second alignment film 112b respectively provided on the dielectric substrate 104 and the opposing substrate 106 is the thickness of the liquid crystal layer 114. Although not in... Figure 3B As shown in the figure, a spacer for keeping the spacing constant may also be provided between the dielectric substrate 104 and the opposing substrate 106.

[0062] A control voltage is supplied to the patch electrode 108 to control the orientation of the liquid crystal molecules 116 in the liquid crystal layer 114. For example, the control voltage is a DC voltage signal or a polarity reversal voltage signal where positive and negative DC voltages alternate. In the latter case, a voltage at an intermediate level between ground level and polarity reversal voltage is supplied to the ground electrode 110. By supplying the control voltage to the patch electrode 108, the orientation state of the liquid crystal molecules contained in the liquid crystal layer 114 changes. The liquid crystal layer 114 uses a liquid crystal material with dielectric anisotropy. For example, nematic liquid crystals, smectic liquid crystals, cholesteric liquid crystals, and disk-shaped liquid crystals can be used as the liquid crystal layer 114. The dielectric constant of the liquid crystal layer 114 with dielectric anisotropy changes according to the change in the orientation state of the liquid crystal molecules. The absorber cell 102 can change the dielectric constant of the liquid crystal layer 114 according to the control voltage supplied to the patch electrode 108, thereby adjusting the frequency band of the electromagnetic waves absorbed by the absorber cell 102.

[0063] Figure 4A This indicates a state where no voltage is supplied between the patch electrode 108 and the ground electrode 110, or a state where the potential difference between the two electrodes is zero (referred to as "state 1"). Figure 4AThis indicates the case where the first alignment film 112a and the second alignment film 112b are horizontally aligned films. In the first state, the long axis of the liquid crystal molecule 116 passes through the first alignment film 112a and the second alignment film 112b and is horizontally aligned relative to the surfaces of the patch electrode 108 and the ground electrode 110. Figure 4B This indicates a state where a control voltage is supplied to the patch electrode 108 (referred to as "state 2"). In state 2, the liquid crystal molecules 116 are oriented perpendicularly to the surfaces of the patch electrode 108 and the ground electrode 110 due to the electric field. The orientation angle of the long axis of the liquid crystal molecules 116 can also be controlled to be a direction between the horizontal and vertical directions depending on the magnitude of the control voltage supplied to the patch electrode 108 (the magnitude of the voltage between the counter electrode and the patch electrode).

[0064] When the liquid crystal molecule 116 has positive dielectric anisotropy, the dielectric constant of the second state is larger than that of the first state. On the other hand, when the liquid crystal molecule 116 has negative dielectric anisotropy, the dielectric constant of the second state is smaller than that of the first state. The liquid crystal layer 114 with dielectric anisotropy can also be regarded as a variable dielectric layer. The absorption plate cell 102 can adjust the frequency band of the absorbed radio wave by utilizing the dielectric anisotropy of the liquid crystal layer 114.

[0065] Absorbing plate cell 102 is used as an absorbing plate to absorb radio waves. The absorbing plate cell 102 is preferably designed to minimize reflection of incident radio waves. Figure 3B As can be clearly seen from the structure shown, when an electromagnetic wave propagating in the air is incident on the absorber cell 102, the wave passes through the dielectric substrate 104 twice. The dielectric substrate 104 is formed of a dielectric material such as glass or resin. When the electromagnetic wave passes through the dielectric, its phase velocity changes. Therefore, in order to prevent the amplitude of the reflected wave from increasing, it is preferable to set the thickness of the dielectric substrate 104 to be a thickness that deviates from 1 / 4 wavelength of the wavelength of the incident electromagnetic wave (e.g., 1 / 8 wavelength).

[0066] [1-4. Simulation results of the radio wave absorbing device 100]

[0067] Figure 5 This is a simulation result showing the relationship between the voltage supplied to the patch electrode and the ground electrode and the frequency band of the absorbed radio wave in an electromagnetic wave absorption device according to one embodiment of the present invention. Figure 5 The simulation results shown are from a simulation of the reflection characteristics of an absorbing plate cell 102. In this simulation, calculations were performed based on a model assuming the periodic structure of the absorbing plate cell 102 extends infinitely. The simulation was performed using CST Studio Suite (manufactured by Dassault Systèmes). The parameters of the electromagnetic wave absorbing device 100 used in the simulation are as follows.

[0068] • Spacing of the patch electrodes 108: 3mm

[0069] • Dimensions of the patch electrode 108: 2mm × 2mm

[0070] • Thickness of liquid crystal layer 114: 30μm

[0071] • The relative permittivity ε of liquid crystal layer 114: 2.5, 3.5

[0072] • Thickness of substrate 101: 1.0 mm

[0073] exist Figure 5 In the chart shown, the vertical axis represents reflection amplitude, and the horizontal axis represents frequency. Figure 5 In the graph, a larger reflection amplitude (closer to zero) means that the electromagnetic wave absorbing device 100 reflects more of the incident electromagnetic wave. In other words, in... Figure 5 In the chart, the smaller the reflected amplitude (farther than zero), the more the incident radio wave is absorbed by the radio wave absorbing device 100.

[0074] Figure 5 Two simulation results are shown. These simulation results are for different relative permittivity of the liquid crystal layer 114 (relative permittivity ε = 2.5 and 3.5). Figure 5 In the diagram, dashed lines represent simulation results when the relative permittivity ε is 2.5, and solid lines represent simulation results when the relative permittivity ε is 3.5. In the electromagnetic wave absorption device 100, the simulation result when the relative permittivity ε is 2.5 corresponds to the simulation result when no control voltage is supplied to the patch electrode 108 and the ground electrode 110 (the potential difference between the two electrodes is zero). On the other hand, the simulation result when the relative permittivity ε is 3.5 corresponds to the simulation result when a control voltage is supplied to the patch electrode 108 and the ground electrode 110. The relative permittivity ε can be adjusted within the range of 2.5 to 3.5 based on the control voltage supplied to the patch electrode 108 and the ground electrode 110.

[0075] like Figure 5 As shown, when the relative permittivity ε is 2.5, the frequency at which the reflected amplitude reaches its minimum value is 42.9 GHz. That is, under this condition, the radio wave absorbing device 100 is most effective at absorbing radio waves at a frequency of 42.9 GHz. On the other hand, when the relative permittivity ε is 3.5, the frequency at which the reflected amplitude reaches its minimum value is 37.4 GHz. That is, under this condition, the radio wave absorbing device 100 is most effective at absorbing radio waves at a frequency of 37.4 GHz.

[0076] To put the above results another way, for a radio wave with a frequency of 42.9 GHz, when the relative permittivity ε is 2.5, the radio wave absorbing device 100 absorbs the incident radio wave (42.9 GHz), but when the relative permittivity ε is 3.5, the radio wave absorbing device 100 reflects the incident radio wave (42.9 GHz). Similarly, for a radio wave with a frequency of 37.4 GHz, when the relative permittivity ε is 2.5, the radio wave absorbing device 100 reflects the incident radio wave (37.4 GHz), and when the relative permittivity ε is 3.5, the radio wave absorbing device 100 absorbs the incident radio wave (37.4 GHz). In other words, the radio wave absorbing device 100 can switch between absorption and reflection states for a specific frequency of radio wave.

[0077] [1-5. Influence of the materials of the patch electrode 108 and the ground electrode 110]

[0078] Figure 6 This represents the simulation results of the frequency band of electromagnetic waves absorbed in an electromagnetic wave absorbing device according to one embodiment of the present invention. Figure 6 The following shows four simulation results 1000 ([A] to [D]) of different combinations of patch electrode 108 and ground electrode 110. Figure 6 The conductivity of Al used in the simulation shown is 3.5 × 10⁻⁶. 7 [S / m], the conductivity of ITO is 6.7 × 10⁻⁶. 5 [S / m].

[0079] [A] Surface mount electrode 108 / Ground electrode 110 = Al / ITO

[0080] [B] Surface mount electrode 108 / Ground electrode 110 = ITO / Al

[0081] [C] Surface mount electrode 108 / Ground electrode 110 = ITO / ITO

[0082] [D] Patch electrode 108 / Ground electrode 110 = Al / Al

[0083] like Figure 6 As shown in [A], when the patch electrode 108 / ground electrode 110 is Al / ITO and the relative permittivity ε of the liquid crystal layer 114 is 2.5, the minimum reflection amplitude is approximately -50 dB. When the patch electrode 108 / ground electrode 110 is Al / ITO and the relative permittivity ε of the liquid crystal layer 114 is 3.5, the minimum reflection amplitude is approximately -21 dB.

[0084] like Figure 6As shown in [B], when the patch electrode 108 / ground electrode 110 is ITO / Al and the relative permittivity ε of the liquid crystal layer 114 is 2.5, the minimum reflection amplitude is approximately -34 dB. When the patch electrode 108 / ground electrode 110 is ITO / Al and the relative permittivity ε of the liquid crystal layer 114 is 3.5, the minimum reflection amplitude is approximately -20 dB.

[0085] like Figure 6 As shown in [C], when the patch electrode 108 / ground electrode 110 is ITO / ITO and the relative permittivity ε of the liquid crystal layer 114 is 2.5, the minimum reflection amplitude is approximately -14 dB. When the patch electrode 108 / ground electrode 110 is ITO / ITO and the relative permittivity ε of the liquid crystal layer 114 is 3.5, the minimum reflection amplitude is approximately -10 dB.

[0086] like Figure 6 As shown in [D], when the patch electrode 108 / ground electrode 110 is Al / Al, the minimum value of the reflection amplitude is approximately -8dB regardless of whether the relative permittivity ε of the liquid crystal layer 114 is 2.5 or 3.5.

[0087] As described above, the minimum reflected amplitude when the materials of the patch electrode 108 and the ground electrode 110 are different ([A], [B]) is smaller than the minimum reflected amplitude when the materials of the patch electrode 108 and the ground electrode 110 are the same ([C], [D]). In other words, the electromagnetic wave absorbing device 100 with different materials for the patch electrode 108 and the ground electrode 110 absorbs more electromagnetic waves than the electromagnetic wave absorbing device 100 with the same materials for both. By making the ratio of the conductivity of the material constituting the patch electrode 108 to the conductivity of the material constituting the ground electrode 110 10 times or more, the absorption of electromagnetic waves by the electromagnetic wave absorbing device 100 can be further increased. This ratio can also be 20 times or more, 30 times or more, or 50 times or more. Similarly, to put the above results in another way, the material of the patch electrode 108 is one of a metal material and a transparent conductive material, and the material of the ground electrode 110 is the other of a metal material and a transparent conductive material. That is to say, when the patch electrode is made of a metal material, the material of the counter electrode is a transparent conductive material; when the patch electrode is made of a transparent conductive material, the material of the counter electrode is a metal material.

[0088] Figure 7 These are simulation results showing the relationship between the conductivity of the patch electrode and the ground electrode and the electromagnetic wave absorption in an electromagnetic wave absorption device according to one embodiment of the present invention. Figure 7In the diagram, the horizontal axis represents the common logarithm of the conductivity of the ground electrode 110 (Log(Conduct_G)), and the vertical axis represents the common logarithm of the conductivity of the patch electrode 108 (Log(Conduct_P)). Figure 7 In the two-dimensional diagram, the simulation results for each conductivity are plotted, showing the minimum value of the reflection amplitude when the relative permittivity ε of the liquid crystal layer 114 is 2.5 and the average value of the minimum value of the reflection amplitude when the relative permittivity ε of the liquid crystal layer 114 is 3.5.

[0089] like Figure 7 As shown, the region with a relatively small minimum reflected amplitude (below -20 dB) is distributed in a quadratic pattern (curving from the upper left to the lower right of the graph). The region with a minimum reflected amplitude below -20 dB is influenced by the balance of the conductivity of the patch electrode 108 and the ground electrode 110. This is because the smaller the difference between the characteristic impedance of air and the impedance of the metasurface, the greater the amount of electromagnetic wave absorbed in the electromagnetic wave absorbing device 100.

[0090] As described above, the electromagnetic wave absorbing device 100 according to this embodiment can adjust the frequency band of the electromagnetic waves absorbed by the electromagnetic wave absorbing device 100 according to the control voltage supplied to the patch electrode 108 and the ground electrode 110.

[0091] [1-6. Control method of radio wave absorbing device 100]

[0092] Reference Figures 8-10 The control method for the radio wave absorbing device 100 integrating the absorption plate cell 102 will be described. The control method for the radio wave absorbing device 100 includes a unified control method and an independent control method. The following describes each control method.

[0093] [1-6-1. Unified Control Method]

[0094] Figure 8 This is a diagram illustrating the structure of an electromagnetic wave absorbing device according to a unified control method of one embodiment of the present invention. The electromagnetic wave absorbing device 100a has an absorbing plate 120. The absorbing plate 120 is composed of a plurality of absorbing plate cells 102. The plurality of absorbing plate cells 102 are, for example, along a first direction (…). Figure 8 The X-axis direction shown) and the second direction intersecting the first direction ( Figure 8 (As shown in the Y-axis direction). The absorber cell 102 is arranged with the patch electrodes 108 facing the incident surface of the electromagnetic wave. The absorber 120 is flat, and multiple patch electrodes 108 are arranged in a matrix within the flat surface. Figure 8 The electromagnetic wave absorbing device 100a shown may also exclude the switching element 134.

[0095] The electromagnetic wave absorbing device 100a has a structure in which multiple absorbing plate cells 102 are integrated on a dielectric substrate 104. For example... Figure 8 As shown, the electromagnetic wave absorption device 100a has the following structure: a dielectric substrate 104 with a plurality of patch electrodes 108 arranged thereon is overlapped with a counter substrate 106 having a ground electrode 110, and a liquid crystal layer 114 is provided between the two substrates. An absorption plate 120 is formed in the region where the plurality of patch electrodes 108 overlap with the ground electrode 110. The cross-sectional structure of the absorption plate 120 is similar to that of each patch electrode 108. Figure 3B The absorption plate cell 102 shown has the same structure. The dielectric substrate 104 and the opposing substrate 106 are bonded together by a sealing material 128, and the liquid crystal layer 114 is disposed in the area inside the sealing material 128.

[0096] The dielectric substrate 104 has a thickness that deviates from 1 / 4 of the wavelength of the absorbed electromagnetic wave (e.g., 1 / 8 of the wavelength). In addition to the area opposite to the opposing substrate 106, the dielectric substrate 104 also has a peripheral region 122 extending outward from the opposing substrate 106. A first driving circuit 124 and a terminal portion 126 are provided in the peripheral region 122. The first driving circuit 124 supplies a control voltage to the patch electrode 108. In this configuration, the first driving circuit 124 corresponds to the driving circuit 600. The terminal portion 126 is the portion connected to an external circuit and is also the portion connected to the FPC 160. A signal controlling the first driving circuit 124 is input to the terminal portion 126.

[0097] As described above, a plurality of surface mount electrodes 108 are arranged on the dielectric substrate 104 along a first direction (X-axis direction) and a second direction (Y-axis direction). A plurality of first wirings 118 extending along the second direction (Y-axis direction) and a plurality of second wirings 119 extending along the first direction (X-axis direction) are disposed on the dielectric substrate 104. The plurality of first wirings 118 electrically connect the plurality of surface mount electrodes 108 arranged along the second direction (Y-axis direction). In other words, the plurality of surface mount electrodes 108 arranged along the second direction (Y-axis direction) are connected by the first wirings 118. Similarly, the plurality of second wirings 119 electrically connect the plurality of surface mount electrodes 108 arranged along the first direction (X-axis direction). In other words, the plurality of surface mount electrodes 108 arranged along the first direction (X-axis direction) are connected by the second wirings 119. The absorption plate 120 has a structure configured such that a matrix-shaped patch electrode array connected by a first wiring 118 and a second wiring 119 extends in the XY plane.

[0098] Multiple first wirings 118 disposed on the absorber plate 120 extend to the peripheral region 122 and are connected to the first driving circuit 124. The first driving circuit 124 supplies control voltage for supplying to the patch electrodes 108. The first driving circuit 124 supplies control voltage of the same voltage level to each of the multiple first wirings 118. Thus, in the absorber plate 120, a unified control voltage is supplied to the multiple patch electrodes 108 arranged along the first direction (X-axis direction) and the second direction (Y-axis direction).

[0099] [1-6-2. Independent Control Mode]

[0100] The following radio wave absorbing device 100b is capable of independently controlling the absorbing plate cell 102. In the following description, the differences from the radio wave absorbing device 100a described above will be the focus.

[0101] Figure 9 The structure of the electromagnetic wave absorbing device 100b according to this embodiment is shown. In the following description, it is used in conjunction with... Figure 8 The different parts of the electromagnetic wave absorbing device 100a shown will be described in detail.

[0102] The electromagnetic wave absorbing device 100b has multiple first wirings 118 extending along the second direction (Y-axis direction) and multiple second wirings 132 extending along the first direction (X-axis direction) on the absorbing plate 120. The multiple first wirings 118 and multiple second wirings 132 are arranged in a crossing manner separated by an insulating layer (not shown). That is, the first wirings 118 and the second wirings 132 are insulated from each other. The multiple first wirings 118 are connected to a first drive circuit 124, and the multiple second wirings 132 are connected to a second drive circuit 130. The first drive circuit 124 supplies a control voltage, and the second drive circuit 130 outputs a scanning signal. In this configuration, the first drive circuit 124 and the second drive circuit 130 correspond to the drive circuit 600. Figure 9 In this embodiment, the first driving circuit 124 is shown with an IC chip or the like mounted on the dielectric substrate 104. The second driving circuit 130 is shown as a driving circuit using a thin-film transistor formed on the dielectric substrate 104 in the same manner as the switching element 134. However, this embodiment is not limited to this structure.

[0103] exist Figure 9The lower part shows an enlarged insert view of the configuration of four surface mount electrodes 108, two first wirings 118, and two second wirings 132. Switching elements 134 are provided on each of the four surface mount electrodes 108. The switching (on and off) of the switching elements 134 is controlled by a scan signal supplied to the second wirings 132. When the switching element 134 is on, the surface mount electrode 108 is connected to the first wirings 118. A control voltage is supplied to the surface mount electrode 108 via the switching element 134. The switching element 134 is formed, for example, by a thin-film transistor. With this structure, multiple surface mount electrodes 108 arranged in a first direction (X-axis direction) can be selected row by row, and control signals of different voltage levels can be supplied to each row.

[0104] Figure 9 The radio wave absorbing device 100b shown can independently control the absorbing plate cells 102. Therefore, it is possible to control all absorbing plate cells 102 uniformly as in the first embodiment described above, or to control each absorbing plate cell 102 differently as in the second embodiment described below.

[0105] [1-6-3. Cross-sectional structure of the radio wave absorbing device 100]

[0106] Figure 10 This diagram illustrates an example of the cross-sectional structure of an absorber cell 102 on which a switching element 134 is connected to a patch electrode 108. The switching element 134 is disposed on a dielectric substrate 104. The switching element 134 is a transistor, having a structure in which a first gate 138, a first gate insulating layer 140, a semiconductor layer 142, a second gate insulating layer 146, and a second gate 148 are stacked. An undercoating layer 136 may also be provided between the first gate 138 and the dielectric 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 contact with the semiconductor layer 142. A first connection wiring 144 is provided on the same layer as the conductive layer forming the first wiring 118. The first connection wiring 144 is provided in contact with the semiconductor layer 142. The connection configuration of the first wiring 118 and the first connection wiring 144 relative to the semiconductor layer 142 shows a configuration in which one wiring is connected to the source of a transistor and the other wiring is connected to the drain.

[0107] A first interlayer insulating layer 150 is provided to cover the switching element 134. A second wiring 132 is provided beneath the first interlayer insulating layer 150. The second wiring 132 is connected to a second gate 148 via a contact hole formed in the first interlayer insulating layer 150. Although not shown, the first gate 138 and the second gate 148 are electrically connected to each other in a region that does not overlap with the semiconductor layer 142. A second connection wiring 152 is provided beneath the first interlayer insulating layer 150 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.

[0108] A second interlayer insulating layer 154 is provided to cover the second wiring 132 and the second connection wiring 152. Furthermore, a planarization layer 156 is provided to fill the layer gaps of the switching element 134. By providing the planarization layer 156, the patch electrode 108 can be formed without being affected by the configuration of the switching element 134. A passivation layer 158 is provided beneath the flat surface of the planarization layer 156. The patch electrode 108 is disposed beneath the passivation layer 158. The patch electrode 108 is connected to the second connection wiring 152 via contact holes penetrating the passivation layer 158, the planarization layer 156, and the second interlayer insulating layer 154. A first alignment film 112a is provided beneath the patch electrode 108.

[0109] Opposite substrate 106 and Figure 3B Similarly, it includes a ground electrode 110 and a second alignment film 112b. The surface of the dielectric substrate 104 with the switching element 134 and the patch electrode 108 is arranged opposite to the surface of the opposing substrate with the ground electrode 110, and a liquid crystal layer 114 is disposed therebetween. The thickness t of the liquid crystal layer 114 is equivalent to the length from the surface of the patch electrode 108 on the liquid crystal layer 114 side to the surface of the ground electrode 110 on the liquid crystal layer 114 side.

[0110] Each layer formed on the dielectric substrate 104 is formed using the materials described below. For example, the underlayer 136 is formed of a silicon oxide film. For example, the first gate insulating layer 140 and the second gate insulating layer 146 are formed 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 or polycrystalline silicon, or an oxide semiconductor including metal oxides such as indium oxide, zinc oxide, and gallium oxide. For example, the first gate 138 and the second gate 148 may also be made of molybdenum (Mo), tungsten (W), or alloys thereof. The first wiring 118, the second wiring 132, the first connection wiring 144, and the second connection wiring 152 are formed using metallic materials such as titanium (Ti), aluminum (Al), and molybdenum (Mo). For example, the aforementioned gate and wiring may also be formed of a titanium (Ti) / aluminum (Al) / titanium (Ti) stacked structure or a molybdenum (Mo) / aluminum (Al) / molybdenum (Mo) stacked structure. The planarization layer 156 is formed of resin materials such as acrylic acid and polyimide. For example, the passivation layer 158 is formed of silicon nitride film or the like. The patch electrode 108 and the ground electrode 110 are formed of metal films such as aluminum (Al) and copper (Cu), or transparent conductive films such as indium tin oxide (ITO).

[0111] like Figure 10 As shown, the second wiring 132 is connected to the gate of the transistor used as a switching element 134, the first wiring 118 is connected to one of the source and drain of the transistor, and the surface mount electrode 108 is connected to the other of the source and drain. Thus, a predetermined surface mount electrode can be selected from a plurality of surface mount electrodes 108 arranged in a matrix to supply a control voltage. Furthermore, by providing the switching element 134 to each surface mount electrode 108 in the absorption plate 120, a control voltage can be supplied to each surface mount electrode 108 arranged laterally in a row along the first direction (X-axis direction) or each surface mount electrode 108 arranged longitudinally in a row along the second direction (Y-axis direction).

[0112] [2. Second Implementation]

[0113] Reference Figure 11 and Figure 12 An electromagnetic wave absorption system 10C according to one embodiment of the present invention will be described. The structure of the electromagnetic wave absorption system 10C of the second embodiment is similar to that of the electromagnetic wave absorption system 10 of the first embodiment. In the following description, descriptions of structures identical to those of the electromagnetic wave absorption system 10 will be omitted, and structures different from those of the electromagnetic wave absorption system 10 will be described. When describing structures identical to those of the first embodiment, refer to... Figures 1-10 The letter "C" is added after the reference numerals in these figures for illustrative purposes.

[0114] [2-1. Electromagnetic wave absorption device 100C]

[0115] The electromagnetic wave absorbing device 100C in the electromagnetic wave absorbing system 10C of this embodiment passes through... Figure 9 The independent control method shown is used for control. In the electromagnetic wave absorbing device 100 of the first embodiment, a control voltage is uniformly supplied to all the patch electrodes 108 provided on the absorbing plate 120. On the other hand, in the electromagnetic wave absorbing device 100C of this embodiment, the patch electrodes 108C provided on the absorbing plate 120C are divided into multiple groups, and a control voltage is supplied to the patch electrodes 108C on a group basis. Specifically, the patch electrodes 108C are divided into a group consisting of the first patch electrode 108C-1 and a group consisting of the second patch electrode 108C-2.

[0116] Since the electromagnetic wave absorbing device 100C is controlled independently, the first patch electrode 108C-1 and the second patch electrode 108C-2 can be controlled independently. Similar to the electromagnetic wave absorbing device 100 of the first embodiment, the electromagnetic wave absorbing device 100C includes a ground electrode 110C (opposite electrode) and a liquid crystal layer 114C. The ground electrode 110C (opposite electrode) is respectively opposite to the first patch electrode 108C-1 and the second patch electrode 108C-2. The liquid crystal layer 114C is disposed between the first patch electrode 108C-1 and the ground electrode 110 (opposite electrode) and between the second patch electrode 108C-2 and the ground electrode 110 (opposite electrode).

[0117] like Figure 11 As shown, the first patch electrode 108C-1 and the second patch electrode 108C-2 are arranged in a checkerboard pattern or an alternating arrangement. That is, the first patch electrode 108C-1 is adjacent to the second patch electrode 108C-2 in all directions (up, down, left, right). Similarly, the second patch electrode 108C-2 is adjacent to the first patch electrode 108C-1 in all directions (up, down, left, right). Figure 11 The arrangement is an example of this embodiment, and this embodiment is not limited to this arrangement.

[0118] Different control voltages are supplied to the first patch electrode 108C-1 and the second patch electrode 108C-2. That is, the relative permittivity ε (first relative permittivity) of the liquid crystal layer 114C sandwiched between the first patch electrode 108C-1 and the ground electrode 110C is different from the relative permittivity ε (second relative permittivity) of the liquid crystal layer 114C sandwiched between the second patch electrode 108C-2 and the ground electrode 110C. For example, a control voltage is supplied to the first patch electrode 108C-1, and the same voltage as the ground electrode 110C is supplied to the second patch electrode 108C-2. In other words, a potential difference based on the control voltage is generated between the first patch electrode 108C-1 and the ground electrode 110C. On the other hand, the potential difference between the second patch electrode 108C-2 and the ground electrode 110C is zero. As a result, the relative permittivity ε of the liquid crystal layer 114C belonging to the first patch electrode 108C-1 is 3.5. On the other hand, the relative permittivity ε of the liquid crystal layer 114C belonging to the second patch electrode 108C-2 is 2.5.

[0119] In this embodiment, a control voltage with a relative permittivity ε of 3.5 for the liquid crystal layer 114C is supplied to the first patch electrode 108C-1, and a control voltage with a relative permittivity ε of 2.5 for the liquid crystal layer 114C is supplied to the second patch electrode 108C-2. However, control voltages other than those described above may also be supplied to the first patch electrode 108C-1 and the second patch electrode 108C-2. For example, the relative permittivity ε of the liquid crystal layer 114C belonging to the first patch electrode 108C-1 may be fixed at 3.5, and the relative permittivity ε of the liquid crystal layer 114C belonging to the second patch electrode 108C-2 may be adjusted within the range of 2.5 to 3.5.

[0120] [2-2. Simulation results of the radio wave absorbing device 100C]

[0121] Figure 12 This is a simulation result showing the relationship between the driving method of the electromagnetic wave absorption device and electromagnetic wave absorption in an electromagnetic wave absorption device according to one embodiment of the present invention. Figure 12 The simulation result 1100 shown is a simulation of the reflection characteristics of the absorbing plate cells 102C arranged in a 2×2 matrix. This simulation was performed using CST Studio Suite (manufactured by Dassault Systèmes). The parameters of the electromagnetic wave absorbing device 100C used in the simulation are as follows.

[0122] • Spacing of 108C surface mount electrodes: 3mm

[0123] • Dimensions of the 108C surface mount electrode: 2mm × 2mm

[0124] • Thickness of the 114C liquid crystal layer: 30μm

[0125] • The relative permittivity ε of the liquid crystal layer 114C belonging to the first patch electrode 108C-1 is 3.5.

[0126] • The relative permittivity ε of the liquid crystal layer 114C belonging to the second patch electrode 108C-2 is 2.5~3.4.

[0127] • Thickness of substrate 101C: 1.0 mm

[0128] Figure 12 Four simulation results are shown. The simulation results labeled [X1] to [X3] are obtained using the parameters described above.

[0129] The simulation results marked [X1] are for the case where the relative permittivity ε of the liquid crystal layer 114C of the second patch electrode 108C-2 is 2.5 to 2.8. The simulation results marked [X2] are for the case where the relative permittivity ε of the liquid crystal layer 114C of the second patch electrode 108C-2 is 2.9 to 3.1. The simulation results marked [X3] are for the case where the relative permittivity ε of the liquid crystal layer 114C of the second patch electrode 108C-2 is 3.2 to 3.4.

[0130] The simulation results marked [Y] are not simulation results of the electromagnetic wave absorbing device 100C of this embodiment, but simulation results of the electromagnetic wave absorbing device 100 of the first embodiment. That is, the simulation results marked [Y] are simulation results under the condition that the relative permittivity ε of the liquid crystal layer 114 of all patch electrodes 108 is the same.

[0131] like Figure 12 As shown in Figure [X2], when the relative permittivity ε of the liquid crystal layer 114C belonging to the first patch electrode 108C-1 is 3.5 and the relative permittivity ε of the liquid crystal layer 114C belonging to the second patch electrode 108C-2 is 3.0, the frequency at which the reflection amplitude has a minimum value is 39.3 GHz. The minimum value in this case is approximately -48 dB.

[0132] On the other hand, under the unified control method shown in the first embodiment, when adjusting the frequency at which the reflection amplitude has a minimum value to approximately 39.3 GHz, it is necessary to control the relative permittivity ε of the liquid crystal layer 114 to 3.2. However, as Figure 12As shown in the graph of [Y], under the unified control method, the minimum reflection amplitude is approximately -13 dB when the relative permittivity ε of the liquid crystal layer 114 is 3.2. In other words, compared to controlling the minimum reflection amplitude to the desired frequency using the unified control method, controlling the minimum reflection amplitude to the desired frequency using the independent control method can further reduce the minimum reflection amplitude.

[0133] Similar to the first embodiment, when the materials of the first patch electrode 108C-1 and the ground electrode 110C are different, the minimum value of the reflected amplitude is smaller than the minimum value of the reflected amplitude when the materials of both are the same. Similarly, when the materials of the second patch electrode 108C-2 and the ground electrode 110C are different, the minimum value of the reflected amplitude is smaller than the minimum value of the reflected amplitude when the materials of both are the same. In other words, by using different materials for the opposing electrodes, the absorption amount of electromagnetic waves by the electromagnetic wave absorbing device 100C can be increased.

[0134] In this embodiment, the first patch electrode 108C-1 and the second patch electrode 108C-2 are illustrated as having a checkerboard pattern or an alternating arrangement, but are not limited to this structure. For example, the first patch electrode 108C-1 and the second patch electrode 108C-2 may also be arranged as follows: Figure 13 As shown, the first patch electrodes 108C-1 can be adjacent to each other, and the second patch electrodes 108C-2 can also be adjacent to each other.

[0135] [3. Third Implementation]

[0136] Reference Figure 14 and Figure 15 An electromagnetic wave absorption system 10D according to one embodiment of the present invention will be described. The structure of the electromagnetic wave absorption system 10D of the third embodiment is similar to that of the electromagnetic wave absorption system 10 of the first embodiment. In the following description, descriptions of structures identical to those of the electromagnetic wave absorption system 10 will be omitted, and structures different from those of the electromagnetic wave absorption system 10 will be described. When describing structures identical to those of the first embodiment, refer to... Figures 1-10 The letter "D" is added after the reference numerals in these figures for illustrative purposes.

[0137] [3-1. Radio wave absorbing device 100D]

[0138] In the radio wave absorption device 100D of the radio wave absorption system 10D of this embodiment, the following can be used: Figure 8 The unified control method shown and Figure 9Any of the independent control methods shown. In the radio wave absorbing device 100 of the first embodiment, all the patch electrodes 108 provided on the absorbing plate 120 have the same size (e.g., side length). On the other hand, in the radio wave absorbing device 100D of this embodiment, the patch electrodes 108D provided on the absorbing plate 120D are divided into multiple groups, and the size of the patch electrodes 108D is different on a group basis.

[0139] Specifically, such as Figure 14 As shown, the patch electrode 108D is divided into a group consisting of a first patch electrode 108D-3 and a group consisting of a second patch electrode 108D-4. The dimensions of the first patch electrode 108D-3 and the second patch electrode 108D-4 are different. Figure 14 In the example, the size of the first patch electrode 108D-3 is smaller than the size of the second patch electrode 108D-4. The size of the second patch electrode 108D-4 can also be within ±10% of the size of the first patch electrode 108D-3.

[0140] The same control voltage is supplied to the first patch electrode 108D-3 and the second patch electrode 108D-4. That is, the relative permittivity ε (first relative permittivity) of the liquid crystal layer 114D sandwiched between the first patch electrode 108D-3 and the ground electrode 110D is the same as the relative permittivity ε (second relative permittivity) of the liquid crystal layer 114D sandwiched between the second patch electrode 108D-2 and the ground electrode 110D.

[0141] like Figure 14 As shown, the first patch electrode 108D-3 and the second patch electrode 108D-4 are arranged in a checkerboard pattern or an alternating arrangement. That is, the first patch electrode 108D-3 is adjacent to the second patch electrode 108D-4 in all directions (up, down, left, right). Similarly, the second patch electrode 108D-4 is adjacent to the first patch electrode 108D-3 in all directions (up, down, left, right). Figure 14 The arrangement is an example of this embodiment, and this embodiment is not limited to this arrangement.

[0142] [3-2. Simulation results of the 100D electromagnetic wave absorbing device]

[0143] Figure 15 This is a simulation result showing the relationship between the driving method of the electromagnetic wave absorption device and electromagnetic wave absorption in an electromagnetic wave absorption device according to one embodiment of the present invention. Figure 15The simulation results shown are from a simulation of the reflection characteristics of the absorbing plate cells 102D arranged in a 2×2 matrix. The simulation was performed using CST Studio Suite (manufactured by Dassault Systèmes). The parameters of the electromagnetic wave absorbing device 100D used in the simulation are as follows.

[0144] • Spacing of 108D surface mount electrodes: 3mm

[0145] • Dimensions of the first patch electrode 108D-3: 2mm × 2mm

[0146] • Dimensions of the second patch electrode 108D-4: 2.1mm × 2.1mm

[0147] • Thickness of liquid crystal layer 114D: 30μm

[0148] • The relative permittivity ε of liquid crystal layer 114D: 2.5, 3.5

[0149] • Thickness of substrate 101D: 0.8mm

[0150] Figure 15 Two simulation results are shown. These simulation results are for different relative permittivity conditions of the liquid crystal layer 114D (relative permittivity ε = 2.5 and 3.5). Figure 15 In the diagram, dashed lines represent simulation results when the relative permittivity ε is 2.5, and solid lines represent simulation results when the relative permittivity ε is 3.5. In the electromagnetic wave absorbing device 100D, the simulation result when the relative permittivity ε is 2.5 corresponds to the simulation result when no control voltage is supplied to the patch electrode 108D and the ground electrode 110D (the potential difference between the two electrodes is zero). On the other hand, the simulation result when the relative permittivity ε is 3.5 corresponds to the simulation result when a control voltage is supplied to the patch electrode 108D and the ground electrode 110D. The relative permittivity ε can be adjusted within the range of 2.5 to 3.5 depending on the control voltage supplied to the patch electrode 108D and the ground electrode 110D.

[0151] like Figure 15 As shown, regardless of the value of the relative permittivity ε, the spectrum representing the reflection amplitude has two local minima. As a result, compared to... Figure 5 Compared to the simulation results shown, Figure 15 The simulation results show that the electromagnetic wave absorbing device 100D can absorb a wider frequency band of electromagnetic waves. That is, as described above, by varying the size of the patch electrode 108D, the frequency band of electromagnetic waves that the electromagnetic wave absorbing device 100D can absorb can be extended. Figure 13Therefore, the arrangement of the first patch electrode 108D-3 and the second patch electrode 108D-4 can be such that the first patch electrode 108D-3 is arranged adjacent to each other, or the second patch electrode 108D-4 is arranged adjacent to each other.

[0152] [4. Fourth Implementation]

[0153] Reference Figure 16 An electromagnetic wave absorption system 10E according to one embodiment of the present invention will be described. The structure of the electromagnetic wave absorption system 10E of the fourth embodiment is similar to that of the electromagnetic wave absorption system 10 of the first embodiment. In the following description, descriptions of structures identical to those of the electromagnetic wave absorption system 10 will be omitted, and structures different from those of the electromagnetic wave absorption system 10 will be described. When describing structures identical to those of the first embodiment, refer to... Figures 1-10 The letter "E" is added after the reference numerals in these figures for illustrative purposes.

[0154] [4-1. Simulation results of the radio wave absorbing device 100E]

[0155] In the electromagnetic wave absorption device 100E of the electromagnetic wave absorption system 10E in this embodiment, the following can be used: Figure 8 The unified control method shown and Figure 9 Any of the independent control methods shown. In the radio wave absorption device 100E of this embodiment, a substrate 101E with a thickness suitable for absorbing radio waves is provided.

[0156] Figure 16 This is a simulation result showing the relationship between the thickness of the substrate and the electromagnetic wave absorption in an electromagnetic wave absorption device according to one embodiment of the present invention. Figure 16 The simulation results shown are from a simulation of the reflection characteristics of an absorbing plate cell 102E. The simulation was performed using CST Studio Suite (manufactured by Dassault Systèmes). The parameters of the electromagnetic wave absorbing device 100E used in the simulation are as follows.

[0157] • Spacing of the 108E surface mount electrodes: 3mm

[0158] • Dimensions of the 108E surface mount electrode: 2mm × 2mm

[0159] • Thickness of liquid crystal layer 114E: 30μm

[0160] • The relative permittivity ε of the 114E liquid crystal layer: 2.5, 3.5

[0161] • Thickness of substrate 101E: 0.2mm~2.0mm

[0162] Figure 16 In such Figure 5 The simulation results shown plot the minimum values ​​of the reflection amplitude under various conditions. Figure 16 In the graph shown, the vertical axis represents the reflection amplitude, and the horizontal axis represents the thickness (T) of the substrate 101E relative to the wavelength of the electromagnetic wave used as a simulation parameter, divided by the wavelength (λ) of the electromagnetic wave propagating in the substrate 101E. g The value obtained (T / λ) g ). Figure 16 The value of the reflection amplitude is the average of the minimum reflection amplitude when the relative permittivity ε of the liquid crystal layer 114E is 2.5 and the minimum reflection amplitude when the relative permittivity ε is 3.5. For example... Figure 16 As shown, the minimum value of the reflection amplitude exhibits a periodic variation with the thickness of the substrate 101E. This variation can be attributed to the interference effect of the electromagnetic waves reflected by the electromagnetic wave absorption device 100E. Specifically, the reflection amplitude tends to decrease when the thickness T of the substrate 101E is different from 1 / 4 of the wavelength of the electromagnetic wave incident on the electromagnetic wave absorption device 100E. More specifically, when the thickness T of the substrate 101E is λ... g / 8+(n-1)λ g Under the condition of λ / 4, the reflected amplitude tends to decrease. Therefore, for example, by setting the thickness of the substrate 101E to λ / 8, the apparent amount of electromagnetic wave absorption of the electromagnetic wave absorption device 100E can be increased according to the interference effect of the reflected wave.

[0163] [5. Fifth Implementation]

[0164] Reference Figure 17 An electromagnetic wave absorption system 10F according to one embodiment of the present invention will be described. The structure of the electromagnetic wave absorption system 10F of the fifth embodiment is similar to that of the electromagnetic wave absorption system 10 of the first embodiment. In the following description, descriptions of structures identical to those of the electromagnetic wave absorption system 10 will be omitted, and structures different from those of the electromagnetic wave absorption system 10 will be described. When describing structures identical to those of the first embodiment, refer to... Figures 1-10 The letter "F" is added after the reference numerals in these figures for illustrative purposes.

[0165] [5-1. Simulation results of the 100F electromagnetic wave absorption device]

[0166] In the electromagnetic wave absorption device 100F of the electromagnetic wave absorption system 10F of this embodiment, the following can be used: Figure 8 The unified control method shown and Figure 9 Any of the independent control methods shown. In the radio wave absorbing device 100F of this embodiment, a liquid crystal layer 114F with a thickness suitable for absorbing radio waves is provided.

[0167] Figure 17 This is a simulation result showing the relationship between the thickness of the substrate and the electromagnetic wave absorption in an electromagnetic wave absorption device according to one embodiment of the present invention. Figure 17 The simulation results shown are from a simulation of the reflection characteristics of an absorbing cell 102F. The simulation was performed using CST Studio Suite (manufactured by Dassault Systèmes). The parameters of the electromagnetic wave absorbing device 100F used in the simulation are as follows.

[0168] • Spacing of the 108F surface mount electrodes: 3mm

[0169] • Dimensions of the 108F surface mount electrode: 2mm × 2mm

[0170] • Thickness of the 114F liquid crystal layer: 5μm~70μm

[0171] • The relative permittivity ε of the 114F liquid crystal layer: 2.5, 3.5

[0172] • Thickness of substrate 101F: 0.8mm

[0173] Figure 17 Is with Figure 16 Similarly, graphs were plotted showing the minimum values ​​of the reflection amplitude under each condition. Figure 17 In the chart shown, the horizontal axis represents the thickness of the 114F liquid crystal layer. Figure 17 The value of the reflection amplitude is the average of the minimum reflection amplitude when the relative permittivity ε of the liquid crystal layer 114F is 2.5 and the minimum reflection amplitude when the relative permittivity ε is 3.5. For example... Figure 17 As shown, by adjusting the thickness of the liquid crystal layer 114F to a range of 10μm to 40μm, the amount of electromagnetic wave absorption by the electromagnetic wave absorption device 100F can be increased.

[0174] [6. Sixth Implementation]

[0175] Reference Figure 18 and Figure 19 An embodiment of the electromagnetic wave absorbing device 100G according to the present invention will be described. The structure of the electromagnetic wave absorbing device 100G of the sixth embodiment is similar to that of the electromagnetic wave absorbing device 100 of the first embodiment. In the following description, descriptions of structures identical to those of the electromagnetic wave absorbing device 100 will be omitted, and descriptions of structures different from those of the electromagnetic wave absorbing device 100 will be provided. In the following description, when describing structures identical to those of the first embodiment, refer to... Figures 1-10 exist Figures 1-10 The attached figures are labeled with the letter "G" for illustrative purposes.

[0176] [6-1. Radio wave absorption device 100G]

[0177] Figure 18 This is a cross-sectional view illustrating an embodiment of an electromagnetic wave absorbing device according to the present invention. Figure 18 As shown, the radio wave absorbing device 100G includes multiple absorbing elements (absorbing plate cells) 102G. The multiple absorbing plate cells 102G are arranged along at least one direction. Figure 18 In this structure, multiple absorber cells 102G are arranged along the Y-axis. The electromagnetic wave absorption device 100G includes a dielectric substrate 104G, a counter substrate 106G, a driving electrode 109G (counter electrode), a patch electrode 111G, a liquid crystal layer 114G, a sealing material 128G, a switching element 134G, a terminal portion 126G, and an FPG 160G. The liquid crystal layer 114G contains liquid crystal molecules 116G. In this structure, the electrode 111G located on the counter substrate 106G side functions as a patch electrode for absorbing electromagnetic waves. The liquid crystal is aligned based on the potential difference between the potential applied to the driving electrode 109G and the potential applied to the patch electrode 111G, thereby changing the dielectric constant. A passivation layer 158G is provided between the driving electrode 109G and the dielectric substrate 104G.

[0178] The absorber cell 102G includes at least a driving electrode 109G, a surface mount electrode 111G, a liquid crystal layer 114G, and a switching element 134G. The surface mount electrode 111G... Figure 18 It appears to be set up independently for each 102G absorption plate cell, but in reality... Figure 19 The diagram shows multiple absorber cells 102G shared together. A driving electrode 109G is located on the dielectric substrate 104G side. The driving electrode 109G is opposite to the patch electrode 111G and is independently provided for each absorber cell 102G. The patch electrode 111G is located on the opposing substrate 106G side.

[0179] Switching element 134G is connected to drive electrode 109G. Figure 18 In this configuration, the driving electrode 109G is arranged on the switching element 134G in a manner overlapping with the switching element 134G. This makes the switching element 134G less susceptible to electromagnetic interference. The switching element 134G is controlled by the driving circuit 600G (see reference). Figure 1 The orientation of the liquid crystal molecule 116G is controlled according to the driving state of the switching element 134G. As described above, by controlling the orientation of the liquid crystal molecule 116G, the frequency band of the radio waves absorbed by the radio wave absorbing device 100G can be adjusted.

[0180] As described above, in the case of the electromagnetic wave absorbing device 100G of this embodiment, since the electromagnetic waves incident on the electromagnetic wave absorbing device 100G are shielded or absorbed by the patch electrode 111G, it is possible to suppress adverse effects such as heat generation in the switching element 134G due to the irradiation of the electromagnetic waves.

[0181] [6-2. Driving electrode 109G]

[0182] Figure 19 This is a top view illustrating the outline of the patch electrodes of an electromagnetic wave absorption device according to one embodiment of the present invention. Figure 19 As shown, the patch electrode 111G includes a resonant part 1111G and a connecting part 1112G.

[0183] The resonant section 1111G is the part that resonates with the wavelength of the electromagnetic wave incident on the electromagnetic wave absorption device 100G, and is arranged in a matrix in the X-axis and Y-axis directions. The size of the resonant section 1111G in the X-axis and Y-axis directions is calculated using the dielectric constant of the liquid crystal layer 114G, in addition to the wavelength of the electromagnetic wave.

[0184] The connecting portion 1112G connects adjacent resonant portions 1111G in the X-axis or Y-axis direction. The resonant portions 1111G, arranged in a matrix, are electrically connected by the connecting portion 1112G. Therefore, the resonant portions 1111G arranged in a matrix are at the same potential. The connecting portion 1112G has a long side (length direction along the Y-axis) in either the X-axis or Y-axis direction. The connecting portion 1112G connecting adjacent resonant portions 1111G in the X-axis direction has a long side (length direction along the X-axis) in the X-axis direction. The connecting portion 1112G connecting adjacent resonant portions 1111G in the Y-axis direction has a long side (length direction along the Y-axis) in the Y-axis direction.

[0185] The width of the connecting portion 1112G, which has a long side in the X-axis direction (width in the Y-axis direction), is less than 1 / 100 of the size of the resonant portion 1111G in the Y-axis direction. By having this structure, the connecting portion 1112G can reduce its influence on the resonance of the resonant portion 1111G.

[0186] As an embodiment of the present invention, the various structures of the radio wave absorbing device and absorbing plate unit illustrated herein can be appropriately combined as long as they do not contradict each other. Furthermore, based on the radio wave absorbing device and absorbing plate unit disclosed in this specification and drawings, any additions, deletions, or design changes to constituent elements, or additions, omissions, or changes to processes performed by those skilled in the art, as long as they capture the essence of the present invention, are also included within the scope of the present invention.

[0187] Even if other effects are different from those of the embodiments disclosed in this specification, effects that are known from the description in this specification or that can be easily predicted by those skilled in the art can of course be understood as being caused by the present invention.

[0188] Explanation of reference numerals in the attached figures

[0189] 10: Electromagnetic wave absorption system; 100: Electromagnetic wave absorption device; 101: Substrate; 102: Absorbing plate cell; 104: Dielectric substrate; 106: Opposing substrate; 108: Patch electrode; 108C-1: First patch electrode; 108C-2: Second patch electrode; 108D-3: First patch electrode; 108D-4: Second patch electrode; 109G: Driving electrode; 110: Ground electrode; 111G: Patch electrode; 112a: First alignment film; 112b: Second alignment film; 114: Liquid crystal layer; 116: Liquid crystal molecule; 118: First wiring; 119: Second wiring; 120: Absorbing plate; 122: Peripheral area; 124: First driving circuit; 12 6: Terminal section; 128: Sealing material; 130: Second drive circuit; 132: Second wiring; 134: Switching element; 136: Base coating; 138: First gate; 140: First gate insulating layer; 142: Semiconductor layer; 144: First connection wiring; 146: Second gate insulating layer; 148: Second gate; 150: First interlayer insulating layer; 152: Second connection wiring; 154: Second interlayer insulating layer; 156: Planarization layer; 158: Passivation layer; 162: Electron wave absorption region; 164: Peripheral region; 500: Control circuit; 600: Drive circuit; 1000, 1100: Simulation results; 1111G: Resonant section; 1112G: Connection section.

Claims

1. An electromagnetic wave absorbing device, characterized in that, include: Patch electrodes; The opposing electrode is opposite to the patch electrode and is made of a different material than the patch electrode; and The liquid crystal layer between the patch electrode and the counter electrode.

2. The electromagnetic wave absorbing device according to claim 1, characterized in that, The conductivity of the material constituting the patch electrode is different from the conductivity of the material constituting the counter electrode.

3. The electromagnetic wave absorbing device according to claim 1, characterized in that, The ratio of the conductivity of the material constituting the patch electrode to the conductivity of the material constituting the counter electrode is more than 10 times.

4. The electromagnetic wave absorbing device according to claim 1, characterized in that, When the patch electrode is made of a metallic material, the counter electrode is made of a transparent conductive material. When the patch electrode is made of a transparent conductive material, the counter electrode is made of a metal material.

5. An electromagnetic wave absorbing device, characterized in that, include: First patch electrode; The second patch electrode can be controlled independently of the first patch electrode; Opposite electrode, which is opposite to the first patch electrode and the second patch electrode; and The liquid crystal layer between the first patch electrode and the counter electrode, and between the second patch electrode and the counter electrode. The first relative permittivity of the liquid crystal layer sandwiched by the first patch electrode and the counter electrode is different from the second relative permittivity of the liquid crystal layer sandwiched by the second patch electrode and the counter electrode.

6. The electromagnetic wave absorbing device according to claim 5, characterized in that, The material constituting the first patch electrode is different from the material constituting the counter electrode. The material constituting the second patch electrode is different from the material constituting the counter electrode.

7. The electromagnetic wave absorbing device according to claim 5, characterized in that, The ratio of the conductivity of the material constituting the patch electrode to the conductivity of the material constituting the counter electrode is more than 10 times.

8. The electromagnetic wave absorbing device according to claim 5, characterized in that, When the patch electrode is made of a metallic material, the counter electrode is made of a transparent conductive material. When the patch electrode is made of a transparent conductive material, the counter electrode is made of a metal material.

9. The radio wave absorbing device according to any one of claims 1 to 8, characterized in that, It also includes a substrate disposed on the side where the electromagnetic wave is incident relative to the electromagnetic wave absorbing device, with the liquid crystal layer as a reference. The thickness of the substrate is different from λ / 4 relative to the wavelength λ of the electromagnetic wave incident on the electromagnetic wave absorbing device.

10. The radio wave absorbing device according to any one of claims 1 to 8, characterized in that, The thickness of the liquid crystal layer is more than 10 μm and less than 40 μm.

11. The radio wave absorbing device according to any one of claims 1 to 4, characterized in that, The patch electrode includes a first patch electrode and a second patch electrode. The size of the first patch electrode is different from the size of the second patch electrode.

12. The electromagnetic wave absorbing device according to any one of claims 5 to 8, characterized in that, The size of the first patch electrode is different from the size of the second patch electrode.

13. An electromagnetic wave absorption system, characterized in that, have: The electromagnetic wave absorbing device according to any one of claims 1 to 4; and A control device that controls the voltage supplied to the patch electrode and the counter electrode. The control device controls the voltage supplied to the patch electrode and the counter electrode to change the amount of electromagnetic wave absorption by the electromagnetic wave absorption device for electromagnetic waves of any frequency.

14. The radio wave absorption system according to claim 13, characterized in that, The control device receives a set value related to the frequency of the electromagnetic waves absorbed by the electromagnetic wave absorption device, and controls the voltage supplied to the patch electrode and the counter electrode based on the set value.

15. An electromagnetic wave absorption system, characterized in that, have: The electromagnetic wave absorbing device according to any one of claims 5 to 8; and A control device that controls the voltage supplied to the first patch electrode, the second patch electrode, and the counter electrode. The control device controls the voltage supplied to the first patch electrode, the second patch electrode, and the counter electrode to change the amount of electromagnetic wave absorption by the electromagnetic wave absorption device for electromagnetic waves of any frequency.

16. The radio wave absorption system according to claim 15, characterized in that, The control device receives a set value related to the frequency of the electromagnetic waves absorbed by the electromagnetic wave absorption device, and controls the voltage supplied to the patch electrode and the counter electrode based on the set value.

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