Transmission frequency changing mechanism

Abstract

The objective is to provide a transmission frequency changing mechanism that can change the transmission wavelength band of radio waves. [Solution] A transmission frequency changing mechanism capable of changing the frequency of transmitted radio waves is provided, comprising a sheet member and an actuator, wherein the sheet member is configured to be expandable and contractible from a first expanded / contracted state to a second expanded / contracted state, and the sheet member is configured such that the wavelength band transmitted by radio waves in the first expanded / contracted state and the wavelength band transmitted by radio waves in the second expanded / contracted state change, the width of the sheet member in the expansion / contraction direction in the second expanded / contracted state is longer than the width of the sheet member in the expansion / contraction direction in the first expanded / contracted state, and the actuator is configured to expand and contract the sheet member between the first expanded / contracted state and the second expanded / contracted state.

Description

Technical Field

[0004] ,

[0006] , , , , ,

[0005] , , , , ,

[0001] The present invention relates to a transmission frequency changing mechanism.

Background Art

[0002] Conventionally, in radar systems and communication systems, in order to protect an antenna operating in a high frequency band (for example, the 240 GHz band), a radome having a protection function from the external environment has been used (for example, see Patent Document 1). The radome is required to ensure both physical protection of the antenna and radio wave transmission performance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, the design of a radio wave transmission member such as a radome is a fixed one that ensures radio wave transmission in a desired frequency range, and there is a problem that it is difficult to flexibly operate according to the situation.

[0005] An object of the present invention is to provide a transmission frequency changing mechanism capable of changing the transmission wavelength band of radio waves.

Means for Solving the Problems

[0006] [[ID=(45)]] According to the present invention, a transmission frequency changing mechanism capable of changing the frequency of transmitted radio waves is provided, comprising a sheet member and an actuator, wherein the sheet member is configured to be expandable and contractible from a first expanded / contracted state to a second expanded / contracted state, and the sheet member is configured such that the wavelength band transmitted by radio waves in the first expanded / contracted state and the wavelength band transmitted by radio waves in the second expanded / contracted state change, the width of the sheet member in the expansion / contraction direction in the second expanded / contracted state is longer than the width of the sheet member in the expansion / contraction direction in the first expanded / contracted state, and the actuator is configured to expand and contract the sheet member between the first expanded / contracted state and the second expanded / contracted state.

[0007] According to the present invention, the invention provides a sheet member configured such that the wavelength band through which radio waves are transmitted in a first stretched state and the wavelength band through which radio waves are transmitted in a second stretched state change, and an actuator for stretching the sheet member, thereby making it possible to change the wavelength band through which radio waves are transmitted. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1A is a schematic cross-sectional view of the transmission frequency changing mechanism 100 according to an embodiment, showing the sheet member 10 in its natural length state. Figure 1B shows the sheet member 10 of the transmission frequency changing mechanism 100 shown in Figure 1A stretched by approximately 30% in the expansion and contraction direction. [Figure 2] Figure 2A is a plan view of an example of the resistive layer r shown in Figure 1A. Figure 2B is a plan view of the resistive layer r with a different configuration than Figure 2A. [Figure 3] Figures 3A and 3B are explanatory diagrams showing the transmission characteristics of radio waves when the radio waves incident on the sheet member 10 shown in Figures 1A and 1B are in TE mode. Figure 3A shows the transmission characteristics of radio waves in the state shown in Figure 1A (when the sheet member 10 is at its natural length). Figure 3B shows the transmission characteristics of radio waves in the state shown in Figure 1B (when the sheet member 10 is stretched by about 30%). [Figure 4]Figures 4A and 4B are explanatory diagrams showing the transmission characteristics of radio waves when the radio waves incident on the sheet member 10 shown in Figures 1A and 1B are in TM mode. Figure 4A shows the transmission characteristics of radio waves in the state shown in Figure 1A (sheet member 10 at its natural length). Figure 4B shows the transmission characteristics of radio waves in the state shown in Figure 1B (sheet member 10 stretched by about 30%). Note that the results in Figures 3A and 4A are the same graph, differing only in the scale of the vertical axis. [Figure 5] Figure 5A is a graph of the sheet member 10 in its natural length state, showing the results of sequentially changing the resistance value (Ω / sq) of the resistive layer r from 0.2 to 10 (0.2, 0.7, 1.2, 1.7, 2.2, 2.7, 3.2, 3.7, 4.2, 4.7, 5.2, 10). The analysis conditions are the same as in Figures 3A and 4A. Figure 5B is an enlarged view of the main part of the area indicated by the arrow in Figure 5A. [Figure 6] Figure 6A is a graph showing the case where the incident radio wave is in TE mode and the sheet member 10 is stretched by about 30%. Figure 6A shows the results of sequentially changing the resistance value (Ω / sq) of the resistive layer r from 0.2 to 10.2 (0.2, 0.7, 1.2, 1.7, 2.2, 2.7, 3.2, 3.7, 4.2, 4.7, 5.2, 5.7, 6.2, 6.7, 7.2, 7.7, 8.2, 8.7, 9.2, 9.7, 10.2). In Figure 6B, the graphs for each resistance value are sequentially arranged from the graph for 0.2 to the graph for 10.2 in the direction indicated by the arrow in Figure 6B. The analysis conditions are the same as in the case of Figure 3B. Figure 6B is an enlarged view of the main part of the area indicated by the arrow in Figure 6A. [Figure 7]Figure 7A is a graph showing the case where the incident radio wave is in TM mode and the sheet member 10 is stretched by about 30%. Figure 7A shows the results of sequentially changing the resistance value (Ω / sq) of the resistive layer r from 0.2 to 10.2 (0.2, 0.7, 1.2, 1.7, 2.2, 2.7, 3.2, 3.7, 4.2, 4.7, 5.2, 5.7, 6.2, 6.7, 7.2, 7.7, 8.2, 8.7, 9.2, 9.7, 10.2). In Figure 7B, the graphs for each resistance value are sequentially arranged from the graph for 0.2 to the graph for 10.2 in the direction indicated by the arrow in Figure 7B. The analysis conditions are the same as in the case of Figure 4B. Figure 7B is an enlarged view of the main part of the area indicated by the arrow in Figure 7A. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings. The various features shown in the embodiments below can be combined with each other. Furthermore, each feature can stand alone as an independent invention.

[0010] 1. Description of the Configuration of the Embodiment The configuration of the transmission frequency changing mechanism 100 according to the embodiment will be described with reference to Figures 1A and 1B. Note that Figures 1A and 1B are schematic diagrams provided to facilitate understanding of the configuration of the transmission frequency changing mechanism 100, and the sizes of the components shown in the figures, particularly the thickness of each layer, are not necessarily accurate representations of reality.

[0011] The transmission frequency changing mechanism 100 is, for example, a radome that protects radar equipment and antennas used in the high-frequency band. The term "radome" is a combination of "radar" and "dome," and it is an exterior component (cover) for protecting radar equipment and antennas. The radome needs to have the property of transmitting radio waves of a desired frequency (frequency band) so as not to interfere with the internal radar equipment and antenna when they transmit and receive radio waves. Furthermore, the radome is made of a material that can protect the internal electronic equipment (radar equipment, antennas, etc.) from external environmental factors such as rain, wind, and impacts, and can be made of, for example, dielectric material and / or glass fiber reinforced plastic (FRP).

[0012] The transmission frequency changing mechanism 100 comprises a sheet member 10 and an actuator 20 attached to the sheet member 10. The actuator 20 changes the length of the sheet member 10 in the expansion and contraction direction, thereby changing the frequency (frequency band) of the transmitted radio waves. Furthermore, in this embodiment, the frequency characteristics can be varied by deformation caused by stretching the frequency-selective surface (described later), and the resulting changes in size and array spacing. The configuration according to this embodiment can be applied as a frequency-variable filter or switch. In addition, it is possible to design a suppression filter between the TE mode and TM mode of radio waves (the characteristics can be adjusted, for example, by polarization, to transmit or block them).

[0013] 1-1. Sheet member 10 The sheet member 10 has a laminate 10s. The sheet member 10 may have only the laminate 10s, or it may have, in addition to the laminate 10s, another layer member (for example, a member for reinforcing the sheet member 10). The laminate 10s is formed as a flexible sheet.

[0014] The thickness (mm) of the laminate 10s is specifically, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, and may be within the range between any two of the values exemplified herein.

[0015] The sheet member 10 is configured to be able to change the frequency of the radio wave to be transmitted. Specifically, as shown in FIG. 1A, the laminate 10s has a dielectric layer d1 (an example of the first dielectric layer), a resistance layer r, and a dielectric layer d2 (an example of the second dielectric layer), and these layers are arranged in this order from the radio wave incident side. The resistance layer r, as will be described later, has a structure in which a so-called frequency selective surface is formed, and the frequency of the radio wave passing (transmitting) through it is a predetermined frequency. The resistance layer r, which is a frequency selective surface, expands and contracts, so that the shape of the structure formed in the resistance layer r changes and the frequency characteristics of the resistance layer r change. As a result, the frequency of the radio wave passing through (the frequency of the radio wave absorbed) changes.

[0016] The sheet member 10 is configured to be able to change the transmission / non-transmission (passage / non-passage) of radio waves of a desired wavelength (wavelength band) according to, for example, the radio wave characteristics of the radio wave interference type (λ / 4 type). The radio wave characteristics of the radio wave interference type (absorption radio wave characteristics) are explained, for example, when the thickness of the dielectric layer with a dielectric constant of ε is d and the wavelength in the dielectric of the radio wave to be absorbed is λ (= 1 / frequency), as d = λ / 4 = πc / (2ω√ε).

[0017] For example, among the radio waves incident on the dielectric layer d1, which is a surface dielectric layer, the radio waves of a predetermined frequency pass through the resistance layer r, and the others are reflected by the resistance layer r. The radio waves incident on the sheet member 10 interfere with the radio waves reflected by the resistance layer r, so that they do not pass through the sheet member 10 (are absorbed). That is, since the phases of the radio waves incident on the sheet member 10 and the reflected radio waves are different (ideally, completely opposite), the radio waves are attenuated, and seemingly, the radio waves are absorbed in the sheet member 10.

[0018] The sheet member 10 is configured to be stretchable in the stretching direction to a plurality of length states. For example, the sheet member 10 is configured to be stretchable from the stretching state shown in FIG. 1A (an example of the first stretching state) to the stretching state shown in FIG. 1B (an example of the second stretching state). Note that the width of the sheet member 10 in the stretching direction in the stretching state shown in FIG. 1B is longer than the width of the sheet member 10 in the stretching direction in the stretching state shown in FIG. 1A. Specifically, in the stretching state shown in FIG. 1A, the sheet member 10 is at its natural length. In the stretching state shown in FIG. 1B, the sheet member 10 is in a state stretched by about 30% from the state shown in FIG. 1A. The stretching direction is not limited. For example, the direction having the periodicity of the resistance layer r having a periodic structure described later (for example, in the case of FIG. 2A, not only the direction corresponding to the lateral width W2 but also the direction corresponding to the vertical width W1) can be set as the stretching direction.

[0019] When the sheet member 10 is stretched and contracted, the shape of the structure of the resistance layer r changes. As a result, the sheet member 10 is configured such that the wavelength (wavelength band) through which the radio wave passes in the stretching state shown in FIG. 1A and the wavelength (wavelength band) through which the radio wave passes in the stretching state shown in FIG. 1B change. Note that when the sheet member 10 is stretched and contracted, the thickness of the sheet member 10 changes, and as a result, the radio wave characteristics of the radio wave interference type (λ / 4 type) change, and the change in the transmission / non-transmission wavelength (wavelength band) described above may also occur. However, it is preferable that various configurations (for example, the configuration of the resistance layer r, the configuration of the thickness and dielectric constant of the sheet member 10, etc.) are such that this change does not cancel out the change in the transmission / non-transmission wavelength (wavelength band) caused by the change in the shape of the structure of the resistance layer r.

[0020] In the above description, the amount of expansion and contraction of the sheet member 10 is described as 30% of the natural length of the sheet member 10, but it is not limited thereto. The amount of expansion and contraction is the difference between the length of the stretched sheet member 10 and the length of the sheet member 10 at its natural length. The reference for the amount of expansion and contraction is the length of the sheet member 10 at its natural length. For example, if the natural length of the sheet member 10 is, for example, 10 cm, and it is stretched by 20%, the amount of stretching or shrinking is converted to length as 2 cm (the length of the stretched sheet member 10 is 12 cm). The amount of expansion or contraction of the sheet member 10 is specifically, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 (%) of the natural length of the sheet member 10, and may be within the range of any two of the values ​​exemplified here.

[0021] The radio wave non-transmitting (non-through) characteristics of the sheet member 10 are such that the radio wave absorption rate has a peak in the frequency range of 50 GHz to 300 GHz. Specifically, the peak frequency of the non-transmitting wavelength band of the sheet member 10 in the stretched state shown in Figure 1A is defined as the first peak frequency. The peak frequency of the non-transmitting wavelength band of the sheet member 10 in the stretched state shown in Figure 1B is defined as the second peak frequency. In this case, the first peak frequency and the second peak frequency are different. In this embodiment, the first peak frequency is lower than the second peak frequency. Preferably, the first peak frequency and the second peak frequency are within the frequency range of 50 GHz to 300 GHz.

[0022] Here, it is preferable that the first peak frequency and the second peak frequency are separated by 5 GHz or more, but it is not limited to this. Specifically, for example, it is preferable that the first peak frequency and the second peak frequency are separated by 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50 GHz or more, and the difference between the first peak frequency and the second peak frequency may be defined within the range between any two of the values ​​exemplified here.

[0023] The reflection attenuation (radio wave absorption rate) of radio waves at the first and second peak frequencies is preferably 80% or higher. The return loss (radio wave absorption rate) corresponds to the ratio of the amount of radio waves absorbed to the amount of radio waves of any given frequency incident on the sheet member 10. The quantity of radio waves can be expressed, for example, by converting radio waves into electrical power. A radio wave absorption rate of 80% is equivalent to approximately 7 dB, while a radio wave absorption rate of 90% is equivalent to 10 dB. Furthermore, the reflection attenuation (radio wave absorption rate) of radio waves at the first and second peak frequencies is not limited to these values. Specifically, it is preferable that the values ​​be 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, or 99% or higher, and may be specified within the range between any two of the values ​​exemplified here.

[0024] Furthermore, the first characteristic peaking at the first peak frequency in the stretched state shown in Figure 1A has a first frequency range where the radio wave reflection attenuation is 80% or more. Also, the second characteristic peaking at the second peak frequency in the stretched state shown in Figure 1B has a second frequency range where the radio wave reflection attenuation is 80% or more.

[0025] The first frequency range is preferably included within the frequency range of 50 GHz to 300 GHz. The second frequency range is also preferably included within the frequency range of 50 GHz to 300 GHz. The first and second frequency ranges may overlap in part, but their respective peak frequencies (first peak frequency and second peak frequency) are different.

[0026] When the lower limit of the first frequency range is set to f1m and the upper limit to f1M, the sheet member 10 can be configured such that f1m and f1M (GHz) can take on values ​​such as 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, 255, 260, 265, 270, 275, 280, 285, 290, 295, and 300. At this time, f1m <f1Mである。

[0027] Furthermore, when the lower limit of the first frequency range is set to f2m and the upper limit to f2M, the sheet member 10 can be configured such that f2m and f2M (GHz) can take on values ​​such as 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, 255, 260, 265, 270, 275, 280, 285, 290, 295, and 300. At this time, f2m <f2Mである。

[0028] The first and second frequency ranges preferably have a width of 5 GHz or more. This width corresponds to the difference between f1M and f1m, and the difference between f2M and f2m, as described above. This width (GHz) is not limited to this, and specifically, the sheet member 10 can be configured to take values ​​such as 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, and 150. Note that this width may be defined within the range between any two of the values ​​exemplified here.

[0029] In this embodiment, a sheet member 10 is described assuming the use of the above-mentioned frequency (GHz band frequency range), but it is not limited to this, and the sheet member 10 having the layer structure of the embodiment can also be applied to the absorption of radio waves in the MHz band or lower.

[0030] Furthermore, it is preferable that in at least one of the expanded / contracted states shown in Figure 1A and Figure 1B, the input impedance value of the sheet member 10 matches the impedance value of the air. This allows radio waves of the target frequency to properly enter the sheet member 10 without being reflected at the surface and reach the resistive layer r, making it easier to match the transmission / non-transmission of radio waves to the desired target frequency.

[0031] 1-1-1. Dielectric layers (dielectric layer d1 and dielectric layer d3) The dielectric layers d1 and d3 sandwich the resistive layer r so as to protect it. Various dielectric materials can be used for the dielectric layers d1 and d3. The dielectric materials constituting dielectric layers d1 and d3 may include polymer materials. These polymer materials may be synthetic resins (including thermoplastic elastomers) such as polyvinyl chloride, polyvinylidene fluoride, acrylic resin, ethylene vinyl acetate copolymer, polyurethane, acrylic urethane resin, ionomer, polyolefin, polypropylene, polyethylene, silicone resin, polyester, polystyrene, polyimide, polyamide, polysulfone, polyethersulfone, and epoxy resin, or synthetic rubbers such as polyisoprene rubber, polystyrene-butadiene rubber, polybutadiene rubber, chloroprene rubber, acrylonitrile butadiene rubber, butyl rubber, acrylic rubber, ethylene propylene rubber, and silicone rubber. These may be used individually or in combination of two or more to constitute the polymer material. The dielectric layers may also be made of materials such as glass, titanium oxide, alumina, and barium titanate.

[0032] Furthermore, it is preferable that dielectric layers d1 and d3 contain a material that is stretchable (flexible). Specifically, it is preferable that they contain stretchable materials such as rubber-based materials or elastomers, as described below. In other words, dielectric layers d1 and d3 can be composed of a material obtained by mixing the dielectric material for imparting dielectric properties and the stretchable material for imparting stretchability, as described above. Furthermore, if the stretchable material also has suitable dielectric properties, it is not necessary to mix in a separate dielectric material. Examples of stretchable materials include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, butyl rubber, nitrile rubber, ethylene-propylene rubber, chloroprene rubber, acrylic rubber, chlorosulfonated polyethylene rubber, urethane rubber, silicone rubber, fluororubber, ethylene-vinyl acetate rubber, epichlorohydrin rubber, polysulfide rubber, etc.

[0033] The constituent materials of dielectric layer d1 and dielectric layer d3 may be the same or different.

[0034] In addition, while the above describes how stretchability can be imparted by modifying the constituent materials, flexibility can also be imparted by forming a lattice structure or pattern structure in the dielectric layer, or by foaming the dielectric layer to make it porous and thus imparting stretchability.

[0035] The relative permittivity of dielectric layers d1 and d3 can be set as appropriate, but specifically, for example, they can be 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, or 10, and may also be within the range of any two of the values ​​exemplified here. The relative permittivity of dielectric layer d1 and dielectric layer d3 may be the same or different.

[0036] The thickness (μm) of dielectric layers d1 and d3 can be, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1500, 2000, 2500, 3000, 4000, 4500, 5000, 6000, 7000, 8000, 9000, 10000, and may be within the range of any two of the values ​​exemplified here. The thicknesses of dielectric layer d1 and dielectric layer d3 may be the same or different.

[0037] Each dielectric layer (dielectric layer d1 and dielectric layer d3) may be composed of multiple dielectric layers stacked on top of each other.

[0038] 1-1-2.Resistance layer The resistive layer r has functions related to the reflection and transmission of radio waves. The resistive layer r also has a function related to the selection of the frequencies of radio waves that are transmitted. Since the sheet member 10 has at least one resistive layer r, it is possible to interfere with radio waves to allow radio waves of a desired frequency to pass through and radio waves of different frequencies to not pass through. In this embodiment, the sheet member 10 is shown as an example in which it has only one resistive layer r, but it is not limited to this, and there may be another resistive layer sandwiched between dielectric layers. In other words, the sheet member 10 may have two or more resistive layers r.

[0039] Figures 1A and 1B show examples of the shape of the resistive layer r when viewed from above (Figures 1A and 1B have different configurations). In both Figure 1A and Figure 1B, the resistive layer r has a periodic structure rs, and this periodic structure rs is formed to have periodicity within the plane of the resistive layer r so as to allow radio waves of a predetermined frequency (a predetermined frequency band) to pass through. In other words, the resistive layer r has a structure with a frequency-selective surface (patch-type resonator structure).

[0040] Here, in the expanded / contracted state shown in Figure 1A, the predetermined frequency range through which the resistive layer r passes can be defined as a frequency range other than the first frequency range described above, within the range of 50 to 300 (GHz). Furthermore, in the expanded / contracted state shown in Figure 1B, the predetermined frequency range through which the resistive layer r passes can be defined as a frequency range other than the second frequency range described above, within the range of 50 to 300 (GHz). The predetermined frequency range through which the resistive layer r passes may be divided into multiple frequency ranges.

[0041] The shape of the periodic structure rs is not particularly limited. For example, as shown in Figure 2A, the periodic structure rs can be composed of a plurality of resistive element portions rsa (an example of a resistor) arranged to have periodicity in the plane of the resistive layer r. In the example in Figure 2A, the resistive element portion rsa is shown as a circular ring shape, but it is not limited to this, and may be in other shapes such as rectangular. In Figure 2A, W1 is the vertical width of the resistive element rsa, and W2 is the horizontal width of the resistive element rsa. Also in Figure 2A, ds1 is the vertical distance between adjacent pairs of resistive element rsa, and ds2 is the horizontal distance between adjacent pairs of resistive element rsa. The sizes of ds1 and ds2 may be the same or different. As the resistive layer r stretches, the width W2 of the resistive element portion rsa changes. Also, the resistive element portion rsa deforms to stretch laterally, and its width ds2 expands. In other words, the spacing of the resistive element portions rsa constituting the periodic structure in the stretched state shown in Figure 1B (an example of the second stretched state) becomes wider than the spacing of the resistive element portions rsa constituting the periodic structure in the stretched state shown in Figure 1A (an example of the first stretched state). Thus, the transmission characteristics of radio waves change as the shape of the resistive layer r deforms.

[0042] As shown in Figure 2B, the periodic structure rs can extend across the entire resistive layer r and be composed of a periodic mesh structure. When the resistive layer r is a mesh structure, each grid in the mesh structure corresponds to a resistive element (an example of a resistor). As the resistive layer r extends, the shape of each grid deforms. This changes the transmission characteristics of radio waves at different frequencies.

[0043] The periodicity of the periodic structure rs may exist in one direction (for example, the vertical or horizontal direction in the figure) or in two directions (for example, the vertical and horizontal directions in the figure) within the plane of the resistive layer r.

[0044] The resistance value (Ω / sq) of the resistive layer r is, specifically, for example, 0.01, 0.02, 0.03, 0.04, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1, 1.2, 1.7, 2.2, 2.7, 3.2, 3.7, 4.2, 4.7, 5.2, and may be within the range of any two of the values ​​exemplified here. For example, the resistance value (Ω / sq) of the resistive layer r is preferably 0.01 or more and 5.2 or less. More preferably, the resistance value (Ω / sq) of the resistive layer r is 2 or less. The thickness (μm) of the resistive layer r is specifically, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, and may also be within the range of any two of the values ​​exemplified here.

[0045] For the resistive layer r, for example, carbon microcoils, carbon nanotubes, or graphene can be used. Here, it is preferable that the resistive layer r, like the dielectric layers d1 and d3, be highly stretchable, so carbon nanotubes or graphene are preferred. Carbon nanotubes can be obtained by various methods, such as vapor phase growth methods including arc discharge, laser evaporation, and thermal decomposition. The carbon nanotubes used as the resistive layer r of the sheet member 10 may be single-layer or multi-layer. Graphene can be obtained by methods such as peel transfer, SiC pyrolysis, chemical vapor deposition, or carbon nanotube cutting. For the graphene used as the resistive layer r of the sheet member 10, flaky powdered graphene can be used, as it allows for easy acquisition of the desired aspect ratio and provides orientation in the sheet member 10. A water-soluble polyester resin can be used as the resin for dispersing the above-mentioned carbon material. The constituent material of the resistive layer r is not limited to these, and may, for example, be a conductive organic polymer film.

[0046] 1-2. Actuator 20 The actuator 20 is configured to extend and retract the sheet member 10 to the extended and retracted states shown in Figure 1A and Figure 1B. The actuator 20 can employ multiple forms as a tensioning mechanism, including a linear mechanism and a roller mechanism. One example of the embodiment shows a form using a linear mechanism. In this case, the actuator 20 has, for example, a connecting member 20a and a linear mechanism 20b.

[0047] The connecting member 20a is connected to the sheet member 10, allowing the sheet member 10 to be stretched. In one example, the connecting member 20a is provided penetrating the dielectric layers (dielectric layer d1 and dielectric layer d2), but is not limited to this, and may be connected, for example, to the upper surface of dielectric layer d1 and the lower surface of dielectric layer d2 via an engagement mechanism or adhesive. The position where the connecting member 20a is connected to the sheet member 10 is not particularly limited, but for example, each connecting member 20a is connected to the end (edge) of the sheet member 10.

[0048] The linear mechanism 20b is connected to the connecting member 20a, and the linear mechanism 20b is configured to be able to stretch the connecting member 20a in the expansion and contraction direction of the sheet member 10. The linear mechanism 20b is driven and controlled by a control unit (not shown). This control unit may also be included in the configuration of the transmission frequency changing mechanism 100. This control unit can determine the expansion and contraction state of the sheet member 10 (for example, the expansion and contraction state shown in Figure 1A or Figure 1B) based on position information (for example, the position information of the connecting member 20a). When the control unit determines that a desired expansion and contraction state has been reached, it can stop the linear mechanism 20b.

[0049] The actuator 20 may also be configured using a roller mechanism. In other words, the actuator 20 has a roller mechanism instead of the connecting member 20a and the linear mechanism 20b. The roller mechanism is configured to pull the sheet member 10 by wrapping around it, for example. The rotation of the rollers of the roller mechanism is driven and controlled by the control unit.

[0050] Furthermore, while the embodiment shows a configuration in which the sheet member 10 is pulled from both sides as an example, it is not limited to this. The tensioning mechanism on one side may be fixed, while the tensioning mechanism on the other side is driven.

[0051] Furthermore, although the embodiment describes the realization of two expansion / contraction states, as shown in Figure 1A and Figure 1B, it is not limited to this. The control unit described above may control the actuator 20, which is a tensioning mechanism, to realize three or more expansion / contraction states. Even when three or more expansion / contraction states are realized, the radio wave transmission characteristics in each expansion / contraction state are different.

[0052] In this embodiment, the expansion and contraction direction is set to one, but the invention is not limited to this. The transmission frequency changing mechanism 100 may include multiple sets of actuators 20 and pull the sheet member 10 from two or more directions to change the transmission characteristics of radio waves.

[0053] 2. Description of the operation and effects of the embodiment The transmission frequency changing mechanism 100 according to this embodiment includes a sheet member 10 configured to change the wavelength band through which radio waves are transmitted in each expanded / contracted state, and an actuator 20 that expands / contracts the sheet member 10, thereby changing the transmission wavelength band of radio waves. This makes it possible to transition, for example, between a state in which radio waves of a predetermined wavelength band are blocked and a state in which radio waves are transmitted. Furthermore, since the transmission wavelength band can be easily adjusted by the degree of expansion / contraction (the length to which the actuator 20 pulls the sheet member 10), it can be used not only as a radome but also as a variable filter in which the transmission frequency band can be tuned.

[0054] The inventors analyzed and confirmed the radio wave transmission characteristics of the transmission frequency changing mechanism 100 according to the embodiment. The graphs shown in Figures 3A to 4B show the results of the transmission characteristics of an object having the configuration of the transmission frequency changing mechanism 100 described in the embodiment. The vertical axis corresponds to the return loss (radio wave absorption), and the unit is decibels (dB). A smaller value on the vertical axis indicates that the signal is less likely to penetrate. The horizontal axis corresponds to the frequency of radio waves, and the unit is GHz.

[0055] The conditions for the analysis are described below. <Analysis conditions for the state without stretching (an example of the first stretched state)> The dielectric layers d1 and d2 have a thickness of 100 μm, a square shape in plan view with sides of 0.8 mm, a relative permittivity of 2.5, and a tanδ of 0.02. The layers placed between dielectric layer d1 and dielectric layer d2 are a resistive layer r and an adhesive layer. The thickness of the resistive layer r and the adhesive layer is 10 μm. The resistive layer r has a square shape with sides of 0.34 mm and a resistance of 0.2 Ω / sq. The adhesive layer has a square shape with sides of 0.8 mm, a relative permittivity of 2.6, and a tanδ of 0.07. <Analysis conditions for the stretched state (an example of the second stretched state)> The dielectric layers d1 and d2 have a thickness of 95 μm, and their planar shape is a rectangle with a long side of 1.072 mm and a short side of 0.76 mm. The relative permittivity is 2.5, and tanδ is 0.02. The thickness of the resistive layer r and the adhesive layer is 9.5 μm. The resistive layer r has a rectangular shape in plan view, with a long side of 0.456 mm and a short side of 0.323 mm, and a resistance of 0.2 Ω / sq. The adhesive layer has a rectangular shape in plan view, with a long side of 1.072 mm and a short side of 0.76 mm, a relative permittivity of 2.6, and a tanδ of 0.07.

[0056] In Figures 3A and 3B, TE mode radio waves are incident on the transmission frequency changing mechanism 100. Here, the TE mode (Transverse Electric mode) and the TM mode (Transverse Magnetic mode), which will be described later, are classified based on the directions of the electric and magnetic fields in the propagation of electromagnetic waves. In the TE mode, there is no electric field component along the propagation direction, and the electric field is perpendicular to the propagation direction. On the other hand, in the TM mode, there is no magnetic field component along the propagation direction, and the magnetic field is perpendicular to the propagation direction. In this analysis, the direction of the electric field in TE mode is aligned with the expansion and contraction direction of the sheet member 10. As shown in Figures 3A and 3B, it can be seen that the peak frequency at which radio waves are blocked is shifted from point P1 to point P2. Furthermore, at the peak frequency, the return loss is 9 dB or less, ensuring sufficient shielding of radio waves.

[0057] In Figures 4A and 4B, radio waves in TM mode are incident on the transmission frequency changing mechanism 100. In this case, the direction of the electric field in TM mode is perpendicular to the expansion and contraction direction of the sheet member 10. In this mode as well, as shown in Figures 4A and 4B, it can be seen that the peak frequency that blocks the radio waves is shifted from point P3 to point P4, and radio wave shielding is also ensured. Note that Figure 3A is the graph for the TE mode and Figure 4A is the graph for the TM mode. Both graphs represent the natural length state (no stretching, an example of the first stretching state), but in the natural length state, the graphs are the same regardless of the mode. In other words, although Figures 3A and 4A appear to have different shapes because the vertical axis scales are different, they are graphs with the same content.

[0058] Furthermore, the inventors analyzed the transmission characteristics while varying the resistance value of the resistive layer r, as shown in Figures 5A and 5B (unstretched state), Figures 6A and 6B (30% stretched state in TE mode), and Figures 7A and 7B (30% stretched state in TM mode). Based on these results, taking into account the bandwidth and loss characteristics, the inventors identified that a resistance value of 2 (Ω / sq) or less for the resistive layer r is particularly preferable.

[0059] Various embodiments are illustrated below. The embodiments shown below can be combined with each other. [Note 1] A transmission frequency changing mechanism capable of changing the frequency of radio waves transmitted, It comprises a seat member and an actuator, The sheet member is configured to be expandable and contractible from a first expanded / contracted state to a second expanded / contracted state, and the sheet member is configured such that the wavelength band through which the radio waves are transmitted in the first expanded / contracted state changes from the wavelength band through which the radio waves are transmitted in the second expanded / contracted state. The width of the sheet member in the expansion and contraction direction in the second expansion and contraction state is longer than the width of the sheet member in the expansion and contraction direction in the first expansion and contraction state. The actuator is configured to extend and retract the sheet member to a first extended state and a second extended state, and is a transmission frequency changing mechanism. [Note 2] The transmission frequency changing mechanism described in Appendix 1, The sheet member has a laminate, The laminate comprises a first dielectric layer, a resistive layer, and a second dielectric layer, and these layers are arranged in this order from the incident side of the radio waves, in a transmission frequency changing mechanism. [Note 3] The transmission frequency changing mechanism described in Appendix 2, The aforementioned resistive layer has a resistance value of 2 (Ω / sq) or less, and is a transmission frequency changing mechanism. [Note 4] A transmission frequency changing mechanism described in any one of the appendices 1 to 3, The resistive layer has a periodic structure, The periodic structure is formed to have periodicity within the plane of the resistive layer. A transmission frequency changing mechanism wherein the shape of the resistor constituting the periodic structure in the second expansion / contraction state is deformed from the shape of the resistor constituting the periodic structure in the first expansion / contraction state. [Note 5] A transmission frequency changing mechanism described in any one of the appendices 1 to 4, A transmission frequency changing mechanism wherein, in at least one of the first and second expansion / contraction states, the input impedance value of the sheet member matches the impedance value of air. [Note 6] A transmission frequency changing mechanism described in any one of the appendices 1 to 5, The peak frequency of the non-transmitting wavelength band of the radio waves in the sheet member in the first expanded / contracted state is defined as the first peak frequency. When the peak frequency of the non-transmitting wavelength band of the radio waves in the sheet member in the second stretched state is defined as the second peak frequency, A transmission frequency changing mechanism in which the first peak frequency and the second peak frequency are different. [Note 7] The transmission frequency changing mechanism described in Appendix 6, A transmission frequency changing mechanism in which the first peak frequency and the second peak frequency are within the frequency range of 50 GHz to 300 GHz. [Note 8] A transmission frequency changing mechanism as described in Appendix 6 or Appendix 7, A transmission frequency changing mechanism wherein the first peak frequency and the second peak frequency are separated by 5 GHz or more. [Note 9] A transmission frequency changing mechanism described in any one of the appendices 6 to 8, A transmission frequency changing mechanism wherein the reflection attenuation of the radio waves at the first peak frequency and the second peak frequency is 80% or more. [Note 10] A transmission frequency changing mechanism described in any one of the appendices 6 to 9, The first characteristic, which peaks at the first peak frequency in the first stretched state, has a first frequency range in which the reflection attenuation of the radio waves is 80% or more. The second characteristic, which peaks at the second peak frequency in the second stretched state, has a second frequency range in which the reflection attenuation of the radio waves is 80% or more. The first frequency range and the second frequency range have a width of 5 GHz or more, and are a transmission frequency changing mechanism. [Note 11] A transmission frequency changing mechanism described in any one of the appendices 6 to 10, A transmission frequency changing mechanism wherein the first peak frequency is lower than the second peak frequency. [Explanation of Symbols]

[0060] 10: Sheet material 10s: Laminate 20: Actuator 20a: Connecting member 20b: Linear mechanism 100: Transmission frequency changing mechanism d1: Dielectric layer d2: Dielectric layer d3: Dielectric layer r: resistance layer rs :periodic structure rsa: Resistor element

Claims

1. A transmission frequency changing mechanism capable of changing the frequency of radio waves transmitted, It comprises a seat member and an actuator, The sheet member is configured to be expandable and contractible from a first expanded / contracted state to a second expanded / contracted state, and the sheet member is configured such that the wavelength band through which the radio waves are transmitted in the first expanded / contracted state changes from the wavelength band through which the radio waves are transmitted in the second expanded / contracted state. The width of the sheet member in the expansion and contraction direction in the second expansion and contraction state is longer than the width of the sheet member in the expansion and contraction direction in the first expansion and contraction state. The actuator is configured to extend and retract the sheet member to a first extended state and a second extended state, and is a transmission frequency changing mechanism.

2. A transmission frequency changing mechanism according to claim 1, The sheet member has a laminate, The laminate comprises a first dielectric layer, a resistive layer, and a second dielectric layer, and these layers are arranged in this order from the incident side of the radio waves, in a transmission frequency changing mechanism.

3. A transmission frequency changing mechanism according to claim 2, The aforementioned resistive layer has a resistance value of 2 (Ω / sq) or less, and is a transmission frequency changing mechanism.

4. A transmission frequency changing mechanism according to claim 2, The resistive layer has a periodic structure, The periodic structure is formed to have periodicity within the plane of the resistive layer. A transmission frequency changing mechanism wherein the shape of the resistor constituting the periodic structure in the second expansion / contraction state is deformed from the shape of the resistor constituting the periodic structure in the first expansion / contraction state.

5. A transmission frequency changing mechanism according to any one of claims 1 to 4, A transmission frequency changing mechanism wherein, in at least one of the first and second expansion / contraction states, the input impedance value of the sheet member matches the impedance value of air.

6. A transmission frequency changing mechanism according to any one of claims 1 to 4, The peak frequency of the non-transmitting wavelength band of the radio waves in the sheet member in the first stretched state is defined as the first peak frequency. When the peak frequency of the non-transmitting wavelength band of the radio waves in the sheet member in the second stretched state is defined as the second peak frequency, A transmission frequency changing mechanism wherein the first peak frequency and the second peak frequency are different.

7. A transmission frequency changing mechanism according to claim 6, A transmission frequency changing mechanism wherein the first peak frequency and the second peak frequency are within the frequency range of 50 GHz to 300 GHz.

8. A transmission frequency changing mechanism according to claim 6, A transmission frequency changing mechanism wherein the first peak frequency and the second peak frequency are separated by 5 GHz or more.

9. A transmission frequency changing mechanism according to claim 6, A transmission frequency changing mechanism wherein the reflection attenuation of the radio waves at the first peak frequency and the second peak frequency is 80% or more.

10. A transmission frequency changing mechanism according to claim 6, The first characteristic, which peaks at the first peak frequency in the first stretched state, has a first frequency range in which the reflection attenuation of the radio waves is 80% or more. The second characteristic, which peaks at the second peak frequency in the second stretched state, has a second frequency range in which the reflection attenuation of the radio waves is 80% or more. A transmission frequency changing mechanism wherein the first frequency range and the second frequency range have a width of 5 GHz or more.

11. A transmission frequency changing mechanism according to claim 6, A transmission frequency changing mechanism wherein the first peak frequency is lower than the second peak frequency.

Images