Reflector

Abstract

The purpose of the present invention is to provide a reflector in which the beam diameter of a main lobe of a reflected wave in a target direction is increased. The reflector includes: a dielectric layer; the conductive layer is formed on the first surface of the dielectric layer and comprises a plurality of conductor patterns for reflecting incident waves; and a ground layer formed on a second surface of the dielectric layer opposite to the first surface, the plurality of conductor patterns being arranged along a predetermined direction, the plurality of conductor patterns being arranged along the predetermined direction, and the conductor patterns being arranged along the predetermined direction. The standard deviation sigma of the difference between the center-to-center distance between the reference conductor pattern and any conductor pattern and the ideal distance is 0.5 mm or more and 1.5 mm or less.

Description

Technical Field

[0001] This invention relates to a reflector, and more particularly to a reflector having a metasurface. Background Technology

[0002] When high-frequency radio waves such as microwaves, millimeter waves, and terahertz waves are used for wireless communication, high-speed and high-capacity communication is possible. On the other hand, high-frequency radio waves, such as those from 1 GHz to 10 THz, have the following drawbacks: strong line-of-sight propagation, and the inability to reach the target area due to obstacles between the transmitting and receiving antennas, thus preventing communication. To improve the communication environment and coverage area for high-frequency mobile communications, reflectors are used. Typical reflectors have a specular reflective surface with an incident angle equal to the reflection angle, thus limiting the reflection range. To extend the communication range, superreflectors with metasurfaces that reflect incident waves in the desired direction are being actively developed.

[0003] "Metasurface" refers to an artificial surface that controls the transmission and reflection characteristics of incident electromagnetic waves. By periodically arranging metallic patterns of approximately half a wavelength, the reflection characteristics are controlled, causing the incident wave to be reflected in the desired direction. One proposed reflection array involves forming array elements in segmented regions on a substrate, with the gaps between the multiple patches constituting the array elements varying according to each region (see, for example, Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Publication No. 5177708 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Metasurface reflector arrays utilize the resonance phenomenon. Therefore, when reflected at a specified frequency in a desired direction (hereinafter referred to as the "target direction"), the reflection distance to the target is inversely proportional to the beam diameter. Consequently, if the reflection distance increases, the beam diameter of the main lobe of the reflected wave in the target direction narrows. If the beam diameter of the main lobe narrows, the coverage area of ​​the radio wave within its arrival distance is limited, sometimes preventing communication.

[0009] In one aspect, the object of the present invention is to provide a reflector in which the beam diameter of the main lobe of the reflected wave in the target direction is increased.

[0010] Solution for solving the problem

[0011] In one embodiment, the reflector has: a dielectric layer; a conductive layer formed on a first surface of the dielectric layer, including a plurality of conductor patterns for reflecting incident waves; and a ground layer formed on a second surface of the dielectric layer opposite to the first surface, wherein a plurality of conductor patterns are arranged along a predetermined direction, and among the plurality of conductor patterns, the standard deviation σ of the difference between the center distance of a reference conductor pattern and an arbitrary conductor pattern along the predetermined direction and an ideal distance is 0.5 mm or more and 1.5 mm or less.

[0012] Invention Effects

[0013] Through the above configuration, a reflector with a large beam diameter of the main lobe of the reflected wave in the direction of the target is achieved. Attached Figure Description

[0014] Figure 1 This is a diagram showing the basic configuration of the reflector in the first embodiment.

[0015] Figure 2 This is a diagram illustrating an example of a design method for conductor patterns.

[0016] Figure 3A This is a diagram illustrating a design example of the reflector according to the first embodiment.

[0017] Figure 3B This is a diagram illustrating a design example of the reflector according to the first embodiment.

[0018] Figure 4 It means based on Figure 3A and Figure 3B The diagram shows the reflection characteristics of the designed reflector.

[0019] Figure 5 This is a graph showing the composition of the standard deviations of the embodiments and comparative examples.

[0020] Figure 6 It means based on Figure 5 The diagram shows the reflection characteristics of the designed reflector.

[0021] Figure 7 It means based on Figure 5 The diagram shows the reflection characteristics of the designed reflector.

[0022] Figure 8A This is a diagram showing the reflection characteristics of a low dielectric constant reflector.

[0023] Figure 8B This is a diagram showing the reflection characteristics of a low dielectric constant reflector.

[0024] Figure 8C This is a diagram showing the reflection characteristics of a low dielectric constant reflector.

[0025] Figure 9A This is a diagram showing the reflection characteristics of a high dielectric constant reflector.

[0026] Figure 9B This is a diagram showing the reflection characteristics of a high dielectric constant reflector.

[0027] Figure 9C This is a diagram showing the reflection characteristics of a high dielectric constant reflector.

[0028] Figure 10A This is a graph representing the reflection range of a low dielectric constant reflector relative to frequency.

[0029] Figure 10B This is a graph representing the reflection range of a high dielectric constant reflector relative to frequency.

[0030] Figure 11 This is a graph showing the relationship between the thickness of a dielectric layer with different dielectric constants and the reflection bandwidth.

[0031] Figure 12 This is a graph showing the relationship between the thickness of a dielectric layer with different dielectric constants and the reflection intensity.

[0032] Figure 13 This is a diagram illustrating the configuration and characteristics of the embodiments and comparative examples.

[0033] Figure 14 This is a schematic diagram of the reflector according to the second embodiment.

[0034] Figure 15 This is a graph showing the simulation results obtained by changing the thickness and dielectric constant of the protective layer.

[0035] Figure 16A This is a diagram illustrating an example of the use of a reflector in an implementation method.

[0036] Figure 16B This is a diagram illustrating a typical example of the use of a reflector. Detailed Implementation

[0037] Figure 1This is a basic structural diagram of the reflector 10 according to the first embodiment. The reflector 10 includes: a dielectric layer 11; a conductive layer 13 disposed on a first surface 111 of the dielectric layer 11; and a ground layer 12 disposed on a second surface 112 of the dielectric layer 11 opposite to the first surface 111. The conductive layer 13 includes an arrangement of a plurality of conductor patterns 131, and functions as a reflective surface of the reflector 10. This reflective surface is a metasurface that reflects incident waves at an angle (absolute value) different from the angle of incidence. Through the ground layer 12, a capacitor is formed between the ground layer 12 and each conductor pattern 131, and the magnitude of the phase delay can be controlled according to each conductor pattern 131. There are no particular limitations on the conductive layer 13 and the ground layer 12 as long as they are made of conductive materials, but copper foil is preferred, for example, from the perspective of conductivity, manufacturability, processability, and material cost.

[0038] The size and spacing of the conductor patterns 131 are set according to the required reflection characteristics. Each conductor pattern 131 has a size much smaller than the wavelength used, selectively reflecting radio waves in the target frequency band. The phase of the reflection is controlled by the conductor patterns 131, so that the reflected waves are superimposed to form a reflected beam BM in the desired direction.

[0039] Let the wavelength of the incident electromagnetic wave be λ, the spacing between the conductor patterns 131 (i.e., the distance between the centers of adjacent conductor patterns 131) be d, the phases of the electromagnetic waves reflected by the two adjacent conductor patterns 131 be δ1 and δ2 respectively, and the reflection angle be θ. The phase difference δ1-δ2 is expressed by formula (1).

[0040] δ1-δ2=(2π / λ)d·sinθ+2nπ (1)

[0041] Here, n is an integer.

[0042] To reflect the radio wave in the desired direction using reflector 10, δ1, δ2, and d only need to be designed in a way that yields the required reflection angle θ. The reflection angle θ is set as the desired angle between the normal direction (0°) and the horizontal direction (90°) of the reflecting surface of reflector 10, excluding 0° and 90°. The values ​​of δ1 and δ2, representing the reflected phase, can be controlled and varied by design parameters such as the wavelength λ of the incident radio wave, the dimensions (length × width) and spacing of the conductor pattern 131, the thickness of reflector 10, and the relative permittivity. For example, when designing the conductor pattern 131 to achieve the desired phase difference, the length L can be... Figure 2 The length / phase characteristic curve shown is used to design conductor pattern 131. Figure 2The length / phase characteristics were obtained as follows: With all design parameters except the length L (mm) fixed, the reflection pattern of the electromagnetic wave was measured while the length L of the conductor pattern was varied. The reflection pattern was then analyzed using three-dimensional electromagnetic field simulation software. The length L is the length of the conductor pattern 131 corresponding to the vibration direction of the electromagnetic wave, as shown below. Figure 3A As shown, when conductor patterns 131a to 131g are intersecting patterns, the longitudinal and transverse lengths of each conductor pattern are equal. As a design parameter other than length, for example, the relative permittivity ε of dielectric layer 11 is fixed at ε = 1.88.

[0043] (Distance between centers)

[0044] In the conductive layer 13, multiple conductor patterns 131 of different sizes are arranged separately at a predetermined distance. For example... Figure 3A As shown, in the reflector 10 of the first embodiment, the conductor patterns 131 are arranged in a row on a straight line l. The center point of each conductor pattern 131 is located on an arbitrary straight line. It should be noted that the semiconductor patterns 131 may not be arranged in a straight line, but may be arranged in a zigzag pattern or other arrangement patterns in the arrangement direction.

[0045] In this specification, "center point of conductor pattern" refers to the center point of the circle inscribed in the outline of each conductor pattern when viewed from above. Furthermore, the distance between the center points of the reference conductor pattern and any other conductor pattern is called the "inter-center distance." Additionally, when multiple conductor patterns are arranged, for ease of explanation, sometimes an arbitrary integer m greater than 1 is used to denote the inter-center distance from the center point of the reference conductor pattern to the center point of the m-th conductor pattern (counting from the reference conductor pattern) as "dm" or "dm'". For example, [The text abruptly ends here, likely due to an incomplete translation or missing information.] Figure 3A The first conductor pattern 131a from the left in the middle is set as the reference conductor pattern. For the first conductor pattern in the arrangement direction from the reference conductor pattern (in... Figure 3A The center-to-center distance of the second conductor pattern (131b) from the left is denoted as d1, and the actual distance is denoted as d1'. The seventh conductor pattern (in... Figure 3A The ideal distance of the eighth pattern from the left (131h) is denoted as d7, and the actual distance is denoted as d7'.

[0046] (Ideal distance)

[0047] In the design of arranging multiple conductor patterns 131 as conductor layer 13, when incident waves of the same phase are incident on a reference conductor pattern and the m-th conductor pattern counting from the reference conductor pattern, the center-to-center distance between the reference conductor pattern with the strongest reflected wave intensity and the m-th conductor pattern is defined as the "ideal distance" of the m-th target conductor pattern. In this specification, the ideal distance is denoted as dm. By arranging the conductor patterns 131 of the conductor layer 13 with the ideal distance dm, a reflector with a large flight distance of the reflected wave is obtained. From the viewpoint of robustness when designing the reflection characteristics of the reflector, the ideal distance dm is preferably 0.5λ or more and 0.7λ or less relative to the wavelength λ of the incident wave.

[0048] (Actual distance)

[0049] For an ideal distance dm, the center-to-center distance between the first conductor pattern and the m-th conductor pattern formed on the first surface of the dielectric layer is defined as the "actual distance" of the m-th conductor pattern. In this specification, the actual distance is denoted as dm'.

[0050] (Enlarging the diameter of the beam)

[0051] For the reflector of the first embodiment of the present invention, the absolute value of the difference between the actual distance dm' and the ideal distance dm is set as |dm'-dm|.

[0052] When m is set to an integer greater than or equal to 1

[0053] The standard deviation σ of the group consisting of |dm'-dm| of each conductor pattern other than the reference conductor pattern is 0.5 mm or more and 1.5 mm or less. The inventors of this invention, through in-depth research, discovered that by designing the reflector in this way, when an electromagnetic wave is incident on the reflector at any phase, the beam diameter of the main lobe of the reflected wave is enlarged. It should be noted that, in this specification, "beam diameter" is defined as: in the intensity distribution of the main lobe of the reflected wave, when the horizontal axis is used as the reflection angle and the vertical axis as the reflected wave intensity, the region where the difference Δ between the intensity and the peak intensity is 10 dB is the reflection angle region.

[0054] In the second embodiment of the present invention, the relative permittivity of the dielectric layer 11 in the reflector is 2.0 or less, except for the configuration of the first embodiment. By setting the relative permittivity to 2.0 or less, the frequency band of the electromagnetic waves reflected in a predetermined direction can be expanded. Details regarding the expansion of the reflected frequency band will be referred to... Figure 5This will be explained later. For dielectric materials with a relative permittivity of 2.0 or less, fluorinated resins such as polytetrafluoroethylene (PTFE), composites of fluorinated resins and inorganic porous aggregates, and other transparent porous resins can be used. For resins bonded to inorganic porous aggregates, polytetrafluoroethylene (PTFE) and polystyrene are used.

[0055] Inorganic porous aggregates can be manufactured, for example, by the method described in Japanese Patent Application Publication No. 2017-171898. By adjusting the material and aggregation density of the porous inorganic microparticles, the porosity of the aggregate can be controlled to be above 50%. By adjusting the porosity, the relative permittivity can be controlled, and a permittivity of 2.0 or below can be achieved.

[0056] Figure 3A and Figure 3B This illustrates a design example of the reflector 10 according to the first embodiment. Figure 3A This indicates the arrangement of conductor patterns 131a to 131h constituting the conductive layer 13. Figure 3B The dimensions of each conductor pattern are shown. Conductor patterns 131a to 131h are intersecting patterns with equal lengths in both the longitudinal and transverse directions. The dimensions of each conductor pattern 131 are represented by longitudinal or transverse lengths L1 to L8. The incident wave has a wavelength λ = 10.8 mm in the 28 GHz band, and the ideal distance dm between the centers of conductor patterns 131a to 131h is 5.35 mm.

[0057] The target reflection angle is -42°, achieved by arranging conductor patterns 131a to 131h. In this case, the reflection angle is the angle of reflection when the electromagnetic wave is incident perpendicularly to the reflector 10, i.e., the reflection angle relative to the normal. When the phase difference "δ1 - δ2" is calculated as θ = -42° according to the above formula (1), the phase difference is 120°. The dimensions of conductor patterns 131a to 131h, i.e., the lengths L1 to L8, are determined in a manner that allows this phase difference to be obtained.

[0058] The shape of the conductor pattern 131 is not limited to a cross pattern; it can also be circular, elliptical, polygonal, or other shapes of different sizes arranged at a predetermined period. When targeting the 28 GHz band, the conductor pattern 131 preferably has a length of 2.0 mm to 5.0 mm, but the size of the conductor pattern 131 is appropriately designed according to the frequency band. Radio waves at frequencies determined by the size and period of the conductor pattern 131 are selectively reflected. Generally, the frequency band selected by resonance is narrow, but by setting the relative permittivity of the dielectric layer 11 to 2.0 or less, the selected frequency band can be extended to a bandwidth of 4 GHz or more, more preferably 6 GHz or more. The selected bandwidth may vary depending on the thickness of the dielectric layer 11 of the reflector 10, thus achieving a broadband reflector with a bandwidth exceeding 6.5 GHz / mm per unit thickness (1 mm) of the reflector 10.

[0059] Figure 4 It shows in Figure 3A and Figure 3B In the conductor pattern design, the reflection characteristics of a reference-based reflector 10 are designed such that the standard deviation σ of the absolute value of the difference between the actual distance dm' and the ideal distance dm, |dm'-dm|, is zero. The horizontal axis represents the reflection angle, and the vertical axis represents the reflection intensity (dB). A main peak was observed in the -42° direction, confirming that the reflector 10 can roughly control the reflection direction of the radio wave according to the design. Furthermore, the beam diameter of the main lobe at -42°, i.e., the reflection angle region that decreases by 10dB from the peak, is 36.4°.

[0060] <Beam Diameter Enlargement Based on Standard Deviation σ>

[0061] Regarding the standard deviation σ of the absolute value |dm'-dm| of the difference between the actual distance dm' and the ideal distance dm, for Examples 1-3 and Comparative Examples 1-6, σ is expressed as 0, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, 1.5, 2.0, 2.5, as follows: Figure 5 The design was implemented with actual distances varying from d1 to d7. A dielectric layer 11 with a relative permittivity ε of 1.88 was used to calculate the reflection spectrum of an incident plane wave at 28 GHz. The reflection intensity was analyzed using Dassault Systèmes' CST Studio Suite, a general-purpose 3D electromagnetic field simulation software, to determine the reflection intensity at each angle. The angle at which the peak reflection intensity occurred was then defined as the "reflection peak angle."

[0062] The reflection peak angle and beam diameter were evaluated as described below.

[0063] 〇: The beam diameter is thicker than the reference, and the difference in the peak reflection angle relative to the reference is within ±2°.

[0064] △: The beam diameter is thicker than the reference, but the reflection peak angle is offset.

[0065] ×: The beam diameter is smaller than the reference.

[0066] Based on Figure 5 The simulation results of the reflection characteristics of the designed reflector are shown in Figure 6 and Figure 7 . Figure 6 The vertical axis represents the reflection intensity (unit: dB), and the horizontal axis represents the reflection angle (unit: °).

[0067] like Figure 6 and Figure 7As shown, Examples 1-3 and Comparative Examples 5 and 6, with a standard deviation σ of 0.5 mm or more, exhibit larger beam diameters compared to the reference. On the other hand, Comparative Examples 5 and 6, with a standard deviation σ of 2.0 or more, show a shift in the peak reflection angle of the reflection peak angle of Comparative Examples 5 and 6 exceeding 3° relative to the design value, thus failing to achieve the desired reflection characteristics. Furthermore, Comparative Examples 1-4, with a standard deviation σ less than 0.5 mm, show smaller beam diameters compared to the reference. Therefore, it is evident that when the standard deviation σ is 0.5 mm or more and 1.5 mm or less, it is possible to increase the beam diameter while maintaining the desired reflection angle.

[0068] (A more preferred configuration)

[0069] <Expansion of the reflection frequency band achieved by reducing the dielectric constant>

[0070] By using a material with a relatively low permittivity in the dielectric layer 11 of the reflector 10, the frequency band of the reflection can be expanded. The frequency band of the reflection refers to the frequency range in which the main lobe of the reflected wave in the target direction of the incident wave attenuates by 3 dB from the peak intensity. Hereinafter, the target value of the reflection peak angle is designed to be "35°", and analysis and evaluation based on simulation are performed.

[0071] Figures 8A to 8C The reflection characteristics of a low-dielectric-constant reflector for incident waves of different frequencies are shown. The low-dielectric-constant reflector is the reflector of the embodiment, specifically a reflector 10 using a dielectric layer 11 with a relative permittivity of 2.0 or less. In this example, a dielectric layer with a relative permittivity ε of 1.88 is used. For comparison, Figures 9A to 9C The diagram illustrates the reflection characteristics of a high-dielectric-constant reflector for incident waves of different frequencies. A high-dielectric-constant reflector is a reflector that uses a dielectric layer with a relative permittivity exceeding 2.0.

[0072] exist Figures 8A to 8C In this study, a dielectric layer 11 with a relative permittivity ε of 1.88 was used to calculate the reflection spectra at 26 GHz, 28 GHz, and 31 GHz. The reflection intensity on the vertical axis is represented by the radar cross section (RCS), an indicator of reflectivity. Plane waves incident from the normal direction of the reflector at each frequency band of 26 GHz, 28 GHz, and 31 GHz were analyzed for the RCS at each angle using Dassault Systèmes' CST Studio Suite, a general-purpose three-dimensional electromagnetic field simulation software.

[0073] At ε = 1.88, peak values ​​of the reflection spectrum appear at a 35° angle at 26 GHz, 28 GHz, and 31 GHz. Regardless of the frequency band, the peak value is within the range of -25 dB ± 2.5 dB, and a stable peak intensity can be obtained at a target reflection angle of 35° within a frequency band of at least 5 GHz.

[0074] In particular, at 28 GHz and 31 GHz, the main lobe at a reflection angle of 35° is clearly distinguishable from the other side lobes, indicating that the incident wave is reflected with good control towards the target at a 35° angle. At 26 GHz, in addition to the peak at 35°, other peaks appear at 0° and -65°. The peak at 0° is a reflection in the same direction as the incident wave, and therefore corresponds to a loss. The peak at -65° is a reflection in the opposite direction to the target at 35°; depending on the environment in which the reflector is used, this can sometimes be considered a loss, and sometimes an advantage in allowing the radio wave to reach both directions at once.

[0075] exist Figures 9A to 9C In the comparative example, the relative permittivity ε was changed to 3.62, while other conditions such as the conductor pattern were kept the same as before. Figures 8A to 8C The reflector is the same. Materials with a relative permittivity of 3.62 include polyphenylene ether (PPE) and acrylic resin. At a relative permittivity of 3.62, reflection peaks appear at 35° of the target at 28 GHz and 31 GHz, but the spectral shape of the main lobe deteriorates at 31 GHz. At 26 GHz, no reflection is obtained at 35° of the target.

[0076] Figures 9A to 9C The structure directly illustrates the fact that in metasurfaces utilizing resonance, reflection properties deteriorate as the frequency changes. By using... Figures 8A to 8C The low-dielectric-constant reflector of the illustrated embodiment can significantly improve frequency characteristics. Based on Figures 8A to 8C as well as Figures 9A to 9C It can be seen that by using a certain degree to reduce the dielectric constant of the dielectric layer 11 used in the reflector 10, the frequency band of the reflection can be expanded.

[0077] Figure 10A The reflection range of the low dielectric constant reflector is shown. Figure 10B The reflection range of a high dielectric constant reflector is shown. Figure 10A and Figure 10B In the diagram, the horizontal axis represents the reflection angle, and the vertical axis represents the frequency of the incident wave. The reflector model used is based on a dielectric layer with a surface textured with... Figure 3A Models with the same conductor pattern. Figure 10A The relative permittivity ε of the low-permeability reflector was set to 1.88. Figure 10BThe relative permittivity ε of the high permittivity reflector is set to 3.62.

[0078] exist Figure 10A In the 35° direction from the target, high reflection intensity (exceeding -30dB and below -20dB) was obtained from 24GHz to 33GHz. This reflection intensity is distributed within ±10° around 35°, and particularly, within the frequency band above 10GHz, a reflection intensity exceeding -30dB and below -20dB is obtained in the range above 23° and below 35°. This wide range of reflection frequency characteristics enables high tolerance to environmental changes.

[0079] exist Figure 10B In this study, with a relative permittivity of 3.62, high reflection intensity (exceeding -30dB and below -20dB) was obtained from 21GHz to 28.5GHz in a 35° direction from the target. However, considering the frequency bands actually used in various countries, Figure 10B The practical frequency band of the reflector is in the range of 24 GHz to 28.5 GHz. Considering the possibility of frequency bands and peak shifts used in different countries, a reflector with a frequency band of more than 6 GHz in the frequency range above 24 GHz and below 60 GHz is desired.

[0080] from Figure 10A and Figure 10B It can be confirmed that the lower the dielectric constant of the dielectric layer 11 of the reflector, the wider the reflection range (angle range) relative to the frequency, and the wider the frequency band of the practical reflection.

[0081] <Thickness of the dielectric layer>

[0082] Reference Figure 11 and Figure 12 The thickness of dielectric layer 11 was studied. Figure 11 The relationship between the thickness of dielectric layers with different dielectric constants and the frequency band of reflection is shown. Figure 12 The relationship between the thickness of dielectric layers with different dielectric constants and the reflection intensity is shown. Figure 11 In this process, the thickness of the dielectric layer 11 is changed to 0.30 mm, 0.50 mm, and 0.75 mm. The conductor pattern 131 formed on the first surface 111 of the dielectric layer 11 and... Figure 3A The conductors have the same pattern, but the relative permittivity ε of the dielectric layer 11 is different. A 28 GHz plane wave is incident from the normal direction of the reflector, and the frequency band of the reflected wave is analyzed. As mentioned above, the bandwidth of the reflected wave is the bandwidth of the main lobe of the reflected wave that is attenuated by 3 dB from the peak value.

[0083] With the same thickness of dielectric layer 11, a lower relative permittivity ε results in a wider frequency band for reflection. Conversely, to achieve the same frequency band for reflection, a material with a low permittivity allows for a thinner reflector. Figure 11 In the example, when the thickness of the dielectric layer 11 is 0.75 mm, a frequency band of reflection exceeding 6.5 GHz can be achieved in a reflector with ε of 1.88, but in a reflector with ε of 3.62, only a frequency band of reflection of 4.5 GHz can be covered.

[0084] As mentioned above, considering the frequency bands used in different countries and peak offsets, ideally, the reflected frequency band should exceed 6 GHz in the frequency band above 24 GHz and below 30 GHz. When considering... Figure 11 When interpolating the data points, it may be possible to achieve a 6GHz reflection frequency band by increasing the thickness of the dielectric layer 11 with an ε of 3.62 to approximately 1.2 mm. However, in this case, the reflector becomes thicker, its flexibility decreases, and its application range is limited.

[0085] In contrast, with an ε of 1.88, a dielectric layer 11 with a thickness of 0.75 mm can achieve a reflection frequency band of 6.5 GHz, enabling the creation of a flexible, sheet-like reflector. Sheet-like reflectors are easy to handle and can be applied to desired locations like wallpaper. The ability to achieve broadband coverage through a thin and flexible dielectric layer 11 is a significant advantage.

[0086] exist Figure 12 In this study, the peak intensity of the reflected wave was calculated by changing the thickness of the dielectric layer 11 to 0.25 mm, 0.30 mm, 0.50 mm, and 0.80 mm. When the relative permittivity ε is 1.88, a peak intensity exceeding -24 dB can be obtained by setting the thickness of the dielectric layer 11 to 0.30 mm or more. When ε is 3.62, the same level of peak intensity cannot be obtained unless the thickness of the dielectric layer 11 is set to 0.5 mm.

[0087] according to Figure 12 As a result, from the viewpoint of thinning and lightening the device, the low dielectric constant reflector of the implementation method is also advantageous.

[0088] Figure 13 The configuration and characteristics of the embodiments and comparative examples are shown. The configuration parameters include the type, thickness, relative permittivity, and porosity of the substrate material constituting the dielectric layer 11. Various changes were made to the values ​​of these parameters. As characteristics of the reflector, the frequency band of reflection and the frequency band per unit thickness are shown. Throughout the embodiments and comparative examples, the conductor pattern 131 is... Figure 3A The conductor patterns 131a to 131h are modified to change the type and parameters of the dielectric layer 11.

[0089] The simulation was conducted under the following conditions, and the frequency bands of the reflection of the embodiments and comparative examples were determined based on the far-field radiation field, intensity, and angle of the reflection spectrum obtained for the incident wave.

[0090] Wavelength of the incident wave: 10.7 mm (frequency 28 GHz)

[0091] The frequency variation range of the incident wave is from 20 GHz to 35 GHz.

[0092] Angle of incidence of the incident wave relative to the normal direction of the reflector: 0 degrees

[0093] The first desired reflection angle θ of the reflection spectrum relative to the normal direction of the reflector is 35 degrees.

[0094] Number of conductor patterns: 8 (in a straight line)

[0095] Conductor pattern spacing: 5.35mm

[0096] Standard deviation σ: 0.5 mm (designed with the same spacing as in Example 1).

[0097] <Example 4>

[0098] In Example 4, a fluorinated porous substrate was used as the matrix material for the dielectric layer 11. The fluorinated porous substrate is a combination of a fluorinated resin and an inorganic porous aggregate. Polytetrafluoroethylene (PTFE) was used as the fluorinated resin. The dielectric matrix material had a thickness of 0.75 mm, a porosity of 33.2%, and a relative permittivity of 1.88. The reflector obtained in Example 1 had a frequency band of 6.6 GHz, and a frequency band of 8.8 GHz / mm per unit thickness (1 mm).

[0099] <Example 5>

[0100] In Example 5, a fluorine porous substrate was used as the matrix material for the dielectric layer 11. This dielectric matrix material had a thickness of 0.75 mm, a porosity of 67.7%, and a relative permittivity of 1.50. The dielectric layer 11 was designed with different porosities and relative permittivityes by varying the aggregation density of the porous inorganic particles used in the fluorine porous substrate. The reflector obtained in Example 5 had a reflection frequency band of 7.1 GHz, and a frequency band of 9.5 GHz / mm per unit thickness (1 mm).

[0101] <Example 6>

[0102] In Example 6, a fluorine porous substrate was used as the matrix material for the dielectric layer 11. This dielectric matrix material had a thickness of 0.50 mm, a porosity of 33.0%, and a relative permittivity of 1.88. The dielectric layer 11 was designed with different porosities and relative permittivity by varying the aggregation density of the porous inorganic particles used in the fluorine porous substrate. Furthermore, the dielectric layer 11 was made thinner than the dielectric layers 11 in Examples 4 and 5. The reflector obtained in Example 6 had a reflection frequency band of 4.55 GHz, and a frequency band of 9.1 GHz / mm per unit thickness (1 mm).

[0103] <Example 7>

[0104] In Example 7, a fluorine porous substrate was used as the substrate material for the dielectric layer 11. This dielectric substrate material had a thickness of 1.00 mm, a porosity of 33.0%, and a relative permittivity of 1.88. The thickness of the dielectric layer 11 was made thicker than that of the dielectric layers 11 in Examples 4 and 5. The reflector obtained in Example 7 had a reflection frequency band of 6.5 GHz, and a frequency band of 6.5 GHz / mm per unit thickness (1 mm).

[0105] <Example 8>

[0106] In Example 8, a fluorine porous substrate was used as the matrix material for the dielectric layer 11. This dielectric matrix material had a thickness of 0.75 mm, a porosity of 22.5%, and a relative permittivity of 2.00. Different porosities and relative permittivity were designed by controlling the aggregation density of the porous inorganic particles used in the fluorine porous substrate. The reflector obtained in Example 8 had a reflection frequency band of 5.5 GHz, and a frequency band of 7.3 GHz / mm per unit thickness (1 mm).

[0107] <Example 9>

[0108] In Example 9, a fluorine porous substrate was used as the substrate material for the dielectric layer 11. This dielectric substrate material had a thickness of 0.3 mm, a porosity of 33.0%, and a relative permittivity of 1.88. The thickness of the dielectric layer 11 was thinner than that of the dielectric layer 11 in Example 8. The reflector obtained in Example 9 had a reflection frequency band of 4.1 GHz, and a frequency band of 13.7 GHz per unit thickness (1 mm).

[0109] <Comparative Example 7>

[0110] In Comparative Example 7, PPE was used as the substrate material for the dielectric layer 11. The PPE substrate material had a thickness of 0.75 mm, a porosity of 0.0%, and a relative permittivity of 3.62. The reflector obtained in Comparative Example 7 had a reflection frequency band of 4.5 GHz, and a frequency band of 6.0 GHz / mm per unit thickness (1 mm). Compared with Examples 4-5 and Example 8, a substrate material of the same thickness was used, but the relative permittivity was higher, thus narrowing the reflection frequency band.

[0111] <Comparative Example 8>

[0112] In Comparative Example 8, a glass epoxy matrix material was used as the substrate material for the dielectric layer 11. This dielectric substrate material had a thickness of 0.75 mm, a porosity of 0.0%, and a relative permittivity of 5.00. This relative permittivity was higher than that of Comparative Example 7. The reflector obtained in Comparative Example 8 had a reflection frequency band of 3.7 GHz, and a frequency band of 4.9 GHz / mm per unit thickness (1 mm).

[0113] <Comparative Example 9>

[0114] In Comparative Example 9, PPE was used as the substrate material for the dielectric layer 11. This dielectric substrate material had a thickness of 0.50 mm, a porosity of 0.0%, and a relative permittivity of 3.62. The reflector obtained in Comparative Example 9 had a reflection frequency band of 3.0 GHz and a frequency band of 6.0 GHz per unit thickness (1 mm). Although the same PPE substrate material as in Comparative Example 7 was used, the thickness of the substrate material was reduced, thus further narrowing the reflection frequency band.

[0115] from Figure 13The results show that when the relative permittivity of the dielectric layer 11 is 2.0 or less, a broadband reflection characteristic of more than 6.5 GHz, preferably more than 7.0 GHz, and more preferably more than 8.0 GHz per unit thickness of the reflector can be obtained. When the thickness of the dielectric layer is thin and the relative permittivity is 1.88 or less, a frequency band of more than 8.8 GHz per unit thickness of the reflector can be achieved. In Examples 8 and 9, by using a material with a low relative permittivity for the fluorinated resin combined with the inorganic porous aggregate, a porosity of about 20% and a relative permittivity of 2.0 or less can be achieved for the dielectric layer 11. The thickness of the dielectric layer 11 can be appropriately designed according to the application. When the reflector 10 is used in a flexible manner, the thickness of the dielectric layer 11 can be set to 0.3 mm or more and 1.0 mm or less. By setting the thickness of the dielectric layer 11 to 0.3 mm or more, a reflector 10 with high robustness can be obtained. Furthermore, if the thickness of the dielectric layer 11 is less than 1.0 mm, it is beneficial for lightweight design in large reflectors with a side length of approximately 1 m, resulting in excellent workability and construction costs. It should be noted that when mentioning thicknesses of 0.3 mm, 1.0 mm, etc., it is assumed to include permissible manufacturing tolerances.

[0116] Figure 14 This is a schematic diagram of the reflector 20 according to the second embodiment. The main part of the reflector 20 is the same as that of the reflector 10 in the first embodiment, using a dielectric layer 21 with a relative permittivity of 2.0 or less. A conductive layer 23 including a predetermined conductor pattern 231 is formed on the first surface 211 of the dielectric layer 21, and a ground layer 22 is provided on the second surface 212. The conductor pattern 231 is designed such that the reflection direction of the main lobe obtained for incident waves in the 28 GHz band is tilted at a predetermined angle from the normal direction. As an example, for example... Figure 3A The pattern shown is illustrated below. The target value for the peak reflection angle was then changed to "-43°", and a simulation-based analysis and evaluation were performed.

[0117] A protective layer 24 is provided to cover the conductive layer 23. An adhesive layer 26 is provided on the grounding layer 22 side. The reflector 20 can be attached to a desired location such as a wall or ceiling via the adhesive layer 26. The protective layer 24 is transparent to incident waves in the 24GHz to 30GHz range. Transparency to incident waves means having a transmittance of 60% or more, preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more. The protective layer 24 may also be transparent to visible light. By providing the protective layer 24, the reflector 20 can be attached to outdoor billboards or building walls. Alternatively, the board with the reflector 20 attached can be suspended in a desired location.

[0118] The protective layer 24 protects the conductor pattern 231 of the reflector 20 from deterioration and damage caused by external factors, resulting in excellent durability. The conductor pattern 231 of the reflector 20 is susceptible to oxidation and deterioration over time due to contact with oxygen and moisture in the atmosphere, especially in outdoor applications. From a weather resistance perspective, forming the protective layer 24 is preferable. Even indoors, in environments prone to condensation, forming the protective layer 24 is equally preferable. The protective layer 24 is preferably 0.1 mm or more and 1.0 mm or less in thickness, and has a relative permittivity of 2.0 or less. By constructing the protective layer 24 in this way, a reflector 20 that balances high durability and high transparency for incident waves in the 24 GHz to 30 GHz range can be obtained.

[0119] Use the adhesive layer 26 as an example. Figure 14 The model of its composition, such as Figure 15 As shown, for Examples 10-13 and Comparative Examples 10-17 with different protective layer thickness (mm) and relative permittivity Dk, simulations were performed under the following conditions, and the reflection angle deviation (%) and reflection intensity loss (%) of the Examples and Comparative Examples were determined based on the far-field radiation field, intensity, and angle of the reflection spectrum obtained for the incident wave.

[0120] • Wavelength of incident wave: 10.7 mm (frequency 28 GHz)

[0121] • Frequency variation region of incident wave: 20GHz–35GHz

[0122] • Angle of incidence of the incident wave relative to the normal direction of the reflector: 0 degrees

[0123] • The first desired reflection angle θ of the reflection spectrum relative to the normal direction of the reflector: -43 degrees

[0124] • Number of conductor patterns: 5 (in a straight line)

[0125] • Spacing of conductor patterns: 5.35mm

[0126] • Relative permittivity of protective layer 24: 1.0 (reference), 1.5, 2.0, 3.0, 5.0

[0127] • Thickness of protective layer 24: 0.0mm (reference), 0.2mm, 0.5mm, 1.0mm

[0128] Using five cross patterns of different sizes as the shape of the conductor pattern, the thickness and relative permittivity of the protective layer 24 covering the conductor pattern are varied, and the reflection angle and reflection intensity are calculated.

[0129] Figure 15 The simulation results are shown. Figure 15The leftmost column, "Reference," shows a baseline configuration without the protective layer 24. In the baseline configuration, an air layer covers the conductor pattern, therefore the thickness of the protective layer 24 is set to 0.0 mm, and the relative permittivity is set to 1.0. The unit of reflection intensity of the baseline configuration is (dB). "Reflection angle deviation" represents the rate of change (%) of the reflection angle relative to the baseline configuration, and "Reflection intensity loss" represents the percentage decrease (%) of the reflection intensity relative to the baseline configuration. For the peak angle and peak intensity of the main lobe obtained for the incident wave, the baseline configuration (reference) is compared with Examples 10 to 13 and Comparative Examples 10 to 17, and the reflection angle deviation (unit: %) and reflection intensity loss (unit: %) are calculated. The reflection angle deviation and reflection intensity loss are evaluated as follows.

[0130] • Reflection angle deviation is less than 10%: A

[0131] • Reflection angle deviation exceeds 10%: B

[0132] • Reflection intensity loss is less than 5%: S

[0133] • Reflection intensity loss is less than 10%: A

[0134] • Reflection intensity loss exceeds 10%: B

[0135] Overall evaluation

[0136] Pass: Both the reflection angle deviation and reflection intensity loss are rated "A".

[0137] Unacceptable: Either the evaluation of reflection angle deviation or reflection intensity loss is rated "B".

[0138] like Figure 15 As shown, Examples 10 to 13 are satisfactory. Furthermore, Examples 10 to 12 exhibit low reflection intensity loss, resulting in even better results. According to... Figure 15 When the relative permittivity Dk is high, the reflection angle deviation and reflection intensity loss are large. Ideally, the relative permittivity Dk should be below 2.0. When the relative permittivity Dk is below 1.5, the reflection intensity loss is below 5%, which is more preferable. Figure 15 The rating is "S" (meaning it is rated as "S"). When the thickness of the protective layer 24 is too thick, the reflection angle deviation and reflection intensity loss are large. Ideally, the thickness of the protective layer 24 should be above 0.1 mm and below 1.0 mm.

[0139] Figure 16A An example of the use of the reflector 20 of the embodiment is shown. Figure 16B The comparison shows examples of the use of a typical reflector. Figure 16AThe usage of the reflector 10 or reflector 20 according to the embodiment is shown. The thin and flexible reflector 10 or reflector 20 can be installed along pathways, channels, corridors, etc. that are bent into an L shape.

[0140] The reflector of this embodiment has a metasurface comprising a periodically arranged plurality of conductor patterns 131, and reflects incident waves in directions other than specular reflection. For example... Figure 16A In this way, when an electromagnetic wave is incident perpendicularly onto a reflector 10 or reflector 20 located on a wall at a corner, the incident electromagnetic wave is reflected at an angle other than the vertical and horizontal directions of the reflector. Thus, electromagnetic waves can be transmitted to smartphones, electronic devices, lighting equipment, etc., located in area A.

[0141] like Figure 16B Therefore, in a typical reflector RFL with a specular reflective surface, a perpendicularly incident radio wave would be reflected in the direction of incidence. Thus, the reflector RFL must be positioned at an angle relative to the incident radio wave. For example... Figure 16B In that case, when placed in a corner, space cannot be used effectively. In contrast, the reflector 10 or reflector 20 of the embodiment can reduce the blind spot of radio waves in a way that does not occupy space or damage the appearance.

[0142] As described above, the reflector of this embodiment, by using a dielectric layer with a low relative permittivity, can broaden the frequency band of reflection and improve environmental resistance. Furthermore, while maintaining the same reflection frequency characteristics, the reflector thickness can be reduced, expanding its application range. When the reflector is formed in a wallpaper-like shape, a protective film can be used to protect the surface of the adhesive layer 26; the protective film can be peeled off during use to adhere it to the desired location. The reflector of this embodiment can also be used in combination with small cells and repeaters. In this case, the dead zone can be further reduced without increasing the number of small cells, repeaters, or other devices and without occupying space for the reflector installation.

[0143] The above disclosure can be implemented in the following ways.

[0144] (Option 1)

[0145] A reflector having:

[0146] Dielectric layer;

[0147] A conductive layer, formed on a first surface of the dielectric layer, includes a plurality of conductor patterns that reflect incident waves; and

[0148] A grounding layer is formed on the second surface of the dielectric layer on the side opposite to the first surface.

[0149] The conductor patterns are arranged in multiple ways along a predetermined direction.

[0150] Among the plurality of conductor patterns, the standard deviation σ of the difference between the center distance of the reference conductor pattern and the center distance of any conductor pattern along a straight line along the specified direction is greater than 0.5 mm and less than 1.5 mm.

[0151] (Option 2)

[0152] According to the reflector described in Scheme 1, wherein,

[0153] When incident waves of the same phase are incident on a reference conductor pattern and the m-th conductor pattern in the arrangement direction from the reference conductor pattern, the center-to-center distance between the reference conductor pattern with the strongest reflected wave and the m-th conductor pattern is set as the ideal distance dm of the m-th conductor pattern.

[0154] The center-to-center distance between the reference conductor pattern formed on the first surface of the dielectric layer and the m-th conductor pattern is defined as the actual distance dm' of the m-th conductor pattern.

[0155] Let the absolute value of the difference between the actual distance dm' and the ideal distance dm be |dm'-dm|.

[0156] When m is set to an integer greater than or equal to 1

[0157] The standard deviation of the group consisting of |dm'-dm| of each conductor pattern other than the reference conductor pattern is 0.5 mm or more and 1.5 mm or less.

[0158] (Option 3)

[0159] The reflector according to Scheme 1 has:

[0160] An adhesive layer is disposed on the side of the grounding layer opposite to the dielectric layer.

[0161] (Option 4)

[0162] The reflector according to Scheme 1 also has:

[0163] A protective layer that covers the conductive layer.

[0164] (Option 5)

[0165] According to the reflector described in scheme 4, wherein,

[0166] The thickness of the protective layer is 0.1 mm or more and 1.0 mm or less, and the relative permittivity of the protective layer is 2.0 or less.

[0167] (Option 6)

[0168] According to the reflector described in Scheme 1, wherein,

[0169] The thickness of the dielectric layer is 0.3 mm or more and 1.0 mm or less.

[0170] (Option 7)

[0171] According to the reflector described in Scheme 1, wherein,

[0172] The length of the conductor pattern is more than 2.0 mm and less than 5.0 mm.

[0173] (Option 8)

[0174] According to the reflector described in Scheme 1, wherein,

[0175] The reflector has a frequency band of over 6.5 GHz / mm per unit thickness.

[0176] (Option 9)

[0177] The reflector according to any one of schemes 1 to 8, wherein,

[0178] The dielectric layer is formed by a combination of fluorinated resin and inorganic porous aggregate, and the porosity of the dielectric layer is greater than 20%.

[0179] This application claims priority based on Japanese Patent Application No. 2023-058657, filed with the Japan Patent Office on March 31, 2023, and invokes all the contents set forth in that application.

[0180] Explanation of reference numerals in the attached figures

[0181] 10, 20: Reflectors; 11, 21: Dielectric layers; 111, 211: First surfaces; 112, 212: Second surfaces; 12, 22: Grounding layers; 13, 23: Conductive layers; 131, 231: Conductor patterns; 24: Protective layers; 26: Adhesive layers.

Claims

1. A reflector having: Dielectric layer; A conductive layer, formed on the first surface of the dielectric layer, includes multiple conductor patterns that reflect incident waves; as well as A grounding layer is formed on the second surface of the dielectric layer on the side opposite to the first surface. The conductor patterns are arranged in multiple ways along a predetermined direction. Among the plurality of conductor patterns, along the specified direction, the standard deviation σ of the difference between the center distance of the reference conductor pattern and the center distance of any conductor pattern and the ideal distance is greater than 0.5 mm and less than 1.5 mm.

2. The reflector according to claim 1, wherein, When incident waves of the same phase are incident on a reference conductor pattern and the m-th conductor pattern in the arrangement direction from the reference conductor pattern, the center-to-center distance between the reference conductor pattern with the strongest reflected wave and the m-th conductor pattern is set as the ideal distance dm of the m-th conductor pattern. The center-to-center distance between the reference conductor pattern formed on the first surface of the dielectric layer and the m-th conductor pattern is defined as the actual distance dm' of the m-th conductor pattern. Let the absolute value of the difference between the actual distance dm' and the ideal distance dm be |dm'-dm|. When m is set to an integer greater than or equal to 1 The standard deviation of the group consisting of |dm'-dm| of each conductor pattern other than the reference conductor pattern is 0.5 mm or more and 1.5 mm or less.

3. The reflector according to claim 1, comprising: An adhesive layer is disposed on the side of the grounding layer opposite to the dielectric layer.

4. The reflector according to claim 1, further comprising: A protective layer that covers the conductive layer.

5. The reflector according to claim 4, wherein, The thickness of the protective layer is 0.1 mm or more and 1.0 mm or less, and the relative permittivity of the protective layer is 2.0 or less.

6. The reflector according to claim 1, wherein, The thickness of the dielectric layer is 0.3 mm or more and 1.0 mm or less.

7. The reflector according to claim 1, wherein, The length of the conductor pattern is more than 2.0 mm and less than 5.0 mm.

8. The reflector according to claim 1, wherein, The reflector has a frequency band of over 6.5 GHz / mm per unit thickness.

9. The reflector according to any one of claims 1 to 8, wherein, The dielectric layer is formed by a combination of fluorinated resin and inorganic porous aggregate, and the porosity of the dielectric layer is greater than 20%.

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