Reflector

Abstract

A reflector according to one aspect of the present invention comprises: a dielectric layer having a first surface on one side in a thickness direction and a second surface on the other side in the thickness direction; a conductor layer having a plurality of conductor patterns that are disposed at positions separated from each other on the first surface and each reflect an incident radio wave; and a ground layer disposed on the second surface of the dielectric layer. When the beam diameter of a reflected beam based on a reflected wave from each of the plurality of conductor patterns is defined as a reflection angle region between a first reflection angle and a second reflection angle each corresponding to a reflection intensity lower by 5 dB than a peak intensity that is the maximum intensity of the reflected beam, the beam diameter is 10° or more, at least one main peak having the peak intensity and at least one sub peak having a lower reflection intensity than the main peak are present within the peak diameter, and the standard deviation of the reflection intensity within the beam diameter is 1.3 or less.

Description

Reflector

[0001] The present invention relates to a reflector.

[0002] The use of high-frequency radio waves, such as microwaves, millimeter waves, and terahertz waves, in wireless communications enables high-speed, high-capacity communications. However, these high-frequency radio waves tend to travel in a straight line. Therefore, their path may be restricted by obstacles. To alleviate the limitations of communications using high-frequency radio waves, reflectors with multiple conductor patterns on the radio wave incident surface are used.

[0003] For example, Patent Document 1 discloses a reflector such as a radio wave scattering device that includes a first radio wave scattering section in which a plurality of cells are arranged, each including a conductor pattern that scatters an incident beam at a first scattering angle, and a second radio wave scattering section in which a plurality of cells are arranged, each including a conductor pattern that scatters the incident beam at a second scattering angle, the first radio wave scattering section and the second radio wave scattering section being arranged adjacent to each other, and the phase difference between the first radio wave scattering section and the second radio wave scattering section being set to a phase difference that scatters the incident beam at a predetermined scattering angle.

[0004] Japanese Patent Application Laid-Open No. 2022-189533

[0005] If the reflection phase is made different for each of the multiple conductor units, each of which includes multiple conductor patterns, as in the reflector disclosed in Patent Document 1, variations in the intensity distribution of the reflected beam after synthesis may occur. Furthermore, if the variations in the intensity distribution of the reflected beam are large, an area may arise in which reception of the reflected beam is restricted even if the receiving antenna is within the beam diameter.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide a reflector that reduces variations in the intensity distribution of a reflected beam.

[0007] A reflector according to one aspect of the present invention comprises a dielectric layer having a first surface on one side in a thickness direction and a second surface on the other side in the thickness direction; a conductor layer having a plurality of conductor patterns arranged at positions spaced apart from each other on the first surface and reflecting incident radio waves; and a ground layer arranged on the second surface of the dielectric layer, wherein when the beam diameter of a reflected beam based on the reflected wave from each of the plurality of conductor patterns is defined as a reflection angle range of a first reflection angle and a second reflection angle corresponding to a reflection intensity that is 5 dB lower than a peak intensity that is the maximum intensity of the reflected beam, the beam diameter is 10° or more, the beam diameter has a main peak having the peak intensity and at least one sub-peak having a reflection intensity lower than that of the main peak, and the standard deviation of the reflection intensity within the beam diameter is 1.3 or less.

[0008] A reflector according to one aspect of the present invention comprises a dielectric layer having a first surface on one side in a thickness direction and a second surface on the other side in the thickness direction; a conductor layer having a plurality of conductor patterns each arranged at a distance from one another on the first surface and reflecting incident radio waves; and a ground layer arranged on the second surface of the dielectric layer, wherein when the beam diameter of a reflected beam based on the reflected wave from each of the plurality of conductor patterns is defined as a first reflection angle range of first and second reflection angles corresponding to reflection intensities that are 5 dB lower than a peak intensity, which is the maximum intensity of the reflected beam, the beam diameter is 10° or more, the beam diameter has a main peak having the peak intensity and at least one sub-peak having a reflection intensity lower than the main peak, and the intensity difference between the minimum reflection intensity in a second reflection angle range between the peak corresponding to the smallest reflection angle and the peak corresponding to the largest reflection angle among the main peak and the sub-peaks is 3.5 dB or less.

[0009] According to the present invention, it is possible to provide a reflector that reduces variations in the intensity distribution of a reflected beam.

[0010] 1. It is a plan view showing a schematic plane of a reflector according to an embodiment. It is a cross-sectional view showing a schematic cross section of the reflector according to an embodiment taken along line II-II shown in FIG. 1. It is an example of a graph showing a relationship between the length of a conductor pattern and the magnitude of a phase delay of each reflected wave reflected by each conductor pattern. It is an example of a graph showing a spectrum of the reflection intensity of a reflected beam. It is a partially enlarged view showing a main part of a reflected beam within a frame V shown by a dashed line in the graph shown in FIG. 4. It is a diagram showing a schematic diagram of a plurality of conductor patterns arranged in a predetermined direction such as the X-axis direction. It is an angle graph showing the reflection characteristics of a conductor unit in Example 1. It is an angle graph showing the reflection characteristics of a conductor unit in Example 2. It is an angle graph showing the reflection characteristics of a conductor unit in Example 3. It is an angle graph showing the reflection characteristics of a conductor unit in Example 4. It is an angle graph showing the reflection characteristics of a conductor unit in Example 5. It is an angle graph showing the reflection characteristics of a conductor unit in Example 6. It is a graph showing the reflection spectrum of Example 1. It is a graph showing the reflection spectrum of Example 2. It is a graph showing the reflection spectrum of Example 3. 1 is a graph showing the reflection spectrum of Example 4. FIG. 2 is a graph showing the reflection spectrum of Example 5. FIG. 3 is a graph showing the reflection spectrum of Example 6. FIG. 4 is a graph showing the reflection spectrum of Comparative Example 1. FIG. 5 is a graph showing the reflection spectrum of Comparative Example 2.

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same components are given the same reference numerals, and duplicated descriptions will be omitted as appropriate.

[0012] The following embodiments are intended to exemplify reflectors that embody the technical concepts of the present invention, and are not intended to limit the present invention to the following embodiments. The dimensions, materials, shapes, relative positions, and other details of the components described below are intended for illustrative purposes only, unless otherwise specified, and are not intended to limit the scope of the present invention. Furthermore, the sizes and positional relationships of components shown in the drawings may be exaggerated for clarity.

[0013] In the following drawings, directions may be indicated by the mutually orthogonal X-axis, Y-axis, and Z-axis. The X-axis direction corresponds to the width direction of the reflector according to the embodiment. The Y-axis direction corresponds to the depth direction of the reflector according to the embodiment. The Z-axis direction corresponds to the thickness direction of the reflector according to the embodiment. A direction parallel to the XY plane including the X-axis direction and the Y-axis direction may be referred to as an in-plane direction. The Z-axis direction may also be referred to as the perpendicular-to-plane direction or the thickness direction.

[0014] The direction in which the arrow points in the X-axis direction is referred to as the +X direction or +X side, and the direction opposite to the +X direction is referred to as the -X direction or -X side. The direction in which the arrow points in the Y-axis direction is referred to as the +Y direction or +Y side, and the direction opposite to the +Y direction is referred to as the -Y direction or -Y side. The direction in which the arrow points in the Z-axis direction is referred to as the +Z direction or +Z side, and the direction opposite to the +Z direction is referred to as the -Z direction or -Z side.

[0015] [Embodiment] An example of the configuration of a reflector 1 according to an embodiment will be described with reference to Figures 1 and 2. Figure 1 is a plan view schematically showing a plane of the reflector 1 according to the embodiment. Figure 2 is a cross-sectional view schematically showing a cross section of the reflector 1 according to the embodiment taken along line II-II shown in Figure 1.

[0016] The reflector 1 according to the embodiment emits a reflected beam BM based on a reflected wave of an incident radio wave. Examples of incident radio waves include high-frequency radio waves such as microwaves, millimeter waves, and terahertz waves. Here, microwaves are, for example, radio waves in a frequency band of about 3 GHz to about 30 GHz. Millimeter waves are radio waves in a frequency band of about 30 GHz to about 300 GHz. Terahertz waves are radio waves in a frequency band of about 300 GHz to about 10 THz. However, the frequencies of the radio waves incident on the reflector 1 are not limited to these.

[0017] The reflected beam BM emitted from the reflector 1 corresponds to a composite wave of reflected waves reflected by each of the multiple conductor patterns 21 of the conductor layer 20, which will be described separately. The composite of the multiple reflected waves generates, for example, a main lobe having a large distribution of reflection intensity over a relatively wide reflection angle range (hereinafter referred to as "intensity distribution") and side lobes over reflection angle ranges different from the reflection angle range of the main lobe. In this specification, the reflected beam BM is defined as a composite wave corresponding to the main lobe.

[0018] The reflection angle range of the reflected beam BM may be referred to as the "beam diameter" below. Details of the "beam diameter" will be explained separately. In the following explanation, the "reflection angle" or "angle" refers to the angle when the normal direction of the reflector 1 is set to 0°. The normal direction of the reflector 1 according to the embodiment corresponds to the Z-axis direction.

[0019] 1 and 2, the reflector 1 includes a dielectric layer 10, a conductor layer 20, and a ground layer 30. The reflector 1 may further include other components such as a protective layer that protects the incident surface of the reflector 1 and an adhesive layer that adheres the reflector 1 to an external member. The components included in the reflector 1 will be described below.

[0020] <Dielectric Layer 10> An example of the configuration of the dielectric layer 10 will be described. As shown in Fig. 2, the dielectric layer 10 is a plate-like member having a first surface 11a on one side in the thickness direction and a second surface 11b on the other side in the thickness direction. In the example shown in Fig. 1, the dielectric layer 10 has a substantially rectangular shape in plan view. However, the dielectric layer 10 may have other shapes in plan view, such as a substantially circular shape, a substantially elliptical shape, or a substantially polygonal shape other than a rectangle.

[0021] Examples of materials that can be used to form the dielectric layer 10 include polymeric materials such as polyethylene resin, polypropylene resin, and polystyrene resin. However, the material that can be used to form the dielectric layer 10 is not limited to these materials and can be other materials such as ceramics or glass. Furthermore, the material that can be used to form the dielectric layer 10 can be a composite material containing a fluorine-based resin and an inorganic porous aggregate. Examples of inorganic porous aggregates include those disclosed in Japan Patent Office Publication No. 2017-171898.

[0022] Here, as fluorine-based resin, polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTEF), tetrafluoroethylene-ethylene copolymer (ETFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), these can be used alone or in combination of two or more kinds.Among them, PTFE is particularly preferred.

[0023] The fluororesin is preferably "fibrillated (fibrous structured)." It is more preferable that the fibrillated fibers are oriented not only in one direction but in multiple directions. It is particularly preferable that the fibrils and inorganic fine particle aggregates are linked to form a "three-dimensional micromesh structure." When the fibrillated fluororesin and inorganic fine particle aggregates are linked to form a three-dimensional micromesh structure, the composite material can ensure excellent mechanical strength and dimensional stability. The fibrillation of the fluororesin can be promoted by, for example, applying a shear force, but more specifically, it is preferably carried out by multi-stage rolling. The three-dimensional micromesh structure is preferably formed by anti-directional multi-stage rolling.

[0024] When the dielectric layer 10 contains, for example, a fluorine-based resin and an aggregate of inorganic fine particles, the dielectric layer 10 has a porosity represented by formula (1). The porosity is a value calculated by measuring the bulk density and true density of the material to be the pore-containing layer and substituting them into formula (1).

[0025] Porosity [%] = (1 - (bulk density [g / cm 3] of the material containing fluorine-based resin and inorganic fine particle aggregates) ３ ] / true density [g / cm 3 of the material containing fluorine-based resin and inorganic fine particle aggregates ３ ])) × 100 ... (1)

[0026] The porosity of the dielectric layer 10 is preferably 30% or more, more preferably 35% or more, even more preferably 40% or more, even more preferably 45% or more, and particularly preferably 50% or more. The porosity of the dielectric layer 10 is preferably 80% or less, more preferably 70% or less. When the porosity of the dielectric layer 10 is within the above range, it is possible to ensure favorable properties such as a dielectric constant and a coefficient of expansion as a composite material.

[0027] The relative dielectric constant of the dielectric layer 10 is not particularly limited. As an example, the relative dielectric constant of the dielectric layer 10 is preferably, for example, 1.5 or more and 5.0 or less. By setting the relative dielectric constant of the dielectric layer 10 to 1.5 or more and 5.0 or less, the flight distance of the reflected beam BM can be increased. Furthermore, the relative dielectric constant of the dielectric layer 10 is preferably, for example, 1.5 or more and 2.0 or less. By setting the relative dielectric constant of the dielectric layer 10 to 1.5 or more and 2.0 or less, the flight distance of the reflected beam BM can be further increased. However, the relative dielectric constant of the dielectric layer 10 is not limited to these. Note that "relative dielectric constant" will hereinafter be referred to as "dielectric constant".

[0028] Although there are no particular limitations on the thickness of the dielectric layer 10, it is preferably 0.1 mm to 1.0 mm. By setting the thickness of the dielectric layer 10 within this range, the flight distance of the reflected beam BM can be increased.

[0029] <Conductor Layer 20> An example of the configuration of the conductor layer 20 will be described. As shown in FIGS. 1 and 2 , the conductor layer 20 has a plurality of conductor patterns 21. The plurality of conductor patterns 21 are arranged at positions spaced apart from one another on the first surface 11a of the dielectric layer 10. In the example shown in FIG. 2 , the plurality of conductor patterns 21 are arranged along the X-axis direction. However, the arrangement direction of the plurality of conductor patterns 21 is not limited to the X-axis direction. For example, the plurality of conductor patterns 21 may be arranged in a matrix along each of the X-axis direction and the Y-axis direction. Furthermore, the plurality of conductor patterns 21 may be arranged in a direction different from the X-axis direction or the Y-axis direction.

[0030] 1 , each of the plurality of conductor patterns 21 has a shape known as a cross dipole, in which a strip-shaped pattern extending along the X-axis direction intersects with another strip-shaped pattern extending along the Y-axis direction in a plan view. However, the shape of the conductor pattern 21 is not limited to a cross dipole. Other examples of the shape of the conductor pattern 21 include a substantially circular, substantially elliptical, or substantially rectangular shape in a plan view.

[0031] Examples of materials constituting each of the plurality of conductive patterns 21 include metals such as titanium, silicon, niobium, indium, zinc, tin, gold, silver, copper, aluminum, cobalt, chromium, nickel, lead, iron, palladium, platinum, tungsten, zirconium, tantalum, and hafnium; conductive metal oxides such as ITO (oxide of indium and tin), zinc oxide, and tin oxide; and materials containing two or more of these metals or metal oxides, or alloys containing these metals as the main component.

[0032] 2 , the +Z side surface (front surface) of each of the plurality of conductor patterns 21 and the first surface 11a of the dielectric layer 10 form an incident surface on which incident radio waves enter the reflector 1. Here, the incident radio waves that enter the reflector 1 are reflected by each of the plurality of conductor patterns 21. That is, a plurality of reflected waves are generated that are reflected by each of the plurality of conductor patterns 21. A reflected beam BM is radiated from the reflector 1 by combining the plurality of reflected waves.

[0033] <Ground Layer 30> An example of the configuration of the ground layer 30 will be described. The ground layer 30 is a conductor layer disposed on the second surface 11b of the dielectric layer 10. Examples of materials that can be used to form the ground layer 30 include metals such as titanium, silicon, niobium, indium, zinc, tin, gold, silver, copper, aluminum, cobalt, chromium, nickel, lead, iron, palladium, platinum, tungsten, zirconium, tantalum, and hafnium; and conductive metal oxides such as ITO, zinc oxide, and tin oxide. The ground layer 30 may also be made of a material containing two or more of these metals or metal oxides, or an alloy containing these metals as the main component.

[0034] <Reflected Beam BM> Next, the reflected beam BM emitted from the reflector 1 will be described. As a prerequisite for describing the reflected beam BM, the phase of the reflected wave reflected by the conductor pattern 21 will be described with reference to FIG. 3. FIG. 3 is an example of a graph that schematically illustrates the relationship between the length L of the conductor pattern 21 and the magnitude of the phase delay of each reflected wave reflected by each conductor pattern 21. The horizontal axis of FIG. 3 corresponds to the length L of the conductor pattern 21. An example of the length L of the conductor pattern 21 is the length along the X-axis direction (see FIGS. 1 and 2). The vertical axis of FIG. 3 corresponds to the magnitude of the phase delay of the reflected wave from each conductor pattern 21. Here, each numerical value shown on the vertical axis of FIG. 3 is denoted by a minus sign. A larger negative value, i.e., a larger absolute value, indicates a larger magnitude of the phase delay. The magnitude of the phase delay will hereinafter be referred to as "phase."

[0035] Each of the multiple conductor patterns 21 and the ground layer 30 face each other across the dielectric layer 10 (see FIG. 2 ). Therefore, a capacitance corresponding to, for example, the length L of each conductor pattern 21 is formed in the region of the dielectric layer 10 between each conductor pattern 21 and the ground layer 30. As shown in FIG. 3 , the phase of each reflected wave reflected by each conductor pattern 21 can be controlled by geometric conditions such as the length L of each conductor pattern 21. Note that the phase of the reflected wave reflected by the conductor pattern 21 also varies depending on other parameters, such as the length of the conductor pattern 21 along the Y-axis direction, the area of ​​the conductor pattern 21, the thickness and dielectric constant of the dielectric layer 10, and the shape (area) of the ground layer 30. In practice, the phase of the reflected wave reflected by the conductor pattern 21 can be controlled by changing one of these parameters, including the length L of the conductor pattern 21, while fixing the other parameters.

[0036] Next, an example of the relationship between the phase of the reflected wave from each of the multiple conductor patterns 21 and the peak angle of the reflected beam BM will be described. As described above, the reflected beam BM is a composite wave of reflected waves that has a large reflection intensity over a relatively wide reflection angle range. Therefore, the peak angle of the reflected beam BM described below corresponds to the reflection angle corresponding to the peak intensity (maximum reflection intensity) of the reflection intensity of the reflected beam BM. For convenience of explanation, the following description will be given using as an example a reflector 1 in which two conductor patterns 21 are arranged on the first surface 11 a of the dielectric layer 10.

[0037] When the phase of the reflected wave from one of the two conductor patterns 21 is δ1, the phase of the reflected wave from the other is δ2, the wavelength of the incident radio wave is λ, the pitch of the two conductor patterns 21 (for example, the distance between the centers of the two conductor patterns 21) is d, and the peak angle of the reflected beam BM is θp, theoretically, the peak angle θp has the relationship shown in equation (2) with the phases δ1 and δ2 of the reflected waves.

[0038] sin(θp) = [(δ1-δ2)・λ] / (2πd) ...(2)

[0039] From equation (2), a reflected beam BM having a desired peak angle θp can be obtained according to the phase difference (δ1−δ2) between the reflected waves from the two conductor patterns 21.

[0040] Next, the reflected beam BM in this specification will be described in detail with reference to FIGS. 4 and 5. FIG. 4 is an example of a graph schematically showing the reflection intensity spectrum of the reflected beam BM (hereinafter referred to as the "reflection spectrum"). In FIG. 4, a positive reflection angle means an angle tilted toward the +X side with respect to the normal direction of the reflector 1. Also, in FIG. 4, a negative reflection angle means an angle tilted toward the -X side with respect to the normal direction of the reflector 1. The same applies to other figures showing reflection angles. Also, FIG. 5 is a partially enlarged view showing a main portion of the reflected beam BM within a frame V indicated by a dashed line in the graph shown in FIG. 4.

[0041] The horizontal axes in Figures 4 and 5 represent the reflection angle θ of the reflected wave including the reflected beam BM. The vertical axes in Figures 4 and 5 represent the reflection intensity (unit: dB) corresponding to each reflection angle θ. Here, the reflection intensity shown on the vertical axis in Figure 4 is the logarithm of the ratio to the incident intensity of the incident radio wave. Specifically, when the incident intensity is "I" and the reflection intensity S(θ) at an arbitrary reflection angle θ is "Sr(θ)," the reflection intensity Sr(θ) [unit: dB] shown in Figures 4 and 5 corresponds to the value calculated by equation (3).

[0042] Sr(θ)=log(S(θ) / I)...(3)

[0043] As used herein, the term "beam diameter" refers to the reflection angle range W between the first reflection angle θ1 and the second reflection angle θ2, which corresponds to a reflection intensity 5 dB lower than the peak intensity Sm, as shown in FIG. 5 , and is defined as a reflection angle range W of 10° or more. The beam diameter may also be a reflection angle range W of 10° or more and 90° or less. The beam diameter may also be a reflection angle range W of 10° or more and 50° or less. The first reflection angle θ1 corresponds to the smallest reflection angle within the reflection angle range W related to the beam diameter. The second reflection angle θ2 corresponds to the largest reflection angle within the reflection angle range W related to the beam diameter. The reflection angle range W is an example of a "first reflection angle range." A reflection angle range W of 10° or more allows the reflected beam BM to reach a wide area. In other words, communication radio waves can reach a wide area via the reflector 1.

[0044] As shown in Figures 4 and 5, the reflection spectrum within the beam diameter has mountain-shaped regions and valley-shaped regions corresponding to repeated increases and decreases in reflection intensity. That is, the reflection spectrum within the beam diameter has multiple sub-peaks P with reflection intensities smaller than the peak intensity Sm. In this specification, the reflected beam BM is defined as having at least one sub-peak P in addition to the peak corresponding to the peak intensity Sm. In the example shown in Figures 4 and 5, five sub-peaks P occur in the reflected beam BM. Note that the peak corresponding to the peak intensity Sm in the reflected beam BM is referred to as the "main peak Pm." When the main peak Pm and the sub-peaks P are described without distinction, they are collectively referred to as a "peak" or a "peak group."

[0045] The reflected beam BM may have 1 to 1000 sub-peaks P. Furthermore, the reflected beam BM may have 1 to 100 sub-peaks P.

[0046] The standard deviation σ of the reflection intensity of the reflected beam BM contained within the beam diameter is preferably 1.3 or less. The standard deviation σ of the reflection intensity of the reflected beam BM may be 0 or greater and 1.3 or less. Furthermore, the standard deviation σ of the reflection intensity of the reflected beam BM may be 0.1 or greater and 1.3 or less. Here, the standard deviation σ of the reflection intensity of the reflected beam BM may be, for example, the standard deviation of the group of reflection intensities S(θ) of the reflected beam BM over the reflection angle θ of the reflection angle range W. The standard deviation σ of the reflection intensity of the reflected beam BM may also be the standard deviation of the group of reflection intensities of the subpeaks P of the reflected beam BM. By setting the standard deviation σ of the reflection intensity of the reflected beam BM to, for example, 0 or greater and 1.3 or less, the variation in the intensity distribution of the reflected beam BM having a relatively large beam diameter can be reduced. As a result, the limitations on radio wave reception in the area contained within the beam diameter can be reduced.

[0047] 4 and 5, in a reflection angle range W1 between the main peak Pm or sub-peak P with the smallest reflection angle and the main peak Pm or sub-peak P with the largest reflection angle among the peaks of the reflected beam BM, the difference in intensity between the smallest reflection intensity and the peak intensity Sm is preferably 3.5 dB or less. The reflection angle range W1 is an example of a "second reflection angle range."

[0048] The difference between the smallest reflection intensity and the peak intensity Sm in the reflection angle range W1 may be 0 dB or more and 3.5 dB or less. The difference between the smallest reflection intensity and the peak intensity Sm in the reflection angle range W1 may be 0.1 dB or more and 3.5 dB or less. By making the difference between the smallest reflection intensity and the peak intensity Sm in the reflection angle range W1 3.5 dB or less, the variation in the intensity distribution of the reflected beam BM, which has a relatively large beam diameter, can be reduced. As a result, the limitations on radio wave reception in the area included in the beam diameter can be reduced.

[0049] <Configuration Example for Reducing Variation in Intensity Distribution of Reflected Beam BM> Next, a configuration example for reducing variation in intensity distribution of reflected beam BM will be described with reference to Fig. 6. Fig. 6 is a diagram schematically showing a plurality of conductor patterns 21 arranged in a predetermined direction, such as the X-axis direction.

[0050] The reflector 1 according to the embodiment preferably includes the following configuration as an example for reducing variations in the intensity distribution of the reflected beam BM. That is, the reflector 1 includes a plurality of conductor units 21U, each having a plurality of conductor patterns 21 whose phases are adjusted so that the phase differences between adjacent conductor patterns 21 are approximately the same. The phase differences between the conductor patterns 21 belonging to each of the plurality of conductor units 21U are different for each conductor unit 21U. That is, the reflection angles of the plurality of sub-beams radiated from each of the plurality of conductor units 21U are different. Here, the sub-beams radiated from each conductor unit 21U correspond to a composite wave of reflected waves reflected by each of the plurality of conductor patterns 21 constituting the conductor unit 21U. However, the sub-beams are conceptually used for convenience of explanation, and in reality, the sub-beams radiated from each conductor unit 21U are not distinguishable from one another.

[0051] 6, three conductor units 21U are provided in the reflector 1. The conductor units 21U are arranged along the X-axis direction. However, the number and arrangement direction of the conductor units 21U are not limited to these.

[0052] In FIG. 6 , the conductor unit 21U1, which is closest to the -X side, is composed of conductor patterns 21a, 21b, and 21c. Here, to adjust the reflection angle Θ1 of the sub-beams from the conductor unit 21U1, the phase difference between the conductor patterns 21a and 21b and the phase difference between the conductor patterns 21b and 21c are made substantially identical. For example, to achieve the reflection angle Θ1 of the sub-beams from the conductor unit 21U1, the phase difference between the conductor patterns 21a and 21b and the phase difference between the conductor patterns 21b and 21c are each adjusted to "α." However, the phase difference between the conductor patterns 21a and 21b and the phase difference between the conductor patterns 21b and 21c may differ by an allowable error.

[0053] The conductor unit 21U2, which is adjacent to the conductor unit 21U1 on the +X side, is composed of conductor patterns 21c, 21d, and 21e. The conductor pattern 21c is shared between the adjacent conductor units 21U1 and 21U2. Here, to adjust the reflection angle Θ2 of the sub-beam from the conductor unit 21U2, the phase difference between the conductor patterns 21c and 21d and the phase difference between the conductor patterns 21d and 21e are made substantially identical. For example, the phase difference between the conductor patterns 21c and 21d and the phase difference between the conductor patterns 21d and 21e are each adjusted to "β" so as to achieve the reflection angle Θ2 of the sub-beam from the conductor unit 21U2. However, the phase difference between the conductor patterns 21c and 21d and the phase difference between the conductor patterns 21d and 21e may differ by an allowable error.

[0054] In FIG. 6 , the conductor unit 21U3, which is closest to the +X side, is composed of conductor patterns 21e and 21f. The conductor pattern 21e is shared between the adjacent conductor units 21U2 and 21U3. Here, the phase difference between the conductor patterns 21e and 21f is adjusted to adjust the reflection angle Θ3 of the sub-beam from the conductor unit 21U3. For example, the phase difference between the conductor patterns 21e and 21f is adjusted to "γ" so that the reflection angle of the sub-beam from the conductor unit 21U3 is Θ3. However, the phase difference between the conductor patterns 21e and 21f may differ from γ by an allowable error.

[0055] In other words, one conductor unit 21U is composed of a plurality of conductor patterns 21 arranged so that the phase differences of reflected waves between adjacent conductor patterns 21 are the same. Here, "having the same phase differences" includes cases where the phase differences are completely identical, as well as cases where there is an error of within ±5% from the desired phase difference. The plurality of conductor units 21U are arranged on the first surface 11a of the dielectric layer 10. Each of the plurality of conductor units 21U radiates a sub-beam having a reflection angle Θ corresponding to the phase difference of reflected waves between the conductor patterns 21 belonging to that conductor unit 21U.

[0056] The reflection angle Θ of the multiple conductor units 21U may vary linearly or randomly depending on the position of each conductor unit 21U (in FIG. 6 , the position in the X-axis direction: X-axis coordinate). However, even when the reflection angle Θ of the multiple conductor units 21U varies randomly, it is preferable to comply with, for example, the following condition. The following condition is an example of a "predetermined condition."

[0057] For example, in an angle graph in which the horizontal axis specifies the position of each conductor unit 21U and the vertical axis specifies the reflection angle Θ of the sub-beam from each conductor unit 21U, the minimum and maximum values ​​of the regression line of the reflection angle Θ of the sub-beam from each conductor unit 21U may be set to have predetermined values. An example of the minimum value of the regression line is a value within a range of ±5° with respect to the first reflection angle θ1 that specifies one end of the beam diameter of the reflected beam BM in the angle graph. The minimum value of the regression line is the value at the center position of the conductor pattern 21 that is located closest to one end in the predetermined direction among the conductor patterns 21 arranged in the predetermined direction. In FIG. 6, the value is at the center position of the conductor pattern 21a that is located closest to the -X side.

[0058] In contrast, an example of the maximum value of the regression line is a value within a range of ±5° with respect to the second reflection angle θ2 that defines the other end of the beam diameter of the reflected beam BM in the angle graph. The maximum value of the regression line is the value at the center position of the conductor pattern 21 furthest from the other end in the predetermined direction among the conductor patterns 21 arranged in the predetermined direction. In Figure 6, this value is the value at the center position of the conductor pattern 21 furthest from the +X side.

[0059] The number of conductor patterns 21 constituting a conductor unit 21U is arbitrary. Furthermore, as shown in FIG. 6 , it is preferable that at least one of the conductor patterns 21 is shared between two adjacent conductor units 21U. In other words, it is preferable that, among the conductor patterns 21 constituting each of two adjacent conductor units 21U, the conductor pattern 21 on the other end side of one conductor unit 21U is the same as the conductor pattern 21 on one end side of the other conductor unit 21U. Furthermore, it is preferable that 50% or more of all conductor units 21U share a conductor pattern 21 with an adjacent conductor unit 21U. Furthermore, it is preferable that 80% or more of all conductor units 21U share a conductor pattern 21 with an adjacent conductor unit 21U. Furthermore, it is preferable that 100% or less of all conductor units 21U share a conductor pattern 21 with an adjacent conductor unit 21U. Furthermore, it is preferable that 90% or less of all conductor units 21U share the conductor pattern 21 with adjacent conductor units 21U. This reduces the variation in the intensity distribution of the reflected beam BM, which has a relatively large beam diameter. As a result, the limitations on radio wave reception in the area included in the beam diameter can be reduced. Furthermore, by randomly varying the reflection angle Θ of the multiple conductor units 21U under specified conditions, the variation in the intensity distribution of the reflected beam BM can be further reduced.

[0060] Next, the present invention will be described in more detail using examples and comparative examples, but the present invention is not limited to the examples shown below.

[0061] Examples 1 to 6 and Comparative Example 2 shown below correspond to simulation results of the reflection spectrum of the reflector 1 when radio waves (frequency: approximately 28 GHz) are incident from the normal direction. Comparative Example 1 corresponds to the reflection spectrum disclosed as Figure 8(c) in Patent Document 1 mentioned above.

[0062] In Examples 1 to 6, the reflection characteristics of the conductor unit 21U were set as shown in Figs. 7 to 12. Fig. 7 is an angle graph showing the reflection characteristics of the conductor unit 21U in Example 1. Fig. 8 is an angle graph showing the reflection characteristics of the conductor unit 21U in Example 2. Fig. 9 is an angle graph showing the reflection characteristics of the conductor unit 21U in Example 3. Fig. 10 is an angle graph showing the reflection characteristics of the conductor unit 21U in Example 4. Fig. 11 is an angle graph showing the reflection characteristics of the conductor unit 21U in Example 5. Fig. 12 is an angle graph showing the reflection characteristics of the conductor unit 21U in Example 6.

[0063] 13 to 20 show the reflection spectra of Examples 1 to 6, and Comparative Examples 1 and 2. FIG. 13 shows the reflection spectrum of Example 1. FIG. 14 shows the reflection spectrum of Example 2. FIG. 15 shows the reflection spectrum of Example 3. FIG. 16 shows the reflection spectrum of Example 4. FIG. 17 shows the reflection spectrum of Example 5. FIG. 18 shows the reflection spectrum of Example 6. FIG. 19 shows the reflection spectrum of Comparative Example 1. FIG. 20 shows the reflection spectrum of Comparative Example 2. Note that FIG. 19 cites FIG. 8(c) of Patent Document 1.

[0064] The horizontal axis of the angle graphs shown in FIGS. 7 to 12 corresponds to numbers for identifying each of the multiple conductor units 21U. The conductor unit 21U identified by number 1 refers to the conductor unit 21U located closest to one end in a predetermined direction (e.g., the X-axis direction or the Y-axis direction) on the conductor layer 20. As the number increases, the conductor unit 21U is closer to the other end in the predetermined direction. Each of Examples 1 to 6 includes 80 conductor units 21U. Furthermore, in each of Examples 1 to 6, the proportion of conductor units 21U that share a conductor pattern 21 (the number of conductor units 21U that share a conductor pattern 21 relative to all conductor units 21U) was set to 50% or more and 100% or less. In each of Examples 1 to 6, the proportion of conductor units 21U that share a conductor pattern 21 was the same.

[0065] The vertical axis of the angle graphs shown in Figures 7 to 12 corresponds to the reflection angle Θ of the sub-beams from each conductor unit 21U. The angle graphs in Figures 7 to 12 show regression lines as dashed lines. The minimum value of the regression line (the minimum value of the reflection angle on the regression line) shown in each of Figures 7 to 12 is the reflection angle on the regression line for the conductor unit 21U identified by the smallest number (e.g., number 1). Furthermore, the maximum value of the regression line (the maximum value of the reflection angle on the regression line) shown in each of Figures 7 to 12 is the reflection angle on the regression line for the conductor unit 21U identified by the largest number (e.g., number 80). Although Figures 7 to 12 are actually scatter plots of plotted points indicating the reflection angle Θ of the sub-beams from each conductor unit 21U, adjacent plotted points are connected by straight lines, so they are represented as line graphs. Furthermore, the dashed lines shown in each of Figures 7 to 12 correspond to the regression lines based on the reflection angle Θ of the sub-beams from each conductor unit 21U. The regression line was determined using the least squares method.

[0066] 7 to 12 , for each Example, the reflection angle on the regression line (minimum value of the regression line) for the conductor unit 21U with the smallest number, 1, falls within a range of ±5° with respect to the first reflection angle θ1 for each Example (see FIGS. 13 to 18 ). Also, for each Example, the reflection angle on the regression line (maximum value of the regression line) for the conductor unit 21U with the largest number, 80, falls within a range of ±5° with respect to the second reflection angle θ2 for each Example (see FIGS. 13 to 18 ).

[0067] In Comparative Example 1, the reflection characteristics of the conductor units are set as described in, for example, paragraphs

[0053] to

[0057] of the specification of Patent Document 1. In Comparative Example 1, adjacent conductor units do not share a conductor pattern.

[0068] In Comparative Example 2, all of the conductor patterns are arranged so that the phase differences between any two adjacent conductor patterns are equal, i.e., Comparative Example 2 does not include a conductor unit including multiple conductor patterns.

[0069] Table 1 shows the main characteristic values ​​of Examples 1 to 6 and Comparative Examples 1 and 2. Note that the "intensity difference (dB)" in Table 1 corresponds to the intensity difference between the smallest reflection intensity and the peak intensity Sm in the reflection angle range W1.

[0070]

[0071] 13 to 18 and Table 1, in all of Examples 1 to 6, a reflected beam BM having a beam diameter of 10° or more was obtained. Furthermore, in all of Examples 1 to 6, the standard deviation σ was 1.3 or less, and the intensity difference between the smallest reflection intensity and the peak intensity Sm in the reflection angle range W1 was 3.5 dB or less. In other words, in each Example, it was possible to reduce the variation in the intensity distribution of the reflected beam BM having a relatively large beam diameter.

[0072] In contrast, in Comparative Example 1, the beam diameter was smaller and the variation in the intensity distribution of the reflected beam BM was greater than in Examples 1 to 6. In Comparative Example 2, a reflected beam BM with a small beam diameter was obtained. In other words, in Comparative Example 2, there is room for improvement in terms of making the reflected beam BM reach a wider area.

[0073] The present invention can be embodied, for example, as follows: <1> A reflector comprising: a dielectric layer having a first surface on one side in a thickness direction and a second surface on the other side in the thickness direction; a conductor layer having a plurality of conductor patterns arranged at positions spaced apart from each other on the first surface and reflecting incident radio waves; and a ground layer arranged on the second surface of the dielectric layer, wherein when a beam diameter of a reflected beam based on a wave reflected from each of the plurality of conductor patterns is defined as a reflection angle range of a first reflection angle and a second reflection angle corresponding to a reflection intensity that is 5 dB lower than a peak intensity that is the maximum intensity of the reflected beam, the beam diameter is 10° or more, the beam diameter has at least one main peak having the peak intensity and one sub-peak having a reflection intensity lower than the main peak, and the standard deviation of the reflection intensity within the beam diameter is 1.3 or less. <2> A reflector comprising: a dielectric layer having a first surface on one side in a thickness direction and a second surface on the other side in the thickness direction; a conductor layer having a plurality of conductor patterns arranged at positions spaced apart from each other on the first surface and reflecting incident radio waves; and a ground layer arranged on the second surface of the dielectric layer, wherein when a beam diameter of a reflected beam based on a reflected wave from each of the plurality of conductor patterns is defined as a first reflection angle range of first and second reflection angles corresponding to reflection intensities that are 5 dB lower than a peak intensity that is the maximum intensity of the reflected beam, the beam diameter is 10° or more, the beam diameter has at least one main peak having the peak intensity and one sub-peak having a reflection intensity lower than the main peak, and an intensity difference between the minimum reflection intensity in a second reflection angle range between the peak corresponding to the smallest reflection angle and the peak corresponding to the largest reflection angle among the main peak and the sub-peak and the peak corresponding to the largest reflection angle is 3.5 dB or less.<3> The reflector according to <1> or <2>, wherein a plurality of the conductor patterns arranged so that the phase difference of the reflected waves between adjacent conductor patterns is the same constitute one conductor unit, a plurality of the conductor units are arranged on the first surface of the dielectric layer, each of the plurality of conductor units emits a sub-beam having a reflection angle according to the phase difference of the reflected waves between the conductor patterns belonging to the respective conductor units, and 50% or more of the plurality of conductor units share at least one conductor pattern with an adjacent conductor unit. <4> The reflector according to any one of <1> to <3>, wherein the dielectric constant of the dielectric layer is 2.0 or less. <5> The reflector according to any one of <1> to <4>, wherein the dielectric layer includes a fluorine-based resin and an inorganic porous aggregate, and wherein the porosity of the dielectric layer is 50% or more.

[0074] This application claims priority based on Japanese Patent Application No. 2024-055489, filed on March 29, 2024, the entire contents of which are incorporated herein by reference.

[0075] REFERENCE SIGNS LIST 1 reflector 10 dielectric layer 11a first surface 11b second surface 20 conductor layer 21 conductor pattern 21U conductor unit 30 ground layer BM reflected beam

Claims

1. A reflector comprising: a dielectric layer having a first surface on one side in the thickness direction and a second surface on the other side in the thickness direction; a conductor layer having a plurality of conductor patterns arranged at positions spaced apart from each other on the first surface and reflecting incident radio waves; and a ground layer arranged on the second surface of the dielectric layer; wherein, when the beam diameter of a reflected beam based on the reflected wave from each of the plurality of conductor patterns is defined as a reflection angle range of a first reflection angle and a second reflection angle corresponding to a reflection intensity that is 5 dB lower than a peak intensity that is the maximum intensity of the reflected beam, the beam diameter is 10° or more; the beam diameter has at least one main peak having the peak intensity and one sub-peak having a reflection intensity lower than the main peak; and the standard deviation of the reflection intensity within the beam diameter is 1.3 or less.

2. A reflector comprising: a dielectric layer having a first surface on one side in the thickness direction and a second surface on the other side in the thickness direction; a conductor layer having a plurality of conductor patterns arranged at positions spaced apart from each other on the first surface and reflecting incident radio waves; and a ground layer arranged on the second surface of the dielectric layer; wherein, when the beam diameter of a reflected beam based on the reflected wave from each of the plurality of conductor patterns is defined as a first reflection angle range of first and second reflection angles corresponding to reflection intensities 5 dB lower than a peak intensity which is the maximum intensity of the reflected beam, the beam diameter is 10° or more; the beam diameter has at least one main peak having the peak intensity and one sub-peak having a reflection intensity lower than the main peak; and the intensity difference between the minimum reflection intensity in a second reflection angle range between the peak corresponding to the smallest reflection angle and the peak corresponding to the largest reflection angle among the main peak and the sub-peaks is 3.5 dB or less.

3. A reflector as claimed in claim 1 or claim 2, wherein a plurality of the conductor patterns arranged so that the phase difference of the reflected waves between adjacent conductor patterns is the same constitutes one conductor unit, a plurality of the conductor units are arranged on the first surface of the dielectric layer, each of the plurality of conductor units emits a sub-beam having a reflection angle according to the phase difference of the reflected waves between the conductor patterns belonging to the respective conductor unit, and 50% or more of the plurality of conductor units share at least one conductor pattern with an adjacent conductor unit.

4. The reflector according to claim 1 or 2, wherein the dielectric layer has a dielectric constant of 2.0 or less.

5. The reflector according to claim 1 or 2, wherein the dielectric layer contains a fluorine-based resin and an inorganic porous aggregate, and the porosity of the dielectric layer is 50% or more.

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