Radio wave reflector

Abstract

We provide a radio wave reflector that can transmit radio waves over a wide area. [Solution] The radio wave reflector reflects radio waves of wavelength λ, multiple reflecting elements are arranged in the X and Y directions, the substrate layer is divided into n regions Ak in the X direction, reflecting elements are periodically arranged within each region Ak and divided into one or more sections, the length of the section in the X direction Pk, the length of each region Ak in the X direction Lk, the maximum value of Lk among the n Lk (k=1~n) Lmax, the sum of the n Lk Ls, the set of regions Ak that satisfy condition 1 G1, and the set of other regions Ak G2, then conditions 2 and 3 are satisfied. (Condition 1) 0.35≦Lk / Lmax≦1 (Condition 2) (Sum of lengths Lk of regions Ak belonging to set G2 LG2) / Ls ≤ 0.35 (Condition 3) In each region Ak belonging to the set G1, Pk ≥ λ / 2, and for all other regions Ak' (k' ≠ k, and 1 ≤ k' ≤ n) belonging to the set G1, Pk ≠ Pk'

Description

Technical Field

[0001] The present invention relates to a radio wave reflector for reflecting radio waves.

Background Art

[0002] In mobile phones and wireless communications, radio waves in a frequency band of about 2 GHz or more and 300 GHz or less, called centimeter waves and millimeter waves, are used. Such radio waves with short wavelengths have strong directivity and are difficult to bend around obstacles. Therefore, in order to spread radio waves over a wide area, a reflector is provided on the surface of a building such as the walls, floors, ceilings, columns, etc. of the building (hereinafter referred to as "walls, etc."). For example, Patent Document 1 proposes a communication system in which a monopole antenna and a metal reflector for reflecting radio waves are arranged in an indoor underfloor space. The metal reflector diffuses the radio waves radiated from the monopole antenna in the underfloor space and prevents the radio waves from leaking from the underfloor space to the outside of the living room (building) or being absorbed by the floor of the building.

[0003] As a reflector, one that reflects radio waves by specular reflection is known. Specular reflection refers to reflection in which the incident angle and the reflection angle are equal with respect to the reflecting surface. Such a reflector that reflects by specular reflection must adjust the mounting angle of the reflector to the wall, etc. according to the reflection direction in order to reflect radio waves into a desired space. Therefore, in recent years, for example, as shown in Patent Document 2, a reflector that reflects radio waves by so-called diffuse reflection has been proposed. Diffuse reflection refers to reflection in which the incident angle and the reflection angle are different angles with respect to the reflecting surface.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in both specular and polarized reflectors, while the radio wave intensity is high in the designed reflection direction, the reflection intensity is low in other directions, resulting in spaces where radio waves do not reach, so-called "blind spots." This invention has been made in view of the above problem, and aims to provide a radio wave reflector that can deliver radio waves to a wide area. [Means for solving the problem]

[0006] To achieve the above objectives, the present invention encompasses the subject matter described in the following sections.

[0007] Item 1: A radio wave reflector comprising a base layer, a plurality of reflective elements provided on the surface of the base layer, and a conductive layer provided on the back surface of the base layer, which reflects radio waves of wavelength λ, The reflective elements are arranged in a plan view in a first direction and a second direction perpendicular to the first direction. The substrate layer is divided into n regions Ak (k=1 to n, where n is 2 or more, and k indicates the order in which the regions are arranged along the first direction), Within each of the aforementioned regions Ak, a plurality of reflective elements of different shapes or sizes are periodically arranged along the first direction, and each period is divided into one or more sections. Pk is the length of the section of each region Ak along the first direction. Let Lk be the length of each region Ak along the first direction. Lmax is the value of Lk that is the maximum among the n Lk values ​​(k=1 to n) mentioned above. Let Ls be the sum of the n Lk values. When G1 is the set of regions Ak that satisfy the following condition 1, and G2 is the set of regions Ak that do not belong to set G1, A radio wave reflector that satisfies the following conditions 2 and 3. (Condition 1) 0.35≦Lk / Lmax≦1 (Condition 2) (Sum of lengths Lk of the region Ak belonging to set G2 LG2) / Ls ≤ 0.35 (Condition 3) In each region Ak belonging to the set G1, Pk ≥ λ / 2, and for all other regions Ak' (k' ≠ k, and 1 ≤ k' ≤ n) belonging to the set G1, Pk ≠ Pk'.

[0008] Item 2: The radio wave reflector described in Item 1, which satisfies the following condition 4 in all of the aforementioned regions Ak. (Condition 4) 0.5≦Lk / Lmax≦1

[0009] Item 3: The radio wave reflector according to Item 1, wherein the length Pk of the section in each of the regions Ak satisfies the following condition 5. (Condition 5)Pk <Pk+1(k=1~(n-1))

[0010] Item 4: The radio wave reflector described in Item 1, which satisfies the following condition 6, when Pmax is the maximum value of the length Pk of the section in each region Ak, and λ is the wavelength of the radio wave reflected by the radio wave reflector. (Condition 6) Pmax-Pk≦1.9λ

[0011] Item 5: A radio wave reflector comprising a base layer, a plurality of reflective elements provided on the surface of the base layer, and a conductive layer provided on the back surface of the base layer, which reflects radio waves of wavelength λ, The reflective elements are arranged in a first direction and a second direction perpendicular to the first direction, and are divided into n regions Ak (k=1 to n, where n is 2 or more, and k indicates the order in which the regions are arranged along the first direction) along the first direction. Within each of the aforementioned regions Ak, a plurality of reflective elements with different reflection phases are periodically arranged along the first direction, and each period is divided into one or more sections. Pk is the length of the section of each region Ak along the first direction. Let Lk be the length of each region Ak along the first direction. Lmax is the value of Lk that is the maximum among the n Lk values ​​(k=1 to n) mentioned above. Let Ls be the sum of the n Lk values. Of the aforementioned regions Ak, the set of regions Ak that satisfy the following condition 11 is G1, and the set of regions Ak that do not belong to set G1 is G2. A radio wave reflector that satisfies the following conditions 12 and 13 when [conditions are met]. (Condition 11) 0.35 ≦ Lk / Lmax ≦ 1 (Condition 12) (Sum LG2 of the lengths Lk of the regions Ak belonging to the set G2) / Ls ≦ 0.35 (Condition 13) In each region Ak belonging to the set G1, Pk ≧ λ / 2, and for all other regions Ak’ (k’ ≠ k and 1 ≦ k’ ≦ n) belonging to the set G1, Pk ≠ Pk’.

[0012] Item 6: The radio wave reflector according to item 5, which satisfies the following condition 14 in all of the regions Ak. (Condition 14) 0.5 ≦ Lk / Lmax ≦ 1

[0013] Item 7: The radio wave reflector according to item 5, wherein the length Pk of the partition of each region Ak satisfies the following condition 15. (Condition 15) Pk < Pk+1 (k = 1 to (n - 1))

[0014] Item 8: The radio wave reflector according to item 5, which satisfies the following condition 16 when the maximum value of the length Pk of the partition of each region Ak is Pmax and the wavelength of the radio wave reflected by the radio wave reflector is λ. (Condition 16) Pmax - Pk ≦ 1.9λ

Advantages of the Invention

[0015] According to the present invention, a radio wave reflector that can reach radio waves to a wide range of space can be provided.

Brief Description of the Drawings

[0016] [Figure 1] It is a plan view showing the overall schematic configuration of a radio wave reflector according to an embodiment of the present invention. [Figure 2] It is a figure showing the evaluation test results of Example 1 and Comparative Example 1. [Figure 3] It is a figure showing the evaluation test results of Example 2 and Comparative Example 2. [Figure 4] It is a figure showing the evaluation test results of Example 3 and Comparative Example 3. [Figure 5]This figure shows the evaluation test results for Example 4. [Modes for carrying out the invention]

[0017] Embodiments of the present invention will be described with reference to the drawings. Note that the drawings are used for illustrative purposes and do not represent actual scale. Furthermore, the dashed lines in the drawings are imaginary lines indicating the areas and sections described below, and are not lines drawn on the actual radio wave reflector 11.

[0018] The radio wave reflector 11 of this embodiment comprises a base layer 13 and a plurality of reflective elements 20, and reflects radio waves of wavelength λ. The base layer 13 is rectangular in plan view. The reflective elements 20 are provided on the surface of the base layer 13, and each reflective element 20 is a square-shaped conductor in plan view, as shown in the example in Figure 1. The reflective elements 20 are arranged along a first direction (also called the "X direction") and a second direction (also called the "Y direction") perpendicular to the X direction. Although not shown in Figure 1, the base layer 13 has a conductive layer on its back surface (the surface opposite to the surface on which the reflective elements 20 are formed).

[0019] The substrate layer 13 is divided into n regions Ak along the X direction (k=1 to n, where n is 2 or greater, and k indicates the order in which the regions are arranged along the X direction). In the example in Figure 1, n=2, and there are two regions A1 and A2 along the X direction, and the regions Ak are arranged from left to right in Figure 1 such that the number k, which indicates the order, increases. Note that it is not necessary to divide the entire surface of the substrate layer 13 into the regions Ak; for example, the peripheral part of the substrate layer 13 may not belong to the regions Ak, while the central part is divided into regions Ak.

[0020] Within each region A1 and A2, multiple reflective elements 20 of different shapes or sizes are periodically arranged along the X direction. Each period of this arrangement is divided into one or more sections B (B11-B15, B21-B24). In this embodiment, region A1 is divided into five sections B11-B15, and region A2 is divided into four sections B21-B24. In the example in Figure 1, the shape of each reflective element 20 belonging to each section B is the same in plan view and is a square, but their sizes are different. For example, each section B11-B15 in region A1 contains four square reflective elements 20 with different side lengths along the X direction, and each section B21-B24 in region A2 contains five square reflective elements 20 with different side lengths.

[0021] In the example in Figure 1, the reflective elements 20 in each section B are of different sizes, but their shapes may also be different, or both their shapes and sizes may be different. The shape and size of the conductor constituting each reflective element 20 are appropriately selected according to the frequency and intensity of the reflected radio waves. For example, the planar shape may be rectangular, circular, elliptical, triangular, polygonal, etc., or it may be annular, that is, composed of a conductor and a region without a conductor surrounded by the conductor.

[0022] In the example shown in Figure 1, reflective elements 20 of the same shape and size are arranged in each row along the Y direction.

[0023] Let Pk (also called "length Pk of section B") be the length of section B in each region Ak along the X direction. That is, the length Pk of section B indicates the period in which the reflecting elements 20 are arranged within region Ak, and the lengths P1 along the X direction of sections B11 to B15 in region A1 are the same, and the lengths P2 along the X direction of sections B21 to B14 in region A2 are the same.

[0024] Let Lk (also called "Length Lk of region Ak") be the length of each region Ak along the X direction. In the example in Figure 1, the length of region A1 is L1 and the length of region A2 is L2.

[0025] Let Lmax be the value of Lk that is the largest among n values ​​of Lk (k=1 to n). In the example in Figure 1, of the lengths L1 and L2 of regions A1 and A2, the length of L2 is the longest, so Lmax = L2.

[0026] Let Ls be the sum of n lengths Lk (k=1 to n). That is, Ls = ΣLk (k=1 to n). In the example in Figure 1, the sum of lengths L1 and L2 of regions A1 and A2 is Ls = L1 + L2.

[0027] Let G1 be the set of regions Ak that satisfy condition 1, and G2 be the set of regions Ak that do not belong to set G1. (Condition 1) 0.35≦Lk / Lmax≦1

[0028] In other words, for regions Ak belonging to set G1, the ratio of the length Lk of each region Ak to Lmax (Lk / Lmax) is in the range of 0.35 or more and 1 or less, and for regions Ak belonging to set G2, Lk / Lmax is less than 0.35. Region Ak belongs to either set G1 or G2. In the example in Figure 1, the length L1 of region A1 is 0.95 mm, and the length L2 (i.e., Lmax) of region A2 is 1.00 mm, so L1 / Lmax is 0.95 and L2 / Lmax is 1, and regions A1 and A2 belong to set G1, and there are no regions belonging to set G2.

[0029] At this time, the radio wave reflector 11 satisfies the following conditions 2 and 3. (Condition 2) (Sum of the lengths Lk of the regions Ak belonging to set G2 LG2) / (Total sum of the lengths Lk of the regions Ak Ls) ≤ 0.35 (Condition 3) In each region Ak belonging to the set G1, Pk ≥ λ / 2, and for all other regions Ak' (k' ≠ k, and 1 ≤ k' ≤ n) belonging to the set G1, Pk ≠ Pk'.

[0030] LG2 and Ls in condition 2 can also be expressed as follows. The sum of the lengths Lk of the regions Ak belonging to the set G2 is LG2 = Σ[Ak∈G2]Lk The sum of the lengths Lk of the regions Ak is Ls = Σ[Ak∈G1+G2]Lk Furthermore, condition 2 can also be expressed as follows: (Sum of the lengths Lk of the regions Ak belonging to set G1 LG1) / (Sum of the lengths Lk of the regions Ak Ls) > 0.65

[0031] Condition 3, "For all other regions Ak' (k'≠k, and 1≦k'≦n) belonging to set G1, Pk≠Pk'", can be expressed as follows: Pk≠Pk'(k'=1~n, k=1~n, k≠k', Ak∈G1, Ak'∈G1) In other words, condition 3 states that in the region Ak belonging to set G1, the lengths Pk (periods Pk) of each section B are different, and Pk will never be the same length. In the example in Figure 1, P1 and P2 are different.

[0032] Preferably, the radio wave reflector 11 satisfies condition 4 in all regions Ak. (Condition 4) 0.5≦Lk / Lmax≦1 In the example in Figure 1, both L1 and L2 satisfy condition 4.

[0033] Preferably, the radio wave reflector 11 satisfies condition 5, where the length Pk of each region Ak section satisfies condition 5. (Condition 5)Pk <Pk+1(k=1~(n-1)) In other words, in adjacent regions Ak, the length Pk of the partition in the region Ak that appears earlier in the sequence along the X direction (the one with the smaller k) is set to be shorter than the length Pk of the partition in the next region Ak. To put it another way, as the sequence of regions Ak progresses, the length Pk of the partitions in each region Ak increases. In the example in Figure 1, the length P1 of the partition in region A1, which appears earlier in the sequence, is shorter than the length P2 of the partition in region A2, which appears after region A1.

[0034] Preferably, condition 6 is satisfied when Pmax is the maximum length Pk of each region Ak and λ is the wavelength of the radio waves reflected by the radio wave reflector 11. (Condition 6) Pmax-Pk≦1.9λ

[0035] The radio wave reflector 11 reflects electromagnetic waves with an incident wave frequency of 2 GHz or higher and 300 GHz or lower, and its wavelength λ is 1 mm or higher and 150 mm or lower.

[0036] The thickness (film thickness) of the reflective element 20 is preferably 5 nm or more, and preferably 0.05 μm or more and 10 μm or less. The thickness is set appropriately from the viewpoint of ensuring appropriate radio wave intensity and visible light transmittance.

[0037] The reflective element 20 is preferably made of silver, for example. However, the reflective element 20 of the first conductive layer 16 may be made of any metal, metal compound, or alloy having free electrons, and is not limited to silver. For example, one or more selected from the group consisting of gold, copper, platinum, aluminum, titanium, silicon, indium tin oxide, and alloys (for example, alloys containing nickel, chromium, and molybdenum). Examples of alloys containing nickel, chromium, and molybdenum include various grades such as Hastelloy B-2, B-3, C-4, C-2000, C-22, C-276, G-30, N, W, and X.

[0038] One method for manufacturing the reflective element 20 is to form a conductive film, then create a pattern by etching, and then remove the conductive thin film having the pattern. Another method involves coating a base film with a lift-off layer with a photosensitive resist, forming a pattern by photolithography, filling the patterned area with a conductor, and then removing the conductive thin film having the pattern. The manufacturing method is not limited to the above, and other methods for forming the reflective element 20 include bonding a metal thin film and depositing metal.

[0039] The base layer 13 has a reflective element 20 formed on its upper surface and is a sheet-like component. "Sheet" refers to a shape in which the thickness of the object is 10% or less of the maximum length between the outer edges in a plan view. In this specification, films, foils, etc. are also included in "sheet".

[0040] The base layer 13 is made from materials such as PET (polyethylene terephthalate), FR4 (glass fiber cloth impregnated with epoxy resin and heat-cured to form a sheet), glass, or silicone. Other synthetic resins may also be used as materials. Examples of synthetic resins include one or more selected from the group consisting of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polymethyl methacrylate, polyester, polyformaldehyde, polyamide, polyphenylene ether, vinylidene chloride, polyvinyl acetate, polyvinyl acetal, AS resin, ABS resin, acrylic resin, fluororesin, nylon resin, polyacetal resin, polycarbonate resin, polyamide resin, and polyurethane resin.

[0041] The base layer 13 is formed in a rectangular shape when viewed from above. However, it is not limited to this, and may be rectangular, circular, elliptical, sector-shaped, polygonal, three-dimensional, etc., and is appropriately set according to the conditions of the building or wall on which the radio wave reflector 11 is installed. The thickness of the base layer 13 is appropriately set according to the wavelength λ. For example, if λ = 10 mm, it is set to 0.1 mm to 1 mm.

[0042] The conductive layer is formed on the back surface of the base layer 13 (the surface opposite to the surface on which the reflective element 20 is formed) and is laminated with the base layer 13. The shape of the conductive layer is not particularly limited, but for example, it can be a layer with the same shape as the base layer 13. The conductive layer may contain a conductor made of a metal with free electrons, such as copper, silver, gold, platinum, aluminum, titanium, or silicon. The conductive layer may also contain any synthetic resin or other material in addition to the conductor. The thickness (film thickness) of the conductive layer is not particularly limited and may be 50 nm or more, 100 nm or more, 200 nm or more, 500 nm or more, or 700 nm or more. The thickness (film thickness) of the conductive layer may also be 10 μm or less, 5 μm or less, 3 μm or less, or 2 μm or less.

[0043] Furthermore, in order to protect the reflective element 20, the reflector 20 may have a protective layer to protect it and an adhesive layer to bond the reflective element 20 to the protective layer. In this case, the radio wave reflector 11 is laminated in the order of base layer 13, reflective element 20, adhesive layer, and protective layer. The material of the protective layer may be the same as that of the base layer 13.

[0044] The above-mentioned radio wave reflector 11 is in sheet form, and its thickness is preferably set to 1 mm or less. The thickness of the radio wave reflector 11 is set such that the radio wave reflector 11 can be flexible and that when an external force is applied to the radio wave reflector 11 and the radio wave reflector 11 is bent, the force does not concentrate on the conductor. Note that since the thickness of the reflective element 20 is very thin compared to the base material layer 13, the thickness of the reflective element 20 may be ignored when setting the thickness of the radio wave reflector 11.

[0045] The shape of the radio wave reflector 11 in a plan view is the same as the shape of the base material layer 13. Radio waves with frequencies between 2 GHz and 300 GHz are attenuated with distance, but it is preferable that the reflector be large enough to reflect with sufficient intensity at all points within a practical distance from the radio wave source.

[0046] (modified version) Within each region A1 and A2, multiple reflective elements 20 with different reflection phases may be periodically arranged along the X direction. That is, the reflection phases of each reflective element 20 contained in each section B are different. The reflection phase refers to the difference between the phase of the incident wave incident on each reflective element 20 and the phase of the reflected wave reflected by each reflective element 20. The difference in the reflection phases of each reflective element 20 means that the degree of this phase difference is different for each reflective element 20. As long as the reflection phases of each reflective element 20 contained in each section B are different, the shape and size of the reflective elements 20 may all be different along the X direction, or they may be the same. Other configurations are the same as in the embodiment of Figure 1, so their explanation is omitted. Also, in this embodiment, conditions 11 to 16 correspond to conditions 1 to 6 in the embodiment of Figure 1.

[0047] (Evaluation test) Examples 1 to 4 and Comparative Examples 1 to 3 (hereinafter also referred to as "samples") were prepared as radio wave control bodies 11, and evaluation tests regarding radio wave reflection were conducted. However, the radio wave control body 11 of the present invention is not limited to Examples 1 to 4. Each of the radio wave reflectors 11 of the samples was prepared according to the parameters shown in Tables 1 to 7.

[0048] The following points apply to Examples 1-4 and Comparative Examples 1-3. Total thickness of the radio wave control unit 11: 202 μm Thickness of reflective element 20: 1 μm Material of reflective element 20: Copper Thickness of substrate layer 13: 200 μm Material of base layer 13: PET Arrangement of reflective elements: Multiple reflective elements of different shapes or sizes are arranged periodically along the X direction. The size of each reflective element in the X direction is 3.4 to 5.1 mm.

[0049] For the sample, a far-field analysis was performed using an electromagnetic field simulator (Ansys HFSS) to analyze the reflection profile when radio waves were irradiated onto the sample's radio wave reflector 11 at predetermined incidence angles shown in Tables 1 to 7. The sample was designed so that the reflection intensity was greatest at the predetermined reflection angles shown in Tables 1 to 7. The radio waves had a wavelength λ of 10.7 mm and a frequency of 28 GHz, and the maximum reflection intensity of the reflected wave was estimated to be 0 dB.

[0050] Figures 2 to 5 show the simulation results of the reflection intensity for each sample in the direction of radio wave reflection. Furthermore, the full width at half maximum (FWHM) of the reflected wave incident on each sample was calculated and evaluated according to the following criteria. The results are shown in Table 8. Half-width of 15 degrees or more: ◎ Half-width is 7.5 degrees or more, but less than 15 degrees: ○ Half-width less than 7.5 degrees: ×

[0051] In Examples 1-4, it was confirmed that the half-width was larger compared to Comparative Example 1-3, and that radio waves could be reflected over a wider area.

[0052] Table 1

[0053] Table 2

[0054] Table 3

[0055] Table 4

[0056] Table 5

[0057] Table 6

[0058] Table 7-1

[0059] Table 7-2

[0060] Table 8

[0061] Note that the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples. Expressions indicating that things such as "in a certain direction", "along a certain direction", "the same", "identical", "equal", and "homogeneous" are in an equal state not only represent a strictly equal state, but also represent a state in which there are tolerances or differences within a range that can achieve the same function. Expressions representing triangular, square, or circular shapes not only represent shapes in a strictly geometric sense, but also represent shapes including concave and convex portions, chamfered portions, etc. within a range that can achieve the same effect. The expressions "comprising", "having", "including", or "possessing" one component are not exclusive expressions that exclude the existence of other components. "Parallel" and "orthogonal" mean substantially "parallel" and "orthogonal", and include not only a strictly "parallel" and "orthogonal" state, but also a meaning including an error of about several degrees. In addition, there may be cases where an expression such as "... part" is used, for example, "end part". For example, the "end part" means a part having a certain range including the "end". The same applies to other expressions with "... part".

Explanation of Reference Numerals

[0062] 11 Radio wave reflector 13 Base material layer 20 Reflective element Ak(A1,A2) Region B(B11~B15,B21~B24) Compartment Pk(P1,P2) Length of the compartment of region Ak along the first direction Lk(L1, L2) Length of each region Ak along the first direction Lmax Value of Lk that is the maximum among n Lk Ls Sum of n Lk G1 Set of region Ak that satisfies condition 1 G2 Set of the region Ak that does not belong to set G1 X direction (first direction) Y direction (second direction)

Claims

1. A radio wave reflector comprising a base layer, a plurality of reflective elements provided on the surface of the base layer, and a conductive layer provided on the back surface of the base layer, which reflects radio waves of wavelength λ, The reflective elements are arranged in a plan view in a first direction and a second direction perpendicular to the first direction. The substrate layer is divided into n regions Ak (k = 1 to n, where n is 2 or more, and k indicates the order in which the regions are arranged along the first direction), Within each of the aforementioned regions Ak, a plurality of reflective elements of different shapes or sizes are arranged periodically along the first direction, and each region is divided into one or more sections for each period. Pk is the length of the section of each region Ak along the first direction. The length of each region Ak along the first direction is Lk, Lmax is the value of Lk that is the largest among the n Lk values ​​(k=1 to n) mentioned above. Let Ls be the sum of the n Lk values. When G1 is the set of regions Ak that satisfy the following condition 1, and G2 is the set of regions Ak that do not belong to set G1, A radio wave reflector that satisfies the following conditions 2 and 3. (Condition 1) 0.35≦Lk / Lmax≦1 (Condition 2) (Sum of lengths Lk of the region Ak belonging to set G2 LG2) / Ls ≤ 0.35 (Condition 3) In each region Ak belonging to the set G1, Pk ≥ λ / 2, and for all other regions Ak' belonging to the set G1 (k' ≠ k, and 1 ≤ k' ≤ n), Pk ≠ Pk'.

2. The radio wave reflector according to claim 1, wherein all of the aforementioned regions Ak satisfy the following condition 4. (Condition 4) 0.5≦Lk / Lmax≦1

3. The radio wave reflector according to claim 1, wherein the length Pk of the section in each of the aforementioned regions Ak satisfies the following condition 5. (Condition 5) Pk<Pk+1 (k=1~(n-1))

4. The radio wave reflector according to claim 1, wherein the following condition 6 is satisfied when the maximum value of the length Pk of the section in each of the regions Ak is Pmax and the wavelength of the radio wave reflected by the radio wave reflector is λ. (Condition 6) Pmax-Pk≦1.9λ

5. A radio wave reflector comprising a base layer, a plurality of reflective elements provided on the surface of the base layer, and a conductive layer provided on the back surface of the base layer, which reflects radio waves of wavelength λ, The reflective elements are arranged in a first direction and a second direction perpendicular to the first direction, and are divided into n regions Ak (k = 1 to n, n is 2 or more, k indicates the order in which the regions are arranged along the first direction) along the first direction. Within each of the aforementioned regions Ak, a plurality of reflective elements with different reflection phases are periodically arranged along the first direction, and each period is divided into one or more sections. Pk is the length of the section of each region Ak along the first direction. The length of each region Ak along the first direction is Lk, Lmax is the value of Lk that is the largest among the n Lk values ​​(k=1 to n) mentioned above. Let Ls be the sum of the n Lk values, G1 be the set of regions Ak that satisfy the following condition 11, and G2 be the set of regions Ak that do not belong to set G1. In this case, a radio wave reflector that satisfies the following conditions 12 and 13. (Condition 11) 0.35≦Lk / Lmax≦1 (Condition 12) (Sum of lengths Lk of the region Ak belonging to set G2 LG2) / Ls ≤ 0.35 (Condition 13) In each region Ak belonging to the set G1, Pk ≥ λ / 2, and for all other regions Ak' belonging to the set G1 (k' ≠ k, and 1 ≤ k' ≤ n), Pk ≠ Pk'.

6. The radio wave reflector according to claim 5, wherein the following condition 14 is satisfied in all of the aforementioned regions Ak. (Condition 14) 0.5≦Lk / Lmax≦1

7. The radio wave reflector according to claim 5, wherein the length Pk of the section in each of the aforementioned regions Ak satisfies the following condition 15. (Condition 15) Pk<Pk+1 (k=1~(n-1))

8. The radio wave reflector according to claim 5, wherein the following condition 16 is satisfied when the maximum value of the length Pk of the section in each of the regions Ak is Pmax and the wavelength of the radio wave reflected by the radio wave reflector is λ. (Condition 16) Pmax-Pk≦1.9λ

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