Manufacturing method of selective radio wave reflection sheet

Abstract

To provide a manufacturing method of an FSS radio wave reflection sheet in which antenna elements having a simple shape are evenly arranged and a frequency and a bandwidth can be easily designed only by changing an arrangement interval of the antenna elements.SOLUTION: A manufacturing method of a selective radio wave reflection sheet includes: a step of determining an interval in a magnetic field amplitude direction of an incident radio wave of an antenna patch or an interval in an electric field amplitude direction of an incident radio wave of an antenna slot while referring to a specific line format, to satisfy it; and a step of manufacturing the selective radio wave reflection sheet in which the antenna patches or antenna slots are evenly arranged on a dielectric sheet or a conductive sheet at the determined intervals.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a selective radio wave reflection sheet.

Background Art

[0002] In recent years, with the spread of IoT, various wireless communication systems such as wireless LAN, Bluetooth (registered trademark), and Sub6 in the frequency band of 6 GHz or less have been introduced. Along with this, radio waves in the frequency band of 2 to 6 GHz are crowded in narrow spaces such as factories, offices, and houses.

[0003] Along with this, radio waves generated from various electronic devices have become a problem in that they have an adverse effect on the human body or cause malfunction of surrounding electronic devices. In addition, there are concerns about security risks such as eavesdropping and unauthorized access to wireless LAN communication data.

[0004] Against such a background, there is a demand for shielding radio waves of wireless LAN from penetrating through building walls and allowing necessary radio waves such as those of mobile phones to penetrate. Therefore, it is required to selectively shield only radio waves in a specific frequency band and allow radio waves outside the specific frequency band to pass through.

[0005] Conventionally, as a technique for selectively blocking or transmitting radio waves in a specific frequency band, a radio wave reflection sheet using a frequency selective surface (FSS) has been proposed (Patent Documents 1 and 2).

[0006] In the FSS radio wave reflection sheet, an FSS radio wave reflection sheet having a structure of an element pattern combining a plurality of types of shapes such as a Y shape and an Elsalam cross shape has been proposed. However, a complex structure with many element patterns is required to exhibit desired characteristics.

[0007] The design of FSS radio wave reflection sheets is generally carried out using electromagnetic field analysis methods such as the moment method, the finite-difference time-domain method (FDTD), and the finite element method (FEM). However, the analysis software is expensive, and equipment such as a personal computer with corresponding specifications is required. In addition, knowledge and experience are required for condition settings and the like in the analysis of complex shapes. Furthermore, the more complex the shape, the more time-consuming the analysis. Therefore, if the analysis is performed multiple times with different conditions, there is a concern that the design and development will be delayed. The places of use are various, such as factories, offices, and houses, and it is difficult to appropriately change the design according to each environment.

[0008] In Patent Document 3, as an electromagnetic wave shielding material that can easily change the resonance frequency and aims to selectively and accurately shield electromagnetic waves of a specific frequency, it is proposed to arrange a plurality of conductive patterns having a total circumference L that forms a closed loop and satisfies a specific formula on the surface of a dielectric substrate.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0010] However, only the frequency design is considered, and the bandwidth is not considered. Since radio waves are defined not only by frequency but also by bandwidth depending on the application, it is also important to consider the bandwidth. Conventionally, no technology that considers both frequency and bandwidth and enables easy design of these has been proposed. The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing an FSS radio wave reflection sheet in which antenna elements having a simple shape are evenly arranged and the frequency and bandwidth can be easily designed only by changing the arrangement interval.

Means for Solving the Problems

[0011] As a result of intensive studies to solve the above problems, the present inventor has found that by arranging slots or patches according to a specific mathematical formula, the peak frequency and bandwidth of transmission or reflection characteristics can be controlled, and the present invention has been completed. That is, the present invention is characterized by the following. [1] A method for manufacturing a radio wave reflection sheet that selectively reflects radio waves of a target frequency in the vicinity of a frequency F (GHz) and a wavelength λ (mm), a step of determining the interval in the magnetic field amplitude direction of the incident radio wave of an annular antenna patch having a peripheral length of 1λ mm or a linear antenna patch having an element length of 1 / 2λ mm with reference to the following formulas (1) and (2) so as to satisfy this; and a step of manufacturing a selective radio wave reflection sheet in which the annular antenna patch or the linear antenna patch is evenly arranged on a dielectric sheet at the determined interval.

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Advantages of the Invention

[0012] According to the present invention, by arranging simple-shaped antenna elements evenly and simply changing the arrangement interval, the frequency and bandwidth can be easily designed.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Best Mode for Carrying Out the Invention

[0014] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In this specification, selectively reflecting or transmitting radio waves of a target frequency in the vicinity of a frequency F (GHz) and a wavelength λ (mm) means that, as the reflection peak frequencies y1 and y3 and the transmission peak frequencies y4 and y6 are normalized by the frequency F (GHz), the range of the normalized reflection peak frequencies y1 and y3 and the transmission peak frequencies y4 and y6 before and after the frequency F (GHz) is referred to. In other words, when determining the element interval based on the radio waves that are originally desired to be reflected or transmitted in the vicinity of the frequency F (GHz) and the wavelength λ (mm) which are the main reference of the target radio wave range, it means selectively reflecting or transmitting radio waves of that frequency within the range derived from a straight line in which the frequency and bandwidth change depending on the element interval. (Embodiment 1) FIGS. 1A to 1F are plan views showing a part of a radio wave reflection sheet manufactured in this embodiment, and showing shape examples of an annular antenna patch and a linear antenna patch. The annular antenna patch 1A or the linear antenna patch 1B is evenly arranged on the dielectric sheet 2A at a predetermined interval. The manufacturing method of the radio wave reflection sheet in this embodiment is a manufacturing method of a radio wave reflection sheet that selectively reflects radio waves of a target frequency in the vicinity of a frequency F (GHz). The manufacturing method of the radio wave reflection sheet in this embodiment includes the following steps (A1) and (B1). (A1) A step of determining, with reference to the formulas (1) and (2), the interval in the magnetic field amplitude direction of the incident radio waves of an annular antenna patch having a peripheral length of 1λ mm or a linear antenna patch having an element length of 1 / 2λ mm so as to satisfy this; and (B1) A step of manufacturing a selective radio wave reflection sheet in which the annular antenna patch or the linear antenna patch is evenly arranged on a dielectric sheet at the determined interval

[0015] The frequency F (GHz) serving as a reference for the radio waves to be selectively reflected is not particularly limited, but is preferably 1 to 100 GHz, more preferably 1 to 80 GHz, and even more preferably 2 to 60 GHz.

[0016] In step (A1), a circular antenna patch or a linear antenna patch is used. Examples of the circular antenna patch include the shapes shown in FIGS. 1A to 1C, and are not particularly limited. For example, a square (FIG. 1A), a circle (FIG. 1B), a triangle (FIG. 1C), etc. may be mentioned.

[0017] The circular antenna patch has a perimeter length of 1λ mm. Here, 1λ mm includes a range equivalent in view of common general knowledge from the perspective of antenna efficiency that resonates at a specific frequency and as a result acts as a reflection filter for a specific band, and is not necessarily limited to exactly 1λ mm, and is understood as a range having a width centered around 1λ mm.

[0018] In step (A1), examples of the linear antenna patch include the shapes shown in FIGS. 1D to 1F, and are not particularly limited. For example, a straight line (FIG. 1D), a cross shape (FIG. 1E), an inverted Y shape (FIG. 1F), etc. may be mentioned.

[0019] The linear antenna patch has an element length of 1 / 2λ mm. Here, 1 / 2λ mm includes a range equivalent in view of common general knowledge from the perspective of antenna efficiency that resonates at a specific frequency and as a result acts as a reflection filter for a specific band, and is not necessarily limited to exactly 1 / 2λ mm, and is understood as a range having a width centered around 1 / 2λ mm.

[0020] In step (A1), the interval in the magnetic field amplitude direction of the incident radio waves of the circular antenna patch or the linear antenna patch is determined with reference to the above formulas (1) and (2) so as to satisfy this. In formula (1), x represents the interval in the magnetic field amplitude direction of the incident radio waves of the antenna patch, and y1 represents the reflection peak frequency. The interval x between the antenna patches is normalized as λ mm, and the reflection peak frequency y1 is normalized as F (GHz).

[0021] The interval x in the magnetic field amplitude direction of the incident radio wave on the antenna patch satisfies 0.1 < x < 0.7, and preferably 0.12 < x < 0.55. Within this range, a reflection peak with an appropriate intensity for reflecting the target radio wave can be obtained.

[0022] The reflection peak frequency y1 satisfies 0.45 < y1 < 1.27, and preferably 0.50 < y1 < 1.14. When within this range, it will not deviate significantly from the reference frequency F (GHz) of the radio wave to be selectively reflected.

[0023] In Equation (1), a is a number that satisfies -0.75 < a < -0.15, preferably -0.6 < a < -0.2, and more preferably -0.5 < a < -0.3. b is a number that satisfies 0.97 < b < 1.29, preferably 0.98 < b < 1.25, and more preferably 1.05 < b < 1.20.

[0024] In Equation (2), x represents the interval in the magnetic field amplitude direction of the incident radio wave on the antenna patch, and y2 represents the bandwidth at -10 dB of the reflection peak. The interval x between the antenna patches is normalized as λ mm, and the bandwidth y2 is normalized as F (GHz).

[0025] The bandwidth y2 at -10 dB of the reflection peak satisfies 0 < y2 < 0.29 from the perspective of frequency selection performance, and preferably 0.03 < y2 < 0.26.

[0026] In Equation (2), c is a number that satisfies -0.44 < c < -0.13, preferably -0.40 < c < -0.16, and more preferably -0.35 < c < -0.20. d is a number that satisfies 0.08 < d < 0.31, preferably 0.10 < d < 0.28, and more preferably 0.12 < d < 0.25.

[0027] The interval between the magnetic field amplitude directions of the incident radio waves of the circular antenna patch or the linear antenna patch is determined with reference to Expressions (1) and (2) so as to satisfy this condition. Within the range of the interval x between the antenna patches, both the frequency and the bandwidth change. Therefore, the frequency and the bandwidth can be designed according to the purpose of selectively shielding only the radio waves in a specific frequency band and transmitting the radio waves outside the specific frequency band, and applications where not only the frequency but also the bandwidth is defined.

[0028] The method for manufacturing the radio wave reflection sheet in the present embodiment may further include the following step (A1-1). Step (A1-1): Prepare a selective radio wave reflection sheet with the interval between the antenna patches changed, measure the reflection frequency characteristics, and obtain the straight lines of Expressions (1) and (2).

[0029] In this step (A1-1), Expressions (1) and (2) for designing the frequency and the bandwidth can be obtained. The number of selective radio wave reflection sheets to be prepared is not particularly limited. For example, within the range of the interval x between the antenna patches in Expressions (1) and (2), several points are prepared and the reflection frequency characteristics are measured, and then Expressions (1) and (2) can be obtained from the straight line derived from those several points. After performing steps (A1) and (B1) thereafter, it is possible to easily design the frequency and the bandwidth by evenly arranging simple-shaped antenna elements and only changing the array interval. The method for obtaining the straight line is not particularly limited, and a conventionally known method can be used. For example, a straight line passing through two points may be used, or a statistical analysis method such as the least squares method can be used.

[0030] In the present embodiment, in step (B1), a selective radio wave reflection sheet is manufactured by evenly arranging the circular antenna patch or the linear antenna patch on the dielectric sheet at the determined interval.

[0031] Here, the uniform array is intended to be arranged uniformly in the direction of the magnetic field amplitude of the incident radio wave, and it is not necessarily required that the interval W1 in the direction of the magnetic field amplitude of the incident radio wave is the same as the interval W2 in the direction of the electric field amplitude of the incident radio wave orthogonal thereto. However, it is preferable that both the interval W1 and the interval W2 are within the range of the interval x between the antenna patches. In this way, based on the formulas (1) and (2), it is possible to easily design the frequency and the bandwidth simply by arranging the antenna elements of a simple shape uniformly and changing the array interval.

[0032] (Embodiment 2) FIGS. 1G to 1I are plan views showing a part of the radio wave reflection sheet manufactured in this embodiment, and show examples of the shapes of the planar antenna patches. The planar antenna patches 1C are arranged uniformly on the dielectric sheet 2A at a predetermined interval. The manufacturing method of the radio wave reflection sheet in this embodiment is a manufacturing method of a radio wave reflection sheet that selectively reflects radio waves of a target frequency in the vicinity of the frequency F (GHz). The manufacturing method of the radio wave reflection sheet in this embodiment includes the following steps (A2) and (B2). (A2) A step of determining, with reference to the formulas (3) and (2), the interval in the direction of the magnetic field amplitude of the incident radio wave of the planar antenna patch whose minimum value of the straight line passing through the center point is 1 / 2λ mm so as to satisfy this; and (B2) A step of manufacturing a selective radio wave reflection sheet in which the planar antenna patches are arranged uniformly on the dielectric sheet at the determined interval

[0033] The reference frequency F (GHz) of the radio wave to be selectively reflected is not particularly limited, but 1 to 100 GHz is preferable, 1 to 80 GHz is more preferable, and 2 to 60 GHz is even more preferable.

[0034] In step (A2), a planar antenna patch is used. Examples of the planar antenna patch include the shapes shown in FIGS. 1G to 1I, and are not particularly limited. For example, a square (FIG. 1G), a circle (FIG. 1H), a triangle (FIG. 1I), etc. can be mentioned.

[0035] The minimum value of the straight line passing through the center point of the planar antenna patch is 1 / 2λ mm. Here, 1 / 2λ mm includes a range equivalent in view of common technical knowledge from the perspective of antenna efficiency that resonates at a specific frequency and as a result acts as a reflection filter for a specific band, and is not necessarily limited to 1 / 2λ mm, but is understood as a range with a width centered around 1 / 2λ mm.

[0036] In step (A2), the interval in the magnetic field amplitude direction of the incident radio wave of the planar antenna patch is determined with reference to the above formulas (3) and (2) so as to satisfy this. In formula (3), x represents the interval in the magnetic field amplitude direction of the incident radio wave of the antenna patch, and y3 represents the reflection peak frequency. The interval x between the antenna patches is normalized as λ mm, and the reflection peak frequency y3 is normalized as F (GHz).

[0037] The interval x in the magnetic field amplitude direction of the incident radio wave of the antenna patch is 0.1 < x < 0.7, and 0.12 < x < 0.55 is preferable. Within this range, a reflection peak of appropriate intensity for reflecting the target radio wave can be obtained.

[0038] The reflection peak frequency y3 is 0.41 < y3 < 1.45, and 0.45 < y3 < 1.31 is preferable. When within this range, it will not deviate significantly from the frequency F (GHz) that serves as the standard for the radio wave to be selectively reflected.

[0039] In formula (3), e is a number satisfying -1.35 < e < -0.90, -1.30 < e < -0.95 is preferable, and -1.25 < e < -1.00 is more preferable. f is a number satisfying 1.35 < f < 1.55, 1.38 < f < 1.51 is preferable, and 1.43 < f < 1.48 is more preferable.

[0040] In formula (2), x represents the interval in the magnetic field amplitude direction of the incident radio wave of the antenna patch, and y2 represents the bandwidth at -10 dB of the reflection peak. The interval x between the antenna patches is normalized as λ mm, and the bandwidth y2 is normalized as F (GHz).

[0041] The bandwidth y2 at -10 dB of the reflection peak is 0 < y2 < 0.29 from the viewpoint of frequency selection performance, and preferably 0.03 < y2 < 0.26.

[0042] In formula (2), c is a number satisfying -0.44 < c < -0.13, preferably -0.40 < c < -0.16, and more preferably -0.35 < c < -0.20. d is a number satisfying 0.08 < d < 0.31, preferably 0.10 < d < 0.28, and more preferably 0.12 < d < 0.25.

[0043] The interval in the magnetic field amplitude direction of the incident radio wave of the planar antenna patch is determined with reference to formulas (3) and (2) so as to satisfy this. Within the range of the interval x between the antenna patches, both the frequency and the bandwidth change. Therefore, according to the purpose of selectively shielding only the radio waves in a specific frequency band and transmitting the radio waves outside the specific frequency band, and applications where not only the frequency but also the bandwidth is defined, the frequency and the bandwidth can be designed.

[0044] The method for manufacturing the radio wave reflection sheet in this embodiment may further include the following step (A2-1). Step (A2-1): Prepare a selective radio wave reflection sheet with the interval between the antenna patches changed and measure the reflection frequency characteristics to obtain the straight lines of formulas (3) and (2).

[0045] In this step (A2-1), equations (3) and (2) for designing the frequency and bandwidth can be obtained. The number of selective radio wave reflection sheets to be prepared is not particularly limited. For example, within the range of the interval x between the antenna patches in equations (3) and (2), several points are prepared and the reflection frequency characteristics are measured, and then equations (3) and (2) can be obtained from the straight line derived from those points. Subsequently, by performing steps (A2) and (B2), simple-shaped antenna elements are evenly arranged, and the frequency and bandwidth can be easily designed only by changing the arrangement interval. The method for obtaining the straight line is not particularly limited, and a conventionally known method can be used. For example, a straight line passing through two points may be used, or a statistical analysis method such as the least squares method can be used.

[0046] In this embodiment, in step (B2), the planar antenna patches are used to manufacture selective radio wave reflection sheets evenly arranged on a dielectric sheet at the determined interval.

[0047] Here, the even arrangement is intended to be an even arrangement in the magnetic field amplitude direction of the incident radio wave, and it is not necessarily required that the interval W1 in the magnetic field amplitude direction of the incident radio wave coincides with the interval W2 in the electric field amplitude direction of the incident radio wave orthogonal to it. However, it is preferable that both the interval W1 and the interval W2 are within the range of the interval x between the antenna patches. In this way, based on equations (1) and (2), simple-shaped antenna elements are evenly arranged, and the frequency and bandwidth can be easily designed only by changing the arrangement interval.

[0048] (Embodiment 3) Figures 2A to 2F are plan views showing a part of the radio wave reflection sheet manufactured in this embodiment, and show shape examples of a circular antenna slot and a linear antenna slot. The circular antenna slot 1D or the linear antenna slot 1E is evenly arranged on the conductive sheet 2B at a predetermined interval. The manufacturing method of the radio wave reflection sheet in this embodiment is a manufacturing method of a radio wave reflection sheet that selectively transmits radio waves of a target frequency in the vicinity of the frequency F (GHz). The manufacturing method of the radio wave reflection sheet in this embodiment includes the following steps (A3) and (B3). (A3) Referring to the formulas (4) and (5), determining the interval in the direction of the electric field amplitude of the incident radio wave of the circular antenna slot with a peripheral length of 1λ mm or the linear antenna slot with an element length of 1 / 2λ mm so as to satisfy this; and (B3) Manufacturing a selective radio wave reflection sheet in which the circular antenna slot or the linear antenna slot is evenly arranged on the conductive sheet at the determined interval

[0049] The reference frequency F (GHz) of the radio wave that selectively passes through is not particularly limited, but 1 to 100 GHz is preferable, 1 to 80 GHz is more preferable, and 2 to 60 GHz is even more preferable.

[0050] In step (A3), a circular antenna slot or a linear antenna slot is used. Examples of the circular antenna slot include shapes as shown in FIGS. 2A to 2C, and although not particularly limited, for example, a square (FIG. 2A), a circle (FIG. 2B), a triangle (FIG. 2C), etc. can be mentioned.

[0051] The circular antenna slot has a peripheral length of 1λ mm. Here, 1λ mm includes a range equivalent in view of common technical knowledge from the perspective of antenna efficiency that resonates at a specific frequency and as a result acts as a reflection filter for a specific band, and is not necessarily limited to 1λ mm, and is understood as a range having a width centered on 1λ mm.

[0052] In step (A3), examples of the linear antenna slot include shapes as shown in FIGS. 2D to 2F, and although not particularly limited, for example, a straight line (FIG. 2D), a cross shape (FIG. 2E), an inverted Y shape (FIG. 2F), etc. can be mentioned.

[0053] The linear antenna slot has an element length of 1 / 2λmm. Here, 1 / 2λmm encompasses a range equivalent from the perspective of common general knowledge in technology considering the antenna efficiency that resonates at a specific frequency and as a result acts as a reflection filter for a specific band, and is not necessarily limited to exactly 1 / 2λmm, but is understood as a range with a width centered around 1 / 2λmm.

[0054] In step (A3), the interval in the direction of the electric field amplitude of the incident radio wave of the circular antenna slot or the linear antenna slot is determined with reference to the above formulas (4) and (5) so as to satisfy this. In formula (4), x represents the interval in the direction of the electric field amplitude of the incident radio wave of the antenna slot, and y4 represents the transmission peak frequency. The interval x between the antenna slots is normalized as λmm, and the transmission peak frequency y4 is normalized as F(GHz).

[0055] The interval x in the direction of the electric field amplitude of the incident radio wave of the antenna slot is 0.45 < x < 1.1, and 0.5 < x < 0.8 is preferable. Within this range, a transmission peak with an intensity suitable for transmitting the target radio wave can be obtained.

[0056] The transmission peak frequency y4 is 0.54 < y4 < 1.13, and 0.59 < y4 < 1.02 is preferable. If it is within this range, it will not deviate significantly from the reference frequency F(GHz) of the radio wave to be selectively transmitted.

[0057] In formula (4), g is a number satisfying -0.38 < g < -0.10, -0.35 < g < -0.13 is preferable, and -0.32 < g < -0.15 is more preferable. h is a number satisfying 0.95 < h < 1.18, 0.97 < h < 1.13 is preferable, and 1.00 < h < 1.10 is more preferable.

[0058] In formula (5), x represents the interval in the direction of the electric field amplitude of the incident radio wave of the antenna slot, and y5 represents the bandwidth at -3dB from the transmission peak apex. The interval x between the antenna slots is normalized as λmm, and the bandwidth y5 is normalized as F(GHz).

[0059] The bandwidth y5 at -3 dB from the peak vertex is, from the viewpoint of frequency selection performance, 0 < y5 < 0.28, and preferably 0.03 < y5 < 0.25.

[0060] In formula (5), i is a number satisfying -0.21 < i < -0.02, preferably -0.15 < i < -0.025, and more preferably -0.09 < i < -0.03. j is a number satisfying 0.12 < j < 0.29, preferably 0.15 < j < 0.26, and more preferably 0.18 < j < 0.23.

[0061] The interval in the direction of the electric field amplitude of the incident radio wave of the circular antenna slot or the linear antenna slot is determined with reference to formulas (4) and (5) so as to satisfy this. Within the range of the interval x of the antenna slots, both the frequency and the bandwidth change. Therefore, the frequency and the bandwidth can be designed according to the purpose of selectively transmitting only the radio waves in a specific frequency band and reflecting the radio waves outside the specific frequency band, and applications where not only the frequency but also the bandwidth is defined.

[0062] The method for manufacturing the radio wave reflection sheet in this embodiment may further include the following step (A3-1). Step (A3-1): Prepare a selective radio wave reflection sheet with the interval of the antenna slots changed and measure the transmission frequency characteristics to obtain the straight lines of formulas (4) and (5).

[0063] In this step (A3-1), equations (4) and (5) for designing the frequency and bandwidth can be obtained. The number of selective radio wave reflection sheets to be prepared is not particularly limited. For example, within the range of the interval x between the antenna slots in equations (4) and (5), several points are prepared, and if the transmission frequency characteristics are measured, equations (4) and (5) can be obtained from the straight line derived from those points. Subsequently, by performing steps (A3) and (B3), simple-shaped antenna elements are evenly arranged, and the frequency and bandwidth can be easily designed only by changing the arrangement interval. The method for obtaining the straight line is not particularly limited, and a conventionally known method can be used. For example, a straight line passing through two points may be used, or a statistical analysis method such as the least squares method can be used.

[0064] In this embodiment, in step (B3), the planar antenna slots are used to manufacture selective radio wave reflection sheets evenly arranged on the conductive sheet at the determined intervals.

[0065] Here, the even arrangement is intended to be an even arrangement in the direction of the electric field amplitude of the incident radio wave, and it is not necessarily required that the interval W1 in the direction of the magnetic field amplitude of the incident radio wave and the interval W2 in the direction of the electric field amplitude of the incident radio wave orthogonal thereto are the same. However, it is preferable that both the interval W1 and the interval W2 are within the range of the interval x between the antenna slots. In this way, based on equations (4) and (5), simple-shaped antenna elements are evenly arranged, and the frequency and bandwidth can be easily designed only by changing the arrangement interval.

[0066] (Embodiment 4) Figs. 2G to 2I are plan views showing a part of the radio wave reflection sheet manufactured in this embodiment, and show examples of the shapes of the planar antenna slots. The planar antenna slots 1F are evenly arranged on the conductive sheet 2B at a predetermined interval. The manufacturing method of the radio wave reflection sheet in this embodiment is a method for manufacturing a radio wave reflection sheet that selectively transmits radio waves of a target frequency in the vicinity of the frequency F (GHz). The manufacturing method of the radio wave reflection sheet in this embodiment includes the following steps (A4) and (B4). (A4) Referring to the above formulas (6) and (5), determining the interval in the direction of the electric field amplitude of the incident radio wave of the planar antenna slot where the minimum value of the straight line passing through the center point is 1 / 2λ mm so as to satisfy this; and (B4) Manufacturing a selective radio wave reflection sheet in which the planar antenna slots are evenly arranged on the conductive sheet at the determined interval

[0067] The reference frequency F (GHz) of the radio wave that selectively passes through is not particularly limited, but 1 to 100 GHz is preferable, 1 to 80 GHz is more preferable, and 2 to 60 GHz is even more preferable.

[0068] In step (A4), a planar antenna slot is used. Examples of the planar antenna slot include shapes shown in FIGS. 2G to 2I, and although not particularly limited, for example, a square (FIG. 2G), a circle (FIG. 2H), a triangle (FIG. 2I), etc. may be mentioned.

[0069] For the planar antenna slot, the minimum value of the straight line passing through the center point is 1 / 2λ mm. Here, 1 / 2λ mm includes an equivalent range in consideration of common general knowledge from the perspective of antenna efficiency that resonates at a specific frequency and as a result acts as a reflection filter for a specific band, and is not necessarily limited to 1 / 2λ mm, and is understood as a range having a width centered on 1 / 2λ mm.

[0070] In step (A4), referring to the above formulas (6) and (5), the interval in the direction of the electric field amplitude of the incident radio wave of the planar antenna slot is determined so as to satisfy this. In formula (6), x represents the interval in the direction of the electric field amplitude of the incident radio wave of the antenna slot, and y6 represents the transmission peak frequency. The interval x between the antenna slots is normalized as λ mm, and the transmission peak frequency y6 is normalized as F (GHz).

[0071] The interval x in the direction of the electric field amplitude of the incident radio wave of the antenna slot is 0.45 < x < 1.1, and 0.5 < x < 0.8 is preferable. Within this range, a transmission peak with an appropriate intensity for transmitting the target radio wave can be obtained.

[0072] The transmission peak frequency y6 satisfies 0.62 < y6 < 1.11, and preferably 0.68 < y6 < 1.01. When within this range, it will not deviate significantly from the frequency F (GHz) that serves as the reference for the selectively transmitted radio waves.

[0073] In Equation (6), k is a number that satisfies -0.12 < k < -0.02, preferably -0.11 < k < -0.03, and more preferably -0.10 < k < -0.04. l is a number that satisfies 0.75 < l < 1.12, preferably 0.77 < l < 1.10, and more preferably 0.80 < l < 1.08.

[0074] In Equation (5), x represents the interval in the direction of the electric field amplitude of the incident radio wave on the antenna slot, and y5 represents the bandwidth at -3 dB from the transmission peak vertex. The interval x of the antenna slots is normalized with respect to λ mm, and the bandwidth y5 is normalized with respect to F (GHz).

[0075] The bandwidth y5 at -3 dB from the transmission peak vertex is, from the perspective of frequency selection performance, 0 < y5 < 0.28, and preferably 0.03 < y5 < 0.25.

[0076] In Equation (5), i is a number that satisfies -0.21 < i < -0.02, preferably -0.15 < i < -0.025, and more preferably -0.09 < i < -0.03. j is a number that satisfies 0.12 < j < 0.29, preferably 0.15 < j < 0.26, and more preferably 0.18 < j < 0.23.

[0077] The interval in the direction of the electric field amplitude of the incident radio wave on the planar antenna slot is determined with reference to Equations (6) and (5) so as to satisfy this condition. Within the range of the interval x of the antenna slots, both the frequency and the bandwidth change. Therefore, according to the purpose of selectively transmitting only the radio waves in a specific frequency band and reflecting the radio waves outside the specific frequency band, or applications where not only the frequency but also the bandwidth is specified, the frequency and the bandwidth can be designed.

[0078] The method for manufacturing the radio wave reflection sheet in this embodiment may further include the following step (A4-1). Step (A4-1): Prepare a selective radio wave reflection sheet with different intervals between the antenna slots, measure the transmission frequency characteristics, and obtain the straight lines of the formulas (6) and (5).

[0079] In this step (A4-1), the formulas (6) and (5) for designing the frequency and bandwidth can be obtained. The number of selective radio wave reflection sheets to be prepared is not particularly limited. For example, within the range of the interval x of the antenna slots in the formulas (6) and (5), several points are prepared and the transmission frequency characteristics are measured. Then, the formulas (6) and (5) can be obtained from the straight line derived from these points. After that, by performing steps (A4) and (B4), simple-shaped antenna elements are evenly arranged, and the frequency and bandwidth can be easily designed only by changing the arrangement interval. The method for obtaining the straight line is not particularly limited, and a conventionally known method can be used. For example, a straight line passing through two points may be used, or a statistical analysis method such as the least squares method can be used.

[0080] In this embodiment, in step (B4), the planar antenna slots are used to manufacture a selective radio wave reflection sheet in which the planar antenna slots are evenly arranged on the conductive sheet at the determined interval.

[0081] Here, the even arrangement is intended to be an even arrangement in the direction of the electric field amplitude of the incident radio wave, and it is not necessarily required that the interval W1 in the direction of the magnetic field amplitude of the incident radio wave and the interval W2 in the direction of the electric field amplitude of the incident radio wave orthogonal thereto are the same. However, it is preferable that both the interval W1 and the interval W2 are within the range of the interval x of the antenna slots. In this way, based on the formulas (6) and (5), simple-shaped antenna elements are evenly arranged, and the frequency and bandwidth can be easily designed only by changing the arrangement interval.

[0082] In the above-described Embodiments 1 to 4, the manufacturing of the selective radio wave reflection sheet can be performed by, for example, known techniques. In Embodiments 1 and 2, a selective radio wave reflection sheet is manufactured by arranging antenna patches evenly on a dielectric sheet at the determined intervals. In Embodiments 3 and 4, a selective radio wave reflection sheet is manufactured by arranging antenna slots evenly on the surface of a conductive sheet at the determined intervals.

[0083] When patches, which are conductive patterns of a specific shape, are arranged in an array on a dielectric sheet, reflection occurs at a specific frequency with respect to the electromagnetic wave propagating in space, and it acts as a radio wave filter. That is, the FSS of the patch type structure composed of conductor patches acts as a band-stop filter that reflects only radio waves of a specific frequency.

[0084] When a conductive surface is provided on a dielectric sheet and slots, which are conductive patterns extracted in a specific shape, are arranged in an array, transmission occurs at a specific frequency with respect to the electromagnetic wave propagating in space, and it acts as a radio wave filter. That is, the FSS of the slot type structure composed of conductor slots acts as a band-pass filter that transmits only radio waves of a specific frequency.

[0085] This FSS is a spatial filter having a function of transmitting or blocking only radio waves of a specific frequency. Since a resonance structure is used, the size of its structure needs to be at least about the same as the wavelength. Taking one resonance structure as a unit, it consists of a periodic structure arranged in an array. The FSS radio wave reflection sheet has a periodic structure composed of N×M (N, M = 1, 2, 3, …) cells in which a plurality of element patterns of patches or slots of a certain shape are arranged at a certain period, and has frequency selectivity to reflect or transmit only radio waves of a specific frequency. That is, the antenna patches or slots are arranged in a matrix as shown in FIGS. 1 and 2, and these antenna patches or slots are arranged at a certain interval so that adjacent antenna patches or slots do not contact each other.

[0086] The dielectric sheets of Embodiments 1 and 2 are not particularly limited as long as they are made of a material having dielectric properties that function as an FSS. For example, resin materials, ceramics, glass, paper, etc. can be used. Examples of resin materials include polyester resin, acrylic resin, epoxy resin, fluororesin, silicone resin, polycarbonate resin, polyvinyl chloride, polyimide resin, polyamide resin, polyolefin resin, and the like. The conductive pattern of the antenna patch on the dielectric sheet in Embodiments 1 and 2 and the conductive surface of the conductive sheet in Embodiments 3 and 4 can be formed of a conductive material. Examples of conductive materials include metals such as aluminum, silver, copper, gold, platinum, iron, etc. or their alloys, conductive carbon materials such as carbon and graphite, and conductive oxides such as indium tin oxide (ITO) and indium zinc oxide (IZO).

[0087] Examples of methods for forming a conductive layer such as the conductive pattern of the antenna patch and the conductive surface of the conductive sheet include printing on the dielectric sheet, attaching the conductive sheet to the dielectric sheet, and forming a conductive layer on the dielectric sheet by thin film technology. For printing on the dielectric sheet, conductive ink can be used. For example, a conductive layer can be formed by applying a conductive ink in which fine particles of a conductive material are dispersed in a binder to the dielectric sheet and then drying it. In the method using thin film technology, for example, a conductive layer can be formed by a film forming method such as vapor deposition method, sputtering method, chemical vapor deposition method (CVD method), etc., and it may be patterned into a predetermined shape by a patterning method such as photolithography.

[0088] The thickness of the conductive pattern of the antenna patch and the conductive surface of the conductive sheet is not particularly limited, but is preferably 0.1 μm to 5 mm, more preferably 0.5 μm to 1 mm, and even more preferably 1 to 50 μm from the viewpoints of easy processing and good reflection performance.

[0089] The thickness of the dielectric sheet and the conductive sheet is not particularly limited, but is preferably 0.01 to 10 mm, more preferably 0.05 to 2 mm from the viewpoints of easy processing and easy installation.

[0090] The selective radio wave reflection sheets of Embodiments 1 to 4 can be used as radio wave absorbers. Specifically, by using them as the reflection films which are the components of the λ / 4 type radio wave absorber, a radio wave absorber having the function of absorbing specific radio waves and transmitting other radio waves can be fabricated. The λ / 4 type radio wave absorber is formed by laminating a resistive film, a dielectric sheet, and a reflection film in this order, and the resistive film is disposed via the dielectric sheet so as to be at a position separated from the reflection film by λ / 4 with respect to the wavelength λ of the radio waves to be absorbed. Thereby, resonance cancellation occurs between the incident radio wave and the λ / 4 wavelength of the incident radio wave, and the radio wave is absorbed.

Example

[0091] Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to these examples.

[0092] 1) Calculation of frequency and bandwidth The frequency F (GHz) and wavelength λ (mm) serving as the reference (normalizing) for the measurement sample for deriving a straight line were set to a frequency of 3.7 GHz and a wavelength of 81 mm, and 0.25, 0.5, 0.75, and 1 were substituted for x in the above formulas (1) to (6) to calculate the peak frequency and bandwidth of the rod-shaped patch type, circular ring-shaped patch type, circular patch type, rod-shaped slot type, and square slot type radio wave reflection sheets. The results are shown in Table 1.

[0093]

Table 1

[0094] 2) Fabrication of radio wave reflection sheet Based on the results in Table 1, a radio wave reflection sheet was fabricated. Example 1 Fabrication of rod-shaped patch type radio wave reflection sheet An aluminum sheet of the same size was bonded to a 70 cm square adhesive sheet. As shown in Fig. 3A, the aluminum sheet was cut using a cutting plotter so that the horizontal and vertical intervals of the rod-shaped patches were both arranged at 0.25λ. While confirming that the rod-shaped patch portions were attached to the adhesive sheet, the aluminum sheet other than the rod-shaped patch portions was peeled off from the adhesive sheet.

[0095] Example 2 Production of a rod-shaped patch type radio wave reflection sheet In Example 1, as shown in Fig. 3B, cuts were made so that the horizontal and vertical intervals of the rod-shaped patches were both arranged at 0.5λ. Otherwise, a rod-shaped patch type radio wave reflection sheet was produced in the same manner as in Example 1.

[0096] Comparative Example 1 Production of a rod-shaped patch type radio wave reflection sheet In Example 1, as shown in Fig. 3C, cuts were made so that the horizontal and vertical intervals of the rod-shaped patches were both arranged at 0.75λ. Otherwise, a rod-shaped patch type radio wave reflection sheet was produced in the same manner as in Example 1.

[0097] Example 3 Production of a circular ring-shaped patch type radio wave reflection sheet In Example 1, as shown in Fig. 3D, cuts were made so that the horizontal and vertical intervals of the circular ring-shaped patches were both arranged at 0.25λ. Otherwise, a circular ring-shaped patch type radio wave reflection sheet was produced in the same manner as in Example 1.

[0098] Example 4 Production of a circular ring-shaped patch type radio wave reflection sheet In Example 3, as shown in Fig. 3E, cuts were made so that the horizontal and vertical intervals of the circular ring-shaped patches were both arranged at 0.5λ. Otherwise, a circular ring-shaped patch type radio wave reflection sheet was produced in the same manner as in Example 3.

[0099] Comparative Example 2 Production of a circular ring-shaped patch type radio wave reflection sheet In Example 3, as shown in FIG. 3F, cuts were made so that the horizontal and vertical intervals of the circular ring-shaped patches were both arranged at 0.75λ. Otherwise, a circular ring-shaped patch type radio wave reflection sheet was produced in the same manner as in Example 3.

[0100] Example 5 Production of a circular patch type radio wave reflection sheet In Example 1, as shown in FIG. 3G, cuts were made so that the horizontal and vertical intervals of the circular patches were both arranged at 0.25λ. Otherwise, a circular patch type radio wave reflection sheet was produced in the same manner as in Example 1.

[0101] Example 6 Production of a circular patch type radio wave reflection sheet In Example 5, as shown in FIG. 3H, cuts were made so that the horizontal and vertical intervals of the circular patches were both arranged at 0.5λ. Otherwise, a circular patch type radio wave reflection sheet was produced in the same manner as in Example 5.

[0102] Comparative Example 3 Production of a circular patch type radio wave reflection sheet In Example 5, as shown in FIG. 3I, cuts were made so that the horizontal and vertical intervals of the circular patches were both arranged at 0.75λ. Otherwise, a circular patch type radio wave reflection sheet was produced in the same manner as in Example 5.

[0103] Example 7 Production of a rod-shaped slot type radio wave reflection sheet An aluminum sheet of the same size was bonded to a 70 cm square adhesive sheet. As shown in FIG. 4B, cuts were made in the aluminum sheet using a cutting plotter so that the horizontal interval of the rod-shaped slots was 0.25λ and the vertical interval was 0.5λ. The aluminum sheet of the rod-shaped slot portion was peeled off from the adhesive sheet.

[0104] Example 8 Production of a rod-shaped slot type radio wave reflection sheet In Example 7, as shown in FIG. 4C, cuts were made so that the horizontal spacing of the rod-shaped slots was 0.25λ and the vertical spacing was λ. A rod-shaped slot type radio wave reflection sheet was produced in the same manner as in Example 7 except for this.

[0105] Comparative Example 4 Production of a rod-shaped slot type radio wave reflection sheet In Example 7, as shown in FIG. 4A, cuts were made so that the horizontal spacing of the rod-shaped slots was 0.25λ and the vertical spacing was 0.25λ. A rod-shaped slot type radio wave reflection sheet was produced in the same manner as in Example 7 except for this.

[0106] Example 9 Production of a square slot type radio wave reflection sheet In Example 7, as shown in FIG. 4E, cuts were made so that both the horizontal spacing and the vertical spacing of the square slots were 0.5λ. A square slot type radio wave reflection sheet was produced in the same manner as in Example 7 except for this.

[0107] Example 10 Production of a square slot type radio wave reflection sheet In Example 9, as shown in FIG. 4F, cuts were made so that both the horizontal spacing and the vertical spacing of the square slots were λ. A square slot type radio wave reflection sheet was produced in the same manner as in Example 9 except for this.

[0108] Comparative Example 5 Production of a square slot type radio wave reflection sheet In Example 9, as shown in FIG. 4D, cuts were made so that both the horizontal spacing and the vertical spacing of the square slots were 0.25λ. A square slot type radio wave reflection sheet was produced in the same manner as in Example 9 except for this.

[0109] 3) Measurement of reflection characteristics and transmission characteristics Method for measuring transmission attenuation rate (S21) The radio wave reflection sheet was placed between horn antenna 1 and horn antenna 2. Of the radio waves radiated from antenna 1, part is reflected by the sheet and the rest is transmitted and received by antenna 2. The ratio of the incident power of the radio waves radiated from antenna 1 to the transmitted power of the radio waves received by antenna 2 (transmission attenuation rate) was calculated. S21(dB)=10×log(Transmitted power / Incident power)

[0110] Method for calculating bandwidth In the case of the patch type, the width of -10 dB was defined as the bandwidth. In the case of the slot type, the width of -3 dB from the peak vertex was defined as the bandwidth.

[0111] For each radio wave reflection sheet, the measurement results of the frequency dependence of S21 are shown in FIGS. 5 and 6. The peak frequencies and bandwidths obtained from the measured values are shown in Table 2. An "×" in the table indicates that no peak was obtained, or the peak intensity was low and the bandwidth could not be calculated. All the examples were within the range of the values calculated from the straight line. In the comparative examples, the peak intensity was less than -10 dB and the intensity was low, so they did not function as selective radio wave reflection sheets. In Comparative Example 4, the bandwidth was wider than the calculated result and it transmitted a wide range of frequencies, so the frequency selection performance was insufficient.

[0112]

Table 2

[0113] 4) Creation of frequency vs. element spacing graph and bandwidth vs. element spacing graph and derivation of straight line For the rod-shaped patch type radio wave reflection sheets of Example 1 and Example 2, a graph was created with the normalized interval with λ = 81 mm on the horizontal axis and the normalized peak frequency and bandwidth with F = 3.7 GHz on the vertical axis, and a straight line was calculated. (Figs. 7A, 7B) Straight line of frequency vs. element spacing: y f =-0.45x + 1.15 (7) Straight line of bandwidth vs. element spacing: y w =-0.36x + 0.22 (8)

[0114] For the circular ring patch type radio wave reflection sheets of Example 3 and Example 4, in the same manner as in Example 1 and Example 2, a straight line was calculated. (Figs. 7A, 7B) Straight line of frequency vs. element spacing: y f =-0.38x + 1.22 (9) Straight line of bandwidth vs. element spacing: y w =-0.24x + 0.16 (10)

[0115] For the circular patch type radio wave reflection sheets of Example 5 and Example 6, in the same manner as in Example 1 and Example 2, a straight line was calculated. (Figs. 7A, 7B) Straight line of frequency vs. element spacing: y f =-0.93x + 1.37 (11) Straight line of bandwidth vs. element spacing: y w =-0.14x + 0.11 (12)

[0116] For the rod-shaped slot type radio wave reflection sheets of Example 7 and Example 8, in the same manner as in Example 1 and Example 2, a straight line was calculated. (Figs. 7A, 7B) Straight line of frequency vs. element spacing: y f =-0.34x + 1.17 (13) Straight line of bandwidth vs. element spacing: y w =-0.18x + 0.25 (14)

[0117] For the square slot type radio wave reflection sheets of Example 9 and Example 10, in the same manner as in Example 1 and Example 2, a straight line was calculated. (Figs. 7A, 7B) Straight line of frequency vs. element spacing: y f =-0.05x + 0.86 (15) Straight line of bandwidth vs. element spacing: y w =-0.05x + 0.14 (16)

[0118] <Example A> In items 2) to 4) above, from the straight lines obtained in Examples 1 and 2, the interval in the magnetic field amplitude direction of the incident radio wave of the rod-shaped patch (linear antenna patch) is referred to the formula (7) included in the above formula (1) and the formula (8) included in the above formula (2), and a step of determining it to satisfy this, and a step of manufacturing a selective radio wave reflection sheet in which the rod-shaped patches (linear antenna patches) are evenly arranged on the dielectric sheet at the determined interval, a reference (normalized) frequency F (GHz), wavelength λ (mm), that is, an example for obtaining a radio wave reflection sheet that selectively reflects radio waves of a target frequency in the vicinity of a frequency of 3.7 GHz and a wavelength of 81 mm was shown.

[0119] <Example B> In items 2) to 4) above, from the straight lines obtained in Examples 3 and 4, the interval in the magnetic field amplitude direction of the incident radio wave of the circular ring patch (ring-shaped antenna patch) is referred to the formula (9) included in the above formula (1) and the formula (10) included in the above formula (2), and a step of determining it to satisfy this, and a step of manufacturing a selective radio wave reflection sheet in which the circular ring patches (ring-shaped antenna patches) are evenly arranged on the dielectric sheet at the determined interval, a reference (normalized) frequency F (GHz), wavelength λ (mm), that is, an example for obtaining a radio wave reflection sheet that selectively reflects radio waves of a target frequency in the vicinity of a frequency of 3.7 GHz and a wavelength of 81 mm was shown.

[0120] <Example C> In items 2) to 4) above, from the straight lines obtained in Examples 5 and 6, the interval in the magnetic field amplitude direction of the incident radio wave of the circular patch (plane antenna patch) is referred to the formula (11) included in the above formula (3) and the formula (12) included in the above formula (2), and a step of determining it to satisfy this, and a step of manufacturing a selective radio wave reflection sheet in which the circular patches (plane antenna patches) are evenly arranged on the dielectric sheet at the determined interval, a reference (normalized) frequency F (GHz), wavelength λ (mm), that is, an example for obtaining a radio wave reflection sheet that selectively reflects radio waves of a target frequency in the vicinity of a frequency of 3.7 GHz and a wavelength of 81 mm was shown.

[0121] <Example D> In the above items 2) to 4), from the straight lines obtained in Examples 7 and 8, referring to Equation (13) included in the aforementioned Equation (4) and Equation (14) included in the aforementioned Equation (5), the interval in the magnetic field amplitude direction of the incident radio waves of the rod-shaped slot (linear antenna slot) is determined so as to satisfy this, and the rod-shaped slot (linear antenna slot) is evenly arranged on the dielectric sheet at the determined interval. By the step of manufacturing the selective radio wave reflection sheet, an example for obtaining a radio wave reflection sheet that selectively transmits radio waves of a target frequency in the vicinity of the reference (normalized) frequency F (GHz) and wavelength λ (mm), that is, a frequency of 3.7 GHz and a wavelength of 81 mm, was shown.

[0122] <Example E> In the above items 2) to 4), from the straight lines obtained in Examples 9 and 10, referring to Equation (15) included in the aforementioned Equation (6) and Equation (16) included in the aforementioned Equation (5), the interval in the magnetic field amplitude direction of the incident radio waves of the square slot (plane antenna slot) is determined so as to satisfy this, and the square slot (plane antenna slot) is evenly arranged on the dielectric sheet at the determined interval. By the step of manufacturing the selective radio wave reflection sheet, an example for obtaining a radio wave reflection sheet that selectively transmits radio waves of a target frequency in the vicinity of the reference (normalized) frequency F (GHz) and wavelength λ (mm), that is, a frequency of 3.7 GHz and a wavelength of 81 mm, was shown.

[0123] According to the above Examples A to E, there is no case where the frequency selection performance becomes insufficient due to low peak intensity, inability to calculate the bandwidth due to low peak intensity, wide bandwidth, and transmission of a wide range of frequencies. A radio wave reflection sheet that selectively reflects or transmits radio waves of a target frequency in the vicinity of the frequency F (GHz) and wavelength λ (mm), that is, a frequency of 3.7 GHz and a wavelength of 81 mm, can be obtained.

[0124] <Example F> In Example A, the reference (normalized) frequency F (GHz) and wavelength λ (mm) were set to a frequency of 3.7 GHz and a wavelength of 81 mm. In the following Example F, the reference (normalized) frequency F (GHz) and wavelength λ (mm) were changed to a frequency of 5.2 GHz and a wavelength of 57.7 mm. When the interval x in the magnetic field amplitude direction of the incident radio wave of the rod-shaped patch is 0.35λ (= 20.2 mm), From Equation (7), the frequency y f = -0.45 × 0.35 + 1.15 = 0.99 From Equation (8), the bandwidth y w = -0.36 × 0.35 + 0.22 = 0.09 is obtained. The frequency and bandwidth calculated from the straight lines of Equations (7) and (8) are Frequency: 0.99 × 5.2 = 5.15 GHz Bandwidth: 0.09 × 5.2 = 0.47 GHz is obtained.

[0125] A rod-shaped patch type radio wave reflection sheet with an interval x of 0.35λ in the magnetic field amplitude direction of the incident radio wave was fabricated. An aluminum sheet of the same size was bonded to a 70 cm square adhesive sheet. As shown in FIG. 8A, cuts were made in the aluminum sheet using a cutting plotter so that both the horizontal and vertical intervals of the rod-shaped patches would be arranged at 0.35λ. While confirming that the rod-shaped patch portion was attached to the adhesive sheet, the aluminum sheet other than the rod-shaped patch portion was peeled off from the adhesive sheet.

[0126] As described in item 3) "Measurement of reflection characteristics and transmission characteristics" above, the transmission attenuation rate was measured (S21), and the peak frequency and -10 dB bandwidth were obtained. The results are shown in FIG. 8B. The peak frequency was 5.2 GHz and the -10 dB bandwidth was 0.46 GHz, and the radio wave reflection sheet could be designed as calculated from the straight line. That is, as a method for manufacturing a radio wave reflection sheet that selectively reflects radio waves of a target frequency in the vicinity of a reference (normalized) frequency F (GHz) and a wavelength λ (mm), specifically, a frequency of 5.2 GHz and a wavelength of 57.7 mm, when the target reflection peak frequency (×F (GHz)) is 5.15 GHz and the bandwidth at -10 dB of the reflection peak (×F (GHz)) is 0.47 GHz, the interval in the magnetic field amplitude direction of the incident radio waves of the rod-shaped patch (linear antenna patch) is determined to be 0.35λ (= 20.2 mm) by referring to Equation (7) included in Equation (1) and Equation (8) included in Equation (2) above so as to satisfy this condition, and a selective radio wave reflection sheet in which the rod-shaped patches (linear antenna patches) are evenly arranged on the dielectric sheet at the determined interval is manufactured. An example for obtaining a radio wave reflection sheet that selectively reflects radio waves of a target frequency in the vicinity of a reference (normalized) frequency F (GHz) and a wavelength λ (mm), that is, a frequency of 5.2 GHz and a wavelength of 57.7 mm, is shown.

[0127] According to the above Example F, the peak intensity is not low, and the peak intensity is not so low that the bandwidth cannot be calculated. Also, in Equation (7) included in Equation (1) and Equation (8) included in Equation (2) above, even if the reference (normalized) frequency F (GHz) is changed from a frequency of 3.7 GHz and a wavelength of 81 mm to a frequency of 5.2 GHz and a wavelength of 57.7 mm, a radio wave reflection sheet that selectively reflects radio waves of a target frequency in the vicinity thereof can be obtained.

Description of Symbols

[0128] 1A Circular antenna patch 1B Linear antenna patch 1C Planar antenna patch 1D Circular antenna slot 1E Linear antenna slot 1F Planar antenna slot 2A Dielectric sheet 2B Conductive sheet

Claims

1. A method for manufacturing a radio wave reflection sheet that selectively reflects radio waves of a target frequency in the vicinity of a frequency F (GHz) and a wavelength λ (mm), comprising: a step of determining the interval in the magnetic field amplitude direction of incident radio waves of an annular antenna patch having a peripheral length of 1λ mm or a linear antenna patch having an element length of 1 / 2λ mm with reference to the following formulas (1) and (2) so as to satisfy them; and a step of manufacturing a selective radio wave reflection sheet in which the annular antenna patch or the linear antenna patch is evenly arranged on a dielectric sheet at the determined interval. 【Number 1】 (In the formula, a is a number satisfying -0.75 < a < -0.15, b is a number satisfying 0.97 < b < 1.29, x is the interval (×λ (mm)) in the magnetic field amplitude direction of the incident radio wave of the antenna patch satisfying 0.1 < x < 0.7, y 1 represents a reflection peak frequency (×F (GHz)) satisfying 0.45 < y 1 < 1.27.) 【Number 2】 (where c is a number satisfying -0.44 < c < -0.13, d is a number satisfying 0.08 < d < 0.31, x is the interval (×λ (mm)) in the magnetic field amplitude direction of the incident radio wave of the antenna patch satisfying 0.1 < x < 0.7, y 2 is 0 < y 2 shows the bandwidth (×F (GHz)) at -10 dB of the reflection peak satisfying < 0.29.)

2. A method for manufacturing a radio wave reflection sheet that selectively reflects radio waves of a target frequency in the vicinity of a frequency F (GHz) and a wavelength λ (mm), comprising: a step of determining the interval in the magnetic field amplitude direction of incident radio waves of a planar antenna patch having a minimum value of 1 / 2λ mm for a straight line passing through the center point with reference to the following formula (3) and the following formula (2) so as to satisfy them; and a step of manufacturing a selective radio wave reflection sheet in which the planar antenna patch is evenly arranged on a dielectric sheet at the determined interval. 【Number 3】 (In the formula, e is a number satisfying -1.35 < e < -0.90, f is a number satisfying 1.35 < f < 1.55, x is the interval (×λ (mm)) in the magnetic field amplitude direction of the incident radio wave of the antenna patch satisfying 0.1 < x < 0.7, y 3 is 0.41 < y 3 < 1.45 indicates the reflection peak frequency (×F (GHz)). ) 【Number 4】 (In the formula, c is a number satisfying -0.44 < c < -0.13, d is a number satisfying 0.08 < d < 0.31, x is the interval (×λ (mm)) in the magnetic field amplitude direction of the incident radio wave of the antenna patch satisfying 0.1 < x < 0.7, y 2 is 0 < y 2 shows the bandwidth (×F (GHz)) at -10 dB of the reflection peak satisfying < 0.29.)

3. A method for manufacturing a radio wave reflection sheet that selectively transmits radio waves of a target frequency in the vicinity of a frequency F (GHz) and a wavelength λ (mm), comprising: a step of determining the interval in the electric field amplitude direction of incident radio waves of an annular antenna slot having a peripheral length of 1λ mm or a linear antenna slot having an element length of 1 / 2λ mm with reference to the following formulas (4) and (5) so as to satisfy them; and a step of manufacturing a selective radio wave reflection sheet in which the annular antenna slot or the linear antenna slot is evenly arranged on a conductive sheet at the determined interval. 【Number 5】 (where g is a number satisfying -0.38 < g < -0.10, h is a number satisfying 0.95 < h < 1.18, x is the interval (×λ (mm)) in the direction of the electric field amplitude of the incident radio wave of the antenna slot satisfying 0.45 < x < 1.1, y 4 is 0.54 < y 4 < 1.13 indicates the transmission peak frequency (×F (GHz)).) 【Number 6】 (where i is a number satisfying -0.21 < i < -0.02, j is a number satisfying 0.12 < j < 0.29, x is the interval (×λ (mm)) in the direction of the electric field amplitude of the incident radio wave of the antenna slot satisfying 0.45 < x < 1.1, y 5 is 0 < y 5 shows the bandwidth (×F (GHz)) at -3 dB from the transmission peak apex satisfying < 0.28.)

4. A method for manufacturing a radio wave reflection sheet that selectively transmits radio waves of a target frequency in the vicinity of a frequency F (GHz) and a wavelength λ (mm), comprising: a step of determining the interval in the electric field amplitude direction of incident radio waves of a planar antenna slot having a minimum value of 1 / 2λ mm for a straight line passing through the center point with reference to the following formula (6) and the following formula (5) so as to satisfy them; and a step of manufacturing a selective radio wave reflection sheet in which the planar antenna slot is evenly arranged on a conductive sheet at the determined interval. 【Number 7】 (where k is a number satisfying -0.12 < k < -0.02, l is a number satisfying 0.75 < l < 1.12, x is the interval (×λ (mm)) in the direction of the electric field amplitude of the incident radio wave of the antenna slot satisfying 0.45 < x < 1.1, y 6 is 0.62 < y 6 < 1.11 indicates the transmission peak frequency (×F (GHz)). ) 【Number 8】 (where i is a number satisfying -0.21 < i < -0.02, j is a number satisfying 0.12 < j < 0.29, x is the interval (×λ (mm)) in the direction of the electric field amplitude of the incident radio wave of the antenna slot satisfying 0.45 < x < 1.1, y 5 is 0 < y 5 < 0.28 shows the bandwidth (×F (GHz)) at -3 dB from the transmission peak apex.

5. A method for manufacturing a selective radio wave reflection sheet according to any one of claims 1 to 4, further comprising a step of preparing a selective radio wave reflection sheet with a changed interval between the antenna patches or antenna slots and measuring frequency characteristics of reflection or transmission to obtain any one of the straight lines in the formulas (1) to (6).

6. The method for manufacturing a selective radio wave reflection sheet according to any one of claims 1 to 4, wherein the thickness of the sheet is 0.01 to 10 mm.

7. The method for manufacturing a selective radio wave reflection sheet according to any one of claims 1 to 4, wherein a conductive ink is used for the conductive portion.

8. A method for manufacturing a radio wave absorber, comprising using the selective radio wave reflection sheet obtained by the method according to any one of claims 1 to 4 as a component of the radio wave absorber.

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