Radio wave scattering direction control plate

Abstract

To provide a radio wave scattering direction control plate which has a small installation area, is easy to handle, has excellent weather resistance, and can control the scattering direction and intensity of incident radio waves.SOLUTION: A radio wave scattering direction control plate 1 is made of a conductor and has a sawtooth structure in which rectangular recesses 3 and protrusions 2 which are continuous in a y direction are alternately and repeatedly arranged in an x direction. The height of the teeth (height d of the recesses or protrusions) is set to a value within a specified range that includes a quarter of the wavelength λ of the radio wave, thereby suppressing the reflected power. The calculated bandwidth at which the reflected power is 1 / 100 is 0.029 λ, and the bandwidth relative to the center frequency, i.e. the relative bandwidth, in this case is 12% (Figure 2).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a radio wave scattering direction control plate that can control the scattering direction of incident radio waves (also called electromagnetic waves; the same applies below). [Background technology]

[0002] In radar operation and outdoor RCS measurements, it is necessary to take measures to suppress unwanted reflections from objects other than the target, i.e., clutter. In radar, clutter sources include various structures around the transmitting and receiving antennas. In outdoor measurements, the main clutter sources include buildings, trees, fences, signs, outdoor lights, surveillance cameras, etc. that are located at positions other than the target and are equidistant from the propagation path from the transmitting and receiving antennas to the target. Even if these clutter sources are obstacles to radar operation and outdoor RCS measurements, they often cannot be removed due to the necessity.

[0003] Therefore, in radar operation, outdoor RCS measurements, etc., it is necessary to scatter the radio waves arriving at obstacles that are clutter sources in a direction other than the direction of arrival, or to absorb them. A commonly known method for achieving this is to use an inclined metal plate (left side of Fig. 11) or a radio wave absorber (right side of Fig. 11), as shown in Fig. 11.

[0004] As shown in the upper diagram of Figure 11, when the metal plate is tilted so that the reflective surface on the left faces upward, the law of reflection causes the incident radio waves to be scattered mainly in the direction of specular reflection, so by changing the angle of inclination, the radio waves can be scattered in the desired direction.

[0005] The outdoor radio wave absorber shown in the lower diagram of FIG. 11 is expected to have the effect of absorbing radio waves and at the same time, to have the effect of scattering radio waves.

[0006] Furthermore, as shown in the following Patent Documents 1 and 2, scattering direction control using reflectarrays and metasurfaces is known as a technique for improving the propagation area in mobile communication systems. This is a technique that uses a flat plate with a periodic structure to scatter radio waves incident from the front in the desired direction without tilting it. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2013-48344 [Patent Document 2] Patent Publication No. 2021-48465 [Patent Document 3] Patent Publication No. 2012-39587 Summary of the Invention [Problem to be solved by the invention]

[0008] The method of using a tilted flat metal plate, as shown in the upper diagram of Figure 11, had the following problems. In other words, unlike light rays, when the flat metal plate is tilted, radio waves, although the frontal reflection is reduced, still have a considerable amount of reflection in the direction of incidence, so the tilt angle needs to be large. However, if the tilt angle is large, the projected area on the installation surface increases, and the area required for installation becomes enormous. In addition, the tilted flat metal plate needs to be supported safely, but this is difficult and dangerous, especially when installing at high places, so the method of using a tilted flat metal plate cannot be said to be realistic from a safety standpoint.

[0009] The method of suppressing clutter using outdoor radio wave absorbers shown in the lower diagram of Fig. 11 had the following problems. In other words, outdoor radio wave absorbers have inferior absorption performance compared to radio wave absorbers for anechoic chambers, and the longer the distance to the target, the wider the range over which radio waves are irradiated, making it practically difficult to apply radio wave absorbers to all clutter sources. In addition, deterioration of quality due to sunlight cannot be ignored. Furthermore, since the incident radio waves are converted into heat and consumed, a certain degree of thickness is unavoidable, which requires troublesome handling, and in addition, deterioration of quality is likely to occur in outdoor environments, making them unsuitable for long-term use.

[0010] In addition, controlling the scattering direction using the reflectarrays and metasurface reflectors exemplified in Patent Documents 1 and 2 requires microfabrication of conductive reflective elements on a substrate, which is not realistic in terms of cost-effectiveness.

[0011] Incidentally, Patent Document 3 discloses an invention regarding a radio wave scatterer. According to the description in the document, by using this radio wave scatterer, radio waves can be scattered in all directions, but if this is the case, reflection should also occur in the incident direction, as with the conductive sphere, and this cannot be a technology for controlling the scattering direction of incident radio waves as desired by the present inventors.

[0012] The present invention has been made in consideration of the conventional technology and its problems described above, and aims to provide a radio wave scattering direction control plate that does not require installation at a large inclination angle and therefore requires a small installation area, is easy to handle, has excellent weather resistance, and can control the scattering direction and intensity of incident radio waves. [Means for solving the problem]

[0013] The radio wave scattering direction control plate described in claim 1 is characterized in that it is made of a conductor and has a structure in which rectangular recesses and protrusions that are continuous in a first direction are alternately and repeatedly arranged in a second direction perpendicular to the first direction.

[0014] The radio wave scattering direction control plate according to claim 2 is the radio wave scattering direction control plate according to claim 1, The present invention is characterized in that a dielectric sheet is provided on the surface of the protrusions so as to cover the recesses.

[0015] The radio wave scattering direction control plate according to claim 3 is the radio wave scattering direction control plate according to claim 1, The present invention is characterized in that at least one of a dielectric material and a magnetic material is provided inside the recess.

[0016] The radio wave scattering direction control plate according to claim 4 is the radio wave scattering direction control plate according to claim 1, The depth (d) of the recess or the height (d) of the protrusion is set to a value within a predetermined range including a quarter of the wavelength (λ) of the radio wave.

[0017] The radio wave scattering direction control plate according to claim 5 is the radio wave scattering direction control plate according to claim 1, The ratio (W / L) of the length (W) of the recess in the second direction to the total length (period L) of the recess and the protrusion in the second direction is set to a value within a predetermined range including 0.5.

[0018] The radio wave scattering direction control plate according to claim 6 is the radio wave scattering direction control plate according to claim 1, The total length (period L) of the recesses and protrusions adjacent to each other in the second direction is set to a value within the range of one wavelength (λ) to two wavelengths (2λ) of radio waves.

[0019] The radio wave scattering direction control plate according to claim 7 is the radio wave scattering direction control plate according to claim 1, The depths of two of the recesses adjacent to each other in the second direction or the heights of two of the protrusions adjacent to each other in the second direction are different from each other. Effect of the Invention

[0020] According to the radio wave scattering direction control plate described in claim 1, in a sawtooth structure composed of recesses and protrusions with a rectangular cross section, the dimensions of the recesses and protrusions, for example, the depth of the recesses and the height of the protrusions, which are dimensions in a direction perpendicular to both the first direction and the second direction, and the length of the recesses and protrusions in the second direction, can be appropriately set to control the scattering direction and intensity of the incident radio wave, thereby reducing the intensity of unnecessary radio waves reflected in the incident direction. In addition, since this radio wave scattering direction control plate is composed of a conductor, it is easy to manufacture, material costs and manufacturing costs can be reduced, and it has excellent weather resistance and is less likely to deteriorate compared to a radio wave absorber. In addition, since the radio waves are reflected on the surface of the radio wave scattering direction control plate, it is not necessarily required to manufacture it by cutting out a block of conductor, and it can be manufactured by sheet metal processing of a thin conductor plate, so it can also be made lighter.

[0021] According to the radio wave scattering direction control plate described in claim 2, by providing a dielectric sheet that is not easily affected by radio waves on the surface of the convex portion and covering the concave portion, it is possible to prevent rainwater from entering the concave portion, and to prevent fluctuations in the radio wave scattering performance due to water entering the concave portion.

[0022] According to the radio wave scattering direction control plate described in claim 3, the internal wavelength becomes shorter according to the relative dielectric constant of the material provided inside the recess, so that the thickness of the radio wave scattering direction control plate can be reduced while maintaining the same effect as when the inside of the recess is air.

[0023] According to the radio wave scattering direction control plate described in claim 4, by setting the depth (d) of the concave portion or the height (d) of the convex portion to a value within a predetermined range including a quarter of the wavelength (λ) of the radio wave, it is possible to match the directionally controlled radio wave to a desired frequency.

[0024] According to the radio wave scattering direction control plate described in claim 5, the ratio of the length (W) of the recess in the second direction to the total length (period L) of adjacent recesses and protrusions in the second direction is set to a value within a predetermined range including 0.5, thereby making it possible to reduce the reflected electric field to a desired level or below.

[0025] According to the radio wave scattering direction control plate described in claim 6, the total length (period L) of the concave and convex portions adjacent to each other in the second direction is set to a value within the range of one wavelength (λ) to two wavelengths (2λ) of the radio wave, thereby making it possible to reduce the reflection scattering angle (θ n ) can be set arbitrarily within the range of 30° to 90° in elevation angle.

[0026] According to the radio wave scattering direction control plate described in claim 7, by making the depths of two adjacent recesses or the heights of two adjacent protrusions (period L) different values ​​in the second direction, that is, by providing two or more values ​​for the depth (d) of the recesses or the height (d) of the protrusions, the bandwidth (fractional bandwidth) of the controlled radio waves can be expanded. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a longitudinal cross-sectional view of a radio wave scattering direction control plate according to a first embodiment, in which FIG. 1(a) shows an example of a structure when manufactured by sheet metal processing, FIG. 1(b) shows an example of a structure when manufactured by cutting out metal, and FIG. 1(c) shows an example of a structure in which a dielectric sheet is provided on the surface side where radio waves are incident in the example of FIG. 1(b). [Diagram 2] FIG. 1 is a graph showing the relationship between the height of the tooth profile (depth d of the concave portion or height d of the convex portion normalized by wavelength λ, i.e. d / λ) and the reflected electric field (Erx I / Ein) in the radio wave scattering direction control plate of the first embodiment, and an explanatory diagram showing an enlarged portion of the graph to explain an example of a bandwidth in which reflection is suppressed. [Diagram 3] This figure shows the relationship between the width ratio of the tooth profile (the ratio of the length W of the recess in the second direction to the total length (period) L of the recess and protrusion in the second direction, i.e., W / L) and the reflected electric field (Erx I / Ein) and scattered electric field (Erx I / Ein) for different periods (L) defined by wavelength (λ) in the first embodiment. [Figure 4] 4 is a graph showing the relationship between the period (L / λ) of the tooth profile normalized by the wavelength (λ) and the reflection scattering angle (θn) in the first embodiment. [Diagram 5] FIG. 2 is an explanatory diagram showing the direction of scattered waves (reflection / scattering angle (θn)) when radio waves are incident from the front in the first embodiment. [Figure 6] 1 is a graph showing the relationship between the period (L / λ) of the tooth profile normalized with the wavelength (λ) and the reflected electric field (Erx I / Ein) and the scattered electric field (Erx I / Ein) in the first embodiment. [Figure 7] FIG. 2 is an explanatory diagram showing the direction of scattered waves (reflection / scattering angle (θn)) when radio waves are obliquely incident at an incident angle (θi) in the first embodiment. [Figure 8] 4 is a graph showing the relationship between the angle of incidence (θi) of an incident wave and the angle of reflection / scattering (θn) when a radio wave is obliquely incident in the first embodiment. [Figure 9] FIG. 13 is a longitudinal cross-sectional view of a radio wave scattering direction control plate according to a second embodiment manufactured by sheet metal processing, showing an example structure in which the front ends of the tooth-shaped protrusions are flush with each other and the height of the tooth-shaped protrusions or the depth of the recesses include two different dimensions, d1 and d2. [Figure 10] FIG. 11 is a longitudinal cross-sectional view of a radio wave scattering direction control plate according to a third embodiment manufactured by sheet metal processing, showing an example structure in which the bottom surfaces of the tooth-shaped recesses are flush with each other, and the height of the tooth-shaped protrusions or the depth of the recesses include two different dimensions, d1 and d2. [Figure 11] 1 is an explanatory diagram of a conventional radio wave scattering direction control using an inclined metal plate and an outdoor radio wave absorber. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] A first embodiment of the present invention will be described with reference to FIGS. The radio wave scattering direction control plate of the embodiment shown in Fig. 1(a) is formed by bending a metal sheet made of a conductor, and as can be seen from its cross-sectional shape, it has a sawtooth-like repeating structure in which rectangular convex parts (tooth parts) 2 and concave parts (slots) 3 appear alternately and continuously. The radio wave scattering direction control plate 10 of the embodiment shown in Fig. 1(b) is formed by cutting out a conductor, unlike the radio wave scattering direction control plate 1 shown in Fig. 1(a), but the shape and structure of its reflecting surface are similar to the radio wave scattering direction control plate 1 of Fig. 1(a), and since radio waves are reflected and scattered by the reflecting surface without penetrating the conductor as with the radio wave scattering direction control plate 1 shown in Fig. 1(a), the obtained action and effect are similar to that of the radio wave scattering direction control plate 1 of Fig. 1(a).

[0029] The radio wave scattering direction control plate 10 shown in Fig. 1(c) is the radio wave scattering direction control plate 10 of the embodiment shown in Fig. 1(b) in which a dielectric sheet 4 is provided on the surface of the protrusion 2 to cover the recess 3. This radio wave scattering direction control plate 10 can prevent rainwater from entering the recess 3, and can prevent the radio wave scattering performance of the radio wave scattering direction control plate 1 described below from being affected by water that has entered the recess 3. Note that the dielectric sheet 4 is not easily affected by radio waves, and therefore does not affect the radio wave scattering performance of the radio wave scattering direction control plate 10.

[0030] 1(a) to 1(c), one or both of a dielectric material and a magnetic material may be provided inside the recess 3. According to this radio wave scattering direction control plate 1, 10, the internal wavelength becomes shorter depending on the relative dielectric constant of the material provided inside the recess 3, so the thickness of the radio wave scattering direction control plate 1, 10 can be reduced while maintaining the same effect as when the recess 3 is filled with air. For example, in the radio wave scattering direction control plate 1, 10, when there is no dielectric material in the recess 3 and the recess 3 is filled with air, the wavelength is 3 cm when the frequency of the radio wave is 10 GHz, but when a dielectric material is placed in the recess 3, the wavelength becomes shorter than 3 cm depending on the relative dielectric constant (>1) of the material.

[0031] The structure of the radio wave scattering direction control plates 1, 10 will be described more specifically with reference to FIG. The radio wave scattering direction control plates 1, 10 have rectangular projections (teeth) 2 and recesses (slots) 3 that are uniformly continuous along the y direction (perpendicular to the paper) as a first direction, and also have a sawtooth structure in which the projections 2 and recesses 3 are repeatedly and alternately arranged along the x direction (up and down direction on the paper) as a second direction perpendicular to the y direction. The direction perpendicular to both the x and y directions is called the z direction (left and right direction on the paper). Here, the depth of the recesses 3 or the height of the projections 2 is represented by d (collectively referred to as "height" d), and the total length of the adjacent recesses 3 and projections 2 in the x direction, i.e., one period of repetition of the uneven structure, is represented by L.

[0032] As shown in Fig. 1(a), an incident wave (magnetic field H y and electric field E) at an incidence angle of θ i The reflected and scattered waves are obtained when the incident waves enter the radio wave scattering direction control plate 1 in the manner described above. The same is true for the radio wave scattering direction control plate 10. Here, the free space where the incident waves arrive is taken as Region I, and the interior of the recesses 3 between the protrusions 2 is taken as Region II, and the symbols expressing the physical quantities in each region are given the suffixes I and II.

[0033] The names and symbols of the dimensions of each part of the radio wave scattering direction control plate 1, 10 described above, as well as the letters, coefficients, functions, and other symbols used to write the formulas used to calculate the reflected scattered waves, and their meanings are summarized in the following (Equation 1).

[0034]

number

[0035] By defining the electromagnetic field of each region so as to satisfy Maxwell's equations and substituting them into the equation expressing the boundary condition of z=0 and rearranging them, we obtain the fundamental equation shown in the following (Equation 2):

[0036]

number

[0037] Where k x is the phase constant of the incident wave, k x I is the phase constant of the reflected and scattered waves in the first region. k x II is the phase constant of region II.

[0038] The above basic equation (1) is expanded with coefficient B m If we substitute the required number of terms m into the following equation (2) (Equation 3), we get the coefficient A representing the reflected and scattered waves in the I region. n is required.

[0039]

number

[0040] The obtained A n Using this, the reflected and scattered wave (electric field) in the I region can be expressed by the following equation (3) shown in (Mathematical Expression 4).

[0041]

number

[0042] When the radio wave is incident from the front (θ i = 0), that is, the value that means the reflection coefficient A0 when n = 0, that is, the reflected electric field E of region I obtained from equation (3) rx The incident electric field E in Divided by (E rx I / E in ) on the vertical axis and d / λ, the height d of the protrusion 2 (tooth shape) normalized by the wavelength λ, on the horizontal axis for calculations. The results are shown in the upper graph of Figure 2. The lower graph is an enlarged view of the minimum value of height d near λ / 4 (d / λ near 0.25) in the upper graph. In the lower graph, as a guide for controlling the scattering of radio waves, the bandwidth where the reflected electric field normalized by the incident electric field is 0.1, in other words, the bandwidth where the reflected power is 1 / 100, was found to be 0.029λ, and the bandwidth relative to the center frequency in this case, in other words, the relative bandwidth, was 12%.

[0043] Reflected and scattered electric fields (E rx I / E in ) is plotted on the horizontal axis as the ratio of the length (W) of the recess 3 in the x direction to the sum (period L) of the lengths of the recess 3 and the protrusion 2 adjacent to each other in the x direction, that is, the width ratio W / L, and the results of calculations for different periods (L) defined by the wavelength (λ), that is, (a) to (c), are shown in the graph of FIG. 3. According to FIG. 3, for each period, the characteristic that the reflected electric field becomes minimum when the width ratio W / L is in the vicinity of 0.5 is obtained. However, it can also be seen that the minimum is not necessarily achieved exactly at a width ratio of 0.5. From this, it can be said that the reflected wave from the tip surface of the protrusion 2 and the reflected wave from the bottom surface of the recess 3 do not cancel each other out simply when the width ratio is 1:1. Therefore, by changing the width ratio W / L in the range exceeding 0:1 and less than 1:0, the scattered electric field (E rx I / E in In this case, the width ratio W / L can be controlled within a predetermined range including 0.5 so as to control the reflected electric field (E rx I / E in It is preferable to set it to an optimal value so that θ becomes a minimum value.

[0044] The reflected and scattered wave angle (i.e., the propagation direction of the scattered wave) θ for frontal incidence (θi = 0) n can be expressed by the following equation (4) (Mathematical Expression 5).

[0045]

number

[0046] FIG. 4 shows the relationship between the period L of the convex portion 2 normalized by the wavelength λ, i.e., L / λ, on the horizontal axis and the reflection / scattering angle θ n The vertical axis shows the results of the calculation of the scattering angle θ of the scattered wave. The smaller the period L (normalized L / λ) of the protrusions 2, the larger the opening angle from the incident direction becomes for the scattered wave with n=±1, and the wave is scattered over a wider angle. Figure 5 shows the reflection / scattering angle θ of the scattered wave in the case of such frontal incidence.n 5 shows a radio wave scattering direction control plate 10, but the same applies to the radio wave scattering direction control plate 1.

[0047] In FIG. 4, when the period L of the convex portion 2 is changed in the range of 1λ to 2λ, the reflection scattering angle θ n The elevation angle of the projections 2 changes between 30° and 90°, that is, in a range of 60°. Therefore, by appropriately setting the period L of the projections 2, it is possible to control the reflection / scattering angle of the scattered wave.

[0048] FIG. 6 shows the relationship between the period L of the convex portions 2 normalized by the wavelength λ, i.e., L / λ, plotted on the horizontal axis, and the reflected electric field and the scattered electric field (E rx I / E in ) are shown in two graphs, one above the other, which show the results of calculating the reflection coefficient. Here, the height d of the convex portion 2 is set to λ / 4, where the reflection coefficient is at its minimum value, and the width ratio of the concave portion 3 to the convex portion 2 is set to 1:1. The upper graph in Figure 6 shows the reflected electric field for n=0, and the lower graph shows the scattered electric field for n=±1. Since n +1 and -1 are the same value, they are the same graph.

[0049] As shown in the upper graph of Figure 6, the reflected electric field decreases almost monotonically with increasing L / λ, and especially between about 1.5 and 2.0, the reflected electric field is suppressed to 5% or less of the case of perfect reflection, and the remaining 95% is all scattered, and as shown in the lower graph of Figure 6, the scattered electric field is stable at almost the maximum value due to the conservation of energy. At this time, as can be seen from Figure 4 shown above, the scattering direction is controlled in the range of 30° to 41°. In this way, if L / λ is set between about 1.5 and 2.0, reflection is particularly suppressed and the amount of scattering increases, which is effective for controlling the scattering direction.

[0050] Figure 7 shows the incidence angle θ of the incident wave in the case of oblique incidence. i and the reflection / scattering angle θ of the scattered wave n 7 shows the radio wave scattering direction control plate 10, but the same applies to the radio wave scattering direction control plate 1. Also, FIG. 8 shows the angle of incidence θ when the period L of the protrusions 2 is set to 1.5λ and the incident wave is obliquely incident.i and the reflection scattering angle θ n This is a graph showing the relationship between oblique incidence (θ i >0), the scattered wave is scattered in a direction different from the direction of specular reflection according to the law of reflection, and by optimally adjusting the period L of the convex parts 2 and the height d of the convex parts 2, it is possible to suppress specular reflection and control the scattering direction. Thus, in the case of oblique incidence, the scattering angle θ of the scattered wave (n=-1) n is the oblique incidence angle θ i In the example of Figure 8, the scattering direction can be controlled within the range of -42° to +19°.

[0051] Fig. 9 is a vertical cross-sectional view of a radio wave scattering direction control plate 11 according to the second embodiment, which is manufactured by sheet metal processing, like the radio wave scattering direction control plate 1 of the first embodiment shown in Fig. 1(a). This radio wave scattering direction control plate 11 has the front ends of the convex parts 2 in the same plane, and has a structure in which the height of the convex parts 2 or the depth of the concave parts 3 includes two different heights d1 and d2.

[0052] Fig. 10 is a vertical cross-sectional view of a radio wave scattering direction control plate 12 according to the third embodiment, which is manufactured by sheet metal processing, like the radio wave scattering direction control plate 1 of the first embodiment shown in Fig. 1(a). This radio wave scattering direction control plate 12 has the same bottom surface of the recesses 3, and has a structure in which the height of the protrusions 2 or the depth of the recesses 3 include two different heights d1 and d2.

[0053] As shown in Fig. 2 in the first embodiment, the minimum point of the strength of the reflected electric field is determined according to the height d of the convex portion 2 normalized by the wavelength λ (i.e., d / λ), but since the minimum point has a width, if the height d (d / λ) of the convex portion 2 changes, the reflected electric field will deviate from the minimum value and become stronger. However, according to the radio wave scattering direction control plates 11 and 12 of the second and third embodiments, since two or more types of dimensions (heights d1, d2) are provided for the height of the convex portion 2 or the depth of the concave portion 3, it is possible to shift and provide multiple minimum points, and the bandwidth (fractional bandwidth) can be expanded. Furthermore, by expanding the bandwidth (fractional bandwidth), it becomes possible to control the scattering direction while suppressing reflection for a wider frequency range.

[0054] As described above, the radio wave scattering direction control plates 1, 10, 11, 12 according to each embodiment are made of a conductor and have a repeated sawtooth structure consisting of rectangular recesses 3 and protrusions 2, so that the scattering direction of radio waves can be arbitrarily controlled by changing the dimensions of the recesses 3 or protrusions 2. By arranging such radio wave scattering direction control plates 1, 10, 11, 12 on structures near radars or transmitting / receiving antennas for outdoor measurement or on clutter sources near targets, unwanted reflections can be reduced and highly accurate target signals can be obtained.

[0055] Furthermore, the radio wave scattering direction control plates 1, 10, 11, and 12 according to each embodiment are lighter and easier to handle than thick outdoor radio wave absorbers, and because they are made of metal, they do not deteriorate due to sunlight. Even if deterioration over time due to wind and rain is expected, this can be prevented by applying paint that does not affect the radio wave characteristics, which is the same maintenance method as for the roofs and shutters of ordinary houses.

[0056] In addition, the radio wave scattering direction control plates 1, 10, 11, and 12 according to the respective embodiments do not need to be tilted at an angle, so they require a small installation area and are advantageous in terms of safety. Furthermore, they can be easily and inexpensively manufactured by only uneven sheet metal processing, without relying on precise and expensive reflect arrays or metasurfaces. [Explanation of symbols]

[0057] 1, 10, 11, 12...Radio wave scattering direction control plate 2...Convex part (tooth part) 3…Slot 4…Dielectric sheet

Claims

1. A radio wave scattering direction control plate comprising a conductor and having a structure in which rectangular recesses and protrusions continuing in a first direction are alternately and repeatedly arranged in a second direction perpendicular to the first direction.

2. 2. The radio wave scattering direction control plate according to claim 1, wherein a dielectric sheet is provided on the surface of said protrusions so as to cover said recesses.

3. 2. The radio wave scattering direction control plate according to claim 1, wherein at least one of a dielectric material and a magnetic material is provided inside said recess.

4. 2. The radio wave scattering direction control plate according to claim 1, wherein the depth of the recess or the height of the protrusion is set to a value within a predetermined range including a quarter of the wavelength of the radio wave.

5. The radio wave scattering direction control plate according to claim 1, characterized in that the ratio of the length of the recess in the second direction to the total length of the recess and the protrusion in the second direction is set to a value within a predetermined range including 0.

5.

6. The radio wave scattering direction control plate according to claim 1, characterized in that the total length of the adjacent concave and convex portions in the second direction is set to a value within the range of one to two wavelengths of radio waves.

7. 2. The radio wave scattering direction control plate according to claim 1, wherein the depths of two adjacent recesses in the second direction or the heights of two adjacent protrusions in the second direction are different from each other.

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