JP4338460B2 - Radio wave absorber and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic wave absorber used for an anechoic chamber, an anechoic box, an electromagnetic wave absorption partition, and the like, and a manufacturing method thereof.
[0002]
[Prior art]
Conventionally, an anechoic chamber has been used as a space for evaluating performance such as antenna directivity and gain. In recent years, an electronic darkroom has been actively used as a test site for measuring electromagnetic noise emitted from electronic equipment and evaluating the resistance of electronic equipment to external electromagnetic noise. A radio wave absorber that absorbs incident radio waves and suppresses reflection is disposed on the inner wall of the anechoic chamber.
[0003]
As a radio wave absorber, a radio wave absorber made of a material obtained by mixing or impregnating a conductive material such as carbon with a base material such as foamed polystyrene or foamed urethane and including a tapered portion having a tapered shape is widely used.
[0004]
Patent Document 1 discloses a radio wave absorber that includes a heat-resistant base material and a conductive material as a radio wave absorber corresponding to high-power radio waves, and has a tapered portion in which an opening for heat dissipation is arranged on the surface. The body is listed.
[0005]
In these radio wave absorbers, a conductive material that is a radio wave absorbing material is held using a base material and disposed in a space. Moreover, in these wave absorbers, by adopting a tapered shape, the impedance can be gradually changed from the free space to the back side of the wave absorber to absorb the waves while suppressing the reflection at the wave absorber. I am doing so.
[0006]
Generally, in the radio wave absorber, the longer the wavelength of radio waves to be absorbed, that is, the lower the frequency, the greater the length of the radio wave absorber in the radio wave incident direction. For this reason, for example, the length of the electromagnetic wave absorber provided in the electromagnetic wave noise measurement anechoic chamber used in a low frequency band whose lower limit is about 30 MHz may be several meters. Therefore, a technique for reducing the length of the radio wave absorber by combining the radio wave absorber and the ferrite sintered body has been developed.
[0007]
By the way, the shape of the tapered portion of the radio wave absorber has many types such as a pyramid shape and a wedge shape. In the tapered portion, if the shape is different, the aspect of the change in the cross-sectional area of the cross section perpendicular to the radio wave incident direction with respect to the change in the position in the radio wave incident direction is different, and as a result, the effective material constant for the change in the position The mode of change is different. For this reason, in a radio wave absorber having a tapered portion, the radio wave absorption characteristics vary depending on the shape of the tapered portion.
[0008]
For this reason, conventionally, for example, as disclosed in Patent Documents 2 to 4, various studies on optimization of the shape of the tapered portion of the radio wave absorber have been made.
[0009]
[Patent Document 1]
JP 2003-115633 A
[Patent Document 2]
Japanese Examined Patent Publication No. 62-5360
[Patent Document 3]
Japanese Patent Publication No. 63-32278
[Patent Document 4]
Japanese Patent No. 3291855
[0010]
[Problems to be solved by the invention]
As a method of manufacturing a radio wave absorber having a tapered portion, there is a method of manufacturing a rectangular parallelepiped block-shaped radio wave absorber and cutting it. However, in this method, a large amount of scrap material is generated by cutting, so that the loss of material cost is large and there may be a problem in discarding the scrap material. Further, the above method has a problem that it is difficult to manufacture the radio wave absorber when the shape of the tapered portion is complicated.
[0011]
Further, depending on the type of base material such as a base material made of foamed polystyrene, the radio wave absorber can be formed by a mold. In this case, no end material is generated, and a radio wave absorber having a tapered portion with a complicated shape can be manufactured relatively easily. However, in this case, each time a radio wave absorber with a different shape or length is manufactured, a mold must be manufactured, and there is a problem that extra cost and time are required to manufacture the mold. There is.
[0012]
The present invention has been made in view of such problems, and an object of the present invention is to provide a radio wave absorber that can be easily manufactured and can reduce material loss while including a tapered portion having a tapered shape, and a method for manufacturing the same. It is to provide.
[0013]
[Means for Solving the Problems]
The radio wave absorber according to the present invention includes a structure formed by winding a thin plate-like radio wave absorber, and the structure includes a tapered portion having a tapered shape that becomes thinner toward the end on the radio wave arrival side. It is a waste. The radio wave absorber of the present invention can be easily manufactured by winding a thin plate wave absorber.
[0014]
In the radio wave absorber of the present invention, the radio wave absorber before being wound may have an edge inclined with respect to the rotation axis when the radio wave absorber is wound.
[0015]
In the radio wave absorber of the present invention, the radio wave absorber may have an opening. In the radio wave absorber of the present invention, the radio wave absorber may have a plurality of openings that penetrate in a direction parallel to the surface of the radio wave absorber. The plurality of openings may penetrate in a direction parallel to the rotation axis when winding the radio wave absorber. The plurality of openings may be formed in a corrugated shape.
[0016]
In the radio wave absorber of the present invention, the radio wave absorber may include a base material and a radio wave absorption material, and the base material may be heat resistant or nonflammable.
[0017]
In the radio wave absorber of the present invention, the shape of the end surface of the structure opposite to the end on the radio wave arrival side may be rectangular.
[0018]
The radio wave absorber of the present invention may further include a base member having a recess into which the structure is fitted, and the structure may be fitted to the recess and attached to the base member. The base member may include a radio wave absorbing material.
[0019]
In addition, the radio wave absorber of the present invention may further include a ferrite sintered body disposed so as to face the end surface of the structure opposite to the end on the radio wave arrival side.
[0020]
The method for manufacturing a radio wave absorber according to the present invention includes a step of producing a thin plate-like radio wave absorber and a step of forming a structure by winding the radio wave absorber.
[0021]
In the present application, “heat resistance” means that the heat resistance temperature is 150 ° C. or higher. The heat resistant temperature of the heat resistant substrate is more preferably 200 ° C. or higher, and further preferably 300 ° C. or higher. Moreover, if a heat resistant base material passes the nonflammability test or the exothermic test prescribed | regulated by a building standard law, it is still more preferable on safety.
[0022]
In addition, in this application, “nonflammable” means that it has a nonflammable performance that conforms to the nonflammable material specified in the Building Standard Law, and that is equivalent to the nonflammable performance of the nonflammable material specified in the Building Standard Law. Say that you have.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing an example of a configuration of a radio wave absorber according to an embodiment of the present invention. 1A is a side view of the radio wave absorber, and FIG. 1B is a bottom view of the radio wave absorber. In the present embodiment, the bottom surface of the radio wave absorber refers to the end surface of the radio wave absorber opposite to the end on the radio wave arrival side. As shown in FIG. 1, the radio wave absorber 1 according to the present embodiment includes a structure 2 formed by winding a thin plate-like radio wave absorber 3. The radio wave absorber 3 includes a base material and a radio wave absorber material. As the radio wave absorbing material, for example, a conductive material such as carbon black, carbon graphite, or carbon fiber, or a magnetic material such as ferrite is used. In the following description, the incident direction of the radio wave 20 is referred to as the Z direction. The structure 2 includes a tapered portion having a tapered shape that becomes thinner as it approaches the end on the radio wave arrival side. Note that the entire structure 2 shown in FIG. 1 is a tapered portion.
[0024]
FIG. 2 is an explanatory diagram showing the shape of the radio wave absorber 3 constituting the structure 2 shown in FIG. 1 before being wound. 2A is a plan view of the radio wave absorber 3, and FIG. 2B is a side view of the radio wave absorber 3. As shown in FIG. 2, the radio wave absorber 3 has three edges 4, 5, and 6. The edges 4 and 5 are linear. The edge 6 may be linear or curved. FIG. 2 shows an example in which the edge 6 is curved. The edge 4 is arranged in parallel to the rotation axis 7 when the radio wave absorber 3 is wound. The edge 5 is disposed perpendicular to the rotation axis 7 when the radio wave absorber 3 is wound. One end of the edge 4 and one end of the edge 5 are connected to each other. One end of the edge 6 is connected to the other end of the edge 4, and the other end of the edge 6 is connected to the other end of the edge 5. The edge 6 is inclined with respect to the rotation shaft 7 when the radio wave absorber 3 is wound. The rotating shaft 7 is parallel to the Z direction.
[0025]
The method for manufacturing the radio wave absorber 1 according to the present embodiment includes a step of producing the radio wave absorber 3 and a step of forming the structure 2 by winding the radio wave absorber 3.
[0026]
The material of the radio wave absorber 3 is preferably a material that can be easily wound and bent. As such a material, for example, there is a plate-like material in which a radio wave absorbing material such as carbon or ferrite powder is held on a base material made of a material that is easily bent such as paper, rubber, or resin. The radio wave absorber 3 does not necessarily have a uniform flat plate shape, and may be a mat shape using fibers, for example. Further, the radio wave absorber 3 may have an opening as will be described later.
[0027]
The base material of the radio wave absorber 3 may be heat resistant or incombustible. As such a base material, for example, a substrate formed by laminating sheets made of a hydrous inorganic compound such as sepiolite or aluminum hydroxide in a corrugated shape (wave shape) is preferable from the viewpoint of production and cost. By making the base material of the radio wave absorber 3 heat resistant or incombustible, the radio wave absorber 1 can be used for applications that absorb high-power radio waves.
[0028]
Examples of the method for holding the radio wave absorbing material on the thin plate-shaped wave absorbing material 3 include a method of forming the thin plate-shaped wave absorbing material 3 using a material including a base material and a radio wave absorbing material, and a base material. There is a method in which a radio wave absorbing material is attached to the surface of a thin plate made of a material.
[0029]
The radio wave absorber 3 is densely wound around the rotation shaft 7 so that the edge 4 is on the inside as indicated by an arrow 8 in FIG. As a result, as shown in FIG. 1, the electromagnetic wave absorbing material 3 forms a tapered structure 2 close to a conical shape. The shape of the bottom surface of the structure 2 shown in FIG. 1, that is, the bottom surface of the radio wave absorber 1 is circular.
[0030]
Here, as shown in FIG. 1, the length of the structure 2 in the Z direction is A, and the diameter of the bottom surface of the structure 2 is B. Further, as shown in FIG. 2, the length of the edge 4 is a, the length of the edge 5 is b, and the thickness of the radio wave absorber 3 is t.
[0031]
The length A in the Z direction of the structure 2 is equal to the length a of the edge 4 of the radio wave absorber 3. The diameter B of the bottom surface of the structure 2 is determined by the length b of the edge 5 and the thickness t of the radio wave absorber 3. When the radio wave absorber 3 is densely wound, between B, b, and t, π · (B / 2) ² ≈b · t
[0032]
As the thickness t of the radio wave absorber 3 is reduced, the shape of the side surface of the tapered portion of the structure 2 becomes smoother, which is advantageous in terms of radio wave absorption characteristics of the radio wave absorber 1 at a high frequency. However, as the thickness t of the radio wave absorber 3 is reduced, the length b of the edge 5 necessary for manufacturing the structure 2 having the bottom surface having the same diameter B is increased and the radio wave absorber 3 is wound. The number of times also increases. Therefore, reducing the thickness t of the radio wave absorber 3 is disadvantageous in terms of manufacturing the radio wave absorber 1.
[0033]
By the way, although the electromagnetic wave absorber 3 shown in FIG. 2 does not have an opening part, in this Embodiment, the electromagnetic wave absorber 3 may have an opening part. Hereinafter, first to fifth examples of the radio wave absorber 3 having an opening will be described with reference to FIGS. 3 to 7. 3 to 7, (a) is a plan view of the radio wave absorber 3, (b) is a side view of the radio wave absorber 3, and (c) is an enlarged part of the plan view shown in (a). Explanatory drawing shown, (d) represents explanatory drawing which expands and shows a part of side view shown in (b).
[0034]
FIG. 3 shows a first example of the radio wave absorber 3 having an opening. In the first example, the radio wave absorber 3 has a plurality of cylindrical openings 51 penetrating in a direction perpendicular to the surface thereof. The shape, size, and number of the openings 51 can be arbitrarily set within a range in which the strength of the radio wave absorber 3 and the structure 2 can be maintained.
[0035]
FIG. 4 shows a second example of the radio wave absorber 3 having an opening. In the second example, the radio wave absorber 3 has a plurality of cylindrical openings 52 penetrating in a direction parallel to the surface thereof. In particular, the plurality of openings 52 penetrate in a direction parallel to the rotation shaft 7.
[0036]
FIG. 5 shows a third example of the radio wave absorber 3 having an opening. In the third example, the radio wave absorber 3 has a plurality of openings 53 formed in a corrugated shape. The plurality of openings 53 penetrates in a direction parallel to the surface of the radio wave absorber 3, particularly in a direction parallel to the rotation shaft 7. As shown in FIG. 5D, the radio wave absorber 3 in the third example is configured by sandwiching a corrugated sheet 3a between two flat sheets 3b and 3c.
[0037]
FIG. 6 shows a fourth example of the radio wave absorber 3 having an opening. In the fourth example, the radio wave absorber 3 has a plurality of openings 54 formed in a corrugated shape (wave shape). The plurality of openings 54 penetrates in a direction parallel to the surface of the radio wave absorber 3, particularly in a direction parallel to the rotation shaft 7. As shown in FIG. 6D, the radio wave absorber 3 in the fourth example is configured by superimposing a corrugated sheet 3a and a single flat sheet 3b. In the structure 2 formed using the radio wave absorber 3 in the fourth example, the sheet 3a appears on the outer peripheral portion.
[0038]
FIG. 7 shows a fifth example of the radio wave absorber 3 having an opening. In the fifth example, the radio wave absorber 3 has a plurality of openings 55 formed in a corrugated shape (wave shape). The plurality of openings 55 penetrates in a direction parallel to the surface of the radio wave absorber 3, particularly in a direction parallel to the rotation shaft 7. As shown in FIG. 7D, the radio wave absorber 3 in the fifth example is configured by superimposing a corrugated sheet 3a and a single flat sheet 3c. In the structure 2 formed using the radio wave absorber 3 in the fifth example, the sheet 3c appears on the outer peripheral portion.
[0039]
As in the first to fifth examples, by making the structure 2 using the radio wave absorber 3 having an opening, the radio wave absorber 1 can be reduced in weight and the heat radiation of the radio wave absorber 1 can be reduced. It becomes easy to cope with high-power radio waves because of improved performance.
[0040]
Further, as in the second to fifth examples, the structure 2 is manufactured by using the radio wave absorber 3 having a plurality of openings penetrating in the direction parallel to the surface of the radio wave absorber 3. In addition to the effect, there is an effect that the strength of the radio wave absorber 3 and the structure 2 can be increased. Furthermore, when the plurality of openings penetrates in the direction parallel to the rotation shaft 7, the radio wave absorber 3 can be easily wound. In this case, the radio wave absorber 1 is advantageous in terms of radio wave absorption characteristics. When the radio wave absorber 1 is viewed from the radio wave arrival side, there are many openings on the surface of the radio wave absorber 1. This is because a large amount of radio waves can be taken into the absorber 1.
[0041]
Next, the arrangement of the plurality of radio wave absorbers 1 will be described. FIG. 8 is an explanatory diagram showing an example of the arrangement of the plurality of radio wave absorbers 1. 8A is a front view of the plurality of wave absorbers 1, and FIG. 8B is a side view of the plurality of wave absorbers 1. In the example shown in FIG. 8, the shape of the bottom surface of the structure 2, that is, the bottom surface of the radio wave absorber 1 is circular. In this example, the plurality of wave absorbers 1 are arranged side by side on the wall surface so that the bottom surface of the wave absorber 1 is in contact with a wall surface (not shown) in an anechoic chamber or the like. In this example, as shown in FIG. 8 (a), when viewed from the radio wave arrival side, the end of each radio wave absorber 1 on the radio wave arrival side is arranged at the intersection of the grid. A radio wave absorber 1 is disposed. In this example, since the shape of the bottom surface of the radio wave absorber 1 is circular, a gap 11 is generated between the plurality of radio wave absorbers 1. In this gap 11, the wall surface is exposed. The wall surface on which the radio wave absorber 1 is provided is often a metal surface. In this case, when the gap 11 is large, reflection of radio waves on the wall surface particularly in a high frequency region becomes a problem.
[0042]
9 and 10 show examples of the arrangement of the radio wave absorber 1 that can avoid the above problem. 9 and 10 are front views of a plurality of radio wave absorbers, respectively. In the example shown in FIG. 9, the radio wave absorber 12 having a small bottom surface is disposed at the position of the gap 11 in FIG. The radio wave absorber 12 is smaller than the radio wave absorber 1, but its basic configuration and manufacturing method are the same as those of the radio wave absorber 1. According to the example shown in FIG. 9, the size of the gap 13 generated between the radio wave absorbers 1 and 12 can be made significantly smaller than the size of the gap 11 in FIG. Thereby, reflection of the radio wave on the wall surface can be suppressed.
[0043]
In the example shown in FIG. 10, a plurality of radio wave absorbers 1 are arranged so that six radio wave absorbers 1 surround a single radio wave absorber 1. According to this example, the size of the gap 11 generated between the plurality of radio wave absorbers 1 can be made significantly smaller than the size of the gap 11 in FIG. Thereby, reflection of the radio wave on the wall surface can be suppressed.
[0044]
FIG. 11 shows another example of the configuration of the radio wave absorber 1. 11A is a side view of the radio wave absorber 1, and FIG. 11B is a bottom view of the radio wave absorber 1. In the example shown in FIG. 11, the shape of the bottom surface of the structure 2, that is, the bottom surface of the radio wave absorber 1 is rectangular. By using the radio wave absorber 1 having the shape shown in FIG. 11, a plurality of radio wave absorbers 1 can be arranged side by side without any gaps on the wall surface. Thereby, reflection of the radio wave on the wall surface can be suppressed.
[0045]
FIG. 12 is an explanatory diagram showing still another example of the configuration of the radio wave absorber according to the present embodiment. 12A is a front view of the radio wave absorber, and FIG. 12B is a side view of the radio wave absorber. The radio wave absorber 21 shown in FIG. 12 includes a plurality of, for example, nine structures 2 and a base member 15 having a plurality of recesses 16 into which portions near the bottom surface of these structures 2 are fitted. . In addition, in FIG.12 (b), about the base member 15, the cross section is shown. The structure 2 is fitted to the recess 16 and attached to the base member 15. According to the radio wave absorber 21 having such a base member 15, the structure 2 can be easily attached to a wall surface in an anechoic chamber or the like.
[0046]
The base member 15 may be made of a radio wave transmitting material. In this case, the base member 15 can be prevented from affecting the radio wave absorption characteristics of the structure 2.
[0047]
The base member 15 may include a radio wave absorbing material. In this case, when a plurality of structures 2 are attached to the wall surface, even if there are gaps 11 between the plurality of structure bodies 2, reflection of radio waves on the wall surface can be suppressed.
[0048]
FIG. 13 is an explanatory diagram showing still another example of the configuration of the radio wave absorber according to the present embodiment. 13A is a front view of the radio wave absorber, and FIG. 13B is a side view of the radio wave absorber. The radio wave absorber 31 shown in FIG. 13 includes a plurality of, for example, nine structures 2, and a plurality of ferrite sintered bodies 32 bonded to each structure 2 so as to face the bottom surface of each structure 2. The ferrite sintered body 32 includes a metal plate 33 as a radio wave reflector disposed on the opposite side of the structure 2. For example, the ferrite sintered body 32 is formed in a flat plate shape having a rectangular planar shape. Moreover, the ferrite sintered body 32 has a radio wave absorption function. The plurality of sets of structures 2 and ferrite sintered bodies 32 are arranged side by side on the metal plate 33 with no gap so that the ferrite sintered body 32 contacts the metal plate 33.
[0049]
In the radio wave absorber 31 shown in FIG. 13, radio waves are absorbed by the structure 2 and the ferrite sintered body 32. Therefore, according to the radio wave absorber 31, the length of the radio wave absorber 31 in the radio wave incident direction is made smaller than that of the radio wave absorber made only of the structure 2 in a wider frequency band including lower frequencies. It becomes possible to absorb radio waves.
[0050]
Note that the radio wave absorber 31 shown in FIG. 13 includes a plurality of sets of structures 2, a ferrite sintered body 32, and a single metal plate 33. However, one set of the structural body 2 and the ferrite sintered body 32 and one metal plate 33 may constitute one radio wave absorber.
[0051]
Further, the metal plate 33 may be removed from the radio wave absorber 31 shown in FIG. 13 and the structure 2 and the ferrite sintered body 32 may be directly attached to a wall surface in an anechoic chamber or the like.
[0052]
Next, the operation of the radio wave absorber (1, 12, 21, 31) according to the present embodiment will be described. In the radio wave absorber according to the present embodiment, the radio wave is absorbed by the structure 2 constituted by the radio wave absorber 3. In this radio wave absorber, since the structure 2 includes a tapered portion having a taper shape, the impedance is gradually changed from the free space to the back side of the radio wave absorber, while suppressing reflection at the radio wave absorber. Can be absorbed.
[0053]
The radio wave absorber according to the present embodiment can be used as a radio wave absorber in an anechoic chamber, an anechoic box, a radio wave absorption panel, or a radio wave absorption partition. The anechoic chamber is used for measuring the radiation noise intensity of a device that generates noise that causes electromagnetic interference to other devices, or for testing malfunctions by irradiating electronic devices with electromagnetic waves of strong electromagnetic fields. The anechoic chamber is also used for various experiments that emit radio waves, such as radar evaluation. The anechoic box is used for measuring antenna characteristics of a mobile radio terminal or the like, or measuring the influence of an electromagnetic wave on an electronic device or the like. The anechoic box is distinguished from an anechoic chamber in which a person may work, in that a person does not work in the box. In both the anechoic box and the anechoic chamber, a radio wave absorber is disposed on at least a part of the inner wall. Each of the radio wave absorption panel and the radio wave absorption screen is a plate-like structure for absorbing radio waves. The radio wave absorption panel is used by being attached to another structure, and the radio wave absorption screen is used alone. Both the radio wave absorption panel and the radio wave absorption screen include a radio wave absorber.
[0054]
In the radio wave absorber according to the present embodiment, the structure 2 including the tapered portion is formed by winding the thin plate-like radio wave absorber 3. Therefore, according to the present embodiment, it is possible to easily manufacture a radio wave absorber including a tapered portion having a tapered shape without requiring cutting or molding using a mold, and to reduce material loss. Can be reduced.
[0055]
Moreover, according to this Embodiment, the electromagnetic wave absorber of various lengths and shapes can be manufactured only by changing the shape of the electromagnetic wave absorber 3 before being wound. Therefore, according to the present embodiment, radio wave absorbers having various radio wave absorption characteristics can be easily realized.
[0056]
In the present embodiment, in particular, the radio wave absorption characteristics of the radio wave absorber can be changed by changing the shape of the edge 6 of the radio wave absorber 3. That is, when the shape of the edge 6 changes, the shape of the tapered portion in the structure 2 changes. When the shape of the tapered portion changes, the aspect of the change in the cross-sectional area of the cross section perpendicular to the radio wave incident direction with respect to the change in the position in the radio wave incident direction is different in the taper portion. The mode of change of the material constant is different. From the above, the radio wave absorption characteristics of the radio wave absorber change depending on the shape of the edge 6.
[0057]
Here, the relationship between the shape of the edge 6 of the radio wave absorber 3 and the shape of the tapered portion of the structure 2 will be described in detail. 14A is a side view of the radio wave absorber 1, FIG. 14B is a plan view of the radio wave absorber 3, and FIG. 14C is a cross-sectional view taken along the line AA of the radio wave absorber 1 shown in FIG. It represents. Here, the position in the structure 2 in the direction of radio wave incidence is represented by the symbol z. z is 0 at the position of the end of the structure 2 on the radio wave arrival side, and has a positive value on the far side of the radio wave absorber 1 from this position. Further, the width of the radio wave absorber 3 at an arbitrary position z is W (z). Note that the width of the radio wave absorber 3 refers to the length of the radio wave absorber 3 in a direction perpendicular to the rotation axis 7. In addition, the cross-sectional area of the cross section of the structure 2 at an arbitrary position z is S (z). This cross-sectional area S (z) is expressed by the following equation using the width W (z) and the thickness t of the radio wave absorber 3. FIG. 15 shows an example of the relationship between the position z and the cross-sectional area S (z).
[0058]
S (z) = W (z) · t
[0059]
Accordingly, by changing the shape of the edge 6 of the radio wave absorber 3, the aspect of the change in the width W (z) with respect to the change in the position z changes, and as a result, the change in the cross-sectional area S (z) with respect to the change in the position z. The mode of changes. Therefore, when the shape of the edge 6 of the radio wave absorber 3 changes, the mode of change in effective material constant (for example, dielectric constant) with respect to the change in the position z in the structure 2 changes. From the above, the radio wave absorption characteristics of the radio wave absorber 1 vary depending on the shape of the edge 6.
[0060]
Hereinafter, first to sixth examples of the shapes of the radio wave absorber 3 and the structure 2 will be described.
[0061]
FIG. 2 shows a first example of the shape of the radio wave absorber 3. In the radio wave absorber 3 shown in FIG. 2, the shape of the edge 6 is a quadratic curve. In this case, the relationship between the position z and the cross-sectional area S (z) is also represented by a quadratic curve. In this case, the structure 2 has a substantially conical shape as shown in FIG.
[0062]
16 and 17 show a second example of the shape of the radio wave absorber 3 and the structure 2. 16 is a plan view of the radio wave absorber 3, and FIG. 17 is a side view of the structure 2. In the radio wave absorber 3 shown in FIG. 16, the shape of the edge 6 is a cubic curve. In this case, the relationship between the position z and the cross-sectional area S (z) is also represented by a cubic curve. In this case, as shown in FIG. 17, the shape of the structure 2 is a shape having a recessed side surface compared to the conical shape.
[0063]
18 and 19 show a third example of the shape of the radio wave absorber 3 and the structure 2. 18 is a plan view of the radio wave absorber 3, and FIG. 19 is a side view of the structure 2. In the radio wave absorber 3 shown in FIG. 18, the shape of the edge 6 is a straight line. In this case, the relationship between the position z and the cross-sectional area S (z) is also represented by a straight line. In this case, as shown in FIG. 19, the shape of the structure 2 is a shape whose side surface swells compared to the conical shape.
[0064]
20 and 21 show a fourth example of the shapes of the radio wave absorber 3 and the structure 2. 20 is a plan view of the radio wave absorber 3, and FIG. 21 is a side view of the structure 2. In the radio wave absorber 3 shown in FIG. 20, the shape of the edge 6 is a 0.8th order curve. In this case, the relationship between the position z and the cross-sectional area S (z) is also represented by a 0.8th order curve. In this case, as shown in FIG. 21, the shape of the structure 2 is a shape in which the side surface is further expanded as compared with the structure 2 shown in FIG.
[0065]
22 and 23 show a fifth example of the shapes of the radio wave absorber 3 and the structure 2. FIG. 22 is a plan view of the radio wave absorber 3, and FIG. 23 is a side view of the structure 2. In the radio wave absorber 3 shown in FIG. 22, z is 0 to z. ₁ (Z ₁ In the range of <a), the shape of the edge 6 is a quadratic curve. Moreover, in this electromagnetic wave absorber 3, z is z ₁ In the range of ~ a, W (z) = b. In this case, the shape of the structure 2 is such that z is 0 to z as shown in FIG. ₁ In the range of, it becomes conical and z is z ₁ In the range of ~ a, it is cylindrical.
[0066]
24 and 25 show a sixth example of the shape of the radio wave absorber 3 and the structure 2. FIG. 24 is a plan view of the radio wave absorber 3, and FIG. 25 is a side view of the structure 2. The radio wave absorber 3 shown in FIG. 24 has a shape in which a part of the radio wave absorber 3 shown in FIG. 2 is cut away. Specifically, the radio wave absorber 3 shown in FIG. 24 has a shape in which the portion in the vicinity of the intersection between the edge 4 and the edge 5 is cut out in the radio wave absorber 3 shown in FIG. . As a result, in the radio wave absorber 3 shown in FIG. 24, the edge 9 that connects the end of the edge 4 near the intersection and the end of the edge 5 near the intersection is newly formed. The shape of the edge 9 is, for example, a quadratic curve. In this case, as shown in FIG. 25, the structure 2 has a shape having a hollow portion 37 in the vicinity of the bottom surface. The outer shape of the structure 2 shown in FIG. 25 is the same as that of the structure 2 shown in FIG. According to the sixth example, the structure 2 can be reduced in weight.
[0067]
Thus, in this Embodiment, the electromagnetic wave absorber 1 of various shapes can be manufactured only by changing the shape of the electromagnetic wave absorber 3 before being wound. More specifically, in the present embodiment, the length a of the edge 4, the length b of the edge 5, the thickness t of the radio wave absorber 3, and the width W of the radio wave absorber 3 in the radio wave absorber 3. The electromagnetic wave absorbers having various shapes in which at least one of the shape of the side surface of the tapered portion, the length A, and the diameter B of the bottom surface is different only by changing at least one of the changes of the position z to the position z. 1 can be manufactured.
[0068]
Hereinafter, configurations and characteristics of examples in the present embodiment will be described.
[First embodiment]
In this example, first, a sheet having the structure shown in FIG. 6 was prepared using sheets 3a and 3b made of a base material mainly composed of sepiolite. This plate member was manufactured by cutting so that the shape of the edge 6 in FIG. 6 was a quadratic curve, and a = 300 mm, b = about 1500 mm, and t = 5 mm.
[0069]
Next, a coating material containing carbon black and an inorganic binder was spray-coated on the surface of the plate material to produce the radio wave absorber 3 having the structure shown in FIG. The amount of carbon black attached was 3 g per liter of the volume of the radio wave absorber 3. Next, the radio wave absorber 3 was wound to produce the structure 2 as shown in FIG. The radio wave absorber 1 has dimensions of A = 300 mm and B = 100 mm, and has a shape close to a conical shape.
[0070]
Next, the radio wave absorption performance of the manufactured radio wave absorber 1 was measured as follows. That is, first, as shown in FIG. 26, nine manufactured radio wave absorbers 1 are attached to the metal plate 41 such that their bottom surfaces are in contact with the metal plate 41, and the aggregate of the radio wave absorbers 1 is assembled. Was made. In FIG. 26, (a) is a front view of the aggregate of the radio wave absorber 1, and (b) is a side view of the aggregate of the radio wave absorber 1. The size of the metal plate 41 is 300 mm long and 300 mm wide. Nine radio wave absorbers 1 were arranged in three rows and three rows. Next, the radio wave absorption performance of the structure composed of the nine radio wave absorbers 1 and the metal plate 41 was measured in an anechoic chamber. In the radio wave absorption performance, the return loss was 20 to 40 dB at a frequency of 1 to 20 GHz, but the return loss was less than 20 dB at a frequency of 20 GHz or more. This is considered to be the influence of reflection by the metal plate 41 exposed in the gap generated between the plurality of radio wave absorbers 1 as shown in FIG.
[0071]
[Second Embodiment]
FIG. 27 shows a radio wave absorber of the second embodiment. 27A is a front view of the radio wave absorber, and FIG. 27B is a side view of the radio wave absorber. The radio wave absorber 21 of the present embodiment includes nine structures 2 and a base member 15 having a plurality of recesses 16 into which portions near the bottom surface of these structures 2 are fitted. The structure 2 is fitted to the recess 16 and attached to the base member 15. The structure 2 in the present embodiment is the same as the structure 2 in the first embodiment. The base member 15 is formed of a material in which carbon black is contained in foamed polyethylene. The dimensions of the base member 15 are 350 mm in length, 350 mm in width, and 50 mm in thickness, and the depth of the recess 8 is 25 mm. Nine structures 2 were arranged in three rows and three rows.
[0072]
Next, the radio wave absorption performance of the radio wave absorber 21 of this example was measured as follows. That is, first, the radio wave absorber 21 is attached to a metal plate having a size of 350 mm in length and 350 mm in width so that the surface of the base member 15 opposite to the surface having the recess 16 is in contact with the metal plate. . Next, the radio wave absorption performance of the radio wave absorber 21 attached to the metal plate was measured in an anechoic chamber. The radio wave absorption performance was good with a return loss of 20 to 40 dB at a frequency of 1 to 110 GHz.
[0073]
In addition, this invention is not limited to the said embodiment, A various change is possible. For example, the shape of the radio wave absorber 3 and the shape of the structure 2 may be shapes other than the example shown in the embodiment.
[0074]
【The invention's effect】
As explained above, claims 1 to 10 The electromagnetic wave absorber according to any one of claims 1 to 11 In the radio wave absorber manufacturing method described above, a structure including a tapered portion having a tapered shape is formed by winding a thin plate-shaped radio wave absorber. Therefore, according to the present invention, it is possible to easily manufacture a radio wave absorber including a tapered portion and to reduce the loss of material. In addition, according to the present invention, it is possible to manufacture radio wave absorbers of various lengths and shapes simply by changing the shape of the radio wave absorber, and as a result, radio wave absorbers having various radio wave absorption characteristics can be easily realized. There is an effect that can be done.
[0075]
Claims 2 Or 5 According to the radio wave absorber according to any one of the above, since the radio wave absorber has an opening, the radio wave absorber can be reduced in weight and the heat dissipation of the radio wave absorber can be improved. .
[0076]
Claims 3 Or 5 In the radio wave absorber according to any one of the above, the radio wave absorber has a plurality of openings that penetrate in a direction parallel to the surface of the radio wave absorber. Thereby, according to this invention, there exists an effect that the intensity | strength of a radio wave absorber and a structure can be enlarged.
[0077]
Claims 4 In the described radio wave absorber, the radio wave absorber has a plurality of openings that penetrate in a direction parallel to the rotation axis when the radio wave absorber is wound. Thereby, according to this invention, there exists an effect that a radio wave absorber becomes easy to wind.
[0078]
Claims 6 In the described radio wave absorber, the radio wave absorber includes a base material and a radio wave absorber material, and the base material is heat resistant or nonflammable. Thereby, according to this invention, there exists an effect that it becomes possible to use an electromagnetic wave absorber for the use which absorbs an electromagnetic wave of a high electric power.
[0079]
Claims 7 In the described radio wave absorber, the shape of the end surface of the structure opposite to the end on the radio wave arrival side is rectangular. Thereby, according to this invention, there exists an effect that it becomes possible to arrange several electromagnetic wave absorbers in order without gap.
[0080]
Claims 8 Or 9 The radio wave absorber described above further includes a base member having a recess into which the structure is fitted, and the structure is fitted to the recess and attached to the base member. Thereby, according to this invention, there exists an effect that it becomes possible to attach a structure to a wall surface easily.
[0081]
Claims 9 In the described electromagnetic wave absorber, the base member includes an electromagnetic wave absorbing material. Thereby, according to this invention, when attaching a some structure to a wall surface, even if there exists a clearance gap between several structure bodies, there exists an effect that reflection of the electromagnetic wave in a wall surface can be suppressed.
[0082]
Claims 10 The described radio wave absorber further includes a ferrite sintered body disposed so as to face the end surface of the structure opposite to the end on the radio wave arrival side. Thus, according to the present invention, there is an effect that it is possible to absorb radio waves in a wider frequency band while reducing the length of the radio wave absorber in the radio wave incident direction.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an example of a configuration of a radio wave absorber according to an embodiment of the present invention.
2 is an explanatory view showing a planar shape of the radio wave absorber shown in FIG. 1. FIG.
FIG. 3 is an explanatory view showing a first example of a radio wave absorber having an opening.
FIG. 4 is an explanatory view showing a second example of a radio wave absorber having an opening.
FIG. 5 is an explanatory view showing a third example of a radio wave absorber having an opening.
FIG. 6 is an explanatory view showing a fourth example of a radio wave absorber having an opening.
FIG. 7 is an explanatory view showing a fifth example of a radio wave absorber having an opening.
FIG. 8 is an explanatory diagram showing an example of an arrangement of a plurality of radio wave absorbers.
FIG. 9 is a plan view showing another example of the arrangement of a plurality of radio wave absorbers.
FIG. 10 is a plan view showing still another example of the arrangement of a plurality of radio wave absorbers.
FIG. 11 is an explanatory diagram showing another example of the configuration of the radio wave absorber according to the embodiment of the present invention.
FIG. 12 is an explanatory diagram showing still another example of the configuration of the radio wave absorber according to the embodiment of the present invention.
FIG. 13 is an explanatory diagram showing still another example of the configuration of the radio wave absorber according to the embodiment of the present invention.
FIG. 14 is an explanatory diagram for explaining the relationship between the shape of the radio wave absorber and the shape of the tapered portion of the structure in one embodiment of the present invention.
15 is an explanatory diagram showing an example of a relationship between a position and a cross-sectional area in the structure shown in FIG. 14;
FIG. 16 is a plan view showing a second example of the shape of the radio wave absorber.
17 is a side view of a structure formed of the radio wave absorber shown in FIG.
FIG. 18 is a plan view showing a third example of the shape of the radio wave absorber.
19 is a side view of a structure formed of the radio wave absorber shown in FIG.
FIG. 20 is a plan view showing a fourth example of the shape of the radio wave absorber.
21 is a side view of a structure formed of the radio wave absorber shown in FIG.
FIG. 22 is a plan view showing a fifth example of the shape of the radio wave absorber.
23 is a side view of a structure formed of the radio wave absorber shown in FIG.
FIG. 24 is a plan view showing a sixth example of the shape of the radio wave absorber.
25 is a side view of a structure formed of the radio wave absorber shown in FIG. 24. FIG.
FIG. 26 is an explanatory diagram showing an aggregate of radio wave absorbers according to the first example of the embodiment of the present invention.
FIG. 27 is an explanatory diagram showing a radio wave absorber according to a second example of the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Radio wave absorber, 2 ... Structure, 3 ... Radio wave absorber, 4, 5, 6 ... Edge part.

Claims (11)

A structure comprising a thin plate-shaped wave absorber wound around, the structure is a wave absorber including a tapered portion having a tapered shape that becomes thinner toward the end on the radio wave arrival side ,
The electromagnetic wave absorbing material before being wound includes an edge portion disposed perpendicular to a rotation axis when the electromagnetic wave absorbing material is wound, and an edge portion inclined with respect to the rotational axis when the electromagnetic wave absorbing material is wound. An electromagnetic wave absorber comprising: The radio wave absorber, electromagnetic wave absorber according to claim 1, characterized in that it has an opening. The radio wave absorber, electromagnetic wave absorber according to claim 1, wherein a plurality of openings through in a direction parallel to the plane of the radio wave absorber. The radio wave absorber according to claim 3, wherein the plurality of openings penetrates in a direction parallel to a rotation axis when the radio wave absorber is wound. The radio wave absorber according to claim 3 or 4 , wherein the plurality of openings are formed in a corrugated shape. The radio wave absorber according to any one of claims 1 to 5 , wherein the radio wave absorber includes a base material and a radio wave absorber material, and the base material is heat resistant or nonflammable. The radio wave absorber according to any one of claims 1 to 6 , wherein a shape of an end surface of the structure opposite to the end on the radio wave arrival side is a rectangle. Furthermore, the base member which has a recessed part with which the said structure body fits is provided, The said structure body is fitted to the recessed part, and is attached to the said base member, The Claim 1 thru | or 7 characterized by the above-mentioned. Radio wave absorber. The radio wave absorber according to claim 8 , wherein the base member includes a radio wave absorbing material. Furthermore, according to any one of claims 1 to 9, characterized in that the in the structure and the wave arrival side of the end portion having opposite ferrite sintered body disposed so as to face the end face of Radio wave absorber. A method for producing the radio wave absorber according to any one of claims 1 to 10 ,
Producing the thin plate-shaped electromagnetic wave absorber;
And a step of forming the structure by winding the radio wave absorber.

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