JPH08274490A - Wave absorber - Google Patents

Abstract

PURPOSE: To provide a wave absorber which has an excellent absorbing characteristic against oblique incident waves irrespective of their directions of incidence and can be manufactured relatively easily. CONSTITUTION: A wave absorber is provided with a pedestal 10 made of a dielectric loss material and a plurality of pyramidal wave lead-in sections 15 composed of a dielectric loss material, are provided on the top faces 12 and 13 of the pedestal 10, and have nearly the same height. The pedestal 10 has a triangle pole-like shape and the three surfaces of the five surfaces constituting the triangle pole of the pedestal 10 except the two facing surfaces 11 are constituted of one bottom face 14 and two top faces 12 and 13. The wave lead-in sections 15, especially, are provided so that they can become nearly perpendicular to the bottom face 14 of the pedestal 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio wave absorber, and more particularly to a radio wave absorber for an anechoic chamber.

[0002]

2. Description of the Related Art With the development of telecommunication technology and mobile communication, the importance of an anechoic chamber as an evaluation facility is increasing. On the wall surface of this type of anechoic chamber, there are a part where a vertical incident wave is mainly incident and a part where an oblique incident wave is mainly incident. In particular, the part where the oblique incident wave is incident has high-performance oblique incident characteristics. It is required to provide an absorber.

As a radio wave absorber for an anechoic chamber, a dielectric loss material formed in a wedge shape or a quadrangular pyramid shape is often used. FIG. 9 is a perspective view showing an example of the most common radio wave absorber of this type, in which a plurality of quadrangular pyramidal radio wave introducing portions 91 are arranged on the upper surface of a plate-shaped base 90. However, the radio wave absorber having such a shape has a high absorption characteristic (reflection attenuation amount) for vertically incident waves, but has a low absorption characteristic (reflection attenuation amount) for oblique incident waves. have.

For this reason, in the conventional anechoic chamber, the length of the portion of the vertically incident electromagnetic wave absorber into which the oblique incident wave is mainly incident is made longer than the length of the portion into which the vertically incident wave is incident so that the oblique incident characteristic is improved. We are trying to secure it. However, since this means using a long-length absorber,
The effective volume of the use space is reduced, and the volume of the entire anechoic chamber must be increased. As a result, the manufacturing cost of the anechoic chamber is increased.

In order to improve the oblique incidence characteristic, a deformed quadrangular pyramid having a square cross section in front of the plate-shaped magnetic loss material and the area of which increases in the thickness direction of the absorbing member by a function similar to an exponential function. A radio wave absorber provided with a dielectric loss member having a rectangular shape has been proposed (JP-A-58-19000). However, this absorber has a problem that it is difficult to manufacture a deformed quadrangular pyramid having such a shape.

Further, a radio wave absorber has been proposed in which the wedge portion or the quadrangular pyramid portion is multi-layered to change the dielectric loss distribution in the height direction of the absorber exponentially (Japanese Patent Laid-Open No. 2-25).
No. 0398). However, this absorber has a problem that it is not easy to process because it is necessary to make several kinds of materials having different dielectric losses, and the shape of each layer is linear but complicated.

Furthermore, as shown in the perspective view of FIG. 10, 2 of the wedge-shaped pedestal portion 100 having an apex angle of about 90 °.
An oblique-incidence absorber having triangular prism-shaped radio wave introducing portions 101 arranged on two inclined surfaces has been commercialized, and has a great effect on improving the oblique-incidence characteristics (Japanese Patent Laid-Open No. 59-129494).
issue). However, in this absorber, since the electric wave introducing portion 101 has a wedge shape, the absorption characteristics differ between the TE wave in which the electric field of the incident wave is parallel to the bottom surface of the absorber and the TM wave in which the magnetic field is parallel to each other. It has the problem of being directional.

Further, as shown in the perspective view of FIG. 11 and the cross-sectional view of FIG. 12, the radio wave introducing section 1 is constructed such that the upper surface 111 of the base 110 is inclined and stands upright in a direction perpendicular to the upper surface.
A radio wave absorber provided with 12 has been proposed (US Pat. No. 4,496,950). However, in this absorber, the standing directions of the radio wave introducing portions 112 provided on both slopes 111 are significantly different from each other at the top of the absorber.
Impedance change becomes discontinuous at this part, and because the radio wave introduction part is provided perpendicular to the slope,
As will be described later, there is a problem in that the absorption characteristics have directivity and the return loss itself is low.

As described above, all of the conventional electromagnetic wave absorbers have problems in terms of their electromagnetic wave absorption performance and easiness of manufacture, and they are used as oblique incidence electromagnetic wave absorbers for obtaining a high-performance anechoic chamber. I was not satisfied.

Therefore, an object of the present invention is to provide a radio wave absorber which has excellent absorption characteristics for obliquely incident waves, has no direction in the absorption characteristics, and is relatively easy to manufacture.

[0011]

According to the present invention, a base made of a dielectric loss material and a quadrangular pyramid shape made of a dielectric loss material and provided on the upper surface of the base and having substantially equal heights to each other are provided. It has a plurality of radio wave introducing parts, and the base has a triangular prism shape, and forms the triangular prism of the base.
Three of the two surfaces, excluding two opposite surfaces, relate to a radio wave absorber having one bottom surface and two above-described top surfaces. Particularly according to the present invention, the radio wave introducing portion is provided so that the height direction thereof is substantially vertical to the bottom surface of the base.

Radio wave introducing portions are provided on two upper surfaces of a triangular prism-shaped base, and the entire absorber has a wedge shape. Therefore, an excellent scattering effect is obtained, and the absorption characteristics are improved. Further, since the radio wave introducing portions are in the shape of a quadrangular pyramid having almost the same height, the characteristic change due to the polarization is small. In particular, in the present invention, since the height direction of the radio wave introducing portion is a direction substantially perpendicular to the bottom surface of the base, not only the impedance change becomes continuous on the slope, but also large absorption characteristics for oblique incident waves are obtained, Moreover, the characteristic change due to the polarized wave is further reduced.

[0013]

The present invention will be described in detail below with reference to examples. 1 is a side view schematically showing the configuration of an embodiment of a radio wave absorber according to the present invention, and FIG. 2 is a front view thereof.

In these figures, 10 is a triangular prism-shaped base, 11 is one of two facing surfaces of the base 10, 12 and 13 are two upper surfaces (slopes) of the base 10,
Reference numerals 14 denote bottom surfaces of the base 10. Top 12
A plurality of quadrangular pyramid-shaped (pyramid-shaped) radio wave introducing portions 15 having the same height are fixedly attached (adhered in this embodiment) on the bases 13 and 13 so as to be integrated with the base 10. Each of the plurality of radio wave introducing portions 15 is attached so that its tip direction, that is, its height direction is substantially perpendicular to the bottom surface 14. The angle between the upper surfaces 12 and 13 of the base 10 is about 90 ° in this embodiment. Base 10
Also, it is clear from the figure that the entire electromagnetic wave absorber including the plurality of electromagnetic wave introducing portions 15 has a substantially wedge shape.

In this embodiment, the base 10 and the plurality of radio wave introducing portions 15 are made of the same dielectric loss material. However, the base 10 and the radio wave introducing portion 15 may be formed of dielectric loss materials having different permittivities.

In this embodiment, foamed polyethylene mixed with carbon powder is used as the dielectric loss material. In addition, as the dielectric loss material, foamed polyurethane mixed with carbon powder, foamed polyurethane impregnated in a carbon liquid, or foamed polystyrene having the surface of particles coated with carbon can be applied.

The dimensions of each part in this embodiment are as follows, for example. The base 10 has a bottom surface 14 of 600 mm ×
It has a triangular prism shape with a height of 600 mm and a height of 300 mm. In addition, each radio wave introducing unit 15 includes the upper surfaces 12 and 13 of the base 10.
94mm × 75mm, the height is 200m
It has a square pyramid shape of m. The height of the radio wave absorber as a whole is 500 mm.

FIG. 3 is a characteristic diagram showing the relationship between the installation angle θ of the radio wave introducing portion with respect to the bottom surface 14 and the return loss (radio wave absorption) for each TE wave and TM wave. However, this characteristic is an absorption characteristic with respect to an incident wave having a frequency of 2 GHz and an oblique incident angle of 65 °, and the radio wave introducing portion installation angle θ is set such that the height direction of the radio wave introducing portion is perpendicular to the bottom surface as shown in FIG. In some cases, θ = 0 °.

As is clear from FIG. 3, as in the conventional example shown in FIGS. 11 and 12, the radio wave introducing portion stands upright with respect to the bottom surface of the base (perpendicular to the slope of the base). In this case, as the angle increases, the return loss decreases and the directivity due to the TE wave and the TM wave occurs. However, as in the present invention, the height direction of the radio wave introducing portion is set to the bottom surface 1 of the base 10.
When set almost vertically to 4 (θ ≈ 0 °), both TE and TM waves have excellent absorption characteristics (40 dB or more)
And there is no difference in absorption characteristics depending on the polarization.

FIG. 4 is a characteristic diagram of the return loss with respect to frequency in the radio wave absorber of this embodiment and the radio wave absorber of FIG. 9 when an incident wave with an oblique incident angle of 65 ° is received. The solid line and the broken line show the TE wave and TM wave absorption characteristics of the electromagnetic wave absorber of this embodiment, respectively, and the alternate long and short dash line shows the TM wave absorption characteristic of the electromagnetic wave absorber of FIG. As is clear from the figure, the electromagnetic wave absorber of the present embodiment has an excellent return loss of 10 dB or more higher than that of the conventional electromagnetic wave absorber at 2 to 4 GHz.

FIG. 5 shows 2 GHz of the electromagnetic wave absorber according to this embodiment.
FIG. 6 is a characteristic diagram showing the return loss with respect to the angle of the incident wave at z for each TE wave and the TM wave. FIG. 6 shows the return loss with respect to the angle of the incident wave at 2 GHz for the conventional electromagnetic wave absorber shown in FIG. It is a characteristic view shown for each and TM wave. However, the characteristic of FIG. 6 is that when the conventional electromagnetic wave absorber of FIG. 9 is formed of the same dielectric loss material as that of this embodiment and the height of the entire electromagnetic wave absorber is 500 mm, which is the same as that of this embodiment. It is a characteristic.

As is clear from the comparison between FIG. 5 and FIG.
In the conventional electromagnetic wave absorber shown in FIG. 9, when the angle of the incident wave becomes large, the electromagnetic wave absorption amount of both TE wave and TM wave sharply decreases and the oblique incidence characteristic deteriorates. According to this, the radio wave absorption amount of 40 dB or more can be obtained in the incident angle range of 40 ° to 65 ° for both TE wave and TM wave polarization incidents. In particular, at an incident angle of 65 °, an improvement of 10 dB or more is observed as compared with the conventional electromagnetic wave absorber.

FIG. 7 shows the return loss with respect to the angle of the incident wave at 2 GHz of the conventional electromagnetic wave absorber shown in FIG.
It is a characteristic view shown according to E wave and TM wave. However, the characteristic of FIG. 7 is that the conventional electromagnetic wave absorber of FIG. 10 is formed of the same dielectric loss material as in this embodiment, and the pedestal portion 80 has a bottom surface of 600 mm.
× 600 mm, height 300 mm, radio wave introducing unit 8
1 has a wedge width of 75 mm and a height of 200 mm,
This is a characteristic when the height of the radio wave absorber as a whole is 500 mm, which is the same as that of this embodiment.

As is clear from the comparison between FIG. 5 and FIG.
The conventional radio wave absorber shown in FIG. 10 can obtain a radio wave absorption amount of 40 dB or more in the incident angle range of 40 ° to 65 ° for TE waves, but the incident angle of 6 dB for TM waves.
At 5 °, the radio wave absorption amount is as low as about 35 dB, and exhibits absorption characteristics having directivity according to the polarization. On the other hand, the radio wave absorber according to the present embodiment allows TE waves and TM waves to be absorbed. With respect to both polarization incidents, a radio wave absorption amount of 40 dB or more can be obtained in the incident angle range of 40 ° to 65 °.

FIG. 8 is a characteristic diagram showing the return loss for the TE wave and the TM wave with respect to the angle of the incident wave at 2 GHz of the conventional electromagnetic wave absorber shown in FIGS. 11 and 12. However, the characteristic of FIG. 8 is that the conventional electromagnetic wave absorber of FIGS. 11 and 12 is formed of the same dielectric loss material as that of the present embodiment, and the base 110
Has a bottom surface of 600 mm × 600 mm and a height of 300 mm, and the radio wave introducing portion 112 has a quadrangular pyramid width of 75 mm and a height of 141 mm, and the total height of the radio wave absorber is 5.
This is a characteristic when the height is set to 00 mm and is the same as that of this embodiment.

As is clear from the comparison between FIG. 5 and FIG.
In the conventional electromagnetic wave absorbers shown in FIGS. 11 and 12, the TE wave is 40 in the incident angle range of 40 ° to 65 °.
Although the electromagnetic wave absorption amount of dB or more can be obtained, the absorption property of the TM wave has a directivity according to the polarization, such as a low electromagnetic wave absorption amount of about 30 dB at an incident angle of 65 °. On the other hand, according to the electromagnetic wave absorber of this embodiment, TE
40 ° for both polarized waves of TM wave and TM wave
A radio wave absorption amount of 40 dB or more is obtained in the incident angle range of 65 °.

As described above, since the radio wave absorber of this embodiment can obtain good radio wave absorption characteristics for oblique incident waves, it should be mounted on a wall surface in the radio wave darkroom that requires oblique incidence characteristics. This can greatly improve the performance of the anechoic chamber. In addition, since it has a linear shape and can be formed of one kind of material as a whole, it is easy to manufacture. Moreover, as compared with the quadrangular pyramid-shaped electromagnetic wave absorber that is widely used for anechoic chambers, it is possible to realize high-performance characteristics at a lower height, which enables effective use of space and reduces the external dimensions of anechoic chambers. The size can be reduced and the cost can be reduced.

As another embodiment of the present invention, the shapes of the base 10 and the radio wave introducing portion 15 are the same as those in the above-mentioned embodiment, and the bottom surface 14 of the base 10 is 600 mm × 6 in size of each portion.
The height of the radio wave introducing portion 15 is set to 00 mm, the height is 250 mm, and the portion to be joined to the upper surfaces 12 and 13 of the base 10 is 94 mm ×
A radio wave absorber having a height of 75 mm and a height of 250 mm and a height of the radio wave absorber as a whole of 500 mm was prepared. Also in this case, the characteristics as shown in FIGS. 3 to 5, that is, the radio wave absorption amount higher than the conventional radio wave absorber by 10 dB or more for the incident wave with the oblique incidence angle of 65 ° of 2 to 4 GHz, is similar to the above-described embodiment. And 40 ° in the incident angle range of 40 ° to 65 ° for both TE wave and TM wave polarization incidents.
A radio wave absorption amount of dB or more was obtained.

As yet another embodiment, the base 10
The angle between the upper surfaces 12 and 13 of the above is set to about 100 °, and a radio wave absorber having the same structure as that of the above-described embodiment is produced in other configurations. In this case as well, good radio wave absorption similar to that of the above-described embodiment is obtained. The characteristics were obtained.

The embodiments described above are merely illustrative of the present invention and are not restrictive, and the present invention can be implemented in various other modified modes and modified modes. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

[0031]

As described in detail above, according to the present invention, a plurality of quadrangular pyramid-shaped radio wave introducing portions provided on the upper surface of a triangular prism-shaped base and having substantially the same height are provided in the height direction. Is installed so that it is in a direction almost perpendicular to the bottom surface of the base, the impedance change is continuous on the slope, and not only excellent grazing incidence absorption characteristics are obtained, but also the characteristics change due to polarization. It becomes even smaller. Of course, it is relatively easy to manufacture.

Further, since the radio wave introducing portions are provided on the two upper surfaces of the triangular prism-shaped base and the entire absorber has a wedge shape, an excellent scattering effect can be obtained, so that the absorption characteristics are improved. Moreover, since the radio wave introducing portions are in the shape of a quadrangular pyramid having almost the same height, the characteristic change due to the polarization is small also from this point.

[Brief description of drawings]

FIG. 1 is a side view schematically showing a configuration of a radio wave absorber as one embodiment of the present invention.

FIG. 2 is a front view of the radio wave absorber of FIG.

FIG. 3 is a characteristic diagram showing the relationship between the installation angle of the radio wave introducing portion with respect to the bottom surface and the return loss for each TE wave and TM wave.

FIG. 4 is a characteristic diagram showing return loss with respect to frequency for the TE wave and the TM wave in the radio wave absorber of FIG. 1 and the radio wave absorber of FIG. 9.

5 is a characteristic diagram showing the return loss with respect to the angle of the incident wave in the radio wave absorber of FIG. 1 for each TE wave and TM wave.

FIG. 6 is a characteristic diagram showing the return loss with respect to the angle of the incident wave in the conventional radio wave absorber shown in FIG. 9 for each TE wave and TM wave.

FIG. 7 is a characteristic diagram showing the return loss with respect to the angle of the incident wave in the conventional electromagnetic wave absorber shown in FIG. 10 for each TE wave and TM wave.

FIG. 8 shows the return loss with respect to the angle of an incident wave in the conventional electromagnetic wave absorber shown in FIGS.
It is a characteristic view shown according to a wave.

FIG. 9 is a perspective view showing an example of a conventional radio wave absorber.

FIG. 10 is a perspective view showing an example of a conventional radio wave absorber.

FIG. 11 is a perspective view showing an example of a conventional radio wave absorber.

12 is a cross-sectional view of the radio wave absorber of FIG.

[Explanation of symbols]

 10 Base 11 Faces 12 and 13 Top 13 Bottom 14 Radio Wave Introducing Section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Hashimoto 1-13-1, Nihonbashi, Chuo-ku, Tokyo TDC Corporation (72) Inventor Kenichi Ichihara 1-1-13, Nihonbashi, Chuo-ku, Tokyo TDC Co., Ltd. (72) Inventor Takashi Tanaka 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Inc.

Claims (1)

[Claims] 1. A pedestal made of a dielectric loss material, and a plurality of quadrangular pyramid-shaped radio wave introducing portions made of a dielectric loss material and provided on an upper surface of the pedestal and having substantially equal heights to each other. And the base has a triangular prism shape, and three of the five surfaces forming the triangular prism of the base except two facing surfaces are one bottom surface and two top surfaces for absorbing electromagnetic waves. In the body, the radio wave absorber is provided such that its height direction is substantially vertical to the bottom surface of the base.