JPS5982800A - Radio wave absorber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a radio wave absorber, and more particularly to a two-layer radio wave absorber that can obtain broadband characteristics and be lightweight.

(Background technology) Conventionally, in order to suppress reflected radio waves from radio wave reflectors such as ships, aircraft, or steel towers, electromagnetic absorbers such as magnetic materials or resistive materials are often attached to such reflectors. .

An example of a conventional single-layer charge absorber is shown in FIG.

This radio wave absorber is constructed by adhering metal &2 to an absorbing layer 1 formed by mixing and dispersing a magnetic material such as ferrite or a dielectric material such as carbon in a resin.

This kind of single-layer radio wave absorber can be constructed of thin (
For example, in the X band (8 to 12 GHz), it is possible to reduce the thickness to 2 mm or less. In addition, since it is a single layer, there are fewer points to manage during manufacturing (and it has the advantage of excellent workability).

However, as shown in Figure 4, this yuzu radio wave absorber had the disadvantage that the band in which attenuation of 20 dB or more could be obtained was narrow, extending about 10% from the center frequency. In order to achieve this, a two-layer radio wave absorber as shown in FIG. 2 has been proposed.

This radio wave absorber has a second layer 12 made of ferrite mixed and dispersed in resin on one side of a first layer 11 made of ferrite and short metal fibers mixed and dispersed in resin (laminated as shown in the figure). A metal plate 13 is lined on the surface opposite to the surface on which the second layer 12 of the first layer 11 is stacked.In this two-layer radio wave absorber, the first layer 11 is an absorption layer in terms of electromagnetic waves The second layer 12 acts as a matching transformer.The conventional two-layer radio wave absorber using this ferrite is as follows.

(Objective of the Invention) The present invention has been made by paying attention to such conventional problems, and aims to provide a radio wave absorber that can obtain broadband characteristics and be lightweight.

(Structure and operation of the invention) The present invention will be explained below based on the drawings.

FIG. 3 is a sectional view showing an embodiment of the radio wave absorber according to the present invention. As shown in the figure, this radio wave absorber is a so-called two-layer radio wave absorber consisting of a first layer 21 that acts as an absorption layer, a second layer 22 that acts as a matching transformer, and a metal layer B. Each layer is laminated by a method such as bonding with an adhesive.The first layer 21 is formed by mixing and dispersing a magnetic material and a conductive substance in a first matrix (base material). Meanwhile, the second layer 22 may be formed by mixing and dispersing a dielectric material in a second matrix.

The absence of magnetic material in this layer is a feature of the invention.

11i2] may be iron powder or a mixture of iron powder and ferrite.

Further, as the conductive substance, a metal or carbon substance in the form of powder or fiber can be used, and synthetic fiber coated with a conductor such as copper oxide may also be used. The use of a fibrous conductor is particularly suitable when strength and weather resistance are required for the radio wave absorber. First matrix (base material)
Various resins, rubber, concrete, ceramics, etc. can be used as the material. The first and second matrices may be of the same type or may be of different types.

Various metals such as aluminum, iron, and stainless steel can be used for the metal layer 23.

Next, a preferred embodiment of the present invention will be described while comparing it with a conventional example.

FIG. 4 is a diagram showing the relationship between return loss and frequency of a single-layer radio wave absorber having an absorbing layer composed of 10 volumes of Ni-Zn ferrite, 15 volumes of carbonyl iron, and 75 volumes of Pybalon rubber. As can be seen from the figure, a frequency bandwidth Δf with a return loss of 20 dB or more and a center frequency f of the frequency band. The ratio (fractional band) is about 10 inches.

FIG. 5 is a diagram showing the relationship between the amount of reflection and frequency of a two-layer radio wave absorber according to an embodiment of the present invention.

The first layer of the radio wave absorber in this example consists of 20 volumes of carbonyl iron (particle size 1 to 5 μm) and carbon chopped fibers (diameter 15 to 25 μm, length 200 to 400 tt).
m) 8-body multiplexed with epoxy resin (manufactured by Ciba Geigy:
GY250-HY850) 72 volume multi-mixed and dispersed layer with a thickness of 1.1 mm. The second layer consists of 3 volumes of titanium oxide (particle size: 0.1 to 2 μm) and epoxy resin (
Manufactured by Ciba Geigy: GY250-HY850)
It is a 3.7 mm thick layer mixed and dispersed in 97 volumes. Further, an aluminum plate with a thickness of 2 am was used as the metal layer.

As is clear from FIG.
It can be seen that f/fo) is approximately 50 inches, which is significantly improved compared to the conventional single-layer radio wave absorber shown in FIG.

(Effects of the Invention) As explained above, the present invention has the following effects.

(1) The bandwidth at which return loss of 20 dB or more can be obtained can be tripled or more compared to that of a single-layer structure.

t21 Since the second absorbing base layer does not have magnetism, the design,
Manufacturing becomes easier.

(3) Since no magnetic material is used in the second absorption base layer, quantification becomes possible.

[Brief explanation of drawings]

Figure 1 is a sectional view showing a conventional single-layer radio wave absorber, Figure 2 is a sectional view showing a two-layer radio wave absorber using ferrite in the first layer, and Figure 3 is a two-layer radio wave absorber according to the present invention. FIG. 4 is a graph showing the relationship between the return loss and frequency of the single-layer radio wave absorber shown in FIG. 1, and FIG. It is a graph showing the relationship between return loss and frequency. 21...First layer 22...Second layer 23...Metal layer Patent applicant Tokyo Denki Kagaku Kogyo Co., Ltd. Patent application agent Megumi Yamamoto - (7 ) Continued from page 1 0 Inventor: Ken Ichihara - Tokyo Denki Kagaku Kogyo Co., Ltd., 1-13-1 Nihonbashi, Chuo-ku, Tokyo 0 Inventor: Yasuo Hashimoto Tokyo Electric, 13-1 Nihonbashi-chome, Chuo-ku, Tokyo Inventor Yoshikazu Narimiya 13-1, Nihonbashi-chome, Chuo-ku, Tokyo Written amendment to procedures within Tokyo Densaku Chemical Industry Co., Ltd. (voluntary) Commissioner of the Patent Office Kazuo Wakasugi 1, Indication of the case Showa 1957 Patent 1 Condyle No. 191. ! No. 137 No. 2 Name of the invention Radio wave absorber 3 Who makes the amendment What is the relationship? Patent applicant 5. The subject of the amendment is iron powder or a mixture of iron powder and ferrite 1." Examples include ferrite alone, soft magnetic metal powder such as permalloy and iron powder, or a mixture of these and ferrite.'' (2) “Carbon substance” on page 4, line 11 of the specification is replaced with “carbon, etc.”
and correct it. (3) “First matrix” on line 15 of No. 4 of the specification
are corrected as "first and second matrices". (4) Correct the "return loss amount" on page 5, line 6 to line 7 of the specification to "reflection amount". (5) "Return loss amount" on page 7, line 3 of the specification is corrected to "reflection amount." (6) "Return loss amount" on page 7, line 5 of the specification is corrected to "reflection amount." (7) Figures 4 and 5 of the drawings will be corrected as shown in the attached sheet. Above Figure 4: Frequency 1 ((GHz) Figure 5: Frequency & (GHz)

Claims (1)

[Claims] A first layer formed by mixing and dispersing a magnetic material and a conductive material in a first matrix, and a second layer formed by mixing and dispersing a dielectric material in a second matrix and provided on one surface of the first layer. a layer, and one surface of the first layer, the i 2 Jm
1. A radio wave absorber comprising a surface provided with a metal layer and a metal layer provided on an opposing surface.