JPS5934701A - Radio wave absorber - Google Patents

Abstract

PURPOSE:To reduce the strict control of production of a radio wave absorber, by controlling the resistance value with how to weave conductive fibers which form a resistance film. CONSTITUTION:The conductive fibers like metallic fibers, etc. are obtained by coating a conductive material such as brass, etc. on the surfaces of carbon fibers, silicon carbide fibers, etc. Such conductive fibers are distributed in a lattice form with gaps 24 formed in vertical directions 10-16 and horizontal directions 17-23 in order to obtain a resistance film. The impedance of each resistance film is lowered successively toward a reflector 8 from the side of a surface 1, and at the same time plural numbers of resistance films are arranged in parallel to each other with a fixed distance (t). Then a reflector 8 is provided to a resistance film 7 at an end of the resistance film. These films are combined into a multilayered structure. Such a resistance film is hardened with resin having <=10 dielectric constant. This resin can minimize the reflection of radio waves as less as possible. The impedance per unit area of the resistance film can be controlled easily by changing how to weave the conductive fibers, i.e. changing the number of resistance films (the area of gap 24 formed with vertical and horizontal fibers).

Description

[Detailed description of the invention] (Technical field) The present invention relates to a radio wave absorber.

(Background technology) Conventionally, reflected radio waves from radio wave reflectors such as ships, aircraft, or steel towers have been suppressed! ! In order to do this, a radio wave absorber such as a magnetic material or a resistive material is often mounted on such a reflector.

What are the following conditions for designing a radio wave absorber? Demands to meet,! +ru.

this. =zA ・・・・・・・・・・・・
(1)-αd e go (to) ・・・・・・・・・・・・
f2+where, ZO: characteristic impedance of free space (377Ω) λA
:Loss interest penalty innovidance (1: Loss side slope j value α: Loss penalty penalty loss amount.

Equation (1) is based on the condition that the lossy material acts as a radio wave absorber and does not reflect radio waves in the forward direction of the lossy material, that is, the matching condition where the characteristic impedance of free space and the characteristic impedance of the lossy material are equal. be. Equation (2) is the first condition for determining the radio wave absorption characteristic of the absorber, with the thickness 1 of the lossy material and the amount of loss α of the lossy material as parameters.

As a means to satisfy the condition of formula (1), there is a method of sequentially changing the inopedance of a lossy material, which has been developed as a multilayer electric θU absorber by Tenkawa)'+. However, when carbon fiber is used as the loss material, there is a problem in that it is difficult to control the resistance value, and strict control and control is necessary.

(Objective of the invention) The invention addresses the problems of the conventional technology.
Shitenasa Jll Komono aims to solve the above problem by controlling the resistance value by weaving the conductive fibers that form the resistive film, and its features include carbon fiber, silicon carbide fiber, A conductive layer is coated on the surface of organic or inorganic fibers, and several resistive films made of conductive fibers woven in a lattice pattern are arranged in parallel, and one conductive reflector is installed at one end of the resistive film. and between the resistive film, the anti-fouling layer, and σ) with a resin having a dielectric constant of 10 or less.
The innovation of the registered resistive film lies in the radio wave absorber, which is configured so that the resistive film becomes smaller in size from the resistive film in free space to the resistive film in the reflector.

(Structure and operation of the invention) Hereinafter, the invention σ) will be explained based on the drawings.

This is a cross-sectional view. In the figure, 1 to 7 are a resistive film which is one of the features of the invention, 8 is a reflector based on a conductor D-, and 9 is a dielectric.

First, the resistive film will be explained. Figure 2 is a diagram showing the structure of a resistive film. Conductive fibers such as metal fibers coated with 0) fibers 1() to 1(5) in the longitudinal direction
The lateral fibers 17-2:3 are formed in a lattice shape so that the voids 2.1 are T+. The impedance per unit area of the resistive film is determined by the weave of the conductive fibers, that is, the number of resistive fibers σ) (in other words, the area of the void 2.1 formed by the longitudinal fibers and the vertical fibers). You can easily control it by changing it.

Further, FIG. 3 shows another configuration example. 4-electrical fiber 1f (t, 2
It is also possible to form a lattice-like resistive film by combining 5°26 with fibers (for example, nylon, acrylic) for supporting the conductive fibers. .

Several of the resistive films thus formed are arranged in parallel with an interval t of -W as shown in FIG. A body is provided and combined into a multi-layered structure. As for the value of the distance t, it is desirable to make all the resistive films the same from the viewpoint of manufacturing, but from the viewpoint of operation principle, this is the only value. When all 1's have the same value, a preferable value is about 9 mm. 2 Here, the innovation dance of each resistive film is expressed by the above-mentioned formula (1
In order to satisfy 1, it is necessary to reduce the -1111-order resistance value from the surface to the reflector direction. This first IL control is
This is done with a number of conductive fibers as described above. FIG. 4 shows how the resistance value of the resistive membrane changes with changes in the number of conductive fibers. As is clear from the figure, as the number of conductive fibers π increases, the resistance value of the resistor j decreases. The preferred number of conductive fibers per unit length is: Resistive film 1: 20 pieces/1oCr/L Resistive film 2: 35 pieces/10CTL Resistive film 3
・・・・・・・・・5) 0 pieces/1ocm fox anti-film 4...
...00 lines/10cm resistance 11! ! 5 ・---
-75 pieces/l0cm resistive film 6--90 pieces/]Ocn+ Resistive film 7-! 15 wood/I (1cm).

Such a resistive film is used as I/C, iA as shown in Fig. 1.
Harden with a resin with a lli rate of 10 or less 3,
The ratio is 10 or more, and 7F and L are simply the supports for each resistive film. , ) -C
be.

Figure 5 shows an example of the characteristics of the radio wave absorber shown in Figure 1, with 4 GI
Iz~1(JCjllz, the reflection is -1,'+d13 or more 1-1+(1("+11/, above -20(113 or more).

(Effects of the Invention) As explained above, according to the present invention, the resistance value of the resistive film can be controlled by the method of weaving the conductive fibers. It is possible to obtain f-peak and wave absorption characteristics.

[Brief explanation of drawings]

Fig. 1 is a structural diagram showing an embodiment of the present invention, Fig. 2 is a structural diagram of a resistor film σ); Fig. 3 is a structural diagram of a resistive film σ); θ) Number and 4” (Antai and θ) 1 length I K
? /1'e -1-graph, ri), Figure 5 is 'f, 1
Figure θ)'l' L-wave absorber σ) Characteristic diagram of L, B) 1. 1, 2, 3, 4, 5.6.7... Resistive film 8
・・・・・・Conductor reflector 0 ・・・・・・Resin No. 10 to 25, 2! i, 2(i...Derivation:
l'1', 1. jM &II2・1・・・・・・
Gaps 27, 28...1lf (nylon/acrylic)! samurai,
;'I Applicant: Tokyo Denki Kagaku Shimojo Co., Ltd. 71'11j'l Output #+! [1 Proxy Bench J-+I+ Ki Kei - Figure 1 Figure 2

Claims (1)

[Claims] Carbon fiber, silicon carbide-based binding string: A plurality of resistive films made of organic or inorganic fibers coated with a conductive material and woven in a lattice pattern are arranged in parallel, and one reflective conductor is attached to one end of the resistive film. The body is set up with a resin having a dielectric constant of 10 or less between each resistive film and between the resistive film and the reflective layer, and the impedance of each of the resistive films is ζ-plane from the resistive film facing free space to the reflective layer. Is it that A' is constructed so that it becomes smaller in size according to the resistance film? Characteristic radio wave absorber.