JP2001185892A - Multilayered electric wave absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric wave absorber that can efficiently absorb various kinds of polarized waves. SOLUTION: A multilayered electric wave absorber 10 is composed of first and second electric wave absorption layers 12 and 14, and the orientation direction (arrow A) of a ferrite for forming the first electric wave absorption layer 12 orthogonally crosses the orientation direction (arrow B) of the ferrite for forming the second electric wave absorption layer 14. One of the first and second electric wave absorption layers 12 and 14 absorbs a horizontally polarized wave extremely well, and the other absorbs a vertically polarized wave extremely well. Also, the first and second electric wave absorption layers 12 and 14 jointly absorb an electric wave where the directions of a circulary polarized wave and the polarized wave are oblique. As a result, the multilayered electric wave absorber 10 can absorb various kinds of polarized waves efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention belongs to the technical field of radio wave absorbers.

[0002]

2. Description of the Related Art There has been known a radio wave absorber made of, for example, a plate formed by combining a powder or a fibrous body of a magnetic substance or a conductor through a binder.

[0003]

There are various types of polarization systems for broadcast waves and communication waves. For example, in the case of terrestrial television broadcasting, horizontal polarization is widely used and vertical polarization is sometimes used. . Also, rotation polarization is adopted in satellite broadcasting and the like. As in these examples, the directions of polarization of radio waves are various, and a radio wave absorber capable of efficiently absorbing such various polarizations has been demanded.

[0004]

Means for Solving the Problems and Effects of the Invention A multilayer electromagnetic wave absorber according to claim 1 for solving the above problems is provided by:
When the powder or fibrous body is bonded via a binder, the first radio wave absorbing layer and the second radio wave absorbing layer in which the powder or fibrous body is oriented in a certain direction, the orientation directions of the two are orthogonal to each other. For example, the first radio wave absorbing layer efficiently absorbs the horizontally polarized wave, and the second radio wave absorbing layer efficiently absorbs the vertically polarized wave. In addition, the first order is also applied to radio waves having a rotational polarization or an oblique polarization direction.
The radio wave absorption layer and the second radio wave absorption layer cooperatively absorb efficiently. Therefore, radio waves of various polarizations can be efficiently absorbed.

It is needless to say that the powder or fiber used must have radio wave absorption (for example, it must be magnetic or dielectric). Claim 2
The multilayer electromagnetic wave absorber according to claim 1, wherein the powder is ferrite in the multilayer electromagnetic wave absorber according to claim 1.

For example, ferrite can be formed into a flat shape having a long axis and a short axis (giving orientation) when a ferrite crystal is grown in a sintering step. When the ferrite powder having such a shape is bound in one direction by a press or a magnetic field when the ferrite powder is bonded with a binder, an oriented radio wave absorbing layer can be manufactured. This may be used as the first radio wave absorption layer and the second radio wave absorption layer.

[0007]

Next, an embodiment of the present invention will be described with reference to an embodiment of the present invention. As shown in FIG. 1, the multilayer radio wave absorber 10 includes a first radio wave absorption layer 12 and a second radio wave absorption layer 1.
4.

First radio wave absorbing layer 12 and second radio wave absorbing layer 1
Reference numeral 4 denotes a ferrite 16 corresponding to the powder material,
And formed into a plate shape. The shape of each ferrite 16 forming the first radio wave absorption layer 12 and the second radio wave absorption layer 14 is a flat shape having a major axis L and a minor axis S as illustrated in FIG. L is much larger than thickness T (the aspect ratio T / L is extremely small). Then, as shown in an enlarged manner in FIG.
The direction of the major axis L of each of the ferrites 16 of the radio wave absorbing layer 12 and the second radio wave absorbing layer 14 is substantially aligned in one direction, and the ferrites 16 are oriented in that direction.

However, as shown in FIG. 1A, the first radio wave absorbing layer 12 and the second radio wave absorbing layer 14
6 differ by 90 degrees. That is, the orientation direction of the first radio wave absorption layer 12 (indicated by the arrow A) and the second radio wave absorption layer 1
4 is orthogonal to the orientation direction (indicated by arrow B).

[0010] As shown in FIG.
Is formed by laminating a first radio wave absorption layer 12 and a second radio wave absorption layer 14 with their orientation directions (arrows A and B) orthogonal to each other. For this reason, one of the first radio wave absorption layer 12 and the second radio wave absorption layer 14 absorbs horizontal polarization very well,
Vertical polarization is absorbed very well by the other. In addition, the first radio wave absorption layer 12 and the second radio wave absorption layer 14 cooperatively absorb even the rotationally polarized waves and the radio waves whose polarization directions are oblique. Therefore, the multilayer radio wave absorber 10 can efficiently absorb radio waves of various polarizations.

The embodiments of the present invention have been described with reference to the embodiments. However, the present invention is not limited to the embodiments, and may be variously implemented without departing from the gist of the present invention. Needless to say.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a structure of a radio wave absorber of an embodiment;
FIG. 1A is an explanatory view of a layer structure and an orientation direction, FIG. 1B is an enlarged plan view showing an orientation of ferrite, and FIG. 1C is a perspective view showing a shape of the ferrite.

FIG. 2 is an explanatory diagram of the operation of the radio wave absorber of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Multilayer radio wave absorber 12 ... First radio wave absorption layer 14 ... Second radio wave absorption layer 16 ... Ferrite 18 ... Binder

Claims (2)

[Claims] 1. A first radio wave absorption layer and a second radio wave absorption layer in which the powder or fiber body is oriented in a certain direction when the powder or fiber body is bonded via a binder, and A multilayer electromagnetic wave absorber characterized by being laminated with the orientation directions orthogonal to each other. 2. The multi-layer radio wave absorber according to claim 1, wherein the powder is ferrite.