KR100498887B1 - Broad-band ferrite electromagnetic wave absorber - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wideband ferrite radio wave absorber, which satisfies the demand for widening of the radio wave absorber, and allows the manufacturing conditions to be made more economically.

According to the present invention, a tile-like ferrite magnetic material is disposed on a reflecting plate, a first-layer tile-like ferrite magnetic material is disposed on a tile-like ferrite magnetic material, and a cylindrical ferrite magnetic material, which is a second layer, is vertically and laterally spaced at a predetermined interval (a), and a second-type cylindrical ferrite magnetic material is disposed on a reflective layer. The three-layered cutting cone-shaped ferrite magnetic material is disposed, and the third-layered cutting-cone-shaped ferrite magnetic material is disposed on the fourth-layer cylindrical ferrite magnetic material, and the longitudinal and horizontal spacing (a) of the second layer is larger than the wavelength of the radio wave used. Short, the diameter of the second layer and the diameter of the lower side of the third layer r ₁ , the diameter of the upper side of the third layer and the diameter of the fourth layer r ₂ , the height from the first layer to the fifth layer h ₁ , For h ₂ , h ₃ , and h ₄ , r ₁ is r ₂ <r ₁ <a, r ₂ is 5mm <r ₂ <15 mm, h ₁ is 4mm ≤ h ₁ ≤ 8 mm, and h ₂ is 1 mm ≤ h ₂ ≤ 5 mm, h ₃ is 10 mm ≤ h ₃ ≤ 20 mm, h ₄ is 0.1 mm ≤ h ₄ ≤ 2.5 mm to be.

Description

BROAD-BAND FERRITE ELECTROMAGNETIC WAVE ABSORBER

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wideband ferrite radio wave absorber, and more particularly, to widening of a radio wave absorber composed of a ferrite magnetic material.

Wide band ferrite absorber is widely used as a wall material for preventing interference of TV and radar by radio wave reflection from radio dark room, building, bridge, etc. Will be.

A radio wave absorber composed of sintered ferrite, which is a conventional magnetic material, has a thin thickness of about 5 to 8 mm, and has an excellent characteristic of absorbing low frequency radio waves of, for example, about 30 MHz. It is widely used as a wall material for preventing the reflection of radio waves by radio darkrooms and buildings for measuring the radio waves.

On the other hand, as a technique for widening a radio wave absorber made of a magnetic layer, for example, a technique has been proposed in which a tile-like ferrite magnetic body is floated in an air layer (actually, floated from a reflecting plate using a foamed polyurethane plate). As an example of this technique, a NiZn-based ferrite tile of 7 mm in height (thickness perpendicular to the tile mounting surface) is placed at a height of 17 mm from the reflector via a 10 mm air gap from the reflector. A radio wave absorber with a reflection attenuation of 20 dB or more can be obtained for a radio wave of ˜800 MHz.

In general, when the reflection coefficient of the radio wave is S on the surface of the radio wave absorber, the power absorption coefficient alpha _p of the radio wave absorber is expressed as shown in equation (1).

Therefore, the smaller the S is, the better the radio absorber has. The equation (2) is generally used as a measure of the radio wave absorber characteristics evaluation.

In other words, the reflection attenuation amount (-20 log S) is 20 dB or more and the absorption coefficient ≥ 0.99 is adopted.

As shown in FIG. 15, the most basic ferrite radio wave absorber has a structure in which a ferrite magnetic body (F) on a tile is attached to the reflecting plate (M), and the absorption characteristics of the radio wave absorber having the above structure are shown in FIG.

In FIG. 16, the horizontal axis represents frequency f and the vertical axis represents reflection coefficient │ S │. The lower and upper limit frequencies │ S │ = 0.1 in the drawing are f _L and f _H , respectively. Similarly, the frequency bandwidth B that satisfies S = 0.1 is expressed by Equation (3).

Much research has already been done on the bandwidth B, for example

(A) The ferrites used when the lower limit frequency (f _L ) is 30 MHz are all sintered and of NiZn type or MnZn type. In this case, the upper limit frequency (f _H ) is generally 300 MHz to 400 MHz. It becomes

(B) The ferrites used when the lower limit frequency (f _L ) is 90 MHz are all sintered and of NiZn type or MnZn type. In this case, the upper limit frequency (f _H ) is generally 350 MHz to 520 MHz. It becomes

As an application, when applying a radio absorber to a wall of a radio darkroom for measuring radio waves from the above-mentioned electronic equipment, f _L = 30 MHz, and f _H is the 1998 International Special Committee on Radio Interference. In the case of des Perturbations Radioelectrique II, the frequency range is 20 GHz, so in the case of (A), the upper limit frequency (f _H ) is low, and in (B), the upper limit frequency (f _H ) is also low. In addition, f _L = 90 MHz and f _H = 800 MHz are required in Japan in the case of wall materials for preventing reflection of TV radio waves from buildings, and the radio absorber of (B) also has insufficient characteristics.

Therefore, various attempts have been made to improve the radio wave absorber, and as an example of the recent widening of the radio wave absorber composed only of sintered ferrite, a radio wave absorber in which a ferrite is disposed in a lattice form on a reflector is disclosed in US Patent No. 5,276,448. The proposed lattice wave absorber has f _L = 30 MHz and f _H = 800 MHz.

In addition, as an example of widening of a radio wave absorber composed of only sintered ferrite, a tile-like ferrite magnetic material is disposed on a reflecting plate, and a ferrite magnetic material of the same thickness that is repeatedly arranged in a lattice shape at regular intervals on the tile-like ferrite magnetic material is superposed. A radio wave absorber in which a slot is formed along a height direction at the same has been proposed by the present inventors as Korean Patent No. 144,802.

The lattice wave absorber is obtained by f _L = 30 MHz and f _H = 1000 MHz.

However, the radio wave absorption characteristics of the radio wave absorber are satisfied for the wall material of the building, but the radio dark room use is significantly lower than the above-regulated range, and the thickness of the ferrite of a part of the structure should be made relatively thin and the width and thickness of the slot should be made small. In the case of forming the whole structure integrally during the actual manufacturing process, when the material is injected into the mold, poor material flow, poor mold release of the molded product, uneven molding pressure, and the like are deformed or broken during sintering. It is easy to occur and the problem that manufacturing cost rises due to difficulty of setting manufacturing conditions is inevitable.

The inventors of the present invention disclose a radio wave absorber in which a tile-like ferrite magnetic body is disposed on a reflecting plate, and a cutting cone-shaped ferrite magnetic body is disposed on the tile-like ferrite magnetic body at a predetermined interval across the tile-like ferrite magnetic body. Proposed 2001-103,241, the wave absorber is obtained f _L = 30 MHz, f _H = 50 GHz.

However, the above-mentioned radio wave absorber meets the radio wave absorption characteristics required in the radio darkroom, but when the entire structure is integrally formed during actual manufacture, sharp projections at the tip of the protrusion due to uneven molding pressure of the molded product and stroke unevenness of the upper and lower molds There is a problem that the breakage occurs, or the shape of the projection is changed and the defect rate is high. In particular, as the interest in the electromagnetic environment (EMI / EMC) increases, the wave absorber is also required to be broadband. The frequency to be used for the environment, etc. will be a higher frequency, so f _H will inevitably be higher.

1 is a perspective view of a first embodiment of a radio wave absorber according to the present invention;

2 is a plan view of a first embodiment of a radio wave absorber according to the present invention;

3 is a side view of a first embodiment of a radio wave absorber according to the present invention;

4 is an absorption characteristic diagram of a first embodiment of a radio wave absorber according to the present invention;

5 is a perspective view of a second embodiment of a radio wave absorber according to the present invention;

6 is a plan view of a second embodiment of a radio wave absorber according to the present invention;

7 is a side view of a second embodiment of a radio wave absorber according to the present invention;

8 is an absorption characteristic diagram of a second embodiment of a radio wave absorber according to the present invention;

Fig. 9 is a principle diagram for obtaining an equivalent dielectric constant and an equivalent permeability in the case where the radio wave absorber according to the present invention is divided into multiple layers and homogenized.

10 is a unit structure diagram for obtaining a synthetic capacity of a radio wave absorber according to the present invention.

FIG. 11 is a synthetic capacity model of FIG. 10. FIG.

12 is a unit structure diagram for obtaining a synthetic inductance of a radio wave absorber according to the present invention.

FIG. 13 is a composite inductance model diagram of FIG. 12. FIG.

14 is a multi-layered model for determining the reflection coefficient of the radio wave absorber according to the present invention.

Fig. 15 is a side view of a basic tiled ferrite wave absorber.

16 is an absorption characteristic diagram of a basic tile-like ferrite wave absorber.

Best Mode for Carrying Out the Invention

Absorption characteristics of the radio wave absorber of the embodiments to be described below are evaluated by measurement by a TEM wave using a rectangular coaxial line.

In addition, in FIGS. 1 to 3 and 5 to 7 showing the structure of the radio wave absorber of each embodiment, M is a reflector, F is a sintered ferrite, Cu is a unit structure constituting a radio wave absorption layer, the radio wave absorption layer of the present invention The layer of the unit structure (Cu) is configured to be arranged side by side on the same plane so that the required area in contact with each other.

R ₁ is the diameter of the lower side of the two-layer cylindrical ferrite and the three-layer cutting cone column ferrite, r ₂ is the upper side of the three-layer cutting cone column ferrite and the diameter of the four-layer cylindrical ferrite, r ₃ is the five-layer lower cutting spheroid The lower diameter of the ferrite, h ₁ , h ₂ , h ₃ , h ₄ , h ₅ are the heights of the first to fifth layers, which are cavities in all figures.

Example 1

In the first embodiment of the present invention, as shown in Figs. 1 to 3, the tile-like ferrite magnetic material, which is the first layer, is disposed on the reflecting plate M, and the second layer is vertically and horizontally spaced apart from the tile-like ferrite magnetic material. Arranging a cylindrical ferrite magnetic material, placing a three-layered cutting cone-shaped ferrite magnetic material on the second-layer cylindrical ferrite magnetic material, and arranging a fourth-layer cylindrical ferrite magnetic material on the three-layered cutting cone cylindrical ferrite magnetic material, The height h ₁ , h ₂ , h ₃ , h _{4 of the} layer, the second layer, the third layer, the fourth layer, the diameter of the second layer and the lower side diameter r ₁ of the third layer, and the upper side diameter of the third layer And controlling the diameter r ₂ of the fourth layer to control the equivalent permeability and the equivalent dielectric constant.

In the manufacture of the first embodiment, the first layer, the second layer, the third layer, and the fourth layer were manufactured by integrally molding, but in the drawings, the first layer to the fourth layer are shown separately for ease of separation. .

The radio wave absorption characteristics of the first embodiment of the present invention were obtained as follows.

Since the first layer is formed of tile-like ferrite, the equivalent dielectric constant ( ) Is

In the above formula (4), Is the relative dielectric constant of ferrite.

In addition, the equivalent permeability ( ) Is shown below.

In the above formula (5a) Is the specific permeability of ferrite

In the formula (5b) Is the initial permeability of ferrite, Is the relaxation frequency of ferrite, Is frequency, Is an imaginary unit.

In the second to fourth layers of the first embodiment, the portion F of the ferrite and the portion A of the air are mixed as shown in FIG. 9 (a) showing only one cycle of the periodic arrangement of FIG. In order to obtain a homogeneous equivalent effective dielectric constant (Fig. 9 (b)) ) And equivalent effective permeability ( ), Which is proposed by the present inventors and the like.Equivalent material constants method: IEEE Transactions on Electromagnetic Compatibility, Vol. 38, No. 2, pp. 173-177, May 1996 Reference).

1 and 9 (a) has a symmetry, as can be seen in the plan view of FIG. 3 can be represented as a quarter of one cycle, that is, the unit structure (Cu), virtual in FIG. Each layer is divided into 1, 2, 3, ... as shown in FIG. i… Equivalent effective dielectric constant when divided into n layers ( ) And equivalent effective permeability ( ) Is obtained and substituted in FIG. 9 (b) to homogenize each layer.

Equivalent dielectric constant with respect to the unit structure (Cu) of the second layer ( ) And equivalent permeability ( ) Can be obtained as shown in the following equation by using the equivalent material constant calculation model diagrams (FIGS.

Using the unit structure of the third layer, as shown in Fig. 9 (a), the layer is divided into three layers (n-1), and the equivalent dielectric constant and permeability of each layer are calculated as shown in the following equations according to Figs. Each layer can be homogenized as in b).

In the above formula (8) (9) Is the axial length occupied by the ferrite to each step in FIGS. 10 and 12 of the i th layer.

For the fourth layer it is obtained by replacing the r ₁ to ₂ h to ₄ h in the formula (6) and (7) to r _2.

The equivalent model obtained as shown in FIG. 9 (b) is identical to the multilayered model diagram of FIG. 14, and thus the reflection coefficient | S | in this case is as follows.

In Equation (10), Z _n is an input impedance viewed from the surface of the n layer toward the reflector, and z ₁ is represented by Equation (11), and z ₂ to Z _n are represented by Equation (12) using FIG. Is obtained.

D ₁ , d ₂ ,... In formula (11), formula (12) and FIG. , d _n is the thickness of each layer divided.

The ferrite magnetic bodies used in the first embodiment are all NiZn-based sintered ferrite, and the relative dielectric constant = 14, specific permeability = 2,500.

2 and 3, the height h ₁ of the first layer is 6.2 mm, the height h ₂ of the second layer is 2 mm, the height h ₃ of the third layer is 16 mm, and The height h ₄ is 0.5 mm,

The diameter of the second layer and the diameter r ₁ of the lower side of the third layer is 18 mm, the diameter of the upper side of the third layer and the diameter r ₂ of the fourth layer is 10 mm, and the longitudinal and horizontal spacing (a) of the second layer. Is made of 20 mm.

The radio wave absorption characteristics of the radio wave absorber having the above structure were obtained as shown in FIG. .

The result is that in the Korean Patent Application Publication No. 2001-103,241 proposed by the inventors, etc., the tile-type ferrite ground body (h ₁ = 6.5 mm) is disposed on the conductor plate M, and the cutting cone-shaped ferrite magnetic material is simply raised thereon. (h ₂ ) is 18 mm, the arrangement period (a) is 20 mm, the propagation when the diameter (r ₁ ) of the lower side of the cutting cone-shaped ferrite magnetic body is 18 mm and the diameter (r ₂ ) of the upper side is 7 mm The absorption efficiency is improved by about 5 dB, and in the first embodiment, since the cylindrical ferrite magnetic material is disposed on the upper side of the cutting cone-shaped ferrite magnetic material, the edge breakage phenomenon can be eliminated when the monolithic fabrication is made integrally.

Example 2

In the second embodiment of the present invention, as shown in FIGS. 5 to 7, the tile-like ferrite magnetic material, which is the first layer, is disposed on the reflecting plate M, and the predetermined thickness (a) is disposed on the tile-like ferrite magnetic material, which is the first layer. A cylindrical ferrite magnetic body, which is a second layer, is disposed vertically and horizontally, and a truncated cone cylindrical ferrite magnetic material, which is a third layer, is disposed on the cylindrical ferrite magnetic material, which is the second layer, and a cylindrical ferrite magnetic material, which is a fourth layer, on a third cutting cone column type ferrite magnetic material. And arranging the lower cut spheroidal ferrite magnetic body, which is the fifth layer, and the heights h ₁ , h ₂ , h ₃ , h ₄ , h _{5 of} the first layer, the second layer, the third layer, the fourth layer, and the fifth layer; Equivalent permeability by adjusting the diameter of the second layer and the lower side diameter r ₁ of the third layer, the upper side diameter of the third layer and the diameter r ₂ of the fourth layer and the lower diameter r ₃ of the lower cut rotation ellipse of the fifth layer and Equivalent dielectric constant control It would be a help.

The radio wave absorption characteristics of the second embodiment of the present invention can be obtained by the above formulas (4) to (12) as in the first embodiment, and the fifth cut layer of the elliptic ferrite magnetic body is the fifth layer. In this case, the basic principle is the same as that of the cutting cone-shaped ferrite magnetic body of the first embodiment, and only the decrease in the radius is different as it goes up to the upper layer, so that in Equation (8) and (9) Only the expression of can be obtained by modifying it using elliptic equation.

In addition, the second embodiment was also manufactured by integrally molding the first to fifth layers, but in the drawings, the first layers to the fifth layers are separately shown to facilitate division.

The ferrite magnetic bodies used in the second embodiment are all NiZn-based sintered ferrite, and the relative dielectric constant = 14, the specific permeability is = 2.500 was used.

6 and 7, the height h ₁ of the first layer is 6.2 mm, the height h ₂ of the second layer is 2 mm, the height h ₃ of the third layer is 16 mm, and The height h ₄ is 0.5 mm, the height h ₅ of the fifth layer is 2.3 mm, the diameter of the second layer and the diameter r ₁ of the lower side of the third layer is 18 mm, the upper side and the third layer of the third layer. The diameter r ₂ of the four layers was 10 mm, the lower diameter r ₃ of the fifth layer was 6.8 mm, and the longitudinal and horizontal spacings a of the second layer were 20 mm.

The radio wave absorption characteristics of the radio wave absorber having the above-described structure were obtained as shown in FIG. 8 with respect to the vertically incident wave from the ferrite surface in the direction of the reflector, and the amount of reflection attenuation of 25 dB or more was obtained in the frequency range of 30 MHz to 100 GHz. It was.

The frequency characteristic of the radio wave absorber of the second embodiment is not only improved by 4 dB or more than the radio wave absorber of the first embodiment, but also easy to manufacture, and in the second embodiment, the end is convex, so that the surface reflection at the end is significantly reduced. As a result, the performance is greatly improved in the low frequency region as well as the high frequency region.

As described above, according to the present invention, a tile-like ferrite magnetic material is disposed on a reflecting plate, a cylindrical ferrite magnetic material is disposed on the tile-like ferrite magnetic material in a longitudinal and horizontal direction at a predetermined interval (a), and a truncated cone-shaped ferrite magnetic material is disposed on the cylindrical ferrite magnetic material. In addition, a wide-band ferrite radio wave absorber having a shape in which a cylindrical ferrite magnetic material and a lower cutting spherical elliptic ferrite magnetic body are sequentially arranged on the cutting cone-shaped ferrite magnetic material. It can be manufactured at cost and can be easily controlled to change the equivalent permeability and equivalent permittivity to a desired value, so that it is especially used for wall materials of buildings to prevent virtual images of TV or radar or to absorb jammers. Ultra Wideband Suitable for It can exhibit radio wave absorption characteristics.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a broadband ferrite radio wave absorber which can be manufactured more economically in accordance with the demand for widening of the radio wave absorber and having good setting of manufacturing conditions.

In order to achieve the above object, the present invention is to arrange a ferrite magnetic layer of the first layer on the reflective plate, the ferrite magnetic layer of the second layer in the longitudinal and horizontal intervals (a) above the first layer of tile-like ferrite magnetic And arranging the cutting cone column ferrite magnetic material, which is the third layer, on the cylindrical ferrite magnetic material, which is the second layer, and placing the cylindrical ferrite magnetic material, which is the fourth layer, on the cutting cone cylindrical ferrite magnetic material, the third layer, and the cylindrical ferrite material of the second layer. The longitudinal and horizontal spacing (a) of the magnetic material is shorter than the wavelength of radio waves to be used, and the diameter of the cylindrical ferrite magnetic material as the second layer and the lower side of the cutting cone-shaped ferrite magnetic material as the third layer is r ₁ and the cutting cone as the third layer. The diameter of the upper side of the columnar ferrite magnetic body and the diameter of the cylindrical ferrite magnetic body of the fourth layer is r ₂ The height of the tile-like ferrite magnetic body, which is the first layer, h ₁ , The height of the cylindrical ferrite magnetic material, which is the second layer, h ₂ , The height of the cutting cone-shaped ferrite magnetic material, which is the third layer, is h ₃ , and the cylindrical shape is the fourth layer. When the height of ferrite is h ₄ , r ₁ is r ₂ <r ₁ <a, r ₂ is 5 mm <r ₂ <15 mm, h ₁ is 4 mm ≤ h ₁ ≤ 8 mm, and h ₂ is 1 mm. ≤ h ₂ ≤ 5 mm, h ₃ is 10 mm ≤ h ₃ ≤ 20 mm, h ₄ is characterized in that 0.1 mm ≤ h ₄ ≤ 2.5 mm.

The present invention also provides a tile-like ferrite magnetic material as a first layer on a reflecting plate, and a cylindrical ferrite magnetic material as a second layer in the longitudinal and horizontal intervals of a predetermined interval (a) on the tile-like ferrite magnetic material as the first layer, and the cylindrical ferrite as the second layer. A third cutting cone cylindrical ferrite magnetic material is disposed on the magnetic material, and a fourth cutting cylindrical ferrite magnetic material and a fourth lower cutting rotary elliptic ferrite magnetic material are disposed on the third cutting cone cylindrical ferrite magnetic material. The longitudinal and horizontal spacing (a) of the cylindrical ferrite magnetic material, which is a layer, is shorter than the wavelength of radio waves to be used, and the diameter of the cylindrical ferrite magnetic material, which is the second layer, and the diameter of the lower side of the truncated cylindrical columnar ferrite magnetic material, is r ₁ and the third layer is cut. Cylindrical ferrite magnetic body which is the upper side and fourth layer of the conical ferrite magnetic body Diameter of the r _2, wherein the fifth layer undercut rotation oval the lower diameter of the ferrite r _3, said first layer to the other high daily ferrite magnetic material h _1, the second layer, the height of the cylindrical ferrite magnetic material h _2, the third layer r ₁ when the cutting cone columnar ferrite magnetic material elements to increase the h _3, 4 to a layer height of the cylindrical ferrite magnetic material h _4, the fifth layer undercut rotation oval height of the ferrite magnetic material of the h ₅ la is r ₂ <r ₁ <a, r ₂ is 5 mm <r ₂ <15 mm, h ₁ is 4 mm ≤ h ₁ ≤ 8 mm, h ₂ is 1 mm ≤ h ₂ ≤ 5 mm, h ₃ is 12 mm ≤ h ₃ ≤ 22 mm , h ₄ is 0.1 mm ≤ h ₄ ≤ 2.5 mm, _h5 is 1 mm ≤ h ₅ ≤ 5 mm.

The present invention relates to a radio wave absorber in which a tile-like ferrite magnetic body is disposed on a reflecting plate, and a protrusion-absorbing layer having a different material constant is disposed vertically and continuously on the tile-like ferrite magnetic body. The means for changing the material constant is a shape change of a protrusion. It is to control the equivalent permeability and equivalent permittivity to look at the projection by the set value, that is, to control the equivalent permeability and equivalent dielectric constant of the projection by adjusting the diameter, spacing, shape, height and width of the projection. .

In particular, the ferrite magnetic body is formed by forming the projections in the vertical and horizontal intervals of a predetermined interval is good moldability and easy to manufacture, thereby improving productivity. And as a ferrite magnetic body, things, such as a NiZn system and MnZn system, can be used, A sintering type is preferable.

The electromagnetic wave absorber according to the present invention can be used for wall materials installed for preventing interference of TVs and radars by radio wave reflection from buildings or structures such as radio darkrooms, buildings, bridges, etc. used for electromagnetic interference tests and antenna characteristic tests of electronic devices. Can be.

Claims (2)

A tile-like ferrite magnetic material, which is a first layer, is disposed on the reflecting plate, and a cylindrical ferrite magnetic material, which is a second layer, is disposed on the tile-like ferrite magnetic material, which is the first layer, in the longitudinal and horizontal intervals of a predetermined interval (a), and on the cylindrical ferrite magnetic material, which is the second layer. The layered cutting cone ferrite magnetic material is disposed, and the third layer of the cylindrical cutting ferrite magnetic material is disposed on the fourth layer of cylindrical ferrite magnetic material, and the longitudinal and horizontal spacing (a) of the second layer of cylindrical ferrite magnetic material is used. Shorter than the wavelength of radio waves, the diameter of the cylindrical ferrite magnetic material of the second layer and the lower side of the cutting cone-shaped ferrite magnetic material of the third layer r ₁ , the diameter of the upper side of the cutting cone-shaped ferrite magnetic material of the third layer and the fourth the diameter of the cylindrical ferrite magnetic material layer r _2, wherein the first layer, the other routine magnetic ferrite body When the h _1, the second layer, a cylindrical ferrite magnetic material elements to increase the h _2, and the third layer, cutting cones columnar height of the ferrite magnetic material h _3, and the fourth layer, the height of the cylindrical ferrite magnetic material of the height h ₄ d r ₁ is r ₂ <r ₁ <a, r ₂ is 5 mm <r ₂ <15 mm, h ₁ is 4 mm ≤ h ₁ ≤ 8 mm, h ₂ is 1 mm ≤ h ₂ ≤ 5 mm, h ₃ is 10 Broadband ferrite absorber, characterized in that mm ≤ h ₃ ≤ 20 mm, h ₄ is 0.1 mm ≤ h ₄ ≤ 2.5 mm. A tile-like ferrite magnetic material, which is a first layer, is disposed on the reflecting plate, and a cylindrical ferrite magnetic material, which is a second layer, is disposed on the tile-like ferrite magnetic material, which is the first layer, in a longitudinal and horizontal direction at a predetermined interval (a). A layered cutting cone ferrite magnetic material is disposed, and a third cutting cylindrical cylindrical ferrite magnetic material is disposed on the third cutting cone cylindrical ferrite magnetic material, and a lower cutting rotary elliptic ferrite magnetic material, which is the fifth layer, and the cylindrical ferrite magnetic material is the second layer. The vertical and horizontal spacing (a) is shorter than the wavelength of radio waves to be used, and r ₁ is the diameter of the cylindrical ferrite magnetic body, the second layer, and the diameter of the lower side of the cutting cone cylindrical ferrite magnetic body, the third layer, r ₁ , the cutting cone being the third layer. The diameter of the cylindrical ferrite magnetic body, which is the upper side of the columnar ferrite magnetic body and the fourth layer R ₂ , the lower diameter of the lower cut rotary elliptic ferrite, which is the fifth layer, is r ₃ , the height of the tile-like ferrite magnetic material, which is the first layer, h ₁ , and the height of the cylindrical ferrite magnetic material, which is the second layer, is h ₂ , which is the third layer. a conical columnar height of the ferrite magnetic material h _3, the fourth layer, the height of the cylindrical ferrite magnetic material h _4, claim 5 r ₁ when a layer undercut rotation oval height of the ferrite magnetic material h ₅ la is r ₂ <r ₁ <a , r ₂ is 5 mm <r ₂ <15 mm, h ₁ is 4 mm ≤ h ₁ ≤ 8 mm, h ₂ is 1 mm ≤ h ₂ ≤ 5 mm, h ₃ is 12 mm ≤ h ₃ ≤ 22 mm, h ₄ is 0.1 mm ≤ h ₄ ≤ 2.5 mm, h ₅ is 1 mm ≤ h ₅ ≤ 5 mm.