RU2500704C2 - Electromagnetic wave absorber and radar absorbent material for production thereof - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: filler contains discrete carbon fibres in the following ratio, wt %: discrete carbon fibres 40-10, carbonyl iron powder 60-90, with the following ratio of components, wt %: binder 85-15, filler 15-85. The invention also relates to an electromagnetic absorber using said material.

EFFECT: low probability of detecting protected objects and recognition thereof, low weight, thickness and cost of production.

3 cl, 4 dwg

Description

The invention relates to the field of radio engineering, in particular, to materials for the absorption of electromagnetic waves and designs of absorbers, the invention is intended to absorb electromagnetic radiation in land, sea, aviation and space technology, which can increase the stealth of objects and reduce the likelihood of their detection by radars, can be used to create coatings that absorb electromagnetic waves (EMW) microwave frequency range, reducing the magnitude of the power of the reflected signal Ala radar wave in a wide frequency range and as a protective material to reduce the radar visibility of objects of various sizes and configurations in the area of exposure to electromagnetic waves emitted by radars in the microwave range 5-20 GHz.

One of the directions in the creation of absorbers of electromagnetic waves and radar absorbing materials for their manufacture is the creation of electrodynamic materials based on the synthesis of a layered structure having specified electrophysical properties, for example, a given level of reflection of radio waves in a certain frequency range. In this case, it is desirable that such a structure has a minimum thickness and mass.

Known synthetic dielectric material, broadband absorption and reflection (radar absorbing material), described in the invention according to the patent US 5298903, class. H01Q 17/00, containing synthetic material with ellipsoid Rayleigh reflectors distributed in it with a maximum linear size smaller than the smallest wavelength in a given frequency range. Rayleigh particles are an insulator coated with a thin metal shell. The thickness of the material selected is greater than the maximum wavelength of the working strip in the synthetic material.

The disadvantages of this material include the great complexity of applying a metallization layer on insulators, the high cost of its manufacture and the complexity of applying to the protected object.

The closest in technical essence and purpose to the claimed radar absorbing material is the material described in the patent (RU 2107705 C1, CL C09D 5/32; C08K 3/10, publ. 03/27/98). It uses a synthetic adhesive "Elaton" as a polymer binder, and powdered ferrite or carbonyl iron in the ratio, wt.%: "Elaton" - 80-20; magnetic filler 20-80.

The radar absorbing material (RPM) used in the prototype provides EMF absorption in a limited frequency range, mainly at the upper frequencies of the radar stations operating range, has uneven absorption, weak at the beginning of the range at 5–9 dB and slightly higher at the higher frequencies 15– 20 dB

A known absorber of electromagnetic waves (EMW) (patent US 5561428, CL H01Q 17/00), including a polymer binder and a filler, which is made in the form of randomly oriented threads forming a three-dimensional porous structure, while a conductive layer is applied to part of the threads .

The disadvantages of this absorber include the complexity of applying a conductive layer to the filaments and the formation of a uniform three-dimensional filament filament structure from the filaments.

The main disadvantages of such absorbers are: large weight and dimensions (thickness), a small degree of absorption of electromagnetic waves, as well as a high reflection coefficient. The latter is due to the absence of smooth decay of electromagnetic waves as they pass through the absorber.

Also known is a multilayer EMF absorber made in three layers: the outermost layers are made of dielectric materials, and the middle layer located between them is made of electrically conductive material (AS No. 1786567, class H01Q 17/00, publ. 07.05.90, publ. 07.01. 93).

A disadvantage of the known absorber is the relatively high reflection coefficient due to the non-smooth matching of the dielectric constant of dielectric materials with the dielectric constant of the external environment (air) and inefficient absorption of electromagnetic waves in the entire wavelength range.

As a prototype, an ultra-wide range absorber of electromagnetic waves is selected, consisting of fixed on a metal substrate: a layer of dielectric material made on the basis of radar absorbing foam glass, a layer of magnetic material made of radar absorbing nickel-zinc ferrite (RF patent No. 21010122, priority from 11.03.1997 g, publ .27.04.1998 g). At the same time, the total thickness of the absorber is large and varies from 210 to 365 mm depending on the embodiment.

The disadvantage of the prototype is the use of magnetic material from radio-absorbing nickel-zinc ferrite, which has a significant mass (8-15 kg / m2), high cost, low mechanical strength and heat resistance, so it can not be used in miniature electronic devices. Also the disadvantages of this technical solution include the low values of specific attenuation in all layers of the absorber, the high level of reflection of electromagnetic waves, especially in the upper part of the frequency range of absorbed electromagnetic waves. Thus, the scope of this absorber is significantly limited, in particular, its use for protecting biological objects, for radio masking armored vehicles, vehicles, aircraft and light class ships is excluded.

The technical problem to which the invention is directed is to reduce the probability of detection of protected objects and their recognition, by expanding the frequency range from 5 to 20 GHz of absorbed electromagnetic waves from stationary and mobile radars and reducing the power level of the reflected signal. And also, reducing the weight, thickness and cost of the absorber of electromagnetic waves.

The specified technical result is achieved by the fact that in the known radar absorbing material containing a polymeric binder and a powdery filler, the filler is made of two components - from discrete carbon fibers (OIL) and powdered carbonyl iron (QL). An epoxy resin was used as a polymer binder, with the following ratio of components, wt.%: Epoxy resin 85-15, discrete carbon fibers and powdered carbonyl iron 15-85. A mixture of discrete carbon fibers and carbonyl iron consists in the following ratio of components, wt.%: Discrete carbon fibers 40-10, powdered carbonyl iron 60-90.

Discrete carbon fibers are used in the form of randomly oriented strands of 10-50 microns in size, and carbonyl iron is used in the form of spherical particles with a diameter of 10-20 microns.

The use of discrete carbon fibers leads to the appearance of specific atomic-molecular structures in the composite material, in which fluctuations of the dielectric constant occur, leading to a significant increase in the dissipation of microwave power in the composite material.

The presence of randomly oriented and randomly located in the volume of the polymer binder filler particles of various sizes, different dielectric and magnetic permeability, leads to the formation of scattering structures of various sizes, which, in turn, leads to the expansion of the working frequency range of the proposed material.

The problem is achieved in that in the known absorber of electromagnetic waves, consisting of dielectric and radar absorbing materials and a metal substrate, the dielectric material is made in the form of a plate of alumina ceramic, on the outer surface of which a polymer dielectric film is deposited, behind it is a radar absorbing material, consisting of two layers, the first layer is made of a mixture of a polymer binder and a filler of powdered carbonyl iron in the following ratio ponents, wt.%:

- binder - 80-20

- filler - 20-80,

and the second layer is a mixture of a polymer binder and a filler, consisting of powdered carbonyl iron and discrete carbon fibers in the ratio, wt.%:

- discrete carbon fibers - 40-10

- powdered carbonyl iron - 60-90

in the following ratio of components, wt.%:

- binder - 85-15

- filler - 15-85,

wherein a second layer is applied to a metal substrate. The invention is illustrated by the following drawings:

Figure 1 and figure 2 presents a diagram of the attenuation of the level of microwave power and the level of the reflected wave in the frequency range 5-20 GHz when using RPM from a composite filler of different composition. In Fig. 1, the filler is made of powdered carbonyl iron, and in Fig. 2 of carbonyl iron and discrete carbon fibers. Measurements and tests were carried out according to the method described in GOST R 50011-92.

Figure 3 presents a diagram of a device for measuring reflection of electromagnetic waves, where:

- P - reflective plate;

- A - horn antenna;

- H01, H02 - taps;

- B1, B2 - valves;

- PV - tunable phase shifter;

- ATT - tunable attenuator;

- D is the divisor;

- G - generator;

- IM - power meter.

Figure 4 shows in cross section an absorber of electromagnetic waves and, included in its structure, as a component, a radar absorbing material. In addition, the mechanism of the passage of electromagnetic waves through the layered structure of the absorber and the subsequent reflection of electromagnetic waves from each layer into the surrounding space are illustrated. The absorber comprises a first outer layer of dielectric material 1, a second layer of dielectric material 2, a first layer of radar absorbing material 3, a second layer of radar absorbing material 4 and a metal substrate 5.

The outer layer of the dielectric material 1 is made of a polymer dielectric film of polyethylene terephthalate (GOST 24234-80) with a thickness of 0.2 mm, the second layer of dielectric material 2 is made in the form of a plate of alumina ceramic 10 mm thick. The first layer of the radar absorbing material 3 with a thickness of 2 mm is a polymer binder based on epoxy resin and a filler of powdered carbonyl iron. The second layer of the radar absorbing material 4 with a thickness of 2 mm is an epoxy resin binder with carbonyl iron conductive particles distributed therein with the addition of discrete carbon fibers. The entire layered structure is connected to a metal substrate 5, which is made of armored steel 2 mm thick.

The measurements of the radio absorbing properties were carried out in two stages. At the first stage, the radio-absorbing properties of calibrated samples in the form of rings made of compositions based on epoxy resin, epoxy resin with different concentration of QOL, epoxy resin with different concentration of OIL of epoxy resin with different concentration of QOL and OIL in the coaxial waveguide path were studied, and in the second stage, the radio-absorbing and radio-reflecting abilities of the selected compositions of the layers based on epoxy resin with different concentrations of QOL and OIL applied in one case to a metal were studied a 200 × 200 mm panel, and in the second case, 16 pieces of ceramic armor plate measuring 50 × 50 × 10 mm, which were then joined by a metal panel 200 × 200 mm in size.

The reflection coefficient shows the fraction of energy reradiated in the direction of the EMW source. The magnitude of the attenuation of electromagnetic energy estimates the ratio of the levels of incident electromagnetic energy and in the region of space behind the sample. The processes of reflection of electromagnetic waves from the interface between two media with different electromagnetic characteristics and absorption of EMW energy in the volume of the material due to various mechanisms characterize the effectiveness of shielding electromagnetic radiation.

A study of the shielding properties of the obtained composite materials based on epoxy resin with different concentrations of OIL and epoxy with different concentrations of QOL and OIL was performed in the range of 5 ... 20 GHz using a panoramic meter of the standing wave coefficient by voltage (VSWR) and attenuation and waveguide measuring path.

The VSWR is related to the Kotr reflection coefficient as follows:

VSWR = 1 + Kotr / 1-Kotr.

The above characteristics are obtained for a two-layer material with a thickness of 4 mm, including the 1st and 2nd layers of the same thickness equal to 2 mm. When measuring the reflection coefficient of the microwave signal, the absorbing layer is deposited on a metal base. The filler is made in two layers: the first layer of 2 mm consists of an epoxy resin and a mixture of discrete carbon fibers and powdered carbonyl iron in the following ratio of components, wt.%: Epoxy resin - 25, discrete carbon fibers - 10, powdered carbonyl iron - 65, respectively, the second layer 2 mm from epoxy resin and powdered carbonyl iron in the ratio of components, wt.%: Epoxy resin - 20, powdered carbonyl iron - 80, respectively.

The measurements were carried out in the frequency range 5–20 GHz. Analysis of the measurement results was carried out on the experimentally obtained values of the transmission and reflection coefficients of the studied RPMs. During measurements, a metal panel was installed behind the samples. It was found that the proposed design of the absorber in the frequency range 5-20 GHz attenuates electromagnetic radiation at a frequency of 5 GHz by -6 ... -12 dB with a coefficient of reflection of -0.8 ... -4 dB and at a frequency of 20 GHz weakens electromagnetic radiation coefficient by -26 ... -40 dB when the reflection coefficient is -3.2 ... -1.8 dB.

The graphs (figure 1 and figure 2) show the obtained frequency dependences of the reflection coefficients of the studied samples of radar absorbing materials in the frequency range 5-20 GHz.

The reflection coefficient of the proposed design of the absorber in the frequency range 5-20 GHz was measured as follows:

A square plate 200 × 200 mm in size made of the material to be studied is mounted perpendicular to the axis of the horn antenna irradiating it, which is also the receiving antenna of the reflected wave from the square plate. The distance from the plate to the antenna is 50-60 cm. A special device provides the ability to smoothly measure this distance. The type of antenna used is P6-12.

The wave radiated by the antenna is reflected from the plate, then from the antenna (due to the mismatch of the latter with space) and the plate one, two, three, and so on, to infinity times, forms the total wave received by the antenna. The microwave signal received by the antenna will have an amplitude

, $$A=\frac{U\left(\mathrm{one}-{\rho }^2\right)\alpha k}{\left|\mathrm{one}-\alpha k\rho \beta e^{-j\left(\varphi -\Delta p-\Delta x\right)}\right|}$$

,

where U is the amplitude of the radiated antenna signal

ρ ² - the reflection coefficient of the wave from the antenna (power),

α - for the power of the radiated antenna wave incident on the plate,

k is the desired reflection coefficient of the plate (in amplitude),

β is the fraction of the power reflected from the plate of the wave incident on the antenna,

Δp is the phase increment when the wave is reflected from the antenna,

Δx is the phase increment upon reflection of the wave from the plate,

$$\phi =2\pi \cdot \frac{2l}{\lambda },$$

l is the distance from the antenna emitter to the plate, λ is the wavelength.

до A_max $$A=\frac{U\left(1-{\beta }^2\right)\alpha k}{1-\alpha k\beta \rho }.$$

It follows from the above expressions that, during a smooth measurement, the distance from the antenna to the plate at λ / 2, the amplitude of the received signal runs through the entire set of values from A _min $$A=\frac{U\left(\mathrm{one}-{\beta }^2\right)\alpha k}{\mathrm{one}+\alpha k\beta \rho }$$

up to A _max $$A=\frac{U\left(\mathrm{one}-{\beta }^2\right)\alpha k}{\mathrm{one}-\alpha k\beta \rho }.$$

Using equipment connected to the antenna, the measured values of V _min and V _{max are} proportional to A _min and A _max, respectively. As a result, we have two relations

и $$V_{\max }=M\frac{U\left(1-{\beta }^2\right)\alpha k}{1-\alpha \beta \rho k}\left(1\right)$$

$$V_{\min }=M\frac{U\left(\mathrm{one}-{\beta }^2\right)\alpha k}{\mathrm{one}+\alpha \beta \rho k}$$

and $$V_{\max }=M\frac{U\left(\mathrm{one}-{\beta }^2\right)\alpha k}{\mathrm{one}-\alpha \beta \rho k}\left(\mathrm{one}\right)$$

Next, a plate made of the test material is replaced with a plate with the same dimensions made of a material with a known reflection coefficient k _o . Usually this is a metal plate, the reflection coefficient of which is taken equal to unity.

As described above, for this plate we obtain two relations

и $$V_{\max }=M\frac{U\left(1-{\beta }^2\right)\alpha k_o}{1-\alpha \beta \rho k_o}\left(2\right)$$

$$V_{\min }=M\frac{U\left(\mathrm{one}-{\beta }^2\right)\alpha k_o}{\mathrm{one}+\alpha \beta \rho k_o}$$

and $$V_{\max }=M\frac{U\left(\mathrm{one}-{\beta }^2\right)\alpha k_o}{\mathrm{one}-\alpha \beta \rho k_o}\left(2\right)$$

Relations (1) and (2) are solved with respect to the unknown k in the form

$$k=k_o\frac{v_{\max }\left(\mathrm{one}+\frac{v_{\max }}{v_{\min }}\right)}{v_{\max }\left(\mathrm{one}+\frac{v_o{}_{\max }}{v_{o\min }}\right)},\left(3\right)$$

According to the formula (3), the reflection coefficient to the material under study is calculated according to the measurement data V _max , V _min , V _omax , V _omin .

The scheme of the device for measuring the magnitude of V _max , V _min , V _omax , V _omin is presented in _Fig.3 .

Directional couplers and valves are used to separate the signal emitted through the antenna that irradiates the plate and the received signal. Through the output 1 of the directional coupler H01, the signal received by the antenna is fed to the MI power meter. As a value of V, proportional to the amplitude of the received signal, the square root of the measured power value is taken.

To exclude the influence on the measurement results of the signal going to the radiation, which together with the received signal can pass to the output 1 of the H01 directional coupler, the device has a compensation channel that includes the output 2 of the H02 directional coupler, tunable attenuator ATT, and tunable phase shifter ФВ. On dividers D, the signals of the measuring and compensation channels are added, after which it is fed to the power meter of the MI.

Compensation of the measured signal penetrating through the measuring channel is carried out with the reflecting plate removed by setting such attenuation and phase rotation of the signal in the compensation channel, in which the power meter indicates zero power.

Measurements of the reflection coefficients of known materials of flan and plexiglas with the characteristics known from reference books and technical conditions, carried out by the method described above, yielded results that practically coincided with theoretical calculations.

The above characteristics are obtained for the inventive multilayer RPM with a total thickness of approximately 14 mm

When measuring the reflection coefficient of the microwave signal, the absorbing layer is deposited on a metal base. The filler is made of two layers: the first layer of 2 mm consists of an epoxy resin and a mixture of discrete carbon fibers and powdered carbonyl iron in the following ratio of components, wt% :, epoxy resin - 25, discrete carbon fibers - 10, powdered carbonyl iron - 65, respectively. The second layer with a thickness of 2 mm is applied to the 1st layer and consists of epoxy resin and powdered carbonyl iron in the ratio of components, wt.%: Epoxy resin - 20, powdered carbonyl iron - 80, respectively.

The use of an epoxy resin as a polymer binder base, for example, of the ED-20 grade (GOST 24709-81) makes it possible to apply radar absorbing material to a ceramic base. In this case, coatings are obtained from a thin-layer radar absorbing material with high absorbing properties, with a microwave signal attenuation value of 5-10 dB / mm, which can be used to create radar absorbing anti-radar panels, including for mobile objects and vehicles.

Examples of the invention:

The radar absorbing material is prepared by mechanically mixing the components immediately before applying it to the surface to be coated. First, all the components that make up the RPM are weighed, then the mixture of excipients from OIL and QL is poured into the epoxy resin and mixed using a propeller mixer, after which a hardener is added to the resulting composition, again the mixture is thoroughly mixed in the propeller mixer and then the finished composition is applied to Ceramic armor plate placed in a special injection mold. After this 1st layer hardens, its surface is milled to provide a given thickness of 2 mm. Then, in a similar way, the mixture is prepared for the 2nd layer, which is then applied by casting in the same form to the milled surface of the 1st layer. The result is a RPM with a total thickness of 4 mm.

Depending on the required value of reducing the level or power of the reflected electromagnetic wave, appropriate ratios of the components of the filler are prepared.

The composition of the formulations is presented below.

1st layer formulation

The ratio of components, wt.%:

epoxy resin 85-15

filler in the form of a mixture of discrete carbon fibers and powdered carbonyl iron 15-85, a mixture of powdered carbonyl iron and discrete carbon fibers is made in the following ratio of components, wt.%:

discrete carbon fibers 40-10,

powdered carbonyl iron 60-90

2nd layer formulation

The ratio of components, wt.%:

epoxy resin 80-20

powdered carbonyl iron 20-80

An absorber with layers deposited according to the specified recipes can be used as part of various designs of military equipment and special devices, where it is required to ensure the absorption of EMW of increased efficiency.

In the proposed absorber design, as EMW penetrates from the inside to the inside, in the direction from the outer layer to the inner layers, the dielectric constant of the radar absorbing layers increases, the resistivity of the layers of the polymer binder and powder fillers of carbonyl iron and of a mixture of discrete carbon fibers and carbonyl gland. At the same time, the radar absorbing and reflecting properties of the absorber depend on the distance between the layers and on the permeability values associated with the value of the loss tangent and with the resistivities of the absorbing materials.

The thickness of the layers determines the weight of the absorber, diffraction scattering of the incident radiation, interference absorption damping, and the efficiency of re-reflection of radio waves between the layers. The design of the absorber is technological, has a small weight and allows for absorption in a wide frequency band when using the required number of absorbing layers. Thus, with a layer-by-layer distribution of the required permeability values, taking into account their frequency dispersion, conditions are created for the EMW to enter the material with minimal reflection. With further movement of the EMW toward the metal, its absorption, refractive index, scattering, and compression increase, but reflection continues to decrease.

A comparable analysis of the claimed solution with the prototype shows that the claimed EMF absorber differs from the known one in that the dielectric material is made composite in the form of an alumina ceramic plate with a polymer dielectric film deposited on the outside, the radar absorbing material is made of 2 layers, and the 1st the layer behind the dielectric material is a polymeric binder and powdery carbonyl iron filler, and the second layer between the first layer and the metal substrate, it is a polymer binder and a powdery filler from a mixture of discrete carbon fibers and carbonyl iron, which have a large loss tangent that reaches several tens of units, which is necessary for effective attenuation of radio waves in a wide frequency band.

The proposed design of the absorber has a low weight and high efficiency of reducing the reflection coefficient.

The absorber operates as follows.

A direct electromagnetic wave (wave B1) enters the outer layer of dielectric material in the form of a polymer dielectric film 1 bordering the air and having a small dielectric constant (Fig. 4), while the wave is slightly reflected from the front surface (wave B2). Next, the wave enters the dielectric material in the form of a plate of alumina ceramic 2, which has a slightly larger dielectric constant than a polymer dielectric film. Reaching the interface between ceramics 2 and the radar absorbing material 3, the wave partially reflects (wave B4), and most penetrates the first layer of the radar absorbing material 3, which consists of a polymer binder based on epoxy resin and a powdery carbonyl iron filler, undergoes a slight attenuation due to due to diffraction scattering, interference, absorption and re-reflection (waves B4-1 and B4-2). Next, the electromagnetic wave enters the second radar absorbing material 4 in the form of a polymer binder and a powdery filler from a mixture of discrete carbon fibers and carbonyl iron. Reaching the interface between the layer of the radar absorbing material 4 and the metal substrate, the wave is partially reflected (wave B5-1), and part of it, as it penetrates into the second layer of the radar absorbing material 4, is reflected from the metal substrate and goes outside (wave B5-2).

Such complex energy dissipation occurs at the boundary of each absorbing layer, both radiolucent and insulating, but with different intensities. The closer the absorbing layer to the metal, the greater the scattering intensity, since the subsequent layers are made of materials with decreasing resistivities and increasing dielectric constants. In this regard, the complex energy dissipation of radio waves in the absorber increases almost to their complete attenuation.

Thus, the design of the absorber due to the multilayer ™ and the use of a combination of carbonyl iron and discrete carbon fibers is effective in a wide range of wavelengths and is minimal in thickness and weight compared to the prototype. This is facilitated by the use of layers of materials in absorbing coatings with decreasing resistivities and increasing dielectric constants. The external polymer dielectric film is made of polyethylene terephthalate, the dielectric constant of which is 2.54-4.0, and the dielectric constant of the aluminum oxide ceramic plate following the path of penetration of the EMW is 8.0-10.0.

The radar absorbing material located behind the dielectric material, which is a polymer binder and a powdery filler made of carbonyl iron, has a low resistivity, and the second layer, located between the 1st layer and a metal substrate and representing a polymer binder and a powdery filler from a mixture discrete carbon fibers and carbonyl iron, also has a low resistivity.

A part of the electromagnetic wave incident on the material from the microwave energy space is absorbed by converting the molecules of the filler material into the energy of thermal motion, and a part is randomly reflected into the space. All particles of a filler distributed in a polymer base, which are elementary emitters with wide radiation patterns, repeatedly participate in rereflection. The re-reflection of an electromagnetic wave is not specular, but diffusely scattered. An absorber containing dielectric fibers, a polymer binder and absorbing elements located in separate layers, for example carbonyl iron powder and discrete carbon fibers, the concentration of which increases in the direction from the outer layer to the metal, allows for minimal reflection and maximum absorption of electromagnetic waves.

The use of the invention reduces the visibility of the protected object in the radar range of electromagnetic waves (EMW). The production and use of the inventive material does not impose strict requirements on personnel safety and technological equipment, because All materials used are non-toxic.

The use of discrete carbon fibers leads to the appearance of specific atomic-molecular structures in the composite material, in which fluctuations of the dielectric constant occur, leading to a significant increase in the dissipation of microwave power in the composite material based on the difference in permittivity.

The use of powdered carbonyl iron leads to the formation of irregular structures in the composite material in which fluctuations of magnetic permeability occur, which also lead to the dissipation of microwave power based on the difference in magnetic permeability.

The use of discrete carbon fibers can significantly increase the absorption properties of RPM. The use of powdered carbonyl iron significantly reduces the reflection of electromagnetic waves from RPM.

The use of a two-layer or multilayer absorber from thin layers of composite materials allows you to create RPM structures with absorption of microwave power - 40 dB and a small intrinsic reflection coefficient in RPM with a thickness of several millimeters.

The technical result achieved by the implementation of the invention is to create an RPM that will reduce the power of the reflected EMP signal (reflected electromagnetic wave from the object) in the direction of the irradiating radar by 10-30 dB (depending on the required magnitude of reduction) in relation to the level or power of the scanning electromagnetic wave of the radar and reducing the likelihood of detecting or classifying objects, expanding the frequency range from 5 GHz to 20 GHz absorption of EMP and ensuring the adequacy of absorption of EMP in frequency range 5-20 GHz.

In addition, the use of an aluminum oxide ceramic plate in the design of the absorber additionally provides bulletproof design, which allows to expand the scope of the proposed absorber due to this technical characteristic, in particular for various military equipment.

Claims (3)

1. Radar absorbing material containing a polymeric binder and a filler, consisting of powdered carbonyl iron, characterized in that discrete carbon fibers are introduced into the filler in the ratio, wt.%:
discrete carbon fibers 40-10 powdered carbonyl iron 60-90
in the following ratio of components, wt.%:
binder 85-15 filler 15-85 2. The radar absorbing material according to claim 1, characterized in that it contains an additional layer consisting of a polymer binder and a filler made of powdered carbonyl iron, in the following ratio of components, wt.%:
binder 80-20 filler 20-80 3. The absorber of electromagnetic waves, consisting of a dielectric and radar absorbing materials and a metal substrate, characterized in that the dielectric material is made in the form of a plate of alumina ceramic, on the outer surface of which a polymer dielectric film is deposited, behind it is a radar absorbing material, consisting of two layers, the first layer is made of a mixture of a polymer binder and a filler of powdered carbonyl iron in the following ratio of components, wt.%:
binder 80-20 filler 20-80
and the second layer is a mixture of a polymer binder and a filler, consisting of powdered carbonyl iron and discrete carbon fibers in the ratio, wt.%:
discrete carbon fibers 40-10 powdered carbonyl iron 60-90
in the following ratio of components, wt.%:
binder 85-15 filler 15-85
moreover, the second layer is connected to a metal substrate.

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