RU2362220C1 - Device for absorbing electromagnetic radiation - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to devices for absorbing electromagnetic radiation and can be used in anechoic chambers, used for testing radio-, tele-, and other electrical devices. The invention is aimed at reducing weight and reflection coefficient of a device, which is made possible due to that, the device comprises a metallic shield, ferrite layer, a dielectric layer without dielectric losses placed between them and a matching dielectric packet of radar absorbing material made from dielectric layers with carbon filler. The carbon filler for the layers is in form of semiconducting vibrators. There are not less than ten layers and they have the same thickness. The first two layers of the matching packet do not have dielectric loss. In the dielectric of the next layers, there are vibrators, which provide for dielectric loss, concentration values of which, starting from the third to the middle layer, increase from 0.3·10^-5±5% to an extreme value for the middle layer, equal to 2·10^-5±5%. Concentration values of the semiconducting vibrators then decrease. The concentration value of semiconducting vibrators for the last layer is equal to concentration of vibrators of the third dielectric layer of the matching packet.

EFFECT: reduced weight and reflection coefficient of the device.

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Description

The invention relates to the field of microwave technology, namely, to absorbers of electromagnetic radiation for equipping them with anechoic chambers used for testing radio, television, and other electrical devices.

A known absorber of electromagnetic radiation, which is made in the form of three layers: the outer and lower of the dielectric materials and the middle layer of electrically conductive material located between them. The disadvantages of the absorber include a narrow operating frequency range (Aut. St. No. 1786567, H01Q 17/00, Bull. No. 1, 01/07/93).

A known absorber of electromagnetic radiation, which consists of dielectric fibers and a polymeric binder and of conductive absorbing elements located in the active layers (Patent RU No. 2231181, H01Q 17/00, Bull. No. 17, 06/20/2001). The dielectric constant of the elements increases from the outer active layer to the active inner layers and metal. Absorbing elements are made of carbon-graphite fabric and form diffraction gratings. This absorber operates in a narrow frequency range.

The closest technical solution for the design and the achieved result (prototype) is "Device for the absorption of electromagnetic radiation" (RU, US Pat. No. 2169952, G12B 17/00, H01Q 17/00, H05K 9/00, Bull. No. 18 dated 27.06. 01). This device consists of a ferrite substrate and a matching dielectric layer with a carbon filler deposited on it. Matching dielectric layer is a layered structure consisting of flat layers of sound-absorbing material of different densities, and the density of the layers decreases with distance from the ferrite substrate. The device operates in a wide frequency range from 20-30000 MHz and has sound-absorbing properties, but has a large weight due to the large thickness of the 65 mm ferrite substrate.

The technical result of the invention is the creation of a broadband device for absorbing electromagnetic radiation, reducing its weight and reflection coefficient in the frequency range, as well as simplifying the manufacturing technology and mounting on the walls of anechoic chambers (BEC).

The design of the device for absorbing electromagnetic radiation (EMP) is illustrated by drawings and a table.

Figure 1. Device design. Designations are introduced: 1 - a flat metal screen; 2 - a flat dielectric layer of material without dielectric loss; 3 - flat ferrite layer; 4 - a flat package of dielectric radar absorbing material (RPM).

Figure 2. Graphs of changes in the values of the reflection coefficient in the frequency range for the inventive device (solid curve) and the prototype device (dashed curve). On the ordinate axis of the graphs the reflectance values of the claimed device and prototype are plotted, on the abscissa axis is the frequency range in MHz.

Figure 3. Table. The concentration of semiconductor vibrators in the dielectric layers of a flat packet of dielectric material. The following notation is introduced in the table: No. of a layer of a flat package RPM 4; K is the concentration of semiconducting vibrators in the dielectric layers of a flat package RPM 4.

The device for absorbing electromagnetic radiation (Fig. 1) consists of a flat metal screen 1, a flat ferrite layer 3, a flat dielectric layer without dielectric loss 2, located between the screen 1 and the shadow side of the ferrite layer 3, and a flat matching RPM dielectric package 4. The device for EMP absorption is made in the form of a rectangular parallelepiped.

As the metal screen 1, sheet metal, for example sheets of iron, a metal foil or a metal wall of the BEC, on which the absorption device is mounted, can be used.

The flat dielectric layer 2 is made of lossless dielectric with a thickness of 9.0-9.5 mm, for example, of particleboard (chipboard) or fiberboard (MDF) and is placed between the screen 1 and the shadow side of the ferrite layer 3.

Flat ferrite layer 3 is made of adjacent adjacent to each other square ferrite tiles with a thickness of 6.6 ± 0.1 mm with dimensions of width and length 60 × 60 ± 0.1 mm.

Matching dielectric package RPM 4 consists of at least 10 flat dielectric layers of the same thickness with varying relative permittivity in the frequency range. The RPM 4 package is attached on the EMR-lit side of the ferrite layer 3.

The first two dielectric layers of matching packet 4, counting from the ferrite layer, have no dielectric losses.

The subsequent dielectric layers of packet 4 are filled with semiconducting vibrators made of carburized viscose filaments randomly distributed in the dielectric material with an average thickness of 0.009 mm, a length of 9-10 mm, and a specific volume resistance of 0.008 ± 5% Ohm · cm and have the same concentration in one layer. Vibrators provide dielectric losses in the layers of the package 4.

The concentration of vibrators K, starting from the third to the middle dielectric layer of the matching package 4, increase from 0.3 · 10 ^-5 ± 5% to the extreme value of their concentration of the average dielectric layer of the matching package, equal to 2 · 10 ^-5 ± 5%, and then the concentration value decreases, and the concentration value of the semiconducting vibrators of the last layer of the matching package 4 is equal to the concentration of vibrators 3 of the dielectric layer of the matching package 4. This law changes the concentration of vibrators, together with the use of dielectric one layer 2 between the screen 1 and ferrite layer 3 aligns ferrite with free space, whereby the reflection coefficient of the apparatus is less than the prototype, in the entire frequency range 30-18000 MHz (Figure 2).

When mounting the device for absorbing electromagnetic radiation on the inner metal surface of the anechoic chamber (BEC), which in this case serves as the screen 1 of the device for absorbing electromagnetic radiation, the ferrite tiles are glued to the fiberboard panel in advance. The panel is bolted to the BEC flat metal surface. A flat-layered matching dielectric package 4 is glued onto the ferrite surface.

Practical implementation of the invention.

A batch of prototypes of an EMP absorption device was manufactured. The prototype device (Fig. 1) consists of a flat metal screen 1, a flat dielectric 2, a flat ferrite layer 3 of ferrite tiles and a matching package 4. The prototype device is made in the form of a rectangular parallelepiped with a thickness of 350 mm and a square base with dimensions 600 × 600 mm (Fig. 1).

As the metal screen 1, aluminum foil 0.1 mm thick, 600 × 600 mm wide and long was applied, which is glued to the shadow side of the dielectric layer 2. The flat dielectric layer 2 is made of fiberboard 9.5 mm thick.

The flat ferrite layer 3 is made of adjacent ferrite plates 6.6 mm thick, with a width and length of 60 × 60 mm, made of ferrite brand "Ferrilen", which is glued to the other side of a flat dielectric layer 2.

Matching dielectric package RPM 4 consists of 11 flat dielectric layers with a thickness of 30 mm each with a relative complex dielectric constant that varies from frequency, which is glued to the EMR illuminated side of the ferrite layer 3.

The first two dielectric layers of matching packet 4, counting from the ferrite layer 3, have no dielectric losses and are made of foamed asbestos.

The dielectric layers from the 3rd to the 11th matching package 4 are made of foamed asbestos with randomly distributed semiconducting vibrators in it from carbonized viscose filaments with a thickness of 0.009 mm, a length of 10 mm and a specific volume resistance of 0.008 Ohm · cm. The concentration of vibrators in one layer is the same.

The values of the optimal concentration of semiconducting vibrators for each dielectric layer with losses were obtained by calculation. The calculation results are shown in the table of figure 3. From this table it can be seen that the concentration of vibrators, starting from the third to the middle layer of the packet, increases from 0.3 · 10 ^-5 to the extreme value of the concentration of the middle layer of the packet, equal to 2 · 10 ^-5 , and then the concentration value of the semiconductor vibrators decreases, and the concentration value of the semiconducting vibrators of the last layer is equal to the concentration of vibrators of 3 layers. Such a law of changing the concentration of vibrators, together with the use of a dielectric layer 2 between the screen 1 and the ferrite layer 3, ensured the coordination of the device for absorbing EMR with free space.

The reflection coefficient of the absorption device was minimized by calculation using the iteration method in the frequency range from 30 to 18000 MHz. After manufacturing the device according to the calculation results, the real reflection coefficient was measured over the entire frequency range using a broadband reflectometer. The results of the experiment are shown in figure 2 (broken solid line). For comparison, the same drawing shows a graph of the reflection coefficient of the prototype in the same frequency range (broken dashed line). As can be seen from these graphs, the reflection coefficient of the claimed device in the entire frequency range is less than that of the prototype.

The composition of the Ferrite brand ferrite used and its manufacturing technology ensure the absorption of EMP in the operating frequency range of 30-1800 MHz between the resonance of domain walls and natural ferromagnetic resonance, where the real part of the magnetic permeability is an even frequency function and the imaginary part is odd, with the main term being the product of saturation magnetization times the anisotropy field divided by the frequency.

Before mounting samples of the device for absorbing EMR onto the inner metal surface of the anechoic chamber (BEC), ferrite tiles were glued to a fiberboard panel, on the other side of which aluminum foil was glued. A flat-layered matching dielectric packet 4 was glued onto the ferrite surface.

Compared with the prototype in the device made according to the invention, the thickness of the ferrite layer is significantly reduced, which significantly reduced the mass of ferrite (8 times). The presence of a panel made of fiberboard - lossless dielectric layer 2, provided the required gap of 9.5 mm between the ferrite and the metal screen, necessary to increase the absorption of electromagnetic radiation at frequencies of more than 300 MHz, and simplified the installation of the absorbing device on the walls of the BEC. The presence of two lossless dielectric layers (1st and 2nd) in matching package 4 of the proposed device significantly increased the absorption of EMR in the ferrite layer in the resonance region.

The technical result of the invention is achieved, a broadband device for absorbing electromagnetic radiation is created, its weight and reflection coefficient are reduced. Simplified manufacturing techniques for an EMR absorption device and mounting on BEC metal walls.

Claims (1)

A device for absorbing electromagnetic radiation, consisting of a ferrite layer and the side of the matching dielectric package of a radio-absorbing material from carbon-filled dielectric layers placed on it with the light of electromagnetic radiation, characterized in that a metal screen and a dielectric layer without dielectric losses are inserted between the screen and the shadow side of the ferrite layer, in addition, the carbon filler of the layers of the matching dielectric package radio The material is made in the form of semiconducting vibrators, and the number of layers in the matching dielectric package is not less than ten that have the same thickness, in addition, the first two layers of the matching package of the radar absorbing material have no dielectric losses, and the semiconductors are introduced into the dielectric of the subsequent layers of the matching radar absorbing material package. dielectric loss vibrators whose concentration values are from the third to the middle layer of the matching dielectric package radar absorbing material, increase from 0.3 · 10 ^-5 ± 5% to an extreme value of the middle layer of the package equal to 2 · 10 ⁵ ± 5%, and then the concentration values of the semiconductor vibrators decrease, and the concentration value of the semiconductor vibrators of the last layer is equal to the concentration of the third vibrators the dielectric layer of the matching package of radar absorbing material.

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