RU2447551C1 - Dead room - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: in a proposed room, ferrite plates are made of magnesium-zinc ferrites, electromagnetic properties of which are close to properties of nickel-zinc ferrites. The proposed dead room comprises walls forming a closed volume, inside which there is an electric tight metal screen attached to inner walls, at the same time on the walls there are metal bases installed with fixed ferrite plates made of magnesium-zinc ferrite with additives of titanium and strontium oxides, at the appropriate weight ratio of components. Above ferrite plates there are construction sound-insulation panels.

EFFECT: increased radio-absorbing properties of a dead room, preferably in the range of frequencies from 30 MHz to 1000 MHz, reduction of cost of its manufacturing due to application of manganese-zinc ferrite plates.

1 ex, 1 tbl, 1 dwg

Description

The invention relates to radiophysics and may find application in the construction of premises with increased requirements for isolation from sound and radio signals. An object of the invention is the creation of an anechoic chamber, which ensures the exclusion of radiation from the chamber of sound and radio signals, as well as the exclusion of reflection from the chamber walls of sound and radio signals of frequencies from 30 MHz to 1000 MHz.

A known construction of an anechoic chamber, the walls of which are covered with plates of magnetic material (see Japan Patent No. 26143, class 98 (3) D 6, published 1968). Thickness of the plates is chosen to be _^1/2 wavelength in free space. This camera provides absorption of electromagnetic waves in the range of 300-2000 MHz. The disadvantages of this camera is that it does not provide absorption of low-frequency electromagnetic and sound waves.

Sound-absorbing panels are known for wall cladding with increased sound insulation requirements (see USSR Author's Certificate No. 293981, class E04B 1/82. Authors: Osipov GL, Nikolsky VN, Timofeenko LP and E.A. Bieviecki, Research Institute of Building Physics). The disadvantage of these panels is the fact that they do not absorb electromagnetic waves.

The closest technical solution to the proposed (prototype) is an anechoic chamber containing walls forming a closed volume, an electro-tight metal screen that is installed inside a closed volume, and the walls of the electro-tight metal screen are attached, respectively, to the walls forming a closed volume, metal bases, fixed on the walls of an electrically sealed metal screen, a radio absorber made in the form of nickel-zinc ferrite ferrite plates, located wives on introduced metal bases, and a sound absorber made in the form of sound-absorbing panels placed on top of ferrite plates (see RF patent No. 2113040 H01Q 17/00. Authors Martynov AP, Maslov EL, Nikonov SV, Pokusin D.N., Subbotin I.Yu., Titkov A.D., Pryanishnikov V.A. and Fedotova O.L. Ferrat LLP).

The disadvantage of this technical solution is the high cost of ferrite plates, due to the high cost of nickel-containing raw materials.

The aim of the present invention was to provide an effective cheap anechoic chamber, which ensures the exclusion of radiation from the chamber of sound and radio signals, as well as the exclusion of reflection from the chamber walls of sound and radio signals of frequencies from 30 MHz to 1000 MHz. This goal is achieved in that the ferrite plates are made of magnesium-zinc ferrites, the electromagnetic properties of which are close to the properties of nickel-zinc ferrites.

The chamber proposed in the present technical solution comprises walls forming a closed volume, an electro-tight metal screen that is installed inside the closed volume, the walls of the electro-tight metal screen attached to the walls forming a closed volume, metal bases fixed to the walls of the electro-tight metal screen, a radio absorber, made in the form of ferrite plates located on the introduced metal bases, and a sound absorber, made enny as acoustical panels, placed over the ferrite plates. The wall structure of the proposed anechoic chamber is presented in figure 1. To the inner surface of each wall 1 of the anechoic chamber there is attached a corresponding wall of an electrically sealed metal screen 2, on which a metal base 3 is mounted with a sound and radio absorber placed on it in the form of a magnesium-zinc ferrite plate 4, on top of which a sound-absorbing panel 5 is installed. For manufacturing the screen 2 any metal is used, for the manufacture of base 3 light metal is used (for example, duralumin). Panels 5 are made of any sound-absorbing material. Ferrite plates are magnesium-zinc ferrite plates made using standard ceramic technology, containing magnesium, zinc, and iron oxides as a base, and strontium and titanium oxides as additionally introduced, in the following ratio, wt.%:

Magnesium oxide 7.0-13.0 Zinc oxide 11.0-17.0 Strontium oxide 0.3-1.5 Titanium oxide 0.3-1.5 Iron oxide rest

Nickel-zinc ferrites are most widely used as radar absorbing ferrites for anechoic chambers. The disadvantages of the known nickel-zinc ferrites are the insufficient absorption of radio waves in the frequency range from 30 MHz to 1000 MHz and the high cost due to the high cost of nickel-containing raw materials. There is also a method of producing magnesium-zinc ferrites, the electromagnetic properties of which are close to the properties of nickel-zinc ferrites (see Letyuk LM, Zhuravlev GI Chemistry and technology of ferrites. - L .: Chemistry, 1983, p.93) .

The method includes synthesis of a ferrite powder from magnesium, zinc and iron oxides, grinding the synthesized charge to a particle size of 1-3 microns, granulating the mixture with the introduction of a binder, pressing the blanks, sintering and subsequent cooling of the sintered blanks in air. The advantage of magnesium-zinc ferrite is its low cost, due to the low cost of magnesium-containing raw materials. However, the known magnesium-zinc ferrites also do not sufficiently absorb electromagnetic radiation in the frequency range from 30 MHz to 1000 MHz.

Improving the radio-absorbing characteristics is achieved by introducing strontium oxide and titanium oxide into the charge.

The technology for producing ferrite for the developed anechoic chamber includes mixing ferrite-forming oxides of magnesium, zinc and iron, synthesis of ferrite powder from the obtained mixture in furnaces in air by calcining a mixture of the initial oxides in the temperature range 900-980 ° C, grinding the synthesized charge with the introduction of strontium oxide and oxide titanium to a particle size of 1-3 microns, the introduction of polyvinyl alcohol as a binder and granulation of the obtained crushed mixture, the molding of raw billets in the form of plates from granular fairies ritovogo powder pressing and high temperature sintering of preforms in air at 1290-1350 ° C.

The efficiency of absorption of radio waves by ferrite of the proposed composition is due to the fact that the addition of strontium and titanium oxides during heating of the preforms during sintering decomposes to form strontium titanate SrTiO ₃ , which, located at the grain boundaries in sintered ferrites, forms interlayers with high dielectric constant. As a result, a new mechanism for the absorption of radio waves arises due to dielectric losses in the material. In addition, a nonmagnetic thin layer at the grain boundaries contributes to the fixation of the domain walls, which makes it possible to produce resonance of the domain walls during their reversible movement inside the grains and additional absorption of electromagnetic energy.

Figure 1 presents the wall structure of the proposed anechoic chamber. Here: 1 - a chamber wall, 2 - an electro-tight metal screen, 3 - a metal base for ferrite plates, 4 - a ferrite plate, 5 - a soundproofing construction panel.

Example. The comparative effectiveness of the proposed anechoic chamber and prototype was determined. As rooms for anechoic chambers, rooms with dimensions 12000 × 7500 × 4000 mm were used. The floor and ceiling in the rooms were made of standard building reinforced concrete slabs, the walls were made of bricks. The thickness of the walls was one brick. From the inside, each room was qualitatively plastered, the thickness of the plaster layer was 15-20 mm. An electro-tight metal screen was installed inside each room, made of sheets of steel sheet 1.0 mm thick. The connection of the sheets was carried out by electric welding so that the sheet closely adjacent to the plaster. To facilitate the welding process, tin sheets were previously attached to the walls with dowels. Metallic duralumin bases for ferrite plates were installed on top of tin steel sheets. The latter were glued to metal substrates using BF-2 glue. Ferrite plates for both chambers were manufactured using standard ceramic technology; the sizes of ferrite plates were 60 × 60 × 6 mm. For chamber 1 (prototype), the ferrite plates were made of Ni-Zn ferrite with the following component content, wt.%:

Nickel oxide 8.5-10.0 Zinc oxide 21.0-35.0 Cobalt oxide 0.5-1.0 Iron oxide rest

For chamber 2, the ferrite plates were made of Mg-Zn-ferrite with the following component content, wt.%:

Magnesium oxide 7.0-13.0 Zinc oxide 11.0-17.0 Strontium oxide 0.3-1.5 Titanium oxide 0.3-1.5 Iron oxide rest

Ferrite plates glued the walls and ceiling of the chambers. On top of the ferrite plates, standard building soundproofing panels were installed (for example, see USSR Author's Certificate No. 293981, class E04B 1/82. Authors: Osipov GL, Nikolsky VN, Timofeenko LP and E.A. Bievetsky Research Institute of Building Physics). Soundproof panels were installed on the walls and ceiling of the cameras.

The cameras were tested using electromagnetic radiation in the frequency range 30–1000 MHz, and with sound vibrations, in the frequency range 16 Hz – 20,000 Hz. The test results showed that in the indicated frequency ranges there is attenuation of sound signals by –40 dB for cameras of both types, and attenuation of electromagnetic radiation is from –20 dB to –45 dB for a type 1 camera (prototype) and from –20 dB to –– 50 dB for a type 2 camera (proposed camera).

The averaged data on measuring the frequency dependence of the reflection coefficient of radio waves from the surface of the walls of the tested cameras are shown in table 1.

Table 1 No. p / p The composition of ferrite, wt.% The attenuation coefficient of the reflected signal in power, dB Note at field frequency 30 MHz 100 MHz 1000 MHz one Nickel oxide - 9.0 -twenty -45 -25 Prototype Zinc Oxide - 30.0 Cobalt oxide - 0.8 Iron oxide - 60.2 2 Magnesium Oxide - 6.5 -17 -32 -28 Going beyond Zinc Oxide - 17.5 Strontium oxide - 0.2 Titanium Oxide - 0.2 Iron oxide - 75.6 3 Magnesium Oxide - 7.0 -twenty -46 -thirty According to the formula Zinc oxide - 17.0 Strontium oxide - 0.3 Titanium Oxide - 0.3 Iron oxide - 75.4 four Magnesium Oxide - 10.0 -22 -fifty -32 According to the formula Zinc Oxide -14.0 Strontium oxide - 0.9 Titanium Oxide - 0.9 Iron oxide - 74.2 5 Magnesium Oxide - 13.0 -21 -44 -31 According to the formula Zinc Oxide - 11.0 Strontium oxide - 1.5 Titanium oxide - 1.5 Iron Oxide - 73.0 6 Magnesium Oxide - 13.5 -19 -37 -thirty Going beyond Zinc Oxide - 10.5 Strontium oxide - 1.6 Titanium Oxide - 1.6 Iron oxide - 73.8

As can be seen from the table, the manufacture of radar absorbing ferrites according to the proposed composition can significantly reduce the reflection of radio waves from the walls of the anechoic chamber. The deterioration of the parameters beyond the scope of the invention can be explained either by the insufficient thickness of the formed dielectric layer of strontium titanate (when the content of strontium and titanium oxides is less than 0.3 wt.%), Or by a decrease in the resonance of the magnetic domain walls (when the content of strontium and titanium oxides is more than 1, 5 wt.%).

Thus, at a cost less than 1.5-2.0 times (due to the significantly lower cost of manganese-zinc ferrite plates compared to nickel-zinc ferrite plates), the proposed anechoic chamber has better performance compared to the prototype.

Claims (1)

An anechoic chamber containing walls forming a closed volume, an electro-tight metal screen that is installed inside the closed volume, the walls of the electro-tight metal screen attached respectively to the walls forming a closed volume, metal bases fixed to the walls of the electro-tight metal screen, a radio absorber made in the form of ferrite plates located on the introduced metal bases, and a sound absorber made in the form of sound absorbing pa the oil placed over the ferrite plates arranged respectively on the input metallic substrates, each of which is fixed to the corresponding wall elektrogermetichnogo metallic screen, characterized in that the ferrite plates are made of magnesium-zinc ferrite comprising the following components, wt.%:
Magnesium oxide 7.0-13.0 Zinc oxide 11.0-17.0 Strontium oxide 0.3-1.5 Titanium oxide 0.3-1.5 Iron oxide Rest