The regularities of the influence of the moisture content of expanded clay on the values of the reflection coefficient of electromagnetic radiation (EMR) of this material in the frequency range of 1–17 GHz have been established. The relationship between the size of fractions (pore size) of expanded clay and the operating frequency range of the EMR screen samples has been determined. It is shown that a twofold increase in the moisture content of expanded clay with fractions of 1…4 and 10…20 mm provides an extension of the operating frequency range of the EMR shield samples made on the basis of this material, with a decrease in the reflection coefficient of the test samples by 1.7 and 3 times, respectively. It was found that an increase in the moisture content of expanded clay from 19 to 40 % with a decrease in the size of its fractions from 10…20 to 1…4 mm and a pore size from 0.1…0.2 to 0.01…0.06 mm provides a decrease in the values of the reflection coefficient of EMR screen samples at frequencies of 7.7–17.0 GHz, and an increase in the size of expanded clay fractions from 1…4 to 10…20 mm with an increase in the size of its pores from 0.01…0.06 to 0.1…0.2 mm provides a decrease in the values of the reflection coefficient of EMR screen samples at frequencies of 1.0–7.7 GHz. It is shown that the practical use of these regularities makes it possible to form EMR screen samples with reflection coefficients from –2.8 to –22.0 dB in the frequency range 1–17 GHz, which makes it possible to recommend them for use when creating shielded rooms.
The results of the study of the values of the reflection coefficients and the effective scattering surface of the developed design of the electromagnetic radiation screen in the frequency range of 2…12 GHz are considered. The structure consists of a layer of moisture-containing pseudo-oval scattering elements with linear dimensions of 1…4, 1…2 and 10…20 mm, which is placed between two layers of polyurethane sealing mastic. The use of pseudo-oval elements with linear dimensions of 1…4 mm containing solutions made on the basis of a 20 % solution in the developed electromagnetic radiation screen design allows reducing the values of the reflection coefficients of electromagnetic radiation at frequencies 4.2…6.5 and 1.0…4.1, 8.0…12.0 GHz. The formation of a screen design based on elements with linear dimensions of 1…2 and 10…20 mm, impregnated with a 20 % sodium chloride solution, leads to a decrease in the values of reflection coefficients in the frequency range of 2…12 GHz. It is established that the values of the effective scattering surface of ground objects in case of placing or fixing of the specified design variant of the electromagnetic radiation screen on their surface are 0.6…24.0 m2 in the frequency range of 2…12 GHz. This makes it significantly difficult to obtain reliable information about the location and characteristics of ground objects in the frequency range under consideration.
Process research results of creating polymer charcoal-containing electromagnetic radiation absorbers by adding powdered coal (coconut activated, wood activated and non-activated) to the composition of polyurethane mastic for reducing the reflection coefficient of electromagnetic radiation in order to ensure the electromagnetic compatibility of radioelectronic devices are presented in the article. A technique for creating charcoal-containing electromagnetic radiation absorbers has been developed, according to which single-layer, two-layer and three-layer carbon-containing electromagnetic radiation absorbers samples have been obtained. The structure of coal particles and the mechanism of their distribution in polyurethane mastic have been studied. Based on the analysis of reflection and transmission coefficients frequency characteristics in the frequency range 3–17 GHz, the optimal layers position and their composition was determined to obtain the optimal shielding level for radioelectronic devices from electromagnetic interference and ensuring electromagnetic compatibility.
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