PRINCIPLES OF DESIGNING INHOMOGENEOUS ELECTROMAGNETIC SCREENS

Abstract

Two classes of inhomogeneous electromagnetic shields are considered: shields based on regular shielding elements and materials with a chaotic arrangement of metal-containing particles. It is shown that an accurate prediction of the protective properties of composite materials with a chaotic arrangement of inclusions is impossible due to the empirical nature of the known Lorentz, MaxwellGarnet, and Odelevsky relations. The development of building and finishing materials with a regular arrangement of protective material in construction products is proposed. The main problem of imparting protective properties to building and finishing materials is the reduction of the main parameters of these materials (elastic modules) due to the addition of a shielding substance. To avoid this effect, it is proposed to use technological cavities in building materials. For this purpose, it is possible to use soot from thermal power plants and iron ore concentrate. Theoretical considerations indicate that the addition of a screening additive of large dispersion to the initial mixture of foam and aerated concrete during foaming promotes the distribution of additive particles on the inner surfaces of the cavities. This significantly increases the protective properties of materials without reducing the elastic modulus of products. A calculation apparatus for the efficiency of shielding electromagnetic radiation by mesh metal structures is presented. To make the structure broadband, it is proposed to use two parallel structures tuned to the maximum and minimum wavelengths of radiation, which are determined experimentally. It is shown that the use of the solution of the wave equation for the Hertz vector allows obtaining simple and convenient relations for determining the minimum frequencies of radiation penetrating through the holes (cutoff frequencies). This made it possible to determine such parameters for rectangular and circular openings. The relations for calculating the effectiveness of protection due to the absorption of electromagnetic energy and the reflection of electromagnetic waves were obtained. The possibility of taking into account the area and number of holes per unit area of the screen is shown. The calculations performed concern purely geometric characteristics of protective structures with holes. A promising area of research is to determine the protective properties of heterogeneous electromagnetic shields, taking into account the electrophysical and magnetic properties of the materials from which the structures are made.