PRINCIPLES OF DEVELOPMENT OF ELECTROMAGNETIC SCREENS WITH SMALL DIMENSIONS AND WEIGHT

Abstract

The possibilities of developing thin-film materials for shielding ultra-high and higher frequency electromagnetic radiation are analysed. It is shown that coatings with a thickness less than a quarter of the wavelength of the incident electromagnetic wave (400–500 μm) do not provide low reflection coefficients when applied to a metal surface. The reduction of reflection coefficients to 0.7–0.6 occurs randomly at different frequencies. This is due to resonance phenomena in the coating. The frequency band of minimum reflection is narrow and has no practical significance. It has been shown that it is difficult to achieve an acceptable balance of magnetic and electrophysical properties of a thin coating to minimise reflection coefficients. This is due to the dependence of the final product's performance not only on the magnetic and dielectric properties of the components and their concentrations, but also on the morphology of the particles, their distribution in the matrix body, and the polymerisation mode. In addition, magnetic and electrophysical properties have an amplitude-frequency dependence. It has been proven that in order to ensure low electromagnetic wave reflection coefficients and high electromagnetic energy absorption, it is advisable to use a multilayer structure. The layers must have different magnetic and electrophysical properties. At the same time, the lowest filler concentrations are in the upper layer. These concentrations should be at the limit of the percolation effect – a sharp increase in the electrical conductivity of the composition. These concentrations can be estimated using the theory of electrodynamics of continuous media. If possible, it is advisable to provide a dielectric layer between the layers. The presence of boundaries increases the overall effectiveness of the protective coating.