CHARACTERISTICS OF SEA SURFACE SCATTERING ELEMENTS UPON RADIO WAVES PROPAGATION AT SMALL GRAZING ANGLES

Subject and purpose. The article is devoted to the simulation of the backscattering of the electromagnetic field on the sea surface in respect to the millimeter and centimeter ranges of radio wavelengths. The relevance of such studies is determined by the need to model the characteristics of sea-based radio systems at the design stage. The aim of the work was to determine the characteristics of the illuminated elements of the underlying surface in relation to the backscattering of radio waves at small grazing angles.

Methods and methodology. To achieve this goal, the methods of mathematical and statistical modeling were used. The simulation results were compared with experimental data.

Results. Comparison of the lifetimes of the sea surface scattering elements and the speeds of their movement with the durations of the scattered radio signal bursts and Doppler frequency shifts of the radio signal upon movement of the electromagnetic field diffusers showed the consistency of the results obtained from the simulation with experimental data. The characteristics of the scattering elements of the sea surface are obtained in respect to the backscattering of radio waves at small grazing angles. They include the probabilities of the illumination of the scattering elements of the surface, their average radii of curvature, as well as the local angles of incidence of the radio wave on the illuminated surface elements.

Conclusion. It is shown that with the grazing propagation of radio waves significant surface shading occurs. This leads to the fact that the electromagnetic field is scattered almost only on the tops of the highest sea waves. In this case, the local angles of incidence of the electromagnetic field on the scattering element of the surface approach 90°. At such local angles of incidence, the illuminated surface element has a very low reflectivity in the opposite direction.