DOPPLER SPECTRUM MATHEMATICAL MODEL OF SIGNAL SCATTERING FROM SEA SURFACE AT LOW GRAZING ANGLES

Abstract

Introduction. Doppler spectra of signals which are scattered from sea surface and received by radar is used in oceanology and ecological monitoring applications. Existing models of Doppler spectra have the limitation of application because they are based on empirical data in changing conditions. Variability of the observation conditions critically influence on microwaves scattering by sea surface at low grazing angles which is typical for marine radiolocations. Objective. The goal of investigation proposed in this article is to develop the mathematical model of Doppler spectra at low grazing angles for microwave frequency range. Materials and methods. The two-dimensional problem of the scattering of an electromagnetic field on a cylindrical deterministic surface is considered. For generating of sea surface realizations is used linear model with spatial sea spectrum Elfohaily. The solution of the scattering problem is obtained for the case of vertical polarization of the incident electromagnetic field by the method of an integral equation with the control of the error of the solution. The mathematical modeling of the Doppler Spectrum of signal scattered by sea surface is produced by method of statistical trial. The case where the direction of the observation of the sea surface by radar is perpendicular to the direction of the wind is considered. The electromagnetic filed scattered in the direction of the radar receiver as a function of time is calculated for each generated sea surface realizations. Further, the set of variables of the implementation of scattered field is calculated for implementation of the Doppler spectrum. Results. The set of implementations of the Doppler spectrum provided its mathematical model with consist of deterministic and random component. The approximation of each aforesaid component is suggested and mathematical expressions for value component calculation are presented. The analyze of modeling result is produced. Conclusion. The developed mathematical model is offered to use for the design of algorithm sea surface condition estimation and pollutant detection using the signal which received by radar.

Keywords

• radiolocation
• doppler spectrum of signal
• modeling
• radio wave scattering
• sea surface
• grazing angle of illumination