Modélisation cohérente de la diffusion électromagnétique par des surfaces de mer tridimensionnelles en incidence rasante. : Application aux radars HF à ondes de surface.

摘要

This thesis deals with the analysis of the electromagnetic interactions between surface waves at HF frequencies, and a time-evolving sea surface. A simulator comprising three specific elements has been developed.The first one enables the user to model a time-varying sea surface in three dimensions, by the application of the linear wave theory. The second one simulates the interaction between the electromagnetic wave at grazing incidence and the sea surface using an exact model based on the method of moments. Lastly, a post-processing tool allows the plotting and the analysis of the resulting Doppler spectra. Validation tests are presented. Various simulations on static and dynamic surfaces (sinusoids and sea surfaces) reveal the Bragg resonance phenomenon and the Doppler effect respectively. The influence of the sea surface and the radar configuration is investigated. The simulation results show a good fit with published data and ONERA measurements. Finally, a film of pollutant on the surface is introduced in the model by the addition of a surface pressure (corresponding here to an attenuation of the heights of the waves). The effect of the presence of the film on the Doppler spectra is analyzed.