Equation parabolique hybridée à l'optique physique pour le calcul de la propagation et de la diffusion dans un environnement maritime

Abstract : The aim of this thesis is to estimate the field scattered by a rough sea surface in the presence of a duct. The surface is illuminated by a coastal radar under low grazing incidence. The case of a bistatic configuration, for which both transmitter and receiver are located in the duct, is particularly studied. For such a configuration, an evaporation duct, characterised by the vertical variations of the refraction index profile in the vicinity of the sea surface, can strongly affect the radar system performances. Thus, this is a problem of propagation and scattering under low grazing incidences. This thesis aims to develope an approximate methode (asymptotic) to jointly solve the scattering caused by the sea surface and the propagation within the duct. The studied method is based on the physical optics (PO) approximation. It allows us to calculate the coherent and the incoherent components of the currents on a rough surface and the field scattered inside the duct. For the coherent component, a classical model introduced by Ament is hence extended to multiple rebounds from the surface and for a duct with a linear-square refraction index profile. In addition, the results are compared with a rigorous method based on Method of Moments. Finally, the effective impedance, derived from the Small Perturbation Method, is introduced in order to correct the PO-based model for the vertical polarisation.
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Dusan Cvetkovic. Equation parabolique hybridée à l'optique physique pour le calcul de la propagation et de la diffusion dans un environnement maritime. Electromagnétisme. UNIVERSITE DE NANTES, 2016. Français. ⟨tel-01298028⟩

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