FACET-BASED TREATMENT ON MICROWAVE BISTATIC SCATTERING OF THREE-DIMENSIONAL SEA SURFACE WITH ELECTRICALLY LARGE SHIP

A feasible simulator, of which formulation and mechanism should be simple and time saving, is developed in this paper to overcome the difficulties of prediction on the EM scattering from three-dimensional (3-D) electrically very large ship-sea models. The work in this paper is twofold. First, the sea surfaces are supposed to be a combination of many locally-tilted slightly rough facets with two-scale profiles. The radar return from each local facet is associated to a semi-deterministic scheme which is established by combining the geometric optics limit of Kirchhoff Approximation (KA-GO) with the Bragg components of Bass-Fuksʹ two-scale model (BFTSM). Furthermore, we associate the complex reflective function of the respective facet by a so-called Phase-modified Facet Model (PMFM), in which the facetʹs phase is treated approximately as a combination of inherent part that follows a homogeneous random distribution and coherent part associated with the relative path-delay. Second, in companion with the semi-deterministic treatment of the sea scattering model, a hybrid approximate algorithm is proposed to deal with the composite scattering of electrically large ship-sea model, which is entirely evolved through facets (for the sea surface) and wedges (for the ship target). The method of equivalent currents (MEC) and a hybrid frame which combines the four path model (FPM) with the quasi-image method (QIM) are employed to calculate the scattering characteristics of the ship-like target and ship-sea interactions, respectively. The entire simulator is of comparatively significant computational efficiency, and suitable for providing a preliminary prediction on the instantaneous complex reflective functions and normalized radar cross sections (NRCS) mean levels for electrically very large ship-sea model.