Facet-Based Treatment on Microwave Bistatic Scattering of Three-Dimensional Sea Surface With Electrically Large Ship

Abstract

Abstract-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 threedimensional (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 semideterministic scheme which is established by combining the geometric optics limit of Kirchhoff Approximation (KA-GO) with the Bragg components of Bass-Fuks' 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 facet's 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.

Investigation on Doppler Spectral Characteristics of Electromagnetic Backscattered Echoes From Dynamic Nonlinear Surfaces of Finite-Depth Sea

“…The Doppler spectrum of backscattered echoes provides much more valuable information than the mere radar backscattering cross section, thus the study of the Doppler spectral characteristics from dynamic oceanic surfaces has been receiving great attention for its myriad applications in research areas such as target detection [1][2][3][4][5][6][7], remote sensing in marine environment, etc. [8][9][10].…”

Numerical Approach on Doppler Spectrum Analysis for Moving Targets Above a Time-Evolving Sea Surface

“…When a target is above a three-dimensional (3-D) sea surface at a low altitude, the EM scattering from the sea surface as well as the mutual EM coupling interactions between the sea surface and the moving target has to be considered. This is a typical composite scattering problem which has been widely studied [9,10]. In pervious studies, there are two main types of algorithms based on integral equation method, one applies half space Green function in a specified environment [11,12], the other uses an iterative method which calculates the EM scattering from the target and the sea surface separately, then solves the mutual EM coupling between those two parts using an iterative process [13,14].…”

Comparison of the Two-Scale and Three-Scale Models for Bistatic Electromagnetic Scattering From Ocean Surfaces

“…Here we focus on the bistatic scattering rather than the conventionally considered backscatter, since the evaluation of emissivity calls for bistatic scattering coefficient [18], as well as the growing trend of bistatic applications [19][20][21]. The findings, although by nature are for 2-D scattering from 1-D ocean surface due to computer limitations, can nevertheless be expected to provide valuable insight into the full 3-D surface scattering problem.…”