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

Abstract

Abstract-In order to analyze the Doppler spectrum of threedimensional (3-D) moving targets above a time-evolving sea surface, a hybrid method with acceleration techniques is proposed to simulate the electromagnetic (EM) scattering from the composite moving model. This hybrid iterative method combines Kirchhoff approximation (KA) and the multilevel fast multipole algorithm (MLFMA) to solve the EM backscattering from the rough sea surface and the targets, respectively, then mutual EM coupling effects between them are taken into account through an iterative process. To overcome the vast computational cost in the iterative process, acceleration approaches which can greatly reduce the calculation time are applied. Coupling area on the sea surface is truncated according to geometrical optic principle. Then a fast far-field approximation (FAFFA) is applied to speed up the mutual interactions between the targets and the sea surface. A successive iteration method is proposed to reduce the convergence steps for the MLFMA process. The accuracy and efficiency of this hybrid method with accelerations are demonstrated. Doppler spectra of backscattering signals obtained from such numerical EM simulations are compared for different incident angles, target velocities and surface models. The broadening effects of the Doppler spectra due to the mutual EM coupling interactions are studied.

Scattering and Doppler Spectral Analysis for a Fast-Moving Target above Time-Varying Lossy Dielectric Sea Surface

“…Considering the specular reflection properties, Qi et al [7] and Zhang and Sheng [20] presented their own coupling areas according to geometrical optical principle. We follow the coupling area proposed by Zhang and Sheng.…”

“…Recently, Guo et al [6] proposed the EPILE method to analyze scattering from targets above or below rough surfaces. Qi et al [7] employed a hybrid iterative method that combined KA and MLFMA to solve the EM backscattering from rough sea surface and targets. Liu and Jin [8] developed the FEM with domain decomposition to study the Doppler spectrum of a flying target above dynamic oceanic surfaces.…”

An efficient raw data simulation algorithm for large complex marine targets and extended sea clutter in spotlight SAR

“…To calculate a backscattering field, a specific integral equation has to be solved. Recently, the numerical solutions are more considered for this purpose . By this manner, the computation depends on the size of desired scene and the target dimensions.…”

“…Recently, the numerical solutions are more considered for this purpose. 8,9 By this manner, the computation depends on the size of desired scene and the target dimensions. Unfortunately, most of these methods are limited to 2D models due to the high amount of calculations required for the 3D cases.…”

Backscattering From Electrically Large Target Above Nonlinear Sea Surface

“…Since FEM and BIM are only performed on the target and the dominant region of the sea, the number of unknowns is dramatically reduced [15]. A fast far-field approximation (FAFFA) is also applied to speed up the mutual interactions between the targets and the sea surface, and improved iteration method is proposed to reduce the convergence steps for the MLFMA process [16].…”