复杂海面电磁散射的修正面元模型

A Modified Facet-Model of Electromagnetic Scattering from Complex Ocean Surface

针对合成孔径雷达成像系统中,利用传统面元模型在含泡沫的复杂海面环境下得到的面元后向散射场误差较大,导致成像模糊的问题,提出了一种复杂海面电磁散射的修正面元(MFM)模型。首先建立精确的海水介电模型来计算含泡沫海面介电常数;然后基于Elfouhaily海谱模型生成具体的海面样本,并将其划分成一个个小面元;最后计算出各面元的散射场,将其叠加得到海面样本的散射结果。与实测数据的对比表明,传统面元模型在大入射角时的仿真结果出现衰减现象,而加入泡沫的修正面元模型将使衰减降低近10dB,增强了与实测数据的吻合度。采用MFM模型对海面电磁散射特性及布儒斯特效应进行实验,结果表明:风速对海面布儒斯特效应影响较大,在P波段当风速由4m/s增大至10m/s时,布儒斯特效应减弱85%左右。

A modified facet model is presented to solve the problem that the classical facet model in the synthetic aperture radar has large error of backscattered field from facets and results in blurring imaging in complex ocean surface.Firstly,an accurate model is built to calculate the permittivity of sea water with foams.Then,a concrete ocean surface is built based on the spectral model of Elfouhaily,and is divided into many little facets.The scattered field for each facet is calculated,and the result of electromagnetic scattering from ocean surface is obtained by superposing these scattered fields.A comparison with the measured data shows that when incidence angles are large,simulation results of the classical facet model appear an attenuation,while the modified facet model with foams reduces the attenuation about 10 dB and enhances the coincidence degree with the measured data.Experiment results by using the modified facet model to analyze the ocean surface electromagnetic scattering properties and Brewster effect show that the wind speeds influence the Brewster effect obviously.When the wind speeds at P-band increase from 4 m/s to 10 m/s,the Brewster effect is weakened about 85%.