改进的二维分形模型在海面电磁散射中的应用

The application of an improved 2D fractal model for electromagnetic scattering from the sea surface

提出了一种改进的二维分形海面模型,其表面谱函数在空间波数小于基波波数及大于基波波数时分别满足正幂率关系和负幂率关系.通过比较可以发现在不同风速时,改进模型的空间自相关函数及表面轮廓谱和有关文献结果有较好的吻合.在满足Kirchhoff近似条件下推导了改进分形模型的散射系数及散射强度系数的计算公式并进行了数值计算,比较了改进模型和经典模型的后向散射强度系数角分布并详细讨论了它们随入射频率、海上风速和风向的变化.

In this paper, an improved 2D fractal model is present for modeling the sea surface, the fractal spectrum of which satisfies the positive or negative power law for spatial wave numbers smaller or larger than the fundamental wave number, respectively. The spatial correlation function and the spectrum of this improved model show good agreements with those given in the literature for different windspeed. Based on the Kirchhoff approximation, the scattering coefficient and the scattering intensity coefficient of this new model are derived and evaluated. The angular distributions of backscattering intensity coefficient of the improved fractal sea model are compared with those of the conventional model, the influence of the incident frequency, windspeed and winddirection on the backscattering intensity coefficient is also discussed in detail.