二维分形海面电磁后向散射系数的分析与计算

根据改进的二维分形海面模型推导了一种在不同极化方式下(HH水平极化,VV垂直极化)新的电磁后向散射系数计算方法,对多个海浪波长区域内所有分辨单元后向散射系数进行平均统计.在时域内研究了海水介电常数、电磁波入射角、入射频率以及风速风向对后向散射系数的影响,运用盒维数方法计算了该散射系数的分形维数.最后通过数值分析方法证明了该散射系数实部与虚部曲线是分形的,并且与二维分形海面的分形维数相等,从而表明该海面的雷达回波信号也具有分形特性,为运用分形理论研究海面微弱目标检测提供了一个重要方法.

Analysis and computation on electromagnetic backscattering scattering coefficient of two-dimensional fractal sea surface

Based on the existing two-dimensional fractal sea surface model, a novel electromagnetic backscattering coefficient model was derived in the HH and VV polarization mode, respectively. Average statistics of the backscatter coefficient from all resolution cells in some wavelength regions was computed and affect of seawater permittivity, electromagnetic waves incident angle, incident frequency, and wind speed and direction on the backscattering coefficient was analyzed in the time domain. The fractal dimension of the backscatter coefficient was estimated by box-counting. Numerical analysis method was adopted to demonstrate that the real and imaginary parts of the backscattering coefficient are fractal and their fractal dimensions are both equal to the fractal dimension of the backscattering coefficient or the two-dimensional fractal sea surface. Thus it indicates that the radar echo from the sea surface is also fractal, and provides an important method for the use of the fractal theory in sea weak target detection.