稀疏矩阵规范网格结合物理双网格分析介质海面散射特性与试验验证

采用传统数值方法计算介质粗糙海面后向电磁散射时，波束照射面积随擦地角减小急剧增大，需要消耗大量的内存和计算时间。稀疏矩阵规范网格法用快速傅里叶变换计算远区相互作用，极大地提高了计算速度，同时基于物理的双网格法，依据格林函数在介质和自由空间中随作用距离的衰减特性，采用不同分区的网格划分技术，有效减少了介质粗糙面计算所需的内存量。该文基于Monte-Carlo方法产生不同海情PM谱海面，将上述两种方法结合，数值研究了S和Ku波段后向散射特性随擦地角的变化，并与造波池海面后向电磁散射试验进行对比。试验采用连续波扫频方法测量了造波池模拟的中低海情和缩比高海情1维PM谱海面后向散射系数。计算结果与测量数据相吻合，证明了方法具有较高的效率和可行性。结果分析表明，不同海情下海表面相关长度和散射特性存在明显差异。

Backscatter Analysis of Lossy Dielectric Sea Surface Using SMCG- PBTG MethodComparison with Experimental Data

The traditional numerical method of calculating electromagnetic scattering from the dielectric sea surface requires large amounts of memory and computation time as irradiated area increasing rapidly at low grazing angles. The method of Sparse Matrix Canonical Grid (SMCG) computes the product of the Taylor expanded flat surface matrix and the surface current column vector in far field by the Fast Fourier Transform (FFT), which decreases the computation complexity efficiently. According to the properties of the Greens functions of lossy dielectric and free space, the Physics-Based Two-Grid (PBTG) calculates surface field solutions on the both of dense and coarse grids, which reduces the amounts of memory required. Predictions of an exact numerical model using SMCG-PBTG based on Monte Carlo simulation are compared with experimental data. Experimental data is obtained from wave tank experiments in which the backscattering patterns of 1D sea surfaces with PM spectrum at S- and Ku-band are measured. The sea surfaces corresponding to low and moderate windspeed can be directly simulated in wave tank, and the scale model provides an alternative approach for measuring scattering from sea surfaces corresponding to high windspeed. A comparison of the absolute value of the backscattering coefficient shows the theory and experiment to be in good agreement. Results show that the correlation lengths and scattering behaviors are significantly different under the different windspeed.