IPO结合FMM，RPFMM，FaFFA方法快速计算电大腔体的RCS

迭代物理光学法结合快速多极子(IPO+FMM)方法，可以快速计算电大腔体的电磁散射特性。传统的快速多极子(FMM)方法需要计算两组的转移因子以及转移过程的全部角谱分量，计算开销是非常大的。随着组间距离的增大，转移过程可以用射线多极子(RPFMM)简化计算，为了充分利用射线多极子方法中参与计算的有效角谱分量随着组间距离增大而变少的特性，采用一种随着组间距离增大自适应调整参与计算的角谱分量的锥形区域的射线多极子方法(RPFMM)，当两组距离足够大而位于远场时，用远场近似方法(FaFFA)进一步简化计算。结果表明该方法能在保持计算精度的同时并能较IPO+FMM方法进一步减少计算资源占用、提高计算速度。

The Fast Calculation of RCS of Electrically Large Open-Ended Cavities Combine IPO, FMM, RPFMM, FaFFA

IPO+FMM method can rapidly solve the scattering of three-dimensional cavity. In the conventional Fast Multipole Method (FMM), at all directions of translation between two groups should be computed, it is expensive. The Ray-Propagation Fast Multipole Method (RPFMM) is applied to simplify the translation when two groups are well separated. In fact, the amount of translators to be calculated should be decrease with the increase of distance between two groups, to take full advantage of the characteristics; a self-adaptive ray-propagation fast multipole algorithm which can modulate the bound of cone zone of RPFMM is adopted. When the distance between two groups is enough large, Fast Far-Field Approximation (FaFFA) is used to further simplify the translation. The numerical results show this method is accurate enough and can improve efficient computing speed than IPO+FMM.