针对具有对称结构的计算模型, 本文从理论上分析了采用理想电导体 (Perfect Electric Conductor, PEC)边界和理想磁导体 (Perfect Magnetic Conductor, PMC)边界截断的对称边界条件, 提出了对称截断方法, 利用该方法能够确定截断边界以外场分量值, 以实现截断边界处的 FDTD计算。对具有底板结构的金属柱慢波系统的色散特性进行了分析计算, 得到了与全域 FDTD方法完全一致的数值结果, 验证了对称截断方法的可行性和正确性。对称截断的 FDTD实现, 能充分保证计算精度, 在节约内存占用量和计算时间方面具有明显的优势。

For calculation models with symmetric characteristic, symmetry boundary conditions truncated by Perfect Electric Conductor (PEC) boundary and Perfect Magnetic Conductor (PMC) boundary are systematically analyzed, and a symmetric truncation method is proposed. Therefore the field values beyond truncation boundaries can be obtained so as to achieve the FDTD calculation on truncation boundaries. By analysis and calculation for dispersion characteristic of metallic-pole-planar SWS with floor structures, numerical results exactly consistent with global FDTD are obtained, thus feasibility and correctness of symmetric truncation method are verified. The results demonstrated by numerical simulation of dispersion characteristic of metallic-pole-planar SWS with floor structures are entirely equivalent to the results of global FDTD method. Calculation accuracy could be fully considered by the symmetric truncated FDTD algorithm. Numerical results show obvious advantages in both memory usage and computing time compared with the global FDTD method.