大型双反射面天线近轴区辐射FDTD-TDPO模拟

针对大型双反射面天线尺寸过大、使用单一的时域方法无法单独模拟其远区辐射特性，以及使用单一的高频近似技术无法给出准确结果的局限，给出了用于大型双反射面天线时域辐射模拟的并行时域有限差分(PFDTD)-并行时域物理光学(PTDPO)混合方法。先创建两个用于并行计算的进程组，一个用于PFDTD计算，另一个用于PTDPO计算; 再根据PFDTD方法计算出双反射面天线馈源的近磁场，同时根据这些磁场使用基尔霍夫表面积分表达式(KSIR)并行计算出次反射面上及其附近的磁场，再使用KSIR并行计算出主反射面上的磁场; 最后使用PTDPO方法计算出双反射面天线的远区辐射场的瞬态响应。同时，还给出主反射面口径为40个波长的Cassegrain双反射面天线的算例，并对馈源相同而口径尺寸不同的双反射面天线进行近轴区的时域辐射模拟。

FDTD-TDPO hybrid method for radiation simulation near axes of large dual reflector antennas

A hybrid method combining parallel finite-difference time-domain (PFDTD) and parallel time-domain physical optics (PTDPO) is presented for computing radiation fields of large dual reflector antennas. The radiation fields can not be simulated by singular time-domain methods and the accurate results couldn’t be got by singular frequency technologies. Two process groups for parallel computing are firstly set up, one is for PFDTD computing and the other is for PTDPO computing. Then the near magnetic fields of the dual reflector’s feed are got by the PFDTD method. Based on these fields, the magnetic fields near or on the sub-reflector are parallel computed with Kirchhoff’s surface integral representation (KSIR). The magnetic fields on the main reflector are also obtained by KSIR. The radiation far-fields of the dual reflector are calculated by the PTDPO method at last. The radiation patterns of the Cassegrain dual reflector antenna, whose main-reflector aperture size is 40 wavelengths, show the results near the axis simulated by the PFDTD-PTDPO hybrid method agree well with those by the PFDTD method. The radiation simulation in time domain near the axes of dual reflector antennas with the same feed and different aperture size is given. The hybrid method has the ability of simulating any large dual reflector with the aperture size of hundreds of wavelengths, even if the reflector’s feed is very big or offset.