说明：  这是一个用FDTD计算远场的c程序，该程序的核心是用近场值外推远场值。大大节省了计算机内存和计算时间。可谓经典。
(This is a far-field using FDTD calculation of the c process, which is the core value of using near-field far-field extrapolation value. Significant savings of computer memory and computing time. Can be described as classic.)