二维半空间时域有限差分瞬态场外推方法

Extrapolation to the transient field for FDTD in two-dimensional half-space

An algorithm for extrapolating the transient field in two-dimensional half-space for the finite-difference time-domain(FDTD) method is firstly presented. In this algorithm, the far-zone scattered field consists of three parts. The first two parts of the field are generated by the equivalent electromagnetic currents at the extrapolation bound in upper space, propagating along the paths of directed and reflected waves, respectively. And the third part is resulted by that currents at that bound in lower space, its propagation following the path of the transmitted wave. To caculate the latter two parts, the reflection and transmission points should be determined with the knowledge of Snell's law and then projected on to the observation time bins, moreover the proper time of the wave propagating from the equivalent source to those points should also be worked out and used to delay those bins, with the reflection or transmission coefficients used as the contribution factor to the far field. Then the proposed algorithm is validated by the applying far-zone scattered fields to two examples.