The Optimal Spatially-Smoothed Source Patterns for the Pseudospectral   Time-Domain Method
  Spatially-smoothed sources are often utilized in the pseudospectral time-domain (PSTD) method to suppress the associated aliasing errors to levels as low as possible. In this work, the explicit conditions of the optimal source patterns for these spanning sources are presented based on the fact that the aliasing errors are mainly attributed to the high spatial-frequency parts of the time-stepped source items and subsequently demonstrated to be exactly corresponding to the normalized rows of Pascal's triangle. The outstanding performance of these optimal sources is verified by the practical 1-D, 2-D and 3-D PSTD simulations and compared with that of non-optimal sources. 
Zhili Lin