fdtd gaussian pulse

how to select t0 and spread for Gaussian pulse when calculating fields using Fdtd for an antenna..............

In FDTD You shoul use a modulated gaussian impulse. the frequency of the RF sinusoidal tone should be the center frequency of the analisis band, and the duration af the pulse is 0.9/deltaf, where deltaf is the width of the band.
of corse t0 have to be less than 0.5/deltaf