Horn Antenna's FDTD simulation

FDTD method is a time domain analysis.Here we first we design a wave-guide and there after we just increase its broad side.Our aim is to this simulation is plotting its electric field response with time and how will it response in outside free space.
Here we just take 170 time steps one who can interested in antenna designing they can also plot the radiation pattern of this HORN antenna.Just take the field in the outside the mouth of HORN antenna and there do the simple formula to near filed far field transfer and measure it at your band of antenna.Best of LUCK all of you.