I have developed FDTD programming to simulate E and H field, but I don't know how to simulate radiation pattern, anyone have programming based on FDTD technique to produce radiation pattern for patch antenna?
Well, conceptly it can be done by near field and far field transformation.
You can see the materials form any classic FDTD books. As for E plane and H plane, you only need to define an angle of radiation pattern you want to caculate such as fai=0 and fai=90