Thanks for your reply.
I would say that you could benefit greatly from a high frequency EM analysis software, but which tool is right for you will depend on the type of antennas you want to simulate.
If you are designing patch antennas or other planar antennas, I think it is most efficient for you to consider a planar EM simulator. Many exist, just look up 2.5D or 3D Planar EM software on Google or similar (or look through the many posts on this forum).
If you have a more 3D antenna, like a helix or a waveguide antenna, then you should look at the full 3D EM software tools. For antenna problems, many people prefer the time domain 3D analysis techniques because they offer natural broadband simulation performance, and are often more efficient in computer resources required for accurate analysis (though this is not necessarily strictly true).
Finally, if you have an antenna that uses wire elements (or long, thin metal rods), I think you will find the NEC type codes (wire scattering Moment Method codes) to be most efficient for handling this type of problem.
Like I said, the best answer for you depends on your antenna application. I don't think one software tool can come close to handling all antenna design and analysis problems.
--Max