Take a look at the software products sold by Ansoft see:http://ansoft.com/
What you need for an initial analysis is a field solver program. You need to solve Maxwell's equations with boundry conditions that apply to your hardware. This is very difficult to do since Maxwell's equations are four sets of partial differential equations.
The Ansoft product that solves these equations is "Maxwell". See:
It will be expensive, have a steep learning curve but it does do the job. When I was still working an earlier release of "Maxwell" was used in conjunction with a lot of custom software to design aircraft phased array radar antennas.
I wish you a lot of success in your efforts, but it will take a lot of hard work in understanding the problem, even more finding a solution and it will all be very expensive.