I am designing an RF Power Amplifier with Cree CGH40010F 10W model. The design is pretty complex involving two transistors and a complicated output matching and combining network. I have obtained satisfactory results in MLIN design. The problem arises when I am running an EM cosimulation involving the EM model and passive components etc. making layout look alike models. The response here is nowhere near what should be! I have parameterized my layout, thus trying to optimize it with the EM model, but one optimization iteration takes immense time. Even to the extent of it, I ran the optimization for 25 hours but with 5 iterations only, and surprisingly, no improvement in the results! Please suggest me how to proceed with the EM optimization of such a complex design and finally arrive at a working prototype. Thanks in advance.