Optimizing RF PA EM Model

Hello everyone,

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.

Hi deepayanb,

Unfortunately the question you are asking is quite broad, and therefore I will just answer with my own suggestions, hopefully those help you to some extent.

- After your whole design works with ideal components it is good practice to substitute them by models that include harmonic response. This is usually an intermediate step and, even though is not mandatory, it can point out to some of the troubles in your design. Usually these models are provided via design kits by foundries.

- Regarding your EM simulation problem, take it step by step. That is, generate a layout model + an EM simulation of each of your circuit parts (e.g. combiner, output matching network, input matching network) and replace them one by one in the place of the ideal components. Each time you replace a part by its EM model (and left the rest with your ideal model), check that the response of your circuit is within your desired requirements.

- Finally I would advice you to fix the undesired effects in each step by tunning the layouts, rather than using optimization procedure. Optimizations are quite powerful, but they usually involve a lot of things to consider.

Good luck!

Thank you very much. I will definitely try it.

Suggest contacting your local Technical Support center. They will be able to help you troubleshoot the problem, either using WebEx of obtaining your workspace.

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