which one first? Drawing layout or simulation with ADS or CST ....?

Hi
I'm going to simulate and verify a design.at first glance it seems that first step should be simulating with ADS and then drawing layout using Protel.
But I'm wondering that opposite procedure wouldn't be better.?
I mean if first draw layer then simulate and optimum with ads then all effect will be considered.
I mean in practical point of view.
Any comments and suggestions are welcomed

- If you are familiar with required dimensions and good RF layout practice, you can draw first and then EM simulate.
- If you are unsure about dimensions, the first step could be build the RF layout step by step with model-based transmission line elements.
- In any case, a final EM simulation makes sense to include couplings and other real world effects.

Actually i'm familiar with RF concepts but not so much with PCB layout design.

Ok, but I don't get your question. If you know how to do a good layout, draw it then finally analyze to confirm that it works. Problem: if it fails, you need to understand where in that big layout it goes wrong.
If you are not so familiar with layout, go step by step and analyze each small building blocks early, before you put it all together. Then you can locate problems more easily, before you put things together.

Actually as i said I'm not familiar with PCB design. I'm concern about PCB elements like Via's, PAD's and parts that are related to lumped elements and their effects on overall response of design.

Then clearly start at ADS circuit simulation level (model based simulation of layout pieces with MLIN etc.) and build things step by step.

Ok, Thanks for Advises