Just a reminder: Unless you change the boundary conditions of your simulation space Top or Bottom cover, the entire outside of this box will be treated by Sonnet as a PEC boundary. It's convenient if you need to model metal for top and/or bottom ground planes. But if this is not the case in your real model, then you should add layers of air on the top and bottom of your model. That is true even if you change the Top and/or Bottom of your Sonnet simulation box to be Free Space boundaries. You don't want these Free Space boundaries to get too close to your circuit.