Anchal Singh
Ansys Employee

Hello Miguel,

You can create an open region for this case. It will automatically make the radiation box for your design. You can do so by right mouse clicking on the design name in the project manager and choosing 'Auto Open Region' under the solution type dialogue box.

To learn more about boundaries in HFSS, you can go through the HFSS Help document - Assigning Radiation Boundaries

Hope this helps!