Help: Lumped Port in Metal Shielded Box?

Hi everyone,
I have a question of Lumped Port in HFSS. For example, the microstrip line in enclosed in a metal shielding box. The out boundary conditions of the air box is PEC, rather than radiation. How can I set a lumped port for the line?

- I drew a rectangle from the line end to the ground, and set it as lumped port. However, since this port rectangle overlaps with the metal box while the line, ground and metal are all PEC, the simulation is wrong. The error is that "Too few conductors were found."
- Although the waveport is available, I want to simulate this shielding box using lumped port in Driven Terminal. Do anyone know how I can avoid this problem and set right for the lumped port?

Waiting for your help! Thank You!

I guess the simplest solution would be to either make the box slightly larger so it does not short the port. Or, make the line slightly shorter so that it doesn't reach out to the PEC side wall. You will have to try out how far away the port needs to be from the PEC box in order not to have the results affected by it.

Try putting an additional surface of rectangle at the port and draw ur excitation over that surface, as generally used for waveport. if it still gives the problem, why not subtract a section of ur box at the input port and give ur excitation so that the port will not touch the box