cavity resonator simulation

I designed a rectangular cavity resonator. I would like to simulate it by using CST. However, I do not now how to feed it? Which source or method would you recommend?
Thank you in advance..

In HFSS, you normally solve cavity resonators with a Eigenmode Solver solution type. In this solution type you do not have to specify wave ports. I am not 100% sure but I believe there is something similar in CST.

use the eigenmode solver.

here a brief tutorial.

Thank you for your help, it looks very useful. Do you know which boundary conditions are used in this document?

background PEC / boundaries electric

I am trying to design a metallic rectangular cavity resonator. Thank you for helping me about eigenmode solver. I learned how to use it.
I created a box made of vacuum, and used conducting walls as boundary conditions. Do you think this corresponds to the design that I have been trying to achieve? If not, what are the results I obtain from this simulation?

you got it.
You set the background as PEC, then you simply design your vacuum rectangular cavity and apply electric boundaries in all directions.
It is by far more efficient (regarding time computation) to build your cavity like this rather than building a real metalic cavity box with the respective thickness.

Great! Thank you for all your help.