Simulation of rectangular EPR cavity in X Band

We have to make an X band EPR rectangular cavity with waveguide and iris screw on COMSOL. Testing has to be done on the x band. We have to explore the effects of different coupling configurations. We are required to find eigen frequency and simulate a frequency domain model. The wave guide needs to defined with a port and then simulating over a range of frequencies. Below attached is a paper that is similar to my project and explains how part of it works. Please read from page 38 onwards to get an idea. The paper also shows cylindrical cavity but we do not need that.