Coaxial Waveguide

Is there anyone who had designed a coaxial waveguide using CST and extracted the cutoff frequencies?
I would like to test an absorbing material using coaxial waveguide measurements but at firs i want to simulate the model of coaxial waveguide and test the MUT(material under test) inside it, but i get some errors in the feeding port and consequently i don't get the correct results.