Menger sponge EM simulation

Hi all, i am doing a project about EM simulation for dielectric fractal Menger Sponge Stage 2. I am using CST MWS as simulator. The objective is to send the incident plane wave torward the structure and find out the resonance frequency for which the EM fields are localised in the structure. I tried plane wave and wave ports method. But it is strange that i can't get the similar results as obtained in the papers in which the previous studies about Menger Sponge are mentioned. Anyone can help me please? Thank you.