Cavity size: length: 4.3cm, width: 3.9cm, height: 2cm. The cavity is filled with air and a layer of substrate. The thickness of the substrate is 0.5mm and its relative permittivity is 2.2. HFSS 8.5 uses 11602 tetrahedrons for the simulation.
Compared with the same cavity without substrate, the resonant frequency decreases a little. The modal field is very similar. One interesting observation is TE111 and TM111 modes have different frequencies due to the disturbance caused by the substrate, so that HFSS obtains separate TE111 and TM111 mode.
by Yaxun Liu, 2003