The dual mode filter was developed, measured, and simulated by ESA (European Space Agency). It shows a narrow transmission band around 11 GHz. The reflection in this band is below 20 db. CST was the only company who was able to predict the correct behaviour. Below 20 db an agreement is nearly impossible as the structure is highly sensitive to the smallest changes (see measurement and simulation by ESA itself). FE-codes were not able to predict any realistic result.
Figure 1: Dual mode filter
Figure 2: Simulated (dotted line) and measured results (continuous line) by ESA
Figure 3: Simul. Results by CST (continuous line) and KCC (dotted line)
Figure 4: Simul. Results by FE Codes