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An evanescent-mode waveguide filter consisting of two parallel cutoff waveguide paths with dielectrics is modeled in FEKO and compared with results from the open literature.
The authors of  describe an evanescent-mode waveguide filter consisting of two parallel cut-off waveguide paths with dielectrics. The proposed filter is modeled in FEKO with the FEM enclosed regions technique that allows the filter to be modeled with only tetrahedra and a FEM solution. The metallic waveguide forms the boundary condition for the FEM region, so no MoM boundary solution is required.
Figure 1 shows a lateral cut-plane view of the model with dielectric regions in green and free-space (air) regions in orange. All outside surfaces are metallic, except for the ports which are dielectric boundary surfaces. The ports are modeled with FEKO’s FEM modal port which automatically computes the fundamental mode that propagates into the filter.
As this filter is designed for a very wide band of frequencies, FEKO’s AFS technology is applied to effectively select the minimum number of frequency points that will accurately characterise the filter’s response.
Figure 2 presents a comparison between the filter’s measured insertion loss (from ) and the FEKO computed insertion loss. The comparison is excellent, validating the applicability of FEKO to problems including waveguides and dielectric elements.
Fig 2: Insertion loss comparison – Measured vs FEKO
|||H. Shigesawa, M. Tsuji, T. Nkao, K. Takiyama, “Two-Path Cutoff Waveguide Dielectric Resonator Filters,” IEEE Transactions on Microwave Theory and Techniques, Vol. 37, No. 7, July 1989, pp. 1105 – 1112|