Effect of Relative Dielectric Permittivity in Quasi-Planar Filters

A comparison between all metal inserts E-plane filters and finline filters with different substrates is presented. The comparison is focused in the upper out of band rejection achieved by the filters and in the sensitivity of central frequency with respect to the waveguide width. Full-wave simulations and measurements show that finline filters with higher relative permittivity can improve both characteristics. An E-plane filter with all-metal inserts and two finline filters designed from the same pass band prototype at Ka-band are constructed and measured in order to validate the theoretical results.