A New finite transmission zero generation technique in evanescent mode waveguide combline filters

Elif, İnan
With the recent development of the RF and microwave technology, sizes of the microwave filters become more of an issue. In this thesis, evanescent mode waveguide combline bandpass filters operating at 16.6D17 GHz frequency band suitable for miniaturized RF & microwave modules have been developed. In order to accomplish compact filter sizes, evanescent mode waveguide (EWG) and combline filter designs are incorporated. By using a filter design software Filpro and 3DD electromagnetic (EM) simulation software (CST) a 4Dresonator EWG combline bandpass filter is designed. The size of the aforementioned filter design is then further decreased by incorporating Finite Transmission Zero(s) (FTZ). The method to realize the FTZ(s) in the EM simulator is a novel technique where dielectric material is placed in between two adjacent resonator rods creating a series capacitive reactance. This capacitance appears to be in parallel with the inherent series inductive reactance of the waveguide piece between adjacent rods, thus forming a parallel LC resonator in series arm, stopping signal flow at its resonance frequency, thus forming a FTZ. The tuning of the FTZ(s) is achieved by adjusting the height of the corresponding dielectric material. The FTZ(s) can be placed on either sides of the passband, improving the selectivity of the filter while also reducing the length of the filter appreciably. Approximately 15% and 27% size reduction is observed after inserting one FTZ and two FTZs, respectively.


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Citation Formats
İ. Elif, “A New finite transmission zero generation technique in evanescent mode waveguide combline filters,” M.S. - Master of Science, Middle East Technical University, 2014.