Analysis Of Waveguide Discontinuities Using Mode Matching Method And Applications In Microwave Filter

In this thesis, some discontinuities of waveguide structure are analyzed. Based on mode matching method, combined with microwave filter design theory, several low-pass, band-pass filters with different discontinuity structure, and a k band diplexer is designed.First of all, the generalized s-parameter matrix (GSM) of discontinuities unit including waveguide transverse irises, waveguide tee junctions, e-plane metal inserts, waveguide-bend, and ridged waveguide are calculated by the mode matching method (MMM). With the traditional MMM, the GSM of transverse irises, such as resonant iris, inductive iris and capacitive iris are determined by matching the tangential electric field and magnetic field. With the tangential magnetic field matching is replaced by the Conservation of Complex Power matching, single or more E-plane metal inserts is analyzed. The key problem in ridged waveguide that is the determination of cutoff wave number of TE and TM wave is solved by the transverse resonance method, and then the discontinuities between the ridged and rectangular waveguide can be calculated. For the waveguide bend, the Helmholtz equation is transformed to the eigenvalue problem. And then by matching the input rectangular waveguide to the waveguide bend and the waveguide bend to the output rectangular waveguide, the GSM is determined.Combined with microwave filter design theory and numerical optimization method, several low-pass, band-pass filters, and a k band diplexer are designed. The results of MMM agree well with that of HFSS or experiment.