| In this thesis,some discontinuities of waveguide structure are analyzed. Based on mode matching method and microwave filter design theory, several band-pass filters with different discontinuity structures are designed.First of all, a series of key blocks are analyzed by mode matching method. The general expressions of the coupling matrix and scattering matrix are given by analyzing the discontinuity unit of a coaxial and symmetrical circular waveguide step. For certain discontinuities in unsymmetrical circular waveguide step, rectangular-to-circular waveguide junctions, coupling matrix and scattering matrix can be directly obtained provided the eigenfunction and power normalization coefficient are given. Among these, the analysis of rectangular-to-circular waveguide junction discontinuity is the most complicated due to the inhomogeneous coordinate is adopted. The coordinate must be converted to the convenient one in terms of the junction structure.By combining microwave filter theory with numerical optimization method, several band-pass filters are designed. The results of MMM agree well with that of HFSS. |
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