Spectral approach to the synthesis of bandstop filters

A nontraditional approach to the synthesis of bandstop filters (BSF) based on the analysis of the spectrum of complex eigenfrequencies of multimode resonators forming a filter is described. Two types of BSF resonators, which are formed by cross-section enlargements of a finite length of a rectangular waveguide in E- or H-plane, are considered. It was shown that a BSF of the first type had no spurious stopbands and practically did not introduce a loss in the passband. The high accuracy of the filter design is confirmed by the experimental data.< >