A.A. Skvortsov, M.A. Soloviev, E.A. Torgashev

Two-ridged waveguide (TRW) and four-ridged waveguide (FRW) belong to transmission lines of complex cross section, where a distribution of electric component of a dominant mode is changed in a cross section. They can be used in building of different microwave systems including setups for thermal processing of dielectric materials. Since the most of such devices operate on a dominant mode, the evaluation of a single-mode regime operating band of waveguides under consideration defined by the broadbandness coefficient is important. Quasi-analytical calculation of cutoff wavelengths of the dominant and the first high-order modes of asymmetrical TRW and FRW is carried out. These cutoff wavelengths define the broadbandness coefficient of structures under consideration. The calculation is done proceeding from the replacement of real electromagnetic systems by the equivalent circuits with lumped inductances and capacitances. Equivalent circuit parameters for calculation of wavelengths of the dominant and high-order modes of waveguides under study were determined taking into account results obtained earlier. In order to confirm an efficiency of the technique considered in present work, a computation results of broadbandness are compared for asymmetrical TRW and FRW. Equivalent circuits method (ECM) and finite element method were used in the computation. Quite good agreement of the results is seen. The use of ECM has allowed finding a simple quasi-analytical dependence in evident form, which defines the influence of asymmetry of sided sections of TRW and FRW upon broadbandness with accuracy suitable for some practically important cases. Moreover, obtained quasi-analytical expressions can be further adapted for calculating broadbandness of asymmetrical TRW and FRW with inhomogeneous dielectric filling.