Use of three-dimensional field simulators in the synthesis of waveguide round rod bandpass filters

This paper presents the generalized bandpass filter design method of Levy and Rhodes based on three-dimensional (3D) electromagnetic analysis and discontinuity modeling using commercial software. It shows how to use Levy and Rhodes's famous method for very accurate theoretical designs of waveguide post filters, using modern 3D solvers based on the finite element method, the mode matching method, and the transmission line matrix analysis method. This is the first time that design curves and equations are being presented for constant diameter single and double round rod filters by full electromagnetic modeling. The approach is demonstrated with designs for a number of waveguide round rod filters. This paper also demonstrates the generality of the method. This method can be applied to many other types of coupled resonator waveguide band pass filters.