FDTD Analysis of Cylindrical Waveguides With Both Axial and Azimuthal Corrugations

Cylindrical waveguides with both axial and azimuthal corrugations can be found in a variety of microwave devices, where they operate mainly as mode converters. In this work, we study the scattering parameters and the mode conversion in a structure consisting of two axial corrugations and an azimuthally corrugated section, by using the in-house FDTD code COCHLEA. General trends, with respect to the dependence of the mode conversion on the geometrical parameters, are obtained, focusing on the possibility to use the structure for improved mode suppression in gyrotron beam tunnels.