Characteristics of circular waveguide with step discontinuities including coaxial feeders

The reflection and transmission characteristics of a circular waveguide with step discontinuities including coaxial feeders are evaluated using Galerkin's method of moments. Two sizes of cylindrical step discontinuities of large and small diameters are considered. This cylindrical discontinuity is placed so that it aligns the center axis with the circular waveguide. Because of the axisymmetric structure as well as the assumption of a TEM-mode incident wave, which is an axisymmetric mode, the scattered waves from the structural discontinuities can be expressed as axisymmetric modes. Therefore, the analysis can be considerably simplified. The condition to cancel reflected waves by placing two discontinuities at the proper distance is confirmed.