Analysis of rectangular waveguide filters and polarisers with reduced width E plane stubs

Two different rectangular mode matching methods are applied to the design of corrugated waveguide filters and polarisers with reduced width corrugations. The basic building block used in the analysis consists of a short rectangular or square waveguide with corrugations on the side walls. The generalised scattering matrix of the building block is obtained using two different mode matching methods. Scattering matrices of multiple cell blocks are cascaded to model low-pass filter and polariser structures. In the case of the polariser it is necessary to solve for both TE₁₀ and TE₀₁ orthogonal mode excitations. In the first method the TE and TM eigen modes of the cross shape region formed by the inclusion of reduced width corrugations are solved numerically and the coupling of these modes to the input and output rectangular waveguide modes is formulated. In the second method the central rectangular cell block is treated as a cavity and rectangular waveguides may be connected to the block with the use of generalised scattering matrices