Modal Expansion Analysis of T-Shaped Waveguide

The T-shaped waveguide (T-waveguide for short) is a new kind of wideband waveguide which is easier to fabricate than conventional wideband waveguides. This paper presents the modal expansion analysis of the T-waveguide. The T-waveguide is first divided into four rectangular domains. The electromagnetic fields in each domain are expressed by suitable mode functions. The continuity of tangential electromagnetic fields along the interface of neighboring regions is enforced by the Galerkin's matching process and a matrix equation is thus derived. The cutoff wavenumbers of the T-waveguide are then found from the matrix. The results are in good agreement with those obtained by CST Microwave Studio. The proposed method provides fast calculation of the T-waveguide cutoff wavenumber, which is of guiding significance to the design of T-waveguide.