Waveguide diplexer based on E-plane ridged sections and diaphragms

A novel design of waveguide diplexer for millimeter wave applications is proposed. The diplexer is based on E-plane metal insert filters with ridged sections and longitudinal diaphragms in rectangular waveguide. The diplexer includes the E-plane waveguide bifurcation with parallel waveguide channels and stepped waveguide transition. The proposed diplexer design provides extended stop-band of the filters, increased attenuation within stop-band, high slope selectivity and reduced dimensions. CAD of filters and diplexers is based on mode matching technique, Galerkin method and generalized scattering matrix method. The eigenvalue problem for ridged waveguide is solved by Galerkin method with weighted Gegenbauer polynomials as the basis functions taking into account the edge condition. This approach ensures fast convergence and accuracy of the total hybrid solution. Ka-band diplexer is designed for operation within frequency bands 37,06–37,62 GHz and 38,32–38,88 GHz. Reflection loss within passbands of diplexer is better than −29 dB, isolation of the channels is about −48 dB. The length of diplexer is reduced at a factor 1,5 in comparison with the known designs.