Fast full-wave technique for CAD of polarizers based on double-ridge waveguide sections

Full-wave technique for a computer-aided design (CAD) of a wide class of square waveguide 90-degree polarizers based on double-ridge sections is presented. The proposed hybrid full-wave technique for analysis of polarizers is based on the Galerkin method with taking into account the edge condition, mode-matching technique and generalized scattering matrix method. The weighted Gegenbauer polynomials are used as the basis functions taking into account the field asymptotic at the edges when solving the eigenvalue problem for a ridge waveguide. Compact Ku-band waveguide 90-degree polarizers are designed for operation within frequency bands 12-12.5/14-14.5 GHz and 12.1-12.5/17.7-18.1 GHz. VSWR within two operational bands of polarizers is less than 1.04, differential phase shift is about 90 degrees +/- 0.5 degrees and 90 degrees +/- 1.5 degrees, respectively. The length of polarizers is reduced at a factor about 2 in comparison with the known corrugated square waveguide polarizers.