Combined-Phase-Shift Waveguide Polarizer

A waveguide polarizer exploiting two different phase shift phenomena is presented in this letter. Iris-type discontinuities are in fact introduced in a waveguide structure having different propagation constants for the two principal polarizations. In this way, the required 90 differential phase shift is obtained combining the iris phase shift with the waveguide one. Several operative conditions arise from the combination of the two contributions. This approach has been used to design a broadband waveguide polarizer for the C-band antenna feed system of the Sardinia radio telescope with -40 dB reflection coefficients and a -35 dB cross polarization level in a 30% bandwidth.