A circular polarizer designed with a dielectric septum loading

This paper presents a simple method to realize a circular polarizer by inserting a dielectric septum in the middle of the cylindrical waveguide. Since fixing slots are built to precisely locate the septum, dual-compensation slots are made in the orthogonal plane to balance the effects of the fixing slots. The measured axial ratio is smaller than 0.5 dB and the phase difference is flat in the frequency range from 60 to 62.25 GHz. In addition, the return losses are better than -13 dB for both E_x and E_y polarizations in the same frequency range. This design has the added advantage that poor phase differences resulting from fabrication error or an inaccurate dielectric constant can easily be improved by adjusting the length of the inserted dielectric septum.