Reduction of cross polarization in higher frequency for circularly polarized broadband antenna with L-Shaped probe and parabolic short wall

Abstract

Reduction of cross polarization in higher frequency is performed for a circularly polarized broadband antenna consisting of a waveguide and an L-shaped feed probe. Cross polarization over a wide elevation range was enhanced in higher frequency beyond the cutoff frequency of first higher order mode in the previously proposed structure. To reduce the cross polarization, the surface of a short wall of the waveguide is modified to be curved parabolically. And, coefficients of the parabolic function for the short wall are optimized to provide the ideal amplitude ratio characteristics. As a result, cross polarization is reduced by 5dB to 10dB using the short wall.