A Wideband Dual-Circularly Polarized Inverted Quad-Ridged Elliptical Waveguide Horn Antenna

Abstract

This letter presents a balanced-feed circularly polarized inverted quad-ridged elliptical waveguide horn antenna with a low axial ratio (AR) and elliptical radiation pattern. A wideband single-mode operation in dual polarizations is achieved, based on initial analysis of the modes and field patterns within the inverted ridged elliptical waveguide, which is essential for achieving a broadband low AR. Furthermore, a slotted ridge is proposed to elegantly adjust the phase relationship between the two polarizations over the entire operating frequency range, in response to the non-linear variation in propagation phase velocity with frequency caused by elliptical nonrotational symmetric structures. The fabricated antenna exhibits a 66.7% relative bandwidth from 4 to 8 GHz with an AR < 2.6 dB, reflection coefficient < -17 dB, and isolation > 35 dB for dual circular polarizations.