Investigation on crosspolar performance of a coaxial fed dual mode matched rectangular feed horn with step discontinuity

Multimode horns are used as matched feed for offset reflector antennas for reducing cross-polarization in the main beam. This paper investigates the crosspolar performance of a coaxial fed dual mode matched rectangular feed horn with step discontinuity. The design of dual mode rectangular horn as matched feed for an offset parabolic reflector antenna is presented. In this design, dominant TE₁₀ mode is combined with TE₁₁ mode at the horn aperture. A parametric study was carried out using HFSS to evaluate the horn performance when the waveguide is excited directly as well as with coaxial feed line excitation. Appropriate methods have been used for broadening operation bandwidth of the coax fed horn with a small decrease in the crosspolar performance.