Design and experimental validation of dual-band circularly polarised horn filtenna

A simple and cheap solution is proposed to transform a wideband and linearly polarised horn antenna in a dual-band circularly polarised horn filtenna. The filtering and polarisation transformation capabilities are achieved by inserting inside the throat of the horn a complementary electrically small resonator etched on a thin metallic sheet. In this way, the overall structure is well matched in two frequency ranges (13–14 and 16.4–17 GHz) and radiates left-handed and right-handed circularly polarised fields in the lower and upper frequency bands, respectively. The measurements performed on a realised prototype confirm the good performance of the proposed structure, which may be employed in satellite communication systems requiring different circular polarisation for the up- and down-link frequency ranges.