Single and Dual Helical Polarizers for Millimeter-Wave Horn Antennas

This paper presents a helical-based polarizer integrated into the aperture of a pyramidal horn antenna, designed to convert linearly polarized radiated fields into either right-or left-handed circular polarization over two distinct bands. The integrated polarizer is entirely passive and functions as a parasitic element, positioned between the waveguide launcher and the radiating aperture. The polarization type is determined by the winding orientation of the integrated helical wire. Two distinct approaches are explored for polarization conversion. In the first approach, a single helical wire is aligned along the center of the horn aperture and designed to provide polarization conversion with a peak realized gain of 14.3 dBic over the frequency range of 26 GHz to 32 GHz. The second method incorporates two helical wires as polarizers: one centered in the aperture and a second, oppositely wound, placed along the horns sidewall. This configuration provides polarization conversion with a maximum realized gain of 15.25 dBic between 33 GHz and 37 GHz. For both bands, a cross-polarization level that goes beyond 23 dB is achieved. Experimental testing of both designs demonstrates a strong agreement between simulated and measured results, confirming the effectiveness of the proposed polarization conversion technique.