Wideband dual polarized line feed development for a cylindrical reflector radio telescope

A new wideband dual polarized line feed element for a cylindrical reflector radio telescope has been presented. A novel feeding arrangement using microstrip baluns reduces element cost and losses compared to dual polarized dipole designs using hybrid coupler feeds. An 8-element line feed was simulated, constructed and measured for array radiation performance across a 1.57:1 frequency range, with good agreement between simulation and measurement. Beam equalization for both polarizations in the transverse plane was obtained using channels placed beside the elements. Cross-polar levels in the transverse plane patterns are shown to increase with scanning angle. Element patterns in the longitudinal plane, for both polarizations, show excellent polarization purity for wide scan angles. Implementation of the line feed at the MOST (Molonglo observatory synthesis telescope) will demonstrate a world first in polarimetric imaging using a cylindrical reflector radio telescope.