Performance assessment of bi-scalar beamformers in practical phased array feed systems

We assess the sensitivity and polarimetric performance of a polarimetric phased array feed (PAF) system in which the two sets of nominally orthogonally polarized elements are beamformed separately. Out simulations of an actual PAF system indicate that such bi-scalar instead of full-polarimetric beamforming results in about 4% sensitivity loss and an XPD of about 45 dB. Our measurements confirm the sensitivity loss, but indicate worse polarimetric performance than the simulations. We indicate how the performance of a PAF system with bi-scalar beamforming can be improved by beamforming of the cross-polarization signals and polarimetric corrections to the beamformer outputs.