Center-fed parabolic reflector antenna cross polarization due to slightly right-left asymmetric feed patterns

Abstract

Slightly right-left (R-L) asymmetric feed pattern effects on a center-fed parabolic reflector antenna cross polarization have been described with some numerical computation examples, noting that measured feed patterns, both in the E plane and in the H plane, are generally not completely R-L symmetric and have a slightly different R-L field intensity which produces asymmetrical reflector surface currents. It is shown from the numerical computations that even a slight feed asymmetry, in both amplitude and phase, gives rise to a cross polarization in the secondary prinicpal planes and that, in particular, phase R-L asymmetry incurs two-dimensional movement of principal- and cross-polarized patterns resulting in the rapid increase of principal-plane cross polarization as well as the maximum cross polarization, principal-pattern beamshift, and the sidelobe variations.