Original parasitic elements for cross-polarization control in reflector antennas

For synthetic paraboloids illuminated by a linearly polarized feed, the maximums of the cross-polarized field occur in 45 degrees planes (Condon lobes). A significant reduction in amplitude of the Condon lobes has been achieved using original passive elements set on the inner parabolic dish. The purpose is to excite currents with suitable magnitude and phase in passive elements whose radiation causes reduction of the cross-polar secondary pattern without affecting the nominal performances. Theory based on the method of moments is used to evaluate the current distribution on the elements. Physical optics and the geometric theory of diffraction are chosen to compute the secondary far field, taking into account contributions of active (feed) and passive sources.<>