Improved Cross-Polarization Performance in Reflectarray Antennas by Direct Optimization of the XPD and XPI Parameters

Abstract

Current satellite missions for communications demand a high polarization purity, with figures of merit such as the crosspolar discrimination (XPD) better than 33 dB. In order to accomplish these values, some kind of optimization must be carried out to improve cross-polarization performance. The most common approach is to minimize the crosspolar component of the radiation pattern in the region of interest. Nevertheless, this strategy produces suboptimal results since the figure of merit for cross-polarization performance is optimized indirectly. Thus, it is proposed to directly optimize the XPD to improve the polarization purity of reflectarrays for satellite missions. For that purpose, the generalized Intersection Approach algorithm is employed to optimize a very large shaped-beam reflectarray for a direct broadcast satellite application with a European coverage. It is shown that directly optimizing the cross-polarization figure of merit provides better results than the usual approach of minimizing the crosspolar pattern.