The Generalized Direct Optimization Technique for Printed Reflectarrays

A generalized direct optimization technique (GDOT) for the design of printed reflectarrays using arbitrarily shaped elements with irregular orientation and position is presented. The GDOT is based on the spectral domain method of moments (SDMoM) assuming local periodicity (LP) and a minimax optimization algorithm. The accuracy of the LP-SDMoM for the design of reflectarrays with irregularly positioned and oriented array elements has been verified by comparisons with full wave method of moments. Three contoured beam reflectarrays, forming a high-gain beam on a European coverage area, have been designed: a broadband design, a circularly polarized design using the variable rotation technique, and a design with irregularly positioned array elements. The latter has been manufactured and measured at the DTU-ESA Spherical Near-Field Antenna Test Facility. An very good agreement between simulated and measured patterns have been obtained, showing accuracies that are comparable to those obtained for conventional shaped reflectors.