Phase-only synthesis of flat aperiodic reflectarrays

Abstract

A phase-only power pattern synthesis technique for flat (aperiodic) microstrip reflectarrays with elements arranged on a nonregular lattice is presented. The approach mitigates the typical design issues of reflectarray antennas related to the computational burden and to the possible occurrence of suboptimal solutions which are here even more significant due to the non-regular element lattice. This is done by a convenient two-stage procedure for choosing the starting point of the iterations and by proper representations of the unknowns of the problem. Design constraints on the element positions are also imposed to avoid overlapping as well as too large spacings. The algorithm, accelerated by parallel programming on Graphics Processing Units, has been analyzed against the cases of a pencil-beam and of a shaped- beam involving a typical South America coverage. In order to properly characterize the performance of the synthesis algorithm, it has been applied also to the design of reflectarrays with elements located on a non-regular lattice. The results show that in the case of non-regular lattice better directivities, better coverage behavior and better side- lobe levels are achievable as compared to reflectarrays characterized by a regular lattice.