Pareto optimization of wideband circular ring arrays

Our aim is to synthesize a wideband planar array which have to fulfill constraints imposed to the radiation pattern in terms of side lobe level (SLL) within a specified angular range. More in detail, we focus on a particular 2D configuration of antennas, namely the class of Concentric Ring Arrays (CRAs). Planar arrays present advantages with respect to linear ones in case of three dimensional beamforming and CRAs are also symmetric and guarantee a nearly invariant pattern for a full azimuthal coverage. We also require that the proposed solution is physically feasible, thus the minimum distance between the elements is fixed to be not lower than the dimensions of antenna (being this latter dictated by its physical size and by the need of mitigating the effect of e.m. coupling). Since we are interested in developing an efficient code for more than two objectives a dedicated version of a multi-objective genetic algorithm, called Nondominated Sorting Genetic Algorithm (NSGA-II) has been implemented to optimize the array factor of CRAs at three different frequencies.