Antenna arrays are the most effective solution for radiating systems that need high directivity and low sidelobe level, such as radio astronomy, remote sensing, and radar applications. Typically, antenna arrays are only designed for narrowband applications, thus several radiating systems are to be employed, one per each operating bandwidth. Recently, with the aim of reducing the number of antenna system onboard a vehicle, such as aircrafts, satellites or terrestrial vehicles, a great interest has been focused on techniques for designing wideband antenna arrays. Therefore most of the dissertation deals with novel techniques for the synthesis of both narrowband and wideband planar antenna array, aiming to provide a pretty good wide-angle scanning while imposing several constraints to meet imposed by the designer. In addition, an advanced technique for the synthesis of a wideband miniaturized single-element antenna placed in realistic environments has been developed. Furthermore an hybrid technique for the analysis of conformal arrays of antennas as well several synthesis procedures have been developed. Mutual coupling has been also taken into account.