Unconventional Array Architectures for Next Generation Wireless Communications

Phased arrays have emerged as the most suitable antenna technology for several modern wireless communication applications which require highly flexible and high‐performing antennas capable of supporting real‐time adaptive beam reconfiguration, user tracking, and MIMO processing. Achieving these objectives with cost‐effective phased array layouts is crucial to minimize fabrication and maintenance costs. In recent decades, the need of inexpensive but high‐performance antenna systems has driven the research towards unconventional array architectures. Accordingly, a wide set of innovative developing design methodologies have been proposed to properly manage the additional degrees of freedoms which are not present in conventional architectures, such as the array element locations in sparse arrays, or the sub‐array configuration in clustered/tiled arrays. The objective of this Chapter is to review the recent advances and trends in the synthesis of unconventional architectures for wireless applications. Towards this end, the formulation of the associated synthesis problem is discussed, and the theoretical motivations, fundamentals, and applicative guidelines for current state‐of‐the‐art strategies in unconventional phased array synthesis for next generation wireless communications are illustrated.