In this work, the synthesis of clustered phased array antennas characterized by an irregular organization of tiles modules is addressed. By exploiting tiling theorems drawn from the mathematical theory, optimal and sub-optimal methods for the optimization of tiles arrangements and the corresponding excitations minimizing user-defined cost functions are presented. An enumerative approach able to retrieve the optimal clustering providing the maximum aperture coverage and the best radiation performance is proposed to deal with the synthesis of low/medium-size arrays. Based on the same optimal theorems and still exploiting the algorithmic procedures at the basis of the enumerative approach, an innovative schemata-bas ed optimization method is i...