  The design of phased arrays able to generate arbitrary-shaped beams through a
sub-arrayed architecture is addressed here. The synthesis problem is cast in
the excitation matching framework, so as to yield clustered phased arrays
providing optimal trade-offs between the complexity of the array architecture
(i.e., the minimum number of control points at the sub-array level) and the
matching of a reference pattern. A synthesis tool based on the k-means
algorithm is proposed for jointly optimizing the sub-array configuration and
the complex sub-array coefficients. Selected numerical results, including
pencil beams with sidelobe notches and asymmetric lobes as well as shaped main
lobes, are reported and discussed to highlight the peculiarities of the
proposed approach also in comparison with some extensions to complex
excitations of state-of-the-art sub-array design methods.
