  An innovative strategy for the design of low-profile wide-angle impedance
matching (WAIM) superstrates to active return loss (ARL) stability of scanned
microstrip-printed periodic phased arrays (PPAs) is presented. Towards this
end, an instance of the System-by-Design (SbD) paradigm is exploited and a
task-oriented formulation of the WAIM synthesis problem is proposed. More
specifically, a customized global optimization strategy is combined with an
accurate and fast modeling of the array ARL, which is based on a
semi-analytical approach, to enable an effective design of multi-layer
structures with both isotropic and anisotropic materials. A set of
representative numerical examples, concerned with different microstrip patch
substrates, lattices, and design constraints, is presented to give the
interested readers some insights on the features and the potentialities of the
proposed implementation.
