Synthesis of Sparse Concentric Ring Arrays With Minimum Element Spacing Control by Modified Two-Step Optimization Strategy

A modified two-step optimization strategy (MTSOS) is proposed for the synthesis of sparse concentric ring arrays (CRAs). The strategy adopts the discretizing-then-optimizing strategy, which can effectively reduce the error caused by discretization. In the first step of MTSOS, densely spaced concentric continuous current rings are discretized using a deterministic method, constructing ring array candidates with small ring-to-ring spacing. An upper boundary of full-space radiation pattern is introduced to reduce the pattern constraints, which significantly reduces the computational workload. In the second step, the alternating convex optimization is extended to find sparsely spaced ring arrays with minimum ring spacing control from the set of optimal ring array candidates. Two examples demonstrate the effectiveness of MTSOS in synthesizing nonuniformly excited sparse CRAs.