Robust Parameter Tuning of Antenna Structures by Means of Design Specification Adaptation

Parameter tuning through numerical optimization has become instrumental in the design of high-performance antenna systems. Yet, practical optimization faces several major challenges, including high cost of massive evaluations of antenna characteristics, normally involving full-wave electromagnetic (EM) analysis, large numbers of adjustable variables, the shortage of reasonable initial solutions in the case of topologically complex structures, and multimodality of the objective function landscapes. The last two reasons foster the use of global search routines, which might be prohibitively expensive. This article proposes a novel procedure for efficient and reliable antenna optimization by means of design specification adaptation. Using appropriate selection criteria and predictions from a linear expansion model, the ability of improving the current design is verified, and—in the case of a negative outcome—performance requirements are temporarily relaxed. The adjustment is carried out prior to each iteration of the optimization process with the specifications eventually converging to their original levels. The algorithm is intended to improve the efficacy of local optimizers if the target operating frequencies of the structure at hand are severely misaligned with respect to those at the available initial design. This eliminates the need for global routines and greatly enhances the robustness of the search process, as demonstrated using several antenna structures optimized under different scenarios.