Improved trust-region gradient-search algorithm for accelerated optimization of wideband antenna input characteristics

Abstract

Full-wave electromagnetic (EM) simulation models are ubiquitous in carrying out design closure of antenna structures. Yet, EM-based design is expensive due to a large number of analyses necessary to yield an optimized design. Computational savings can be achieved using, for example, adjoint sensitivities, surrogate-assisted procedures, design space dimensionality reduction, or similar sophisticated means. In this article, a simple modification of a rudimentary trust-region-embedded gradient search with numerical derivatives is proposed for reduced-cost optimization of input characteristics of wideband antennas. The approach exploits information and history of relative changes of the design (as compared with the trust region size) during algorithm iterations to control the updates of components of the antenna response Jacobian, specifically, to execute them only if necessary. It is demonstrated that the proposed framework may lead to over 50% savings over the reference algorithm with only minor degradation of the design quality, specifically, up to 0.3 dB (or <3%). Numerical results are supported by experimental validation of the optimized antenna designs. The presented algorithm can be utilized as a stand-alone optimization routine or as a building block of surrogate-assisted procedures.