Cost-Efficient Large-Scale Re-Design of Multi-Band Antennas Using Orthogonal Scaling Directions

Re-design of antenna systems to operate at different operating frequencies is a practically important yet challenging endeavor. In particular, it involves simultaneous tuning of multiple geometry parameters, which incurs considerable computational expenses when electromagnetic (EM) analysis (necessary to ensure reliability) is used. Further, if the target centre frequencies are distant from that of the already established design, global optimization might be required, which entails even higher costs. This work develops a novel and cost-efficient technique for multi-band antenna re-design. The key concept of our approach is identification of a set of orthogonal scaling directions, which allow for approximately independent relocation of individual center frequencies. Large-scale design adjustment along these vectors is interleaved with local tuning, executed to correct unavoidable scaling errors and to improve the primary performance parameters. The scaling and correction steps are iterated until convergence. The introduced framework has been validated using two microstrip antennas, both re-designed for target frequencies unattainable through traditional tuning techniques. The obtained results corroborate the ability of our algorithm to precisely control the operating conditions, as well as low running cost corresponding to just about 170 EM simulations of the antenna under design.