Variable-fidelity simulation-driven design optimisation of microwave structures

The main obstacle in simulation-driven design optimisation of microwave structures is the high computational cost of high-fidelity electromagnetic (EM) simulation. In this paper, we discuss two computationally efficient design optimisation methodologies that exploit variable-fidelity electromagnetic models. The first technique is based on sequential optimisation of coarse-discretisation EM models. The optimal design of the current model is used as an initial design for the finer-discretisation one. The final design is then obtained in the refinement procedure that uses a polynomial approximation of the coarse-discretisation EM data. The unavoidable misalignment between the polynomial and the high-fidelity model is corrected using space mapping. The second technique also exploits coarse-discretisation EM model, however, the discrepancy between the lowand high-fidelity models is accounted for by appropriate adjustment of the design specifications. Our techniques are straightforward to implement and computationally efficient because the optimisation burden is shifted to the coarse-discretisation models. They are also applicable to virtually any type of microwave structures which is demonstrated using several design examples, including microstrip bandpass filter, planar ultrawideband antenna and a coplanar-waveguide-to-microstrip transition.