Multi-objective optimization of microwave couplers using corrected domain patching

Practical design of microwave components and circuits is a compromise between various, often conflicting objectives. In case of compact structures, the trade-offs are typically concerned with the circuit size and its electrical performance. Comprehensive information about the best possible trade-offs can be obtained by means of multi-objective optimization. In this paper, we propose a computationally efficient technique for identifying a Pareto front representation for miniaturized microstrip couplers. We exploit a sequential domain patching technique that constructs a path between the extreme Pareto-optimal designs (found by single-objective optimization runs). This stage is executed using coarse-discretization EM simulation models. Selected non-dominated designs from the path are subsequently corrected in order to fulfill prescribed design constraints (in particular, equal power split at the operating frequency), and refined in order to obtain the final Pareto set representation at the level of high-fidelity EM simulation model of the structure at hand. The proposed technique is demonstrated using a miniaturized microstrip rat-race coupler.