Inverse surrogate models for fast geometry scaling of miniaturized dual-band couplers

Re-design of microwave structures for various sets of performance specifications is a challenging task, particularly for compact components where considerable electromagnetic (EM) cross-couplings make the relationships between geometry parameters and the structure responses complex. Here, we address geometry scaling of miniaturized dual-band couplers by means of inverse surrogate modeling. Our approach allows for fast estimation of the optimum values of structure dimensions corresponding to required operating frequencies. The inverse surrogate is constructed based on a set of reference designs obtained by optimizing the equivalent circuit model of the coupler, and subsequently corrected using output space mapping. As demonstrated using a compact dual-band microstrip branchline coupler example, geometry scaling is possible in a wide range of operating frequencies and at a very low cost of just a single EM simulation of the structure at hand.