Expedited two-objective dimension scaling of compact microwave passives using surrogate models

Geometry scaling of compact microwave structures is a challenging problem because of complex relationships between the physical dimensions and electrical characteristics, mostly caused by considerable cross-couplings in densely arranged layouts. Here, a procedure for expedited dimension scaling of compact microwave couplers with respect to two independent criteria has been presented. Our approach involves inverse surrogate models and permits low-cost re-design of the coupler structure for a required operating frequency and power split ratio. It is illustrated using a folded microstrip rat-race coupler.