Local-global space mapping for rapid EM-driven design of compact RF structures

In this work, we introduce a robust and efficient technique for rapid design of compact RF circuits. Our approach exploits two-level space mapping (SM) correction of an equivalent circuit model of the structure under design. The first SM layer (local correction) is utilized to ensure good matching between the equivalent circuit and the electromagnetic model at the component level. On the other hand, the global correction allows for taking into account the electromagnetic couplings between the components. The important advantage of decomposing the low-fidelity model correction into local and global level is that small number of parameter is utilized at each stage, which substantially simplifies and speeds up the parameter extraction procedure. Another advantage is that the local-global SM results in considerably better generalization capability of the surrogate model (as compared to conventional SM). This leads to improved reliability of the optimization process and its reduced computational cost. The proposed technique is validated using an example of a compact microstrip rat-race coupler (RRC) and compared to previous surrogate-assisted attempts to compact RF structure optimization, including implicit SM and sequential SM.