Surrogate modeling of impedance matching transformers by means of variable-fidelity electromagnetic simulations and nested cokriging

Accurate performance evaluation of microwave components can be carried out using full-wave electromagnetic (EM) simulation tools, routinely employed for circuit verification but also in the design process itself. Unfortunately, the computational cost of EM-driven design may be high. This is especially pertinent to tasks entailing considerable number of simulations (eg, parametric optimization, statistical analysis). A possible way of alleviating these difficulties is utilization of fast replacement models, also referred to as surrogates. Notwithstanding, conventional modeling methods exhibit serious limitations when it comes to handling microwave components. The principal challenges include large number of geometry and material parameters, highly nonlinear characteristics, as well as the necessity of covering wide ranges of operating conditions. The latter is mandatory from the point of view of the surrogate model utility. This article presents a novel modeling approach that incorporates variable-fidelity EM simulations into the recently reported nested kriging framework. A combination of domain confinement due to nested kriging, and low-/high-fidelity EM data blending through cokriging, enables the construction of reliable surrogates at a fraction of cost required by single-fidelity nested kriging. Our technique is validated using a three-section miniaturized impedance matching transformer with its surrogate model rendered over wide range of operating frequencies. Comprehensive benchmarking demonstrates superiority of the proposed method over both conventional models and nested kriging.