A Model-Order Reduction Approach for Electromagnetic Problems With Nonaffine Frequency Dependence

The aim of this paper is to present a novel model-order reduction (MOR) technique for the efficient frequency-domain finite-element method (FEM) simulation of microwave components. It is based on the standard reduced-basis method, but the subsequent expansion frequency points are selected following the so-called sparsified greedy strategy. This feature makes it especially useful to perform a fast-frequency sweep of problems that lead to systems of equations exhibiting a nonaffine frequency dependence. This property appears, for example, when the excitation of the problem is characterized by a frequency-dependent waveguide mode pattern, or when the computational domain includes materials with frequency-dependent permittivity or permeability tensors. Moreover, the new MOR scheme can be also used to accelerate the frequency sweep of problems with many excitations, for which the standard reduction algorithms tend to be time-consuming. Its effectiveness and accuracy is verified through analysis of three microwave structures: planar microstrip branch-line coupler, three-port waveguide junction with ferrite post, and an eighth-order dual-mode waveguide filter.