Sensitivity analysis of scattering parameters with electromagnetic time-domain simulators

We propose an efficient adjoint-variable approach to the sensitivity analysis of S-parameters obtained from full-wave electromagnetic (EM) time-domain simulations. It allows the computation of the S-parameter derivatives with respect to the design variables with negligible overhead. No solutions of adjoint EM problems are needed. The computation is done as an independent post-process outside the solver. The sole requirement is the ability of the solver to export the field solution at user-defined points. Most commercial solvers have this ability, which makes our approach readily applicable to practical design problems. The approach is verified through the analysis of waveguide and antenna structures using commercial simulators.