TLM-based self-adjoint sensitivities of S-parameters with time-domain electromagnetic solvers

We present a self-adjoint approach to S-parameter sensitivity computation with time-domain electromagnetic (EM) simulators based on the transmission-line matrix (TLM) discretization scheme. The method is applicable with any EM simulator, which can export either the electric field or the incident TLM voltages at user defined points. Our technique converts the electric and magnetic field solution into TLM voltages if the latter are not available (e.g., in FDTD-based simulators). The S-parameter derivatives are computed as an independent post-process whose computational requirements are negligible compared to the full-wave system analysis. Adjoint simulations are not needed if the problem is homogeneous. Our approach is illustrated through waveguide problems solved with a commercial TLM solver.