FDTD-based transient adjoint sensitivity analysis

We present an accurate technique for estimating adjoint transient sensitivities using time-domain electromagnetic analysis. Similar to conventional adjoint-based methods, our approach requires only two simulations: the original and adjoint analysis of the system, regardless the number of system parameters. We show that the complete adjoint transient sensitivities of a time-dependent field for all time steps can be evaluated through an additional field convolution process operated on the stored fields from the two simulations.