Adjoint Sensitivities of Real Objective Functions for Time-Domain TLM

We review the Adjoint Variable Method (AVM) for efficient estimation of real objective function sensitivities with time-domain TLM. The original electromagnetic structure is first simulated using TLM. An adjoint TLM simulation that runs backward in time is derived and solved. The sensitivities of the objective function with respect to all designable parameters are estimated using only the original and adjoint simulations. The AVM approach is illustrated through the estimation of the sensitivities of objective functions with respect to the dimensions of waveguide discontinuities.