Efficient estimation of adjoint-variable S-parameter sensitivities with time domain TLM

Abstract

We present a novel algorithm for efficient estimation of S-parameter sensitivities with the time-domain transmission line modelling (TLM) method. The original electromagnetic structure is simulated using TLM to obtain the S-parameters in the desired frequency band. For each port, an adjoint TLM simulation that runs backward in time is derived and solved. The sensitivities of the S-parameters in the desired frequency band are estimated using only the original and adjoint simulations. For a structure with N_p ports and n designable parameters, our approach requires only N_p additional simulations regardless of n. This can be easily contrasted with the 2nN_p additional simulations required by the central difference approximation. Our algorithm is illustrated through the estimation of S-parameter sensitivities with respect to the dimensions of waveguide discontinuities. Very good match is obtained between our sensitivity estimates and those obtained using central difference approximation. Copyright © 2005 John Wiley & Sons, Ltd.