Sensitivity Analysis with Discrete Perturbation of Planar Structure on Method-of-Moment Grids

The system response sensitivity is needed in gradient-based optimization to evaluate changes in the response in the form of the response gradient with respect to the design parameters. The adjoint-variable method (AVM) is known to be the most efficient approach to design sensitivity analysis. It is well established in engineering areas such as structural design [1], circuit and control theory, [2] [3], as well as in microwave design [4]. However, feasible implementation remains a challenge due to the complexity of these techniques. The first applications with the method of moments (MoM) were demonstrated in [5]–[7]. Later, the analytical derivation of the system matrix derivatives was abandoned as impractical. Instead, approximations of the system matrix derivatives are employed using finite differences. However, the computational speed with this approach is still limited due to the following factors: (a) the need to actually compute the perturbed system matrices, and (b) the need to perform an adjoint-system analysis.