Feasible adjoint sensitivity technique for EM design exploiting Broyden´s update

The EM-FAST feasible adjoint sensitivity technique has been proposed for use with frequency domain electromagnetic solvers. It employs finite differences to approximate the derivatives of the system matrix with respect to the design parameters. Here, we propose to estimate and update these derivatives by the classical Broyden technique. This significantly accelerates the response sensitivity analysis when EM-FAST is used for gradient-based optimization. Regardless of the number of design parameters, the response sensitivity is obtained with. computational overhead negligible in comparison with the system analysis. Our EM-Broyden technique is illustrated through the optimization of a Yagi-Uda antenna.