Targeted Design of Single-Layer Frequency-Selective Surface With Angular Stability Based on Topology Optimization

Aiming at angular stability, a frequency-selective surface (FSS) with stable response to TE and TM polarization at large incidence angles is designed by the gradient-based topology optimization approach. According to the adjoint variable method (AVM), the adjoint sensitivity analysis for periodic boundary problems is formulated, and its physical significance is described. The optimization of FSS is a typical multisolution optimization problem, which has a slow convergence speed and is prone to generate morbidity solutions. Therefore, to obtain the desired FSS, an appropriate initial value is selected to avoid the optimization result falling into a morbidity solution and the objective function is improved to make it gradually converge. The optimized FSS is insensitive to polarization and it has stability at oblique incidence angle from 0° to 75°. The measured results are in good agreement with the simulation ones. It is shown that this is an effective design method for the stable response to the variety of incident angles, which can solve the periodic problem of multifrequency, multi-angle, and multimode.