Determining the equivalent impedance boundary condition for material-coated corrugated gratings based on the genetic algorithm

An impedance boundary condition model based on the genetic algorithm is proposed to approximate arbitrary coated gratings in scattering problems. The periodic structure is replaced by a periodic impedance boundary condition (IBC) on a virtual surface. The boundary impedance and the position of the surface are optimized by matching the reflection coefficients to the rigorous numerical solution at a number of incident angles. Similar to traditional IBC models, this approach is most effective when the coating material is high-loss and of high contrast. Finally, the output IBC model generated by this algorithm can be incorporated into an existing computational electromagnetics code to assess the performance of the corrugated surface when mounted on complex platforms.