Worst-case design of multi-layer absorber backed by a PEC plate

The authors consider the worst-case design of a uniformly layered absorber backed by a PEC (perfectly electrically conducting) plane under general cases. The absorber, composed of several uniform layers of a homogeneous medium, is assumed to be illuminated by a plane wave at an arbitrary incidence angle, polarization, and frequency in a certain band. The design parameters, including electromagnetic properties and the thickness of each layer, are optimized so that the unified reflected power gets a minimum for the worst case that could occur. Approaches to realistic absorber design are considered by constraining all of the electromagnetic parameters of the medium in each layer within realizable regions. The design is formulated as a nondifferential constrained optimization problem, and the flexible tolerance polyhedron method is adopted for solving it. Some numerical results are obtained. Sensitivity tests show that the performance of the optimized coatings is stable when the optimal parameters are subject to small tolerances.<>