Efficient analysis of curved frequency selective surfaces

This article presents the analysis of frequency selective surfaces (FSS) embedded in a curved supporting structure. This very complex task is simplified by combining rigorous spectral domain approach with simple free-space analysis method. To enhance efficiency and accuracy, the new hybrid method splits the analysis in two distinct parts depending on the curvature and distance. In the first part asymptotic extraction technique is used to achieve faster convergence of the spectral domain technique, and it is used for closely placed elements. For distant elements the analysis is based on the free-space approach modified with an additional correction term. Verification of the new method is shown using a spherical FSS composed of circular rings, but also a way to extend the method to arbitrary curved structures is proposed. Finally, the radiation properties of curved FSS are compared with an equivalent metal reflector.