Frequency Selective Surfaces

Traditionally, frequency selective surfaces (FSSs) comprising structures with periodicity in two dimensions have important applications as spatial filters in microwave and optics. Due to the manufacturing process, they are usually in the form of printed patches on a dielectric substrate or apertures in a conducting screen. Multiple FSS screens and dielectric layers can be stacked together to meet desirable spectral filter responses. For these structures, a surface discretization of the unknown currents and/or electric fields is more convenient, and efficient integral equation solutions are sought thereafter. Recent developments in manufacturing processes, material properties, and new wave phenomena call for periodic structures with three-dimensional (3D) unit-cell elements. There are situations that a volumetric discretization of the unit cell is more appropriate, and differential equation solutions are preferred. The advent of powerful commercial simulation tools allows effective FSS designs with more flexibility. Compounded with the popularity of 3D printings, some previously unimaginable FSS structures can now be cost-effectively realized. Exploitation of transmission and reflection information obtained from FSS also paves the way for better antenna designs.