Usually, a frequency-selective surface (FSS) comprises one or more screens with two-dimensional periodic patterns, which are generated by a unit cell containing metallic patches or apertures. Now, a design composed of a metallic cross-dipole element connected by switches has been introduced by Pennsylvania State University's Xiaotao Liang, Douglas H. Werner, and Brian Weiner.
The design is housed on an exposed silicon substrate. Because silicon's conductivity can be varied over a large dynamic range, this substrate material is well suited for producing high-speed switches. The concept is applied to two types of radio-frequency-selective-surface (RFSS) examples that operate at a target frequency of 100 GHz. Using a genetic algorithm (GA), the switch's optimal performance is obtained for desired excitation frequencies with respect to variations of the design's geometric and electrical parameters. See "A Novel Concept for Reconfigurable Frequency Selective Surfaces Based on Silicon Switches," Microwave And Optical Technology Letters, January 2007, p. 109.