Tunable High-Impedance Surface With a Reduced Number of Varactors

An efficient approach for obtaining an active high- impedance surface (HIS) is presented. The novel design allows us to synthesize a tunable HIS by drastically reducing the number of the active elements employed. The conventional loading of a single varactor for each of the unit cells of the frequency selective surface (FSS) is overcome by connecting the FSS unit cells to a feeding network located behind the ground plane through metallized vias. A waveguide demonstrator of the proposed structure has been designed, realized, and tested. In the example shown herein, the feeding network allows us to apply a single varactor to a group of eight cells in order to obtain a tunable HIS.