Active frequency selective surface (AFSS)

This paper presents a low-profile, dual-stopband active frequency selective surface (AFSS) with an ultra-wide band ratio (BR) to overcome the limited tuning range and suboptimal profile of current designs. The proposed design consists of a periodic pattern printed on the top of a thin substrate and a bias network on the bottom, with varactor diodes symmetrically mounted on the top metal layer. Based on the equivalent circuit model, the mechanism of wideband tuning is analyzed theoretically.