Passband Tunable Reconfigurable Frequency-Selective Surface With Wide Tuning Range

In this article, a transmission passband tunable reconfigurable frequency-selective surface (RFSS) with a wide tuning range is proposed. First, the design guidelines of a wide tuning range for RFSS embedded with varactors are deduced based on the equivalent circuit model (ECM) method. An ECM with passband wide range tunability is proposed. Second, a paradigm is designed based on the proposed ECM and the design guidelines. The proposed RFSS unit can provide a series of tunable transmission passbands from 1.51 to 4.96 GHz (with a relative bandwidth (RBW) of 106.6%) by embedded voltage-driven varactors and p-i-n diodes. Meanwhile, the transmission passbands can maintain high transmittance (insertion loss (IL) fluctuates between 0.35 and 2.55 dB). In addition, taking full advantage of the tunability of RFSS, the proposed unit can maintain the resonant frequencies and IL stable, when the incident angle varies from 0 $<^>{\circ}$ to 70 $<^>{\circ}$ from the simulated results. Finally, the prototype is fabricated and measured. The measurement and simulation results are in good agreement. The excellent properties of the proposed unit verify the effectiveness and feasibility of the proposed design method. This article provides a practical scheme to broaden the passband tunable range and the application scenarios of RFSS.