Design of a Broadband Switchable Active Frequency Selective Surfaces Based on Modified Diode Model

In this letter, a broadband switchable active frequency selective surfaces (AFSSs) is presented, and the proposed structure is comprised of three metallic layers and two Rogers RT5880 substrates. In order to realize broadband transmission, a second-order bandpass filter is constructed, and the multilayer coupling effect is utilized. A modified equivalent circuit model of the p-i-n diode is proposed to reduce the simulation error and improve the design accuracy. By controlling the bias voltage of the p-i-n diodes, two completely different functions are realized. At the function of dual-polarized shielding, the shielding bandwidth is 2–18 GHz, and the transmission bandwidth is 8.2–10.5 GHz with a fractional bandwidth of 24.6% at the function of dual-polarized transmission. A prototype has been fabricated and measured, and the measurement results are in good agreement with the simulation results, indicating that the AFSSs has good polarization stability for X-band radar applications.