FPGA-Controlled Dual-Band Multifunctional Active Frequency Selective Surface

This letter proposes a 4-bit multifunctional active frequency selective surface (AFSS) whose structure is made up of two metallic layers arranged on both sides of a 1.6 mm thick FR-4 substrate. The binary combination of the four control bits, provided by the incorporated FPGA platform, determines the state of the embedded PIN diodes and yields seven independent functional states. The presented structure offers dual-band characteristics (2.4 and 5 GHz WLAN) with polarization selection (TE/TM) and electromagnetic switching (transmission and shielding) capability. No additional feeder lines are considered to alleviate the structure's complexity and diminish the negative impact of the feeding network. As an ingenious design, the elements of the AFSS structure are employed as a part of the bias lines of the PIN diodes. An equivalent circuit model is accompanied to provide a deeper physical insight into the proposed structure. The proposed AFSS shows high angular stability up to 45 degrees. A prototype consisting of 12 x 12 unit cells is fabricated and measured for different binary states at normal and oblique incidence to verify the proposed AFSS's performance experimentally. An excellent agreement between the experimental and simulation results confirms the functionality of the designed structure.