Broadband Tunability of Polarization-Insensitive Absorber Based on Frequency Selective Surface

An innovative tunable and polarization-insensitive 1.6–8 GHz frequency selective surface (FSS) absorber was investigated in this study. The proposed FSS, which is in 4-axial symmetrical form, includes a novel array of PIN diodes with biasing lines including inductors. A gradually reduced equivalent resistor of PIN diodes can be achieved with increasing DC voltage, which characterizes tunable, multi-resonance absorption peaks. Via this simplified design, small value resistor and equivalent capacitance of the gap between patterns can improve the absorber’s performance in low frequencies; an active tunable absorber can be realized in a broad frequency range by employing adjustable devices. Changing the working state of the PIN diode allows the user to obtain strong absorption within the desired frequency. We analyzed the performance of the proposed absorber and found that it indeed shows very favorable absorption performance in low frequency (−10 dB in 1.6−4.3 GHz) and wideband (−8 dB in 4.3−5.4 GHz and −10 dB in 5.4−8.0 GHz) conditions. Calculation and simulation results also illustrated that the absorber is entirely polarization-insensitive.