Wideband Polarization-Insensitive Switchable FSS-based Rasorber/ Absorber/Transmitter/Reflector

This paper presents a wideband switchable frequency selective surface (FSS)-based multifunctional geometry, demonstrating electromagnetic (EM) characteristics such as absorption, transmission, reflection, and rasorber under various operating modes. The proposed geometry comprises periodic metallic patterns on two substrate layers separated by an air spacer, where lumped resistors and p-i-n diodes are strategically placed to allow independent regulation of operating states. In the OFF (layer 1)-OFF (layer 2) mode, the FSS acts as a rasorber with a transmission-absorption (T-A) response, showing an insertion loss of 2.1 dB at 2.67 GHz and wideband absorption from 4.76-6.37 GHz. In the OFF-ON mode, the structure exhibits wideband absorption from 3.25-6.05 GHz, while the ON-OFF mode provides transmission from 2.41-4.49 GHz. The ON-ON mode shows reflection (S₁₁ < -2.8 dB) over the entire band. The topology is polarization-insensitive and angularly stable across all EM operations. Finally, a 1-D array prototype is fabricated and tested using a parallel plate waveguide (PPW) setup, demonstrating the potential of the proposed switchable FSS for diverse EM applications.