Wide-Passband Reconfigurable Frequency Selective Rasorber Design Based on Fluidity of EGaIn

In this letter, we propose a wide-passband reconfigurable frequency selective rasorber (FSR) design based on the fluidity of liquid metal. To achieve wide-passband reconfigurability, a new type of reconfigurable frequency selective surface with wide-passband elliptic filter response is introduced for the first time, whose bandpass state can be switched to a perfect reflection state by controlling the injection and the extraction of liquid metal in microchannels. Furthermore, a new resistive film loop with a minimum insertion loss of 0.23 dB is presented by loading four circular spiral resonators. Finally, the FSR can realize the reconstruction of the absorption-transmission-absorption (ATA) and absorption-reflection-absorption (ARA) modes. The simulation results show that in ATA mode, the design exhibits a wide passband with a fractional 3 dB bandwidth reaching up to 42.8%, and a passband minimum insertion loss of 0.86 dB at 13 GHz. In ARA mode, the bandwidth for return loss less than 3 dB is 12.8%. Prototypes were fabricated and measured. Compared with previous FSRs, our proposed FSR has advantages such as reconfigurable characteristics, a wide transmission band, and high-frequency selectivity.