Water-based Reconfigurable Frequency Selective Rasorber with Thermally Tunable Absorption Band

In this paper, a novel water-based reconfigurable frequency selective rasorber (FSR) at microwave band is proposed, which has a thermally tunable absorption band above the transmission band. By breaking through the technical barriers of traditional FSR reconfigurable feature design, we have achieved water-based FSR for the first time in a public report. The water-based FSR consists of a bandpass frequency selective surface (FSS) and a 3D-printed container. The water substrate is filled into the sealed space constructed by the above two structures. Numerical results show that the FSR can achieve absorption with high absorptivity from 8.3 to 15.2 GHz, and obtain a transmission band of 5.2 to 7.0 GHz. The minimum insertion loss of the transmission band reaches 0.72 dB at 6.14 GHz. In addition, the FSR has the reconfigurable characteristics of absorbing or reflecting electromagnetic waves by filling with water or not. Due to the Debye model of water, the absorption band can be adjusted by water temperature, while the passband remains stable. At last, the designed FSR based on water has been fabricated, and experimental results are presented to demonstrate the validity of the proposed structure.