A Great Wall-Inspired, Water-Based, Switchable Frequency-Selective Rasorber With Polarization Selectivity: Multifunctional, polarization selective, independent working states

A water-based, switchable frequency-selective rasorber (FSR) with polarization selectivity using Great Wall structures is presented in this article. The proposed structure includes a container comprising horizontal and vertical channels enabling a dividable injection of water and a cross-gap frequency-selective surface (FSS). The novelty of the design lies in its switchability among three different operating states by injecting water into different water channels. When the horizontal channel is filled with water and there is no water in the vertical channel, this structure can be used as an FSR with single-polarization selectivity. The FSR with a −10-dB absorption band from 6.8 to 18.8 GHz allows only certain polarized electromagnetic (EM) waves to pass at 3.1 GHz with an insertion loss of −0.78 dB, while another polarized EM wave cannot pass. When the two channels are filled with water, the structure acts as an absorber in high frequency in which any polarized EM wave cannot be transmitted. Furthermore, the original transmission frequency band in low frequency is switched to the reflection frequency band. Besides, a reconfigurable, water-based FSR automatic control system is built to achieve state switching and temperature constancy of the water within the container. Ultimately, a prototype of the presented design is fabricated, simulated, and measured to verify feasibility. This work can be combined with an antenna to achieve out-of-band backward radar cross-section reduction.