Thermally Tunable Water-based Frequency Selective Rasorber With Transparent Window

In this paper, a water-based frequency selective rasorber (FSR) with a transparent window at microwave band is proposed, which can realize a broadband absorption behind the transmission band. The FSR adopts a combination of a frequency selective surface (FSS) and a water-substrate, where the water is placed in a resin container to maintain its shape. The numerical simulation results show that the FSR can achieve broadband absorption with the efficiency more than 90% from 8.9 to 14.9 GHz and have a transmission band in the frequency range of 5 GHz-6.6 GHz, wherein the minimum insertion loss of 1.1 dB at 5.8 GHz. The FSR shows its good transmission--absorption performance under different angles of incidence wave. According to the dispersion characteristics of water, the FSR exhibits a well thermally tunable with its absorption performance for the temperature range from 0 to 100°C.