Triple-band frequency selective rasorber with dual polarization and multi-band absorption

In this paper, a triple-band dual-polarized frequency selective rasorber (FSR) with multi-band absorption performance is proposed based on the combinatorial lossy structure. The FSR is composed of a top lossy layer, a middle lossy layer and a bottom frequency selective surface (FSS), which are concentrically arranged in a nested configuration. Triple parallel inductor and capacitor (PLC) resonator, integrated circular resonator and composite square and Jerusalem slots provide basically coincident triple passbands for the top lossy layer, middle lossy layer and FSS layer around 8 GHz, 10 GHz and 12 GHz, respectively. The top lossy layer mainly achieves the absorption band below the first transmission window. The middle lossy layer is responsible for the absorption bands between and above the triple transmission windows. Finally, the combinatorial lossy structure successfully integrates the four absorption bands with fractional bandwidths of 74%, 10%, 7% and 30%, maintains the overall triple transmission window, and further expands the reflection restriction band with S11 below -10 dB from 3.4-18.4 GHz (138%). The prototype with 30 × 30 units is assembled to verify the simulated results. Furthermore, the design procedures are given in this paper, which helps in designing multiband FSRs.