Design of a Wideband Absorption Frequency Selective Rasorber Based on Double Lossy Layers

Frequency selective rasorber (FSR) is a special absorber with a transmission window. Due to the characteristics of in-band transmission and out-of-band absorption, FSR is considered as a candidate for stealth radome. By breaking through the technical barrier of traditional FSR transmission windows design, we implement a double lossy layers FSR for the first time in public reports. The FSR is configured by cascading two lossy layers above a lossless layer with two air spaces to separate them. It has two independent absorption bands, which are provided by their lossy layers, respectively. Therefore, it has a broader bandwidth and more stable absorption characteristics. We adopted the equivalent circuit model (ECM), surface current distribution, and loss distribution to comprehend the physical mechanism of the FSR. We fabricated and measured the FSR prototypes to validate the proposed design. The simulated results show that the transmission is -0.78 dB at 6.3 GHz, and the -10 dB reflection is 2.5-14.6 GHz. The measured results achieve a significant agreement with the simulated results. Under the universal guideline, new FSR could do better in terms of absorption bandwidth and scattering stability. It has significance to the engineering progress of FSR acting as a stealth radome in antenna system.