A single layer and very close band spacing frequency selective surface with enhanced isolation

An ultrathin and very closely located dual-band frequency selective surface (FSS) with enhanced isolation is proposed in this letter. The unit cell consists of two typical concentric hexagon rings, with several stubs loaded on each side of the inner ring. Through the stub-loaded configuration, the mutual coupling of adjacent resonators is highly decoupled and a very close band spacing FSS with better isolation can be achieved, and the ratio of the two operating bands can be as low as 1.06. Additionally, due to the independent resonant frequencies, the band ratio can be set over a wide range, from 1.06-2.43. Furthermore, the corresponding equivalent circuit model (ECM) is developed and analyzed for better comprehension of the underlying mechanisms of the proposed FSS. The validity of the design is then checked with a prototype, and the measured results show good agreement with the simulated ones.