Diffusive Energy-Selective Surface With Low Backscattering

In this article, a diffusive energy-selective surface (ESS) is proposed for obtaining high-power electromagnetic (EM) protection and low backscattering at the same time. With properly designed unit cell structures, the ESS is almost transparent to an incident wave of low power, while it fully rejects the high-power incidence. Meanwhile, the ESS unit cells are endowed with different reflection phases. Therefore, when arranged in a chessboard configuration, the high-power waves rejected by the ESS are diffused into other directions resulting in a low backscattering. To demonstrate the design concept, a diffusive ESS with an operating frequency of 3 GHz is designed. A unit cell with an asymmetric structure is proposed, which provides identical transmission coefficients but opposite reflection phases on its two sides. By properly assembling the unit cell and its mirror, an ESS with low-power transmission and high-power diffusive backscattering is designed. Equivalent circuit models are constructed to analyze the unit cell and to formulate the design guidelines. Moreover, the diffusive ESS is fabricated and measured based on the free-space setup, where a good agreement is observed between the simulation and measurement. The transmission magnitude is larger than −0.5 dB and smaller than −25 dB under the low- and high-power normal incidences at the operating frequency. In addition, the backscattering of the ESS is reduced significantly in comparison with a metallic plate of the same size.