Wideband planar retro-reflective metasurfaces for backscattering enhancement under oblique incidence

In this paper, we propose the design of wideband planar retro-reflective metasurface (WRRM) that can enhance backscattering under oblique incidence. By a delicate combination of narrow-band RRMs (NRRMs), the bandwidth with backscattering enhancement can be expanded significantly. As an example, a prototype operating in the X band is demonstrated. The modified metallic square loop structure is used as the sub-cell of four NRRMs. The operating bands of the four RRMs are tailored to act as quarter structures of the WRRM. A prototype was fabricated and measured. Both the simulation and experiment results verify that the WRRM can realize good backscattering enhancement performance in 8.0–12.0 GHz under incidence of angle θ = 20.0°.