Multiangle retrodirective cascaded metasurface

In this paper, a cascaded retrodirective metasurface is designed and demonstrated to operate simultaneously at a wide range of incident angles from $−30°$ to $−10°$ and 10$°$ to 30$°$⁠. It is based on the design of several retrodirective super-cells following the generalized Snell’s law of reflection, where each super-cell is designed to redirect an incoming wave back in the same direction with high efficiency. This metasurface is a very good candidate as a retroreflector for radar cross-section (RCS) enhancement of targets with poor backscattering. Retrodirective topologies have been a subject of interest, and several engineered topologies exist, such as the corner dihedral. Despite their good performances at a range of incident angles, their 3-dimensional bulky structure makes them hard to implement for different applications and they do not address extreme incident angles. The metasurface proposed can be a complementary solution to existing topologies for addressing extreme oblique incident angles while being more compact due to its two-dimensional subwavelength structure design. The monostatic radar cross-section (RCS) performance of the designed metasurface of dimensions $8.163×56.23$ cm$2$ has been compared to that of a conventional corner dihedral of dimensions $8×15.5×7.75$ cm$3$⁠, and a gain of up to 50 dB of monostatic radar cross section (RCS) in the ranges $−30°$ to $−20°$ and 20$°$ to 30$°$ was obtained. Comparable performances are observed in the ranges $−20°$ to $−10°$ and 10$°$ to 20$°$ between the designed metasurface and the corner dihedral. Experimental results are shown to be in good agreement with simulation results.