Two-Dimensional Efficient Broadband Retrodirective Metasurface

This communication presents a novel 2-D broadband retrodirective metasurface. First, a phase-gradient metasurface composed of two crossed arrays of striplines mounted on both sides of a substrate, an insulation space, and a ground plane is implemented to achieve 2-D retrodirective characteristics at a specific angle by precisely tuning the dimensions of its supercells. Second, unlike existing designs, the effects of the distance between the striplines and the ground plane on the performance of the retrodirective metasurface are investigated to broaden the bandwidth of retroreflection. Theoretical studies, full-wave simulations, and experimental results are presented to evaluate the scattering properties of the three types of 2-D retrodirective metasurface corresponding to the three retrodirected angles of -20°, -30°, and -40°. The fractional 3 dB bandwidths of the retroreflections are improved depending on the specific values of h and the incident angle. The results show a good agreement that the retrodirective angles for the incident waves along the x- and y-directions can be controlled independently and simultaneously. The measured radar cross section (RCS) results show a power efficiency of more than 94% in both directions at the retrodirected angles of -20°, -30°, and -40° at 5.8 GHz.