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Planar microwave retroreflector based on a split ring resonator metasurface

Metasurfaces provide an exciting platform to control and manipulate incident electromagnetic wave both in transmission and reflection mode. Up to now, to reflect an incident wave with its origin direction (i.e. planar retroreflector) with wide angle and wide bandwidth is still difficult and challenging. In this paper, we report a reflective metasurface unit element of circular split ring resonator combined with ground metal plate sandwiched by a dielectric. The numerical simulation shows that the proposed reflective unit cell can produce a huge phase variation over 320° by changing its radius at around 15GHz. Based on the reflective metasurface, we design a planar retroreflector according to the predesigned gradient metasurface. The numerical simulations demonstrate that the proposed planar retroreflector can reflect the incident wave back to its origin direction with a large angle of at least 30°. The operation bandwidth is also notable. It is about 2GHz around the operation frequency of 15GHz. The presented studies provide a good candidate to develop wide angle and wideband planar microwave retroreflector.