Low-profile and compact retroreflector enabled by a wide-angle and high-efficiency metalens

Abstract

In this paper, a low-profile metasurface retroreflector based on an ultra-thin wide-angle and high-efficiency metalens is proposed and investigated. Owing to its stable high transmission magnitude and the insensitive phase shift of the proposed meta-atoms within a continuous wide-angle range, the designed metalens can efficiently focus both normal and various oblique incident angle waves to a pre-designed curved trajectory continuously. By placing a concave metal mirror which is exactly coincide with the determined focused spots, the cascaded structure thus can realize backscattering enhancement working at a continuous wide-angle range. A prototype is also fabricated, measured and characterized and the experimental results verify that the proposed retroreflector can perform an excellent backscattering enhancement within a stable 3 dB monostatic RCS for almost ±30° angle range. Moreover, the relationship between the focusing performances of wide-angle metalens (e.g., focused spot power intensity, focusing efficiency and positions) and the backscattering enhancement of cascaded wide-angle retroreflector is established and highlighted. Besides, its excellent backscattering enhancement (the absolute RCS level and angular range) can be compared to some traditional widely-used radar retroreflectors like trihedral corner reflector or Luneburg lens reflector for the similar physical size. The proposed metalens retroreflector also posses of a noticeable working bandwidth of about 0.2 GHz within X band. The presented retroreflective device is promising to develop into a low-profile, light-weight and cost-effective wide-angle retroreflector thus enabling various applications for modern microwave engineering.