Simultaneous Polarization Conversion and Retro-Reflection Based on Surface-Circuit Metasurfaces

A novel design based on surface-circuit metasurface (SCM) is proposed to realize polarization conversion and retro-reflection simultaneously. Unlike conventional reflective metasurfaces, the meta-atoms of the SCM consist of two parts: antennas on top surfaces and back-loaded circuits. With this configuration, the manipulation of spatial electromagnetic (EM) waves can be converted to the operation of guided waves in microwave circuits. This configuration will bring benefits like eliminating unwanted coupling effects between neighboring elements and providing a compact size for some complicated EM manipulation tasks. In this work, a back-loaded microstrip line connecting two ports of a dual-polarized patch antenna for orthogonal polarization is utilized to achieve linear-to-linear polarization conversion and the desired reflection phase delay. Retro-reflection is then realized by generating a gradient phase distribution on SCM by controlling the lengths of back-loaded circuits of meta-atoms. Finally, an
$\text{{8}} \times \text{{8}}$
SCM prototype with a thickness of 0.068
${\lambda }_{0}$
at 23.8 GHz is designed, fabricated, and measured. Both simulation and measurement results show that the SCM can simultaneously achieve high-efficient polarization conversion and retro-reflection at an incidence of −30°. It is especially useful in some applications like RF tags and point-to-point wireless communication where high retro-reflection angular selectivity is needed.