Fig. 1. Conceptual illustration of the proposed corner reflector. The functionality of retro-reflection for RCS enhancement and absorption for RCS reduction is achieved by flipping the polarization states of RHCP and LHCP waves, respectively.

Fig. 2. (a) Topological structure of the proposed chiral meta-atom, (b) surface current distribution under the illumination of LHCP and RHCP waves, (c) co- and cross-polarization amplitudes rRR(LL) and rRL(LR) of the proposed meta-atom under normal incidence of circularly polarized waves, and (d) phase responses under the illumination of RHCP waves when the pivoting angle varies from 0° to 150° with an interval of 30°.

Fig. 3. (a) Phase distribution of the proposed planar corner reflector, (b) schematic of the arrangement of meta-atoms in the designed corner reflector, (c) 3D far-field patterns under the illumination of RHCP and LHCP waves at an incident angle of 22° at 20 GHz, (d) normalized 2D far-field patterns in the cutting-plane of φ=0°, and (e) monitored electric field of Ex-component under the incidence of RHCP and LHCP waves at 20 GHz.

Fig. 4. (a) Simulated 3D far-field patterns under normal incidence of RHCP and LHCP waves at 20 GHz, (b) monitored electric field of Ex-component under the incidence of RHCP and LHCP waves at 20 GHz, (c) normalized 2D far-field patterns under normal incidence of RHCP and LHCP waves at the cutting-plane of the xoz-plane, and (d) simulated mono-static RCS with the elevation angle ranging from −40°  to  40°.

Fig. 5. (a) Photograph of the fabricated metasurface prototype with the inset showing the meta-atoms, and (b) measured mono-static RCS under the illumination of RHCP and LHCP waves at 20 GHz. The mono-static RCS of a metallic sheet of the same size as the proposed metasurface is shown for comparison.

Fig. 6. (a) Curves of absorption and circular dichroism of the proposed N-shaped meta-atom, (b) curves of circular dichroism when the resistance increases from 40 Ω to 160 Ω, (c) co-polarization amplitudes rRR and rLL under oblique incidence from 0° to 30°, and (d) reflection curves under oblique incidence at an angle of 22°.

Fig. 7. Photograph of the experimental setup for the RCS measurement.