Ultra-wideband and polarization-independent RCS reduction based on polarization conversion metasurface

In this work, an ultra-wideband polarization conversion metasurface (PCM) is proposed. Because it is an anisotropic structure with a pair of mutually perpendicular symmetric axes u and v, and the phase difference between the reflection coefficients under u- and v-polarized incidences is close to 180° in an ultra-wide frequency range from 9.5 to 29.5 GHz, it can realize ultra-wideband circular polarization (CP) maintaining reflection and make its co-polarized reflection coefficient under CP incidence close to 1.0 in the ultra-wide band 9.2–29.7 GHz. In addition, for any metasurface, when its unit cell structure is rotated by an angle ψ, almost ±2ψPancharatnam-Berry (PB) phase will be generated in co-polarized reflection coefficient under CP incidence. Thus, based on the proposed PCM, an ultra-wideband Pancharatnam-Berry (PB) 2-dit coding metasurface is conveniently proposed. The simulation and experimental results show that the coding metasurface can achieve more than 10 dB radar cross section (RCS) reduction under normal incidence with arbitrary polarizations in the ultra-wide frequency band 8.7–29.3 GHz with a relative bandwidth of 108.4%, in addition, when the incident angle is increased to 30°, the RCS reduction performance can be kept well, which shows that the proposed coding metasurface has good stealth performance under the detection of airborne radar, fire control radar and imaging radar working in X, Ku, and K bands, it is very practical.