An ultra-wideband phase gradient metasurface for anomalous reflection and RCS reduction

In this work, an ultra-wideband phase gradient metasurface (PGM) based on a novel polarization conversion metasurface (PCM) is proposed for anomalous reflection and radar cross section (RCS) reduction. Because the PCM can achieve ultra-wideband circular-polarization(CP)-maintaining reflection in the frequency band from 8.9 to 34.9 GHz, through the rotation of its unit cell structure, the reflection phase in the ultra-wide frequency band can be adjusted at will by the Pancharatnam–Berry (P-B) phase only generated in its co-polarized reflection coefficient under CP incidence. Thus, a PGM is proposed by gradually rotating each unit-cell structure of the PCM, and the proposed PGM can realize ultra-wideband anomalous reflection to reduce the specular RCS. In addition, when the PGM is divided into multiple square elements with different phase gradients, it can work as a diffusion metasurface to reduce the specular RCS and maximum bistatic RCS simultaneously. The simulated results show that the PGM can achieve more than 10 dB specular RCS reduction in the frequency band from 10.0 to 33.5 GHz, but its maximum bistatic RCS is very large; however, when it is changed as a diffusion metasurface, it can reduce not only the specular RCS but also the maximum bistatic RCS in the ultra-wide frequency band of 10.1–34.3 GHz with a relative band-width of 109.5%; in addition, when the incident angle is increased to 45°, the RCS reduction performance of the diffusion metasurface can still be kept well. Finally, an effective experimental verification is carried out for the diffusion metasurface.