In this article, a coding metasurface is specifically designed to switch transmission and reflection functionalities between two different frequency bands for linearly polarized waves within wide incidence angles. A metasurface consists of four metallic patterns, where the middle two structures are inserted to ensure effective performance of transmission and reflection, while the top and bottom patterns are designed based on simultaneously controlling the reflection phase for both polarization states. It has been experimentally demonstrated that the proposed metasurface can convert a transmission band into a complete reflection band (meanwhile, the reflection band is translated into a complete transmission band) by changing the incident polarization state. Highly efficient transmission and reflection characteristics have been achieved from 21.1 to 24.5 GHz as well as from 33.3 to 38.3 GHz, whereas more than 10 dB radar cross-section (RCS) reduction has also been obtained for both TE and TM modes in their respective reflection bands. The performance of the proposed metasurface is well sustained up to 40° oblique incidence. This work will help to open a new aspect in metasurfaces to manipulate the electromagnetic waves at preferable frequency bands to achieve desirable functionalities.

An ultra wideband (UWB) radar cross-section (RCS) reduction metasurface has received attention in recent years. However, the majority of the research has concentrated on the physics and design of planar surfaces, which do not meet the standards of modern aerodynamics and aesthetics. In this paper, we offer a sophisticated strategy for designing a metasurface that can conform to the shape of any object, even those of moderate curvature, and can also achieve UWB RCS reduction by combining absorption, polarization conversion, and diffusion mechanisms. Firstly, an absorbing-polarization converter is designed, composed of a square patch with a truncated diagonal strip and ring. A thin Rogers RT/Duroid 5880 dielectric substrate layer is used in the structure, which is also appropriate for conformal conditions. The substrate layer and the ground plane are separated by an air gap to enhance the polarization conversion bandwidth (PCBW). For normal incident electromagnetic (EM) waves, the PCBW ranges from 10.8 to 31.3 GHz with polarization conversion ratio (PCR) values greater than 0.9 dB. Up to a 45∘ oblique incidence angle over the aforementioned band, the PCR efficiency is well maintained. Then, the optimized coding metasurface is formed by the Pancharatnam–Berry (PB) phase, consisting of meta-atoms “0” and “1” of the same size but different orientations, to realize the concept of cross-polarization diffusion. A theoretical investigation has been performed to analyze the RCS reduction performance of planar as well as conformal cylindrical surfaces. The results show that more than 10 dB of RCS reduction is experienced over UWB (10.8–31.3 GHz) for planar metasurfaces under linearly and circularly polarized incidence waves. Furthermore, the RCS reduction for cylindrical surfaces can be achieved in a similar frequency band above 10 dB up to an angle of 90∘. It can be deduced that our proposed flexible metasurface can be used as an absorber or a polarization converter and provide broadband RCS reduction, which is essential for multi-function and conformal stealth applications.

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