An Ultra-Wideband Lossy Polarization Conversion Metasurface for RCS Reduction

This paper proposes a lossy reflective circular polarization conversion metasurface (PCM), which can achieve circular polarized (CP)-maintaining reflection and absorption. In this way, the magnitude of the cross-polarization reflection coefficient of the PCM under CP incidence can be kept at less than -10 dB in the frequency range of 6.7–40.9 GHz. In addition, the phase of its co-polarized reflection coefficients can be changed freely by the Pancharatnam-Berry phase generated by rotating its unit cell structure. When the unit cell structure is rotated by 0°, 45°, 90°, or 135°, the lossy PCM can be used as one of the four types of coding elements for a 2-bit absorptive coding metasurface (ACM). Thus, based on the lossy PCM, this paper also proposes an ultra-wideband 2-bit ACM. The simulation and experimental results show that the proposed ACM can achieve effective radar cross section reduction under normal incidence in the ultra-wideband frequency band from 6.8 to 41.4 GHz with a relative bandwidth of 143.6%. Moreover, it has the advantages of polarization insensitivity and wide incident angle.