Patcharatnam-Berry metasurfaces with angular orbital momentum generation and combined phase coding for wideband wide-angle RCS reduction

Abstract

The phase mechanism of a broadband wide-angle radar cross-section (RCS) reduction is examined, based on the use of non-absorbing Patcharatnam-Berry (PB) metasurfaces (MSs) with the generation of orbital angular momentum (OAM) and a combination of different phase profiles. MS unit cells contain a thin shielded single-layer substrate and meta-particles in the form of perforated rectangular patches with a coded rotation angle. The purpose of the work is to compare the scattering characteristics and scattered field cancelation efficiency for structural elements (modules) of a MS, consisting of the same number of meta-particles, but having different PB-phase profiles. A profile with an azimuthal gradient, which forms broadband scattering of vortex waves with OAM, profiles with radial and linear gradients and anomalous scattering, parabolic profiles with wide-angle scattering, and various combined phase profiles are analyzed. The purpose of the work is comparing the scattering characteristics. The MS modules scattering characteristics are studied using the HFSS (finite element method) for co-polarization and cross-polarization in the case of irradiation with a normally incident plane circular polarized wave. The simulation showed that the scattering diagrams of the co-polarized MS field in these cases have a funnel-shaped vortex character with an intense OAM minus the first order (the order of the OAM remains the same as for an MS with an azimuthal phase gradient). OAM generation significantly suppresses backscattering by co-polarization. The far-field phase in the vortex region depends not only on the azimuthal, but also on the meridional observation angles. The combination of OAM and parabolic profile increases the diffusion of broadband scattering, realizes a wider-angle scattering of the resulting field with a vortex opening angle of about 100° (at an average frequency of 14 GHz), which is important for RCS reduction.