Broadband RCS Reduction Using Digital Impedance Metasurfaces with 2-Bit Coding of Axes of Anisotropy and Eigen Reactances

The paper demonstrates the possibilities of broadband radar cross section (RCS) reduction of a fragment of a flat metal plate by means of a nonabsorbing thin-layer coating with a digital anisotropic metasurface (DAMS). The metasurface consists of anisotropic impedance modules of a new type. Modules differ not only of 2-bit coding of the orientation angle of the anisotropy axes, but also of coding the eigenvalues of the impedance tensor. The DAMS coding matrix is described by the binary codes 00, 01, 10, 11 and realizes a RCS reduction due to cancellation, diffuse scattering of waves and twist-effect. The MS coding matrix contains the smallest balanced 2 × 2 blocks consisting of two pairs of “antiphase” modules (for co-and cross-polarization waves). Two models of nonabsorbing meta-coating with a thickness of 3 mm with 2-bit DAMS are developed. The DAMS unit cell is characterized by two eigen reactances, which depend on the orientation of the anisotropy axes of the module. These modules provide twist effect no worse than minus 17 dB in the frequency band 10.2-20.2 GHz. Bistatic RCS patterns made it possible to estimate the levels, number and direction of propagation of intense diffraction lobes. The possibilities of the considered models of 2-bit DAMS to reduce the monostatic and bistatic RCS are compared.