A. I. Semenikhin – Ph.D. (Eng.), Associate Professor of Department of Antennas and Radio Transmitting Devices,

Institute of Radio Engineering Systems and Management, Southern Federal University (Taganrog)

D. V. Semenikhina – Dr.Sc. (Eng.), Professor of Department of Antennas and Radio Transmitting Devices, Institute of Radio Engineering Systems and Management, Southern Federal University (Taganrog) E-mail: d_semenikhina@mail.ru

Yu. V. Yukhanov – Dr.Sc. (Eng.), Professor, Head of Department of Antennas and Radio Transmitting Devices, Institute of Radio Engineering Systems and Management, Southern Federal University (Taganrog) E-mail: yu_yukhanov@mail.ru

A. V. Klimov – Ph.D. (Eng.), Senior Research Scientist, Associate Professor of Department of Antennas and Radio

Transmitting Devices, Institute of Radio Engineering Systems and Management, Southern Federal University (Taganrog)

E-mail: avklimov@sfedu.ru

Reduction and control of radar cross section (RCS) can be obtained using the coatings, which consists of heterogeneous, in particular, binary modules (the "black" and "white" modules), for example checkerboard. However, scattering diagrams of checkerboard in the diagonal planes contains intense diffraction lobes. To reduce the observed level of diffraction lobes, the use in a complex of a twist effect, interference and diffraction of electromagnetic waves has been proposed. The "black" and "white" modules of checkerboard should be located non-equidistantly and have to carry out wideband twist-effect. This will provide diffuse scattering, translation energy of the scattered field on the cross-polarization and reduction in the observed values of RCS on co-polarization. This technology of wideband RCS reduction can be implemented on the basis of non-absorptive binary coating with the anisotropic impedance metasurface.

In this article we study the characteristics of the scattering by anisotropic impedance structures with non-equidistant arrangement of "black" and "white" modules. The block principle of construction of the binary coatings has been proposed, and matrix schemes of modules addressing are analyzed. They must implement a zero of backscattered field. RCS reduction of the binary coatings with checkerboard order of the anisotropic modules and coatings with block addressing of modules was compared.

The modules are based on anisotropic impedance metasurface in the form of lattice of conductive strips located between two layers of dielectric on the shield. Distribution of modules on surface was described by the matrix ||εnm||, and tensors of surface normalized impedances of "white" and "black" modules has eigen values ±i. The axis of the anisotropy of such modules should be inclined at angles 45° and 135° to the plane of incidence.

The solution of the scattering problem provides a high-frequency asymptotic representation of the polarization scattering matrix, which is expressed through matrixes of reflection coefficients from impedance modules on co- and cross-polarizations. To obtain zero backscatter on cross-polarizations, the number of "black" and "white" modules in rows and columns of the matrix must be equal. The coating of two layers of the dielectric (with thickness of 4 mm, ε = 2,61) on the shield with a binary anisotropic impedance metasurface between the layers is considered with using HFSS. The metasurface is formed as a lattice of metal strips having the width of 0,42 mm and the distance between the strips of 0,955 mm. The metasurface is characterized by two eigen reactances Xms1 = ωLms,

Xms 2 = -1/ωCms, Lms = 0,12 nH, Cms = 0,0051 pF.

When the twist-effect is absent, the diffraction lobes in bistatic scattering diagrams are occurred for checkerboard structure on co- and cross-polarizations. Twist-effect removes diffraction lobes in diagonal planes of bistatic scattering diagrams on co-polarizations for both coatings – checkerboard and with block addressing of modules, but for block addressing of modules the diffraction lobes are less also due to wave interference. On cross-polarizations, diffraction lobes appears for checkerboard structure, but for non-equidistant arrangement of modules the diffraction lobes are significantly less due to wave interference.

Monostatic RCS for non-equidistant structure with block addressing of modules is reduced in the band 8...16 GHz for co-polarizations on 15...20 dB, and for cross-polarizations more than by 35 dB. Bistatic RCS patterns of structure with block addressing of modules have no diffraction lobes for co-polarizations. The diffraction lobes on the cross-polarizations in the diagonal planes are lower on 12...29 dB relative checkerboard structure.

Thus, coatings with non-equidistant block addressing of binary modules are preferable before the structures with checkerboard order of modules, as they reduce RCS even the twist-effect is absent.

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