Physical optics approximation of electromagnetic field scattered from large PEC objects covered with chiral metamaterials

Abstract

Electromagnetic scattering analysis from conducting objects comparable in size with the incident wavelength, using exact numerical approaches, always suffers from high computational complexity, especially when covered with composite penetrable materials. In this paper the asymptotic method of the physical optics (PO) is developed to predict the scattering patterns from conducting objects coated by chiral metamaterials (CMMs) as an absorber. In first stage, the backward ray-tracing is used to determine the lit region on the outer surface of the objects represented by flat elementary facets. Simple closed-form expressions are derived for the co- and cross-polarized reflection coefficients from a metal-backed CMM layer to approximate the equivalent currents on lit facets in terms of the geometrical-optics fields. Then, for stealth applications, a CMM layer with appropriate electromagnetic properties is suggested with reflected power lower than −20 dB in a wide aspect angle of incident ray from 0 to 57 degrees. Finally, the scattering patterns are calculated via the PO approximation and the equivalent currents. In order to check the accuracy of the proposed solutions, the simulation results of several objects will be compared with the experimental data and the results of the exact Mie theory and method of moment (MoM).