Evaluation Of Scattering From Electrically Large And Complex PEC Target Coated With Anisotropic Material And Its Software Realization

The evaluation of the scattering from an electrically large and complex target coated with anisotropic material is of significant due to its wide applications in military field, such as electronic countermeasures, stealth technology, etc. The coating of anisotropic material on the surface of a target can not only absorb the incident waves, but also redistribute the scattering energy by controlling the principal axes of anisotropic material to reduce radar cross section (RCS) of the target. This paper focuses on the evaluation of the scattering from electrically large and complex perfectly electric conduct (PEC) target coated with anisotropic material in high-frequency technique and its software realization. Two novel approaches, that is, multimode rays (MMR) and spectral domain method (SDM) are proposed in this paper to calculate the scattered field from an infinite PEC plate coated with a homogenous anisotropic layer. The scattered field is applied to deduce the equivalent electromagnetic currents on the flat triangle facets which are used to discretize the surface of the complex target, and the scattering from the coated target is evaluated by physical optics (PO) solution derived from the equivalent electromagnetic currents. The derivation of the equivalent currents is the difficulty, as well as the primary innovation in this paper.The main content of this paper includes the following parts:1) The MMR solution of the scattering from an infinite PEC plate coated with an anisotropic layer. The optic rays are employed to trace the waves propagating in the air and anisotropic layer. According to the paths of the reflected fields with different modes, the total reflected field can be expanded in terms of a geometric series. Each series is determined by the boundary conditions at the top and bottom interfaces.2) The asymptotic solution of the scattering form an infinite PEC plate coated with a uniaxial or biaxial electric anisotropic medium (UEAM or BEAM) layer. Firstly, the discussion of Maxwell equations in UEAM or BEAM is executed to derive the formulas of the plane wave spectrum. The formulas are employed to represent the electromagnetic fields in the air and anisotropic layer. Then the spectral formula of the scattered field from the coated plate is determined by employing the boundary conditions in the spectral domain at the top and bottom interfaces. Lastly, the spectral integral is handled by the saddle point, and the asymptotic solution of the scattering is the specular reflection of the coated plate in physics.3) The software realization of the evaluation on the scattering from electrically large and complex PEC target coated with an anisotropic layer. The surface of the complex target is discretized using flat triangle facets. Using the Z-Buffer method in OpenGL technique, the facets illuminated by an incident wave are picked out. The equivalent electromagnetic currents on each illuminated facet are derived based on the proposed MMR and SDM, then the PO scattered field of the coated target can be calculated by the currents. The evaluation approach is validated, and the RCSs of several canonical and complex target coated with anisotropic material are evaluated and explained for the first time in this paper.4) The RCS reduction design of an electrically large and complex target coated with anisotropic layer. The surface of the studied target is divided into several regions, and the surface impedance of each region is the optimation parameters. The high-frequency scattering from a surface impedance target is set as the forward algorithm, and the standard genetic algorithm is adopted as the optimization algorithm. Based on the relationship between the reflection matrix of the coated plate and the optimized surface impedance, the parameters of the coating anisotropic layer are extracted.