Research On Design Of Non-conformal Invisible Cloak With Arbitrary Axis Ratio

Metamaterial with special physical properties which conventional materials do not have are made up of the artificial composite materials.Its main characteristics are negative permittivity and negative permeability.The method of coordinate transformation provides us a new way to manipulate electromagnetic wave and reshape its propagation in a controlled manner.Based on the coordinate transformation,the invisible cloak can change the material parameters and make the light smoothly bypass the invisible region along the intended path,thereby achieving perfectly invisible.Due to these features,scientists have made breakthroughs in the research of military defense and acoustics.This paper studies on the arbitrarily non-conformal invisible cloak based on coordinate transformation,and mainly research contents include:1.In this paper,based on the metamaterial properties and the coordinate transformation theory,the definition and electromagnetic properties of metamaterials are introduced in detail.Deeply analyze the coordinate transformation theory in Cartesian coordinate systems and orthogonal coordinate systems.These characteristics and principles lay the theoretical foundation for the below design and research of the invisible cloak.2.Starting from the simple two-dimensional conformal elliptical invisible cloak,based on the above theory,the derivation of the two-dimensional non-conformal elliptical invisibility cloak general constitutive tensors is deduced.Using the finite-element software to simulate different types of invisible cloak and corresponding results were obtained.The validity of the derivation of the two-dimensional non-conformal elliptical invisibility cloak is confirmed.3.From the two-dimensional to the three-dimensional space,up to now,most of the studies were focused on the invisible cloak with conformal inner and outer boundaries.However,in practical applications,simple three-dimensional structures cannot meet the requirements,such as the nose and fuselage parts of aircraft,and missiles.Therefore,it is great necessity to study the three-dimensional non-conformal ellipsoidal cloak both in terms of theory and actual demand.Based on the idea of linear coordinate transformation,arbitrarily three-dimensional non-conformal ellipsoidal invisible cloak were proposed and designed in this work,that is,the ellipsoid inner and outer boundaries have different axial ratios on the x,y,and z axes.The general formulations of the inhomogeneous and anisotropic constitutive tensors of the cloak were derived for the non-conformal ellipsoidal cloak.The results of full-wave simulations by using finite-element software are confirmed the validity of the constitutive parameter tensor expressions,for different types of electromagnetic wave under the irradiation of different geometric parameters of non-conformal ellipsoidal cloak.And deeply research on the electromagnetic properties and loss.This work is more flexible and more suitable for the practical application,and also provides a feasible way to fabricate invisible cloak in the future.