Applications And Analysis Of Metamaterial-based Transformation Electromagnetics Devices On Cloaking And Scattering Issues

Transformation electromagnetics has become a hotspot in the research area of electromagnetics in recent years, and its basic theory is the coordinate transformation method which is based on the form invariance of Maxwell’s equations under different coordinates. The method of coordinate transformation provides us a new way to manipulate electromagnetic wave and reshape its propagation in a controlled manner. Combined with metamaterials, several new electromagnetic devices with peculiar functions can be designed. The earliest application is the electromagnetic invisibility cloak, and then different types of transformation-electromagnetics devices with other functions are also developed and applied on different issues of antenna and scattering. As a new approach for research, coordinate transformation method shows a great potential of application in many different areas such as optics, acoustics, electromagnetics and plasma research.With the background above, the research work about metamaterial-based transformation electromagnetics devices in this dissertation can be divided into five aspects:1. Several kinds of representative electromagnetic invisibility cloaks are analysed. A few kinds of two-dimentional cloaks with arbitrary boundary shape are verified through simulations. Verifications are performed to the designed muti-layered cloak and specific media loss analysis is also made. Some new types ofanti-cloaking ways are introduced.2. The singularity problem of the electromagnetic invisibility cloak is analysed and four types of processing ways are given to deal with this singularity problem, which include parameter simplification method, gradual dimensional vary method, non-Euclidean transformation method and semi-space mapping method. Among them the first two methods are mainly studied, where an optimized parameter simplification model is obtained and the second type of method is specifically analyzed with detailed parameter diagrams and numerical simulation results to prove its validity. The work above makes some consummation to the research work on the singularity problem of electromagnetic invisibility cloaks.3. The scattering minifying and scattering rotating phenomenons in transformation electromagnetics are studied. A series of polyline coordinate transformation devices are summarized. Based on the model of the electromagnetic wave expander, the variations of each constitutive parameter extremum and its normalized distributions are analyzed in detail, and the effect of media loss on the performance of the wave expander is also studied. The parameter analysis work and the study of lossy conditions of the metamaterials gives a further discussion on the realizability of the metamaterial wave expander, and gives some suggestions for practical fabrication work. The scattering minifying functions of the wave expander are further studied through numerical simulations of the two-dimensional embedded aircraft models and the quantitative calculations of their scattering width values. A series of wave expander models with reduced parameters are proposed, among which the model with the optimized performance is fully studied. Specific simulations and quantitative calculations are performed to demonstrate the scattering characteristics of the wave rotator and the lossy conditions of the metamaterial media are also analyzed. The variation of each constitutive parameter extremum and its normalized distribution with the deflection angle of the rotator is analyzed in detail. Two composite models of rotary concentrator and rotary expander are also proposed.4. The scattering magnifying phenomenons in transformation electromagnetics are studied. Based on the models of the electromagnetic wave concentrator and the folded transformation media, the scattering magnifying functions and the military applications of these two kinds of devices are studied through the simulations of embedded stealth aircraft models and the calculations of their scattering cross sections. Each of the parameter extremums and its normalized distributions are analyzed in detail, from which an optimized design conclusion of the folded transformation media model is discovered. Then the effect of media loss on the performances of these two kinds of devices is also analyzed in detail. The parameter analysis work and the study on lossy conditions will bring guidance to the practical fabrication work. At last new models of electromagnetic wave concentrator and folded transformation media with reduced parameters are proposed and fully studied in a comparative way.5. The applications of coordinate transformation method in the improvement of the antenna shape and size issues are studied. The scattering performances of three types of planar parabolic reflectors with different focal distances are verified. The variations of each constitutive parameter extremum and the normalized distributions of the required rectangle metamaterials are further analyzed with the focus-aperture ratios of the parabolic reflectors. The study of planar hyperbola reflector is also performed with the similar method. Based on the transformation-electromagnetics devices with scattering magnifying functions, their applications in reducing the antenna size or enhancing its directivity are further studied and the lossy conditions of the media are also analyzed to fit the practical conditions.