Research On The Electromagnetic Characters And Applications Of Metamaterial

Metamaterials with the extraordinary physical properties which nature materials donot have are made up of the equivalent uniform artificial composite structures orcomposite materials. The emergence of Metamaterials greatly expands the achievablemedia space, its unique electromagnetic properties make it possess a huge potential incivilian areas and military fields.This thesis studied the effective medium theory of metamaterials, did somemeaningful exploration in the applications of electromagnetic stealth, electromagneticabsorbing and antenna using metamaterials. We got a series of valuable results. Themain tasks are the following:1. Analyzed the the monodromy and thickness resonance problem of NRW method byan ordinary medium, studied the constitutive parameters of typical metamaterialunit in different polarized electromagnetic wave incident conditions.2. An approach to design an invisible cloak with controlled constitutive parametersand arbitrary shaped boundaries by Helmholtz equation was presented. We got thevalue of constitutive parameters of invisibility cloak with spherical border andpointed out this analytical solution will alter with a parameter ofHelmholtz equation. Studied the numerical constitutive parameters of arbitrarilyshaped invisibility cloak by FEM simulation, gave the electromagnetic fielddistribution in the cloak when the numerical solution change, showed that themethod can be realized and concluded that either the parameter k inHelmholtz equation is a real number or imaginary can create the correspondingInvisibility Cloak. In addition, a two-dimensional invisible cloak performancetesting device is presented.3. Analyzed the absorbing mechanism of the resistive loaded HIS metamaterialabsorber by single-port network model. We presented an important parameterwhich is the minimum Y value makes the reflection coefficient Γ less than-10dB: Ymin∣Γ<-10. Got the methods make metamaterial absorber have widerabsorbing bandwidth and flatter absorbing curves, full-wave simulation verified thecorrectness of the analysis.4. The traditional metamaterial absorber does not have the ability that letelectromagnetic wave overpass, a novel broadband metamaterial absorber with atransparent window is presented. We used dual-port network to establish the modelof this absorber, simulation and experimental results showed the correctness of themodel and verified the absorber has an absorbing bandwidthof5.5GHz~13GHz and a wave-transparent window at21GHz.5. We adopted I-shaped metamaterial to improve the performance of airborne Yagi antenna. Analyzed the changes of the constitutive parameters caused by differentfrequency, pointed out that I-shaped metamaterials can be equivalent to a electricalnegative materials in a particular polarization conditions. We studied the affect tothe constitutive parameters by different size of I-shaped metamaterials, got the lawof the changes of bandwidth and resonant frequency by altering structure size. Bythe finite element simulation of the interaction of a uniform single negativemetamaterials with a Yagi antenna, we presented how the constitutive parametersand loading position affect the antenna near-field radiation characteristics.Compared the case of metal sheet and dielectric plate loaded Yagi antenna, gave theadvantages of metamaterials loaded method. Simulated the VSWR and far-fieldpattern of metamaterial loaded Yagi antenna by CST, got the suitable loadingposition which can improve VSWR and pattern. Measured the performance of areal I-shaped metamaterial loading Yagi antenna, the results showed that the gainhas an average increase of1.5dB and the back lobe has an average decrease of4dBafter metamaterial loading.