Research On Structures And Applications Of Nonresonant Metamaterial In Microwave Band

Metamaterial is one of the hot topics in today's electromagnetics. Its realizationand application have widely attracted people's attentions, for its electromagneticresponse characters are unavailable in conventional materials. Great progress has beenmade on the theory, fabrication and application of resonant metamaterial up to now.However, its inherent vices, such as high dispersion and high loss, limit its applicationin engineering, and bottleneck its development. In view of the existing problems of theresonant metamaterial, this thesis is bent on the researches of structures andapplications of nonresonant etamaterial in microwave band.In the aspect of nonresonant metamaterial structures, constructions and responsesto incident electromagnetic waves have mainly been studied. First of all, according tothe physical significance of permittivity and permeability, models of nonresonantelectric response and nonresonant magnetic response are built respectively. Calculatingformulas of the effective constitutive parameters of these two models are inferred,which are validated by numerical computation. Characters and influencing factors of theeffective constitutive parameters are studied. Then nonresonant metamaterial structuresare given, and the loss and bandwidth properties of the structures are analyzed. It'sfound that these metamaterials have the advantage of broadband, low loss and simpleconstruction.Nonresonant metamaterials break through resonant metamaterials' bottleneck andhave great potential in application. This is suggested by the researches on theapplications of nonresonant metamaterials in this thesis. First, a gradient refractiveindex lens is designed and fabricated using nonresonant metamaterials. The impedencegradient technology is adopted to decrease the microwave reflectivity. Experimentalresults suggeste that the lens can increase the gain of a horn in wide band. To meet therequirements of antennas, design methods of the shaped gradient index lens and nearfield gradient index lens are given, which can increase the gradient index lens'sapplication scope. Then, base on the approach of optics transformation, electromagneticbeam bends are designed. The resulting metamaterials are inhomogenous and anisotopic.The corresponding parameter-reduced metamaterials are realized using the nonresonant metamaterial structures, which work at an ultra broad bandwidth. The experimental andfull-wave simulated results validated that the electromagnetic waves have been bent tothe designed direction.