Research On Key Techniques And Applications Of Multi-band Electromagnetic Metamaterials

Electromagnetic Metamaterial (EMM), which cannot be found in nature andpossesses the novel electromagnetic properties, e.g. negative refraction, reversals ofboth Doppler shift and Cherenkov radiation, is a kind of artificial composed material. Ithas very important potential applications in the physical areas of includingelectromagnetics, optics, and materials, and also the engineering areas of such aswireless communications and electronic engneerings. Recently, it has excited highlyresearch interests in the world, since the first experimental realization of such EMM in2000. The realization methods of such EMM developed in recent years include thetransmission-line structure, metallic resonance structure, and full dielectric structure.Also, the Photonic Crystals can also lead to some novel electromagnetic properties asnegative refraction, and therefore it can be considered as a kind of EMM. Among theabove mentioned design methods, the metallic resonance structure has huge researchmerit due to the advantages such as simple structure, easy fabrication method, andflexibility to constructe3D realization. However, for the metallic resonance EMM, themajor drawback is that the operating bandwidth is fixed and very narrow. To deal withthe problem, researchers proposed some dual-band and multiband EMMs and integratedliquid crystal, varactor, superconductor, and MEMS as the supplementary elements intoconventional EMM to achieve the band tunable characteristics.In this dissertation, the main problem of the metallic resonance EMM is alsodiscussed by (1) designing a single metallic resonator to achieve single/dual bandswitchable EMM,(2) integrating ferrite materials into the conventional single band anddual band EMM to achieve tunable dual band and triple band EMM, respectively. Theband controllable and tunable electromagnetic absorbers and rectangular waveguideterminal based on the above designed EMM are also discussed in this dissertation. Thenovel research aspects are proposed as follows in details:1. Propose a novel kind of metallic resonator (cross-circular-loop resonator) whichhas single/dual band resoancne characteristics. By using the effective circuit method andelectromagnetic simulation method, the physical realization mechanism and thecontrolling method of single/dual band operation are researched. The fabricationtechnics and measurement method are investigated, and the transmission/reflection characteristics of the proposed EMM are analyzed. After the above investigations, weget the systemic analysis method including design, simulation and measurement, andalso achieve the band controllable EMM samples.2. The physical realization mechanism of dual band tunable EMM based on theferrite materials are researched. By using the electromagnetic simulation method, thedual band and tunable transmission/reflection charactereistics are investigated. Theeffective electromagnetic media parameters are also retrieved from the simulated scatterparameters by using retrieved method. After the above investigations, the systemicanalysis method and controlling approach are obtained. Such EMM can conquer thedisadvantages of conventional EMM such as the narrow and fixed frequency band.3. The physical realization mechanism of triple band tunable EMM based on theferrite materials are researched. By using the electromagnetic simulation method, thetriple band and tunable transmission/reflection charactereistics are investigated. Theeffective electromagnetic media parameters are also retrieved from the simulated scatterparameters by using retrieved method. After the above investigations, the systemicanalysis method and controlling approach are obtained and the operating frequencyband is further extended.4. Based on the cross-circular-loop resonator, the single/dual band controllablemetamaterial absorber is proposed. By using both numerical simulation andexperimental investigations, the fabrication and closed measurement methods areanalyzed. After the above investigations, we obtain the absorbing mechanism andcontrolling approach of such metamaterial absorber.5. The realization mechanism and simulation method of the broadband tunablemetamaterial absorber based on the ferrite materials and wire array is analyzed. Theimpedance matching and absorbing loss mechanism and also tunable controllingmethod are obtained after analyzing the above mentioned research topics. Such kind ofmetamaterial absorber can be used to enlarge the operating band effectively.6. By using the closed measurement system, some kinds of metamaterial absorbersare analyzed experimentally. The realization method of rectangular waveguide terminalbased on the EMM absorbers is also investigated in this paper.