Design And Characteristic Of The Tunable Electromagnetic Metamateriai

Metamaterial refers to a composite or structured material that exhibits propertiesnot found in naturally occurring materials or compounds. Electromagneticmetamaterials are constructed by embedding some material units in traditional media,and have the electromagnetic properties not included in natural media. In1968, V. G.Veselago theoretically researched the imaginary media with negative permittivity ε andnegative permeability μ simultaneously, and found a series of strange electromagneticphenomena. In2000, D. R. Smith et al. proved the existence of electromagneticmetamaterial by experiment. The electromagnetic metamaterial quickly became one ofthe international research focuses of microwave, optical, electromagnetic, and physicsresearch. However, most studies were based on the principle of D. R. Smith'sexperiment. These metamaterials had only fixed physical parameters, and had not thetunability.The research work of this dissertation is supported by the National Natural ScienceFoundation of China "The composed method and characteristic research on tunablenegative refractive index microwave materials". A tunable metamaterial is composed byincorporating periodic metallic wire array into YIG (Yttrium Iron Garnet) applied byexternal magnetic field. In-depth study was carried out for this tunable electromagneticmedium over the electromagnetic mechanism, transmission characteristic, and refractioncharacteristic. The main research activities and innovative achievements gained are asthe following:1. The effective medium theory is improved, and the tunable metamaterial'selectromagnetic mechanism is analysed more accurately. The theoretical system oftunable metamaterial composed by incorporating periodic metallic wire array intoyttrium iron garnet applied by external magnetic field is derived.2. The full-wave electromagnetic simulation program is used to simulate thepropagation and refraction features of electromagnetic wave in the composite medium,which is designed by incorporating periodic metallic wire array into yttrium iron garnetunder external electromagnetic field. Simulation results show that as long as the appropriate parameters are selected, the design method of metamaterial by embeddingin YIG with a periodic array of metal conductors will be theoretically correct andfeasible. Qualitative analysis and numerical simulation of the interaction effect between"electromagnetic field-static magnetic field-base material-metal conductors array" inthe tunable metamaterial composed by incorporating periodic metallic wire array intoyttrium iron garnet applied by external magnetic field are completed.3. A set of transfer experiment program is designed, the experimental equipment isimproved, a viable method of making the sample is found, and the experimentalverification of electromagnetic wave transmission characteristic of the tunablemetamaterial is completed. In the specific frequency band where the equivalentdielectric constant of metal conductors array is negative, by adjusting the externalmagnetic field to make the equivalent permeability of YIG simultaneously negative,double negative transmission propertie of the tunable electromagnetic medium isobserved. The transmission passband center can be regulated by the magnetic field.4. A set of refraction experiment program is designed, the experimental equipmentis improved, a viable method of making the refraction experiment sample is found, andthe experimental verification of electromagnetic wave refraction characteristic of thetunable metamaterial is completed. In the specific frequency band where the equivalentdielectric constant of array of metal conductors is negative, by adjusting the externalmagnetic field to make the equivalent permeability of yttrium iron garnetsimultaneously negative, the angle of refraction on the interface of the air and thetunable metamaterial at different frequencies is recorded, and negative refractionphenomenon of the tunable metamaterial in the microwave band is observed.