Study On The Manipulation Of Scattering Properties By Metamaterials

The new tunable metamaterials of which the electromagnetic responding arecontrolled by the external drive are being widely studied owing to the feature ofitsintelligent and multifunctional. Particularly, the external drives are stronglyrelative to the operation frequency.In this thesis, we mainly focus on the control and applications of themetamaterials to the electromagnetic scatting waves. The works include two aspects:transformation of a) the scatting wave to evanescent wave and its applications inelectromagnetic absorber, b) the transmission characteristics control of the scattingwave and its applications in antenna. Besides, a study is progressed for thecharacteristic of graphene in a magnetostatic bias and its applications in circularlypolarized electromagnetic wave absorber. The main works and conclusions are listedas following:1. Utilizing the theories of the effective medium, the transform matrix, and theequivalent circuit model, we design tunable electromagnetic absorbers. Theapproach of improving the absorption performance under large incidence angle invisible is proposed. In the design of tunable absorber with the assistance ofmicrowave diodes, we analyze the influence of the metallic wires to the absorptionperformance. The results indicate that absorber exhibits the features of tunableabsorbance and tunable frequency for different polarizations after introducing themetallic wires.2. Establish a simple model of tuning the transmission characteristics ofscatting waves based on the microwave diodes. We show the connection anddifference of the positive and passive control. By utilizing the equivalent circuitmodel of metamaterials with microwave diodes, the antennas with the functions oftunable sidelobe level, and electric controlled-scanning are designed.3. Utilizing the equivalent circuit model, the complex impedance of graphenein a magnetostatic bias is derived which is used to analyze the magnetic circulardichroism of the uniform graphene based on circularly polarized electromagneticwave absorber. Then we improve the effective impedance by analyzing the magneticcircular dichroism of subwavelength perforated graphene absorber for a variablemagnetic field, and study the electromagnetic responding of the graphene and the patterns, respectively.