| Metamaterial refers to the artificial material, which is composed of a special unit cell arranged regularly in the subwave length scale, with unique physical properties that the natural materials do not exist. The emergence and development of metamaterials provide a new and powerful tool for researchers to tailor electromagnetic waves. This paper discusses the control of emissivity and the radiation of electromagnetic waves based on metamaterials, in which a steerable emissivity surface in the near-infrared and a reflectarray antenna working in X-band are designed. The main contents of this thesis are listed as follows:(1)An 8-fold symmetric screen geometries EBG unit cell structure with double layers is designed based on genetic algorithm. At two frequencies in the near-infrared, the metasurface composed of this unit cell can not only tailor the emissivity spectrum of TE and TM waves but also custom their emissivity spatial pattern to form a conical emissivity pattern.(2) A reflectarray antenna based on metamaterials is designed, where the unit is chosen as microwave patches with the dimensions near a quarter of wavelength. By properly optimizing the geometrical parameters, a linear phase curve with the phase range 360° is obtained. By tuning the length of two orthogonal dipole, a phase difference of 90 degrees is realized in order to convert the linear-polarized incident wave from the feed to circularly-polarized radiating wave. A compact reflectarray antenna with considerable gain and 3dB axial ratio bandwidth is designed finally. |
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