Metasurface Based Reconfigurable Microstrip Antenna

This dissertation concentrates on reconfigurable microstrip antennas based on metasurfaces, a two-dimensional analogy of metamaterials.Metasurface is a relatively hot topic in the field of electromagnetic materials in recent years. Metasurface can be simply interpreted as a two-dimensional structure of metamaterials. Artificially arranged periodic or non-periodic structures with commonly conductive unit cell configuration can produce special electromagnetic properties. This design can theoretically achieve material structural constitutive relation of any value. Metasurface with special constitutive relation may effectively improve the performance of antenna since fundamental performances of microstrip antennas are closely related with the corresponding material constitutive relation.Four kinds of metasurface are involved in this article. Combined with microstrip antenna, two structures can achieve polarization-reconfigurable feature, which are corner-cut rectangular metasurface and willow metasurface. Two other kinds of metasurfaces are of grid and of fish scale structures. These two kinds of structure can realize frequency-reconfigurable properties.Firstly, we discuss the frequency-reconfigurable feature of microstrip antenna using metasurface in this paper. Metasurface of grid structure is proposed to achieve frequency-reconfigurable property, but the resonance frequency bandwidth of a certain angle is very narrow, about 100 MHz, and fails to meet the 1GHz bandwidth requirement. Therefore, another metasurface is proposed. This model is half-circle metal cell and periodically arranged. For a certain rotation angle of the metasurface, the antenna can reach a bandwidth of 300 MHz. Through mechanically rotating the metasurface, microstrip antenna can be implemented in the range of 4.6 GHz to 5.6 GHz(S11<–10d B), widening the bandwidth of the microstrip antenna. Reconfigurable antenna bandwidth of more than 19% is achieved, compared with 1% bandwidth of a typical microstrip antenna. Also, we adopt the scattering parameter retrieval method to illustrate how the metasurface can realize frequency-reconfiguration. Separately, we use isotropic and anisotropic media to imitate effectively the influence which metasurface exerts on the microstrip antenna. The verification results and those from real antenna configurations have good agreement.Not only that, the article has also carried on the research to study the application of metasurface on microstrip antenna which can realize polarization-reconfigurable property. Corner-cut rectangular metasurface is mentioned in the article referring to a previously proposed model. We adjust parameters so that the antenna can change polarization at a center frequency of 3.4 GHz, and impedance bandwidth reaches 26%. From 3.3 GHz to 3.5 GHz, the antenna can change from circular polarization to linear polarization and the corresponding axial ratio is less than 6 d B, which meet the requirements of circular polarization in engineering. The gain can reach 7d Bi. In order to adapt to the requirement of the frequency bandwidth of satellite communication downlink, another design of willow structure metasurface-based microstrip antenna is proposed, whose bandwidth of polarization-reconfigurable covers the scope of 3.825 GHz to 3.825 GHz, broadening the potential application of the proposed antenna.