Design Of Amplitude And Phase Manipulation Device Based On Metasurfaces

Metamaterials are artificial structures composed of sub-wavelength inclusions that exhibit novel electromagnetic properties. Its two-dimensional (2D) form, called the metasurface, provides powerful solutions to overcome the lossy property and bulk size of metamaterials. This thesis focuses on the study of manipulating the amplitude and phase of electromagnetic (EM) waves using metasurface, which has been proved to be feasible by theoretical analyses and numerical simulations. The main contributions and contents of this thesis are listed as follows:(1) Two general theories are used to analyze and design metasurface devices. The first technique is based on Huygen’s theory. Surface magnetic impedance and electric admittance of the designed metasurface are first obtained with the incident and transmitted field distributions. Then the corresponding structure are built and optimized with numerical simulations to exhibit the above extracted surface magnetic impedance and electric admittance. The second technique is to design anomalous refraction devices by introducing abrupt phase discontinuities on a surface according to generalized laws of reflection and refraction.(2) A novel metasurface structure, the rectangular split-ring resonator, capable of controlling the transmitted amplitude is presented based on co-simulations and genetic algorithms. The mechanism of reducing the sidelobe of antenna is analyzed. A single-layered metasurface is designed and mounted on the aperture of a rectangular horn antenna. The field distribution on the antenna’s aperture is tailored as a Gaussian distribution, and therefore the sidelobe level of radiation pattern is effectively reduced.(3) A novel unit cell of metasurface structure, formed by double-spiral rings distributed on bending and EM focusing metasurfaces, are designed based on this structure, which demonstrate the ability of metasurfaces in controlling the phase of EM waves.