Design of Quasi Crystal Based Broadband GHz Metasurface

Abstract

In this thesis, quasi-crystal metasurface based-on super-cell technique is designed to realize multiple operations at microwave frequencies. In this technique, distinct sized anisotropic patches are placed in one super cell to couple response of each patch operating in different frequency bands. Thus, the proposed design benefits from the individual resonant response of anisotropic patches and also from their coupled response due to periodic perturbations in the square lattice. The metasurface provides simultaneous half- and quarter-wave plate operations to transform linear to cross and linear to circular polarization conversions respectively. Such a broadband and multifunctional planar metasurface will help miniaturize the size of microwave systems whilst being ultrathin than the current reflective metasurface based polarizers. Furthermore, the physical dimensions of the super-cell are optimized to achieve high efficiency cross polarization conversion avoiding the stacking of multiple resonator layers upon each other. In addition to the main contribution discussed above, the thesis also includes a comment on a published research paper in which a metasurface structure is falsely claimed as a perfect absorber. This proclaimed anisotropic metasurface was predominantly a cross polarizer for normally incident electromagnetic wave. Therefore, the use of this asymmetric structure is limited only to the applications where cross polarization operation is desired