Study On Symmetry And Computational Method Of Atrificial Electromagnetic Material

Artificial electromagnetic material has become the hot research interest due to itscharacteristics that the natural materials do not have. Its potential appliaction will beextended to the field of microwave, optics, and acoustics. In this dissertation, grouptheory is utilized to analyze the symmetry of the artifical electromagnetic materials.And, the role of the symmetry in the analysis of the artifical electromagnetic materialsis emphasized. The work of the author is mainly focused on:1. The relationship between the irreducible Brillouin zone(IBZ) and the pointgroup of two-dimensional electomagnetic bandgap structure is proposed by theanalysis of the basis of EBG structure. And the relationship is furtherly applied to theanalysis of diffraction energy chart of some typical EBG structure.2.The analysis of non-full symmetry EBG structure, which can be caused by thechange of via, patch, and array, in the typical mushroom-type EBG structure, is made.The surface wave oppression bandgap and the in-phase reflection bandgap are obtainedby the unit model of infinite periods. The variation of the surface wave oppressionbandgap and the in-phase reflection bandgap with the symmetry of the EBG stucture isproposed, of which it is noticeable that the offset and slant of the via can lead to thedual in-phase reflection bandgap when the incident wave is polarized in a certaindirection.3. The application of the non-holosymmetic EBG structure on the microstripantenna is studied. It can effectively reduce the mutual coupling of two circle antennasto place the non-holosymmetric EBG structure between them. In order to maintain theresonant frequency, the dielectric superstrate is integrated, with the EBG structure on it.The simulation result shows that the modified structure can also reduce the mutualcoupling of two antennas, with the resonant frequency unchanged. The main purposeof this study is to show the requirement of symmetry in the design of EBG structurecan be degraded, and non-holosymmetric EBG structure can effectively work under thecertain condition.4. The effect of the symmetry on the analysis of the basic current mode of DNGstructure is studied by reseaching the-type structure, the typical DNG structure. Thetwo basic current mode is obtained by examing the point group symmety of-typestructure and its irreducible representation and character, and then the relationshipbetween the current mode and the polarization of the incident external electric field. And the constitutive relation for-type structure, the bianisotropic material, is givenqualitatively.5. The higher-order MoM with NURBS is employed to analyze the scatteringfield of the photonic crystal composed of perfect electric conductor cylinders.