Study On Electromagnetic Characteristics Of Microwave Photonic Crystals

Microwave photonic crystals, also referred as electromagnetic bandgap(EBG) materials, are periodic structures characterized by the existence of frequency bandgaps. The dissertation focuses on the analytical methods of EBG structures. In this dissertation, the electromagnetic performances of a wide range of EBG materials have been numerically simulated. The bandgap characteristics of EBG materials with different geometries and parameters have been studied to obtain the intrinsic relationship of the bandgaps and the diversified parameters, and the results would provide instructions for designing EBG materials.The method of lines (MoL) is used as the main numerical tool, and the analyzed EBG materials are include the planar EBG constructed in the micro-strip structures as planar layered structures, the two-dimensional EBG made of metallic rods, the high-impedance ground plane (HIGP) structure, the two- and three-dimensional dielectric EBG, and various kinds of frequency selective surfaces (FSS). The primary work is as follows:(1) In the planar EBG (containing the general ones and the uniplane compact EBG (UC-PBG)) in which the unit cell consists a metallic patch with various geometries, the bandgap characteristics have been efficiently analyzed, and the effects of different geometries and structure parameters on the bandgaps have been investigated. A novel UC-PBG, which displays a lower bandgap compared with the conventional UC-PBG, is proposed, and the effect of the new structure is proved by both numerical results and experimental data. The computational model of the planar EBG containing uniaxial anisotropic media is established using MoL. In addition, the model of the planar EBG containing the both electrically and magnetically anisotropic media is also established using MoL. Taking the UC-PBG as regarded, the effect of the anisotropic media on the bandgap characteristics is studied.(2) In the HIGP structure, according to the effective medium model, the formation of surface wave bandgap and in-phase characteristics are firstly analyzed qualitatively starting from the generation of surface wave. Then, a new full-wave analytical model is established by the use of MoL. Using the model, the surface wave bandgaps and the reflection phases of several kinds of HIGP structures, in included one with anisotropic substrates, are efficiently computed. A novel HIGP with a more compact size is proposed, which exhibits surface wave bandgaps with lattice constant far smaller than the relevant wavelength.(3) In the dielectric EBG, several efficient numerical analyzing models are established by the use of MoL, and detailed studies have been done on the bandgap characteristics of the two-dimensional dielectric EBG, three-dimensional dielectric EBG, and the dielectric EBG containing anisotropic media. The dependence of the bandgap positions on the geometric and material parameters are presented, which would supply references to the dielectric EBG design. Several novel dielectric EBGs are proposed and analyzed, in a kind of two-dimensional dielectric EBG, the overlap of TE bandgaps and TM bandgaps is achieved by using anisotropic media.(4) In the FSS, firstly, efficient analytics are done on several structures by the use of MoL, including the monolayered FSS with one patch or aperture as unit cell, the multilayer FSS using aperture coupled patches, and the one- or two-dimensional dielectric FSS. Especially, a kind of FSS structures which contain conductive layer with a thickness has been considered. Then, the FSS containing uniaxial anisotropic media is also analyzed using MoL. Afterwards, a full-wave analysis of FSS supported by both electrically and magnetically anisotropic substrate is detailed basing on Galerkin's method applied in the spectral domain. Numerical results exhibit the influence of the electrical and magnetic anisotropy on the electromagnetic characteristics of FSS.