Study Of Metamaterials And Phased Array Antennas Based On Electromagnetic Bandgap (EBG) Structures

Presently, new artificial electromagnetic materials, such as metamaterials and electromagnetic bandgap (EBG) structures, become the foreland and hotspot field in Physics and Electromagnetism. The research results can be applied to many fields in the future. Thus, the investigation of the properties of the metamaterials and EBG structures needs developing and perfecting constantly in theoretical analysis, numerical simulations and actual applications. In this thesis, the guided modes in guiding structures containing non-dispersive and dispersive metamaterials are discussed, the negative refraction at the interface associated with anisotropic metamaterials cut along nonprincipal axes and biaxially anisotropic gyrotropic media is investigated, and a blind spot analysis is carried out in EBG waveguide end-slot phased array antennas by using the method of moments (MoM). The work of the author is mainly focused on:1. The guided modes in a slab waveguide of non-dispersive metamaterial are investigated in detail. The guidance conditions of modes with both real and imaginary transverse wave numbers in an isotropic metamaterial slab are obtained. The odd and even mode properties for guided TE waves are discussed, and besides, the existence of guided modes with imaginary transverse wave numbers for different medium parameters is analyzed graphically. However, the metamaterials that have been prepared successfully in experiments are actually anisotropic. Thus, a grounded slab waveguide of uniaxially anisotropic metamaterial is constructed. In terms of the different sign combinations of the permittivity and permeability tensor components, the mode properties are discussed in different cases.2. The guidance of waves at the interface associated with an isotropic dispersive metamaterial and in a slab waveguide of uniaxially anisotropic dispersive metamaterial is discussed. The results show that the mode properties of the two guiding structures are closely dependent on the operating frequency of the dispersive metamaterial.3. The characteristics of reflection and refraction of electromagnetic waves at the interface between an isotropic regular media and an anisotropic metamaterial cut along nonprincipal axes are thoroughly investigated. In terms of the different sign combinations of the tensor components along principal axes, the anisotropic media is divided into four categories. The existence conditions of negative refraction and the influence of the rotation angle on the total reflection and total transmission phenomenon are discussed for each case. When the rotation angle is equal to 0o or 90o , this anisotropic media can be reduced to general anisotropic media, which makes the conclusions in this paper more general.4. A biaxially anisotropic gyrotropic media, in which the negative refraction may occur, is discussed, and the use of such a medium offers flexibility in design and ease of fabrication. The propagation characteristics of TE-polarized waves at the interface between an isotropic regular medium and a biaxially anisotropic gyrotropic medium are analyzed. The effect of the different medium parameters on the total reflection, normally incident total transmission and negative refraction is discussed in different cases. Numerical results are given to validate the theoretical analysis.5. A blind spot analysis is carried out in rectangular waveguide end-slot phased arrays of a triangular arrangement by using the MoM. The parameters associated with blind effect, such as the reflection coefficient of the center element, the active element pattern and the coupling coefficient are all computed. The sufficient condition of the unity of the active element pattern and reflection coefficient in describing blind effect is proved, which is the array should be equal scale excited and the phase of the reflection coefficient be zero (resonance). The conclusions will be helpful in effectively suppressing the scan blind spots by using EBG.