TAHIRA PERVEEN, NAWAZ (2015) MODELING OF INTERACTION OF EMR WITH ROD METAMATERIALS. Doctoral thesis, Bahauddin Zakariya University, Multan.

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This thesis is devoted to the studies of the theoretical description of two component metamaterials, arrays of metal cylinders/ rods periodically immersed in a dielectric matrix. The rods comprise the magnetic material (Iron/ Ferrite / cobalt). Only circular cross section of the rods is considered in the thesis, the rods do not touch each other is another consideration. At the same time, there is no restriction on the radius of cross section of the rods. The frequency ranging between 0 to 5 GHz has only been considered in this thesis. The metamaterial media/ structures are being considered in the thesis as artificial ferrites with their own effective complex dielectric and magnetic constants. So, the presented metamaterial media/ structures in the thesis are considered as perfect crystals with their own dispersive properties studied in the given frequency range. The lattice constant of the crystal is equal to the constant of the unit cell of metamaterial under consideration. The descriptions of the considered metamaterial structures are identified with the study of properties of the effective dielectric and magnetic constants as functions of the frequency (in the GHz frequency range) of incident electromagnetic wave and the volume fraction of metal rods in the unit cell. The above characterization is the key to defining unusual material properties those are unavailable in real nature, i.e., enhancement of the effective parameters; a possibility to get negative values of the effective parameters; ultra-low values of the refractive index and negative refractive index. Throughout the thesis, we consider the initial plane electromagnetic wave that is normally incident on the flat boundaries of the unit cell. The wave has the magnetic induction vector parallel to the axes of the cylinders/ rods while the electric intensity vector is perpendicular to them.</b> The effective complex dielectric and magnetic constants have been obtained through the implementation of the Effective Medium Theory (EMT) in appropriate frequency range. These expressions of the effective constants obtained in this thesis take into account multiple effects for the case of very small value of rod volume fraction while dipole effects are taken into account for the case of large volume fraction. </b> The accuracy of the obtained mathematical models always benchmarked through a comparison with the numerical calculations obtained via the implementations of Finite-Domain Time-Difference (FDTD) method. All of the numerical experiments presented in the thesis have been carried out with the help of the free Meep FDTD software package while analytical modeling has been done using MATLAB software. </b> In this thesis, the author also considered magnetic properties of two components metamaterial medium. We used the Effective Medium Theory for two components, undiluted composites for infinite/long cylindrical metal inclusions and microwave extension of the Effective Medium Approximation for polycrystalline ferrites. The expressions for effective permeability tensors of the considered metamaterial medium have been obtained by the implementation of the above theories. The expressions of effective magnetic constant for the case of the propagation transverse to bias have been obtained as well. Simple analysis of these expressions has shown that the presented metamaterial is a Left-Hand Material with low magnetic losses. </b> Furthermore, two dimensional sandwich composite structure with cobalt/Iron inclusions is also considered. The structure of the sandwich composite composed of an infinite chain of infinitely long metal cylinders symmetrically immersed in an infinite metamaterial slab. The slabs are an infinite magneto dielectric matrix with periodically embedded infinitely long metal cylinders whose diameter is smaller than those of the chain cylinders. Evaluation of the effective parameters is realized using the reflection-transmission parameters i.e. S parameters obtained by simulation or experimental measurements and analytically evaluated at the interface reflection coefficient of the slab. Since there is an enhancement in the real parts of the complex-effective constants with low absorption in the appropriate frequency range. This is obtained in the increase in the values of the metal volume fraction in cylindrical inclusions, that's why the considered artificial material can be used for the miniaturization of and for the improvement in the directivity of the patch antennas. </b> The obtained analytical model of the composite in the thesis gives a good qualitative with the results of the numerical simulations in the case if cylinders touch each other. </b> The obtained mathematical models reveal negative values of the effective dielectric and/or magnetic constants (their real parts) in the GHz frequency range. That's why most of the models presented in this thesis are LHM. </b> Also in this thesis, the magnetic properties of meta-ferrite presented as an infinite host dielectric material (air) with periodically embedded cylindrical ferric inclusions is considered. The inclusions are saturated with a biasing external magnetic field. The direction of wave propagation is in the directions of bias. Computations have shown that the medium becomes either material with a ULI and/ or with negative values of the effective permeability. </b> Comparison of the present models with those of the literature shows worth of the work and their potential applications in technology. </b> It is important to mention that the obtained results in this thesis are in a good quantitative and qualitative agreement with the results of experimental research carried out earlier in the literature. Moreover, these results can be used for creating/ establishing the course of laboratory works while using personal computers for the students of Engineering and Sciences for example, Industrial Mathematics, Theoretical Physics, Electrical & Electronic Engineering, and Material Sciences to study the optical and transport properties of slab metamaterial structures and LHM structure in the microwave frequency range.

Item Type: Thesis (Doctoral)
Subjects: Q Science > QA Mathematics
Depositing User: Mr Sami Uddin
Date Deposited: 27 Oct 2017 04:50
Last Modified: 27 Oct 2017 04:50

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