Study On Electromagnetic Wave Propagation And Scattering Characteristic Of Metamaterials

Since Smith D R et al.fabricated metamaterials whose permittivityεandpermeabilityμare negative by using Pendry J B et al.'s theoretical results for the firsttime in 2001,the study of metamaterials has become a conspicuous front field in theinternational science field.In this thesis,the electromagnetic (EM) wave propagation and scattering inmetamaterials are investigated with finite-difference time-domain (FDTD) method andMie series method.The applications of metamaterials in cloak and beam splitter et al.are discussed.The main results in the paper are as follows:1.The effects caused by disorder,cutting and rotating in transmissioncharacteristic of metamaterials are investigated in theory and experiments.Theextracted real parts of the permittivity,permeability and index of refraction for thestandard metamaterials are compared with those for disorder metamaterials.It is foundthat the disorder on the split ring resonators results in a lower left-handed transmissionand narrower pass bands.The left-handed transmission peak disappears when the cellsof metamaterials are rotated.The cuts of metamaterials in different directions destroythe properties of metamaterials in different degrees.2.The scattering of metallic sphere coated by metamaterials based on Mie seriessolution is studied.Mie series formulas for EM scattering of one-layer and two-layerhomogeneous dispersive media spheres are derived.The scattering of metallic spherecoated by metamaterials or ferrite is compared.Results of Mie series solution show thatthe different material parameters of metamaterials play an important part in thebackward radar cross section (RCS) of metallic sphere.3.By introducing magnetic dispersion,the auxiliary differential equation (ADE)method and shift operator (SO) method in FDTD method for metamaterials are derived.Lossy Drude and Lorentz polarization and magnetization models are used to simulatemetamaterials.The permeabilityμof metamaterials may be described by Pad(?)approximation in jω.Jωis then replaced by (?)/(?)t.By introducing z_t defined as a shift operator,the relation between B and H in SO-FDTD method is derived.We deduce thedifferential equations that describe characters of electromagnetic wave in metamaterials.We obtain two-dimension ADE-FDTD formulation for metamaterials by dispersing theequations.Numerical results of FDTD method show that (i),Though metamaterialsmake the scattering of backward and little bistatic angles decrease,the scattering offorward and big bistatic angles increase inversely.(ii),Generally speaking,the increaseof metamaterials'plasma frequency,damping frequency,and depth leads to the decreaseof RCS of metallic column.And (iii),The degree of metamaterials' match and isotropyplays important parts in the decrease of the back scattering of the metallic sphere.Witha careful selection of metamaterials' parameters,the echo of radar targets can beeffectively decreased.The application of metamaterials in cloak is discussed.4.Wave propagation in metamaterials is simulated with FDTD method.Firstly,theinteraction between Gaussian beam and isotropic metamaterials slab is simulated,suchas negative index,phase compensation,piano-concave lens imaging.Then thenumerical results of ADE-FDTD method show that the sign ofx component of relativepermeability tensor of anisotropic metamaterials (AMM) determines the refraction isregular or anomalous,whereas the sign of z component of relative permeability tensorof AMM determines the energy flow is positively refracted or negatively refracted.Thewave vector and energy flow density in AMM are not always parallel or antiparallel.Finally,the directions of the forward and backward surface and guided wave excitedinfluenced by the material parameters of AMM in multi-layered structures are analyzedwith SO-FDTD method.Their applications of metamaterials in resonator,lens imaging,beam splitter,linear polarizer,solid-state spectroscopy et al.are discussed.