Study Of Electromagnetic Characteristics Of Double Negative Medium

In this thesis, the electromagnetic (EM) wave propagation and scattering in double negative medium (DNG) are investigated with finite-difference time-domain (FDTD) method and CST software. The applications of DNG to reduce RCS are discussed. After discussing the physical mechanism analyses of the split ring resonators (SRRs) in detail, we propose two kinds of new structure units of DNG.Firstly, the numerical simulation of DNG unit is studied using FDTD method. In order to guarantee the fidelity of electromagnetic wave propagation in waveguide, we give the proper value of some parameters of modulated Gaussian pulse. The total field - scattering field technique is reset in view of the particularity of DNG simulation, which saves the computing time, reduces the computation memory and enhances the computing efficiency. The physical mechanisms of electric resonance and magnetic resonance of SRRs in waveguide are simulated and analysed.Secondly, The NRW formulas of electromagnetic constitutive parameters reconstruction of dielectric medium are educed from EM theory, and phase automatic control is realized by using Taylor formula. The inversion formulas of constitutive parameters of DNG in waveguide are given through revising the NRW method according to the difference between DNG and ordinary medium.Thirdly, the periodization influences of the three kinds of truncation boundary are analysed according to the image theory. The SRR located in different boundaries is simulated using CST software. It is demonstrated that the resonance frequency, width and peak of the SRR after the different boundary periodization is dissimilar, which accords with theory.Fourthly, we propose two kinds of new structure units of DNG. One is the tunable SRR whose magnetic resonance frequency can be tuned. The other is double-split ring resonator which realizes magnetic resonance and electric resonance simultaneously. The dependences of the magnetic resonance frequency of the tunable SRR are examined using CST software. We also study the transmission characteristic of left-handed (LH) structures composed of tunable SRR and wires, and verify that the LH transmission peak can be tuned. We compare simulation results of double-split ring resonator using FDTD method and CST software respectively, and analyse its physical mechanism.At last, a parallel ADE-FDTD algorithm based on MPI platform is realized. It is applied to overcome a drawback that too much time and prohibitive computation resources are needed for the analysis of electromagnetic characteristic of electrically large objects for a computer. The scatter characteristic of electrically large objects coated by DNG is analysed. Numerical results show that DNG can reduce the backscattering of objects, but increase forward scattering of objects simultaneously.