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FDTD Method Investigation On The Electromagnetic Scattering Of Rough Surface And The Composite Scattering Of Rough Surface And Target

Posted on:2011-01-25Degree:DoctorType:Dissertation
Country:ChinaCandidate:J LiFull Text:PDF
GTID:1118360305464255Subject:Radio Physics
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This dissertation presents a systematic and deep investigation on the electromagnetic (EM) scattering from rough surface and composite scattering from rough surface and target by the finite-difference time-domain (FDTD) method. Firstly, the EM scattering of rough surface and the composite scattering of rough surface and target are investigated with the time-harmonic wave excitations. Then, from the point of time domain, the composite scattering characteristic of uniform dielectric and dispersive rough surface with and without a target are analyzed with the pulsed wave illuminations. Finally, the scattering characteristic of anisotropic medium is studied, and the far-zone scattered field of a target in a lossless half space is also exactly calculated. The main contributions of the dissertation are as following:1. Based on the fundamental principle of FDTD method in two-dimensional (2-D) space, the characteristic of composite scattering from one-dimensional (1-D) rough surface with and without a target are systematically analyzed with the time-harmonic wave incidence, which includes the scattering from 1-D single-layered and layered rough surface, and the composite scattering from 1-D single-layered and layered rough surface with a target. And the numerical results by the FDTD method are also compared with those by the method of moment, which shows a good agreement.2. Using the basic theories of the three-dimensional (3-D) parallel FDTD method and the basic principle of scattering from 2-D rough surface, the EM scattering from a 2-D single-layered and layered rough surface, and the composite scattering from the 2-D single-layered rough surface and a 3-D target are examined with the time-harmonic wave excitation in detail. The scattering of 2-D single-layered rough surface is compared with the result by the Kirchhoff Approximation, which shows an excellent consistency over the middle and small scattered angular range.3. The extrapolation formulas of the transient field in 2-D and 3-D FDTD space are derived. From the point of time domain, the scattering characteristic of 1-D and 2-D rough surface, the composite scattering from 1-D rough surface and 2-D target, and the composite scattering from 2-D rough surface and 3-D target are studied with the pulsed wave illumination, respectively. And the results by the pulsed FDTD method are compared and verified with those of the time-harmonic wave excitations.4. The ADE-FDTD formulas are derived for the Debye medium, the Lorentz medium, and the Drude medium. In order to absorb the outward-propagating wave well, the CPML is employed to truncate the dispersive medium. From the point of time domain, the reflection and transmission coefficients of 1-D half-space Debye, Lorentz and Drude medium are calculated with the pulsed wave excitations, which are also compared with the results by the analytic method. In addition, taking the single-pole and two-pole Debye model for example, the composite EM scattering from 1-D dispersive sea water and soil with and without a target are analyzed, and the results are also verified by those of the time-harmonic wave incidence.5. According to the theory of Yee cell, averaging value method and interpolation method, the FDTD formulas of electric- and magnetic-anisotropic medium are derived in 2-D and 3-D space in detail. The EM scattering characteristic of 2-D and 3-D anisotropic target are investigated and validated by the results in the literature. Meanwhile, the MIPML is used to truncate the anisotropic medium, and the angular distribution of scattered coefficient from an anisotropic rough surface is calculated for the TM polarization.6. In light of Maxwell's equations, the hybrid scheme of the injection of plane wave in lossless half space is presented to obtain the exact near fields. And the near-field to far-field extrapolation formulas in half space are adopt to aquire the far-zone scattered field of the target, which is verified by that of the three-wave method presented in the literature.
Keywords/Search Tags:Electromagnetic scattering, Finite-difference time-domain method, Rough surface, Target, Parallel algorithm
PDF Full Text Request
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