Browsing by Subject "Electromagnetic waves Scattering."

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    Application of biconjugate gradient stabilized method with spectral acceleration for propagation over terrain profiles
    (2003) Babaoğlu, Barış
    Using the Method of Moments (MoM) for the computation of electromagnetic radiation / surface scattering problems is a very popular approach since obtained results are accurate and reliable. But the memory requirement in the MoM to solve discretized integral equations and the long computational time of O(N3 ) operation count (where N is the number of the surface unknowns) make the method less favorable when electrically large geometries are of interest. This limitation can be overcome by using BiConjugate Gradient Stabilized (BiCGSTAB) method, a non-stationary iterative technique that was developed to solve general asymmetric/non-Hermitian systems with an operational cost of O(N2 ) per iteration. Furthermore, the computational time can be improved by the spectral acceleration (SA) algorithm which can be applied in any iterative technique. In this thesis, Spectrally Accelerated BiCGSTAB (SA-BiCGSTAB) method is processed over systems that have huge number of unknowns resulting a computational cost and memory requirement of O(N) per iteration. Applications are presented on electrically large rough terrain profiles. The accuracy of the method is compared with MoM, conventional BiCGSTAB method and Spectrally Accelerated Forward-Backward Method (SA-FBM) where available.
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    Fast multipole method for the solution of electromagnetic scattering problems
    (2003) Ergül, Özgür Salih
    The fast multipole method (FMM) is investigated in detail for the solution of electromagnetic scattering problems involving arbitrarily shaped three-dimensional conducting surfaces. This method is known to reduce the computational complexity and the memory requirement of the solution without sacrificing the accuracy. Therefore, it achieves the solution of large problems with less computational resources compared to the other traditional solution algorithms. However, the expected efficiency of the FMM may not be obtained unless the appropriate choices of the components are made. The types of the employed integral equation, iterative algorithm, and preconditioning technique directly affect the efficiency of the implementations. Performances of these components are also related to each other, and their simultaneous optimization creates a challenging task in the design of an efficient solver.