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Memory-efficient multilevel physical optics algorithm for the solution of electromagnetic scattering problems
Ankara : The Department of Electrical and Electronics Engineering and the Institute of Engineering and Sciences of Bilkent University, 2007.Thesis (Master's) -- Bilkent University, 2007.Includes bibliographical references leaves 55-56For the computation of electromagnetic scattering from electrically large targets,
physical optics (PO) technique can provide approximate but very fast solutions.
Moreover, higher order approximations, such as physical theory of diffraction
(PTD) including the diffraction from the edges or sharp corners can also be
added to the PO solution in order to enhance the accuracy of the PO. On the
other hand, in real-life radar applications, where the computation of the scattering
pattern over a range of frequencies and/or angles with sufficient number of
samples is desired, further acceleration may be needed. Multilevel physical optics
(MLPO) algorithm can be used for such applications, in which a remarkable
speed-up can be achieved by evaluating the PO integral in a multilevel fashion.
As the correction terms like PTD are evaluated independently just on the edges
or sharp corners, whereas the PO integration is carried out on the entire target
surface, PO integration is the dominant factor in the computational time
of such higher order approximations. Therefore accelerating the PO integration
will also reduce the computational time of such higher order approximations.
In this thesis, we propose two different improvements on the MLPO algorithm.First improvement is the modification of the algorithm that enables the solution
of the scattering problems involving nonuniform triangulations, thus decreasing
the CPU time. Second improvement is the memory-efficient version, in which the
O (N3
) memory requirement is decreased to O (N2
log N). Efficiency of the two
proposed improvements are demonstrated in numerical examples including a reallife
scattering problem, with which the scattering pattern of a three-dimensional
stealth target is evaluated as a function of elevation angle, azimuth angle, and
frequency.Manyas, Kaplan AlpM.S