Browsing by Subject "Physical Theory of Diffraction (PTD)"

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    Implementation of physical theory of diffraction for radar cross section calculations
    (2002) Öztürk, Alper Kürşat
    A computer program which uses the Physical Theory of Diffraction (PTD) method to calculate the Radar Cross Section (RCS) of perfectly conducting targets with arbitrary shape is developed. Given an arbitrary surface, it is first meshed using planar triangles. The area of each triangle is restricted to be smaller than 0.005λ 2 in order to obtain a good approximation to the actual surface. After meshing, Physical Optics (PO) surface integral is numerically evaluated over the whole surface. If the surface has edges or wedges, diffractions originating from these edges play a significant role in the overall scattered field. This part of the diffracted field is calculated using PTD-EEC method. Calculation of the edge currents is made possible by canonically modelling the arbitrary-shaped edge. If the surface of the scatterer has thin wires attached to it, then the thin wire scattering formulation in the literature is applied. Expressions for scattering mechanism on a straight wire are based on diffraction, attachment, reflection and launch. The results get sufficiently accurate especially for electrically large bodies.
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    RCS computations with PO/PTD for conducting and impedance objects modeled as large flat plates
    (2005) Albayrak, N. Aslıhan
    Calculation of Radar Cross Section (RCS) of arbitrary bodies using Physical Optics (PO) Theory and Physical Theory of Diffraction (PTD)is considered. For bodies with impedance surface boundary condition, only PO is used. Analytical approach to PO integral is used to achieve faster computations. A computer program has been developed in Fortran in order to calculate the Radar Cross Section (RCS). Arbitrary shape is modeled as triangular facets of any area by the help of graphical tools. Given the triangular meshed model of an arbitrary body, Physical Optics(PO) surface integral is numerically evaluated over the whole surface. There is no limitation on the size of the triangles, as soon as the total surface does not retire from the original one. Shadowing algorithm has been used in order to have more accurate solutions. Additionally, flash points of PO are visualized over the surface of targets, hence local nature of high-frequency phenomena is proved. Induced surface currents, edge currents and RCS have been calculated for some basic shapes and the fuel tank model of F-16 airplanes. Induced surface currents have been visualized over the surface of the particular targets using Matlab.