Browsing by Subject "Triangular Surface Meshing"

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Open Access
Comparison of two physical optics integration approaches for electromagnetic scattering
(2008) Öztürk, Ender
A computer program which uses two different Physical Optics (PO) approaches to calculate the Radar Cross Section (RCS) of perfectly conducting planar and spherical structures is developed. Comparison of these approaches is aimed in general by means of accuracy and efficiency. Given the certain geometry, it is first meshed using planar triangles. Then this imaginary surface is illuminated by a plane wave. After meshing, Physical Optics (PO) surface integral is numerically evaluated over the whole illuminated surface. Surface geometry and ratio between dimension of a facet and operating wavelength play a significant role in calculations. Simulations for planar and spherical structures modeled by planar triangles have been made in order to make a good comparison between the approaches. Method of Moments (MoM) solution is added in order to establish the accuracy. Backscattering and bistatic scattering scenarios are considered in simulations. The effect of polarization of incident wave is also investigated for some geometry. Main difference between approaches is in calculation of phase differences. By this study, a comprehensive idea about accuracy and usability due to computation cost is composed for different PO techniques through simulations under different circumstances such as different geometries (planar and curved), different initial polarizations, and different electromagnetic size of facets.
Open Access
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.