Browsing by Author "Ghassemiparvin, Behnam"

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    Analysis of edge waves due to a point source in the presence of a PEC wedge
    (IEEE, 2014) Ghassemiparvin, Behnam; Altıntaş, Ayhan
    In this paper, we investigate the behavior of the field in the paraxial region of a perfectly conducting wedge and analyze the guiding effect of the wedge. It is observed that as the wedge angle increases, the guidance effect of the wedge decreases and the scattered field in the paraxial region is maximum for the half plane. In addition, interaction of the edge waves with a spherical impedance scatterer is investigated. It is found that for the backscattering case, as the impedance mismatch between the spherical boss and the free-space increases the scattered field due to the boss increases. However for the forward scattering case, impedance of the boss does not affect the scattered field significantly.
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    Scattering from impedance objects at the edge of a perfectly conducting wedge
    (2012) Ghassemiparvin, Behnam
    In this study, scattering from impedance bodies positioned at the edge of a perfectly conducting (PEC) wedge is investigated. In the treatment of the problem, eigenfunction expansion in terms of spherical vector wave functions is employed. A complete dyadic Green’s function for the spherical impedance boss at the edge is developed and through decomposing the dyadic Green’s function, it can be observed that the contribution of the scatterer is separated from the wedge. It is shown that the scattering is highly enhanced by the edge guided waves. For the general case of irregularly shaped scatterer the solution is extended using T-matrix method. The method is implemented by replacing free space Green’s function with the dyadic Green’s function of the PEC wedge. The solution is verified by applying it to the case of spherical scatterer and results are compared with the dyadic Green’s function solution. The T-matrix solution is generalized for the multiple scatterer case. Numerical results are obtained for two impedance scatterers at the edge and compared with the PEC case.
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    Spherical wave representation of the dyadic Green's function for a spherical impedance boss at the edge of a perfectly conducting wedge
    (Electromagnetics Academy, 2012) Ghassemiparvin, Behnam; Altıntaş, Ayhan
    In this work, canonical problem of a scatterer at the edge of a wedge is considered and eigenfunction solution is developed. Initially, a dyadic Green's function for a spherical impedance boss at the edge of a perfect electrically conducting (PEC) wedge is obtained. Since scattering from objects at the edge is of interest, a three-dimensional Green's function is formulated in terms of spherical vector wave functions. First, an incomplete dyadic Green's function is expanded in terms of solenoidal vector wave functions with unknown coefficients, which is not valid in the source region. Unknown coefficients are calculated by utilizing the Green's second identity and orthogonality of the vector wave functions. Then, the solution is completed by adding general source correction term. Resulting Green's function is decomposed into two parts. First part is the dyadic Green's function of the wedge in the absence of the sphere and the second part represents the effects of the spherical boss and the interaction between the wedge and the scatterer. In contrast to cylindrical vector wave function expansions and asymptotic solutions which fail to converge in the paraxial region, proposed solution exhibits good convergence everywhere in space. Using the developed Green's function scattered field patterns are obtained for several impedance values and results are compared with those of a PEC spherical boss. Effects of the incident angle and surface impedance of the boss on the scattering pattern are also examined.