Feray Hacivelioglu

Wedge Diffracted Waves Excited by a Line Source: Method of Moments (MoM) Modeling of Fringe Waves

Method of moments (MoM) simulation of fringe waves generated by a line source that excites a perfectly reflecting wedge is introduced and compared with the exact physical theory of diffraction (PTD) fringe waves.

On the Modified Theory of Physical Optics

Basic features of the modified theory of physical optics (MTPO) are discussed on the example of scattering at perfectly reflecting half-planes and wedges. It is shown that violations of the geometrical optics (GO), introduced in this technique, result in the MTPO solutions which do not satisfy the Helmholtz equation. They are incorrect at a finite distance from a scattering object; however it can be considered as sort of approximations for the field at a large distance from an edge and away from the GO boundaries.

Wedge Diffracted Waves Excited by a Line Source: Exact and Asymptotic Forms of Fringe Waves

Todays understanding and modeling of diffraction at antennas and scattering objects necessitates further analysis of diffracted fields in the vicinity of scattering edges/tips. This paper derives exact and asymptotic forms of fringe waves excited by a line source around a perfectly reflecting wedge. According to the physical theory of diffraction (PTD), these waves are found as the difference between the exact and physical optics (PO) solutions of the wedge diffraction problem. The exact solution has been well-known for a long time, e.g., H. M. Macdonald, Electric Waves, Cambridge Univ. Press, 1902, pp. 186-198; Electromagnetic and Acoustic Scattering by Simple Shapes, J. J. Bowman, T. B. A. Senior, and P. L. E. Uslenghi, Eds., Hemisphere, 1987. In this paper, we focus on the PO solution. Its new exact and asymptotic forms are derived and the fringe waves are analyzed. Numeric results illustrate the theory.

Backscattering From a Soft–Hard Strip: Primary Edge Waves Approximations

High-frequency approximation is constructed for backscattering from a strip with one face soft and the other face hard (i.e., with Dirichlet and Neumann boundary conditions, respectively). This approximation is based on the solution of the canonical problem for a wedge with the same boundary conditions. Its exact solution belongs to Malyuzhinetz (Ann. Phys., vol. 6, no. 1-2, pp. 107-112, 1960). Here, we utilize its approximations presented in Ufimtsevs work (IEEE Antennas Propag. Mag., Dec. 2013) and derive simple asymptotics for backscattering. Only primary edge waves are taken into account. The influence of the secondary diffraction is estimated asymptotically to validate this approach. The results are compared to the physical optics (PO) and Physical Theory of Diffraction (PTD) approximations.

Fringe Waves from a Wedge With One Face Electric and the Other Face Magnetic

Fringe waves represent the diffracted field generated by the nonuniform/fringe surface currents concentrated in vicinity of sharp scattering edges. For perfectly conducting wedges, they have been studied in a number of publications. In this communication, fringe waves for a wedge with one face electric and the other magnetic are analyzed analytically and numerically.

Propagation of Waves in a Bifurcated Cylindrical Waveguide with Wall Impedance Discontinuity

In the present work the radiation of sound from a bifurcated circular waveguide formed by a semi-infinite rigid duct inserted axially into a larger infinite tube with discontinuous wall impedance is reconsidered through an alternative approach which consists of using the mode matching technique in conjunction with the Wiener-Hopf method. By expressing the total field in the appropriate waveguide region in terms of normal modes and using the Fourier transform technique elsewhere, we end up with a single modified Wiener-Hopf equation whose solution involves an infinite system of algebraic equations. This system is solved numerically and the influence of some parameters on the radiation phenomenon is shown graphically. The equivalence of the direct method described in (1) and the present mixed method are shown numerically.

Analysis of a Coaxial Waveguide with Finite-Length Impedance Loadings in the Inner and Outer Conductors

A rigorous Wiener-Hopf approach is used to investigate the band stop filter characteristics of a coaxial waveguide with finite-length impedance loading. The representation of the solution to the boundary-value problem in terms of Fourier integrals leads to two simultaneous modified Wiener-Hopf equations whose formal solution is obtained by using the factorization and decomposition procedures. The solution involves 16 infinite sets of unknown coefficients satisfying 16 infinite systems of linear algebraic equations. These systems are solved numerically and some graphical results showing the influence of the spacing between the coaxial cylinders, the surface impedances, and the length of the impedance loadings on the reflection coefficient are presented.

Wiener-Hopf Analysis of Finite-Length Impedance Loading in the Outer Conductor of a Coaxial Waveguide

A new canonical scattering problem consisting of the propagation of the dominant TEM mode at the finite-length impedance discontinuity in the outer conductor of a coaxial waveguide is solved. The contributions from the successive impedance discontinuities are accounted for through the solution of a modified Wiener-Hopf equation. Some graphical results displaying the reflection and transmission characteristic are presented.

Diffraction at trilateral cylinders with combinations of soft and hard faces: first-order PTD approximation

ABSTRACT The paper investigates diffraction at trilateral cylinders with combinations of soft (electric) and hard (magnetic) faces. Scattered field in far zone is calculated according to the physical theory of diffraction. The first-order high-frequency approximation is constructed as a sum of single-diffracted edge waves. Plotted numerical data clearly demonstrate the difference for objects with different faces. Substantial suppression of backscattering is observed for cylinders with soft-hard illuminated faces. Fringe wave contributions to the scattered field are shown. Physical theory of diffraction results are compared with those of the physical optics and confirmed by the method of moments.

Diffraction at a Rectangular Plate: First-Order PTD Approximation

Physical theory of diffraction (PTD) is developed for the field scattered at a perfectly conducting rectangular plate. Grazing incidence and grazing scattering are analyzed. High-frequency asymptotic estimations are derived. Bistatic and monostatic scenarios are considered. Comparison is presented with known experimental and numeric results obtained by the method of moments (MoM).