F. Sikta

Bio: F. Sikta is an academic researcher from Ohio State University. The author has contributed to research in topics: Singularity & Plane (geometry). The author has an hindex of 1, co-authored 1 publications receiving 107 citations.

First-order equivalent current and corner diffraction scattering from flat plate structures

Abstract: The equivalent current concept is used to compute the scattering patterns of flat plate structures. It is also used to obtain the broadside scattering lobe for any incidence plane. The essential feature introduced in this paper is that only the components of the equivalent current perpendicular to the incidence plane are used. No special treatment of the singularity in the plane wave diffraction coefficient (which is the basis of the equivalent current concept) is required. Instead, this choice of equivalent current components is such that the singularity at one edge segment is canceled by the singularity at the opposite edge segment. For modern day computers there is sufficient accuracy that the main scattering lobe can be obtained in the limit as one approaches broadside. The same results can be obtained for plate structures made of straight edges by using a new corner diffraction analysis. For certain cases where the observation angle is sufficiently removed from normal incidence to an edge, the corner diffraction analysis appears to yield more accurate results.

Techniques for High-Frequency Problems

Abstract: Techniques based on the method of modal expansions, the Rayleigh-Stevenson expansion in inverse powers of the wavelength, and also the method of moments solution of integral equations are essentially restricted to the analysis of electromagnetic radiating structures which are small in terms of the wavelength. It therefore becomes necessary to employ approximations based on “high-frequency techniques” for performing an efficient analysis of electromagnetic radiating systems that are large in terms of the wavelength.

Scattering center analysis via Prony's method

Abstract: High-frequency scattering can often be described in terms of scattering centers, and an understanding of the geometries which give rise to these centers is important in the area of radar cross section modification. Certain canonical geometries have been treated theoretically with asymptotic methods, but, in general, one must study the behavior of scattering centers empirically. Prony's method provides a way of extracting the locations (projected on the path of propagation) and weighting coefficients of scattering centers from the backscattered field as a fuction of frequency. It has been found to be superior to the conventional Fourier transform technique in resolution and dynamic range.

Elementary Edge Waves and the Physical Theory of Diffraction

Abstract: A more general and rigorous form of the physical theory of diffraction (PTD) is presented. This theory is concerned with the field scattered by perfectly conducting bodies whose surfaces have sharp edges and whose linear dimensions and curvature radii are large in comparison with a wavelength. The PTD proposed here is based on the conception of elementary edge waves (EEWs). These are the waves scattered by the vicinity of an edge infinitesimal element. Their high-frequency asymptotics are given. Various definitions of EEWs (Maggi, Bateman, Rubinowicz, Mitzner, Michaeli) are discussed. Total edge waves (TEWs) scattered by the whole edge are found to be a linear superposition of all EEWs. PTD enables one to determine correctly the first (leading) term in the high-frequency asymptotic expansions for primary and multiple TEWs both in ray regions and diffraction regions such as caustics, shadow boundaries, and focal lines. Some examples of these asymptotics are given. The connection of PTD with other ...

High frequency techniques for antenna analysis

Abstract: A summary of various high-frequency techniques is presented for analyzing the electromagnetic radiation from antennas in the presence of their host environment. These techniques provide physical insight into antenna radiation mechanisms and are found to be highly efficient and accurate for treating a variety of practical antenna configurations. Examples to which these techniques have been applied include open-ended waveguide antennas, horn and reflector antennas, and antennas on aircraft and spacecraft. The accuracy of these techniques is established via numerical results which are compared with those based on other independent methods or with measurements. These high frequency methods can be combined with other techniques, through a hybrid scheme, to solve an even greater class of problems than those which can be solved in an efficient and tractable manner by any one technique alone. >

Electromagnetic Scattering from the Sea at Low Grazing Angles

Abstract: Radars operating from ships, shore installations, and low-flying aircraft inevitably view the sea at low grazing angles from zero to a few degrees. Under these conditions it is expected that the surface might often be deeply shadowed, yet the experimental evidence is unclear, sometimes even contradictory. It is obvious that this is a very special scattering regime, in which the conventional ideas of sea scatter are quite possibly of little use. Any approach to understanding this regime must be guided by two basic questions: 1. In the most general case of bistatic scattering, how much, and what part of the sea surface is actually illuminated and observed simultaneously in a scattering interaction? 2. What are the special structural characteristics of the scattering elements in such regions, and what theoretical models are to be used.