Browsing by Author "Altintaş, A."

Now showing 1 - 7 of 7

Open Access
Analysis of the elliptic-profile cylindrical reflector with a non-uniform resistivity using the complex source and dual-series approach: H-polarization case
(Springer, 2013) Oğuzer, T.; Altintaş, A.; Nosich, A. I.
An elliptic-profile reflector with varying resistivity is analyzed under the illumination by an H-polarized beam generated by a complex-source-point (CSP) feed. The emphasis is done on the focusing ability that is potentially important in the applications in the optical range related to the partially transparent mirrors. We formulate the corresponding electromagnetic boundary-value problem and derive a singular integral equation from the resistive-surface boundary conditions. This equation is treated with the aid of the regularization technique called Riemann Hilbert Problem approach, which inverts the stronger singular part analytically, and converted to an infinite-matrix equation of the Fredholm 2nd kind. The resulting numerical algorithm has guaranteed convergence. This type of solution provides more accurate and faster results compared to the known method of moments. In the computations, a CSP feed is placed into a more distant geometrical focus of the elliptic reflector, and the near-field values at the closer focus are plotted and discussed. Various far-field radiation patterns including those for the non-uniform resistive variation on the reflector are also presented.
Open Access
Analytical regularization based analysis of a spherical reflector symmetrically illuminated by an acoustic beam
(IEEE, 2000) Vinogradov, S. S.; Vinogradova, E. D.; Nosich, A. I.; Altintaş, A.
A mathematically accurate and numerically efficient method of analysis of a spherical reflector, fed by a scalar beam produced by a complex source- point feed, is presented. Two cases, soft and hard reflector surface, are considered. In each case the solution of the full-wave integral equation is reduced to dual series equations and then further to a regularized infinite- matrix equation. The latter procedure is based on the analytical inversion of the static part of the problem. Sample numerical results for 50-λ reflectors demonstrate features that escape a high-frequency asymptotic analysis. (C) 2000 Acoustical Society of America.
Open Access
Computer-aided analysis and simulation of complex passive integrated optical circuits of arbitrary rectilinear topology
(SPIE, 1994-05) Önal, G.; Altintaş, A.; Özaktaş, Haldun M.
Optical interconnections can be beneficially employed at the chip-to-chip or backplane level of high-performance computing systems. One method of providing high speed and density interconnections among a large number of integrated circuit chips is with a passive integrated optics circuit. We have developed a method of breaking down arbitrarily complex rectilinear circuits into elementary blocks whose loss and coupling properties are known. Thus, the overall loss and noise for each connection can be calculated. A high-speed algorithm based on this method has been implemented. The high speed of our analysis system makes it suitable for incorporation in an iterative design system, which determines the minimum spacings between the guides and results in acceptable crosstalk and noise levels.
Open Access
E-polarized beam scattering by an open cylindrical PEC strip having an arbitrary "conical-section" profile
(John Wiley & Sons, Inc., 2001) Oğuzer, T.; Nosich, A. I.; Altintaş, A.
Two-dimensional (2-D) scattering of waves by a conducting strip with a canonical profile is simulated in the E-polarization case. This analysis is performed by reducing a singular integral equation (IE) to the dual-series equations, and making their analytical regularization. Furthermore, the incident field is taken as a complex source point (CSP) beam. This is an extension of our previous studies about circular and parabolic reflector antennas. The algorithm features are demonstrated. Far-field characteristics are presented for quite large-size curves strips of elliptic, parabolic, and hyperbolic profiles.
Open Access
Numerical optimization of a cylindrical reflector-in-radome antenna system
(IEEE, 1999-04) Yurchenko, V. B.; Altintaş, A.; Nosich, A. I
Accurate numerical optimization based on rigorous solution of the integral equation using the method of analytical regularization is performed for a cylindrical reflector antenna in a dielectric radome. It is shown that the multiple scattering in this system is more significant for the optimum radome design than any nonplane-wave effects or the curvature of the radome. We claim that, although the common half-wavelength design is a good approximation to avoid negative effects of the radome (such as the loss of the antenna directivity), one can, by carefully playing with the radome thickness, its radius, reflector location, and the position of the feed, improve the reflector-in-radome antenna performance (e.g., increase the directivity) with respect to the same reflector in free-space.
Open Access
Numerically exact analysis of a two-dimensional variable-resistivity reflector fed by a complex-point source
(Institute of Electrical and Electronics Engineers, 1997-11) Nosich, A. I.; Yurchenko, V. B.; Altintaş, A.
Accurate numerical analysis of a two-dimensional (2-D) variable-resistivity reflector has been carried out by the method of regularization based on the analytical inversion of the corresponding static problem. The complex source-point model has been used to account for the directivity of the feeder and both the H- and E-polarization cases are considered. Far-field radiation patterns, directivity, and total radiative power have been computed for reflectors of uniform and nonuniform complex resistivities. The concept of edge loading for the control and improvement of antenna characteristics is confirmed by this numerically rigorous technique.
Open Access
Radar cross-section study of cylindrical cavity-backed apertures with outer or inner material coating: the case of E-polarization
(IEEE, 1993) Çolak, D.; Nosich, A. I.; Altintaş, A.
A dual-series-based solution is obtained for the scattering of an E-polarized plane wave from a cavity-backed aperture which is formed by a slitted infinite circular cylinder coated with absorbing material. The material coating can be done on the inner or outer surface of the cylinder. For both cases, numerical results are presented for the radar cross section and comparisons are given for two different realistic absorbing materials. The radar cross-section results are also given for the aspect angle of the screen. Finally, the dependence of radar cross section on the thickness of the absorbing layer is presented. © 1993 IEEE