Browsing by Author "Yurchenko, V. B."
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Item Open Access Asymptotic wave-like modeling of dielectric lenses(IEEE, 2007) Yurchenko, V. B.; Altıntaş, AyhanWe propose asymptotic wave-like approximations for the accurate modeling of dielectric lenses used in quasi-optical systems of millimeter, submillimeter, and infrared wave applications. For the comparison, we obtain an exact full-wave solution of two-dimensional focusing lens problem and use it as a benchmark for testing and validation of asymptotic models being proposed.Item Open Access Complex source radiation in a cylindrical radome of metal-dielectric grating(IEEE, 1999) Altintas, A.; Ouardani, S.; Yurchenko, V. B.The radiation fields of a line source enclosed in a circular dielectric radorne with grating consisting of an array of thin lossy metal strips are analyzed. The variations of the directivity of the source beam with respect to the beam direction are studied. The possibility of damping these variations by an appropriate design of the radome is demonstrated.Item Open Access Double-sided split-step MM-wave Fresnel lenses: design, fabrication and focal field measurements(European Optical Society : Rapid Publications, 2014-09) Yurchenko, V. B.; Ciydem, M.; Gradziel, M.; Murphy, J. A.; Altintas, A.Design, fabrication and focal field measurements of W-band Fresnel lenses to produce well-shaped Gaussian beams in the focal domain are presented. Two lenses, one of Teflon and another of Polyamide, have been compared in their performance with a double-sided Fresnel lens of different design, with full height of Fresnel steps. Experiments show that a good focusing ability of all the lenses is achieved. They produce the target beam according to the design. Yet, the lenses of split-step design are thinner, have lower insertion losses, and a greater focal depth as compared to more conventional Fresnel lenses.Item Open Access Experimental conditions for the excitation of thin disk whispering-gallery-mode resonators(Electromagnetics Academy, 2013) Yurchenko, V. B.; Altintas, A.; Ciydem, M.; Koc, S.Measurements of mm-wave excitation spectra of highorder whispering gallery modes in free-space cylindrical disk resonators as functions of resonator thickness have been made. Resonators in the form of tight stacks of thin dielectric disks excited via dielectric waveguides have been used in the experiment. Experimental conditions for the excitation of thin-disk resonators have been found. A simple approach for the modeling of resonator spectra and recovery of dielectric parameters has been proposed.Item Open Access Improving the accuracy of a time lens(Optical Society of America, 1997-11) Yurchenko, V. B.A method for improving the accuracy of temporal imaging with an imperfect time lens is proposed. Signal distortion arising from complicated dispersion of the delay lines can be reduced considerably by appropriate choice of the phase-modulation function including the second harmonic of the basic modulation frequency and a specific phase shift of the modulation with respect to the main signal. The method is of particular interest for picosecond and femtosecond optical pulse generation.Item Open Access Modelling a resistive-reflector antenna by the complex source-dual series approach: the 2-D case of H-polarization(IEEE, 1995) Altıntaş, Ayhan; Nosich, A. I.; Yurchenko, V. B.The simulation of reflector antenna is normally conducted under an assumption of the perfect conductivity of reflector. This paper presents an analysis of resistive reflector beamforming using modified method of regularization for solving the scattering from a curve resistive strip. Besides, to simulate a directive feed in equally accurate manner, the Complex Source Method is used.Item Open Access Numerical optimization of a cylindrical reflector-in-radome antenna system(IEEE, 1999-04) Yurchenko, V. B.; Altintaş, A.; Nosich, A. IAccurate 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.Item 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.Item Open Access Physical optics modeling of 2D dielectric lenses(Optical Society of America, 2009-01-27) Yurchenko, V. B.; Altintas, A.We propose an advanced physical optics formulation for the accurate modeling of dielectric lenses used in quasi-optical systems of millimeter, submillimeter, and infrared wave applications. For comparison, we obtain an exact full-wave solution of a two-dimensional lens problem and use it as a benchmark for testing and validation of asymptotic models being considered.