Yazar "Alparslan, Aytac" seçeneğine göre listele
Listeleniyor 1 - 4 / 4
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Current Status of MMP Analysis of Photonic Structures in Layered Media(IEEE, 2016) Alparslan, Aytac; Hafner, ChristianIn this paper, the recent updates in the Multiple Multipole Program (MMP) analysis of photonic structures are introduced, with a special emphasis on the structures built in layered media. Along with the mathematical background of MMP, several numerical techniques including the scattering and eigenvalue analyses of photonic structures are introduced. Numerical examples are also included to demonstrate the advantages of MMP over other computational analysis tools, which will be further discussed during the talk.Öğe Dual-Band Frequency Selective Surface-Backed Reflectarray for High-Speed Ka-Band Satellites(Mdpi, 2024) Gulseren, Ahmet Hulusi; Alparslan, Aytac; Tokan, Nurhan TurkerA dual-band, dual-polarized frequency selective surface (FSS)-backed multilayer reflectarray antenna is designed for 5G high-speed satellites operating at Ka-band uplink and downlink frequencies (20/30 GHz). A reflectarray antenna system consists of two reflectarrays that are separated from each other by an FSS layer that behaves as a planar bandpass filter at Ka-band satellite uplink frequencies. Each reflectarray antenna is designed with dual-polarized unit cells. In order to achieve a uniform phase distribution across the reflectarray surface, physical dimensions and positions of the unit cells with a fixed periodicity are carefully chosen. The FSS conductor is etched to the bottom layer of the 30 GHz reflectarray substrate to save cost and weight. The reflectarray performance is analyzed by using CST Microwave Studio and array theory. A prototype is fabricated, and the results are experimentally verified. The gain of the reflectarray is measured as 21.13 dBi and 26.94 dBi at 20 and 30 GHz, respectively. A crosspol level of more than 35 dB is observed at both frequencies. The simulated and measured results show that the proposed reflectarray is suitable for high-speed Ka-band satellites.Öğe Mode Analysis of Waveguides in Layered Media(IEEE, 2018) Alparslan, AytacIn this paper, the mode analysis of realistic waveguides in multi layered geometries, which is among the most demanding problems in computational electromagnetics, is performed. Multiple multipole program (MMP) combined with layered media Green's functions is used to obtain the locations of the mode wave numbers on a complex plane bounded by the values given by the user. At an intermediate step of the MMP analysis, the approximate locations of the physical modes are obtained and then used to obtain exact locations of the corresponding modes. It is shown that the approximate locations taken from the MMP analysis provide a very precise starting point to determine the exact locations of the modes not only for MMP but also for all the well-known numerical methods, providing a guideline for the solution of the most demanding problems in the mode analysis. During the talk, advantages of the MMP analysis will be demonstrated by several numerical examples solved by different numerical techniques with and without the approximate location obtained from MMP.Öğe Spectral Analysis of Line Sources With Complex Longitudinal Wavenumbers in Planarly Layered Media(IEEE-Inst Electrical Electronics Engineers Inc, 2021) Alparslan, AytacSpectral properties of line sources carrying electric or magnetic current placed in a planarly layered medium are analyzed. It is shown that when the current along the line varies in the longitudinal direction by an exponential function with a complex exponent, classical Sommerfeld radiation condition that ensures outgoing and decaying fields simultaneously cannot always be used. Instead, depending on the exponent and the material properties of the layered medium, outgoing and exponentially increasing or incoming and exponentially decreasing waves are generated. This property is not observed when the exponent is real where the classical Sommerfeld radiation condition is fulfilled. In this article, an in-depth analysis of layered media is first performed in spectral domain as a function of the longitudinal dependence of the line sources. Then, the fields generated by the line sources are obtained by Sommerfeld integrations using two different radiation conditions separately. The effect of the radiation condition on the fields are discussed both in the spectral and spatial domains. In addition, field patterns are compared with the results obtained by finite element method (FEM) combined with perfectly matched layers (PMLs) and several guidelines for increasing the efficiency of simulations by FEM are introduced.