Elektronik ve Haberleşme Mühendisliği Bölümü Yayın Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/260

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Citation - Scopus: 1
A New Companding Technique for Papr Reduction in Ofdm Communication Systems
(2011) Gazi, O.; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
One of the major disadvantages of OFDM communication systems is their high peak-to-average power ratio (PAPR) which degrades system performance when nonlinear power amplifiers are employed. Among the proposed PAPR tech- niques companding is favorable due to its simplicity and easy of implementation. In this article, using the arctan- gent function we propose a new compading technique for PAPR reduction. We compare the proposed technique to the previously suggested exponential companding, and μ- law companding methods. Via computer simulations it is verified that the proposed technique is better than exponen- tial and μ-law companding methods for PAPR reduction.
Citation - Scopus: 30
A New Design of Dual Band Microstrip Bandpass Filter Based On Peano Fractal Geometry: Design and Simulation Results
(2013) Mezaal, Y.S.; Eyyuboglu, H.T.; Ali, J.K.; 7688
The proposed filter design topology is based on dual coupled resonators constructed in the form of Peano fractal geometry. A dual-band microstrip bandpass filter with a quasi-elliptic response has been designed for first time based on 1st iteration Peano fractal geometry at resonant frequencies of 2.25 GHz and 4.825 GHz using a substrate of a relative dielectric constant of 10.8 and thickness of 1.27 mm. The performance of the bandpass filter structure has been analyzed using a method of moments (MoM) based software package, Microwave Office 2009, from Advanced Wave Research Inc. Results show that this filter possesses good frequency response characteristics in addition to dual bands gained which can be used for modern communication applications. © 2013 IEEE.
Citation - WoS: 4
Citation - Scopus: 27
A Novel Design of Two Loosely Coupled Bandpass Filter Based On Hilbert-Zz Resonator With Higher Harmonic Suppression
(Ieee, 2013) Mezaal, Yaqeen S.; Eyyuboglu, Halil T.; Ali, Jawad K.; 7688
New characteristics of fractal design scheme has been introduced to generate compact two poles capacitively coupled microstrip bandpass filter by using additional coupling stubs for different wireless applications. The presented fractal scheme is based on specific type of Hilbert space-filling curve which is called Hilbert-zz fractal geometry. The performance of generated bandpass filter structure has been analyzed using Sonnet software package with a relative dielectric constant of 9 and a substrate thickness of 1.27 mm. Results show that these filters possess good transmission and return loss characteristics, besides higher harmonics suppressions; meeting the specifications of most of wireless communication systems.
Citation - Scopus: 13
A Proposed Method of Photovoltaic Solar Array Configuration Under Different Partial Shadow Conditions
(Trans Tech Publications Ltd, 2014) Humada, A.M.; Hojabri, M.; Mohamed, M.B.; Bin Sulaiman, M.H.; Dakheel, T.H.
The benefit of improving the efficiency of photovoltaic (PV) solar system has come into view because of increasing the demand for electricity, especially in the urban areas. However, these PV solar systems are vulnerable to the mismatch operating conditions. Under such conditions, the performance of solar cells has decreased rapidly since the nonuniform insolation hitting the cells and with different values. Then this leads to cause rapidly decreasing in the output power value and maximum power point, beside to hot spot points that may be occurring in the solar cell which finally leads to damage these cells. This paper proposes an optimal connection of substrings with different value of shadow conditions, based on a thorough configuration that can significantly reduce that nonuniform condition loss. The refinement over existing photovoltaic (PV) solar array interconnections is proven by extensive simulation results by using MATLAB SIMULINK. © (2014) Trans Tech Publications, Switzerland.
Citation - Scopus: 2
A Tutorial Introduction to VHDL Programming
(Springer Singapore, 2018) Gazi, O.; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
This book helps readers create good VHDL descriptions and simulate VHDL designs. It teaches VHDL using selected sample problems, which are solved step by step and with precise explanations, so that readers get a clear idea of what a good VHDL code should look like. The book is divided into eight chapters, covering aspects ranging from the very basics of VHDL syntax and the module concept, to VHDL logic circuit implementations. In the first chapter, the entity and architecture parts of a VHDL program are explained in detail. The second chapter explains the implementations of combinational logic circuits in VHDL language, while the following chapters offer information on the simulation of VHDL programs and demonstrate how to define data types other than the standard ones available in VHDL libraries. In turn, the fifth chapter explains the implementation of clocked sequential logic circuits, and the sixth shows the implementation of registers and counter packages. The book’s last two chapters detail how components, functions and procedures, as well as floating-point numbers, are implemented in VHDL. The book offers extensive exercises at the end of each chapter, inviting readers to learn VHDL by doing it and writing good code. © Springer Nature Singapore Pte Ltd. 2019.
Citation - Scopus: 7
Abstraction-Based Control for Not Necessarily Closed Behaviours
(IFAC Secretariat, 2011) Moor, T.; Schmidt, K.; Wittmann, T.
This paper addresses abstraction-based supervisory control for plant and specification behaviours that are not necessarily ω-closed, i.e. plant behaviours that exhibit eventuality properties and specifications that impose eventuality properties on the closed loop. Technically, the core idea is to combine results from previous work on abstraction-based supervision of input-output behaviours with results on supervisory control of ω-languages. As our main result, we identify a controllability condition for the plant, that ensures a nonblocking closed-loop behaviour with a controller that has been obtained for a plant abstraction. © 2011 IFAC.
Citation - WoS: 23
Citation - Scopus: 24
An investigation of hydrogen bonded neutral B4Hn (n=1-11) and anionic B4H11(-1) clusters: Density functional study
(Elsevier Science Bv, 2007) Boyukata, Mustafa; Özdoğan, Cem; Ozdogan, Cem; Guvenc, Ziya B.; 120207; Ortak Dersler Bölümü
In this study, detailed analysis of the structural stability of hydrogen bonded four-atom boron clusters within the framework of density functional theory (DFT) is presented. Effects of the number of hydrogen atoms on the structural stability of 134, binding energy of the clusters, and also on the boron-hydrogen binding energy are investigated. Attention is also paid to the determination of energetically the most stable geometries of B4Hn (n = 1-11) boron hydrides, and to their isomers. The lower-lying electronic states of the B4Hn structures are investigated. In addition natural electron configurations of the most stable clusters and charge transfer between the atoms in the cluster are also analyzed. Furthermore, the stability of anionic form of B4H11(-1) cluster is examined. (c) 2006 Elsevier B.V. All rights reserved.
Citation - Scopus: 0
Analog and digital filter design
(Springer Science and Business Media B.V., 2018) Gazi, O.; Gazi, Orhan; Elektronik ve Haberleşme Mühendisliği
In this chapter, we will study analog and digital filter design techniques. A filter is nothing but a linear time invariant (LTI) system. Any LTI system can be described using its impulse response. If the impulse response of a LTI system is known, then for any arbitrary input the system output can be calculated by taking the convolution of the impulse response and arbitrary input. This also means that filtering operation is nothing but a convolution operation. And filter design is nothing but finding the impulse response of a linear time invariant system. For this purpose, we can work either in time domain or frequency domain. © Springer Nature Singapore Pte Ltd. 2018.
Citation - WoS: 0
Citation - Scopus: 0
Analysis of wave structure functions
(Ieee, 2008) Eyyuboglu, Halil T.; 7688
Wave structure function (WSF) of spherical wave is used in extended Huygens-Fresnel integral to induce the effect of turbulent atmosphere on the propagating laser beam. Depending on the approximation made and the choice of the spatial power spectral density of refractive index fluctuation function, different forms of WSFs become available. In this study, five different WSFs are numerically evaluated for pure Gaussian, cosh-Gaussian, sinh-Gaussian, cos-Gaussian and sine-Gaussian types of source plane beams. In the range of adapted source and propagation parameters, namely under weak fluctuation conditions, no substantial deviations are found to occur with respect to the WSF selection. Our results are offered in terms of graphical illustrations showing the differences in the receiver intensity profiles against the varying propagation distance.
Citation - WoS: 0
Citation - Scopus: 0
Aperture Averaging of Focused Multi-Gaussian Beams
(Electromagnetics Acad, 2013) Kamacioglu, Callan; Baykal, Yahya; Yazgan, Erdem; 7812
We investigate the behavior of the power fluctuations of the focused annular and flat-topped beams when a realistic receiver possessing a finite sized aperture is employed in turbulent atmospheric optics links. Employing our previously derived formulation for the power scintillation index, the variations of the power scintillations and the receiver aperture averaging factor of the focused annular and flat-topped beams are scrutinized. Receiver aperture averaging factor is deduced from the ratio of power scintillation index detected by a finite sized aperture to that obtained by a point aperture. Influence of the receiver aperture radius, the propagation length, the structure constant, the inner and the outer beam sizes for an annular type incidence, flatness parameter for a flat-topped incidence and the focusing parameter for the multi-Gaussian beam in general, on the power scintillation and the receiver aperture averaging factor are studied. It is found that for the focused multi-Gaussian beams, the effect of the receiver aperture averaging factor increases as the aperture radius increases for larger link lengths. Additionally, for the annular incidences in turbulence, the effect of the receiver aperture averaging factor is stronger for larger inner beam source sizes. At a fixed receiver aperture radius, receiver aperture averaging becomes more effective when the structure constant becomes larger. When focused multi-Gaussian beams are compared to their collimated counterparts, it is seen that the receiver aperture averaging is more beneficial for the focused annular and focused flat-topped beams. At large link lengths, increase in the receiver aperture radius decreases the power scintillations.
Citation - Scopus: 4
Atmospheric Propagation Model and Affecting On Laser Beam Propagation Via Free Space
(Optica Publishing Group (formerly OSA), 2017) Khamees, H.T.
In this article, a laser source (He-Ne) laser with maximum output power ( 2.95 mW) was used to study and analyze laser beam when the laser propagates through the atmosphere. Atmosphere layer, also the spot diameter of the laser beam can be measured. © OSA 2017.
Citation - WoS: 1
Citation - Scopus: 0
Average received intensity for optical beam of arbitrary field profile after propagation in turbulent atmosphere
(Spie-int Soc Optical Engineering, 2009) Arpali, Caglar; Baykal, Yahya; 20809; 7812
Employing our previously obtained formulation of the average received intensity for arbitrary optical beam in turbulent atmosphere, intensity patterns of already known and new source profiles are obtained. Arbitrary beam is defined as an incidence having arbitrary source field distribution which is produced by decomposing the source into pixels and assigning the related field to each pixel. For each source field originating from each pixel, incremental received field is found and the total received field is obtained by superposing the contributions from all the incremental received fields. Using the mentioned formula governing the arbitrary beam excitation in turbulence, average received intensity patterns for various types of beams such as cos-Gaussian, cosh-Gaussian, higher-order annular, flat-topped, general type and arbitrary beams are obtained. Our results can be applied in atmospheric optics communication links, reflection from rough surfaces, optical cryptography, optical imaging systems and propagation of partially coherent light.
Citation - WoS: 1
Citation - Scopus: 7
Beam Wander Characteristics of Flat-Topped, Dark Hollow, Cos and Cosh-Gaussian, J(0)- And I-0- Bessel Gaussian Beams Propagating In Turbulent Atmosphere: A Review
(Spie-int Soc Optical Engineering, 2010) Eyyuboglu, Halil T.; Baykal, Yahya; Cil, Celal Z.; Korotkova, Olga; Cai, Yangjian; 7812; 7688
In this paper we review our work done in the evaluations of the root mean square (rms) beam wander characteristics of the flat-topped, dark hollow, cos-and cosh Gaussian, J(0)-Bessel Gaussian and the I-0-Bessel Gaussian beams in atmospheric turbulence. Our formulation is based on the wave-treatment approach, where not only the beam sizes but the source beam profiles are taken into account as well. In this approach the first and the second statistical moments are obtained from the Rytov series under weak atmospheric turbulence conditions and the beam size are determined as a function of the propagation distance. It is found that after propagating in atmospheric turbulence, under certain conditions, the collimated flat-topped, dark hollow, cos-and cosh Gaussian, J(0)-Bessel Gaussian and the I-0-Bessel Gaussian beams have smaller rms beam wander compared to that of the Gaussian beam. The beam wander of these beams are analyzed against the propagation distance, source spot sizes, and against specific beam parameters related to the individual beam such as the relative amplitude factors of the constituent beams, the flatness parameters, the beam orders, the displacement parameters, the width parameters, and are compared against the corresponding Gaussian beam.
Citation - WoS: 5
Citation - Scopus: 10
Beams with arbitrary field profiles in turbulence - art. no. 652209
(Spie-int Soc Optical Engineering, 2006) Baykal, Yahya; 7812
Characteristics of optical beam incidences that have arbitrary field profiles are examined when they propagate in the turbulent atmosphere. Arbitrary source field profile is introduced by decomposing the source into incremental areas and the received field in the presence of turbulence is expressed as the summation of the fields originating from each incremental area. Intensity moments such as average intensity and the scintillation index in turbulence are formulated under such excitation. Our results correctly reduce to the well established Gaussian beam wave solutions when the arbitrary source beam is taken as the Gaussian field profile. Naturally, all the beam structures such as the higher-order single-mode, multimode, off-axis Hermite-Gaussian, Hermite-sinusoidal-Gaussian, higher-order annular, flat-topped-Gaussian beams form the special cases of our derivation. Numerical results that cover the scintillations in turbulence for various types of arbitrary beam profiles are presented. Our results for the arbitrary source field profiles can be applied in atmospheric optics telecommunication links where combination of several known beams are employed as incidence in an effort to reduce the degrading effects of turbulence. Also in the problems of reflection from rough surfaces, propagation of spatially partially coherent optical beams or double passage imaging in turbulence, our formulation can be utilized.
Citation - Scopus: 0
Ber of Annular Beams in Strong Turbulence
(Optical Society of America (OSA), 2010) Gerçekcioglu, H.; Baykal, Y.; Eyyuboglu, H.T.; 7688; 7812
Bit error rate (BER) of annular beams is found in strong turbulence. Examining effects of beam and medium parameters on BER reveals that annular beams become favorable in stronger turbulence and at smaller focal lengths. ©2010 Optical Society of America.
Citation - WoS: 6
Citation - Scopus: 7
Bit error rate analysis of MISO FSO systems
(Taylor & Francis Ltd, 2016) Gokce, Muhsin Caner; Gökçe, Muhsin Caner; Baykal, Yahya; Uysal, Murat; 28643; 7812; 124615; Elektronik ve Haberleşme Mühendisliği
Multiple-input single-output (MISO) systems are employed in free space optical (FSO) links to mitigate the degrading effects of atmospheric turbulence. In this paper, we consider a MISO FSO system with practical transmitter and receiver configuration that consists of radial laser array with Gaussian beams and a Gaussian receiver aperture function. We have employed our previously derived formulation of the power scintillation in which Huygens-Fresnel principle was employed. Therefore, we choose system parameters within the range of validity of the wave structure functions. Using the on-off keying modulation and the log-normal probability distribution function, we quantify the average bit error rate (< BER >) of laser array beams in weak turbulence. It is observed that the radial array beams at the transmitter are more advantageous than the single Gaussian beam. However, increasing the number of array beamlets to more than three seems to have negligible effects on < BER >. It is further observed that < BER > decreases when the source size, the ring radius and the receiver aperture radius increase.
Citation - WoS: 2
Bit error rates for focused general-type beams
(Electromagnetics Acad, 2009) Arpali, Serap Altay; Baykal, Yahya; 51304; 7812
Using the scintillation index of general beam formulation, bit error rate (BER) is investigated for focused Gaussian, cos-Gaussian, cosh-Gaussian and annular beams in weak atmospheric turbulence. We have employed our previously derived formulation of the scintillation index of these beams by Rytov method. Rytov method scintillation theory is known to yield accurate results for focused beams on horizontal paths under certain regions. Therefore we find the scintillation indices of the mentioned beams for the valid region. Using the log-normal distributed intensity, BER values versus signal-to-noise ratio (SNR) are calculated for Gaussian, cos-Gaussian, cosh-Gaussian and annular beams. In our study, the focal lengths (radius of curvature) of all the mentioned focused beams are equal to the propagation distance. The improvement of BER is observed for variations of propagation length, source size and wavelength of operation. Based on these parameters, BER values of Gaussian, cos-Gaussian, cosh-Gaussian and annular beams are compared. BER values we found for the focused Gaussian, cos-Gaussian, cosh-Gaussian and annular beams decrease with increasing source sizes. Likewise, BER values of focused Gaussian, cos-Gaussian, cosh-Gaussian and annular beams decrease with increasing wavelength. The focused annular beam attains the lowest BER value for small source sizes and long propagation distances. Moreover, BER for focused beams is compared with their collimated counterparts. We observe that focused beams have lower BER values than the collimated beams on horizontal paths. Our formulation can easily be extended to cover corresponding higher order beams, however in this paper we concentrate mainly on the zero order beams.
Citation - Scopus: 0
Channel Coding Theorem
(Springer Science and Business Media Deutschland GmbH, 2018) Gazi, O.; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
In this chapter, we will discuss the channel coding theorem in details. Channel coding theorem can be accepted as a milestone in electronic communication field. For this reason, it is very critical for a communication engineer to comprehend the channel coding theorem very well. In many information theory books, or in many lecture notes delivered in classes about information theory, channel coding theorem is very briefly summarized, for this reason, many readers fail to comprehend the details behind the theorem. © 2018, Springer Nature Singapore Pte Ltd.
Citation - WoS: 14
Citation - Scopus: 15
Closed form series solution of the diffraction problem of plane waves by an impedance half-plane
(Iop Publishing Ltd, 2009) Umul, Yusuf Z.; Umul, Yusuf Ziya; 42699; Elektronik ve Haberleşme Mühendisliği
The scattering problem of plane waves by an impedance half-plane is solved by using the method of separation of variables, and a closed form series expression, which separately reduces to the cases of soft and hard half-planes, is obtained. The results are investigated numerically and compared with the solutions in the literature.
Citation - Scopus: 27
Cloud Computing Investigation for Cloud Computer Networks Using Cloudanalyst
(Little Lion Scientific, 2018) Mezaal, Y.S.; Madhi, H.H.; Abd, T.; Khaleel, S.K.; 7688
In this paper, the performances of load balancing algorithms; Round Robin, Equally Spread Current Execution, and Throttled, in two workload cases, normal and burst are investigated using CloudAnalyst simulator tool. The main objective is to examine the effect of three experiments for regular and irregular normal workloads on the performance of different load balancing algorithms as well as for bursty workload. Each test has two different configurations for parametric investigations. These parametric studies can be used to analyze any electronic service provided by cloud technology vendors in any institutions, especially those offer self-reporting details for every day. © 2005 – ongoing JATIT & LLS.

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