Elektronik ve Haberleşme Mühendisliği Bölümü Yayın Koleksiyonu

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

Browse

Now showing 1 - 20 of 29

Citation - WoS: 0
Citation - Scopus: 2
A compact size multiband printed monopole antenna with triple sense circular polarization for wireless applications
(Natl inst Optoelectronics, 2020) Al-Mihrab, M.; Salim, A.; Al-Saedi, H.; Ali, J.
A penta-band printed monopole antenna based on a hexagonal open loop shape is presented in this paper. The proposed antenna demonstrated a variety in the polarization. Antenna is loaded with some parts and two stair-shaped slits is created in the partial ground plane for enhancing the multiband behavior. A circularly polarized (CP) waves are generated at a three bands with impedance bandwidths (IBWs) of 10.62%, 33.65% and 8.61% centered at 1.60, 5.20 and 6.50 GHz and 3-dB axial ratio bandwidths (ARBWs) of 9.10%, 7.58%, and 4.41% respectively. While a linearly polarized (LP) waves at the other two bands over ranges (2.51-2.64 GHz) and (3.10-3.31 GHz). Besides, the proposed antenna showed a different sense of circular polarization; right hand, left hand, and right hand. The antenna is simulated and fabricated on an FR-4 (glass epoxy) substrate with relative permittivity of 4.6, thickness of 1.6 mm and a loss tangent of 0.02. The properties of multiband and circular polarization, makes the proposed antenna candidates for many modern wireless applications.
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: 1
Analysis of parallel decodable turbo codes
(Ieice-inst Electronics information Communications Eng, 2012) Gazi, Orhan; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
Turbo codes suffer from high decoding latency which hinders their utilization in many communication systems. Parallel decodable turbo codes (PDTCs) are suitable for parallel decoding and hence have low latency. In this article, we analyze the worst case minimum distance of parallel decodable turbo codes with both S-random interleaver and memory collision free Row-Column S-random interleaver. The effect of minimum distance on code performance is determined through computer simulations.
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
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 - 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.
Citation - Scopus: 0
Concept of Information, Discrete Entropy and Mutual Information
(Springer Science and Business Media Deutschland GmbH, 2018) Gazi, O.; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
In this chapter, we will try to explain the concept of information, discrete entropy and mutual information in details. To master on the information theory subjects, the reader should have a knowledge of probability and random variables. For this reason, we suggest to the reader to review the probability and random variables topics before studying the information theory subjects. Continuous entropy and continuous mutual information are very closely related to discrete entropy and discrete mutual information. For this reason, the reader should try to understand very well the fundamental concepts explained in this chapter, then proceed with the other chapters of the book. © 2018, Springer Nature Singapore Pte Ltd.
Citation - WoS: 7
Citation - Scopus: 7
Cosine-Gaussian laser beam intensity in turbulent atmosphere
(Spie-int Soc Optical Engineering, 2004) Eyyuboglu, HT; Baykal, Y; 7688
The effects of turbulent atmosphere on cosine-Gaussian laser beams are examined. To this end, a cosine-Gaussian excitation is taken at the source plane, and subsequently the average intensity profile at the receiver plane is formulated. Our formulation correctly reduces to the known Gaussian beam wave result in turbulence and the cosine-Gaussian beam solution in free space (in the absence of turbulence). Variation of the average intensity profile of the receiver plane is evaluated and plotted against the variations of link length, turbulence levels, two frequently used free space optics (FSO) wavelenaths and beam displacement parameters. From these results, it is seen that cosine-Gaussian beam, following the natural diffraction, is eventually transformed into a hyperbolic-cosine Gaussian beam. Hence, the beam energy becomes concentrated around two main lobes at the receiver plane. Combining our earlier result with the findings of this paper, we conclude that cosine-Gaussian and hyperbolic-cosine-Gaussian beam act in a reciprocal manner after having C, propagated. This rneans, starting with a cosine-Gaussian beam excitation, we obtain hyperbolic-cosine-Gaussian distribution at the receiver plane, whereas hyperbolic-cosine-Gaussian beam excitation will yield a cosine-Gaussian distribution. This reciprocity is applicable both in free space and in turbulence.
Citation - WoS: 1
Citation - Scopus: 1
Determination of chemisorption probabilities of hydrogen molecules on a nickel surface by Artificial Neural Network
(Croatian Chemical Soc, 2008) Boeyuekata, Mustafa; Kocyigit, Yuecel; Guevenc, Ziya B.; 120207; 53469
Dissociative chemisorption probabilities for H-2(v, j) + Ni(100) collision systems have been estimated by using Artificial Neural Network (ANN). For training, previously determined probability values via molecular dynamics simulations have been used. Performance of the ANN, for predicting any quantities in the molecule-surface interaction, has been investigated. Effects of the surface sites and the rovibrational states of the molecule on the process are analyzed. The results are in good agreement with the related previous studies.
Citation - WoS: 20
Citation - Scopus: 33
Effect of beam types on the scintillations: A review
(Spie-int Soc Optical Engineering, 2009) Baykal, Yahya; Eyyuboglu, Halil T.; Cai, Yangjian; 7812; 7688
When different incidences are launched in atmospheric turbulence, it is known that the intensity fluctuations exhibit different characteristics. In this paper we review our work done in the evaluations of the scintillation index of general beam types when such optical beams propagate in horizontal atmospheric links in the weak fluctuations regime. Variation of scintillation indices versus the source and medium parameters are examined for flat-topped-Gaussian, cosh-Gaussian, cos-Gaussian, annular, elliptical Gaussian, circular (i.e., stigmatic) and elliptical (i.e., astigmatic) dark hollow, lowest order Bessel-Gaussian and laser array beams. For flat-topped-Gaussian beam, scintillation is larger than the single Gaussian beam scintillation, when the source sizes are much less than the Fresnel zone but becomes smaller for source sizes much larger than the Fresnel zone. Cosh-Gaussian beam has lower on-axis scintillations at smaller source sizes and longer propagation distances as compared to Gaussian beams where focusing imposes more reduction on the cosh-Gaussian beam scintillations than that of the Gaussian beam. Intensity fluctuations of a cos-Gaussian beam show favorable behaviour against a Gaussian beam at lower propagation lengths. At longer propagation lengths, annular beam becomes advantageous. In focused cases, the scintillation index of annular beam is lower than the scintillation index of Gaussian and cos-Gaussian beams starting at earlier propagation distances. Cos-Gaussian beams are advantages at relatively large source sizes while the reverse is valid for annular beams. Scintillations of a stigmatic or astigmatic dark hollow beam can be smaller when compared to stigmatic or astigmatic Gaussian, annular and flat-topped beams under conditions that are closely related to the beam parameters. Intensity fluctuation of an elliptical Gaussian beam can also be smaller than a circular Gaussian beam depending on the propagation length and the ratio of the beam waist size along the long axis to that along the short axis (i.e., astigmatism). Comparing against the fundamental Gaussian beam on equal source size and equal power basis, it is observed that the scintillation index of the lowest order Bessel-Gaussian beam is lower at large source sizes and large width parameters. However, for excessively large width parameters and beyond certain propagation lengths, the advantage of the lowest order Bessel-Gaussian beam seems to be lost. Compared to Gaussian beam, laser array beam exhibits less scintillations at long propagation ranges and at some midrange radial displacement parameters. When compared among themselves, laser array beams tend to have reduced scintillations for larger number of beamlets, longer wavelengths, midrange radial displacement parameters, intermediate Gaussian source sizes, larger inner scales and smaller outer scales of turbulence. The number of beamlets used does not seem to be so effective in this improvement of the scintillations.
Citation - Scopus: 0
Entropy for Continuous Random Variables Discrete Channel Capacity, Continuous Channel Capacity
(Springer Science and Business Media Deutschland GmbH, 2018) Gazi, O.; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
In this chapter, we will study the entropy concept for continuous random variables. The capacity of both continuous and discrete channels will be inspected in details. The capacity formula for additive white Gaussian channel is to be derived and the factors that affects the capacity of the additive white Gaussian channel will be elaborated. © 2018, Springer Nature Singapore Pte Ltd.
Citation - WoS: 5
Citation - Scopus: 9
Incoherent sinusoidal-Gaussian and annular beam scintillations
(Spie-int Soc Optical Engineering, 2008) Baykal, Yahya; Eyyuboglu, Halil T.; Cai, Yangjian; 7812; 7688
The scintillation index is evaluated in horizontal turbulent atmospheric optical links for incidences of incoherent cosh-Gaussian (IChG), cos-Gaussian (ICG) and annular (IA) beams. Weak turbulence solution is obtained for a slow detector. Dependence of the intensity fluctuations of the IChG, ICG and IA beams on the link length, source size, wavelength and the structure constant are examined. At all the link lengths, fixed size IChG and ICG beams exhibit lower scintillations for larger absolute displacement parameters. At a fixed link length, IChG beam yields lower fluctuations than the ICG beam having the same absolute displacement parameter. For the same size primary beams, IA beam with narrower ring scintillates less than the IA beam with wider ring, and this holds to be valid for each link length. Investigation of the scintillation versus the source size reveals that increase in the source size lowers the scintillations for all types of the incoherent beams. At the same source size and the same absolute displacement parameter, IChG beams have lower fluctuations than the ICG beams, larger absolute displacement parameters exhibiting lower scintillations at the same source size for both beams. For IA beams, as the size of the primary beam is increased, the scintillations are reduced for all ring sizes, the reduction being pronounced for narrower rings. As the wavelength increases, the scintillations of IChG and ICG beams first increase, then at around the wavelength forming the Fresnel zone, the scintillations start to decrease and eventually for all types of IChG and ICG beams, the scintillation indices merge towards a certain value. Similar behaviour of the scintillations versus the wavelength is observed for IA beams as well. As long as the structure constant is kept within the range of interest to remain in the weak turbulence, raising the structure constant first increases the intensity fluctuations of beams for all the mentioned beam types where further rises in the structure constant result in the same level of scintillation index. Comparison of the scintillations of IChG, ICG and IA beams with their coherent counterparts and the coherent Gaussian beam shows that the IChG, ICG and IA beams are favorable for large sized sources.
Citation - Scopus: 0
Information theory for electrical engineers
(Springer Science and Business Media Deutschland GmbH, 2018) Gazi, O.; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
Citation - WoS: 3
Citation - Scopus: 4
Intensity fluctuations for source arrays in turbulent atmosphere - art. no. 630308
(Spie-int Soc Optical Engineering, 2006) Baykal, Yahya; 7812
Intensity fluctuations are formulated for source arrays in weakly turbulent horizontal atmospheric links. Source array is composed of point sources separated by variable distances in the transverse source directions. Formula yielding the on-axis scintillation index for the source array is derived by employing the Rytov solution for the structure and correlation functions in the extended Huygens Fresnel principle. Through numerical results, variations of the scintillations versus the array parameters such as the size of the array, spacing between the array elements, amplitudes and phases of the individual sources in the array are investigated. Numerically evaluated intensity fluctuations for such array parameters are compared with the well known single point source scintillations. We are interested to understand whether the use of a source array will give favorable intensity fluctuations in atmospheric communication links.
Citation - WoS: 2
Citation - Scopus: 5
Intensity fluctuations of focused general-type beams in atmospheric optics links
(Spie-int Soc Optical Engineering, 2007) Baykal, Yahya; Eyyuboglu, Halil T.; 7812; 7688
The intensity fluctuations of focused general-type beams in weakly turbulent atmospheric links are formulated and numerically evaluated. Focused general-type beams in general cover very large range of beams, however in this work we concentrate specifically on the focused sinusoidal-Gaussian, annular and flat-topped beams. The behavior of the scintillations for these beams is examined versus the focusing distance, wavelength of operation and the source size. In our formulation, atmospheric turbulence is introduced through the Rytov method where the free space field (i.e., in the absence of turbulence) at the receiver plane for the general-type focused beam is found by utilizing the Huygens-Fresnel principle. Figures are presented showing the scintillation index for focused general-type beams and collimated general-type beams. To find out the source and medium parameters that will yield favourable scintillation levels, the intensity fluctuations of the focused sinusoidal-Gaussian, annular and flat-topped beams are compared. Within the range of selected source and medium parameters, our observations indicate that the intensity fluctuations in weak turbulence tend to be the smallest for the focused flat-topped Gaussian beams and the largest for the focused cos-Gaussian beams. Gaussian, cosh-Gaussian and annular beams experience interim level fluctuations. The comparison of the scintillation levels for the mentioned types of focused beams follow the same tendency for all the propagation distances. Also, the intensity fluctuations of the focused general-type beams in turbulence are compared with their collimated counterparts. Such a comparison reveals that for all the beams at a selected source size, the scintillations are nearly the same for both the focused and the collimated cases at all the propagation distances, except for the flat-topped Gaussian beams. When focused flat-topped Gaussian beams are employed, the intensity fluctuations seem to be lower as compared to the equivalent collimated flat-topped Gaussian beam at shorter link lengths.
Citation - Scopus: 1
Mathematical modelling of polar codes, channel combining and splitting
(Springer Science and Business Media B.V., 2019) Gazi, O.; 102896
In Chap. 2, we explained the decoding of polar codes in a clear and trivial manner. However, in most of the engineering sciences, it is critical to mathematically formulate the theories or techniques invented. © Springer Nature Singapore Pte Ltd. 2019.
Citation - Scopus: 1
Polar codes: A non-trivial approach to channel coding
(Springer Science and Business Media B.V., 2019) Gazi, O.; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
Polar codes are one of the recently discovered capacity achieving channel codes. What makes the polar codes different from other channel codes is that polar codes are designed mathematically and their performance are mathematically proven. © Springer Nature Singapore Pte Ltd. 2019.
Citation - Scopus: 0
Polarization of binary erasure channels
(Springer Science and Business Media B.V., 2019) Gazi, O.; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
In this chapter, we will demonstrate the calculation of split channel capacities when polar codes are employed for binary erasure channels. © Springer Nature Singapore Pte Ltd. 2019.

Browse

Browsing Elektronik ve Haberleşme Mühendisliği Bölümü Yayın Koleksiyonu by Scopus Q "Q4"