Elektronik ve Haberleşme Mühendisliği Bölümü

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Citation Count: Al-Mihrab, M...at all (2020). "A compact size multiband printed monopole antenna with triple sense circular polarization for wireless applications", Journal of Optoelectronics and Advanced Materials, Vol. 22, No. 9-10, pp. 483-494.
A compact size multiband printed monopole antenna with triple sense circular polarization for wireless applications
(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 Count: Umul, Yusuf Ziya, "A new approach to the Dirac equation", Optik, Vol. 181, pp. 524-527, (2019).
A new approach to the Dirac equation
(Elsevier GMBH, 2019) Umul, Yusuf Ziya; 42699
Dirac equation is based on a novel method that expresses the roots of a square-root operation in terms of matrices. Instead of this technique we propose an alternative approach. The square-root expression is represented as a hypotenuse and it is written in terms of a trigonometric summation of the remaining two edges of a right-angle triangle. Both of the positive and negative energy terms are taken into account and a new matrix equation is obtained. The plane wave solutions of the new differential equation are studied.
Citation Count: Umul, Yusuf Ziya (2021). "A new series solution associated with the quantum harmonic oscillator", Optik, Vol. 25.
A new series solution associated with the quantum harmonic oscillator
(2021) Umul, Yusuf Ziya; 42699
In the non-relativistic case, the problem of quantum harmonic oscillator is solved by the aid of the Schro spacing diaeresis dinger equation. An additional term of potential energy that is related with the square of the spatial coordinate is also included in the equation. A second order linear differential equation is obtained in the stationary state. The direct solution gives the wave function in terms of the parabolic cylinder functions. This solution leads to the Hermite polynomials when the quantization of energy is considered. However, the derived expression of the wave function does not yield the correct functions for the limiting case, in which the potential energy is zero. We put forth an alternative solution for the second order linear differential equation. First of all, a new series expression is suggested as an ansatz for the power series solution of differential equations. The coefficients of the series are obtained in terms of recurrence relations. Some computational simulations are given.
Citation Count: Humada, A.M...et al. "A Proposed Method of Photovoltaic Solar Array Configuration Under Different Partial Shadow Conditions", Advanced Materials Research, Vol 933, pp. 307-311, (2014).
A Proposed Method of Photovoltaic Solar Array Configuration Under Different Partial Shadow Conditions
(Trans Tech Publications LTD, 2014) Humada, Ali Mahmood; Hojabri, Mojgan; Mohamed, Mortaza B.; Herwan Bin Sulaiman, Mohd; Dakheel, Taha Hamad
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
Citation Count: Abdulkhaleq, Nadhir Ibrahim; Gazi, Orhan, "A sequential coding approach for short length lt codes over awgn channel", 2017 4th International Conference On Electrical And Electronic Engineering (ICEEE 2017), pp. 267-271, (2017).
A sequential coding approach for short length lt codes over awgn channel
(IEEE, 2017) Abdulkhaleq, Nadhir Ibrahim; Gazi, Orhan; 102896
Luby Transform (LT) codes which can be considered as one of the first type of rate less codes are introduced to be an efficient erasure code. In such codes a fountain of encoded symbols is continuously transmitted until the successfully delivery of all the data packets. Whenever the receiver collects N noisy encoded symbols the decoding operation starts. Usually belief propagation (BP) algorithm is used to decipher the code and extract the k data symbols. In this paper, short length LT codes are generated using efficient sequential encoding approach (SEA) and performance measurements have been done over additive white Gaussian (AWGN) channel. This coding technique generates its degree in a repeated sequential manner which yields a mutual relation between adjacent codes that will be used in the decoding part. The decoding complexity of the proposed structure is similar to that of the Raptor codes. The simulation results show that the proposed approach has better performance in terms of error floor and successful decoding ratio when compared to LT codes using robust soliton distribution (RSD) and memory-based-RSD (MBRSD) even when supported by belief propagation-pattern recognition (BP-PR) technique.
Citation Count: Umul, Yusus Ziya, "A survey of the new proposal about the photon momentum", Optik, Vol.148, pp.342-343, (2017).
A survey of the new proposal about the photon momentum
(Elsevier GMBH, 2017) Umul, Yusuf Ziya; 42699
Bahadoran et al. [1] proposed that the new approach to photon momentum, introduced by Umul [2], was not correct, because they obtained a negative energy expression for the absorbed photon. In this comment, we show that this proposal is wrong, since the related authors made a mistake in their derivations.
Citation Count: Umul, Yusuf Ziya, "A survey on Klein paradox", Optik, Vol. 181, pp. 258-263, (2019).
A survey on Klein paradox
(Elsevier GMBH, 2019) Umul, Yusuf Ziya; 42699
The solution of the relativistic tunneling problem with the aid of the Klein-Gordon and kinetic energy based wave equations are reviewed. The behaviors of the transmitted and reflected wave functions by the potential barrier are studied for different values of the barrier's energy. The reason of the Klein's paradox is put forth in terms of the structures of the wave equations.
Citation Count: Gazi, Orhan. "A Tutorial Introduction to VHDL Programming", Singapore: Springer, pp. 1-251, 2019.
A Tutorial Introduction to VHDL Programming
(Springer, 2019) Gazi, Orhan; 102896
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.
Citation Count: Özaydın, S. (2018). "Acoustic and Linguistic Properties of Turkish Whistle Language", Open Journal of Modern Linguistics, Vol.8, No.4.
Acoustic and Linguistic Properties of Turkish Whistle Language
(2018) Özaydın, Selma; 253019
This paper presents the acoustic and linguistic properties of Turkish Whistle Language. Whistle Language is a natural communication method usually used for far-distance interaction in some regions in the world. In a whistled speech, auditory features of spoken languages are transposed. Therefore, whistle languages carry some properties of vocal speech with its own vocabulary, grammar, phonology and prosodic features. There are a few places in the world using this whistled communication style and Kuskoy region in Turkey is one of them. Although there are some researches on Turkish Whistle Language, unfortunately there have been a limited number of scientific publications in the literature. On the other hand, the research results present very stunning results such as people can still continue articulating some words while whistling and there is a high understandability rate while communicating. Therefore, it is described as an incomplete form of Turkish Language. The research results also indicate that Turkish Whistle Language is a non-tonal language transposing formants and therefore it can be used to evaluate the formant changes in the transform of a language. These research results indicate many other valuable properties of Turkish whistle language. But, unfortunately there has not been a collective study combining all these properties. Besides, there are still unclear and conflicted points in the literature as can be implied in this paper. This study aims to bring together the research results to underline the distinct features of Turkish Whistle Language and to motivate researchers to go forward on this subject. The paper is mainly focused on acoustic and phonetic properties of Turkish Whistle Language. Historical or cultural based details are out of the scope of this study.
Citation Count: Umul, Yusuf Ziya (2021). "Airy-type relativistic matter wave", Optik, Vol. 247.
Airy-type relativistic matter wave
(2021) Umul, Yusuf Ziya; 4269
A new relativistic Airy-type matter wave is introduced as a solution of the kinetic energy based wave equation. The parametric solution of the related differential equation is obtained. The total energy and momentum of the relativistic particle are derived by using a Bohmian type of decomposition of the kinetic energy based equation. The acceleration of the particle is also evaluated. The behavior of the matter wave is investigated numerically. © 2021 Elsevier GmbH
Citation Count: Basdemir, Husnu Deniz, "An analytical solution for the plane wave diffraction by a resistive half-plane residing at the interface of left and right handed media", Optik, Vol. 191, pp. 109-115, (2019).
An analytical solution for the plane wave diffraction by a resistive half-plane residing at the interface of left and right handed media
(Elsevier GMBH, 2019) Başdemir, Hüsnü Deniz; 20399
The diffraction of waves by a resistive half-plane lying on the interface of left and right handed media is investigated in this study. Because of the anomalous refraction property of left handed media, shadow boundary shifts toward to the lower surface of the half-plane. In order to obtain the shifted boundary, diffracted waves are divided to subfields. Thus, obtained diffracted waves compensates the deficiency of geometries optics fields at the transition regions. The uniform version of waves is obtained by using the uniform theory of diffraction. The wave behaviors are examined numerically.
Citation Count: Özaydın, Selma, "An isolated word speaker recognition system", 2017 International Conference On Electrical And Computing Technologies And Applications (ICECTA), pp.70-74, (2017).
An isolated word speaker recognition system
(IEEE, 2017) Özaydın, Selma; 253019
The paper presents a design of an isolated word speaker recognizer system by using the Hidden Markov Model. HTK toolkit is used as a design tool. The system is operated on a closed set of speakers and with a limited vocabulary of words. Digit utterances from one to ten with ten speakers (7 male, 3 female) are used as dataset in the system. It consists of isolated words that are separated by silences. Each speaker reads each word ten times. Six of them are used in training and the remaining are used in the test phase. The Mel cepstral coefficients are used in order to design the acoustic features and HMM models are constructed. A threshold calculation is performed for each speaker. After threshold adjustment, tests are performed for the performance evaluation and accuracy rates are calculated for each user. The system resulted in changing levels of recognition accuracy for each speaker and each word.
Citation Count: Şafak, A; Preveze, B., "Analysis of delay factors for voice over WiMAX", 23rd International Symposium On Computer And Information Sciences, (2008).
Analysis of delay factors for voice over WiMAX
(IEEE, 2008) Şafak, A.; Preveze, B.; 17573
This paper presents the results of our computer simulation for delays experienced by voice packets over WiMAX 802.16e protocol running over an enterprise packet network connected to public internet. In the simulation we analyzed the effect of packet size, core network link speed, internet service provider link speed, wireless network link speed, wireless distance, base station range, and distance in internet parameters that effect the amount of delay in a WiMAX embedded IP network. In this study, all the delay parameters are fixed to their default values and current parameter values are changed so that the delay is varied between minimum and maximum values in uniformly distributed 100 steps and the delay is plotted in each step. Total fixed delays can be considered as minimum delay and variable delay corresponds to the maximum delay that can occur under the given conditions. All other fixed and variable delay parameters such as switching delays, packetization delays, contention delays and the delays caused by buffers etc. are also taken into account. The results indicate that among these delays WiMAX base station range and the number of base stations play the most decisive role.
Citation Count: Elmabruk, Kholoud; Eyyuboglu, Halil T., "Analysis of flat-topped Gaussian vortex beam scintillation properties in atmospheric turbulence", Spie-Soc Photo-Optical Instrumentation Engineers, Vol. 58, No. 6, (2019).
Analysis of flat-topped Gaussian vortex beam scintillation properties in atmospheric turbulence
(Spie-Soc Photo-Optical Instrumentation Engineers, 2019) Elmabruk, Kholoud; Eyyuboğlu, Halil T.
We analyze the scintillation properties of a flat-topped Gaussian vortex beam propagating in a weakly turbulent atmosphere. We utilize a random phase screen model to perform this analysis. We evaluate the scintillation against the changes of topological charge, beam order, operating wavelength, receiver aperture side length, and source size parameters. The results show that using a flat-topped Gaussian vortex beam with a high topological charge causes a reduction in scintillation. Increasing the receiver aperture side length reduces scintillation level. As the source size increases, scintillation decreases. Our results also indicate that a flat-topped Gaussian vortex beam with high topological charges has less scintillation than the fundamental Gaussian beam. We believe that our findings will be useful in improving the performance of next-generation optical communication links and networks. (C) 2019 Society of Photo-Optical Instrumentation Engineers (SPIE)
Citation Count: Eyyuboğlu, Halil T.; Baykal, Yahya, "Analysis of laser multimode content on the angle-of-arrival fluctuations in free-space optics access systems", Optical Engineering, Vol.44, No.5, (2005).
Analysis of laser multimode content on the angle-of-arrival fluctuations in free-space optics access systems
(Spie-Soc Photo-Optical Instrumentation Engineers, 2005) Eyyuboğlu, Halil T.; Baykal, Yahya; 7688; 7812
The effects of laser beam multimode content on the angle-of-arrival fluctuations are examined for free-space optics (FSO) access systems. Multimode excitation is represented by coherent addition of Hermite-Gaussian modes. Mean square angle-of-arrival fluctuations are formulated using our previously reported multimode phase structure function. Numerical evaluations are obtained for practical FSO links operating at 1.55- and 0.85-mu m wavelengths with link spans of up to 5 km. Mode content is arranged by sequentially grouping all possible mode combinations starting from the single fundamental mode (TEM00) up to a certain higher order (n,m). Angle-of-arrival fluctuations are found to be of the order of several tens of microradians, except for the cases when the mode group terminates with an odd mode or when the extremely higher order modes are present. In these instances, the fluctuations will rise to the radian level. From these results, it is concluded that the performance of a practical FSO receiver, having a field of view of several milliradians, will not be substantially affected by the angle-of-arrival fluctuations due to multimode excitation, provided that the mode content of source excitation is confined to mode indices below 20.
Citation Count: Eyyuboğlu, Halil T.; Baykal, Y., "Analysis of reciprocity of cos-Gaussian and cosh-Gaussian laser beams in a turbulent atmosphere", Optics, Express, Vol.12, No.20, pp.4659-4674, (2004).
Analysis of reciprocity of cos-Gaussian and cosh-Gaussian laser beams in a turbulent atmosphere
(Optical Soc Amer, 2004) Eyyuboğlu, Halil T.; Baykal, Yahya; 7688; 7812
In a turbulent atmosphere, starting with a cos-Gaussian excitation at the source plane, the average intensity profile at the receiver plane is formulated. This average intensity profile is evaluated against the variations of link lengths, turbulence levels, two frequently used free-space optics wavelengths, and beam displacement parameters. We show that a cos-Gaussian beam, following a natural diffraction, is eventually transformed into a cosh-Gaussian beam. Combining our earlier results with the current findings, we conclude that cos-Gaussian and cosh-Gaussian beams act in a reciprocal manner after propagation in turbulence. The rates (paces) of conversion in the two directions are not the same. Although the conversion of cos-Gaussian beams to cosh-Gaussian beams can happen over a wide range of turbulence levels (low to moderate to high), the conversion of cosh-Gaussian beams to cos-Gaussian beams is pronounced under relatively stronger turbulence conditions. Source and propagation parameters that affect this reciprocity have been analyzed.
Citation Count: Eyyuboğlu, Halil Tanyer, 'Analysis of wave structure functions' LFNM 2008: Proceedings Of The 9th International Conference On Laser And Fiber-Optical Network Modeling, pp.107-109, (2008).
Analysis of wave structure functions
(IEEE, 2008) Eyyuboğlu, 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 Count: Eyyuboğlu, Halil Tanyer; Baykal, Yahya, "Angle-of-arrival fluctuations for general-type beams", Optical Engineering, Vol.46, No.9, (2007).
Angle-of-arrival fluctuations for general-type beams
(Spie-Soc Photo-Optical Instrumentation Engineers, 2007) Eyyuboğlu, Halil T.; Baykal, Yahya; 7688; 7812
Starting with the recently introduced phase correlation function of a general-type beam, the angle-of-arrival fluctuations are derived and evaluated in atmospheric turbulence for lowest-order Gaussian, cos-Gaussian, cosh-Gaussian, annular, and flat-topped beams. Our motivation is to examine the improvement in the performance of optical atmospheric links when such beams are employed. For these beams, the dependence of the angle-of-arrival fluctuations on the propagation length, displacement and focusing parameters, source size, inner and outer scales of turbulence, and receiver radius is investigated. It is found that in the majority of the cases examined, the angle- of- arrival fluctuations remain small and hence are not expected to adversely affect the operation of free-space atmospheric links. It is observed that amongst the beams considered, the cos-Gaussian beam offers the least amount of angle-of-arrival fluctuations, while the worst behavior is exhibited by the cosh-Gaussian beam. This situation is reversed, however, if focused beams are used.
Citation Count: Eyyuboğlu, H.T. (2015). Apertured averaged scintillation of fully and partially coherent Gaussian, annular Gaussian, flat toped and dark hollow beams. Optics Communications, 339, 141-147. http://dx.doi.org/10.1016/j.optcom.2014.11.070
Apertured averaged scintillation of fully and partially coherent Gaussian, annular Gaussian, flat toped and dark hollow beams
(Elsevier Science Bv., 2015) Eyyuboğlu, Halil T.; 7688
Apertured averaged scintillation requires the evaluation of rather complicated irradiance covariance function. Here we develop a much simpler numerical method based on our earlier introduced semianalytic approach. Using this method, we calculate aperture averaged scintillation of fully and partially coherent Gaussian, annular Gaussian flat topped and dark hollow beams. For comparison, the principles of equal source beam power and normalizing the aperture averaged scintillation with respect to received power are applied. Our results indicate that for fully coherent beams, upon adjusting the aperture sizes to capture 10 and 20% of the equal source power, Gaussian beam needs the largest aperture opening, yielding the lowest aperture average scintillation, whilst the opposite occurs for annular Gaussian and dark hollow beams. When assessed on the basis of received power normalized aperture averaged scintillation, fixed propagation distance and aperture size, annular Gaussian and dark hollow beams seem to have the lowest scintillation. Just like the case of point-like scintillation, partially coherent beams will offer less aperture averaged scintillation in comparison to fully coherent beams. But this performance improvement relies on larger aperture openings. Upon normalizing the aperture averaged scintillation with respect to received power, fully coherent beams become more advantageous than partially coherent ones.
Citation Count: Kim, Sung W...et al., "Applications of Cognitive Radio Networks: Recent Advances and Future Directions", International Journal of Distributed Sensor Networks, (2016).
Applications of Cognitive Radio Networks: Recent Advances and Future Directions
(Sage Publications LTD, 2016) Kim, Sung W.; Pan, Miao; Joshi, Gyanendra Prasad; Gazi, Orhan; He, Jianhua; Coupechoux, Marceau; 102896

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Browsing Elektronik ve Haberleşme Mühendisliği Bölümü by Department "Çankaya Üniversitesi, Mühendislik Fakültesi, Elektronik ve Haberleşme Mühendisliği Bölümü"