Elektrik - Elektronik Mühendisliği Bölümü Koleksiyonu

Permanent URI for this collectionhttps://gcris.khas.edu.tr/handle/20.500.12469/47

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Citation Count: 0
Abstraction in FPGA implementation of neural networks
(World Scientific and Engineering Academy and Society, 2008) Öğrenci, Arif Selçuk
A model for FPGA implementation of multilayer perceptron neural networks is presented. The model tries to incorporate object oriented design principles in the analysis training and design of components using hardware description languages. The synthesis will be based on the tools supplied by the FPGA vendors. The results indicate that the method can be utilized and it can be further improved to create a general methodology that bridges the gap between hardware and software in embedded system design.
Citation Count: 6
Achievable Performance of Bayesian Compressive Sensing Based Spectrum Sensing
(IEEE, 2014) Erküçük, Serhat; Erküçük, Serhat; Çırpan, Hakan Ali
In wideband spectrum sensing compressive sensing approaches have been used at the receiver side to decrease the sampling rate if the wideband signal can be represented as sparse in a given domain. While most studies consider the reconstruction of primary user's signal accurately it is indeed more important to analyze the presence or absence of the signal correctly. Furthermore these studies do not consider the achievable lower bounds of reconstruction error and how well the selected method performs correspondingly. Motivated by these issues we investigate in detail the primary user detection performance of Bayesian compressive sensing (BCS) approach in this paper. Accordingly we (i) determine the BCS signal reconstruction performance in terms of mean-square error (MSE) compression ratio and signal-to-noise ratio (SNR) and compare it with the conventionally used basis pursuit approach (ii) determine how well BCS performs compared with the Bayesian Cramer-Rao lower bound (BCRLB) of the signal reconstruction error and (iii) assess the probability of detection performance of BCS for various SNR and compression ratio values. The results of this study are important for determining the achievable performance of BCS based spectrum sensing.
Citation Count: 1
Across dimensions: Two- and three-dimensional phase transitions from the iterative renormalization-group theory of chains
(2020) Keçoğlu, İbrahim; Berker, A. Nihat
Sharp two- and three-dimensional phase transitional magnetization curves are obtained by an iterative renormalization-group coupling of Ising chains, which are solved exactly. The chains by themselves do not have a phase transition or nonzero magnetization, but the method reflects crossover from temperaturelike to fieldlike renormalization-group flows as the mechanism for the higher-dimensional phase transitions. The magnetization of each chain acts, via the interaction constant, as a magnetic field on its neighboring chains, thus entering its renormalization-group calculation. The method is highly flexible for wide application.
Citation Count: 0
Advanced signal processing algorithms for wireless communications
(Springer-Verlag Berlin, 2006) Panayırcı, Erdal; Çırpan, Hakan Ali
Traditional wireless technologies are not well suited to meet the extremely demanding requirements of providing the very high data rates with the ubiquity mobility and portability characteristic of cellular systems. Some fundamental barriers related to the nature of the radio channel as well as the limited bandwidth availability at the frequencies of interest stand in the way. Unique sets of efficient advanced signal processing algorithms and techniques is the one of the primary enablers that will allow lifting these limits primarily due to the impressive advent of low cost and low power digital signal processors. As an application of advanced signal processing techniques we will consider the solution of blind phase noise estimation and data detection problem via a computationally efficient sequential Monte Carlo (SMC) methodology in this paper.
Citation Count: 0
An Alternative Approach To Design Lumped Element Delay Equalizers
(Istanbul Univ Fac Engineering, 2015) Şengül, Metin Y.
In this paper an algorithm has been proposed to design lumped element delay equalizers which is considered as a single block as opposed to the existing methods in literature. Then after obtaining the desired delay performance the designed delay equalizer is divided and realized as cascaded first-order and/or second-order all-pass circuits. An example is given to illustrate the utilization of the proposed algorithm.
Citation Count: 0
Alternative Transducer Power Gain Expression in Broadband Matching Network Designs
(IEEE, 2016) Şengül, Metin Y.
In this paper a reflection coefficient based transducer power gain expression has been derived which is an alternative to the impedance based expression exists in the literature. A broadband double matching problem is solved by using the derived gain expression and the obtained performance has been compared with the performance obtained via the existing expression.
Citation Count: 0
Analysis and Optimization of Matching Networks-I Getting Started with ADS
(Springer-Verlag Berlin, 2008) Şengül, Metin Y.
[Abstract Not Available]
Citation Count: 0
Analysis and Optimization of Matching Networks-II Getting Started with Microwave Office
(Springer-Verlag Berlin, 2008) Şengül, Metin Y.
[Abstract Not Available]
Citation Count: 4
Analysis of Extended Busy Tone Performance for Coexistence between WRAN and WLAN TVWS Networks
(IEEE, 2015) Baykaş, Tunçer; Erküçük, Serhat; Baykaş, Tunçer
TV White Spaces indicate spectrum bands which were reserved for licensed terrestrial TV broadcasting and opened to unlicensed use under regulatory conditions. One important regulation which is common in all regulatory domains is no harmful interference is created to licensed devices. On the other hand interference between unlicensed devices is not regulated. As a result system designers developed new methods to improve coexistence between TVWS networks. Extended busy tone one of such methods is designed for coexistence between wireless regional area and wireless local area networks based on IEEE 802.22 and 802.11af standards respectively. In this paper we analyse the performance of extended busy tone at different range conditions and verify via simulations under realistic conditions. Our results indicate that the method can reduce interference considerably at intermediate distances and enable networks to operate without a significant reduction in throughput.
Citation Count: 0
Analytic solution of the Feldtkeller equation
(Elsevier GMBH Urban & Fischer Verlag, 2009) Şengül, Metin Y.
In every reflectance-based application like broadband matching circuit modeling etc. a nonlinear equation following from energy conservation the Feldtkeller equation must be solved in order to obtain real networks. In the literature however there is no analytic solution available but only numerical solutions. Consequently the resulting error depends on the accuracy of the numerical tools. In this paper an analytic solution is proposed which is based on the modified ABCD-parameters of a lossless reciprocal two-port network. An algorithm is presented and examples are included to illustrate the implementation of the analytical method. (C) 2008 Elsevier GmbH. All rights reserved.
Citation Count: 1
Anomaly Detection in Walking Trajectory
(IEEE, 2018) Öğrenci, Arif Selçuk
Analysis of the walking trajectory and the detection of anomalies in this trajectory, provide important benefits in the fields of health and security. In this work, two methods to detect anomalies in trajectories, are compared. Firstly, an unsupervised method is used where the conformance among trajectories are taken into consideration. Trajectories that deviate from others are qualified as anomalies. Secondly, the points in the trajectories are considered as a time series. Artifical neural networks performing supervised learning based on the backpropagation algorithm are used. The results are compared, and the points to be enhanced are highlighted.
Citation Count: 2
Anomaly detection in walking trajectory [Yürüyüş yörüngesinde anormallik algılama]
(Institute of Electrical and Electronics Engineers Inc., 2018) Öğrenci, Arif Selçuk
Analysis of the walking trajectory and the detection of anomalies in this trajectory provide important benefits in the fields of health and security. In this work two methods to detect anomalies in trajectories are compared. Firstly an unsupervised method is used where the conformance among trajectories are taken into consideration. Trajectories that deviate from others are qualified as anomalies. Secondly the points in the trajectories are considered as a time series. Artifical neural networks performing supervised learning based on the backpropagation algorithm are used. The results are compared and the points to be enhanced are highlighted.
Citation Count: 6
Bayesian compressive sensing for ultra-wideband channel models
(IEEE, 2012) Erküçük, Serhat; Erküçük, Serhat; Cirpan, Hakan Ali
Considering the sparse structure of ultra-wideband (UWB) channels compressive sensing (CS) is suitable for UWB channel estimation. Among various implementations of CS the inclusion of Bayesian framework has shown potential to improve signal recovery as statistical information related to signal parameters is considered. In this paper we study the channel estimation performance of Bayesian CS (BCS) for various UWB channel models and noise conditions. Specifically we investigate the effects of (i) sparse structure of standardized IEEE 802.15.4a channel models (ii) signal-to-noise ratio (SNR) regions and (iii) number of measurements on the BCS channel estimation performance and compare them to the results of l(1)-norm minimization based estimation which is widely used for sparse channel estimation. The study shows that BCS exhibits superior performance at higher SNR regions only for adequate number of measurements and sparser channel models (e. g. CM1 and CM2). Based on the results of this study BCS method or the l(1)-norm minimization method can be preferred over the other for different system implementation conditions.
Citation Count: 1
Beacons for Indoor Positioning
(IEEE, 2017) Cay, Elif; Mert, Yeliz; Bahcetepe, Ali; Akyazi, Bugra Kagan; Öğrenci, Arif Selçuk
This work aims to develop a system for the tracking and control of elderly or handicapped people in an indoor environment. We have developed both a special box using an Arduino board and a mobile application on Android to determine the location of the target based on the Bluetooth Low Energy signals transmitted by special Beacons which are placed in the area of interest. Both systems are used to determine the position of the person and to monitor any event that would cause an alert. Those events can be a long stay in a fixed position or the entry into pre-defined forbidden zones. The location data will be stored in a database for further processing. Alerts can trigger messages to be sent to local authorities and/or relatives of the people. Measurements and test results are discussed regarding their performance. It is clear that more research and development is necessary for obtaining reliable products.
Citation Count: 1
Blind-phase noise estimation in OFDM systems by sequential Monte Carlo method
(John Wiley and Sons Ltd, 2006) Panayırcı, Erdal; Çırpan, Hakan Ali; Moeneclaey, Marc; Noels, Nele
One of the main drawbacks of orthogonal frequency division multiplexing (OFDM) systems is the phase noise (PN) caused by the oscillator instabilities. Unfortunately due to the PN the most valuable feature namely orthogonality between the carriers is destroyed resulting in a significant degradation in the performance of OFDM systems. In this paper based on a sequential Monte Carlo method (particle filtering) a computationally efficient algorithm is presented for estimating the residual phase noise blindly generated at the output of the phase tracking loop employed in OFDM systems. The basic idea is to treat the transmitted symbols as 'missing data' and draw samples sequentially of them based on the observed signal samples up to time t. This way the Bayesian estimates of the phase noise is obtained through these samples sequentially drawn together with their importance weights. The proposed receiver structure is seen to be ideally suited for highspeed parallel implementation using VLSI technology. The performance of the proposed approaches are studied in terms of average mean square error. Through experimental results the effects of an initialisation on the tracking performance are also explored. Copyright (c) 2006 AEIT.
Citation Count: 6
Bound free electron-positron pair production accompanied by giant dipole resonances
(Amer Physical Soc., 2011) Şengül, Metin Y.; Guclu, Mehmet C.
At the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) for example virtual photons produce many particles. At small impact parameters where the colliding nuclei make peripheral collisions photon fluxes are very large and these are responsible for the multiple photonuclear interactions. Free pair productions bound free pair productions and nuclear Coulomb excitations are important examples of such interactions and these processes play important roles in the beam luminosity at RHIC and LHC. Here we obtained the impact parameter dependence of bound free pair production cross sections and by using this probability we obtained bound free electron-positron pair production with nuclear breakup for heavy ion collisions at RHIC and LHC. We also compared our results to the other calculations.
Citation Count: 0
Broadband double-matching via lossless unsymmetrical lattice networks
(Istanbul University, 2012) Şengül, Metin Y.
In this paper a broadband double-matching network design algorithm has been presented. In the network an unsymmetrical lattice network has been used. The branch impedances of the lattice network are composed of singly terminated lossless LC networks. After giving the procedure its usage has been illustrated via an example.
Citation Count: 1
Broadband impedance matching via lossless unsymmetrical lattice networks
(Elsevier GMBH Urban & Fischer Verlag, 2012) Şengül, Metin Y.
In this paper a broadband impedance matching network (equalizer) design algorithm has been proposed. In the equalizer a lossless unsymmetrical lattice network has been utilized. The branch impedances of the lattice network are considered as singly terminated lossless LC networks since it is not desired to dissipate power in the equalizer. After giving the algorithm its usage has been illustrated via an example. (C) 2011 Elsevier GmbH. All rights reserved.
Citation Count: 0
Broadband Matching via Reflection Coefficient Modeling
(AVES YAYINCILIK, 2016) Şengül, Metin Y.
[Abstract Not Available]
Citation Count: 5
A broadband microwave amplifier design by means of immittance based data modelling tool
(IEEE, 2002) Kilinç, Ali; Pinarbaşi, Haci; Şengül, Metin Y.; Yarman, Sıddık Binboğa
In this paper a practical broadband microwave amplifier design algorithm is introduced utilizing the immittance data-modelling tool. In the course of design first the optimum input and output terminations for the active device are produced employing the real frequency technique. Then these terminations are modelled utilizing the new immittance-modelling tool to synthesize the front-end and back-end matching networks. An example is included to exhibit the implementation of the proposed design algorithm to construct a single stage BJT amplifier over a wide frequency band. It is expected that the proposed design algorithm will find applications to realize wideband microwave amplifiers put on MMIC for mobile communication.

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