Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/11
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Article Citation - WoS: 3Citation - Scopus: 5Design and Implementation of Spatial Correlation-Based Clustering for Multiuser Miso-Noma Systems(Institute of Electrical and Electronics Engineers Inc., 2021) Göztepe, Caner; Özbek, Berna; Karabulut Kurt, GüneşIn this letter, we propose a novel user clustering algorithm for downlink multiuser multiple-input single-output (MISO) non-orthogonal multiple access (NOMA) systems along with its implementation in a real-time testing environment. The proposed method selects the clusters by considering users' spatial channel properties against the generated orthogonal directions. This is then followed by power allocation and zero-forcing precoding steps to mitigate the interference between the selected clusters. Performance comparisons are provided in terms of both real-time tests and simulations. It is demonstrated that a notable improvement in capacity and reliability can be obtained through the proposed approach in multiuser MISO-NOMA systems with reduced complexity.Article Citation - WoS: 4Citation - Scopus: 4Electromagnetic Simulations of Mechanical Imperfections for Accelerator Cavities(Institute of Electrical and Electronics Engineers Inc., 2019) Karatay, Anıl; Yaman, FatihEffects of surface roughness and transversal cell misalignments on the performance of elliptical accelerator cavities are studied in this article. A high-beta, 9-cell elliptical cavity, whose pi-mode resonates at 3.9 GHz, is designed to investigate imperfections. The considered frequency is chosen to observe variations of fundamental accelerating cavity parameters, wake potentials, and wake impedances more clearly by using relatively small structures. Moreover, 3-cell elliptical cavities having pi-mode at 2 and 3.9 GHz are designed to confirm the 9-cell cavity results. The undesired effects caused by the considered mechanical imperfections are simulated for an ultra-relativistic bunch in the parameter scope of a realistic scenario. In particular, Huray's snowball model, which is a scattering-based surface roughness approach developed for microstrip lines, is employed to determine the effects of the surface roughness on the accelerator cavities. Surface roughness due to the fabrication process is expressed as a surface impedance, and the required equivalence between the surface roughness and surface impedance concept is achieved. Significant computational efficiency is observed by using the surface impedance concept with Huray's snowball model in the simulations. Experimental verification of certain parameters is included for an elliptical cavity having high cell-to-cell coupling at 3.9 GHz.Article Citation - WoS: 7Citation - Scopus: 10Design and Implementation of a Tem Stripline for Emc Testing(Institute of Electrical and Electronics Engineers Inc., 2014) Hilavin, Sezgin; Kuştepeli, AlpIn this paper, a stripline for radiated field immunity testing of audio/video products is designed, constructed, calibrated, and verified. Since the canonical one is only suitable for testing equipments with height less than 70 cm, there is a need of a new device which is also in compliance with EN 55020 standard for testing new large sets, like 47″ thin-film transistor liquid crystal display (TFT LCD) television sets, in the frequency range of 150 kHz-150 MHz. Increasing the height and width of testing area causes important problems in terms of field uniformity regarding the higher order modes, characteristic impedance, and reflections in addition to the room resonances and field interference sources like corners at the edges of stripline. Comprehensive numerical study is performed to overcome these problems and obtain the optimum design before the construction. Measured data show that the new stripline is in very good agreement with the specifications determined by the standards and therefore it can be used for the electromagnetic compatibility (EMC) testing.Article Citation - WoS: 19Citation - Scopus: 24Optimal Transmission Probability in Binary Molecular Communication(Institute of Electrical and Electronics Engineers Inc., 2013) Atakan, BarışMolecular communication (MC) is a promising nanoscale communication paradigm that enables nanomachines to share information by using messenger mo\-le\-cu\-les. In this paper, an expression for the achievable rate in MC is first given. Then, using this expression, an optimal transmission probability is developed to maximize the MC rate. Numerical results show that the MC rate is time-dependent and the molecules freely wandering in the medium negatively affect the MC performance. However, the proposed optimal transmission probability is shown to maximize the MC rate.Article Citation - WoS: 2Citation - Scopus: 2The Groove-Guide Oscillator(Institute of Electrical and Electronics Engineers Inc., 2011) Bechteler, Thomas F.; Aydınlık Bechteler, Ayşe SevinçThe groove guide, a low-loss waveguide consists of two separate parallel plates whose separation distance can be adjusted, thereby affecting the frequency of operation of the guide itself. The standing waves in a groove guide along the direction of propagation are commonly obtained by either total reflection at both ends or by forming a closed loop. A negative resistance has to be implemented to induce oscillations of the groove guide resonator. It is desirable to induce oscillations directly inside the groove region therefore the negative resistance must be placed inside the groove. A Gunn element was selected to provide this negative resistance. A standard heterodyne system may be realized in order to use the groove-guide oscillator for distance or permittivity measurements. The groove-guide oscillator works as an active sensor in the X-band. The accuracy with which the resonant frequency is determined depends on the bias stability of the Gunn element, the phase noise of the local oscillator, and the error of the frequency counter.Article Citation - WoS: 1Citation - Scopus: 3Euclidean Position Estimation of Static Features Using a Moving Uncalibrated Camera(Institute of Electrical and Electronics Engineers Inc., 2012) Nath, Nitendra; Dawson, Darren M.; Tatlıcıoğlu, EnverIn this paper, a novel Euclidean position estimation technique using a single uncalibrated camera mounted on amoving platform is developed to asymptotically recover the 3-D Euclidean position of static object features. The position of the moving platform is assumed to be measurable, and a second object with known 3-D Euclidean coordinates relative to theworld frame is considered to be available a priori. To account for the unknown camera calibration parameters and to estimate the unknown 3-D Euclidean coordinates, an adaptive least squares estimation strategy is employed based on prediction error formulations and a Lyapunovtype stability analysis. The developed estimator is shown to recover the 3-D Euclidean position of the unknown object features despite the lack of knowledge of the camera calibration parameters. Numerical simulation results along with experimental results are presented to illustrate the effectiveness of the proposed algorithm. © 2011 IEEE.Conference Object Citation - Scopus: 1Euclidean Position Estimation of Static Features Using a Moving Uncalibrated Camera(Institute of Electrical and Electronics Engineers Inc., 2009) Nath, Nitendra; Dawson, Darren M.; Tatlıcıoğlu, EnverIn this paper, a novel Euclidean position estimation technique using a single uncalibrated camera mounted on a moving platform is developed to asymptotically recover the three-dimensional (3D) Euclidean position of static object features. The position of the moving platform is assumed to be measurable, and a second object with known 3D Euclidean coordinates relative to the world frame is considered to be available a priori. To account for the unknown camera calibration parameters and to estimate the unknown 3D Euclidean coordinates, an adaptive least squares estimation strategy is employed based on prediction error formulations and a Lyapunov-type stability analysis. The developed estimator is proven to recover the 3D Euclidean position of the unknown object features despite the lack of knowledge of the camera calibration parameters.Article Citation - WoS: 6Citation - Scopus: 7Convolutional Bias Removal Based on Normalizing the Filterbank Spectral Magnitude(Institute of Electrical and Electronics Engineers Inc., 2007) Tüfekçi, ZekeriyaIn this letter, a novel convolutional bias removal technique is proposed. The proposed method is based on scaling the filterbank magnitude by the average of filterbank magnitude over time. The relation between the cepstral mean normalization (CMN) and proposed algorithm is derived. The experimental results show that the proposed algorithm is more robust than the CMN for both convolutional bias and additive noise. For example, the proposed method reduced the equal error rate by 5.66% and 10.16% on average for the convolutional bias and 12-dB additive noise, respectively.