Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/11
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Article Citation - WoS: 5Citation - Scopus: 5Steady-State Analysis of Nonlinearly Coupled Chua's Circuits With Periodic Input(World Scientific Publishing Co. Pte Ltd, 2003) Savacı, Ferit Acar; Yalçın, M. E.; Güzeliş, CüneytIn this paper, nonlinearly coupled identical Chua's circuits, when driven by sinusoidal signal have been analyzed in the time-domain by using the steady-state analysis techniques of piecewise-linear dynamic systems. With such techniques, it has become possible to obtain analytical expressions for the transfer functions in terms of the circuit parameters. The proposed system under consideration has also been studied by analog simulations of the overall system on a hardware realization using off-the-shelf components as well as by a time-domain analysis of the synchronization error.Article Citation - WoS: 97Analysis and Suppression of Nonlinear Frequency Modulation in an Optical Frequency-Domain Reflectometer(The Optical Society, 2009) Yüksel, Kıvılcım; Wuilpart, Marc; Mégret, PatriceA new method for monitoring the nonlinearities perturbing the optical frequency sweep in high speed tunable laser sources is presented. The swept-frequency monitoring system comprises a Mach-Zehnder interferometer and simple signal processing steps. It has been implemented in a coherent optical frequency domain reflectometer which allowed to drastically reduce the effects of nonlinear sweep, resulting to a spatial resolution enhancement of 30 times. © 2009 Optical Society of America.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: 4Citation - Scopus: 4Phase Dependence Mitigation for Autocorrelation-Based Frequency Estimation(Elsevier Ltd., 2008) Altınkaya, Mustafa Aziz; Anarım, Emin; Sankur, BülentThe sinusoidal frequency estimation from short data records based on Toeplitz autocorrelation (AC) matrix estimates suffer from the dependence on the initial phases of the sinusoid(s). This effect becomes prominent when the impact of additive noise vanishes, that is at high signal-to-noise ratios (SNR). Based on both analytic derivation of the AC lag terms and simulation experiments we show that data windowing can mitigate the limitations caused by the phase dependence. Thus with proper windowing, the variance of the frequency estimate is no more eclipsed by phase dependence, but it continues to decrease linearly with increasing SNR. The study covers both the cases of a single sinusoid and two sinusoids closely spaced in the frequency with the Pisarenko frequency estimator, MUSIC and principal component autoregressive frequency estimators. The trade-offs between the spectral broadening and the achieved minimum variance level due to the data window are analyzed in detail.Article Citation - WoS: 6Citation - Scopus: 7Reconstruction of Nonstationary Signals Along the Wavelet Ridges(World Scientific Publishing Co. Pte Ltd, 2006) Özkurt, Nalan; Savacı, Ferit AcarIn this paper, the nonstationary signals have been recovered using the skeleton along the wavelet ridges in the noisy case and the attractors of the cleaned signals are reconstructed in the phase space by time-delay embedding. In order to verify the signal recovery and reconstruction procedure, the similarity measure Hausdorff distance between cleaned, noise-free original attractors have been calculated. The computations show that the procedure reduces the noise level acceptably and the reconstructed attractors are more similar to the original attractors.Article Citation - WoS: 4Citation - Scopus: 5The Implementation of Nonlinear Dynamical Systems With Wavelet Network(Urban und Fischer Verlag GmbH und Co. KG, 2006) Özkurt, Nalan; Savacı, Ferit AcarA dynamic wavelet network circuit implementation for modelling the nonlinear dynamical networks has been proposed in this study. The dynamical wavelet network includes static wavelet network with Mexican hat wavelet function, the voltage-controlled switches and capacitors. The circuit simulations have been done in Spice for the period-1 limit cycle, the spiral and double scroll attractors of the Chua's circuit.Article Citation - WoS: 12Citation - Scopus: 15Harmonic Balance Analysis of the Generalized Chua's Circuit(World Scientific Publishing Co. Pte Ltd, 2006) Savacı, Ferit Acar; Günel, SerkanIn this paper, the harmonic balance analysis of Generalized Chua's circuit exhibiting n-scroll attractors has been accomplished. The dual-input describing functions of the piecewise-linear characteristics of Chua's diode have been obtained and based on the harmonic balance principle, the existence and the locations of the n-scrolls have been verified.Article Citation - WoS: 2Citation - Scopus: 3The System Modelling and Circuit Implementation From Time-Frequency Domain Signal Specifications(Urban und Fischer Verlag GmbH und Co. KG, 2008) Savacı, Ferit Acar; Özkurt, NalanThe system modelling and the circuit implementation of the nonlinear circuits using the wavelet domain techniques has been accomplished in this study. When the time-frequency domain specifications have been given as the wavelet ridges, the signal with the given ridges has been synthesized. Then, the dynamical wavelet network has been trained for the synthesized signal. The circuit of the wavelet network has been designed and simulated. © 2007 Elsevier GmbH. All rights reserved.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.Article Citation - WoS: 5Citation - Scopus: 5The Circuit Realization of Mexican Hat Wavelet Function(Urban und Fischer Verlag GmbH und Co. KG, 2005) Özkurt, Nalan; Savacı, Ferit Acar; Gündüzalp, MustafaA wavelet network circuit implementation for Mexican Hat mother wavelet has been proposed for nonlinear function approximation which can also be used for the realization of the algebraic nonlinear components. The Mexican Hat mother wavelet function has been implemented with discrete circuit components and it has been observed that the experimental waveform obtained from the realized circuit is approximately same as the Spice simulation of the original function. The circuit simulations of exemplar functions implemented in Spice are also given. © 2004 Elsevier GmbH. All rights reserved.