Browsing by Subject "Spurious signal noise"

Now showing 1 - 16 of 16

Open Access
Adaptive filtering approaches for non-Gaussian stable processes
(IEEE, 1995-05) Arıkan, Orhan; Belge, Murat; Çetin, A. Enis; Erzin, Engin
A large class of physical phenomenon observed in practice exhibit non-Gaussian behavior. In this paper, α-stable distributions, which have heavier tails than Gaussian distribution, are considered to model non-Gaussian signals. Adaptive signal processing in the presence of such kind of noise is a requirement of many practical problems. Since, direct application of commonly used adaptation techniques fail in these applications, new approaches for adaptive filtering for α-stable random processes are introduced.
Open Access
Adaptive filtering for non-gaussian stable processes
(IEEE, 1994) Arıkan, Orhan; Çetin, A. Enis; Erzin, E.
A large class of physical phenomenon observed in practice exhibit non-Gaussian behavior. In this letter, a-stable distributions, which have heavier tails than Gaussian distribution, are considered to model non-Gaussian signals. Adaptive signal processing in the presence of such a noise is a requirement of many practical problems. Since direct application of commonly used adaptation techniques fail in these applications, new algorithms for adaptive filtering for α-stable random processes are introduced.
Open Access
AlGaN/GaN HEMT-based fully monolithic X-band low noise amplifier
(Wiley, 2005-04) Schwindt, R.; Kumar, V.; Aktas, O.; Lee, J. W.; Adesida, I.
A fully monolithic AlGaN/GaN HEMT-based low noise amplifier is reported. The circuit demonstrated a noise figure of 3.5 dB, gain of -7.5 dB, input return loss of -7.5 dB, and output return loss of -15 dB at 8.5 GHz. The dc characteristics of individual 0.25-μm × 150-μm transistors were: maximum current density of 1.0 A/mm, maximum transconductance of 170 mS/mm and a threshold voltage of -6.8 V. The devices have a typical short circuit current gain cutoff frequency of 24.5 GHz and a maximum oscillating frequency of 48 GHz. The devices demonstrated a minimum noise figure of 1.6 dB with an associated gain of 10.6 dB at 10 GHz.
Open Access
Binary sequences with low aperiodic autocorrelation for synchronization purposes
(IEEE, 2003) Kocabaş, Ş. E.; Atalar, Abdullah
An evolutionary algorithm is used to find three sets of binary sequences of length 49-100 suitable for the synchronization of digital communication systems. Optimization of the sets are done by taking into consideration the type of preamble used in data frames and the phase-lock mechanism of the communication system. The preamble is assumed to be either a pseudonoise (PN) sequence or a sequence of 1's. There may or may not be phase ambiguity in detection. With this categorization, the first set of binary sequences is optimized with respect to aperiodic autocorrelation which corresponds to the random (PN) preamble without phase ambiguity case. The second and third sets are optimized with respect to a modified aperiodic autocorrelation for different figures of merit corresponding to the predetermined preamble (sequence of 1's) with and without phase ambiguity cases.
Open Access
Filtering in fractional Fourier domains and their relation to chirp transforms
(IEEE, 1994-04) Özaktaş, Haldun M.; Barshan, Billur; Onural, Levent; Mendlovic, D.
Fractional Fourier transforms, which are related to chirp and wavelet transforms, lead to the notion of fractional Fourier domains. The concept of filtering of signals in fractional domains is developed, revealing that under certain conditions one can improve upon the special cases of these operations in the conventional space and frequency domains. Because of the ease of performing the fractional Fourier transform optically, these operations are relevant for optical information processing.
Open Access
Improvement of face detection algorithms for news videos
(IEEE, 2005) Ikizler, Nazlı; Duygulu, Pınar
People are the most important subjects in news videos and for proper retrieval of person images, face detection is a very crucial step. However, face detection and recognition in news videos is a very challenging task due to the huge irregularities and high noise level in the data. This study presents a method that combines skin detection and Schneiderman-Kanade face detection, for improving the face detection performance in news videos for a better retrieval. This method has been tested on TRECVID 2003 dataset and the results are very promising. © 2005 IEEE.
Open Access
Line spectral frequency representation of subbands for speech recognition
(1995) Erzin, E.; Çetin, A.E.
In this paper, a new set of speech feature parameters is constructed from subband analysis based Line Spectral Frequencies (LSFs). The speech signal is divided into several subbands and the resulting subsignals are represented by LSFs. The performance of the new speech feature parameters, SUBLSFs, is compared with the widely used Mel Scale Cepstral Coefficients (MELCEPs). SUBLSFs are observed to be more robust than the MELCEPs in the presence of car noise. © 1995.
Open Access
Location and curvature estimation of "spherical" targets using a flexible sonar configuration
(IEEE, 1996) Barshan, Billur
A novel, flexible, three-dimensional (3-D) multi-sensor sonar system is employed to localize the center of a spherical target and estimate its radius of curvature. The interesting limiting cases for the problem under study are the point and planar targets, both of which are important for the characterization of a mobile robot's environment. A noise model is developed based on real sonar data. An extended Kalman filter (EKF) which incorporates the developed noise model is employed as an estimation tool for optimal processing of the sensor data. Simulations and experimental results are provided for specularly reflecting cylindrical targets.
Open Access
Map building with multiple range measurements using morphological surface profile extraction
(IEEE, Piscataway, NJ, United States, 1999) Barshan, B.; Başkent, D.
A novel method is described for surface profile extraction based on morphological processing of multiple range sensor data. The approach taken is extremely flexible and robust, in addition to being simple and straightforward. It can deal with arbitrary numbers and configurations of range sensors as well as synthetic arrays. The method has the intrinsic ability to suppress spurious readings, crosstalk, and higher-order reflections, and process multiple reflections informatively. The essential idea of this work - the use of multiple range sensors combined with morphological processing - can be applied to different physical modalities of range sensing of vastly different scales and in many different areas. These may include radar, sonar, robotics, optical sensing and metrology, remote sensing, ocean surface exploration, geophysical exploration, and acoustic microscopy.
Open Access
Morphological surface profile extraction from multiple sonars
(IEEE, 1998) Başkent, Deniz; Barshan, Billur
This paper presents a novel method for surface profile determination using multiple sensors. Our approach is based on morphological processing techniques to fuse the range data from multiple sensor returns in a manner that directly reveals the target surface profile. The method has the intrinsic ability of suppressing spurious readings due to noise, crosstalk, and higher-order reflections, as well as processing multiple reflections informatively. The algorithm is verified both by simulations and experiments in the laboratory by processing real sonar data obtained from a mobile robot. The results are compared to those obtained from a more accurate structured-light system, which is however more complex and expensive.
Open Access
Moving object detection in video by detecting non-Gaussian regions in subbands and active contours
(IEEE, 2003-09) Gök, M. Y.; Çetin, A. Enis
A multi-stage moving object detection algorithm in video is described in this paper. First, the camera motion is eliminated by motion compensation. An adaptive subband decomposition structure is then used to analyze the difference image. In the high-band subimages, moving objects which produce outliers are detected using a statistical test determining non-Gaussian regions. It turns out that the distribution of the subimage pixels is almost Gaussian in general. But, at the object boundaries the distribution of the pixels in the subimages deviates from Gaussianity due to the existence of outliers. Regions containing moving objects in the original image frame are detected by detecting regions containing outliers in subimages. Finally, active contours are initiated in these regions in the wavelet domain and object boundaries are accurately estimated.
Open Access
Online exercise ECG signal orthogonalization
(1996) Acar, B.; Köymen H.
In this paper an efficient method of making use of the redundancy in standard 12 lead ECG signals to eliminate noise is described. The method is based on orthogonalization via online Singular Value Decomposition (SVD). Its application as a filter to remove EMG noise and baseline wander are explained. A comparative study of ST analysis results of original and processed exercise ECG data is reported.
Open Access
Optimal filtering in fractional Fourier domains
(IEEE, 1995) Kutay, M. Alper; Onural, Levent; Özaktaş Haldun M.; Arıkan, Orhan
The ordinary Fourier transform is suited best for analysis and processing of time-invariant signals and systems. When we are dealing with time-varying signals and systems, filtering in fractional Fourier domains might allow us to estimate signals with smaller minimum-mean-square error (MSE). We derive the optimal fractional Fourier domain filter that minimizes the MSE for given non-stationary signal and noise statistics, and time-varying distortion kernel. We present an example for which the MSE is reduced by a factor of 50 as a result of filtering in the fractional Fourier domain, as compared to filtering in the conventional Fourier or time domains. We also discuss how the fractional Fourier transformation can be computed in O(N log N) time, so that the improvement in performance is achieved with little or no increase in computational complexity.
Open Access
Robust adaptive filtering algorithms for α-stable random processes
(Institute of Electrical and Electronics Engineers, 1999-02) Aydin, G.; Arıkan, Orhan; Çetin, A. Enis
A new class of algorithms based on the fractional lower order statistics is proposed for finite-impulse response adaptive filtering in the presence of α-stable processes. It is shown that the normalized least mean p-norm (NLMP) and Douglas' family of normalized least mean square algorithms are special cases of the proposed class of algorithms. A convergence proof for the new algorithm is given by showing that it performs a descent-type update of the NLMP cost function. Simulation studies indicate that the proposed algorithms provide superior performance in impulsive noise environments compared to the existing approaches.
Open Access
Robust least mean mixed norm adaptive filtering for α-stable random processes
(IEEE, 1997) Aydın, Gül; Tanrıkulu, O.; Çetin, A. Enis
Based on the concept of Fractional Lower Order Statistics (FLOS), we present the Robust Least Mean Mixed Norm (RLMMN) adaptive algorithm for applications in impulsive environments modeled by α-stable distributions. A sufficient condition for finite variance of the update term is obtained for the underlying α-stable process. Simulation results are provided regarding the identification of the parameters of an AR system.
Open Access
A Wired-AND Current-Mode Logic Circuit Technique in CMOS for Low-Voltage, High-Speed and Mixed-Signal VLSIC
(1997) Ungan I.E.; Aşkar, M.
A wired-AND current-mode logic (WCML) circuit technique in CMOS technology for low-voltage and high-speed VLSI circuits is proposed, and a WCML cell library is developed using standard 0.8 micron CMOS process. The proposed WCML technique applies the analog circuit design methodologies to the digital circuit design. The input and output logic signals are represented by current quantities. The supply current of the logic circuit is adjustable for the required logic speed and the switching noise level. The noise is reduced on the power supply lines and in the substrate by the current-steering technique and by the smooth swing of the reduced node potentials. Precise analog circuits and fast digital circuits can be integrated on the same silicon substrate by using the low noise property of the WCML. It is shown by the simulations that at low supply voltages, the WCML is faster and generates less switching noise when compared to the static-CMOS logic. At high speeds, the power dissipation of the WCML is less than that of the static-CMOS logic.