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In this paper, a novel antenna decoupling approach is investigated. The introduced concept is based on expelling the currents flowing between the closely spaced antennas through a tapered slot etched on the array ground plane. The method is free from extra-reactive components and transmission lines. Although they are closely spaced and strongly coupled, the technique allows a high improvement in port isolation. A practical implementation of this mechanism is applied to a monopole array of two elements working at 2.45 GHz and closely packed ($0.069\lambda _{0}$). The obtained results are very attractive, and a decoupling of about 40 dB is achieved with good impedance matching. Moreover, radiation diversity is obtained with a gain of 1.9 dBi. Furthermore, the decoupled array is integrated in a real receiving system, and the proposed decoupling technique is checked through the array signal processing. Hence, the obtained results confirm the effectiveness of the proposed decoupling mechanism. In addition to its efficient port isolation, the most attractive features of the proposed decoupling technique are simplicity and ease of implementation in compact multiantenna devices. [ABSTRACT FROM AUTHOR]

This paper presents two new time-frequency distributions (TFDs) based on kernels with compact support (KCS) namely the separable (CB) (SCB) and the polynomial CB (PCB) TFDs. The implementation of this family of TFDs follows the method developed for the Cheriet–Belouchrani (CB) TFD. The mathematical properties of these three TFDs are analyzed and their performance is compared to the best classical quadratic TFDs using several tests on multicomponent signals with linear and nonlinear frequency modulation (FM) components including the noise effects. Instead of relying solely on visual inspection of the time-frequency domain plots, comparisons include the time slices' plots and the evaluation of the Boashash–Sucic's normalized instantaneous resolution performance measure that permits to provide the optimized TFD using a specific methodology. In all presented examples, the KCS-TFDs show a significant interference rejection, with the component energy concentration around their respective instantaneous frequency laws yielding high resolution measure values. [ABSTRACT FROM AUTHOR]

The Arctangent function is used in several signal processing applications and it is widely needed for hardware implementations. However, it often constitutes the performance bottleneck because of its inaccuracy and/or its poor performances. We present a generic VLSI design to respond to some applications' need of fast Arctangent functions handling high precision data. The method presented here contrasts with the usual Look Up table based solutions which allow the output customization but limit the precision of the corresponding tangent input. Detailed logical design and FPGA implementation results are provided to show our solution as the best candidate to comply with fast execution as well as high precision for both input and output data. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with the idea of implementing a complete network service on a chip. Herein, we propose an original design together with an efficient implementation of an authoritative domain name system (DNS) server on a Virtex 5 FPGA circuit. The proposed approach exploits the use of a hardware accelerator, MicroBlaze soft-processor cores and an adequate mapping between the DNS specifications and the hardware architecture leading to a Multi-Processor System on Chip (MPSoC). We propose new architectures by translating the DNS specifications to hardware form through the “Specification and Description Language” (SDL) tool. The proposed implementation allows significant reduction in power consumption together with significant performance and security improvement. The proposed architectures have been successfully implemented and tested on an actual network. The obtained results show a query performance improvement of around 200% with respect to the “Berkeley Internet Name Domain” (BIND) 9 server. [Copyright &y& Elsevier]

This contribution addresses the problem of estimating the parameters of multicomponent polynomial-phase signals when impinging on a multisensor array. An original approach is proposed based on a state-space modelization of the signal and the application of an extended Kalman filter for the state estimation. The use of a multisensor array allows the exploitation of a spatial information and leads to the consideration of multiple filters with different observation equations. Computer simulations are used to demonstrate the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

In radar applications, the received echo signals reach the array elements via a multiplicity of paths despite the fact that there exists only one target. We address the problem of joint direction of arrival and Doppler frequency estimation using a sensor array in partially known additive noise. We consider a specular reflection model with a radar cross section fluctuating from one pulse repetition interval to another. The proposed model allows the estimation of more paths than sensors. Two approximate maximum likelihood algorithms are proposed. The first approach uses a linear expansion of the noise covariance matrix, whereas the second employs a combination of oblique projections and a zero-forcing solution to alleviate the effect of noise. In contrast to other classical methods, the two approaches are more robust to spatially correlated noise, and they employ more compact cost functions that reduce the dimension of the optimization search. Numerical simulations are provided to assess the basic performance of the two approaches, which are compared to the Cramér-Rao bound. [ABSTRACT FROM AUTHOR]

Presents information on a study which focused on a two-sensor array blind beamformer dedicated to the problem of interference mitigation in a direct sequence spread spectrum communication system. Problem formulation; Computational analysis; Performance evaluations; Conclusions.

Presents a study which introduced a blind source identification technique based on a joint diagonalization of a combined set of spatial time-frequency distributions (STFD) that are a generalization of the t-f distribution to a vector signal. Problem formulation; Two-step blind identification approach; Asymptotic performance analysis.

Proposes a carrier tracking approach that has guaranteed global convergence. Formulation of the carrier tracking problem; Carrier tracking using blind source separation; Simulation results; Conclusion.

Introduces a new source separation technique exploiting the time coherence of the source signals. Formulation of problem; A second-order identification approach; Asymptotic performance analysis; Performance evaluation of the second-order blind identification (SOBI) algorithm; Conclusion of the study.

This paper describes a method for the classification of heartbeats based on electrocardiogram QRS complex and T wave autoregressive (AR) features and interbeat distance (RR interval) features. The QRS complex (length n samples) is modelled using AR model of order P. A second AR model of order P1 is applied to the electrocardiogram segment including ST segment and T wave (ST/T segment) with a length of n1 samples. In addition, RR interval features such as the distance between one heartbeat and its preceding (pre-RR) and following (post-RR) heartbeats are extracted. The use of AR modelling is motivated by the fact that QRS complex and ST/T segment corresponding to normal beats present different patterns (in shapes and amplitudes) than those corresponding to ventricular ectopic beats. Lengths and AR model orders that minimize the number of misclassifications are determined. Obtained features are used to train and test support vector machine classifier. The proposed method is tested on MIT/BIH Arrhythmia Database and it is compared to state of the art methods. Overall classification accuracy reached 97.02%, whereas it reached 98.86% in the case of subject-specific scheme. Results are better or comparable to those obtained by state of the art methods. [ABSTRACT FROM AUTHOR]

Digital filter design optimization counts as one of the most challenging problems in circuit development. Furthermore, the bit-width allocation has a crucial impact on the efficiency and accuracy of fixed-point digital filters. The conventional implementation procedure involves studying the bit-width allocation problem after determining the filter coefficients. This sequential procedure leads frequently to an excessive bit-width allocation, hence an extra implementation cost. The main contribution of this paper is to propose a new implementation procedure based on the simultaneous handling of both design issues and the bit-width optimization for the infinite impulse response filter. In this study, the problem is formalized by a multi-objective programming technique using the non-dominated sorting genetic algorithm II. The joint consideration of the two problems offers a better trade-off between design and bit-width allocation. The output of our approach is compared to the results of existing algorithms. Simulation results show that the multi-objective method significantly reduces the implementation cost while ensuring filter stability and an acceptable mean square error (MSE) compared to the existing algorithms. [ABSTRACT FROM AUTHOR]

This paper describes the design guidelines for frequency independent 180° phase shifters. The proposed configuration is based on microstrip slot transition technique. The frequency independence feature is due to comparing two quasi‐identical structures and the phase inversion (180°) is related to the chosen inverted orientation of the main line compared to the reference one. Moreover, two different schemes are designed and manufactured and a good simulation to measurement agreement is demonstrated. Thus, interesting results are obtained (more than 10 dB return loss, less than 2.1 dB insertion loss and less than ± 3.6° phase deviation). [ABSTRACT FROM AUTHOR]

In this article, a novel Ultra-Wideband (UWB) 180° planar phase shifter is designed and fabricated. The proposed design is mainly based on coupled sections which are realized by inserting slots into the common ground plane of the multilayer circuit. Two identical structures, leading to discard parameters that disturb the output phase shift, are introduced in the design. To get 180° phase difference shift, via holes are used to perform a short circuit in one of the two coupled sections. Theoretical analysis based on four port network is presented to explain the characteristics of the proposed design. Further, experimental measurements are performed and compared with simulation results to validate the proposed approach. Hence, a good simulated to measured agreement is obtained. [ABSTRACT FROM AUTHOR]

This paper addresses the precision analysis of filters in the parallel form framework. The precision analysis consists of determining suitable fractional bit-widths to set a tradeoff between resource consumption and computational accuracy. Although the stability of the parallel form is relatively better controlled than the related direct form, its bit-width optimization did not receive much consideration in the literature, despite its significant contribution to the optimization of the filter's physical implementation. To carry out the needed bit-width optimization, we present two heuristics based on the Estimation of Distribution Algorithm, which falls within the category of probabilistic model-building genetic algorithm. The performance of the proposed approach is discussed, and compared to chosen benchmarks, the results show that our hardware implementations reduce the cost of the resulted circuits up to 37 % . [ABSTRACT FROM AUTHOR]

This paper introduces a new algorithm to approximate non-orthogonal joint diagonalization (NOJD) of a set of complex matrices. This algorithm is based on the Frobenius norm formulation of the joint diagonalization (JD) problem and takes advantage from combining Givens and Shear rotations to attempt the approximate JD. It represents a non-trivial generalization of the JDi (Joint Diagonalization) algorithm (Souloumiac 2009) to the complex case. The JDi is first slightly modified then generalized to the CJDi (i.e., Complex JDi) using complex to real matrix transformation. Several methods already exist in the literature. Consequently, we provide herein a brief overview of existing NOJD algorithms. Then we provide an extensive comparative study to illustrate the effectiveness and stability of the CJDi with respect to various system parameters and application contexts. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a new system for ECG beat classification using support vector machines classifier with a double hinge loss. The proposed classifier rejects samples that cannot be classified with enough confidence. Specifically in medical diagnoses, the consequence of a wrong classification can be so harmful that it is convenient to reject such sample. After ECG preprocessing, feature selection and extraction, our decision rule uses dynamic reject thresholds according to the cost of rejecting or misclassifying a sample. Significant performance enhancement is observed when the proposed approach is tested with the MIT-BIH arrythmia database. The achieved results are represented by the error reject tradeoff. We obtained 98.2% of sensitivity with no rejection and more than 99% of sensitivity for the optimal classification cost being competitive to other published studies. [ABSTRACT FROM AUTHOR]

Abstract: In the following work, we propose an assessment of wind potential in Algeria. The purpose of this study is twofold. First, to draw the attention to the important wind potential in the region of Hassi-R’mel . In the previous maps, the wind potential in this region has been underestimated due the fact that it is located between two less windy regions. Second, the actualization of the wind map of Algeria using very recent data stretching from February 2004 to December 2009. This paper is structured in three main parts. First, a stochastic and the cyclic study of the wind behaviors in the site of Hassi-R’mel are proposed. The stochastic study is carried out by fitting the wind speed data to Weibull distribution while the cyclic study is carried out via the use of time–frequency analysis. We have used the time–frequency analyses instead of the traditional Fourier analysis due its ability to follow the spectrum variation with respect to time. As results, it has been found that spectrum wind process enfold many limited interval oscillations. In the second part, we propose to contribute to the actualisation of the wind map in Algeria. In this part, we have considered also the topographical aspect of Algeria. Such consideration is very helpful for understanding the wind potential reparation over the country. Finally, a techno-economical study of a stand along hybrid system (wind/diesel) in the site of Hassi-R’mel is considered. Via this study, it has been found that been found that the site of Hassi-R’mel is very adequate for wind energy conversion systems. [ABSTRACT FROM AUTHOR]

This study proposes a process of assessment of wind potential using descriptive statistics and time-frequency analysis. Via the time-frequency analysis, the variation of the spectral content of wind speed with respect to time is analyzed by the determination of the frequencies, the durations and the occurrence-time of significant fluctuations. The study is carried out for six sites in Algeria during a time interval of 1 year and over a frequency range from 1.1 × 10 to 2.4 cycles/day (i.e., periods from 10 h to about 90 days). The study has allowed to deduce that the windiest regions are located in the southern part of the country with annual mean from 5 to 6 m/s. The time-frequency analysis reveals the presence of three types of oscillations. In the warm season, diurnal oscillations have been distinguished especially in the costal and mountainous regions. However, in the cold season, synoptic oscillations of periods around 9-13 days have been observed. The Southern regions are characterized by long oscillations of periods around 33-50 days. [ABSTRACT FROM AUTHOR]

Word-length allocation is the most important design phase to optimize hardware resources while guaranteeing a determined accuracy for circuits with fixed-point numbers. This paper presents an enhanced precision analysis for degree-n polynomial Horner's rule. It is based on affine arithmetic and introduces an error propagating formula for a degree-n polynomial Horner's rule. It takes into account quantization error of all the circuit's connections including the inputs. Furthermore, a tighter upper bound error is defined, exploiting the dependencies between intermediate connections. Hardware implementations show that the proposed upper bound results in an area reduction that reaches 70 percent. [ABSTRACT FROM AUTHOR]

In recent work sea clutter has been modeled as the product of two components. The first one, referred to as speckle, is modeled as a stationary Gaussian process. It is characterized by a short correlation time. The second component, referred to as texture, is modeled as a stationary or cyclostationary process. It is characterized by a long correlation time. Two approaches for the estimation of the texture are introduced here. The first approach involves the correlation properties of texture and speckle. The texture spectrum is modeled as an autoregressive (AR) process, while the texture range profile within one pulse repetition interval (PRI) is identified by combining the AR estimation of the sea clutter sample auto-covariance with the empirical orthogonal functions (EOF) analysis. The second approach involves a mixed $\ell_2$-$\ell_1$ norm minimization criterion to account for the sparse harmonic structure of the texture, considered herein as a cyclostationary process within multiple coherent processing intervals (CPI). [ABSTRACT FROM AUTHOR]

Abstract: Electrocardiogram (ECG) signal processing and analysis provide crucial information about functional status of the heart. The QRS complex represents the most important component within the ECG signal. Its detection is the first step of all kinds of automatic feature extraction. QRS detector must be able to detect a large number of different QRS morphologies. This paper examines the use of wavelet detail coefficients for the accurate detection of different QRS morphologies in ECG. Our method is based on the power spectrum of QRS complexes in different energy levels since it differs from normal beats to abnormal ones. This property is used to discriminate between true beats (normal and abnormal) and false beats. Significant performance enhancement is observed when the proposed approach is tested with the MIT-BIH arrhythmia database (MITDB). The obtained results show a sensitivity of 99.64% and a positive predictivity of 99.82%. [Copyright &y& Elsevier]

This paper deals with fault diagnosis of induction machines based on the discrete wavelet transform. By using the wavelet decomposition, the information on the health of a system can be extracted from a signal over a wide range of frequencies. This analysis is performed in both time and frequency domains. The Daubechies wavelet is selected for the analysis of the stator current. Wavelet components appear to be useful for detecting different electrical faults. In this paper, we will study the problem of broken rotor bars, end-ring segment, and loss of stator phase during operation. [ABSTRACT FROM AUTHOR]

This paper considers the blind separation of nonstationary sources in the underdetermined case, when there are more sources than sensors. A general framework for this problem is to work on sources that are sparse in some signal representation do- main. Recently, two methods have been proposed with respect to the time-frequency (TF) domain. The first uses quadratic time-frequency distributions (TFDs) and a clustering approach, and the second uses a linear TFD. Both of these methods assume that the sources are disjoint in the TF domain; i.e., there is, at most, one source present at a point in the TF domain. In this paper, we relax this assumption by allowing the sources to be TF-nondisjoint to a certain extent. In particular, the number of sources present at a point is strictly less than the number of sensors. The separation can still be achieved due to subspace projection that allows us to identify the sources present and to estimate their corresponding TFD values. In particular, we propose two subspace-based algorithms for TF-nondisjoint sources: one uses quadratic TFDs and the other a linear TFD. Another contribution of this paper is a new estimation procedure for the mixing matrix. Finally, then numerical performance of the proposed methods are provided highlighting their performance gain compared to existing ones. [ABSTRACT FROM AUTHOR]