Recent Submissions

Now showing 1 - 5 of 37
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    Bit Error Probability of M-QAM under Impulsive Noise and Fading Modeled by Markov Chains
    (Společnost pro radioelektronické inženýrství, 2018-12) Silva, Hugerles S.; de Alencar, Marcelo S.; de Queiroz, Wamberto J. L.; Coelho, Rodrigo de A.; Madeiro, Francisco
    This article presents new exact expressions, written in terms of elementary transcendental functions, for calculating the bit error probability of M-ary Quadrature Amplitude Modulation (M-QAM) scheme considering the wireless communication channel modeled by a Markov chain with N states. For the numerical evaluation of the expressions obtained, a particular case of a Markov chain with two states is considered, with each state representing distinct scenarios. In the first scenario it is considered the presence of Gated Additive White Gaussian Noise (GAWGN) and fading eta-mu or kappa-mu, while the second scenario considers the presence of the Double Gated Additive White Gaussian Noise (G2AWGN) and fading eta-mu or kappa-mu. Bit error probability curves as a function of the signal-to-permanent-noise ratio for different values of the signal-to-impulsive-noise ratio, fading parameters and modulation order M are also presented.
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    An Unambiguous Tracking Technique for Cosine-Phased BOC Signals with Low Complexity
    (Společnost pro radioelektronické inženýrství, 2018-12) Li, Tian; Tang, Zuping; Wei, Jiaolong; Zhou, Zhihui; Wang, Boyi
    A low-complexity unambiguous tracking method for cosine-phased binary offset carrier (BOCc) signals is proposed in this paper. The proposed method directly constructs a code discriminator function by multiplying two correlation functions. One local reference signal is a specifically designed auxiliary signal whose cross-correlation function with the BOCc signal is an unambiguous S-curve. The other reference signal is a replica BOCc signal whose correlation function with the BOCc signal is used as a "cover" to maintain the slope of the discriminant function as much as possible and to make the final discriminant function non-coherent.The proposed discriminator function has only a single main lock point and can make tracking reliable and unambiguous. In contrast to the traditional unambiguous early-minus-late methods, the proposed method needs only the prompt branch correlator outputs, and the correlation process of the BOCc signal with input signals is the same as that of the carrier loop process. As a result, the proposed method reduces the number of correlators by at least three-quarters. The theoretical analysis and simulation results show that the proposed method has higher code tracking accuracy, lower tracking threshold and better anti-multipath performance than those of PUDLL, SF and SPAR. In conclusion, the proposed method completely eliminates tracking ambiguity, significantly improves tracking performance and reduces implementation complexity.
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    Generalized Roughness Bearing Faults Diagnosis Based on Induction Motor Stator Current
    (Společnost pro radioelektronické inženýrství, 2018-12) Andrijauskas, Ignas; Vaitkunas, Mindaugas; Adaskevicius, Rimas
    Despite their reliability, induction motors tend to fail. Around 41% of faults in motors are bearing related and that is the most common fault in motor field. Due to the lack of research on generalized roughness bearing fault diagnostics by use of a stator current spectrum, the presented study analyses both single-point and generalized roughness bearing faults and their classification possibilities. In this paper, a new method for generalized roughness ball bearing fault identification by use of a stator current signal analysis is presented. The algorithm relies on Discrete Wavelet Transform and Welch's spectral density analysis. The composition of both methods is used for building a feature vector for the classifier. In order to achieve classification, support vector machine classifier with linear kernel function has been applied. The validation experiment and results are presented.
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    Efficient Procedure Improving Precision of High Conditioned Matrices in Electronic Circuits Analysis
    (Společnost pro radioelektronické inženýrství, 2018-12) Cerny, David; Dobes, Josef; Banas, Stanislav
    In this article, we propose several improvements that could be done to SPICE simulator. The first is based on a functional implementation of device models. The advantages of functional implementation are demonstrated on basic Shichman-Hodges model of MOS transistor. It starts with a description of primary algorithms used in SPICE simulator for the solution of circuits with nonlinear devices and identify the problems that can occur during simulations.Main part of the article is devoted to improved factorization procedure for simulation of the nonlinear electronic circuits. The primary intention of the proposed method is to increase final precision of the result in a case of high condition linear systems. The procedure is based on a use of the iterative methods for solution of nonlinear and linear equations. Utilizing those methods for one iterative process helps to reduce memory consumption during simulation computation, and it can significantly improve simulation precision. The procedure allows to use enumeration with definable precision in a very efficient way.
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    Robust Hybrid Algorithm of PSO and SOCP for Grating Lobe Suppression and against Array Manifold Mismatch
    (Společnost pro radioelektronické inženýrství, 2018-12) Li, Hailin; Liu, Jialing; Sun, Jie; Cao, Aihua; Jin, Can; Zhou, Jianjiang
    Based on Particle Swarm Optimization (PSO) and Second-Order Cone Programming (SOCP) algorithm, this paper proposes a hybrid optimization method to suppress the grating lobes of sparse arrays and improve the robustness of array layout. With the peak side-lobe level (PSLL) as the objective function, the paper adopts the particle swarm optimization as a global optimization algorithm to optimize the elements’ positions, the convex optimization as a local optimization algorithm to optimize the elements’ weights. The effectiveness of the grating lobes suppression (as low as -32.13 dB) by this method is illustrated through its application to the sparse linear array when the actual steering vector is known. To enhance the robustness of the optimized array, a rebuilt robust convex optimization model is adopted in the optimization of both array excitations and layout. When the array manifold mismatch error is 1cm, the PSLL by the robust algorithm can be compressed to -27dB, compared to that of -24dB by the ordinary optimization. Results of a set of representative numerical experiments show that the algorithm proposed in this paper can obtain a more robust array layout and matched elements’ weight coefficients to avoid the huge degradation of the array pattern performance in the presence of array manifold mismatch errors. The good performance of pattern synthesis demonstrates the effectiveness of the proposed robust algorithm.