SERBIAN JOURNAL OF ELECTRICAL ENGINEERING
Vol. 17, No. 2, June 2020
CONTENTS
Analytical and Numerical Models Compared with Measurements for Analysis of Electromagnetic Radiation
through Apertures of a Metallic Enclosure
Download PDF file: 
(527.41 KB)
DOI: https://doi.org/10.2298/SJEE2002131A
Abstract: Generally, most of the electronic equipments need a metallic
enclosure in order to mechanically protect and electrically shield the interior printed circuit boards (PCBs) and subsystems.
But in practical situations, the apertures or slots of various forms are essential parts of
the shielding enclosure for thermal dissipation, CD-ROMs, connectors, I/O cabling and so on.
The performance of shielding enclosures for high-speed digital systems is compromised by these
inevitable discontinuities on enclosure. To minimize the electromagnetic interferences and
susceptibility risks by these discontinuities, the shielding enclosures with apertures should be
designed based on thorough analysis about the electromagnetic coupling mechanism through apertures.
In this paper, the effect of apertures and oblique incident plane wave on shielding effectiveness
of the enclosure is studied with the Circuital Approach, and the Finite-Difference Time-Domain (FDTD) method,
the simulated SE data are verified by experimental technique. Good agreements are found between these approaches.
Keywords: Shielding Effectiveness, Enclosures, Apertures, Normal incident, Oblique incident.
Wave-based Digital Models of Different Branch-Line Couplers
Download PDF file:
(1.33 MB)
DOI: https://doi.org/10.2298/SJEE2002149S
Abstract: Microwave and millimeter-wave communication systems require couplers in different applications.
The aim of this paper is to construct simple wave digital models of directional couplers with two or three parallel lines.
The idea behind this aim is to be able to model a microstrip structure and to simulate it using Simulink platform which has
already been used extensively by researchers. Advanced Design System (ADS) software and MATLAB/Simulink environment are used to design,
implement and simulate the investigated microstrip circuits and their models. Validity and accuracy of the presented digital models
are fully demonstrated through several benchmark problems.
Keywords: Coupler, Branch-line coupler, Microstrip circuit, Wave digital model, Circuit simulator.
Analysis of Signal Quality in FSO Systems with PolSK Modulation
Download PDF file:
(334.85 KB)
DOI: https://doi.org/10.2298/SJEE2002171T
Abstract: In this paper, the quality of the Polarization Shift Keying (PolSK) modulated signal in a Free Space Optical (FSO) system is analyzed.
The atmospheric channel is statistically modeled with four different distributions, namely, the Gamma-Gamma distribution, Negative Exponential distribution,
K-distribution, and I-K distribution. For all four channel models, the Average Bit Error Rate (ABER) at the receiving side of the system is determined in an analytically closed form.
The results are graphically presented and discussed in order to determine the impact of certain parameters on the ABER, i.e.,
the quality of the received signal in the PolSK modulated FSO system. These parameters are the Signal-to-Noise Ratio (SNR), the FSO link distance,
the wavelength at which the signal is transmitted, and the atmospheric turbulence strength.
Keywords: Average Bit Error Rate (ABER), Channel model, Free Space Optical (FSO), Polarization Shift Keying (PolSK), Signal-to-Noise Ratio (SNR).
Adaptive Symlet Filter Based on ECG Baseline Wander Removal
Download PDF file:
(918.30 KB)
DOI: https://doi.org/10.2298/SJEE2002187N
Abstract: In this paper, proposed a new approach of combining the hybrid soft computing technique
called Adaptive Symlet Wavelet Transform (ASWT) filter. The baseline wanders (BW) noise removal from an ECG signals to minimize distortion of the
S-T segment of the ECG signal specially that have high sampling frequencies. Therefore, when using Symlet Wavelet Transform (SWT) to
analysis the ECG signal can cause problems to analysis, exclusively when examining the content of the ECG signal at low-frequency such as S-T segment.
The corresponding frequency components of the approximation coefficients at level number seven are (0–3.9) Hz. Since the BW frequency is below 0.5 Hz
and ST segment frequency between (0.67–4) Hz. The adaptive filter with a unity reference signal used to remove the BW noise below 0.5 Hz
from the lowest level of the approximation coefficient of the decomposed ECG signal. The denoising output from adaptive filter and
the output from SWT (the other detail coefficients) will use as an input to ISWT for reconstruction ECG signals with the remove BW signal.
This method represents a very effective filter for BW noise removal, as it does not need for any computation process of reference point.
Keywords: S-T segment; Symlet transform; ECG noise removal, Baseline Wander.
A Modified ABC Algorithm for Solving Optimal Power Flow Problem
Download PDF file:
(389.22 KB)
DOI: https://doi.org/10.2298/SJEE2002199H
Abstract: This paper presents a modified artificial bee colony
(MABC) algorithm for solving the optimal power flow (OPF) problem in power system.
Artificial bee colony algorithm is a recent population-based optimization method which has been successfully used in many complex problems.
A new mutation strategy inspired from the differential evolution (DE) is introduced in order to improve the exploitation process.
The new algorithm is implemented to the OPF problem so as to minimize the total generation cost when considering the equality and
inequality constraints. In order to validate of the proposed algorithm, it is applied to the standard IEEE 30-bus test system.
The results show that the proposed technique provides better solutions than other heuristic techniques reported in literature.
Keywords: Modified artificial bee colony algorithm, Differential evolution, Optimization, Optimal power flow, Power system.
Design and Analysis of a Novel Miniaturized Microstrip Fractal Antenna for WLAN/WiMAX Applications
Download PDF file:
(7.98 MB)
DOI: https://doi.org/10.2298/SJEE2002213M
Abstract: This paper is a new comparative study via numerical calculations and
experimental measurements of various designs of fractal antennas. The geometry of the antennas dual‐broadband (2.5/5.77 GHz and 2.4/6.18 GHz)
for WLAN/ WiMAX applications is inspired by the Sierpinski carpet and the Minkowski. The simulated and measured results
show a good agreement over the bandwidth. We also performed a comparison with current comparable antenna designs,
demonstrating the superiority of the proposed antenna regarding applicability in telecommunication technology.
Keywords: Fractal antennas, Miniaturization, Dual-band.
Optimization of Synchronous Reluctance Motor Based on Radial Basis Network
Download PDF file:
(1.17 MB)
DOI: https://doi.org/10.2298/SJEE2002223N
Abstract: This paper presents surrogate-model based optimization for synchronous reluctance motor (SynRm) with transversally laminated rotor.
A radial basis function (RBF) model with 12 input variables and three outputs is first trained. A dataset is obtained using finite element method to estimate parameters of RBF model.
By building RBF model, the RBF network can predicts the outputs of the SynRm with good accuracy Using non-dominated sorting genetic algorithm (NSGA II), pareto front is obtained.
The SynRm is designed to maximize the maximum developed torque and power factor of the motor with constrained torque ripple.
Keywords: Electrical machine design, Synchronous reluctance motor, Multi-objective optimizations, Surrogate-model.
Green’s Function for the Semi-Infinite Strip in Terms of an Improper Integral
Download PDF file:
(1.25 MB)
DOI: https://doi.org/10.2298/SJEE2002235F
Abstract: In this paper Green’s function for the semi-infinite strip
(which is the two-dimensional Green’s function for a groove of infinite depth and height) is determined in the form of an improper integral,
as opposed to the standard sum-mation form. The integral itself, although rather complex, is found in a closed form.
By using the derived Green’s function simple formulas are obtained for a single and two-wire line configurations inside a groove of infinite depth and height.
Keywords: Semi-infinite strip, Groove, Green’s function, Capacitance.
Analytical Solution for Determination of Induction Machine Acceleration Based on Kloss Equation
Download PDF file:
(1.47 MB)
DOI: https://doi.org/10.2298/SJEE2002247K
Abstract: In this paper, the analytical solution for the determination of induction machine acceleration,
i.e. acceleration-time characteristic, during no-load direct start-up is proposed. The proposed dependence is derived from the Kloss equation for
torque-speed relation for the induction machine. Also, the analytical solution for the maximal value of the acceleration is derived in this paper.
The results obtained using developed expressions are compared with corresponding results obtained using the developed Matlab/ Simulink model for
analyses of the induction machine starting the process. Therefore, very high degree of accuracy is obtained.
Keywords: Induction machine, Kloss equation, Acceleration, Analytical solution, No-load direct start-up.
Corrigendum
Download PDF file:
(1.18 MB)
DOI: https://doi.org/10.2298/SJEE2002257E