Vol. 14, No. 1, February 2017


Ivana Mladenović, Jelena Lamovec, Vesna Jović, Vesna Radojević
Synergetic Effect of Additives on the Hardness and Adhesion of Thin Electrodeposited Copper Films
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DOI: 10.2298/SJEE1701001M
Abstract: Thin copper films were electrodeposited on a polycrystalline cold-rolled copper substrate. The composition of the laboratory-made copper sulphate electrolyte was changed by the addition of various additives. The influence of chloride ion (Cl-), polyethylene glycol (PEG) and 3-mercapto-1-propane sulfonic acid (MPSA) on mechanical and adhesion properties of the electrodeposited copper films was investigated using Vickers microindentation technique. Calculations of the film hardness and adhesion were carried out using composite hardness models of Korsunsky and Chen-Gao. The hardness of the composite system is influenced by the adhesion of the copper film to the substrate. Increasing adhesion corresponds to increasing values of the calculated adhesion parameter b, named the critical reduced depth. When additives are added to a plating solution, the copper deposition mechanism is changed and fine-grained microstructure without the formation of microscopic nodules is obtained.
Keywords: Composite microhardness, Electrodeposition, PEG, MPS, Adhesion, Critical reduced depth.

Luka Mejić, Strahinja Došen, Vojin Ilić, Darko Stanišić, Nikola Jorgovanović
An Implementation of Movement Classification for Prosthesis Control Using Custom-Made EMG System
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DOI: 10.2298/SJEE1701013M
Abstract: Electromyography (EMG) is a well known technique used for recording electrical activity produced by human muscles. In the last few decades, EMG signals are used as a control input for prosthetic hands. There are several multifunctional myoelectric prosthetic hands for amputees on the market, but so forth, none of these devices permits the natural control of more than two degrees of freedom. In this paper we present our implementation of the pattern classification using custom made components (electrodes and an embedded EMG amplifier). The components were evaluated in offline and online tests, in able bodied as well as amputee subjects. This type of control is based on computing the time domain features of the EMG signals recorded from the forearm and using these features as input for a Linear Discriminant Analysis (LDA) classifier estimating the intention of the prosthetic user.
Keywords: Grasping, Grips, Hand, Electromyography, Classification, LDA, Signals, Feature, Analysis, Neural prosthesis, Forearm.

Đorđe Novaković, Platon Sovilj, Nemanja Gazivoda
Multisensory Platform Based on NEC Protocol
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DOI: 10.2298/SJEE1701023N
Abstract: Multisensory signal acquisition represents one of the main concepts necessary to perform measurements in various industrial and consumer-oriented applications. This paper presents a development platform which provides a data acquisition from multiple sensors. The main module of the platform is the UNIDS-3 development board with PIC18F8520 microcontroller. Data acquisition from the sensors is performed on user demand by remote control. NEC protocol is implemented and IR receiver TSOP31238 is used. The measurement data are sent to a computer, which performs digital data processing, data visualization and data storage.
Keywords: Multisensory platform, Remote control, NEC protocol.

Vladica Đorđević, Zlatica Marinković, Olivera Pronić-Rančić, Vera Marković
An Analytical Approach to the HEMT Noise Wave Model Parameter Determination
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DOI: 10.2298/SJEE1701035D
Abstract: This paper presents an analytical approach to determination of the noise wave model parameters for a high electron-mobility transistor working under different temperature and frequency conditions. The presented approach is composed of two steps and provides more efficient determination of these parameters than in the case of optimization procedures commonly applied for that purpose in circuit simulators. The first step is extraction of the noise parameters of transistor intrinsic circuit from the measured noise parameters of whole transistor using an analytical noise de-embedding procedure. The second step is calculation of the noise wave model parameters from the de-embedded intrinsic noise parameters using existing formulas. The accuracy of the presented approach is validated in a wide frequency and temperature range by comparison of the transistor noise parameters simulated for the determined noise wave model parameters with the measured noise parameters.
Keywords: Analytical Approach, HEMT, Noise Parameters, Noise Wave Model

Katarina Milenković, Žarko Stanisavljević, Jovan Đorđević
Visual Software System for Memory Interleaving Simulation
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DOI: 10.2298/SJEE1701051M
Abstract: This paper describes the visual software system for memory interleaving simulation (VSMIS), implemented for the purpose of the course Computer Architecture and Organization 1, at the School of Electrical Engineering, University of Belgrade. The simulator enables students to expand their knowledge through practical work in the laboratory, as well as through independent work at home. VSMIS gives users the possibility to initialize parts of the system and to control simulation steps. The user has the ability to monitor simulation through graphical representation. It is possible to navigate through the entire hierarchy of the system using simple navigation. During the simulation the user can observe and set the values of the memory location. At any time, the user can reset the simulation of the system and observe it for different memory states; in addition, it is possible to save the current state of the simulation and continue with the execution of the simulation later.
Keywords: Computer architecture and organization, Memory interleaving, Software system, Simulation, Main memory, Random-access memory, Laboratory exercise.

Vladimir L. Petrović, Jelena S. Popović-Božović
A Method for Real-Time Memory Efficient Implementation of Blob Detection in Large Images
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DOI: 10.2298/SJEE1701067P
Abstract: In this paper we propose a method for real-time blob detection in large images with low memory cost. The method is suitable for implementation on the specialized parallel hardware such as multi-core platforms, FPGA and ASIC. It uses parallelism to speed-up the blob detection. The input image is divided into blocks of equal sizes to which the maximally stable extremal regions (MSER) blob detector is applied in parallel. We propose the usage of multiresolution analysis for detection of large blobs which are not detected by processing the small blocks. This method can find its place in many applications such as medical imaging, text recognition, as well as video surveillance or wide area motion imagery (WAMI). We explored the possibilities of usage of detected blobs in the feature-based image alignment as well. When large images are processed, our approach is 10 to over 20 times more memory efficient than the state of the art hardware implementation of the MSER.
Keywords: Real-time blob detection, Maximally stable extremal regions, Parallelism, Multiresolution analysis, Image alignment.

Željko Beljić , Boris Ličina, Platon Sovilj, Dragan Pejić, Vladimir Vujičić, Bojan Vujičić
Measurement of Definite Integral of Sinusoidal Signal Absolute Value Third Power Using Digital Stochastic Method
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DOI: 10.2298/SJEE1701085B
Abstract: In this paper a special case of digital stochastic measurement of the third power of definite integral of sinusoidal signal’s absolute value, using 2-bit AD converters is presented. This case of digital stochastic method had emerged from the need to measure power and energy of the wind. Power and energy are proportional to the third power of wind speed. Anemometer output signal is sinusoidal. Therefore an integral of the third power of sinusoidal signal is zero. Two approaches are proposed for the third power calculation of the wind speed signal. One approach is to use absolute value of sinusoidal signal (before AD conversion) for which there is no need of multiplier hardware change. The second approach requires small multiplier hardware change, but input signal remains unchanged. For the second approach proposed minimal hardware change was made to calculate absolute value of the result after AD conversion. Simulations have confirmed theoretical analysis. Expected precision of wind energy measurement of proposed device is better than 0,00051% of full scale.
Keywords: AD conversion, Digital measurements, Electrical measurements, Probability, Stochastic processes.

Marjan Urekar, Nemanja Gazivoda
The Transfer Voltage Standard for Calibration Outside of a Laboratory
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DOI: 10.2298/SJEE1701099U
Abstract: The transfer voltage standard is designed for transferring the analog voltage from a calibrator to the process control workstation for multi-electrode electrolysis process in a plating plant. Transfer voltage standard is based on polypropylene capacitors and operational amplifiers with tera-ohm range input resistance needed for capacitor self-discharging effect cancellation. Dielectric absorption effect is described. An instrument for comparison of reference and control voltages is devised, based on precise window comparator. Detailed description of the main task is given, including constraints, theoretical and practical solutions. Procedure for usage of the standard outside of a laboratory conditions is explained. Comparison of expected and realized standard characteristics is given.
Keywords: Voltage standard, Calibration, Polypropylene capacitor, Dielectric absorption, Window comparator, Metrology, Electrolysis, Plating.

Bane Popadić, Vladimir Katić, Boris Dumnić, Dragan Milićević, Zoltan Čorba
Synchronization Method for Grid Integrated Battery Storage Systems During Asymmetrical Grid Faults
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DOI: 10.2298/SJEE1701113P
Abstract: This paper aims at presenting a robust and reliable synchronization method for battery storage systems during asymmetrical grid faults. For this purpose, a Matlab/Simulink based model for testing of the power electronic interface between the grid and the battery storage systems has been developed. The synchronization method proposed in the paper is based on the proportional-integral resonant controller with the delay signal cancellation. The validity of the synchronization method has been verified using the advanced laboratory station for the control of grid connected distributed energy sources. The proposed synchronization method has eliminated unfavourable components from the estimated grid angular frequency, leading to the more accurate and reliable tracking of the grid voltage vector positive sequence during both the normal operation and the operation during asymmetrical grid faults.
Keywords: Battery Storage Systems, Synchronization, Grid Connected Converter, Asymmetrical Grid Faults.

Marko Ninić, Radivoje Đurić
A Novel High Efficiency CMOS RF/DC Power Harvester Based on Constant ON/OFF Time Buck Controller for 60GHz Frequency Band
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DOI: 10.2298/SJEE1701133N
Abstract: A novel 60 GHz RF/DC power harvesting system is presented. The system consists of RF to DC rectifier and a DC/DC Buck converter based on constant ON/OFF time (COOT) control. The rectifier has a structure of voltage doubler, but employs diodes that have lower parasitics compared to those of the standard MOSFET diodes, resulting in improved power conversion efficiency. The peak efficiency of the rectifier obtained with the extracted parasitics for the output power of 1 mW is about 25%. In order to keep the output voltage of the system to 1.2 V, the COOT control in the Buck converter is used. COOT control has much better efficiency at low output powers compared to the PWM systems. For correct operation of the COOT control, auxiliary sub-blocks: a low power high-speed comparator, a hysteresis comparator, and a high-speed voltage reference are designed and presented. The maximum switching frequency in the Buck converter is about 100MHz and the whole control system has very low static power consumption. The efficiency of the overall system for the output power of 1mW is about 21%. The system is designed in 65 nm CMOS technology.
Keywords: 60GHz, CMOS, Power harvesting, Buck converter, Rectifier, Voltage doubler.

Lazar Cokić, Aleksandra Marjanović, Sanja Vujnović, Željko Đurović
The Robustness of the Differential Quantizer in the Case of the Variable Signal to Noise Ratio
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DOI: 10.2298/SJEE1701149C
Abstract: In this paper a short theoretical overview of differential quantizer and its implementations is given. Afterward, the effect of the order of prediction in differential quantizer and the effect of the difference in order of predictor in the input and output of differential quantizer is analyzed. Then it was proceeded with the examination of the robustness of the differential quantizer in the case in which a noise signal is brought to the input of the differential quantizer, instead of the clean speech signal. The analysis was conducted with a uniform distribution, as well as the noise with the gaussian distribution, and the obtained results were adequately commented on. Also, experimentally a limit was set which refers to the intensity of the noise and still enable results which are better that a regular uniform quantizer. The whole analysis is done by using the fixed number of bits in quantization, i.e. 12-bit quantizer is used in all the implementations of differential quantizer. In the conclusion of this paper there is a discussion about the possibility of implementing a differential quantizer which will be able to recognize which noise attacks the system, and in addition to that, in what form it adapts its coefficients so that it at any moment acquires the optimal signal to noise ratio.
Keywords: Differential quantizer, Digital speech processing, Predictor order, quantization, Signal to noise ratio.

Maja Rosić, Mirjana Simić, Predrag Pejović, Milan Bjelica
Optimal Source Localization Problem Based on TOA Measurements
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DOI: 10.2298/SJEE1701161R
Abstract: Determining an optimal emitting source location based on the time of arrival (TOA) measurements is one of the important problems in Wireless Sensor Networks (WSNs). The nonlinear least-squares (NLS) estimation technique is employed to obtain the location of an emitting source. This optimization problem has been formulated by the minimization of the sum of squared residuals between estimated and measured data as the objective function. This paper presents a hybridization of Genetic Algorithm (GA) for the determination of the global optimum solution with the local search Newton-Raphson (NR) method. The corresponding Cramer-Rao lower bound (CRLB) on the localization errors is derived, which gives a lower bound on the variance of any unbiased estimator. Simulation results under different signal-to-noise-ratio (SNR) conditions show that the proposed hybrid Genetic Algorithm–Newton-Raphson (GA–NR) improves the accuracy and efficiency of the optimal solution compared to the regular GA.
Keywords: Genetic Algorithm, Localization, Signal-to-noise ratio, Time of Arrival, Wireless Sensor Networks.

©2017 Serbian Journal of Electrical Engineering