Vol. 17, No. 1, February 2020


Oleksandr V. Vovna, Ivan S. Laktionov, Oleksiy O. Koyfman, Ihor I. Stashkevych, Vladyslav A. Lebediev
Study of Metrological Characteristics of Low-Cost Digital Temperature Sensors for Greenhouse Conditions
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Abstract: The article focuses on the relevant scientific and applied problem of assessing and analyzing the metrological characteristics of available digital temperature sensors for greenhouse conditions. The hardware and software implementation of the microprocessor system for obtaining calibration characteristics and evaluating the accuracy and performance of temperature sensors for the physical media under greenhouse conditions is studied. A particular type of linear calibration equation for the temperature sensors under study is established. The values of systematic absolute measurement deviations of temperature sensors DS18B20, SHT11, SHT21, BMP180, BME280 and DHT22 are experimentally obtained. Recommendations on improving the accuracy of temperature information and temperature measuring systems under greenhouse conditions are given. The perspective areas of the research on metrological provision of modern means of automatic monitoring and temperature control in industrial greenhouses are substantiated.
Keywords: Sensor, Deviation, Temperature, Greenhouse.

Bashar Bahaa Qas Elias, Haider Aljanabi
Modified Design of Microstrip Patch Antenna for UWB Applications
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Abstract: Ultra-wideband (UWB) patch antenna for Ku/K band applications is presented. In this paper, a microstrip line feed has been modified to an elliptical gradient structure, and the conventional radiator patch has been developed through the use of the symmetrically circular slots. These modifications have been used to improve the performance of the antenna significantly. Upper and lower frequency ranges achieve UWB antenna performances start from 11.57 GHz to 21.45 GHz. Proposed antenna exhibits good impedance matching, which makes it convenient to work in various applications. Besides that, the reflection coefficient is reduced attained to –31.81 dB over the operating band. The antenna is developed and analyzed using the commercially available software FEKO simulator based on the method of moments (MoM). Other parameters results such as sidelobe level (SLL) and beamwidth (half power –3 dB) are added and discussed significantly. The proposed design is fabricated and tested experimentally, and the results show that a satisfying agreement with the simulation results.
Keywords: Modified antenna, Ultra-wideband (UWB), Reflection coefficient, Slots, Feed line, FEKO.

Guru Prasad, Kumara Shama
A 167.18 ppm/°C Temperature Coefficient, Area Efficient Voltage Reference Using Only MOS Transistors
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Abstract: In this paper, design of a voltage reference circuit using only MOS transistors and without employing an operational amplifier is presented. A proportional to absolute temperature [PTAT] voltage and a PTAT current are designed then difference of the PTAT voltage and product of the PTAT current and resistor gives the temperature independent voltage. The advantages of both sub-threshold and strong inversion region operation of MOS transistors are exploited in the design. The voltage reference is implemented using standard CMOS 180 nm technology. The voltage reference provides a voltage of 224.3 mV consuming a quiescent current of 30 μA at room temperature. Post layout simulation results show that the proposed voltage reference has a temperature coefficient of 167.18 ppm/°C and varies only 3mV when there is a ±10% variation in supply voltage. The circuit occupies an area of only 93.6×32.6μm on the chip, making it suitable for area constraint applications.
Keywords: Band-gap reference, Sub 1V voltage reference, PTAT, Temperature coefficient.

Nenad Petrović, Đorđe Kocić
Data-driven Framework for Energy-Efficient Smart Cities
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Abstract: Energy management is one of the greatest challenges in smart cities. Moreover, the presence of autonomous vehicles makes this task even more complex. In this paper, we propose a data-driven smart grid framework which aims to make smart cities energy-efficient focusing on two aspects: energy trading and autonomous vehicle charging. The framework leverages deep learning, linear optimization, semantic technology, domain-specific modelling notation, simulation and elements of relay protection. The evaluation of deep learning module together with code generation time and energy distribution cost reduction performed within the simulation environment also presented in this paper are given. According to the results, the achieved energy distribution cost reduction varies and depends from case to case.
Keywords: Blockchain, Deep learning, Linear programming, Relay protection, Smart grid, Smart city, Smart contract.

Anja Buljević, Miloš Miletić, Aleksandra Mitrović, Mirna N. Kapetina, Milan R. Rapaić
Examples of Robust Controller Design
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Abstract: In this paper two modern controllers are presented. These controllers should eliminate disturbance effect, handle process variations and process uncertainties. First controller that is considered is conventional Proportional – Integral (PI) controller and second one is Fractional PI (FOPI) controller. After testing both controllers on a series of simulations, performance of both control algorithms were applied on a real 3D crane system.
Keywords: PI control, FOPI control, Particle Swarm Optimization (PSO), Symmetrical Optimum Method (SOM), Robust control.

Milica Matić, Milan Tucić, Marija Antić, Roman Pavlović
Using Online Third Party Geolocation Services to Improve Smart Home User Experience
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Abstract: This paper presents one approach to improve smart home user experience, by providing location-based services. Within the cloud of the existing smart home solution, the geolocation micro-service is first implemented. This micro-service communicates with third party online geolocation service to obtain latitude and longitude values from physical address and vice versa. The geolocation micro-service is used by different services to provide location-based experience. For example, weather micro-service uses the geolocation information, to provide weather content, while the traffic service monitors traffic conditions in the vicinity of the household. This information can be used to setup different automation rules in the system.
Keywords: Smart home, cloud, Online third party services, Geolocation, Weather.

Ivana Stojanović, Mladen Koprivica, Nenad Stojanović, Aleksandar Nešković
Analysis of the Impact of Network Architecture on Signal Quality in LTE Technology
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Abstract: In this paper, the impact of the network architecture on signal quality in the fourth generation of the public mobile network is analyzed. The analysis was performed using RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), SINR (Signal to Interference plus Noise Ratio) and throughput parameters in indoor environment. The signal quality parameters were collected by measurement using TEMS Investigation and TEMS Pocket software. The measurements were carried out at the School of Electrical Engineering on the ground floor of the Technical Faculty building for the macro and micro cell scenario. It has been found that better signal quality is ensured in micro cells. Quality of the signal is also considered by the various services provided to the users.
Keywords: LTE, Macro cell, Micro cell, RSRP, RSRQ, SINR, Throughput.

Sandra Veljković, Vojislav Mitić, Vesna Paunović, Goran Lazović, Markus Mohr, Hans Fecht
Analyses of the Surface Parameters in Polycrystalline Diamonds
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Abstract: There is a progressing interests for polycrystalline diamonds and they have been more extensively used recently. This area has been intensively researched due to the outstanding potential of this material, and this necessitated presenting some of the latest application related to engineering in this paper. A better insight of polycrystalline diamonds properties can be achieved by intensively researching the surface structure. Samples of nanocrystalline diamonds grown by the chemical vapor deposition method are analyzed and accordingly, the focus of the research was the surface parameters and their structure. It is observed that waviness and texture are unique for any direction, their values are almost the same for the chosen directions and they vary approximately from –0.2 nm to 0.4 nm. Analyses of the parameters allowed a more detailed insight into the morphology of the surfaces of polycrystalline films.
Keywords: Polycrystalline diamonds; Microelectronic devices; MEMS; Surface properties.

©2020 Serbian Journal of Electrical Engineering