The paper's purpose is to describe and discuss the study of LED diodes, measured with the help of the TERALED system. A short description of the measurement system is given. Four batches of 5 mm LEDs and two batches of PowerLED diodes are measured and the comments and discussion of the measured results are given. The experiments show clearly that some manufacturer's LEDs do not match the parameters given in the datasheet. The reasons are not clear, but it seems to us that the problems of degradation of the construction materials of LEDs are not connected with the degradation of the semiconductor material itself.

Abstract.A liquid phase epitaxy technology for deposition of GaAs epilayers on the monocristallic GaAs substrates for high voltage ultra fast power p + -p-i-n-n + GaAs structures has been developed. Proposed technological and hardware solutions of the LPE allow high efficiency of the growing process of diode structures with prescribed ratings and high structural quality of epitaxial layers. A method and technology for the fabrication of GaAs dies for the nanosecond range with reverse voltage up to 1200 V and current up to 100 A in diode chips is introduced. Reverse recovery times down to 20 ns were achieved and could be preserved up to + 260 °С.

Films deposited with the Liquid Phase Epitaxy (LPE) technology on the monocristallic GaAs substrates for high voltage power p+-p-i-n-n+ GaAs structures has been developed. Proposed technological and hardware solutions of LPE allow the high efficiency of growing process of diode structures with defined ratings and high structural quality of epitaxial layers. The method and technology for fabrication of GaAs dies for nanosecond range with reverse voltage up to 1200V and current up to 100A is introduced The reverse recovery time of 20 nsec was achieved and could be preserved up to +260 ºɋ.

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Rapidly increasing usage of telecommunication systems causes new transmission technologies and networks to emerge. Not only the efficiency, reliability and accessibility of the network are important, but also the economic issues. One cost-effective solution could be power line communication (PLC) technology, which transmits data using the existing electricity infrastructure. The application of this communication technique is an attractive and innovative solution for the realization of smart cities and smart homes. With intelligent control networks, energy savings can be optimized and the operating as well as maintenance costs can be reduced. Since outdoor lighting systems are the major consumers of electricity, to create a modern, energy-efficient city, intelligent street lighting control is needed. This paper provides an overview of power line communication principles including the theoretical background of data communication, modulation techniques, channel access methods, protocols, disturbances and noises. Furthermore, in order to highlight the benefits of a PLC-based street lighting control system, a pilot project will be presented. Keywords: intelligent lighting control, modulation techniques, Power line communication, smart city, smart grid.1 INTRODUCTION Power line communication (PLC) is a very attractive technology, which can be used for many applications, such as home automation systems, CCTV cameras, pollution sensors, noise detectors, traffic density sensors, advertising backlit panels, solar applications, energy measurements, street lighting control or vehicle communication networks [1].Energy usage of street lighting accounts for a significant portion of the total energy consumption of a city [2]. In order to reduce energy consumption, CO2 emission, light pollution, to improve public safety and enhance public service quality, implementation of an intelligent light control system is essential [1]. PLC is a natural choice for supporting intelligent lighting control systems in order to ensure the optimal illumination level under any operational circumstances and to reduce operational costs.A PLC network can also be the backbone communication infrastructure for a smart grid, which enables reliable, real-time measurements, monitoring and control [3]. The implementation of this management solution is cost-effective, since the communication is done over the existing power lines and therefore no additional infrastructure is needed. Due to this fact, PLC technology can compete with wireless technology and can be a communication medium in a future smart grid [4].There are three basic network elements for the realization of a PLC system: base station, modem and repeater. PLC technology provides a link between the subscribers and their immediate service provider. The application of PLC in the power supply grid can be considered as a communication solution for the access network. To connect the access network to a wide area network (WAN), a PLC base station is used. To make communication possible over po...