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    Effects of Different Modulation Techniques on Charging Time in RF Energy-Harvesting System
    (Ieee-Inst Electrical Electronics Engineers Inc, 2020) Cansiz, Mustafa; Altinel, Dogay; Kurt, Gunes Karabulut
    Radio-frequency (RF) energy harvesting is a promising technology that obtains energy from electromagnetic waves. As an alternative energy source, this modern technology can provide power wirelessly enabling the practical use of battery-free devices and it is also expected to be widely used in future applications. Many studies have examined the effects of different modulation techniques on power or efficiency in RF energy-harvesting systems. In this article, the effects of different modulation techniques, such as amplitude shift keying (ASK), quadrature amplitude modulation (QAM), phase-shift keying (PSK), and frequency shift keying (FSK) on charging time, were measured and theoretically analyzed in detail. The measurement system was designed using a signal generator, an RF energy-harvesting circuit, and other auxiliary devices. The signal generator produced four different modulated signals as transmit power signals from 1 to 10 dBm at the interval of 1 dBm, and then, the RF energy-harvesting circuit was fed with these power signals. According to the measurement results, four different modulation techniques charged the RF energy-harvesting circuit at different times. It was observed that the 4-ASK modulation technique had the shortest charging time in the range of 1-10 dBm when comparing to QAM, PSK, and FSK modulation techniques, and thus, it was evaluated to be the most suitable modulation technique for the RF energy-harvesting system among these modulation techniques in terms of charging time.
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    Efficiency in RF energy harvesting systems: A comprehensive review
    (Pergamon-Elsevier Science Ltd, 2019) Cansiz, Mustafa; Altinel, Dogay; Kurt, Gunes Karabulut
    One of the most important research areas searches for new sources of energy and for the highest efficiency from existing energy sources. Radio frequency (RF) energy harvesting is a promising alternative to obtain energy for wireless devices directly from RF energy sources in the environment. In this paper, we provide a broad overview of the main blocks of RF energy harvesting systems; which are the wireless transmission medium, the antenna and impedance matching circuit, the rectifier, the voltage multiplier, and the energy storage device or load. The characteristics of these blocks directly affect the performance of an RF energy harvesting system. We mainly focus on the ratio of output and input powers at each block, named as the conversion efficiency and the impedance matching efficiency, which determines the overall efficiency of system. We present detailed information about the system parameters. Thus, we characterize an RF energy harvesting system, which makes the design of system possible to obtain the maximum efficiency and correspondingly the maximum output power, providing the necessary insight about the design of RF energy harvesting systems. (C) 2019 Elsevier Ltd. All rights reserved.
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    Mapping of radio frequency electromagnetic field exposure levels in outdoor environment and comparing with reference levels for general public health
    (Springernature, 2018) Cansiz, Mustafa; Abbasov, Teymuraz; Kurt, M. Bahattin; Celik, A. Recai
    In this study, radio frequency electromagnetic field exposure levels were measured on the main streets in the city center of Diyarbakir, Turkey. Measured electric field levels were plotted on satellite imagery of Diyarbakir and were compared with exposure guidelines published by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). Exposure measurements were performed in dense urban, urban and suburban areas each day for 7 consecutive days. The measurement system consisted of high precision and portable spectrum analyzer, three-axis electric field antenna, connection cable and a laptop which was used to record the measurement samples as a data logger. The highest exposure levels were detected for two places, which are called Diclekent and Batikent. It was observed that the highest instantaneous electric field strength value for Batikent was 7.18 V/m and for Diclekent was 5.81 V/m. It was statistically determined that the main contributor band to the total exposure levels was Universal Mobile Telecommunications System band. Finally, it was concluded that all measured exposure levels were lower than the reference levels recommended by ICNIRP for general public health.
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    Measurement and analysis of significant effects on charging times of radio frequency energy harvesting systems
    (Springer, 2020) Cansiz, Mustafa
    Radio frequency (RF) energy harvesting as an alternative energy source is an emerging technology that supplies energy for low power wireless devices. In this study, the impacts of RF sources, antenna gains, output power levels and path losses on charging times of an RF energy harvesting system were measured and analyzed in detail. An advanced measurement system that consisted of RF sources used as signal generators, dipole and patch antennas, an RF energy harvesting circuit and the other auxiliary devices were installed for acquiring measurement samples. The generated RF power signals in continuous wave mode at 915 MHz carrier frequency were collected wirelessly by the RF energy harvesting circuit for different antenna gains and output power levels at distances from 20 to 50 cm at the interval of 5 cm. The measurement samples were analyzed statistically. According to the measurement results, it was determined that double RF sources, 6.1 dBi antenna gain and 17 dBm output power level reduced the charging times by 63.09%, 59.24% and 46.41% on average, respectively.
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    Mobile measurement of radiofrequency electromagnetic field exposure level and statistical analysis
    (Elsevier Sci Ltd, 2016) Cansiz, Mustafa; Abbasov, Teymuraz; Kurt, Muhammed Bahattin; Celik, Ali Recai
    In this study, radiofrequency electromagnetic field exposure levels were measured as mobile on the main streets of Diyarbakir during a week. The measurements were carried out using high precision spectrum analyzer with an isotropic antenna mounted on the top of a car. With this mobile measurement, large areas were measured in a short time and information about characteristics of electromagnetic environment was obtained quickly. Measurement results showed that measurement values were not in normal distribution and variances between independent variables were not homogeneous. According to Spearman's rho correlation coefficient, there was no strong correlation between measurement days. In terms of mean electric field values, contribution of each band to total band was arranged as UMTS DL, GSM900 DL, GSM1800 DL, TV4-5, FM, and TV3 band, respectively. It was determined that all measurement values were below the reference levels of the International Commission on Non-Ionizing Radiation Protection. (C) 2016 Elsevier Ltd. All rights reserved.