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In this study, charging time in RF energy harvesting systems is measured and statistically analyzed. The measurement system is carried out using an RF energy harvesting circuit, transmitters as RF sources, a patch antenna and other auxiliary devices. The RF power signals generated by single, double and triple RF sources are collected wirelessly by the RF energy harvesting circuit at distances from 1 to 5 m at the interval of 0.5 m. Measurement samples for the charging time are recorded and then evaluated. Test of normality using Kolmogorov–Smirnov shows that the measurement samples of the single, double and triple RF sources are not in a normal distribution. Based on Spearman's rho correlation coefficient, it is detected that there is no strong correlation among the measurement samples at different distances for each RF source. Additionally, it is observed that received power distributions of the RF sources match the charging time values. Based on the experimental results, charging time models are proposed for the single, double and triple RF sources. As a result, it is determined that there is a good match between the proposed models and the charging time values. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. • A broad overview of main blocks of RF energy harvesting systems. • Characteristic of circuits affecting the performance of RF energy harvesting. • Overall efficiency of RF energy harvesting systems. • Necessary insight about the design of RF energy harvesting systems. [ABSTRACT FROM AUTHOR]

In this study, radiofrequency electromagnetic field exposure levels were measured as mobile on the main streets of Diyarbakır 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. [ABSTRACT FROM AUTHOR]