Wireless Power Design
From Theory to Practical Applications in Wireless Energy Transfer and Harvesting
Academy Pro
Title by Mohamed Zied Chaari
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Section 1: An Overview of Wireless Power Technology and Its History
Section 1: An Overview of Wireless Power Technology and Its History
1.3 William Brown
After the progression of microwave tubes in World War II, William initiated his research and development of wireless energy transfer in 1960. He developed a rectifying antenna (rectenna) to convert microwave radiation into direct current (DC). In 1963, he created the first rectifying antennas, achieving a high efficiency of around 50%. His conversion circuit enabled microwave power transmission from tethered to aerial helicopters. Brown and his team accomplished a similar microwave power transmission at the Venus Site in Goldstone, California. The rectifying antenna array, spanning 3.4 meters by 7.2 meters, was 1600 meters from the transmitting parabolic antenna. Figure 2 explains the basis and the concept of the initial and most comprehensive WPT (Wireless Power Transfer) test in 1975.
Energy harvesting, a crucial component of wireless power transmission, is an innovative technology that delivers electricity to historically unreachable locations. This method, known as RF harvesting, is especially significant for its ability to energize electronic devices with minimal power requirements in remote and complex settings. It is also referred to as radio frequency harvesting. It can wirelessly energize electronic gadgets with minimal power usage. Researchers have recently attracted significant interest because they can wirelessly charge sensors in complex environments. Much research has examined wireless power charging by RF energy harvesting. The fundamental principle of this technology is to capture the RF energy surrounding the antenna or receiver to energize sensors. Consequently, the IoT sensors must possess battery-free power supply methods. In the future, substantial resources will be required to sustain IoT devices due to the prevalence of numerous sensors in wireless sensor networks. Consequently, each sensor must be battery-free to ensure maintenance-free operation. Wireless power transfer, or RF energy harvesting, is a promising technique because it can supply power to IoT devices over greater distances than alternative methods, as illustrated in Figure 6.
Numerous distinguished researchers have advanced RF energy harvesting through various approaches and strategies. Chang-Yeob Chu et al. investigated system design for electric car charging, considering a broad spectrum of coupling coefficient variations due to coil misalignment. Koichiro Ishibashi and colleagues proposed the radio frequency characteristics of rectifying devices for ambient energy harvesting. Mohamed Zied et al. examined the influence of wireless power transmission on the future of warfare globally and its implications for ranking nations by military might. The investigation considered two factors: the impact of the microwave power sources and the effect of the distance on the attenuation. They investigated establishing energized IoT sensors through RF energy recovery. Mohamed Zied et al. concluded that all parameters efficiently supply energy to
defined a rectenna as consisting of the parts shown in Figure 8. Usually, a large parabolic antenna is selected as a fixed target of the MPT system because it can capture and collect the maximum amount of energy. It is considered that the receiving antenna is part of the rectifying antenna (Rectenna).
2.4 Cyclotron Wave Rectifier (CWC)
Therefore, we investigate an alternative device that alleviates several principal drawbacks of rectennas, including inadequate output voltage requiring the series arrangement of diodes and a heightened risk of degradation: the potential for danger persists even at modest levels of microwave or direct current overloads and insufficient power output from individual rectenna elements. Perspectives on the Cyclotron Wave Converter (CWC) for converting microwaves into direct current (DC). Nevertheless, its appeal has diminished for prospective high-power industrial wireless power transfer systems. Industrial energy systems consistently require and utilize high-power and high-voltage apparatus to minimize losses and enhance reliability. This section addresses an alternative device that mitigates the principal detrimental characteristics of diode-type rectennas:
• The low power level of a single rectenna element
• Low output voltage and therefore the necessity to connect diodes in series
• The possibility of high breakdown, which is dangerous even at relatively small levels of microwave or DC overloads
Microwaves at any frequency generate a transverse electric field within the coupler gap of the resonant cavity. The resonator is placed within the external magnetic field. Consequently, the electron beam, generated by an electron gun and introduced into the resonator, acquires cyclotron rotation at a specific frequency, which excites a rapid cyclotron wave of the electron beam. The conversion zone follows the resonant cavity, where the external magnetic field alters direction and magnitude. Figure 9 illustrates the principle of CWC developed by Istok Corp.
