Harvesting Wireless Power: Survey of Energy-Harvester Conversion Efficiency in Far-Field, Wireless Power Transfer Systems
TL;DR: The idea of wireless power transfer (WPT) has been around since the inception of electricity and Nikola Tesla described the freedom to transfer energy between two points without the need for a physical connection to a power source as an?all-surpassing importance to man? as discussed by the authors.
Abstract: The idea of wireless power transfer (WPT) has been around since the inception of electricity. In the late 19th century, Nikola Tesla described the freedom to transfer energy between two points without the need for a physical connection to a power source as an ?all-surpassing importance to man? [1]. A truly wireless device, capable of being remotely powered, not only allows the obvious freedom of movement but also enables devices to be more compact by removing the necessity of a large battery. Applications could leverage this reduction in size and weight to increase the feasibility of concepts such as paper-thin, flexible displays [2], contact-lens-based augmented reality [3], and smart dust [4], among traditional point-to-point power transfer applications. While several methods of wireless power have been introduced since Tesla?s work, including near-field magnetic resonance and inductive coupling, laser-based optical power transmission, and far-field RF/microwave energy transmission, only RF/microwave and laser-based systems are truly long-range methods. While optical power transmission certainly has merit, its mechanisms are outside of the scope of this article and will not be discussed.
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TL;DR: Numerical results unveil a substantial performance gain that can be achieved if the resource allocation design is based on the proposed non-linear energy harvesting model instead of the traditional linear model.
Abstract: In this letter, we propose a practical non-linear energy harvesting model and design a resource allocation algorithm for simultaneous wireless information and power transfer (SWIPT) systems. The algorithm design is formulated as a non-convex optimization problem for the maximization of the total harvested power at energy harvesting receivers subject to minimum required signal-to-interference-plus-noise ratios (SINRs) at multiple information receivers. We transform the considered non-convex objective function from sum-of-ratios form into an equivalent objective function in subtractive form, which enables the derivation of an efficient iterative resource allocation algorithm. In each iteration, a rank-constrained semidefinite program (SDP) is solved optimally by SDP relaxation. Numerical results unveil a substantial performance gain that can be achieved if the resource allocation design is based on the proposed non-linear energy harvesting model instead of the traditional linear model.
863 citations
Cites background from "Harvesting Wireless Power: Survey o..."
...In general, for low power, the RF energy conversion efficiency improves as the input power rises, but there are diminishing returns and limitations on the maximum possible harvested energy, as was evidently proved by field measurements [6]–[8]....
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...In practice, EH circuits [6]–[8] usually result in a non-linear end-to-end wireless power transfer....
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...However, in practice, EH circuits [6]–[8] result in a non-linear end-to-end wireless power transfer....
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TL;DR: In this paper, the authors proposed a unified MEC-WPT design by considering a wireless powered multiuser MEC system, where a multiantenna access point (AP) integrated with an MEC server broadcasts wireless power to charge multiple users and each user node relies on the harvested energy to execute computation tasks.
Abstract: Mobile-edge computing (MEC) and wireless power transfer (WPT) have been recognized as promising techniques in the Internet of Things era to provide massive low-power wireless devices with enhanced computation capability and sustainable energy supply. In this paper, we propose a unified MEC-WPT design by considering a wireless powered multiuser MEC system, where a multiantenna access point (AP) (integrated with an MEC server) broadcasts wireless power to charge multiple users and each user node relies on the harvested energy to execute computation tasks. With MEC, these users can execute their respective tasks locally by themselves or offload all or part of them to the AP based on a time-division multiple access protocol. Building on the proposed model, we develop an innovative framework to improve the MEC performance, by jointly optimizing the energy transmit beamforming at the AP, the central processing unit frequencies and the numbers of offloaded bits at the users, as well as the time allocation among users. Under this framework, we address a practical scenario where latency-limited computation is required. In this case, we develop an optimal resource allocation scheme that minimizes the AP’s total energy consumption subject to the users’ individual computation latency constraints. Leveraging the state-of-the-art optimization techniques, we derive the optimal solution in a semiclosed form. Numerical results demonstrate the merits of the proposed design over alternative benchmark schemes.
752 citations
TL;DR: In this paper, the authors present a comprehensive overview of wireless charging techniques, the developments in technical standards, and their recent advances in network applications, with regard to network applications and discuss open issues and challenges in implementing wireless charging technologies.
Abstract: Wireless charging is a technology of transmitting power through an air gap to electrical devices for the purpose of energy replenishment. The recent progress in wireless charging techniques and development of commercial products have provided a promising alternative way to address the energy bottleneck of conventionally portable battery-powered devices. However, the incorporation of wireless charging into the existing wireless communication systems also brings along a series of challenging issues with regard to implementation, scheduling, and power management. In this paper, we present a comprehensive overview of wireless charging techniques, the developments in technical standards, and their recent advances in network applications. In particular, with regard to network applications, we review the static charger scheduling strategies, mobile charger dispatch strategies and wireless charger deployment strategies. Additionally, we discuss open issues and challenges in implementing wireless charging technologies. Finally, we envision some practical future network applications of wireless charging.
718 citations
01 Jan 2016
TL;DR: This rfid handbook fundamentals and applications in contactless smart cards and identification helps people to read a good book with a cup of coffee in the afternoon instead of juggled with some malicious bugs inside their laptop.
Abstract: Thank you for reading rfid handbook fundamentals and applications in contactless smart cards and identification. As you may know, people have search numerous times for their chosen novels like this rfid handbook fundamentals and applications in contactless smart cards and identification, but end up in malicious downloads. Rather than reading a good book with a cup of coffee in the afternoon, instead they juggled with some malicious bugs inside their laptop.
570 citations
TL;DR: This paper highlights three different energy harvester models, namely, one linear model and two nonlinear models, and shows how WIPT designs differ for each of them in single-user and multi-user deployments, and identifies the fundamental tradeoff between conveying information and power wirelessly.
Abstract: Radio waves carry both energy and information simultaneously. Nevertheless, radio-frequency (RF) transmissions of these quantities have traditionally been treated separately. Currently, the community is experiencing a paradigm shift in wireless network design, namely, unifying wireless transmission of information and power so as to make the best use of the RF spectrum and radiation as well as the network infrastructure for the dual purpose of communicating and energizing. In this paper, we review and discuss recent progress in laying the foundations of the envisioned dual purpose networks by establishing a signal theory and design for wireless information and power transmission (WIPT) and identifying the fundamental tradeoff between conveying information and power wirelessly. We start with an overview of WIPT challenges and technologies, namely, simultaneous WIPT (SWIPT), wirelessly powered communication networks (WPCNs), and wirelessly powered backscatter communication (WPBC). We then characterize energy harvesters and show how WIPT signal and system designs crucially revolve around the underlying energy harvester model. To that end, we highlight three different energy harvester models, namely, one linear model and two nonlinear models, and show how WIPT designs differ for each of them in single-user and multi-user deployments. Topics discussed include rate-energy region characterization, transmitter and receiver architectures, waveform design, modulation, beamforming and input distribution optimizations, resource allocation, and RF spectrum use. We discuss and check the validity of the different energy harvester models and the resulting signal theory and design based on circuit simulations, prototyping, and experimentation. We also point out numerous directions that are promising for future research.
556 citations
Cites background from "Harvesting Wireless Power: Survey o..."
...Moreover the practical implementation of rectenna is hard and subject to several losses due to threshold and reverse-breakdown voltages, devices parasitics, impedance matching, and harmonic generation [5]....
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...This is so because RF-based energy harvesting circuits consist of various components such as resistors, capacitors, and diodes that introduce various nonlinearities [5], [6], [50], [51]....
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...Indeed, e3 of state-of-theart rectifiers drops from 80% at P r rf =10 mW to 40% at 100 μW, 20% at 10 μW and 2% at 1 μW [2], [5]....
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...For typical input powers between 1 μW and 1 mW, low barrier Schottky diodes remain the most competitive and popular technology [5], [6]....
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References
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TL;DR: An improved voltage multiplier technique has been developed for generating +40 V internally in p-channel MNOS integrated circuits to enable them to be operated from standard +5- and -12-V supply rails.
Abstract: An improved voltage multiplier technique has been developed for generating +40 V internally in p-channel MNOS integrated circuits to enable them to be operated from standard +5- and -12-V supply rails. With this technique, the multiplication efficiency and current driving capability are both independent of the number of multiplier stages. A mathematical model and simple equivalent circuit have been developed for the multiplier and the predicted performance agrees well with measured results. A multiplier has already been incorporated into a TTL compatible nonvolatile quad-latch, in which it occupies a chip area of 600 /spl mu/m/spl times/240 /spl mu/m. It is operated with a clock frequency of 1 MHz and can supply a maximum load current of about 10 /spl mu/A. The output impedance is 3.2 M/spl Omega/.
1,726 citations
"Harvesting Wireless Power: Survey o..." refers methods in this paper
...Note that a combination of these approaches is sometimes used; a rectenna harvests energy to create a low voltage that powers a highly efficient dc-dc converter usually based on the traditional Dickson charge pump [16] to increase the voltage to levels capable of powering the electronics....
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TL;DR: Model-integrated computing (MIC), an approach to model-based engineering that helps compose domain-specific design environments rapidly and cost effectively, is particularly relevant for specialized computer-based systems domains-perhaps even single projects.
Abstract: Domain-specific integrated development environments can help capture specifications in the form of domain models. These tools support the design process by automating analysis and simulating essential system behavior. In addition, they can automatically generate, configure, and integrate target application components. The high cost of developing domain-specific, integrated modeling, analysis, and application-generation environments prevents their penetration into narrower engineering fields that have limited user bases. Model-integrated computing (MIC), an approach to model-based engineering that helps compose domain-specific design environments rapidly and cost effectively, is particularly relevant for specialized computer-based systems domains-perhaps even single projects. The authors describe how MIC provides a way to compose such environments cost effectively and rapidly by using a metalevel architecture to specify the domain-specific modeling language and integrity constraints. They also discuss the toolset that implements MIC and describe a practical application in which using the technology in a tool environment for the process industry led to significant reductions in development and maintenance costs.
1,394 citations
TL;DR: A novel fully integrated passive transponder IC with 4.5- or 9.25-m reading distance at 500-mW ERP or 4-W EIRP base-station transmit power, operating in the 868/915-MHz ISM band with an antenna gain less than -0.5 dB.
Abstract: This paper presents a novel fully integrated passive transponder IC with 4.5- or 9.25-m reading distance at 500-mW ERP or 4-W EIRP base-station transmit power, respectively, operating in the 868/915-MHz ISM band with an antenna gain less than -0.5 dB. Apart from the printed antenna, there are no external components. The IC is implemented in a 0.5-/spl mu/m digital two-poly two-metal digital CMOS technology with EEPROM and Schottky diodes. The IC's power supply is taken from the energy of the received RF electromagnetic field with help of a Schottky diode voltage multiplier. The IC includes dc power supply generation, phase shift keying backscatter modulator, pulse width modulation demodulator, EEPROM, and logic circuitry including some finite state machines handling the protocol used for wireless write and read access to the IC's EEPROM and for the anticollision procedure. The IC outperforms other reported radio-frequency identification ICs by a factor of three in terms of required receive power level for a given base-station transmit power and tag antenna gain.
875 citations
"Harvesting Wireless Power: Survey o..." refers background in this paper
...June 2014 117 designs have leveraged CMOS-based Schottky diodes [33], [36]....
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786 citations
"Harvesting Wireless Power: Survey o..." refers background in this paper
...Though still in the experimental stage, researchers working in SPS have made advancements in energy conversion at great distances and high powers (greater than 1 W) to enable electricity to be shared via radio waves, namely collecting solar energy in orbital stations around earth and beaming it to ground stations via microwave power transfer [5], [6], [7]....
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TL;DR: An RF-DC power conversion system is designed to efficiently convert far-field RF energy to DC voltages at very low received power and voltages and is ideal for use in passively powered sensor networks.
Abstract: An RF-DC power conversion system is designed to efficiently convert far-field RF energy to DC voltages at very low received power and voltages. Passive rectifier circuits are designed in a 0.25 mum CMOS technology using floating gate transistors as rectifying diodes. The 36-stage rectifier can rectify input voltages as low as 50 mV with a voltage gain of 6.4 and operates with received power as low as 5.5 muW(22.6 dBm). Optimized for far field, the circuit operates at a distance of 44 m from a 4 W EIRP source. The high voltage range achieved at low load current make it ideal for use in passively powered sensor networks.
766 citations
"Harvesting Wireless Power: Survey o..." refers methods in this paper
...Most of these techniques involve some method of providing additional voltage bias that effectively reduces the threshold voltage [40], [31], [32]....
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