68,624 research outputs found
Nonradiating sources for efficient wireless power transfer
Nonradiating sources of energy realized under a wave scattering on high-index dielectric nanoparticles have attracted a lot of attention in nano-optics and nanophotonics. They do not emit energy to the far-field, but simultaneously provides strong near-field energy confinement. Near-field wireless power transfer technologies suffer from low efficiency and short operation distance. The key factor to improve efficiency is to reduce the radiation loss of the resonators included in the transmitter and receiver. In this paper, we develop a wireless power transfer system based on nonradiating sources implemented using colossal permittivity dielectric disk resonator and a subwavelength metal loop. We demonstrate that this nonradiating nature is due to the hybrid anapole state originated by destructive interference of the fields generated by multipole moments of different parts of the nonradiating source, without a contribution of toroidal moments. We experimentally investigate a wireless power transfer system prototype and demonstrate that higher efficiency can be achieved when operating on the nonradiating hybrid anapole state compared to the systems operating on magnetic dipole and magnetic quadrupole modes due to the radiation loss suppression. © 2021 Esmaeel Zanganeh et al., published by De Gruyter, Berlin/Boston
Waveform Optimization and Beam Focusing for Near-field Wireless Power Transfer with Dynamic Metasurface Antennas and Non-linear Energy Harvesters
Radio frequency (RF) wireless power transfer (WPT) is a promising technology
for future wireless systems. However, the low power transfer efficiency (PTE)
is a critical challenge for practical implementations. One of the main
inefficiency sources is the power consumption and loss introduced by key
components such as high-power amplifier (HPA) and rectenna, thus they must be
carefully considered for PTE optimization. Herein, we consider a near-field
RF-WPT system with the emerging dynamic metasurface antenna (DMA) at the
transmitter and non-linear energy harvesters. We provide a mathematical
framework to calculate the power consumption and harvested power from
multi-tone signal transmissions. Then, we propose an approach relying on
alternating optimization and successive convex approximation for waveform
optimization and beam focusing to minimize power consumption while meeting
energy harvesting requirements. Numerical results show that increasing the
transmit tones reduces the power consumption by leveraging the rectifier's
non-linearity. Moreover, it is demonstrated that increasing the antenna length
improves the performance, while both DMA and fully-digital architectures may be
favorable depending on the setup. Finally, our results verify that the
transmitter generates accurate energy beams pointed to devices located in the
near-field, while energy beams are formed in devices' direction in the
far-field region.Comment: 13 pages, 12 figure
Near-Field Wireless Power Transfer with Dynamic Metasurface Antennas
Radio frequency wireless power transfer (WPT) enables charging low-power mobile devices without relying on wired infrastructure. Current existing WPT systems are typically designed assuming far-field propagation, where the radiated energy is steered in given angles, resulting in limited efficiency and possible radiation in undesired locations. When large arrays at high frequencies, such as dynamic metasurface antenna (DMA), are employed, WPT might take place in the radiating nearfield (Fresnel) region where spherical wave propagation holds, rather than plane wave propagation as in the far-field. In this paper, we study WPT systems charging multiple devices in the Fresnel region, where the energy transmitter is equipped with an emerging DMA, exploring how the antenna configuration can exploit the spherical wavefront to generate focused energy beams. In particular, after presenting a mathematical model for DMA-based radiating near-field WPT systems, we characterize the weighted sum-harvested energy maximization problem of the considered system, and we propose an efficient solution to jointly design the DMA weights and digital precoding vector. Simulation results show that our design generates focused energy beams that are capable of improving energy transfer efficiency in the radiating near-field with minimal energy pollution
SWIPT in Mixed Near- and Far-Field Channels: Joint Beam Scheduling and Power Allocation
Extremely large-scale array (XL-array) has emerged as a promising technology
to enhance the spectrum efficiency and spatial resolution in future wireless
networks by exploiting massive number of antennas for generating pencil-like
beamforming. This also leads to a fundamental paradigm shift from conventional
far-field communications towards the new near-field communications. In contrast
to the existing works that mostly considered simultaneous wireless information
and power transfer (SWIPT) in the far field, we consider in this paper a new
and practical scenario, called mixed near- and far-field SWIPT, where energy
harvesting (EH) and information decoding (ID) receivers are located in the
near- and far-field regions of the XL-array base station (BS), respectively.
Specifically, we formulate an optimization problem to maximize the weighted
sum-power harvested at all EH receivers by jointly designing the BS beam
scheduling and power allocation, under the constraints on the maximum sum-rate
and BS transmit power. First, for the general case with multiple EH and ID
receivers, we propose an efficient algorithm to obtain a suboptimal solution by
utilizing the binary variable elimination and successive convex approximation
methods. To obtain useful insights, we then study the joint design for special
cases. In particular, we show that when there are multiple EH receivers and one
ID receiver, in most cases, the optimal design is allocating a portion of power
to the ID receiver for satisfying the rate constraint, while the remaining
power is allocated to one EH receiver with the highest EH capability. This is
in sharp contrast to the conventional far-field SWIPT case, for which all
powers should be allocated to ID receivers. Numerical results show that our
proposed joint design significantly outperforms other benchmark schemes without
the optimization of beam scheduling and/or power allocation.Comment: In this paper, we consider a new scenario of mixed-field SWIPT, and
studied efficient beam scheduling and power allocation. The paper is accepted
to JSAC. arXiv admin note: substantial text overlap with arXiv:2304.0794
Studying the Cultural History of Victorian Science
Far-field microwave power transfer (MPT) will free wireless sensors and other mobile devices from the constraints imposed by finite battery capacities. Integrating MPT with wireless communications to support simultaneous wireless information and power transfer (SWIPT) allows the same spectrum to be used for dual purposes without compromising the quality of service. A novel approach is presented in this paper for realizing SWIPT in a broadband system where orthogonal frequency division multiplexing and transmit beamforming are deployed to create a set of parallel sub-channels for SWIPT, which simplifies resource allocation. Based on a proposed reconfigurable mobile architecture, different system configurations are considered by combining single-user/multi-user systems, downlink/uplink information transfer, and variable/fixed coding rates. Optimizing the power control for these configurations results in a new class of multi-user power-control problems featuring the circuit-power constraints, specifying that the transferred power must be sufficiently large to support the operation of the receiver circuitry. Solving these problems gives a set of power-control algorithms that exploit channel diversity in frequency for simultaneously enhancing the throughput and the MPT efficiency. For the system configurations with variable coding rates, the algorithms are variants of water-filling that account for the circuit-power constraints. The optimal algorithms for those configurations with fixed coding rates are shown to sequentially allocate mobiles their required power for decoding in ascending order until the entire budgeted power is spent. The required power for a mobile is derived as simple functions of the minimum signal-to-noise ratio for correct decoding, the circuit power and sub-channel gains. © 1991-2012 IEEE.link_to_subscribed_fulltex
Wireless powering efficiency assessment for deep-body implantable devices
Several frequency-dependent mechanisms restrict the maximum achievable
efficiency for wireless powering implantable bioelectric devices. Similarly,
many mathematical formulations have been proposed to evaluate the effect of
these mechanisms as well as predict this maximum efficiency and the
corresponding optimum frequency. However, most of these methods consider a
simplified model, and they cannot tackle some realistic aspects of implantable
wireless power transfer. Therefore, this paper proposed a novel approach that
can analyze the efficiency in anatomical models and provide insightful
information on achieving this optimum operation. First, this approach is
validated with a theoretical spherical wave expansion analysis, and the results
for a simplified spherical model and a bidimensional human pectoral model are
compared. Results have shown that even though a magnetic receiver outperforms
an electric one for near-field operation and both sources could be equally
employed in far-field range, it is in mid-field that the maximum efficiency is
achieved, with an optimum frequency between 1-5 GHz, depending on the
implantation depth. In addition, the receiver orientation is another factor
that affects the efficiency, with a maximum difference between the best and
worst-case scenarios around five times for an electric source and over 13 times
for the magnetic one. Finally, this approach is used to analyze the case of a
wirelessly powered deep-implanted pacemaker by an on-body transmitter and to
establish the parameters that lead to the maximum achievable efficiency
Wireless Far-field Charging of Quadcopters: WPT System
In this study, wireless power transfer using a transmitting horn antenna and receiving module is designed and analyzed. The receiving module comprises transmitting (horn) and receiving antennas, rectifier, and power management unit. The receiving antenna is used at a frequency of 2.45 GHz which seems to be the most efficient one. The integrated system being low in weight is suitable to be placed on any system having a battery with recharging characteristics. The compact system is designed and simulated using CST STUDIO. The receiving module is used for the conversion of microwave power to DC power for the easy charging of a Quadcopter. Drones always carry a minimal amount of payload and hence require a low weight power receiving system. The integration of 3 by 4 antenna array with the power management circuit makes it of minimal weight which is effective for UAVs. The distance taken into consideration is from 1 to 6m which works in relation to the power transmitted. Far-field transfer is designed and calculated but the method of improving the efficiency to a greater distance is still a concern of research
Energy Beamforming with One-Bit Feedback
Wireless energy transfer (WET) has attracted significant attention recently
for providing energy supplies wirelessly to electrical devices without the need
of wires or cables. Among different types of WET techniques, the radio
frequency (RF) signal enabled far-field WET is most practically appealing to
power energy constrained wireless networks in a broadcast manner. To overcome
the significant path loss over wireless channels, multi-antenna or
multiple-input multiple-output (MIMO) techniques have been proposed to enhance
the transmission efficiency and distance for RF-based WET. However, in order to
reap the large energy beamforming gain in MIMO WET, acquiring the channel state
information (CSI) at the energy transmitter (ET) is an essential task. This
task is particularly challenging for WET systems, since existing channel
training and feedback methods used for communication receivers may not be
implementable at the energy receiver (ER) due to its hardware limitation. To
tackle this problem, in this paper we consider a multiuser MIMO system for WET,
where a multiple-antenna ET broadcasts wireless energy to a group of
multiple-antenna ERs concurrently via transmit energy beamforming. By taking
into account the practical energy harvesting circuits at the ER, we propose a
new channel learning method that requires only one feedback bit from each ER to
the ET per feedback interval. The feedback bit indicates the increase or
decrease of the harvested energy by each ER between the present and previous
intervals, which can be measured without changing the existing hardware at the
ER. Based on such feedback information, the ET adjusts transmit beamforming in
different training intervals and at the same time obtains improved estimates of
the MIMO channels to ERs by applying a new approach termed analytic center
cutting plane method (ACCPM).Comment: This is the longer version of a paper to appear in IEEE Transactions
on Signal Processin
Contactless Energy Transfer Techniques for Industrial Applications. Power and Data Transfer to Moving Parts
Contactless energy transfer (CET) systems are gaining increasing interest in the automatic machinery industries. For this reason, circuit equivalent networks of CET systems considered in the literature are introduced with emphasis on their industrial applicability. The main operating principles and the required compensating networks, along with different topologies of power supplies optimised for wireless powering, are discussed. The analysis of the wireless transfer, at the maximum efficiency, of high power levels shows that, in the kHz range, highly coupled inductive links are needed and soft-switching power sources required. The employment of CET units in controlled systems requires combining a link for data communication with the wireless power channel. At low frequencies, capacitive and inductive couplings are integrated in a unique platform to implement the wireless data and power links, respectively. Differently, at UHF, an increased data channel transfer efficiency is made possible by exploiting auto-resonant structures, such as split-ring resonators instead of capacitances, one at each far-end side of the link. The design procedure of a power CET system, including the dc/ac converter, a rotary transformer and its windings, is discussed and the results presented. A different version of a WPT system, which involves multiple transmitting coils and a sliding receiver, is also presented. A low frequency RFID capacitive data link is then combined with the rotary CET unit to provide the temperature feedback of a controlled system, wherein the rectifying part of a passive tag is exploited to simultaneously power and read a temperature probe. Subsequently, a split-ring based near-field UHF data link is designed to ensure an improved temperature detection in terms of accuracy and resolution. The sensor readout is performed at the transmitter side by measuring the reflected power by the load rectifier
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