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I applied photovoltaic cells equipped with singlet fission (SF) of molecular systems to dual-wavelength laser power converters (DW-LPCs) that efficiently convert two laser lights of different wavelengths to electricity. When the SF-DW-LPC is illuminated by eye-safe laser light of 1470 nm wavelength emitted from a laser diode, a single photon is converted to a single carrier. On the other hand, a single high-energy photon emitted from a high-power and low-cost laser diode of 808 nm is converted to two carriers by SF owing to its endothermic feature, even though the photon energy is slightly lower than twice the fundamental energy gap. Furthermore, the SF-DW-LPC operates as a highly efficient solar cell. These functions are required for optical wireless power transmission to moving objects including electric vehicles and flying drones. I modeled the photovoltaic process with SF and evaluated the limiting conversion efficiencies by detailed-balance calculations. Conversion efficiencies of the SF-DW-LPC for these two laser lights are competitive with those of the conventional single-junction LPCs dedicated to these wavelengths, respectively. The efficiency under solar light is close to that of the optimally designed SF solar cell. Furthermore, the SF-DW-LPC outperforms other types of DW-LPCs designed on the basis of intermediate band, triplet–triplet annihilation, and multiple exciton generation solar cells. Endothermic SF and carrier/energy extraction into the neighboring acceptors have already been demonstrated. However, molecular systems that apply to 1470 nm have not yet been realized, which is the top-priority issue to be solved to realize highly efficient SF-DW-LPCs. [ABSTRACT FROM AUTHOR]

In this paper, the effects of hydrostatic stress on the magnetic properties of Mn-Zn power ferrites are discussed. Ring cores were embedded in cement and the curing process gradually exerted pressure on the core. A novel testing method was developed to continuously measure the power losses and the magnetic susceptibility in dependence on magnetic excitation at a fixed frequency and room temperature with a vector network analyzer. After 450 h, a maximum compressive stress of 120 MPa was reached. Power loss up to 300% was observed, while magnetic susceptibility dropped by 35%. The magneto-mechanical effect on core losses was simulated with the Hodgdon–Esguerra hysteresis model, showing excellent agreement with tested results, which allows us to predict the behavior of ferrite tiles embedded in load-bearing surfaces for wireless power transfer (WPT) applications. [ABSTRACT FROM AUTHOR]

Metasurfaces, due to their outstanding ability to control electromagnetic waves, have great application prospects in the field of wireless communication. This paper provides a comprehensive review of research work based on metasurface in three aspects: wireless power transfer, wireless information transmission, and novel wireless transceiver architectures. In the domain of wireless power transfer, several focusing metasurfaces and systems with unique performance are presented along with a new formula for calculating wireless power transfer. Concerning wireless information transmission section, the direct digital information transmission based on metasurface and the information transmission based on space-time-coding digital metasurface are introduced. Lastly, a simplified wireless transceiver with metasurfaces was introduced. The paper concludes with a discussion on the future directions of metasurfaces in the wireless communication domain. [ABSTRACT FROM AUTHOR]

In this paper, a wideband metasurface-loaded (MTS-L) rectenna system is proposed to capture electromagnetic (EM) energy at arbitrary azimuth angles. The radiation patterns of different modes in the original MTS configuration are analyzed using the characteristic mode theory, and potential modes with omnidirectional radiation are screened out. By the arrangement of patches, the roundness performance of the radiation pattern can be ameliorated, and the omnidirectional characteristic is obtained over a wide frequency band. Subsequently, the surface current density of the selected mode is carefully and artificially designed to facilitate probe excitation as well as refrain from introducing complex power-combining networks. A wideband rectifier circuit is designed as the load of the proposed antenna. Eventually, measured results show that it operates from 4.6 to 9.6 GHz with a fractional bandwidth of 70.4%, and the peak system efficiency is 52.2%. The proposed system demonstrates excellent potential for wireless power transmission and EM energy harvesting in indoor environments. [ABSTRACT FROM AUTHOR]

Microwave wireless power transmission (MWPT) applications have attracted worldwide interest and attention in recent years. Rectennas are a crucial component of a MWPT system. The rectenna's power capacity and output DC power have great significance with regard to the MWPT system's performance. In this article, a compact 4 × 4 S-band rectangular patch rectenna array for MWPT is proposed and experimentally verified. Firstly, an S-band rectifier with better consistency and lower cost than a traditional output design using parallel capacitors as a filter is achieved. Then, a rectenna array based on the proposed rectifier and a novel design idea is proposed. The rectenna can achieve an output DC power of 117.6 mW/cm3 and an efficiency of 47.6%. Finally, a MWPT verification experiment is conducted. A 12-inch LCD screen powered by the rectenna with a rated power of 12 W successfully works without any other power supply. This article provides a new design of a rectenna for MWPT, and the proposed rectenna array demonstrates its good engineering significance and application prospects. [ABSTRACT FROM AUTHOR]

Acoustofluidics has shown great potential in enabling on‐chip technologies for driving liquid flows and manipulating particles and cells for engineering, chemical, and biomedical applications. To introduce on‐demand liquid sample processing and micro/nano‐object manipulation functions to wearable and embeddable electronics, wireless acoustofluidic chips are highly desired. This paper presents wireless acoustofluidic chips to generate acoustic waves carrying sufficient energy and achieve key acoustofluidic functions, including arranging particles and cells, generating fluid streaming, and enriching in‐droplet particles. To enable these functions, the wireless acoustofluidic chips leverage mechanisms, including inductive coupling‐based wireless power transfer (WPT), frequency multiplexing‐based control of multiple acoustic waves, and the resultant acoustic radiation and drag forces. For validation, the wirelessly generated acoustic waves are measured using laser vibrometry when different materials (e.g., bone, tissue, and hand) are inserted between the WPT transmitter and receiver. Moreover, the wireless acoustofluidic chips successfully arrange nanoparticles into different patterns, align cells into parallel pearl chains, generate streaming, and enrich in‐droplet microparticles. This research is anticipated to facilitate the development of embeddable wireless on‐chip flow generators, wearable sensors with liquid sample processing functions, and implantable devices with flow generation and acoustic stimulation abilities for engineering, veterinary, and biomedical applications. [ABSTRACT FROM AUTHOR]

Multi-dimensional wireless power transmission is a critical element in the development of capsule robots. To solve the problem caused by the increasing number of functions of new capsule robots and the fact that the traditional three-dimensional receiving coil occupies excessive inner space, a two-dimensional square transmitting coil with an embedded ferrite core is proposed. The proposed transmitting coil consists of two pairs of rectangular solenoid coils distributed radially along the human body. By changing the direction of the current flow, it can generate a two-dimensional magnetic field covering the whole central plane. This paper presents a theoretical model and conducts finite element simulations to analyze the magnetic flux density in the center plane. To evaluate the effectiveness of the proposed system, two prototypes of transmitting coils with and without ferrite cores are created, tested and compared to assess the performance improvements. Results indicate that the transmitting coil with a ferrite core increases the power transfer efficiency from 5.07% to 6.11%. In addition, attitude experiments reveal that the receiving coil efficiently captures sufficient energy at various angles when operated in the center plane. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) is an emerging technology that enables the wireless transfer of electrical energy from power supplies to electrical equipment. It has been widely used in electric vehicles, mobile phones, household appliances, medical devices, and other fields. However, the frequency splitting and bifurcation phenomena existing in WPT systems are the fundamental obstacles and challenges that affect the effective operation of WPT systems. In this paper, a method based on the fractional‐order circuit is proposed to simultaneously suppress the frequency splitting and bifurcation phenomena by changing the order of fractional‐order capacitor. By replacing the compensation capacitor in the transmitter of the traditional WPT system with a fractional‐order capacitor, a fractional‐order WPT system is formed. Then, using fractional calculus and circuit theory, the mathematical model of the proposed WPT system containing a fractional‐order capacitor is established, and the frequency splitting and bifurcation phenomena are analyzed. The theoretical results show that the frequency splitting and bifurcation phenomena are suppressed only by adjusting the order of fractional‐order capacitor, and the output power of the original resonant frequency is improved. Finally, the experimental prototype is implemented to validate the theoretical results. [ABSTRACT FROM AUTHOR]

Summary: The magnetic couplers play an important role in electric vehicle (EV) wireless power transfer (WPT) systems. Conversational coupling structures are mainly based on unipolar, bipolar, and quadrupole coils, and the interoperability among them cannot be achieved. To solve the interoperability problem in the coupling structure, a novel bipolar coil structure is proposed in this paper. Energy transfer with unipolar and bipolar coils is achieved by interconnecting unipolar and bipolar types crosswise in the same plane and combining them with the corresponding topologies. They are connected in series on the dc side. An experimental prototype is built to verify the interoperability performance of the proposed novel bipolar coil structure. The proposed novel bipolar coil structure can be compatible with unipolar, bipolar, and quadrupole coils and achieve a maximum dc‐dc efficiency of more than 85%. [ABSTRACT FROM AUTHOR]

Summary: With the increasing demand for the constant voltage (CV) charging of multiple loads, this article proposes an LC compensated wireless power transfer (WPT) system with multiple load‐independent CV outputs function. Each transmission channel consists of a compensation capacitor and a compensation inductor forming a resonant loop. By configuring different combinations of compensation inductor and capacitor for each transmission channel, different CV outputs can be achieved without affecting the output voltages of other transmission channels. In addition, the proposed system can achieve near zero phase angle (ZPA) and zero‐voltage switching (ZVS) operations, thereby improving system efficiency. Firstly, a detailed theoretical derivation of the proposed system with multiple load‐independent CV outputs and ZPA operation is performed, and the detailed parameter design process is provided. Secondly, the implementation method of ZVS operation is introduced and verified through simulation. Finally, an experimental prototype of two transmission channels is taken as an example to verify the correctness and rationality of the proposed system. [ABSTRACT FROM AUTHOR]

Summary: Inductive power transmission (IPT) and capacitive power transmission (CPT) are currently the two main wireless power transfer technologies. Hybrid power transmission (HPT) systems that combine IPT and CPT can improve transmission performance and are more attractive for some charging applications such as electric bicycles (e‐bikes). However, HPT systems are more sensitive to parameter variations, and the coupling mechanism is prone to misalignment during wireless charging. Therefore, achieving stable output power and constant transfer efficiency over a wide range of coupling coefficient variations is still a major challenge for HPT systems. In this work, the parity–time (PT) symmetry theory is applied to an SS‐type HPT system, and a circuit model of the PT‐based HPT system is developed by using coupling capacitance and coupling inductance. The effect of connecting the plates to the homonymous end or heteronymous end of the coupling coils on the PT symmetry range of the HPT system is discussed. It is found that the heteronymous end connection of the coils can effectively increase the range of constant output power and stable transfer efficiency. Finally, a prototype is built to verify the feasibility and effectiveness of the proposed PT‐based HPT system. The transfer power and efficiency remain constant in the PT‐symmetric range, and the inductive and capacitive coupling coefficients are smaller compared to IPT and CPT systems with the same parameters. [ABSTRACT FROM AUTHOR]

Electromagnetic metamaterial (EM metamaterial) with a double‐layer spiral structure is often used to enhance the transmission efficiency of wireless power transfer (WPT). When EM metamaterial is used as an array, its AC resistance and loss cannot be ignored due to the high‐frequency magnetic field of WPT. This paper decreases EM metamaterial's loss by increasing its quality factor according to the quality factor theory and proposes a novel structure. This structure adopts a non‐uniform linewidth, which can decrease the proximity effect resistance of the EM metamaterial as well as maintain its high inductance. When using the proposed EM metamaterial to form an array, to enhance its effect in modulating the magnetic field, a hybrid EM metamaterial slab (HMS) is constructed by adjusting the series resonance capacitor. The corresponding samples of EM metamaterial with the non‐uniform linewidth structure are developed. The experiment results prove that compared to the uniform linewidth structure, the equivalent resistance and loss of the non‐uniform linewidth structure respectively are decreased by about 5.48% and 19.73%, and the quality factor is enhanced to 556.874. The HMS constructed by the proposed EM metamaterial can enhance the transmission efficiency of the experimental WPT system to 59.8%, which is about 2.1% higher than the HMS constructed by the normal EM metamaterial. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) has recently been found to be a promising modality in several applications, especially in electric vehicle (EV) technology. EV's contactless power transfer systems must be highly efficient, reliable, lightweight, and low-cost. The WPT assembly must have a large air gap between the transmitting and receiving coil and preferably should be less sensitive to lateral, horizontal, and angular misalignments. A novel, highly efficient, and reliable honeycomb coupler-based WPT (HC-WPT) coil assembly has been proposed for EV charging. The proposed HC-WPT coil system has been designed and used FEA (finite element analysis) to optimize the shape of the coupler based on high coupling coefficient (k), mutual inductance (M), efficiency, and weight simulated, and validated through Ansys Maxwell software. A rigorous study has been conducted on coupler-weight and cost optimization with the effect of aluminum shielding. The magnetic flux linkage and the associated losses in the ferrite core and copper winding have also been studied to ensure system efficiency. The results obtained from the Ansys-based modeling and simulation demonstrate that the HC-based WPT system is more effective, resilient to coil misalignment, and lighter in weight than conventional models. Magnetic coupling coefficient (k), self-inductance (L), mutual inductance (M), and quality factor (Q), magnetic flux density (B), magnetic field intensity (H) are calculated in Ansys Maxwell software, losses in coil, ferrite core with aluminum shielding find through Ansys and the electromagnetic parameters are used in Ansys-TwinBuilder to calculate the power transfer capability and efficiency. It is observed that the proposed HC-WPT assembly with a 150-mm air gap can transfer 4.29 kW electric power at an efficiency of 94.07% across 200 Ohm load resistance at a resonance frequency of 85 kHz. The novel HC-WPT system is compact, lightweight, low-cost, and has high power transfer efficiency, which could be promisingly implemented for EV-wireless charging applications. [ABSTRACT FROM AUTHOR]

This paper presents series-series (SS) compensation topologies that include both primary side duty cycle control (PSDCC) and secondary side duty cycle control (SSDCC) methods. The main challenge for noncontact charging (NCC) for electric vehicles (EVs) batteries, the power transfer capability and efficiency in primary side proved to be unproductive. The investigation considers the primary side control duty cycle control (transmitter and receiver) and the secondary side duty cycle control (transmitter and receiver) in terms of compensation capacitor voltage, coil voltage, load side voltage, current, and power. By adjusting the duty cycle within the range of 0.1 to 0.5, it is possible to control power without significantly decreasing the system's efficiency, by using the SSDCC method. The evaluated parameters, including 1.5 kW output power, 85 kHz resonance frequency, and 120 mm ground clearance, are suitable for three-wheeler auto rickshaws. These findings are verified through MATLAB/Simulink software and compared with experimental results. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to analyze the importance and performance of customer-facing technologies in luxury hotels. The study also assessed differences between and within the four generations in the importance-performance analysis (IPA). Design/methodology/approach: Data were collected using a Qualtrics panel of recent luxury hotel customers in the USA belonging to all four generations. The cross-generational IPA was conducted using t-tests and (ANAOVA). Findings: The IPA matrix concentrated most technology items in either low importance – low performance or high importance – high performance quadrants. One-way ANOVA revealed significant differences between generations on the importance ratings of all technology items except wireless charging power solutions and on the performance ratings of all technology items. Furthermore, post hoc tests indicated that millennials rated luxury technology most favorably among the four cohorts, followed by generations Z, X and Baby Boomers. In addition, significant differences between the importance and performance of many technology items within each generational cohort were observed. Overall, Wi-Fi was unanimously ranked across generations as the most important technology among luxury guests, but it was the only one that scored lower in performance than importance. Research limitations/implications: The findings of this study contribute to hospitality scholarship in two primary ways: the importance and performance of technology and generational differences. The results advance the understanding of the impact of generational factors on customer-facing technological adoptions in the luxury hotel sector. Practical implications: Technologies that are pervasive in the home also become vital offerings for hotels. The more pervasive technology, the more a luxury hotel must work to ensure that it performs at optimal levels. Additionally, which technologies are most important to targeted generations are provided so practitioners may budget for their implementation. Originality/value: This research is a pivotal step forward in unraveling the intricate interplay between generational factors and technological evaluations, providing a foundation for future research and practical applications in a rapidly evolving technological landscape in the hospitality industry. [ABSTRACT FROM AUTHOR]

In the field of wireless power transmission (WPT) for electric vehicles, the challenge of magnetic shielding technology is particularly prominent. Achieving effective magnetic shielding often comes at the cost of transmission efficiency, creating a significant technical bottleneck. As a result, research into improving transmission efficiency while minimizing magnetic leakage has become a primary focus in the industry. This is seen as critical for driving the sustainable development of the electric vehicle sector. In response to this challenge, this paper presents the construction of an active magnetic shield using an isotropic coil configuration, which not only optimizes system efficiency but also significantly reduces magnetic leakage in WPT systems. The paper begins by introducing the concept of an active magnetically shielded isotropic coil structure for wireless power transmission. Next, it details the design methodology and operational principles of the structure, followed by the derivation of the mathematical model and equivalent circuit. The effectiveness of the magnetic shielding mechanism is examined from a theoretical standpoint, and the influence of coil parameters on both shielding performance and transmission efficiency is analyzed. Finally, based on the optimized coil parameters, the design of the wireless charging system incorporating the magnetic shielding structure is completed. This includes relevant theoretical calculations, simulation analyses, and experimental validation to confirm the feasibility of the design. The results demonstrate that the active magnetically shielded isotropic coil significantly reduces magnetic leakage, lowering it by approximately 95.68% compared to traditional coils, while achieving a transmission efficiency of 95.68% in experiments. [ABSTRACT FROM AUTHOR]

A wireless electrochemiluminescence (ECL) device employing the wireless reverse charging function or on-the-go (OTG) USB transmission function of smartphones is designed. It was coupled with a multi-channel single-electrode electrochemical system based on the resistance-induced potential difference for multiple ECL analyses using a smartphone as the detector. [ABSTRACT FROM AUTHOR]

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In the work presented in this paper, the performance of a wireless power transfer system is shown to be enhanced by means of a metamaterial slab utilized as a reflector. The metamaterial slab investigated is a 2D design consisting of a 5 × 5 array of double square split ring resonator cells. It has a near-field mu-near-zero (MNZ) and mu-negative (MNG) characteristic near the target frequency of 2.4 GHz. The array is physically compact having an area of 12.5 × 12.5 cm2. The WPT system considered in the given work is a system of two 10-turn coils separated by a distance of 20 mm. Considerable improvement in the performance is observed in terms of S-parameters and the coupling coefficient after the application of the metamaterial slab reflector. Measurements performed on the fabricated prototype validate the potentiality of the proposed metamaterial structure for improving the efficiency of a wireless power transfer system. [ABSTRACT FROM AUTHOR]

This study proposes a novel topology with bi‐stable controlling for wireless charging system (WCS). The advantage of the proposal is that a desired charging current can be directly output from rectifier without requiring charging current manager, thereby greatly simplifying the structure of the receiver. The proposed topology not only improves the transmission efficiency of system, but also reduces the loss and heat dissipation in the receiver. The principle of the topology is outlined and the circuitry model and control strategy are established and analyzed in detail. The innovation of this method lies in treating the coupler as a current transformer, which enables more direct and simpler controlling of the charging current. The experiment is conducted to verify that when the peak charging current is increased from 5A to 10A, the system efficiency is increased up to 82.0% and the receiver efficiency up to 96.7%. Both computational simulation and experimental validation have confirmed the feasibility of the proposed method. Compared with conventional WCS topology with compensation, the proposed method improves the system efficiency by 3% and the receiver efficiency by 5%, which is more suitable for practical applications where compact and light‐weight receiver is required. [ABSTRACT FROM AUTHOR]

Three‐dimensional (3D) wireless power transfer (WPT) is an attractive methodology to improve the charging safety and flexibility of portable electronic equipment and to meet the charging demand brought by the increase of electronic equipment. Herein a 3D WPT system using a cylindrical transmitting coil excited by a single power source is proposed to improve flexibility and efficiency. Specifically, the coil size is designed and the circuit model is analyzed. A method for determining inductor parameters of Inductor‐Capacity‐Capacity compensation is designed to achieve high efficiency. The power transmission performance of the WPT system is validated through an experimental platform. The measured maximum power is more than 50 W, and the maximum DC‐DC efficiency is up to 82.3%. The system can simultaneously charge multiple loads with different receiving coils at different positions. The proposed WPT system can improve the flexibility of equipment charging without control, and provide a reference for the design of portable equipment high efficiency wireless chargers. [ABSTRACT FROM AUTHOR]

Due to the existence of the evaporation duct near‐sea‐surface described as an inhomogeneous refractive index of atmosphere, microwaves can be trapped in the duct and propagate along it. To investigate wireless power transfer (WPT) over the sea surface, we utilize the two‐dimensional parabolic equation to calculate the electric field distribution and to obtain the transferred power. By analysing the propagation results with specific evaluation functions, we obtained the proper conditions for long‐distance WPT over the sea surface. When the initial field distributes uniformly on the one‐meter aperture, the frequency is 12 GHz, and the centre position is 4 m, a unique focusing spot can be obtained in the duct and nearly 5%, 8%, and 12% of the initial power remains at a distance of 10 km with a receiving aperture of 1, 2, and 3 m, respectively. The presented WPT scheme near the sea surface has potential applications in the power supply or charging for ships or small islands. [ABSTRACT FROM AUTHOR]

Magnetically coupled resonant wireless power transfer (MCR‐WPT) system with constant power load (CPL), finds extensive applications in military, industrial, and medical treatment. However, this system can easily exhibit complex non‐linear behaviors under certain parameter conditions due to the influences of constant power loads, switching devices, and feedback controllers. These behaviors limit the effectiveness of controllers and reduce the efficiency and stability of the system. It is necessary to study the non‐linear characteristics of the MCR‐WPT system with CPL. The stroboscopic discrete mapping of the MCR‐WPT system with CPL is established. Then the system's non‐linear dynamics are analyzed theoretically using a bifurcation diagram, the maximal Floquet multipliers, and the maximal Lyapunov exponent spectrum obtained from the proposed discrete mapping. The results show that the MCR‐WPT system with CPL will exhibit rich non‐linear dynamics with the variation of the power of CPL, such as cyclic fold bifurcation, Neimark–Scaker bifurcation, border collision bifurcations, chaos, etc. The excellent alignment of experimental and theoretical outcomes in corresponding states confirms the accuracy of the proposed discrete mapping and the nonlinear analysis of the system. The results of this study can provide a reference for selecting parameters for an actual MCR‐WPT system with CPL. [ABSTRACT FROM AUTHOR]

A substantial interest in inductive power transfer (IPT) is due to its straight forwardness and dependability in charging electric vehicle (EV) batteries for researchers. The mutual inductance (MI) plays a critical role in the IPT system as it enables efficient power transfer. Therefore, it is imperative to examine the MI between the two coils that are connected through inductive coupling. This work investigates the MI and efficiency of connected coils in interoperable conditions. The transmitter coil is arranged in the shape of a square (TxS), whereas the reception coil is arranged in the shape of a circle (RxC). A concise and user‐friendly collection of design guidelines for S‐S compensated resonant inductive power transfer (SS‐RIPT) systems the design concepts efficiently mitigate the possibility of systematically and unambiguously setting the specifications for a given load profile. A 3.6‐kW setup has been constructed and validated by finite element analysis and experimental testing, following the design specifications. The availability of suitable testing equipment in the laboratory influenced the choice of a resonance frequency and output voltage for a 3.6 kW system. [ABSTRACT FROM AUTHOR]

Cross‐coupling and current sharing are the main problems faced by modular wireless power transfer (WPT) systems for electric vehicle (EV) applications. In this study, a decoupled dual‐channel wireless power transfer loosely coupled transformer (LCT) with a hybrid core composed of nanocrystalline and ferrite is proposed for modular WPT systems, as well as WPT systems with specific hybrid topology or detuned compensation. Firstly, the requirements of the LCT for modular parallel dual‐channel WPT system and detuned compensation are discussed. For these requirements, the structure and corresponding optimization design method of the decoupled dual‐channel LCT with a hybrid core is then proposed, and an LCT is designed with this method for the case study. Furthermore, the LCT is analysed by the finite element method (FEM). It is revealed that the mutual inductances of the proposed LCT between transmitting and receiving coils can be symmetrical under misalignment in multiple directions, while the cross‐coupling is eliminated. Finally, the designed LCT is manufactured and verified in a modular parallel dual‐channel WPT system. The experimental results show that the current and power sharing is realized under misalignment in multiple directions. [ABSTRACT FROM AUTHOR]

This paper introduces three different shapes of wireless charging containers (i.e. quadrangular prism, octagonal prism, and hexagonal prism) and presents optimal current flow designs for the coils to enhance the uniformity of magnetic flux distribution inside the containers. Additionally, the concept of folded coil design is introduced to further improve the even distribution of magnetic flux density within the containers. The performance of these designs is evaluated through simulations and practical experiments. [ABSTRACT FROM AUTHOR]

In the realm of wireless power transfer, considering misalignment between transmitting and receiving coils is imperative. Traditional wireless power transfer systems experience a significant decrease in output power when the coupling coefficient fluctuates. This paper proposes a reconfigurable dual‐frequency series–series (SS) topology with primary side inductive detuned and secondary side with full resonance. The proposed topology operates at two frequencies and can be transformed into two different SS topologies at each frequency. This allows the system to switch between the two SS topologies when a large misalignment occurs, thereby achieving a more stable output power level. Furthermore, a comprehensive parameter design flowchart for the proposed topology is presented, and the parameters for a 400 W prototype are designed and implemented. The prototype is tested to evaluate the performance of the topology. The frequency response analysis of the prototype validates the effectiveness of the parameter design method. The test results show that the topology can maintain output power fluctuations within 23% of the maximum power for misalignment ranging from k = 0.13 to k = 0.46. Additionally, the system maintains an efficiency of at least 80% across the entire output power flat range, peaking at a maximum efficiency of 91%. [ABSTRACT FROM AUTHOR]

The electromagnetic Halbach array (EHA) for wireless power transfer (WPT), designed to improve the transferred power and power transfer distance, has been proven to be effective and can be applied in various consumer applications. This paper presents a hybrid form of the EHA, aimed at improving the quality of power generated and transmitted. The expression for the determination of the magnetic field of a variable pitch flat coil for wireless power transfer and other uses has been derived. The average magnetic field, magnetic flux, and power transfer efficiency are investigated. The power transfer efficiency and the average magnetic field generated by four different design considerations were compared. The hybrid electromagnetic Halbach array wireless power transfer system (HEHA‐WPTS) has also been studied and results are compared with the conventional arrangements. Simulations and experiments were carried out to verify the analytical results obtained. According to the results obtained, the HEHA‐WPTS, with a base coil with variable pitches and uniform side coils, produces a more uniform average magnetic field and a better average power transfer efficiency over a longer power transfer distance. [ABSTRACT FROM AUTHOR]

Traditional soft ferrite manufacturing is limited to simple geometries and materials, while 3D printing offers greater flexibility for complex designs. Notably, soft ferrites are crucial for magnetic couplers (pads) in inductive power transfer (IPT) systems to achieve efficient wireless power transmission. The adoption of soft ferrite 3D printing in IPT systems could lead to significantly improved magnetic coupler design, yet research in this area is limited. Hence, the paper first makes a comprehensive comparison of the existing soft ferrite 3D printing methods to ascertain their suitability for magnetic couplers in IPT systems, and then proposes the binder jetting (BJT) as a potential 3D printing approach that could be appropriate for IPT magnetic coupler implementation being versatile, cost‐effective, and suitable for large‐scale manufacturing with high precision. This paper explores the suitability of BJT by 3D printing toroid cores with Mn–Zn ferrite powder under different sintering temperature profiles. Experimental results are presented to show that toroid cores can be 3D printed with high printing precision, mechanical strength, and a relative permeability of 10. This paper also highlights the impact of sintering temperature on 3D‐printed cores, the challenges, limitations, and future research directions of soft ferrite 3D printing for IPT magnetic couplers by the BJT method. [ABSTRACT FROM AUTHOR]

ABSTRACT Considering the impact of metamaterials on the magnetic coupling effect and electromagnetic response characteristics in wireless power transfer systems for implantable cardiac pacemakers, this paper proposes a wireless power transfer system operating at the 300‐kHz frequency band, enhanced by spiral ring mu‐negative materials (SR‐MNG) to improve magnetic coupling efficiency. First, based on the resonance principle, the SR‐MNG is designed, and the system's mutual inductance coupling is analyzed using the magnetic dipole coupling model theory. Second, the impact of metamaterial thickness and loss on the system's coupling strength is investigated, and the performance of the system is analyzed when using FR4, polyimide, and aluminum nitride as dielectric substrate. The system's tolerance to misalignment is discussed bearing in mind the special implantation environment of the peacemaker. The experimental results indicate that, at a transmission distance of 20 mm, the system achieves optimal magnetic coupling strength with a thickness of 1.6 mm, resulting in a minimum power transmission efficiency of 71%. Increasing the thickness to 2 mm disrupts the trend of increasing efficiency, causing it to drop by at least 23.3%. The SR‐MNG with polyimide as the dielectric plate performs exceptionally well, maintaining an efficiency range of 17.3%–73.1% for lateral displacements between 0 and 30 mm and achieving a minimum efficiency of 39.2% for angular misalignment of 15°. [ABSTRACT FROM AUTHOR]

Long‐lived room temperature phosphorescent (RTP) materials have prospective applications, but endowing long‐lived RTP materials with on‐off regulation property is challenging. Here, the first electric responsive long‐lived RTP switching device under photoexcitation with a wireless power transmission (WPT) system is demonstrated. It exhibits long persistent phosphorescence (180.1 ms for the film and 180.8 ms for the device) and excellent reversibility (>1000 cycles). Due to the effective dual‐state Förster resonance energy transfer (FRET) process from the triplet and singlet states of the chromophore donor to the singlet state of the dye acceptor, the devices exhibit switching characteristics. The appearance of the dye's absorption can be modulated by electro‐acid based on proton‐coupled electron transfer (PCET) mechanism, resulting in the device being electrically controlled. In addition, by integrating WPT coils outside the device, it can be driven wirelessly, thereby overcoming the reliance on electrical stimulation methods on the power supply. Finally, due to the multiple switching characteristics (color, fluorescence, phosphorescence) of this device, it is successfully applied in anti‐counterfeiting and information encryption. [ABSTRACT FROM AUTHOR]

Wireless energy transmission (WET) promises to enhance device mobility through selective and untethered energy delivery. In this paper, WET principles are harnessed to directly and non‐dispersively transfer thermal stimuli to designated areas within thermally‐responsive liquid crystal oligomer networks (LCONs). For this, a conductive coil receiver within the LCON as a remote stimuli source is embedded. Upon activation by radio‐frequency WET, targeted Joule heating occurs and the low thermal conductivity of LCONs causes retention of delivered stimulus at the receiver, generating temperature differences of up to 45 °C within the host LCON. This enables localized LCON actuation and self‐regulated oscillations with a natural frequency of ≈0.027 Hz. WET selectivity is further demonstrated within self‐pressing buttons for keyboards, where actuation only in designated areas is required for operation. The work is envisioned to contribute toward remote material‐based logic for hybrid circuit designs for medical, soft robotic, and haptic applications. [ABSTRACT FROM AUTHOR]

Reconfigurable intelligent surfaces (RISs) have emerged as a groundbreaking technology, revolutionizing wireless networks with enhanced spectrum and energy efficiency (EE). When integrated with drones, the combination offers ubiquitous deployment services in communication‐constrained areas. However, the limited battery life of drones hampers their performance. To address this, we introduce an innovative energy harvesting (EH), that is, EH‐RIS. EH‐RIS strategically divides passive reflection arrays across geometric space, improving EH and information transformation (IT). Employing a meticulous, exhaustive search algorithm, the resources of the drone‐RIS system are dynamically allocated across time and space to maximize harvested energy while ensuring optimal communication quality. Deep reinforcement learning (DRL) is employed to investigate drone‐RIS performance by intelligently allocating resources for EH and signal reflection. The results demonstrate the effectiveness of the DRL‐based EH‐RIS simultaneous wireless information and power transfer (SWIPT) system, demonstrating enhanced drone‐RIS spectrum‐efficient communication capabilities. Our investigation is summarized in unleashing potential, which shows how DRL and EH‐RIS work together to optimize drone‐RIS for next‐generation wireless networks. [ABSTRACT FROM AUTHOR]

ABSTRACT When the autonomous underwater vehicle (AUV) is charged by wireless charging technology (WCT), the coupler will be misalignment due to the impact of marine environment factors, which can lead to the weak stability of the system output. Besides, the electromagnetic field generated by the coaxial coil is concentrated in the center of the AUV hull, and the strong electromagnetic field may interfere with the normal operation of the power electronic equipment inside the AUVs. To address the above problems, this paper proposes a novel coupler with high anti‐offset and suppression of the central magnetic field of the AUVs. The coupler is composed of a three‐phase segmented arc‐shaped transmitter coils and a cylindrical receiver coil. The coupler can implement the suppression of the AUV central magnetic field and the promotion of anti‐rotation offset feature under the omnidirectional uniform magnetic field control method. To better adapt the proposed coupler and meet the battery charging requirements, a three‐phase wireless charging topology with a relay is designed, which can acquire the smooth transition between the two charging modes without constructing the wireless communication between two sides and detecting the state of charge (SOC). Finally, to verify the feasibility of the proposed scheme, a 1‐kW AUV wireless charging prototype is built. The experimental results indicate that the maximum output power fluctuation rate of the system is 1.1% in the case of the full‐angle rotation offset. [ABSTRACT FROM AUTHOR]

Wireless sensor networks (WSNs) play a crucial role in the Internet of Things (IoT) for ubiquitous data acquisition and tracking. However, the limited battery life of sensor nodes poses significant challenges to the long-term scalability and sustainability of these networks. Wireless power transfer technology offers a promising solution by enabling the recharging of energy-depleted nodes through a wireless portable charging device (WPCD). While this approach can extend node lifespan, it also introduces the challenge of bottleneck nodes—nodes whose remaining energy falls below a critical value of the threshold. The paper addresses this issue by formulating an optimization problem that aims to identify the optimal traveling path for the WPCD based on ant colony optimization (WPCD-ACO), with a focus on minimizing energy consumption and enhancing network stability. To achieve it, we propose an objective function by incorporating a time-varying z phase that is managed through linear programming to efficiently address the bottleneck nodes. Additionally, a gateway node continually updates the remaining energy levels of all nodes and relays this information to the IoT cloud. Our findings indicate that the outage-optimal distance achieved by WPCD-ACO is 6092 m, compared to 7225 m for the shortest path and 6142 m for Dijkstra's algorithm. Furthermore, the WPCD-ACO minimizes energy consumption to 1.543 KJ, significantly outperforming other methods: single-hop at 4.8643 KJ, GR-Protocol at 3.165 KJ, grid clustering at 2.4839 KJ, and C-SARSA at 2.5869 KJ, respectively. Monte Carlo simulations validate that WPCD-ACO is outshining the existing methods in terms of the network lifetime, stability, survival rate of sensor nodes, and energy consumption. [ABSTRACT FROM AUTHOR]

Dynamic wireless power transfer (DWPT) systems with segmented transmitters suffer from output pulsations during the moving process. Although numerous coil structures have been developed to mitigate this fluctuation, the parameter design process is complicated and restricted by specific working conditions (e.g., air gaps). To solve these problems, a novel reverse-bent modular transmitter structure is proposed for DWPT in industrial automatic application scenarios such as linear transport systems. Considering the heterogeneous current density distribution in the adjacent region between two coils which causes a drop in magnetic field, the proposed coil structure attempts to eliminate the effects of the adjacent region by bending the terminal parts of each coil reversely to the ferrite layer for shielding. Compared to traditional planar couplers, this structure array can generate a uniform magnetic field over various air gaps. A 100 W laboratory prototype was built to verify the feasibility of the proposed system. The experimental results show that the proposed system achieved a constant output voltage, and the output pulsation was within ±2.3% in the dynamic powering process. The average efficiency was about 88.29%, with a 200 mm transfer distance. When the air gap varied from 20 mm to 30 mm, the system could still retain constant voltage output characteristics. [ABSTRACT FROM AUTHOR]

ABSTRACT Massive multiple‐input multiple‐output (MIMO) technology with a base station (BS) equipped with a large number of transmit antennas is a promising application for wireless information and power transfer (WIPT) in energy‐constrained wireless networks. Recently, a transmit time switching (TS) protocol, where the information and energy are transferred over a different fractions of a time‐slot, has received much attention to enable WIPT. The optimal beamforming design and time‐fraction allocation for information and energy transfer are important to maximize the worst‐case throughput while fulfilling the energy harvesting requirement. However, the existing solution in literature is computationally demanding due to its dependence on off‐the‐shelf solvers such as CVX. In this work, a deep learning model is sought to predict the optimum resource allocation parameters in WIPT‐based massive MIMO systems. The model is composed of three fully connected networks, each of which is trained to predict certain optimization variables. The proposed network enables the system to quickly update the required optimization parameters as the network condition changes without revisiting the original optimization problem. Moreover, it is found that user distances are sufficient input features to train the networks, as training using channel state information (CSI) of the users renders the proposed solution time‐inefficient, as a channel estimation technique is required. It is also found that training using distances yields more accurate results than training using CSI, which suggests that the deep neural network (DNN) extracts higher quality features from spatial information than the features extracted given the corresponding CSI. [ABSTRACT FROM AUTHOR]

This study examines a cooperative non-orthogonal multiple access (NOMA) network utilizing an energy-constrained unmanned aerial vehicle (UAV) relay (UAVR) to expand coverage and improve network throughput. In order to provide energy to the UAVR, we consider the hybrid simultaneous wireless information and power transmission (SWIPT) method, which allows the UAVR to harvest energy from the source (i.e., sink node) signal. Herein, a hybrid time switching (TS)-based and power splitting (PS)-based relaying scheme is applied to improve the UAVR's energy harvesting (EH) efficiency and the system performance. Given this context, we derive the closed-form expression of the outage probability (OP) for the sensors to evaluate the network performance. Based on the achieved analytical results, we apply the bat algorithm optimization (BAO) method to determine the optimal working point (as a fraction of received power and power allocation coefficients, and the 3-D positions of the UAVR) for the system such that the OP is minimized. The numerical analysis indicates that BAO is effective in both exploring and exploiting solutions, making it a suitable choice for similar non-convex optimization problems in continuous search spaces for cooperative NOMA IoT networks. [ABSTRACT FROM AUTHOR]

Devices that are employed in applications related to the Internet of Things (IoT) are constrained by limited energy resources. Consequently, ensuring a continuous supply of energy while also maintaining uninterrupted connectivity within IoT units (IoTUs) is of great importance. In this particular context, we present a scheme that facilitates both, the transfer of wireless power and the transmission of information for IoTUs along with the capability of harvesting solar energy. This scheme is further supported by the utilization of unmanned aerial vehicles (UAV) and the deployment of reconfigurable intelligent surfaces (RIS) for communication purposes. To be more precise, initially, IoTUs obtain energy from the UAV through the process of wireless power transmission (WPT). Subsequently, in the second stage, the UAV retrieves data from the IoTUs using transmitting information. In order to simplify the complexity of the communication issue, we assume that a solar-powered UAV remains stationary at a predetermined altitude. Our objective is to maximize the energy efficiency (EE) of the entire network by coordinating the scheduling of IoTU energy harvesting (EH) and UAV trajectory optimization. We suggest a multi-agent federated reinforcement learning (MFRL) algorithm that maximizes EE through parameter optimization in order to achieve this goal. By utilizing the collective experiences of several agents and reducing energy usage, this algorithm also improves the overall performance of the system. The proposed technique achieves 96.3% and 97.5% accuracy in communication rounds and RIS elements, with a 9 − 33 % increase in EE compared to the best-performing benchmark scheme. The suggested approach outperforms the benchmark algorithms in terms of EE, trajectory optimization, and learning accuracy, according to simulation findings. [ABSTRACT FROM AUTHOR]

Multi-load wireless power transfer systems generally require the configuration of multiple transmitting coils. Using traditional single-output inverters will increase the number of inverters, leading to increased system costs and complex structures. Therefore, this paper proposes a single-input multi-output inverter that can drive multiple transmitting coils simultaneously. Compared with traditional single-output inverters and existing multi-output inverters, the proposed inverter utilizes a topology improvement design and an efficient expansion method. By adding only one inductor, one capacitor, and a small number of power switches, it can generate multiple controllable and stable outputs while ensuring output gain, which is expected to simplify the system structure and improve system performance. This paper first introduces the topology evolution process and operating principle of the proposed inverter. Secondly, a mathematical model is established to analyze its operating characteristics, and its parameter design is carried out. Meanwhile, a comparison with existing multi-output inverters is conducted. Then, the resonant compensation networks are analyzed and selected to match the requirements of different loads. Finally, a simulation model of the proposed inverter is constructed, and an experimental setup is set up. The feasibility and superiority of the proposed inverter are verified through simulation and experiments. [ABSTRACT FROM AUTHOR]

Electrical stimulation is effective for various therapeutic applications; however, to increase convenience, it is crucial to eliminate generators and batteries for wireless power transmission. This paper presents a full textile-based body-coupled electrical stimulation (BCES) system designed for wireless electrical stimulation using energy loss from electronic devices and static electricity from physical activity. We developed the BCES socks by knitting conductive threads to ensure stability and comfort. BCES socks generate electric fields ranging from tens to hundreds of millivolts per millimeter, which are sufficient to activate muscle fibers. Experimental and computational analyses confirmed the effective concentration of the electric fields. Human trials demonstrated significant improvements in exercise performance, with a 21.47% increase in calf raise frequency, an 11.97% increase in repetition count, and a 6.25% reduction in muscle fatigue. These results indicate the potential of BCES socks as a practical battery-free solution for enhancing muscle activity and reducing fatigue. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper proposed a segment‐compensated printed circuit board (PCB) coil for multirelay wireless power transfer (WPT) system. The PCB coil is designed with variable width to improve the system transfer efficiency, and the segmented compensation method is applied to avoid the high voltage stress on resonant capacitors in case of the multirelay WPT system with a low load resistance operating at a constant voltage frequency. The segmented compensation capacitors are integrated into the PCB coil, so as to constitute the compact coupler used in multirelay WPT system. The optimization procedure of the segment‐compensated PCB coil is also provided. The quality factor of the PCB coil can be improved by optimizing the proportional coefficients of width variation. The voltage of capacitors can be reduced by optimizing the number of segments. A physical variable‐width PCB coil with 3 segments is constructed. The experimental prototypes of the three‐coil, four‐coil, and five‐coil WPT systems are built. The experimental results show that the voltage of the segmented compensation capacitors on each coil is almost uniformly distributed and does not exceed 250 V when the input voltage is 50 V and the load resistance is 10 Ω. Compared with the multirelay WPT system using the equal‐width PCB coil, the multirelay WPT system using the PCB coil designed in this paper has higher output power and higher efficiency. [ABSTRACT FROM AUTHOR]

A wearable microgrid that centralizes and distributes harvested energy across different body regions can optimize power utilization and reduce overall battery weight. This setup underscores the importance of developing cable-free wireless power transfer (WPT) systems for mobile and portable devices to eliminate the risks posed by wired connections, especially in dynamic and hazardous environments. We introduce a thin, stretchable, and safe hand band capable of watt-level wireless charging through the widely adopted Qi protocol operating at 130 kHz. The implementation of non-adhesive fabric encapsulation serves to protect the 50-μm-thin spiral copper antenna from mechanical strain, ensuring an overall hand band stretchability of 50%. We also create a stretchable "Ferrofabric", characterized by a magnetic permeability of 11.3 and a tensile modulus of 75.3 kPa, that provides magnetic shielding for the antenna without compromising wearability. The "Ferrofabric" improves the coil inductance but induces core loss in AC application. By fully understanding and managing loss mechanisms such as the skin effect, proximity effect, core loss, and joule heating, we achieve a wireless charging efficiency of 71% and power delivery of 3.81 W in the kHz frequency range. Our WPT hand band is unobstructive to hand motion and can charge a handheld smartphone as fast as a desktop charger or power a battery-free chest-laminated e-tattoo sensor, with well-managed thermal and electromagnetic safety. Through a holistic electromagnetic, structural, and thermal design, our device culminates in a safe, rugged, and versatile solution for wearable WPT systems. [ABSTRACT FROM AUTHOR]

Due to its limited load capacity, the piggybacking of wireless charging systems for micro unmanned aerial vehicles has become a challenging task in the design of micro unmanned aerial vehicles. Therefore, this paper proposes an improved lightweight design method for micro unmanned aerial vehicles to carry a wireless charging system. The improved system uses an inductor–capacitor–capacitor‐parallel (LCC‐P) topology compensation network instead of a bilateral inductor–capacitor–capacitor (LCC) topology compensation network to achieve constant current charging (CC) and constant voltage charging (CV). Then the adaptive frequency conversion control is used to realize the automatic conversion from CC charging to CV charging during the charging process. Compared with the traditional wireless charging system based on a direct current‐direct current converter (DC‐DC converter) to achieve CC charging and CV charging, this improved system reduces the total weight of the receiving end of the wireless charging system based on ensuring the charging efficiency, which meets the demand of wireless charging systems carried by micro drone aircraft. The test results of the constructed physical system coincide with the simulation design results, and the total weight of the receiving end is only 8 g, which verifies the correctness and effectiveness of the improved design scheme. [ABSTRACT FROM AUTHOR]

This paper presents an innovative adaptive strategy implemented in wireless power transmission (WPT) systems to overcome efficiency challenges due to coupling structure misalignment and load variability. A novel versatile transmitter, capable of alternating between single and dual voltage source states via two MOSFETs has been designed. Initially, the system operates in a single voltage source mode, mutual inductance and load characteristics are pinpointed using a particle swarm optimization algorithm. Subsequently, the system transitions to dual voltage source mode, where it fine‐tunes the auxiliary voltage source's amplitude and phase based on the determined mutual inductance and load values to realize zero phase angle for optimal impedance matching. The experimental results show that this method can obviously improve the output power of WPT system. This method stands out for its simplicity, adaptability and rapid response, suggesting its potential for practical use in dynamic charging applications. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) systems have been widely adopted for full autonomy in various fields due to their convenience. However, changes in the air gap between the Tx and Rx coils significantly affect efficiency. To overcome this challenge, this paper introduces the determination of a compensation capacitor for a distance-variable WPT system that is robust in varying air gap conditions. The proposed method was verified using theoretical analysis, simulation, and experimental measurement. The electrical circuit was modeled using a T-equivalent model in a series–series (SS) topology to calculate power transfer efficiency (PTE). Specifically, compensation capacitors were analyzed at distances of 10, 30, and 50 mm, considering different self-inductance values. These results are compared against varying load resistances to demonstrate the effectiveness of the proposed approach. Additionally, the PTE drop ratio was defined to facilitate comparison. The results show that the PTE drop ratio for the compensation capacitor at the farthest distance was consistently smaller than that for the capacitor at the nearest distance under varying air gaps and load resistances. In this research, the difference in the PTE drop ratio between 10 and 50 mm was measured, demonstrating that determining the capacitor at the farthest distance reduces the PTE drop ratio across a range of operational conditions. [ABSTRACT FROM AUTHOR]

InGaN, a group‐III nitride semiconductor, is expected to be widely used in the field of optoelectronics, owing to its excellent physical properties. However, InGaN has various limitations. This study reports face‐to‐face annealing (FFA) using vapor‐phase and in‐plane mass transport to improve the surface flatness of an InGaN template. InGaN layers are grown on a GaN template that is grown on a c‐plane sapphire substrate using metal–organic vapor‐phase epitaxy. NH3‐assisted FFA is performed at 1050 °C for 20 min, causing V‐pits to vanish from the InGaN template despite their initial density of 3.3 × 108 cm−2. The surface condition of the lower InGaN layer is worse than that of the upper InGaN layer due to the FFA‐induced upward mass transport from the lower layer, thereby eliminating the V‐pits. Compositional analysis of the upper layer through Auger electron spectroscopy and energy‐dispersive X‐ray spectroscopy reveals In peaks despite high‐temperature annealing, thus confirming the presence of InGaN. The results of this study offer possibilities for future InGaN crystal growth and InGaN‐based device fabrication. [ABSTRACT FROM AUTHOR]

The proliferation of smart devices increases the demand for energy-efficient, battery-free technologies essential for sustaining IoT devices in Industry 4.0 and 5G networks, which require zero maintenance and sustainable operation. Integrating radio frequency (RF) energy harvesting with IoT and 5G technologies enables real-time data acquisition, reduces maintenance costs, and enhances productivity, supporting a carbon-free future. This survey reviews the challenges and advancements in RF energy harvesting, focusing on far-field wireless power transfer and powering low-energy devices. It examines miniaturization, circular polarization, fabrication challenges, and efficiency using the metamaterial-inspired antenna, concentrating on improving diode nonlinearity design. This study analyzes key components such as rectifiers, impedance matching networks, and antennas, and evaluates their applications in biomedical and IoT devices. The review concludes with future directions to increase bandwidth, improve power conversion efficiency, and optimize RF energy harvesting system designs. [ABSTRACT FROM AUTHOR]