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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]

A rapid and reliable quench detection is vital for high current superconducting magnet system to prevent irreversible damage to a magnet by the quench phenomenon. The method for detecting the occurrence of a resistive transition has been widely adopted in the superconducting magnet. In the case of the voltage monitoring by means of dedicated taps, the electron quench detection device (EQDD) conversion unit, which converts detected high voltages into voltage-drop signal, should be required in the superconducting high field magnet. The power source of traditional quench detecting system, which can monitor for superconducting magnet with middle power operation, is supplied through the power transformer since the transformer can provide galvanic isolation between circuits. On the other hand, in the case of the super high magnet systems such as Korea Superconducting Tokamak Advanced Research and International Thermonuclear experimental reactor, since the maximum operation current and voltage of the super high field magnet keep over 60 kA and 50 kV DC, a passive component, which has strong an isolation device and high dielectric resistor qualities, has been required in the super high field magnet. If the power transformer is adopted in the super high field magnet, it can cause high cost for volume capacity since it needs for higher dielectric resistance value over 500 MΩ. Authors proposed the wireless resonance antenna and multi-receiver coils which can keep high level of dielectric resistance value with stability. As well as, the wireless power charging unit can reduce system volume due to multi-charging receivers for one antenna. In this study, authors investigated the effect of inserted resonator (Sx) coil between antenna and receiver coils, as well as, evaluated the electric field and magnetic field among the resonance coils under 300 W 370 kHz RF power generator since the strong electro-magnetic fields by the resonance coils can affect the electron devices inside of the EQDD module. [ABSTRACT FROM AUTHOR]

The innovations of battery and charging technologies facilitate worldwide bus electrification, which can conserve energy and reduce emissions. The emergence of wireless power transfer technology offers the potential to alleviate bus range anxiety. This paper constructs the layout models of static wireless and centralized charging stations based on the seasonal differences associated with battery capacities and passenger flow, which aims to obtain the bus charging station layout scheme of the lowest cost. Then, the heuristic algorithm is utilized to solve the layout models as the mixed linear programming problem. This study results confirm that the combined layout of static wireless and centralized charging stations is more advantageous than a single model. Finally, the required fixed cost of supporting bus system operation is explored for future capital reserves. [ABSTRACT FROM AUTHOR]

Summary: In wireless power transfer (WPT) systems, extended transmission distances significantly impede efficiency, posing a major challenge to their practical application. This paper presents a novel ortho‐octagonal double‐helix metamaterial that can effectively enhance the transmission efficiency of WPT systems. It has theoretically derived and experimentally verified the enhancement of evanescent wave transmission by this metamaterial dielectric plate. A WPT simulation system operating at 10.78 MHz is constructed by HFSS software, and the effects of adding passive relay coils and different shapes of metamaterials on the transmission efficiency are comparatively investigated. Simulated data converge to indicate that integrating variously shaped metamaterials at the transceiver's end distinctly elevates the WPT system's transmission efficiency. When the transceiver coil spacing of the WPT system is greater than 22 cm, the effect of metamaterials on the system transmission efficiency enhancement shows an increasing and then decreasing trend as the distance increases. The positive octagonal metamaterial improves 12% over the circular metamaterial in the mid‐range transmission distance due to its better magnetic coupling effect. When the transceiver coil spacing is 22 cm, the open‐circuit voltage of the receiving coil after loading the metamaterial is stabilized to be enhanced by nearly five times, and it has the best effect at 30 cm, and the transmission efficiency is enhanced from 30% to 60%, which verifies the effective enhancement of the metamaterial on the transmission efficiency of the WPT system. [ABSTRACT FROM AUTHOR]

Summary: Omnidirectional Wireless Power Transfer (OWPT) system can provide power to multiple loads in space. The different loads have different requirements for current and power levels under various operating conditions. This paper proposes a Variable Receiving Coil (VRC) structure and its control strategy. Active regulation of the output current is achieved by adjusting the geometric size of the receiving coil. Meets the power supply needs of equipment in different scenarios. This design allows the effective value of the VRC current to remain stable within the range of 1.01–1.62A (transmission distance of 22–27 cm). By adjusting the geometric transformation state of the VRC, different output currents can be obtained under fixed positions, loads, and input voltages. The designed receiver can meet the differential current requirements of multiple spatial loads, and is insensitive to factors such as load, transmission distance, and rotation angle. This system can reduce the design complexity of charging and power supply systems and effectively promote the application of Wireless Power Transfer (WPT) in the field of Internet of Things devices. [ABSTRACT FROM AUTHOR]

A cooperative network could improve energy efficiency by combining non-orthogonal multiple access (NOMA) with simultaneous wireless information and power transfer (SWIPT). This work proposes a novel model for optimal resource allocation for specified users through combined time switching and power splitting protocol. The system uses an amplified and forward-based energy harvesting protocol to broadcast the data in the Nakagami-m fading channel. An algorithm that provides the power coefficients for all NOMA users as a Levy Aquila optimiser is exploited to maximise the signal-to-noise ratio for far and near users. Further, the parameters of combined time switching and power splitting are brought by a game theoretic approach, which supports better energy harvesting in relay nodes with improved energy efficiency and high outage probability. The simulated results show that the employed scheme's energy efficiency has increased by 11.3%, improved from the GS-Dinkelbach algorithm. [ABSTRACT FROM AUTHOR]

In this study, we employed a high‐frequency‐driven thin‐film magnetic sensor to precisely measure the magnetic near field with enhanced spatial resolution, a challenge often faced by conventional loop antennas. Our study introduced an innovative approach utilizing this magnetic sensor to assess the magnetic near field in wireless power transfer systems, comparing its performance against that of a loop antenna. Our findings demonstrate that the magnetic sensor achieves its peak signal‐to‐noise ratio at a DC bias field of 4.7 Oe and carrier frequency of 0.5 GHz, boasting a detection limit for magnetic fields of ~0.4 A/m. Moreover, the magnetic field trend measured by the magnetic sensor closely aligns with simulation results, exhibiting sharper changes around the center compared to the loop antenna. These results highlight the superior sensitivity and spatial resolution of the magnetic sensor over conventional loop antennas. By enhancing the reliability of electronic systems across diverse applications, these sensors pave the way for advanced EMI/EMC evaluation techniques. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Recently, unmanned aerial vehicle (UAV)-enabled wireless power transfer (WPT) has received great attention as a promising technology for providing stable power to energy-constrained devices by navigating three-dimensional (3D) space, particularly in challenging environments such as maritime networks and smart cities. Additionally, UAV-enabled radar sensing has gained significant attention as a key technology for future 6G networks, as it enables high-accuracy sensing for various applications, such as target detection and tracking, surveillance, and environmental monitoring, as well as autonomous UAV operation. In this regard, we investigated UAV-enabled integrated sensing and wireless power transfer (ISWPT) systems that combine radar sensing and WPT operations on a unified hardware platform, sharing the same spectrum of resources. In order to accurately sense multiple targets and efficiently transfer power to multiple devices at the same time, we propose a method for jointly designing the transmit waveform and UAV altitude, taking into account the fundamental trade-off between radar sensing performance with the desired beam pattern and WPT performance with the desired harvested power of the devices. We first developed an effective method to obtain the optimal waveform and altitude by solving a challenging non-convex optimization problem. Based on this, we developed another efficient, low-complexity method by exploring a novel transmit waveform and optimizing its parameters to reduce computational complexity and thereby lower power consumption in UAVs. The numerical results verify that the proposed method significantly improves both radar sensing and WPT performance, as well as substantially reduces computational complexity. [ABSTRACT FROM AUTHOR]

In this paper, we study a multi-hop amplify-and-forward (AF) simultaneous wireless information and power transmission (SWIPT) relay system. Each relay node harvests power using a power split (PS) method from a portion of the received signal, amplifies the remaining received signal, and passes it to the next relay. Based on this system model and signal flow, we derived and solved the convex power minimization problem with the optimal PS ratio. In this case, it was found that using the optimal PS ratio consumed a lower amount of power than when using a fixed PS ratio (0.5). We then investigated the impact of processing cost on the AF-SWIPT system using decoding and forwarding SWIPT as benchmarks, and found that AF-SWIPT was superior. [ABSTRACT FROM AUTHOR]

This study proposes a novel approach for selecting the resonance capacitance of wireless power transfer systems, aiming to achieve a zero phase angle (ZPA) while simultaneously minimizing the leakage magnetic field. The performance of the method is validated across two key topologies: series–series (S–S or SS) and the double-sided inductor–capacitor–capacitor (LCC, LCC–LCC) topologies. By minimizing the vector phasor sum of the coil currents, the proposed approach effectively mitigates magnetic field leakage. The method is further validated through mathematical derivations, simulations, and experimental tests. The results reveal that using the proposed method to select resonance capacitances reduces the leakage magnetic field by up to 35.2% in the SS topology and by 42.0% in the double-sided LCC topology. Furthermore, the method improves the ZPA by more than 20° in both cases. These outcomes affirm the effectiveness of the proposed resonance tuning approach. [ABSTRACT FROM AUTHOR]

With the increasing popularity of the internet of things (IoT) and 5th generation mobile communication technology (5G), mobile edge computing (MEC) has emerged as an innovative approach to support smart devices (SDs) in performing computational tasks. Nevertheless, the process of offloading can be energy-intensive. Traditional battery-powered SDs often encounter the challenge of battery depletion when offloading tasks. However, with the advancements in wireless power transfer technology, SDs can now achieve a sustainable power supply by harvesting ambient radio frequency energy. This paper studies the computation offloading in wireless-powered MEC networks with device-to-device (D2D) assistance. The SDs are categorized into near and far SDs based on their proximity to the MEC server. With the support of near SDs, far SDs can reduce transmission energy consumption and overall latency. In this paper, we comprehensively consider the allocation of energy harvesting time, transmission power, computation resources, and offloading decisions for SDs, establishing a mathematical model aimed at minimizing long-term average delay under energy constraints. To address the time-varying stochastic nature resulting from dynamic task arrivals and varying battery levels, we transform the long-term problem into a deterministic one for each time slot by introducing a queue and leveraging Lyapunov optimization theory. We then solve the transformed problem using deep reinforcement learning. Simulation results demonstrate that the proposed algorithm performs effectively in reducing delay and enhancing task completion rates. [ABSTRACT FROM AUTHOR]

Introduction. The system of delivering electricity without wires is known as wireless power transfer (WPT). The WPT system has been extensively used in a number of industries, health, telecommunications, and transportation. However, the distance between the transmitter and receiver coils has a significant impact on its efficiency. Lower power can be generated between coils the farther apart they are, and vice versa. The novelty of the proposed work is innovative in that it develops a multi-magnetic circular planar spiral relay to improve the WPT system’s performance and designs circular planar spiral coils to achieve an appropriate inductance value for the 5 kHz matching frequency. The goal of paper is to create a circular planar spiral coil with an appropriate inductance value for the 5 kHz matching frequency. Methods. The transmitter circuit, receiver circuit, and DC voltage source are parts of the WPT system. The inverter circuit uses the inductive coupling technique to transform the DC power source into AC voltage on the transmitter coil. The suggested coil is additionally employed as a multimagnetic circular planar spiral relay in order to increase the mutual inductance between the receiver and transmitter coils. Results. To monitor the power improvement that results from adding a multi-magnetic relay to the system, the transmitter coil, receiver coil, and multimagnetic relay are positioned at specific distances from each other. With Vdc = 30 V and dtr = 21 cm, the power received at the receiver coil can therefore be improved by up to 67 %. Practical value. The multi-magnetic circular planar spiral relay applied in the WPT system has been investigated in an experimental study and it can be applied for DC load. [ABSTRACT FROM AUTHOR]

In this paper, a high-efficiency compact power amplifier is designed and fabricated with a 0.25 μm GaN high electron mobility transistor (HEMT) to meet the demands of a high integration level and high efficiency for microwave wireless power transfer (WPT) systems. The proposed power amplifier (PA) is implemented using an internally matched method to achieve a compact circuit size. The output second and third harmonic impedances can be optimized through output matching circuits, eliminating the need for additional harmonic matching networks. This approach simplifies the design of matching circuits and reduces the circuit size. Furthermore, the input third harmonic has been controled for improving the efficiency of DC-to-RF conversion. The total size of the proposed PA is 13.4   ×   13.5 mm2. The test results obtained from the continuous wave (CW) testing indicate that the output power of the power amplifier at 2.45 GHz reaches 43.75 dBm. Additionally, the large-signal gain is measured at 15.75 dB, and the power-added efficiency (PAE) achieves a value of 78.5%. [ABSTRACT FROM AUTHOR]

The present study analyzes the microstrip antenna design for wireless power transfer in smart buildings, harnessing the ambient electromagnetic radiation due to common electronic gadgets that energize wireless sensor networks, computing devices, and connected appliances. With the increased number of these devices, so does the potential for health problems caused by electromagnetic radiation. However, these devices also provide a renewable energy source through their emissions. This study suggests the creation of a 5G Microstrip antenna that enhances the absorption of this radiation for the purpose of recharging batteries in smart buildings. The design capitalizes on the inherent low-profile and cost-effective features of microstrip antennas, making them well-suited for incorporation into building infrastructure and 5G wireless technologies. Although each individual device emits a little amount of energy, the combined effect achieved by advanced antenna design and power converters is anticipated to result in a substantial energy production. The antenna designer tool from MATLAB was used to carry out a conceptual simulation of the microstrip antenna. This has set up the framework of a feasible way of predicting the performance with high efficiency and sustainability for a wireless power transfer (WPT) system. [ABSTRACT FROM AUTHOR]

The paper focuses on three-dimensional (3D) spatial wireless power transfer (WPT) and the challenges of improving the isolation between coils in a multiple-coil system. We analyze the mutual inductance between coils to derive an isolation method and propose a 3D overlapping multiple-coil system with high isolation for spatial WPT systems. Through performance verification, the proposed coils are verified to achieve approximately -20.1 dB isolation and an average power transfer efficiency of approximately 61.5%, even in the presence of angular or lateral misalignments of the receiving coil. This represents an improvement of approximately 41.7% over conventional multiple-coil systems. Therefore, it can be considered a viable solution to address the limitations of degraded power transfer efficiency in WPT systems designed for spatial freedom. [ABSTRACT FROM AUTHOR]

This paper proposes compensation circuit values for minimizing the leakage magnetic field in wireless power transfer (WPT) systems with a double-sided LCC topology by identifying the resonant condition in which the vector sum of the coil currents of a WPT system is minimized. The proposed method for calculating compensation circuit values is obtained through mathematical derivation using arithmetic-geometric mean inequality and verified through simulation and experimentation. The experimental results obtained using the compensation circuit values determined by the proposed method confirm a reduction in the leakage magnetic field of the WPT system with a double-sided LCC topology by at least 8% and up to 43% compared to the system that does not use the proposed method. [ABSTRACT FROM AUTHOR]

This paper introduces a high-precision alignment method for laser wireless power transmission (LWPT) systems, integrating neural network-based target detection with a perturbation-observation technique. The objective is to enhance the alignment accuracy between the laser spot and the photovoltaic array, thereby improving energy transfer efficiency. The method's key feature is its ability to achieve these results without requiring additional optical components, simplifying system design. Continual assessment and adjustment based on real-time output power data ensure optimal alignment, maximizing the photovoltaic array power output. Experimental results demonstrated that the proposed method achieved an initial alignment precision with pixel errors below 3%, translating to a physical error of approximately 7 mm. Fine-tuning through the perturbation-observation method further optimized the alignment, resulting in a photovoltaic array power output of 98.70% of its maximum potential. This hybrid approach provides a reliable solution for boosting the performance of LWPT systems, offering significant potential for practical applications. [ABSTRACT FROM AUTHOR]

Capacitive power transfer (CPT) has emerged as a promising alternative to traditional inductive methods. CPT offers advantages like cost‐effectiveness, reduced weight and volume, and greater tolerance to alignment errors. However, the high‐Q resonant circuits used as matching networks can be susceptible to high voltage stress, especially when transmitting substantial power. Consequently, designing matching networks for CPT systems necessitates consideration of multiple parameters, including practical constraints such as component losses and breakdown thresholds. In this work an innovative algorithm is presented for designing practical matching networks in CPT systems. The algorithm conducts a methodical search of potential solutions, and converges on component values that maximize power transfer efficiency whilst also minimizing component voltage stress. The proposed algorithm is demonstrated theoretically and experimentally. [ABSTRACT FROM AUTHOR]

Enhancing the efficiency is an essential target of the wireless power transfer (WPT) technology. Enabling the WPT systems requires careful control to prevent power from being transferred to unintended areas. This is essential in improving the efficiency and minimizing the flux leakage that might otherwise occur. Selective field localization can effectively reduce the flux leakage from the WPT systems. In this work, we propose a method using a digital honeycomb metamaterial structure that has a property operation as a function of switching between 0 and 1 states. These cavities were created by strongly confining the field by using a hybridization bandgap that arose from wave interaction with a two-dimensional array of local resonators on the metasurface. A WPT efficiency of 64% at 13.56 MHz was achieved by using the metamaterial and improved to 60% compared to the system without the metamaterial with an area ratio of Rx:Tx~1:28. Rx is the receiver coil, and Tx is the transmitter one. [ABSTRACT FROM AUTHOR]

The paper investigates the effect of controlling the transmission power used for communication of data packets at physical layer to prolong longevity of network and adaptive learning rates in a reinforcement-learning algorithm working at network layer for dynamic and quick decision making. A routing protocol is proposed for data communication, which works in tandem with physical layer, to improve performance of Wireless Sensor Networks used in IoT applications. The proposed methodology employs Q-learning, a form of reinforcement learning algorithm at network layer. Here, an agent at each sensor node employs the Q-learning algorithm to decide on an agent which is to be used as packet forwarder and also helps in mitigating energy-hole problem. On the other hand, the transmission power control method saves agents' battery energy by determining the appropriate power level to be used for packet transmission, and also achieving reduction in overhearing among neighboring agents. An agent derives its learning rate from its environment comprising of its neighboring agents. Each agents determines its own learning rate by using the hop distance to sink, and the residual energy (RE) of neighboring agents. The proposed method uses a higher learning rate at first, which is gradually decreased with the reduction in energy levels of agents over time. The proposed protocol is simulated to work in high-traffic scenarios with multiple source-sink pairs, which is a common feature of IoT applications in the monitoring and surveillance domain. Based on the NS3 simulation results, the proposed strategy significantly improved network performance in comparison with other routing protocols using Q-learning. [ABSTRACT FROM AUTHOR]

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ABSTRACT Recently, numerous bidirectional wireless power transfer (WPT) systems with enhanced features for electric vehicle (EV) battery charging have been proposed. The converters in these WPT systems are generally configured with two synchronized full‐bridge–controlled converters operating at fixed duty cycle (two‐level operation) to enable WPT between the transmitter and receiver magnetic charge couplers. However, these require additional circuits to be employed in a wide range of load conditions, which lead to high costs and reduced power density. As a substitute, this article introduces a new wireless EV charging system using bidirectional dual T‐type converter (BDTC) configuration with PWM control. A wide range of load variations can be obtained without any additional circuits/switches with a proposed charging system based on a BDTC. Due to the reduced switching loss, reduced reactive circulating current, low cost, and increased efficiency, along with simple control, the proposed architecture offers significant advantages over traditional WPT systems. The proposed wireless EV charging system operates with series resonance in both directions. A mathematical model of the BDTC converter is developed, and the operating principle is detailed. Experimental results were acquired from the 3.3‐kW laboratory model, which exhibits nearly flat efficiency characteristics under various loading conditions; hence, the feasibility of the BDTC topology is validated. [ABSTRACT FROM AUTHOR]

ABSTRACT In order to reduce the damage and interference caused by electromagnetic leakage to human beings and equipment during wireless energy transmission, this paper proposes a resonant hybrid array composite shielding structure based on an LCC‐S compensation circuit at an operating frequency of 200 kHz. First, by analyzing the effects of the number of turns and turn spacing on the coil coupling coefficient, the optimal parameters of the circular main coil were determined and analysis of the effect of different inductance ratios on the transmission efficiency of the system using MATLAB. Second, the system transmission efficiency and magnetic field distribution of the system with an intermediate resonant coil and three different types of array coils are simulated, and the optimal location of the hybrid array is determined; nanocrystals are selected as the shielding material and integrated reactive and passive shielding methods to improve system transmission performance and reduce electromagnetic leakage. Finally, an experimental platform was set up to verify the system's transmission performance. The results showed that when the hybrid array was placed in the center of the transmission coil, the magnetic flux density decreased by 40.1% at 58 mm from the measurement center. At a transmission distance of 16 mm, the transmission efficiency reached 60.2%, which was 9.4% higher than the situation without shielding. [ABSTRACT FROM AUTHOR]

In this study, we introduce a two-dimensional metasurface sensor designed to detect, locate and distinguish between different objects placed in its near field. When an object is placed on the metasurface, local changes can be detected in one or more of the structure's meta-atoms. This interaction generally modifies the inductance of the meta-atom, resulting in changes to the overall input impedance of the surface. We derive the properties of the structure and its behaviour in terms of superposition and demonstrate that observing the meta-surface from a single point is sufficient for unambiguous localisation and identification. To model these changes effectively and identify the position of an object, we employ a neural network machine learning algorithm. Our approach enables accurate localisation of all studied objects, with a precision exceeding 98 % . Additionally, the distinct signatures of the objects allow for separation between them with an accuracy of over 97 % . The potential applications of this platform extend to foreign object detection on metasurfaces for wireless power transfer, providing proximity detection for many surfaces such as clothing, car bodies and robotic carapaces. Furthermore, our research suggests the feasibility of implementing a touchscreen type interface requiring only a single waveguide connection. [ABSTRACT FROM AUTHOR]

Non‐diffraction Airy beams with self‐accelerating properties have many potential applications in the microwave band, such as providing a viable solution to bypass obstacles for microwave‐based wireless power transfer (WPT) and communication. However, most of the recent work on Airy beams exhibits singular functionality and operates solely in linear polarization, with complex generation setups, which will constrain the applications of the beam in the microwave band. In this paper, based on the anisotropic holographic impedance metasurface (AHIM) with low complexity, a new method is proposed to manipulate Airy beams in multiple dimensions, including circularly polarization state, number of beams, direction of acceleration, and launch position of beam. The underlying principle is the combination of plane coordinate transformation, anisotropy of AHIM, and impedance superposition theory. Further, to validate the proposed method, an AHIM prototype for simultaneously generating two Airy beams with orthogonal circular polarization, different directions of acceleration, and different spatial distribution is designed, simulated, and measured. The proposed method based on AHIM for manipulating the Airy beams multidimensionally in the microwave band offers an efficient strategy to control the energy coverage and polarization state of the beam in different WPT scenarios. [ABSTRACT FROM AUTHOR]

The growing adoption of electric vehicles (EVs) and advancements in dynamic wireless charging (DWC) technology have strengthened the interdependence between power distribution networks (PDNs) and electrified transportation networks (ETNs), leading to the emergence of coupled power and transportation energy systems (CPTESs). This development introduces new challenges, particularly as DWC technology shifts EV charging demand from residential plug-in charging to charging-while-driving during commuting hours, causing simultaneous congestion in both ETNs and PDNs during peak times. The present work addresses this issue by developing a collaborative optimization framework for CPTESs that incorporates integrated demand responses (IDRs) and EVs battery state-of-charge (SOC). In the ETN, a multiperiod traffic assignment model with time-shiftable traffic demands (MTA-TSTD) is established to optimize travelers' routes and departure times while capturing traffic flow distribution. Meanwhile, effective path generation models with EVs battery SOC are proposed to optimize charging energy during driving and construct the effective path sets for MTA-TSTD. In the PDN, a multiperiod optimal power flow model with time-shiftable power demands (MOPF-TSPD) is formulated to schedule local generators and flexible power demands while calculating the power flow distribution. To enhance temporal and spatial coordination in CPTESs, a distributed coordinated operation model considering IDRs is proposed, aiming to optimize energy consumption, alleviate congestion, and ensure system safety. Finally, an adaptive effective path generation algorithm and an ETN–PDN interaction algorithm are devised to efficiently solve these models. Numerical results on two test systems validate the effectiveness of the proposed models and algorithms. [ABSTRACT FROM AUTHOR]

With the demand for the miniaturization and integration of wireless power transfer (WPT) systems, higher frequency is gradually becoming the trend; thus, the power electronic device has become one of the main reasons for limiting the development. Therefore, further research on high-frequency inverters and purposeful design according to the characteristics of WPT systems are of great significance to promote the development of high-frequency WPT technology. There is still no literature that summarizes all the inverter circuits that can be applied to WPT systems, which makes it extremely difficult to find an inverter that meets the designer's requirements. This paper reviews the high-frequency inverters for WPT systems, summarizes the derived topologies based on power amplifiers and H-bridge inverters, investigates the main factors restricting the development of high-frequency inverters, and analyzes the research directions for future development. [ABSTRACT FROM AUTHOR]

ABSTRACT Output fluctuation and lower transmission efficiency under load and mutual inductance variation are hot concerned in the wireless charging system for power batteries. In this paper, a decoupled tracking strategy is proposed to realize constant voltage (CV) or current (CC) output and high transmission efficiency. The circuit model of series–series compensation network is built, and corresponding transmission characteristics can be derived. First, the load and mutual inductance value can be estimated by measuring the primary electrical information, including the inverter output voltage, current, and the phase error between them. Then load‐independent voltage or current output characteristics under coils misalignment can be maintained by tracking the optimal switching frequency of inverter part. In addition, the value of output voltage or current can be adjusted flexibly for different operation occasions by the employment of pulse‐width modulation. As a result, the load‐independent output characteristics realization and output adjustment can be decoupled. Based on only the primary measuring information, the CV/CC output can be maintained via the proposed hybrid control strategy when the coils misalignment and load variation happen, increasing the robustness of whole wireless power transfer (WPT) system. Furthermore, the soft switching of all power switches in the inverter part can be realized to reduce the switching loss. Compared with previous research, the proposed wireless charging system has a higher power density and a simplified control strategy. Finally, an experimental platform with 60‐V charging voltage and 3.6‐A charging current is built to verify the feasibility of the proposed sys‐tem and control method. [ABSTRACT FROM AUTHOR]

The high adoption of electric vehicles (EVs) and the rising need for charging power in recent years calls for advancing charging service infrastructures and assessing the readiness of the power system to cope with such infrastructures. This paper proposes a novel model for the integrated operation of dynamic wireless charging (DWC) and power distribution systems offering charging service to in‐motion EVs. The proposed model benefits from a hierarchical design, where DWC controllers capture the traffic flows of in‐motion EVs on different routes and translate them into estimations of charging power requests on power distribution system nodes. The charging power requests are then communicated with a central controller that monitors the distribution system operation by enforcing an optimal power flow model. This controller coordinates the operation of distributed energy resources to leverage charging power delivery to in‐motion EVs and mitigate stress on the distribution system operation. The proposed model is tested on a test distribution system connected to multiple DWC systems in Salt Lake City, and the findings demonstrate its efficiency in quantifying the traffic flow of in‐motion EVs and its translation to charging power requests while highlighting the role of distributed energy resources in alleviating stress on the distribution system operation. [ABSTRACT FROM AUTHOR]

In this work, the concept of peer-to-peer energy sharing in wildlife communication systems is explored. In this context, wild animals can share energy wirelessly besides their data communications as they opportunistically come into range of each other. Our goal is to find a way to balance the energy among the nodes and minimize this energy loss. We propose a novel encounter-based energy-sharing scheme, called EBES, that utilizes single and multi-hop transmission to achieve energy balance, minimize energy losses, and maximize the lifetime of the wildlife communication system. EBES is based on a variety of parameters, including the amount of energy left in the system and the nodes' encounter rate, and buffer sizes. In the simulation studies, we considered a wildlife communication network that is involved in data communication and applied EBES over the opportunistic routing protocols such as EBR, Spray&Wait, and Epidemic resulting in a network lifetime increase of 35% and improving the routing protocols performance. Additionally, we compared EBES with the other well-known energy balancing techniques that also contribute to data communication such as EA-Epidemic, EERPFAnt, and OE-OLSR and the results show the remaining energy was improved by 31%, 26%, and 15%, respectively. [ABSTRACT FROM AUTHOR]

Wireless rechargeable sensor network (WRSN) has become the most effective solution to the energy problem in wireless sensor networks (WSNs) by introducing mobile chargers (MCs) to replenish energy for energy‐starved sensor nodes. In the studies of WRSN, there has been growing interest in using lightweight unmanned aerial vehicles (UAVs) as MCs to overcome geographical constraints. Recently, automatic landing pads (PADs) have been introduced in the UAV‐based WRSN, enabling the UAV to automatically replenish energy during the charging flight. Consequently, the UAV's service range is enlarged, and the UAV can now perform large‐scale charging services. In this paper, we investigate the periodic charging scheduling problem in this novel form of WRSN with the goal of minimizing the charging delay. We present the problem's definition and model and prove it is NP‐hard. To address this problem, we propose two periodic charging schemes: SNBC (sensor‐node‐based charging scheme) and PBC (PAD‐based charging scheme). We extensively simulated our proposed schemes in a UAV‐based WRSN with PADs, evaluating them based on two key metrics: charging delay and UAV replenishment frequency. The results indicate the efficiency of our approaches. SNBC averaged a 7.2 × 104 s charging delay, while PBC outperformed it with a 14.01% reduction in charging delay and a 13.66% decrease in replenishment frequency. [ABSTRACT FROM AUTHOR]

With the deepening of research on wireless power transfer (WPT) technology, there is an urgent need to improve the output power of WPT systems. Therefore, this paper proposes a power boosting method based on a multilevel inverter and dual-resonant network. The system adopts a five-level inverter whose output voltage contains rich fundamental and harmonic components. The transmitting side adopts a dual-resonant compensation network, and, through its parameter configuration, the system can be in a resonant state at both the fundamental and third harmonic frequencies. The receiving side adopts two receiving channels which can simultaneously receive power at both frequencies, thus boosting the output power. Firstly, the overall structure and operating principle of the system are introduced. Then, the relationship between the system output power and efficiency with the inverter modulation parameters is obtained and the strategy for selecting the optimal operating points of the inverter is designed by comprehensively considering the THD of the inverter output voltage and the efficiency of the system. Furthermore, the proposed system is simulated in a Matlab/Simulink platform. Finally, an experimental setup is created to verify the proposed method. The results show that, compared with the single-channel WPT system, the proposed method can enhance the output power from 160 W to 310 W with a boosting coefficient of nearly double and with the highest efficiency exceeding 92%. [ABSTRACT FROM AUTHOR]

For the safe autonomous operations of unmanned aerial vehicles (UAVs) and ground control stations (GCS), including autonomous battery replacement, wireless power transfer, and more, the precise landing of UAVs on GCS is essential. Accurate landing is only possible when the link capacity strength exceeds a certain threshold, but this is often disturbed due to complex terrain. To address this, we developed an extremum seeking (ES)-based radio signal strength optimization (RSSO) algorithm, ES-RSSO, designed to find the optimal positions of the UAV using radio communication signals. This ensures energy-efficient path planning while guaranteeing the minimum received signal strength indication (RSSI) capacity. This algorithm is particularly useful in obstacle-rich environments, where UAVs are limited in power resources. Simulation results demonstrate a 2.37% decrease in the mean, a 62.08% improvement in variance, and a 3.72% decrease in the integration strength of the link capacity when ES-RSSO is applied. These results confirm that the RADIO.rssi maintenance ability remains above a critical boundary level, supporting robust communication links and energy-efficient path planning. Throughout the study, we showed how, in many cases, simply moving the UAV a few meters can significantly improve the communication link. [ABSTRACT FROM AUTHOR]

Laser wireless energy transmission is a widely utilized method, yet its efficiency is constrained by a variety of factors. In order to improve the conversion efficiency of the receivers of the laser wireless power transmission (LWPT) system, the square elliptic hyperboloid (SEH) concentrating module designed for LWPT system receivers is developed. By analysing the I–V characteristic curves from the results of the experiments and employing non‐linear parameter regression, a corrected battery characteristic curve was derived within a specific laser irradiation range. On this basis, an optical–thermal–electric multi‐field coupling characteristic model was developed. The finite element method is used to simulate the multi‐field coupling characteristics and conversion efficiency of the receiving end under diverse working conditions (including different rotation angles and different divergence angles) of the concentrating photovoltaic module. Research shows: First, the larger the divergence half‐angle β of the laser beam, the more obvious the improvement of the effective optical efficiency of the system by the SEH concentrator. Second, the short‐circuit current and the maximum output power of the PV cell at the receiving end are significantly improved by the SEH concentrator, and the improvement effect is more obvious with the increase of the divergence angle and the rotation angle. Third, SEH concentrators did not significantly affect the fill factor of PV cells. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to solve the problem that both the speed and the required driving power of electric vehicles (EVs) will change during the dynamic wireless charging (DWC) process, making it difficult to charge EVs with a constant power considering the overall efficiency of DWC system, the numbers of EVs and the power supply capacity. Therefore, this paper proposes the power control and efficiency optimization strategies for multiple EVs. Design/methodology/approach: The wireless power charging system for multiple loads with a structure of double-sided LCC compensation topology is established. The expressions of optimal transmission efficiency and optimal equivalent impedance are derived. Taking the Tesla Model 3 as an example, a method to determine the number of EVs allowed by one transmitter coil and the overall charging power is proposed considering EV speed, power supply capacity, safe braking distance and overall efficiency. Then, the power control strategy, which can adapt to the changes of EV speed and the efficiency optimization strategy under different numbers of EVs are proposed. Findings: In this paper, a method to determine the numbers of EVs allowed by one transmitter coil and the overall charging power is proposed considering EVs speed, power supply capacity, safe braking distance and overall efficiency. The accuracy of the charging power is good enough and the overall efficiency reaches a maximum of 91.79% when the load resistance changes from 5Ω to 20Ω. Originality/value: In this paper, the power control and efficiency optimization strategy of DWC system for multiple EVs are proposed. Specifically, a method of designing the number of EVs and charging power allowed by one transmitter coil considering the factors of EV speed, power supply capacity, safe braking distance and overall efficiency is designed. The overall efficiency of the experiment reaches a maximum of 91.79% after adopting the optimization strategy. [ABSTRACT FROM AUTHOR]

Summary: In wireless charging systems for electric vehicles, fluctuations in coil mutual inductance can affect both system output power and efficiency. This paper introduces a coil mutual inductance model that accounts for metal shielding material. The formula for coil mutual inductance is derived using Maxwell's equations and boundary conditions. Additionally, the paper presents a tactic for adapting the mutual inductance with the aid of an intelligent optimization algorithm, which is utilized for steadying the mutual inductance of the transmission coil. Lastly, a model of the transmission coil is developed to authenticate the practicality of the mutual inductance equation and the adaptation scheme. Measurement and calculation results indicate that the difference between the calculated value of the mutual inductance formula and the actual mutual inductance value of the coil, following deflection and offset, is below 5%. Moreover, the algorithm, along with the employed adaptation strategy, consistently demonstrates effectiveness in maintaining the mutual inductance value within a predefined range. The temporal efficiency of the algorithm, as measured by the time taken to determine this coordinate position, is consistently under 1 s. This ensures that the algorithm exhibits a rapid response time, a crucial attribute in ensuring its practical utility. [ABSTRACT FROM AUTHOR]

The classical methods for optimizing wireless power transfer (WPT) systems using mathematical equations or finite element methods can be time-consuming and may only sometimes yield optimal designs. In order to overcome this challenge, this paper introduces a novel approach integrating machine learning techniques with meta-heuristic methods to design and optimize a miniaturized, high-efficiency WPT receiving coil for biomedical applications. The objective is to achieve dimensions below 20 mm, a depth of 30 mm within the tissue, and a frequency of 13.56 MHz. Our approach leverages a neural network (NN) model to predict efficiency based on geometric coil parameters, eliminating the need for complex equations. The NN was trained on a dataset generated via finite element method simulations. We employ two meta-heuristic algorithms, the genetic algorithm and the coyote optimization method, to find optimal parameters that maximize efficiency. Our NN model demonstrates exceptional accuracy, exceeding 97%. Furthermore, the proposed WPT coil design approach enhances transfer efficiency by up to 76%, significantly reducing computation time compared to classical methods. Finally, we validate our results using finite element simulation with Ansys Maxwell 3D. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) system in seawater exhibits distinct transmission characteristics from those in air due to the unique properties of seawater medium and the complexity of the seawater environment. In this paper, transmission characteristics of a 2-transmitter (2TX) and 1-receiver (1RX) WPT system in the frequency band of 350 ~ 550 kHz in seawater are investigated. When the transfer distance is at midrange, the maximum load voltage point of the system is shifted from 460 to 430 kHz compared to that in air, and the maximum transfer efficiency is 7 times of that in air, which is very different from the traditional view that the transfer efficiency in water is always worse than in air. The system maintains a stable output voltage when the receiving coil is at different offsets. To grasp the influence mechanism of seawater on wireless power transfer, two new parameters, complex self-inductance and complex mutual inductance, are introduced into the circuit model to explain the shift of the optimal frequency and the increase of transfer efficiency, and the model is verified through experiments. [ABSTRACT FROM AUTHOR]

The secondary pad is desired to be as light as possible and take up less space in the wireless charging applications such as e-bikes. In this paper, a novel disc coil arrangement is proposed to reduce the surface area occupied by the secondary pad. This coil pair has two concentric spiral windings on the primary side and a spiral double-layered coil on the secondary-side. The analytical approaches used to calculate inductance and parasitic capacitance have been generalized, applied to the novel coil arrangement. Analytical results have been confirmed by measurements and FEA. The electromagnetic field noises of the air-core reference coil pair and the novel coil arrangement were examined by using 2D FEA, and the superiority of the proposed coil arrangement in terms of leakage magnetic fields was shown. The self-resonance frequency and quality factors were also examined. On the other hand, since the total wire length used on the primary and secondary sides decreased, up to 3% improvement has been achieved in power transfer efficiency (PTE). The usage area of the secondary pad decreased by 22.13%, but a higher magnetic coupling according to the initial planar coil pair has been measured in the case of up to 40% misalignment. [ABSTRACT FROM AUTHOR]

Introducing collaborative relay and simultaneous wireless information and power transfer (SWIPT) techniques into a cognitive wireless network, named the SWIPT-enabled cognitive relay network (CRN), is considered a promising approach to deal with insufficiency and the low utilization of spectrum resources, as well as the node's energy-constrained issues in wireless networks. In this paper, to improve the network spectrum efficiency (SE) and energy efficiency (EE) of the SWIPT-enabled CRN, we design an energy-efficient adaptive bidirectional transmission strategy. To be specific, we first select an energy-constrained best relay node with the consideration of signal-to-noise ratio and global channel gain to achieve a better bidirectional relay transmission (BRT). At the same time, we let the energy-constrained best relay node transmit a signal with the SWIPT technique, which can solve the node's energy-constrained issue and improve the network EE. Then, with the selected energy-constrained best relay node, we design a total transmit power threshold (TTPT) determining algorithm to find the TTPT, which lets the total transmission rate of the BRT be equal to the bidirectional direct transmission (BDT). Based on this TTPT, we further design an adaptive bidirectional transmission strategy and let the network achieve adaptive transmission between the BRT and BDT to obtain a higher network SE. Furthermore, to further achieve the energy-efficient transmission of the adaptive bidirectional transmission strategy, we optimize the nodes' power under the requirement of primary users' interference threshold and obtain the analytical expressions of the optimal power. Simulation results show that the transmission rate, the outage probability, and the EE of the designed energy-efficient adaptive bidirectional transmission strategy in the SWIPT-enabled CRN are, respectively, 3.01, 0.07, and 3.10 times that of the non-collaborative transmission, which show the effectiveness of our designed transmission strategy. [ABSTRACT FROM AUTHOR]

In this letter, a novel integrated sensing and communication (ISAC) scenario with wireless power transfer (ISAC‐WPT) is investigated. In this new setup, an access point simultaneously employs communication and sensing beams to serve a communication user, detect an RFID tag, and power an energy receiver. The objective is to design the sensing and communication beams to minimize the total transmit power while satisfying the requirements of tag detection, communication, and energy harvesting. To address the corresponding non‐convex problem, the constraints are reformulated into convex second‐order cone constraints, thereby obtaining the globally optimal solution. To further reduce computational complexity, zero‐forcing is employed to design the beamforming vectors, followed by solving a convex optimization problem to determine the optimal power allocation between sensing and communication beams. The simulation results demonstrate the effectiveness of the proposed beamforming designs, highlighting the potential of ISAC‐WPT Backscatter RFID systems. [ABSTRACT FROM AUTHOR]

The parameter variations of magnetically coupled resonant wireless power transmission (MCR‐WPT) system cause frequency splitting and resonant frequency shift, which lead to the system detuning and reduce the transmission efficiency. To solve the problems, a frequency tracking control method based on the phase difference between the primary‐side voltage and the secondary‐side current (Frequency Tracking Control‐the primary‐side voltage and the secondary‐side current, FTC‐PS) in this paper. According to the characteristics that the phase difference between the voltage of transmitting side and the current of receiving side is not affected by frequency splitting, the phase difference is controlled at 90°, so that the system can achieve the maximum transmission efficiency under the condition of frequency splitting and resonant frequency shift. The experimental results show that the method can make the system always work at the natural resonant frequency when the parameters change, and the transmission efficiency is not affected by the frequency splitting phenomenon. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Summary: Radio frequency (RF) energy harvesting (EH) for wireless networks provides a green and sustainable solution and offers an energy‐efficient system. It is most crucial for fulfilling the power requirement of the rising number of low‐powered wireless devices and achieving sustainable development goals (SDG). It ensures the longevity of devices in the network even at inaccessible remote locations. Such RF‐EH‐based mechanisms are utilized in simultaneous wireless information and power transfer (SWIPT) systems. Most of the prevailing studies have analyzed the SWIPT system over conventional fading channels. However, due to the higher rate requirements, the current paradigm shift in frequency usage shifts towards the GHz band, which also offers better EH efficiency. Hence, SWIPT system analysis over the channel that is suitable for mm‐wave signal propagation is dealt with in this study. This study evaluates SWIPT performance over fluctuating two‐ray (FTR) fading channel that is crucial since it provides the best fit for characterizing GHz signal and also provides a generalized framework for most of the conventional fading channels. This study presents new analytical results assuming time switch relaying (TSR) protocol with (i) amplify and forward (AF) and (ii) decode and forward (DF) relaying. The results are also analyzed for H branches maximal ratio combining (MRC) diversity technique and evaluated the diversity gain for both AF and DF relays. The effectiveness of the system is measured in terms of system outage probability (SOP) to envisage the reliability of SWIPT based system. This work presents the simulation and modeling of such system and its obtained results are validated by Monte Carlo simulations for their accuracy. [ABSTRACT FROM AUTHOR]

Space solar power is an old idea. From its initial suggestion in the 1940s to the first practical concept by Dr. Peter Glaser in 1968, it has been analyzed, studied, and refined many times. Multiple government institutions, including NASA, JAXA, ESA, and CAST have invested significant funds into developing direct space solar power research. In parallel to these direct studies, considerable investment has also flowed into enabling technologies that serve as the cornerstone of current space solar power development concepts, including space solar panels, space hardware manufacturing, low-cost launch, wireless power transfer, robotic assembly, and swarm monitoring/control. In the last few years, space solar power concepts and studies have received increased funding, including non-governmental funding showing a strong positive growth trend. Multiple reports in 2021 and 2022, including from this author, have found that while space solar power has been technically feasible for decades, falling launch and hardware costs have only recently made it economically viable as well. Despite these findings, translation from economic feasibility to economic reality will require additional high-value investment. Sourcing these new funds requires investment context. This technical paper will present a state of the industry report on space solar power, including the total and source distribution of historical investments. It further contextualizes the investments in space solar power with the scale of investment in key technologies and their current technology readiness levels. The methodologies developed for this report and the data sourced are intended to serve as a catalyst, alongside industry feedback, to create a template for ongoing reporting of this growing market sub-sector and ultimately drive the full deployment of this technology. • NASA found in 1979 that Space Solar Power was technically and economically viable. • A half-century later solar power cost has fallen 99.8 %, launch has fallen 97.6 %. • A given solar panel will produce 6–20 times as much energy in space. • Direct investment into space solar power has reached $879 million. • Critical indirect investment, including into solar PV, is in hundreds of billions. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) is a promising technology that has the potential to revolutionize the present methods of power transmission. This paper aims to provide an overview of WPT, including its history, a comparative review of methods, and a review of recent papers about WPT. We discussed different methods of WPT, such as inductive power transmission, capacitive power transmission, optical power transmission, and microwave power transmission. The research briefly discusses the applications, challenges, and opportunities of WPT. The study's findings suggest that WPT can serve as a feasible substitute for traditional wired power transmission. This technology has the potential to offer several advantages, including enhanced convenience, decreased expenses, and heightened safety. [ABSTRACT FROM AUTHOR]

Implantable medical devices (IMDs) have become indispensable for treating various health disorders and monitoring individual well-being as a result of significant technical breakthroughs in the field of biomedical technology. This article describes a wireless powering technique at 2.45 GHz for low power devices such as IMDs. The design incorporates a rectangular patch antenna that exhibits peak gain of 2.1 dB and impedance bandwidth of 620 MHz with compact size of 71.4 mm3. The antenna is simulated within a three-layer phantom model replicating the human body to evaluate its performance, which produces −21.4 dB peak gain and 600 MHz–10 dB impedance bandwidth. A full wave rectifier aided by matching network is used to accomplish optimal conversion of RF signal to DC power. The constructed prototype is tested in a saline solution, and the measured results closely match the simulation results. Specific Absorption Rate (SAR) is calculated using a phantom model and a head model for assessing patient safety and biocompatibility. The proposed antenna has SAR values of 5.12 W/kg and 3.13 W/kg are exhibited by proposed antenna inside three layer phantom model and human head model. [ABSTRACT FROM AUTHOR]

Transitioning from petrol or gas vehicles to electric vehicles (EVs) poses significant challenges in reducing emissions, lowering operational costs, and improving energy storage. Wireless charging EVs offer promising solutions to wired charging limitations such as restricted travel range and lengthy charging times. This paper presents a comprehensive approach to address the challenges of wireless power transfer (WPT) for EVs by optimizing coupling frequency and coil design to enhance efficiency while minimizing electromagnetic interference (EMI) and heat generation. A novel coil design and adaptive hardware are proposed to improve power transfer efficiency (PTE) by defining the optimal magnetic resonant coupling WPT and mitigating coil misalignment, which is considered a significant barrier to the widespread adoption of WPT for EVs. A new methodology for designing and arranging roadside lanes and facilities for dynamic wireless charging (DWC) of EVs is introduced. This includes the optimization of transmitter coils (TCs), receiving coils (RCs), compensation circuits, and high-frequency inverters/converters using the partial differential equation toolbox (pdetool). The integration of wireless charging systems with smart grid technology is explored to enhance energy distribution and reduce peak load issues. The paper proposes a DWC system with multiple segmented transmitters integrated with adaptive renewable photovoltaic (PV) units and a battery system using the utility main grid as a backup. The design process includes the determination of the required PV array capacity, station battery sizing, and inverters/converters to ensure maximum power point tracking (MPPT). To validate the proposed system, it was tested in two scenarios: charging a single EV at different speeds and simultaneously charging two EVs over a 1 km stretch with a 50 kW system, achieving a total range of 500 km. Experimental validation was performed through real-time simulation and hardware tests using an OPAL-RT platform, demonstrating a power transfer efficiency of 90.7%, thus confirming the scalability and feasibility of the system for future EV infrastructure. [ABSTRACT FROM AUTHOR]

This paper outlines a design approach for biomedical wireless power transfer systems with a focus on three-coil inductive links for neonatal intensive care unit applications. The relevant literature has been explored to support the design approach, equations, simulation results, and the process of experimental analysis. The paper begins with a brief overview of various power amplifier classes, followed by an in-depth examination of the most common power amplifiers used in biomedical wireless power transfer systems. Among the traditional linear and switching amplifier classes, class-D and class-E switching amplifiers are highlighted for their enhanced efficiency and straightforward implementation in biomedical contexts. The impact of load variation on these systems is also discussed. This paper then explores the basic concepts and essential equations governing inductive links, comparing two-coil and multi-coil configurations. In the following, the paper discusses foundational coil parameters and provides theoretical and experimental analysis of both two-coil and multi-coil inductive links through step-by-step measurement techniques using lab equipment and addressing the relevant challenges. Finally, a case study for neonatal intensive care unit applications is presented, showcasing a wireless power transfer system operating at 13.56 MHz for powering a wearable device on a patient lying on a mattress. An inductive link with a transmitter coil embedded in a mattress is designed to supply power to a load at distances ranging from 4 cm to 12 cm, simulating the mattress-to-chest distance of an infant. the experimental results of a three-coil inductive link equipped with a Class-E power amplifier are reported, demonstrating power transfer efficiency ranging from 75% to 25% and power delivery to a 500 Ω -load varying from 340 mW to 25 mW over various distances. [ABSTRACT FROM AUTHOR]

Increasing the radiated microwave penetration depth is the key to breaking the limitations of the action range in the lossy human body for non-invasive microwave technologies such as microwave hyperthermia, microwave imaging, and the wireless charging of implantable devices. This paper presents a method to increase the radiated microwave penetration depth in the lossy human body by matching the complex impedance of the skin surface using a two-layered medium. The proposed method avoided the impedance mismatch caused by the real impedance assumption of the skin surface for a lossy human body when using the traditional method. Therefore, the reflection loss on the skin surface could be significantly reduced, thereby increasing the penetration depth of the radiated microwave. Moreover, this method could select a suitable medium for the matched Layer 1 by adjusting the relative permittivity of the matched Layer 2, which is more practical than the single-layer-medium optimization method where the relative permittivity cannot be adjusted. The full-wave simulation results showed that the microwave penetration depth of the proposed method at an input power of 0.5 W was 21.01 mm and could significantly increase by 83.18% and 21.37% compared with those in a no-matched layer model and in a traditional 1/4 wavelength medium match method, respectively. [ABSTRACT FROM AUTHOR]

Wireless Power Transfer (WPT) can effectively solve the problem of autonomous power supply for low-power devices. Rectifier is the key component in WPT technology. In this paper, a novel impedance matching network for the broadband rectifier is proposed. This impedance matching network compensates for the diode impedance and reduces its impedance change when the frequency or input power changes. The passive boosting mechanism utilizing coupled transmission lines (CTLs) improves the power conversion efficiency (PCE) of the diode in the low power region. The structure is especially optimized for low-power device applications. For validation, a broadband rectifier operating at 1.9–3 GHz is fabricated and measured. The structure fabricated on the Rogers 4003 substrate with a thickness of 1.508 mm and the diode is HSMS2860. The DC voltage V o u t on the load ( R L = 1300 Ω) was measured. The results show that at 0 dBm, the PCE keeps more than 60% at 1.98–3 GHz. The peak PCE of 79.6% is obtained at 4 dBm. The compact size of the broadband rectifier is 19 mm × 21 mm. This broadband rectifier for low input power ranges can be applied to WPT technology. [ABSTRACT FROM AUTHOR]