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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]

Maximum efficiency tracking (MET) with multiple concurrently-activated transmitters (TXs) has not yet been investigated thoroughly. This paper proposes a fast real-time estimation of coupling coefficients and load resistance for multiple concurrently-activated TXs and a moving RX. This is the first paper that demonstrates iteration-less, fast, communication-less MET with power regulation when the RX is moving across multiple activated TX array. The controller senses only the voltage magnitude of TX coil-capacitor resonator, and the input DC voltage and DC current of inverter. Once the parameters are estimated, the controller sets the converters to maximum efficiency point immediately. The benefits of proposed method are that it does not require a communication channel, extra circuit components for MET, time-consuming iterations and computations, and periodic interruption of power flow due to load disconnection or initialization, all of which were limitations in typical methods. Experimental results show that the proposed method provides a fast response (3.8ms) for an RX moving at 6.84 km/h across multiple TXs.

In recent years, optical camera communication (OCC) has garnered attention as a research focus. OCC uses optical light to transmit data by scattering the light in various directions. Although this can be advantageous with multiple transmitter scenarios, there are situations in which only a single transmitter is permitted to communicate. Therefore, this method is proposed to fulfill the latter requirement using 2D object size to calculate the proximity of the objects through an AI object detection model. This approach enables prioritization among transmitters based on the transmitter proximity to the receiver for communication, facilitating alternating communication with multiple transmitters. The image processing employed when receiving the signals from transmitters enables communication to be performed without the need to modify the camera parameters. During the implementation, the distance between the transmitter and receiver varied between 1.0 and 5.0 m, and the system demonstrated a maximum data rate of 3.945 kbps with a minimum BER of 4.2 × 10 − 3 . Additionally, the system achieved high accuracy from the refined YOLOv8 detection algorithm, reaching 0.98 mAP at a 0.50 IoU. [ABSTRACT FROM AUTHOR]

Multiple-input multiple-output (MIMO) wireless power transfer (WPT) technology which employs multiple transmitter (TX) coils to simultaneously couple power to the receiver (RX) coil has proved to be an effective technique to enhance power transfer efficiency (PTE). Conventional MIMO-WPT systems rely on the phase-calculation method based on the phased-array beam steering concept to constructively combine the magnetic fields induced by the multiple TX coils at the RX coil. However, increasing the number and distance of the TX coils in an attempt to enhance the PTE tends to deteriorate the received signal at the RX coil. In this paper, a phase-calculation method is presented that enhances the PTE of the MIMO-WPT system. The proposed phase-calculation method considers the coupling between the coils and applies the phase and amplitude to calculate the coil control data. From the experimental results, the transfer efficiency is enhanced as a result of the transmission coefficient improvement from a minimum of 2 dB to a maximum of 10 dB for the proposed method as compared to the conventional one. By implementing the proposed phase-control MIMO-WPT, high-efficiency wireless charging is realizable wherever electronic devices are located in a specific space. [ABSTRACT FROM AUTHOR]

In recent years, optical camera communication (OCC) has garnered attention as a research focus. OCC uses optical light to transmit data by scattering the light in various directions. Although this can be advantageous with multiple transmitter scenarios, there are situations in which only a single transmitter is permitted to communicate. Therefore, this method is proposed to fulfill the latter requirement using 2D object size to calculate the proximity of the objects through an AI object detection model. This approach enables prioritization among transmitters based on the transmitter proximity to the receiver for communication, facilitating alternating communication with multiple transmitters. The image processing employed when receiving the signals from transmitters enables communication to be performed without the need to modify the camera parameters. During the implementation, the distance between the transmitter and receiver varied between 1.0 and 5.0 m, and the system demonstrated a maximum data rate of 3.945 kbps with a minimum BER of 4.2×10−3. Additionally, the system achieved high accuracy from the refined YOLOv8 detection algorithm, reaching 0.98 mAP at a 0.50 IoU.

Wireless power transfer (WPT) technology has been widely introduced and developed over the past few years. Nevertheless, the basic WPT configuration using one transmitting (Tx) coil and one receiving (Rx) coil still achieves very limited performance in terms of power transfer distance. To overcome this limitation, various multi-coil WPT systems using three or more coils have been studied. Among them, a multiple-input single-output (MISO) structure can provide the Rx with advanced freedom in an extensive lateral area. However, few studies have investigated how far multi-Tx coils can increase the transfer distance. In this paper, we analyze the transfer distance and lateral coverage based on the generalized critical coupling condition and system energy efficiency according to the number of additional Tx coils in the MISO WPT system. The results demonstrate that the MISO WPT system using planarly arranged Tx coils improves by barely 1% in the optimal transfer distance, which achieves the maximum output power condition in a single-Tx WPT system. To validate our analysis, the MISO WPT system with seven Tx coils and seven LCC inverters was implemented and its performance was assessed. The measured results agreed well with the theoretically calculated results.

A demand-customized selective wireless power transfer system is proposed in this article. Multiple receivers can be recognized based on their positions and the magnetic field in the powering area can be controlled and regulated accordingly. For authorized receivers, the system can simultaneously deliver power to meet different output requirements for different electrical appliances, while for unauthorized ones, they can be shut down independently for energy security, even when they are also in the powering area. Compared to the traditional calculation models for multi-input multi-output systems, the proposed current control algorithm uses a piecewise optimization procedure to simplify the iteration and improve control flexibility. Hybrid-frequency pacing is adopted as the control strategy to further reduce the output fluctuation and raise the system efficiency. An experimental prototype with a 3 × 3 transmitter matrix is established. The system can successfully power two receivers with the same sizes for four different power requirement scenarios, which validates the selectivity and the controllability of the proposed system. [ABSTRACT FROM AUTHOR]

In multi-input wireless power transfer (WPT) systems, it is plagued to create a destructive interference between the multiple transmitters to result in a relatively low voltage delivered to the receiving coil and load, due to the phase differences of the received voltages from different transmitters. In this regard, it is essential to synchronize the phases of the received voltages of the receiving coil from different transmitters. However, the existing offline synchronization methodologies rely heavily on an analytical form solution of the received voltage in a receiver. In most engineering application scenarios, such close-form solution is almost impossible. Moreover, the close form solution, even if possible, will vary with the operating conditions and environments. To eliminate these deficiencies of existing synchronization methodologies, an online synchronization methodology is proposed for a multi-input WPT system. In the proposed methodology, the received voltages from different transmitters are determined from a series of online voltage samplings under different offset phases, and a synchronization strategy is then proposed and implemented. A multi-input WPT prototype is developed to test the feasibility of the proposed synchronization methodology. The experimental results have demonstrated that the received voltage is significantly enhanced by applying the proposed online phase synchronization methodology. [ABSTRACT FROM AUTHOR]

Multiple-input multiple-output (MIMO) wireless power transfer (WPT) technology which employs multiple transmitter (TX) coils to simultaneously couple power to the receiver (RX) coil has proved to be an effective technique to enhance power transfer efficiency (PTE). Conventional MIMO-WPT systems rely on the phase-calculation method based on the phased-array beam steering concept to constructively combine the magnetic fields induced by the multiple TX coils at the RX coil. However, increasing the number and distance of the TX coils in an attempt to enhance the PTE tends to deteriorate the received signal at the RX coil. In this paper, a phase-calculation method is presented that enhances the PTE of the MIMO-WPT system. The proposed phase-calculation method considers the coupling between the coils and applies the phase and amplitude to calculate the coil control data. From the experimental results, the transfer efficiency is enhanced as a result of the transmission coefficient improvement from a minimum of 2 dB to a maximum of 10 dB for the proposed method as compared to the conventional one. By implementing the proposed phase-control MIMO-WPT, high-efficiency wireless charging is realizable wherever electronic devices are located in a specific space.

With the widely applying of inductive power transfer (IPT) sharing platforms in public, the security issue imposed by the leaked electromagnetic field (EMF) of standby transmitters (Txs) becomes one of the concerned topics. Multiple Txs may be an effective scheme to suppress the leaked EMF for which each Tx can be controlled independently. For the traditional technologies, multiple inverters, sensors, or wireless communication links are needed to achieve load detection and independent control, which increases the cost and reduces the system's reliability. This work presents an IPT system with dual secondary loops, which only needs a single inverter and can automatically control the Txs by its circuitry reflective property. The system can enhance the transmitting current when Rx couples with Tx and weaken that when Rx does not couple with Tx. Furthermore, a capacitor array is added in the secondary circuit to adapt different primary reactances by utilizing a simple switching-control method. Finally, a prototype that can transfer 112 W with a dc–dc efficiency of 91.79% is built to validate the feasibility of the proposed system. The experimental results show that the current in coupled Txs is three times higher than that in uncoupled Txs as per the theoretical analysis. [ABSTRACT FROM AUTHOR]

This article proposes and implements a selective wireless power transfer (WPT) system based on magnetic field editing technology. Compared with the traditional WPT without control of power regions, the proposed system can deliver the energy with higher safety, flexibility, selectivity, and can be applied to multiple receivers. The algorithms for current calculation and synchronized control strategies are given to construct the desired magnetic field effectively. The optimization process based on the receiver configuration and voltage threshold is also demonstrated. Both simulation and experimental results validate that the magnetic field distribution can be arbitrarily edited through the proposed current control strategy, and realize the selectivity of the powering area. A prototype of the proposed system with five transmitters is constructed and tested, which can successfully deliver wireless power of 14 W over the distance of three times larger than the radius of the receiver coil with the transmission efficiency over 79%. [ABSTRACT FROM AUTHOR]

The widespread need for ubiquitous power delivery is driving the commercialization of inductive wireless power transfer (WPT). Wireless power transfer systems, however, are plagued by low efficiency. To combat this, we propose a new approach to maximize the efficiency of inductive WPT using multiple coil charging systems. The use of multiple coils can potentially allow the system to efficiently adapt to magnetic field propagation conditions, similar to the way multiple antennas are used to adapt to channel conditions in wireless communication systems. We consider a multiple-input single-output WPT system using near-field inductive coupling. While such systems have been extensively studied in previous work using lumped resistance, inductance, and capacitance (RLC) circuit models to analyze their behavior, the difficulty of constructing tractable and realistic circuit models has limited the ability to accurately predict and optimize the performance of these systems. The main innovation in this paper is to take a more abstract approach to modeling the WPT system as a linear circuit whose input-output relationship is expressed in terms of a small number of unknown parameters that can be thought of as transimpedances and gains. The crucial advantage of this approach is the economy of the representation, i.e., the number of unknown model parameters can be much smaller than the number of lumped circuit elements required for a complete and accurate RLC circuit representation. We present simple derivations for the optimal voltage excitations to be applied at the transmitters to maximize power transfer efficiency as well as suboptimal excitations which are less computationally intensive. A simple procedure, which we call circuit sounding, for estimating the unknown parameters using a small set of direct measurements is described. We outline a series of experiments with four transmit coils and two receive coils that verify the model and show that the optimal solution can achieve higher efficiencies than those of previously known methods.

In this study, the problems, which simultaneously extract and direct positioning of multiple transmitters, are considered. Without assuming a priori knowledge of the source number, the multiple signal classification (MUSIC) algorithm is applied after using the Akaike information theoretic criteria for model order determination, while the minimum variance distortionless response (MVDR) algorithm can be directly used to localise multiple sources that transmit unknown signals. Two methods, which combine MUSIC and MVDR with the image expansion (IE) algorithm, are proposed. The IE algorithm used in actual scenarios is based on the constant-false-alarm rate. Simulation results show that the proposed algorithms can effectively extract and accurately localise multiple transmitters.

In terms of the passive position determination problem, the most commonly used methods are based on two-step processing. While here, the authors propose a technique that estimates the locations of transmitters by processing the raw signals from all receivers at the central processor, which belongs to the direct position determination (DPD) concept. There are already efforts made on single target localisation through eigenvalue maximising based on the DPD technique. While the multi-target case encountered more commonly in realistic scenarios. By additionally combined with the image expansion algorithm, the sources can be extracted effectively and their positions are determined simultaneously. Simulation results illustrate that the localisation accuracy for each transmitter is equivalent to the two-step based approach at high signal-to-noise ratio (SNR). While for low SNR, the superiority and accuracy of the proposed method are also manifested.

In this study, the problems, which simultaneously extract and direct positioning of multiple transmitters, are considered. Without assuming a priori knowledge of the source number, the multiple signal classification (MUSIC) algorithm is applied after using the Akaike information theoretic criteria for model order determination, while the minimum variance distortionless response (MVDR) algorithm can be directly used to localise multiple sources that transmit unknown signals. Two methods, which combine MUSIC and MVDR with the image expansion (IE) algorithm, are proposed. The IE algorithm used in actual scenarios is based on the constant-false-alarm rate. Simulation results show that the proposed algorithms can effectively extract and accurately localise multiple transmitters. [ABSTRACT FROM AUTHOR]

In terms of the passive position determination problem, the most commonly used methods are based on two-step processing. While here, the authors propose a technique that estimates the locations of transmitters by processing the raw signals from all receivers at the central processor, which belongs to the direct position determination (DPD) concept. There are already efforts made on single target localisation through eigenvalue maximising based on the DPD technique. While the multi-target case encountered more commonly in realistic scenarios. By additionally combined with the image expansion algorithm, the sources can be extracted effectively and their positions are determined simultaneously. Simulation results illustrate that the localisation accuracy for each transmitter is equivalent to the two-step based approach at high signal-to-noise ratio (SNR). While for low SNR, the superiority and accuracy of the proposed method are also manifested. [ABSTRACT FROM AUTHOR]

Radio-on-free-space-optical (RoFSO) communication systems have attracted a lot of technological interest in the last few years, due to their high performance characteristics with relatively low installation and operational cost. At the same time a lot of research has been carried out on them. This specific technique facilitates the transmission of radio frequency signals with the aid of optical carriers through the atmosphere; its effectiveness is already known from the Radio over Fibre (RoF) links. However, besides their advantages, the performance of free-space optical (FSO) communication links depends strongly on the atmospheric conditions, due to the fact that the propagation path is the atmosphere. In the present work, we consider the transmission of OFDM radio signals, with QAM modulation format, through an FSO link, using spatial diversity of the receivers. For the estimation of the system performance the atmospheric turbulence effect has been modelled by the gamma-gamma distribution, the accuracy of which spans from weak to strong turbulence conditions. Furthermore, the pointing errors effect is studied with the aid of a new generalized distribution that takes account the nonzero boresight displacement of the optical beam from the optical receiver centre. In addition, different spatial jitters are taken into consideration for the two vertical axes of the receiver. Thus, accurate mathematical expressions are extracted, which lead to the estimation of the average BER and the outage probability of a spatially diverse QAM OFDM RoFSO link. Finally, the theoretical results obtained from the derived expressions are verified through the corresponding numerical simulations which are presented at the numerical results section of the manuscript. [ABSTRACT FROM AUTHOR]

The paper proposes optimal driving conditions of two transmitters (TXs) in magnetic wireless power transfer, where the couplings from each TX to an RX are not identical. First, for the case of identical TX coil currents, a criterion for deactivating a specific TX element is proposed. Specifically, one TX element among the two TXs often has weaker coupling coefficient than the other TX element. It is found that the TX element with weaker coupling should be deactivated if its coupling coefficient is less than 0.414 times of the stronger coupling. Second, for the case of adjustable TX coil currents, the optimal current ratio between the two TX coils is proposed. It is found that the TX coil current ratio should be equal to the coupling coefficient ratio, e.g., the TX coil with twice coupling with an RX should carry twice current. The results are widely applicable regardless of absolute coupling strength and load condition because it turns out that the results only depend on the ratio of couplings. Finally, it is discussed that the required component values of an LCC inverter should be adjusted based on the current ratios and coupling between adjacent TXs. [ABSTRACT FROM AUTHOR]

Multiple transmitters powering a single receiver simultaneously is a good alternative to upgrade the power capacity of the wireless power transfer (WPT) system by using multiple modular inverters manufactured in a larger quantities, since the demand for high power applications is on the rise. A multiple overlapped transmitters based WPT system is presented in this paper. In order to alleviate the effects of the cross couplings between the transmitters, additional capacitors are adopted in the transmitters and the configuration of additional capacitors is provided. Virtual active and reactive powers are defined to decompose the transmitter current into active and reactive components. A transmitter current control scheme based on the proposed current decomposition method consisting of one reactive current control loop and one active current control loop is also presented in this paper. Finally, a low-scale experimental setup using two overlapped transmitters WPT system is provided to verify the proposed approach. The experimental results indicate that the proposed method could improve the stability of output voltage control and achieve minimal current difference amongst transmitters. Besides, the overall system efficiency is improved to 90.34% with the proposed control method at 1.45 kW output power, which demonstrates that the proposed method is a potential solution for high power applications. [ABSTRACT FROM AUTHOR]

An optimization procedure for multitransmitter multiple-input single-output (MISO) wireless power transfer (WPT) systems based on tight semidefinite relaxation (SDR) is presented. This method ensures physical realizability of MISO WPT systems designed via convex optimization—a robust, semianalytical, and intuitive route to optimizing such systems. To that end, the nonconvex constraints requiring that power is fed into rather than drawn from the system via all transmitter ports are incorporated in a convex SDR, which is efficiently and reliably solvable by dedicated algorithms. A test of the solution then confirms that this modified problem is equivalent (tight relaxation) to the original (nonconvex) one and that the true global optimum has been found. This is a clear advantage over global optimization methods (e.g., genetic algorithms), where convergence to the true global optimum cannot be ensured or tested. Discussions of numerical results yielded by both the closed-form expressions and the refined technique illustrate the importance and practicability of the new method. It is shown that this technique offers a rigorous optimization framework for a broad range of current and emerging WPT applications. [ABSTRACT FROM PUBLISHER]

This paper presents a rigorous optimization technique for wireless power transfer (WPT) systems enhanced by passive elements, ranging from simple reflectors and intermediate relays all the way to general electromagnetic guiding and focusing structures, such as metasurfaces and metamaterials. At its core is a convex semidefinite relaxation formulation of the otherwise nonconvex optimization problem, of which tightness and optimality can be confirmed by a simple test of its solutions. The resulting method is rigorous, versatile, and general—it does not rely on any assumptions. As shown in various examples, it is able to efficiently and reliably optimize such WPT systems in order to find their physical limitations on performance, optimal operating parameters, and inspect their working principles, even for a large number of active transmitters and passive elements. [ABSTRACT FROM PUBLISHER]

Wireless power transfer systems with multiple transmitters promise advantages of higher transfer efficiencies and focusing effects over single-transmitter systems. From the standard formulation, straightforward maximization of the power transfer efficiency is not trivial. By reformulating the problem, a convex optimization problem emerges, which can be solved efficiently. Further, using Lagrangian duality theory, analytical results are found for the achievable maximum power transfer efficiency and all parameters involved. With these closed-form results, planar and coaxial wireless power transfer setups are investigated. [ABSTRACT FROM PUBLISHER]

Multiple transmitters can be used to simultaneously transmit power wirelessly to a single receiver via strongly coupled magnetic resonance. A simple circuit model is used to help explain the multiple-transmitter wireless power transfer system. Through this particular scheme, there is an increase in gain and “diversity” of the transmitted power according to the number of transmit coils. The effect of transmitter resonant coil coupling is also shown. Resonant frequency detuning due to nearby metallic objects is observed, and the extent of how much tuning can be done is demonstrated. A practical power line synchronization technique is proposed to synchronize all transmit coils, which reduces additional dedicated synchronization wiring or the addition of an RF front-end module to send the reference driving signal. [ABSTRACT FROM PUBLISHER]

A compound probability density function (pdf) model is used for the outage analysis of a multiple input multiple output (MIMO) scheme operating in shadowed fading channels. Instead of the lognormal pdf, the compound pdf uses a gamma distribution to account for shadowing, leading to a closed form expression for the pdf of the signal-to-noise ratio in a shadowed fading channel. While the mitigation of short term fading is achieved through the use of multiple transmitters and multiple receivers, the shadowing is mitigated with macrodiversity using two base stations. Taking into account the fact that shadowing has a larger correlation distance, the two base stations are treated to have nonzero correlation. It is shown that the expression for the outage probability in a MIMO scheme operating in shadowed fading channels can be written in a simple form eliminating the need for numerical evaluation of double integrals. Results demonstrate the usefulness of the approach for the analysis of MIMO schemes. [ABSTRACT FROM PUBLISHER]

Serving video-on-demand (VOD) traffic via isochronous transmission service is highly desirable because of the characteristics of VOD traffic. This paper proposes a mechanism to transfer VOD traffic over wavelength division multiplexing (WDM) networks by employing isochronous transmission service. Based on the proposed mechanism, the problem of scheduling isochronous and asynchronous traffic for single-star WDM networks with multiple receivers and transmitters is investigated. The lower bounds on the total switching duration and the number of switching modes for the isochronous and asynchronous traffic scheduling problem are derived. An optimal scheduling algorithm is presented for the cases where only asynchronous traffic exists; and a heuristic algorithm is also proposed for the cases where both the isochronous and asynchronous traffic coexist in the WDM networks. Simulation results indicate that the average switching duration and the average number of switching modes obtained by the proposed algorithm are close to the lower bounds, which implies that the proposed scheduling algorithm is effective [ABSTRACT FROM PUBLISHER]