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Achieving three-dimensional (3D) omnidirectional wireless power transfer (OWPT) without any active control is challenging. This paper proposes a square polyhedron transmitter (SPTx) based on the reverse current of parallel coil, which can create a 3D omnidirectional magnetic field. To minimize the counteracting of the reverse magnetic field, each coil is equipped with magnetic shielding material. The coils of SPTx are connected in series and excited by a single power supply without any current amplitude or phase control circuits. The performance of SPTx system is validated with different receivers (Rx) by experiments. In the experiment with dual Rxs, the maximum transmission efficiency is 79.6% with an efficiency stability rate of 49%. In addition, the output power does not affect the efficiency, and more Rxs will increase transmission efficiency. [ABSTRACT FROM AUTHOR]

In this paper, an array multi-transmitter multi-mode wireless power transfer system is proposed. The system realizes the joint modulation of three transmitter coil working modes of single transmitter coil, dual transmittercoil and four transmitter coils in the wireless power transfer system through PI closed-loop control, which can realize the stable output of WPT system in three different transmitter coil work modes. It effectively compensates for the shortcomings of the single working mode of a single transmitter coil and the limited range of effective working areas, and improves the robustness of the wireless power transfer system. [ABSTRACT FROM AUTHOR]

Inductive power transfer (IPT) technology is a promising solution for charging the electric vehicles (EVs) by enabling an EV to charge its energy storage system (battery) without any connecting wires through magnetic coupling. This paper proposes a new receiver design named Hollow Solenoid receiver that is compatible with the standard double-D transmitter defined by the SAE J2954 standard. A deep design analysis for the proposed Hollow Solenoid receiver is presented to define the optimum design parameters for coil (inductances, number of turns, dimensions, wires, etc.) and ferrite core (dimensions, number, arrangement, etc.). Several WPT3 (11.1kVA) solenoid receiver (SR) designs were presented and analyzed based on efficiency, weight, size, volume, and cost. The performance of the proposed SR was compared with the global Double-D receiver (DDR) presented by the SAE J2954 standard under different lateral and rotational alignment and loading conditions considering coupling factor, transmission power and efficiency, and stray electromagnetic fields (EMFs). The entire IPT system including coils, compensation network, power converters, controls, and battery load was modeled and analyzed for both SR and DDR coils. The results reveal that the proposed SR is compatible with the global DD transmitter at different alignment and loading conditions and is able to transmit the desired power (11 kW) at an efficiency > 85%. Hollow SR design shows the highest efficiency and lowest size, weight, and cost compared to DDR and other designs. [ABSTRACT FROM AUTHOR]

In this paper, we study a cognitive radio wireless-powered communication network with an integrated intelligent reconfigurable surfaces system. Actually, massive connectivity and limited energy are the primary challenges to implementing ultra-reliable and low-latency services, as it is extremely difficult to maintain the quality of service and manage the connection of a huge number of users to small cells. So, this paper investigates the application of NOMA-based simultaneous wireless information and power transfer (SWIPT) for massive mobile systems in which the underlay spectrum sharing network is designed to mitigate the interlayer interference such that interference with the primary network is kept less than a predefined level. Problem modeling takes into account residual hardware impairments and channel estimation errors under practical conditions. The communications between the servers and users of NOMA-based small cells are accomplished via an interference-limited multihop connection through intermediate relays. Based on the partial relay selection (PRS) protocol, an optimal relay is selected from K relays to transmit the received signal to multiple user equipment, namely, the far users (FU) and the near users (NU). In addition, to maximize the system total throughput, we formulate the transmitter (Tx)-relay-receiver (Rx) matching problem, which is a mixed-integer nonlinear programming (MINLP) problem. To address this nondeterministic polynomial-time NP-hard problem, we applied a gradient algorithm to obtain a stable matching. The impact of the transmission power, the number of Tx/Rx pairs, and the number of intermediate relays on the sum rate are investigated. Based on the simulation results, the hardware failure parameter has a negative impact on system performance, whereas the channel estimation index is always advantageous to outage probability (OP). Also, the analysis of the energy efficiency and key performance indicators proves that the proposed approach outperforms other similar schemes from the power saving and QoS assurance perspectives. [ABSTRACT FROM AUTHOR]

The use of various technologies to increase efficiency and safety has been continuously increasing. Wireless power transfer (WPT) has emerged as a key technology to increase in this regard. WPT can simplify complex wiring and improve safety by eliminating the need for mechanical contact. Most electronic devices used in buildings are of medium power, and research is being conducted to increase the output power of WPT through the combination of different technologies. This study proposes a 4-Tx WPT system using four transmitters (Tx) to satisfy the power requirements of medium-power electronic devices used in buildings. The existing WPT methods, 1-Tx and 2-Tx, were compared with the proposed 4-Tx WPT. The characteristics of efficiency and output power were analyzed through each Tx phase control of the 4-Tx system. The mutual inductance based on the distance between Tx and Rx was measured, and the relationship between the efficiency and output power was analyzed. Experimental results show that the proposed 4-Tx system is more advantageous in terms of medium power than the existing WPT methods. The proposed WPT system has power control capability, high output power, and high efficiency by adapting the phase control of each Tx. Moreover, it is confirmed that the range of the distance between Tx and Rx that is satisfying the minimum output power of medimum-power electronic device based on the relationship between the efficiency and the output power with the separation distance of Tx and Rx. [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]

Basically, wireless microwave power transfer system has very low power delivery efficiency and this efficiency gets extremely lower as the longer range and higher center frequency. Also, there is no room for the power control of the transmitter in the power supply station in order to keep the wireless power transfer efficiency. So, maximum power must be always transmitted. The time division multiple access (TMDA) system of the wireless microwave power transmission (MPT) is used for the multiple power receiver users. In this paper, an efficient wireless MPT system supporting multiple users power receiver that is a flexible TDMA is proposed based on the power pilot that is the power request signal including the power receiver ID (identification) number and power level status information. That is, this power pilot has the authorized user information and the user's power status information, which is transmitted to the power station for the request of power transmission. The power supply station receives the power pilots from all users. For the user identification of the multiple users, a CDMA system is used in this propose system. Next, the power station recognizes the users power level status and control the order of the power transmission sequence. The lowest power level user receives the wireless power in the first order for the longest time. On the contrarily, the power station transmits the wireless power to the user of the highest power state in the last for the shortest time. So, depending on the power level status of each individual user, the microwave power transmission (MPT) time is assigned and rearranged, which decides the power charge time in user power receiver side. This is a newly suggested flexible time division multiple access (TDMA) MPT system, which allocates power charging time differently to each user, depending on the power level status. This is very meaningful in that power transmission to multiple users is performed according to the power priority. Also, this technology can be extended into multi-user simultaneous transmission system and beamforming technology is also adopted to increase the power transmission efficiency. The phase locked loop (PLL) based retro-directive array (RDA) system is used to each user arrival angle and store the direction information which is used again to send the power to that user. These systems are designed and their performance is verified through the simulations to build and assess the microwave wireless power transmission system that supports multiple users. [ABSTRACT FROM AUTHOR]

The efficiency of Internet of Things (IoT) mobile networks is limited by the battery's capacity in IoT devices. In addition to their replacement/recharge problem, batteries delimit devices' processing and data forwarding capabilities, hence degrading the performance of IoT networks. Recent advances in Wireless Power Transmission (WPT) technology provide an attractive solution, namely Wireless Powered Communication (WPC), in which wireless devices are charged through wireless power transmitters. However, the design and prospect of WPC applications are challenged by the poor efficiency of long-distance WPT. On the other hand, solar energy harvesting is a conventional and natural method for conveying energy wirelessly to devices. This article reviews WPT technology as well as solar energy harvesting and investigates their challenges in IoT networks. It is shown that smart integration of these two energy supply methods to power IoT networks wirelessly leads to more efficient WPCs called green WPC. Three frameworks for green WPC have been investigated in this article. These methods are simulated and analyzed in a network and energy model in separate scenarios. Green WPC is a potential solution to create networks with a longer lifetime and higher reliability and flexibility than conventional battery-based methods. [ABSTRACT FROM AUTHOR]

Intelligent houses and skyscrapers require many electronic devices for the smart control of building conditions. These devices make the power distribution system of buildings too complicated and expensive. Wireless power transfer (WPT) systems are one of the more promising candidates that simplifies power distribution systems. WPT systems via magnetic resonance coupling (MRC) can transmit power further and broader than WPT systems via inductive coupling. Moreover, recent architectures use an H-beam structure due to its durability and recyclability. Since the H-beam structure can be used as a guidance for WPT systems, the performance of the WPT system can be improved. Thus, this paper proposes a WPT system via MRC with aligned two transmitters (2-Txs) and one receiver to simplify the power distribution systems in smart buildings and to improve the power capability of WPT systems. The characteristics of a WPT system with 2-Txs according to variation of coil arrangement, coil size, and distance imbalance are investigated and verified by mathematical analysis and experimental results. In addition, a phase-shift control method is adopted and experimentally verified to control the output power without an additional power conversion circuit. [ABSTRACT FROM AUTHOR]

To improve the degree of freedom (DoF), and the multi-terminal power supply capability of wireless power transfer (WPT) systems, multi-DoF WPT systems for multiple pickups based on magnetic dipole coils are proposed in this paper, which can simultaneously charge multiple receivers regardless of the position degree. First, the equivalent circuit model of the magnetic dipole coils is provided. The critical factors of the proposed multi-load systems are analyzed, such as transfer efficiency, power distribution, and optimal load. Second, a multi-load wireless power transfer system with equal transmitting (TX) and receiving (RX) coil is designed, and the misalignment tolerance of lateral and rotating occasions for the RX coils is discussed. In particular, a multi-load WPT system with miniaturized step-laminated receivers is implemented based on the magnetic dipole coils. Finally, experimental prototypes are established. The obtained results indicate that the output power for the equal dual-load WPT system can reach more than 78 W with a total efficiency of more than 80% under a transfer distance of length of the receiving coil winding. In addition, the output power of the non-equal four-load WPT system can reach 30 W with a total efficiency of 86%. The proposed systems provide practical guidance for the future development of multi-DoF WPT systems for use in portable devices, unmanned intelligent systems, and smart household applications. [ABSTRACT FROM AUTHOR]

Aimed at different demands of power of multiple receiver loads in multiple-input multiple-output wireless power transfer (MIMO-WPT) system, in the paper, a method of calculating the excitation source at the transmitter by general circuit model is put forward to realize the power allocation of the receiver loads. First, the magnetic coupling resonance (MCR) MIMO-WPT system is made to be equivalent to a linear circuit model, and the general circuit model of MIMO-WPT system is established, which describes output transfer characteristics, transmission efficiency and output power of the MIMO-WPT system with parametric state matrix. Then, based on the power demand of each receiver load, the vector expression of the excitation source at the transmitter of MIMO-WPT system is derived by the general circuit model. At last, the simulation experiment of WPT system with 3 transmitting and 2 receiving coils is designed to verify the accuracy of the general circuit model estimation and the feasibility of the power distribution of the receiver load. Meanwhile, the application of the general model provides a feasible solution to solve different power demands of multiple receiving loads in the MIMO-MCRWPT system. [ABSTRACT FROM AUTHOR]

To release more flexibility for users to charge their portable devices, researchers have increasingly developed compact wireless power transfer (WPT) systems in recent years. Also, a dual-band WPT system is proposed to transfer power and signal simultaneously, enriching the system's functionality. Moreover, a stacked metasurface has recently been proposed for a single band near-field WPT system. In this study, a novel multimode self-resonance-enhanced wideband metasurface is proposed for a robust dual-band WPT system, which significantly improves the performance of both bands. The size of the transmitter (Tx) and the receiver (Rx) are both 15 mm × 15 mm only. The proposed metasurface can improve efficiency from 0.04 up to 39% in the best case. The measured figure of merit (FoM) is 2.09 at 390 MHz and 2.16 at 770 MHz, respectively, in the balanced mode. Especially, the FoM can reach up to 4.34 in the lower mode. Compared to the previous state-of-the-art for similar applications, the WPT performance has significantly been improved. [ABSTRACT FROM AUTHOR]

This paper applies the phase conjugation method which is equivalent to time reversal in the time, to wireless power transfer using two different retrodirective array configurations: linear uniform transmitting array and non-planar random transmitting array. The method is based on the reciprocity property of the wave equation. The idea is validated by employing 10 transmitting retrodirective antenna array (Tx) placed on the walls of a cubical room and one receiving antenna (Rx) in free space. In the retro-reflective beamforming, wireless power transmission is guided by pilot signals. The Rx broadcasts pilot signals to its surroundings, and based on analyzing these signals, a wireless power transmitter delivers focused power beam onto the Rx. The study is performed for line of sight and non-line of sight (NLOS) locations for the Rx. We calculate the received (Rx) power for different array configurations, and the power flow density inside the room. Simulation results show that applying the reciprocity theorem in both configurations provides significant enhancement in power transfer system efficiency at different Rx locations. Furthermore, results demonstrate that the power beam in reaction to the pilot signal is capable of tracking the mobile device's location dynamically even if it resides in a NLOS location. When the wireless power receiver resides in the far-zone, a linear array and a random array produce the same power level at the near-zone focal point, but the maximum far-zone gain associated with the random array is on the average 1.5 dB lower than that of the linear array. [ABSTRACT FROM AUTHOR]

We consider the Simultaneous Wireless Information and Power Transfer strategy optimization in the two-way transmission relay system under Power Splitting (PS) receiver. In such case, we propose two operational strategies for two-way transmission under PS receiver structure, (1) Delay-Limited-Relay strategy (PS-LDR) and (2) Delay-Tolerated-Relay strategy (PS-TDR). PS-LDR strategy is that both sending node and receiving node need synchronization of information transmission, so communication systems have higher Signal Noise Ratio (SNR) threshold for channels, or communication may break down. In order to explore the performance of PS-LDR strategy, we use outage probability to calculate the analytical expression of the actual maximum throughput (AMT). PS-TDR strategy allows that the information received by the receiving node delays with the information sent by the sending node. Communication system in PS-TDR strategy has lower SNR threshold than that in PS-LDR strategy. The analytical expression of the AMT is calculated by the ergodic capacity in PS-TDR strategy. The influences of system parameters on the optimal throughput in two strategies are discussed. [ABSTRACT FROM AUTHOR]

To balance the output stability and maximum efficiency of a system, an efficiency optimization method based on adaptive frequency control is proposed. In this paper, load transmission is carried out using a DC–DC converter at the receiving end. When the load changes, controlling the rectified output voltage is carried out to realize the maximum efficiency point tracking. Meanwhile, the duty cycle of the rear stage DC–DC converter is changed to keep the output voltage constant. The sampled rectified voltage is compared with the estimated value and the resulting error data are sent to the system transmitter through ASK modulation wireless communication. Then the transmitter demodulation communication information through PID algorithm control is used to achieve the frequency of the adaptive adjustment. The feasibility of the proposed method has been verified by the simulation and experimental results. When the output voltage is 5 V, the constant voltage accuracy is within ± 1%, the maximum efficiency is up to 79.2%, and the dynamic response time is only 160 ms. [ABSTRACT FROM AUTHOR]

This paper presents a new on–off keying modulation circuit for a Class-E power transmitter used in high-data-rate wireless links used for powering medical implants. A circuit technique is proposed to keep the current of the RF choke of the power transmitter constant, while the transmitter turns on and off. This allows the transmitter to quickly turn on and off. To prove the feasibility of the proposed circuit, a wireless power and data transfer link based on the proposed circuit was designed and implemented. At a carrier frequency of 2.5 MHz, the measured data rate was 625 kbps, which means that a data-rate-to-carrier-frequency ratio of 25% has been achieved. The power transfer efficiency and the power delivered to the load, with a 2.37-μH transmitter coil and a 1.4-μH receiver coil separated by a 1.0-cm air gap, were measured to be 21% and 80 mW, respectively. The measured bit error rate of the link was less than 10−5. [ABSTRACT FROM AUTHOR]

This paper presents a new type of a transmitter coil for wireless power transfer (WPT) to assist in the achievement of a constant output power and in the reduction of magnetic field leakage under misaligned electric vehicle (EV) wireless-charging conditions. The proposed DDP coil is an improvement upon the conventional DD coil and can be adaptively reconfigured depending on the misalignment of different sizes or types of receiver coils. The reconfigurable resonant circuit is designed to compensate various coil structures and to maintain a high-energy efficiency. The reconfiguration strategy is presented by studying the characteristics of the magnetic field and mutual inductance of the coils. A precise human anatomic model and a full-scale Tesla EV model are built to evaluate the magnetic field leakage and human exposure to the WPT system. Simulation results show that the power transfer efficiency (PTE) reaches 99.16% and that the maximum electric field induced in humans is − 1.11 dBV/m, while the transfer power is 6.6 kW with a 12 cm lateral offset on both the x-axis and y-axis. The effectiveness of the proposed type of transmitter coil is verified through simulation and experimental results. [ABSTRACT FROM AUTHOR]

An important challenge in the wireless power transfer is the sizing of the coils for transmission and energy reception. The output power in a wireless power transfer system can be determined by analytical formulation; however, the effects of using some geometry or material for the transmitter and receiver coil assembly are not easily quantifiable by the analytical method. This work quantifies by numerical simulation the impact on output power changing the separation between the transmitter coil and receiver, materials, geometries and number of turns. The quantities obtained allowed to determine a model for coupling coefficient to compute optimal frequency for the power transfer. The analysis and evaluation of these parameters were developed through an electromagnetic simulator with finite element; the work considers planar circular and square coils. Experimental results were obtained in order to validate the proposed model to compute the wireless power transferred. The document contributes to identify the important parameters to be controlled or modified in the coils with the purpose to optimize the power transmission for a wireless system. [ABSTRACT FROM AUTHOR]

Device-to-Device (D2D) communication and wireless small cell networks (SCNs) are two of the most promising paradigms in next generation cellular technologies. However, interference management is a major issue in regard to the use of either or both technologies. In this paper, we propose a D2D pair underlying SCNs using Wireless Power Transfer (WPT) technology. In particular, we have a D2D transmitter and D2D receiver underlying SCNs and operate in close proximity to a SCN primary user (PU). Two scenarios are proposed. The first scenario is when the best base station (BS) link is chosen to harvest energy from, and a second scenario where energy is harvested from all available SCN BSs. The transmission between the D2D pair is kept under a certain threshold so it could not have any harmful effects on the transmission link of PU. The results reveal that the number of interference users shows negative effect on the performance of the considered system. Besides, the primary network's peak interference constraint has significant influence on the optimal value of energy harvesting time at the D2D transmitter. [ABSTRACT FROM AUTHOR]