Planar spiral coils in high-frequency wireless power transfer systems suffer from increased loss due to skin and proximity effects. The PCB Litz wire structure is proposed to suppress eddy current losses and improve the quality factor. Optimized design parameters are obtained through theoretical analysis and electromagnetic simulations. Simulation results confirm reduced AC resistance in the kilohertz range and a higher quality factor compared with conventional solid-wire coils. The proposed approach provides an effective solution for high-performance and compact WPT systems.

With the vigorous advocacy of green communication, research on energy harvesting technology in mobile communication resource allocation has become increasingly urgent. This paper studies the resource allocation problem of multi-relay energy harvesting systems. To improve the diversity gain of the relay system, an improved three-phase energy harvesting relay protocol is proposed. Complete with established non-convex optimization models and transform them into quasi-convex problems through convex optimization methods. Then, by constructing a nonlinear programming model with optimal energy efficiency, parameters such as energy harvesting time slot allocation, subcarrier pairing, and power allocation are jointly optimized. Finally, the Dinkelbach method and Hungarian algorithm were used to iteratively obtain the optimal solution. The Monte Carlo simulation experiment verified the accuracy and fast convergence of the algorithm.

This study first proposes a planar alternating winding coil (PAWC) integrating a magnetic backplate, adopting a dual-sided alternating winding architecture on dielectric substrates. The proposed PAWC system features three fundamental characteristics: load-independent constant-current output, broad-range high-efficiency power transfer, and inherent no-load protection. During no-load operation, the transmitter exhibits high-impedance characteristics, effectively entering a zero-current shutdown state that completely prevents the overcurrent risks typical of series-series (S-S) compensated systems. When the receiver approaches the charging position, the system autonomously shifts to a zero-reactance operating mode at the same working frequency, achieving efficient power transfer without supplemental compensation networks. This design enables state switching purely through relative coil positioning, eliminating the need for additional sensing or switching components. Experimental validation confirms 92.8% coil-to-coil transfer efficiency at 5 mm separation, with efficiency exceeding 90% across 50−300 Ω load variations. These advancements offer particular value for safety-critical applications, including smart home ecosystems and medical implants, where the system's self-regulating switching capability and robust efficiency significantly enhance operational reliability.

Wireless power transfer (WPT) technology, renowned for its reliability and flexibility, is utilized in numerous fields. This article addresses the synchronization of the active rectifier in WPT systems. Traditional methods for synchronization, such as auxiliary coil-based techniques, current sampling approaches, and perturbation observation methods, often suffer from limitations such as communication delays and sensitivity to noise. Meanwhile, they also assume the switch frequency is known. To overcome these flaws, this article proposes a frequency estimation method based on the sampled values of the rectifier bridge's input current. The method accurately estimates the frequency and initial phase angle, thus improving the synchronization performance. Additionally, dynamic clock interpolation technology is introduced to improve synchronization accuracy by compensating for quantization errors in pulse width modulation frequency generation. Simulation and experimental results demonstrate that the proposed method enhances both synchronization performance and stability, even if the realistic frequency is unknown.

By analyzing the resonance frequency and frequency bifurcation characteristics of the wireless power transmission SS compensation system, the characteristic frequencies of the system with stable and strong output robustness are obtained at the frequency bifurcation, and the input impedance does not change with the coupling coefficient at the low-frequency point and the high-frequency point. The system is decoupled from the coupling coefficient, and the system can follow this frequency under the parameter change through the circuit design, to realize the frequency adaptation and a mathematical model to determine the working frequency of the system is established. This shows that the circuit can be approximated as a closed-loop negative feedback system with nonlinear links. Through the method of describing the function to determine the stability frequency of the system, the self-sustaining oscillation frequency of the system during stable operation is solved, the relationship between it and the system parameters is obtained, and the stable operating frequency of the system under the difference of the natural oscillation frequency of the primary and secondary sides is obtained according to the model, and the effectiveness of the model is verified by experiments.

With the gradual approach of 6G network technology, the field of the Internet of Things (IoT) has ushered in unprecedented development opportunities, especially in the intelligent management of tennis. This article focuses on the application of wireless self powered sensor networks in tennis under the 6G network environment, exploring how this cutting-edge technology provides new solutions for monitoring, analysis, and management of tennis. This article proposes wireless and self powered sensor networks to study tennis. Wireless sensor nodes are a fundamental component of wireless sensor networks. This article studies tennis through wireless and self powered sensor networks. Through experiments, it can be clearly seen that the factors affecting the self powered wireless sensor network in tennis show a diversified trend. Experimental data shows that creating a campus tennis atmosphere is crucial for the effective operation of sensor networks, with an impact rate of up to 84%. This indicates that an active and positive tennis culture atmosphere can promote the widespread acceptance and application of sensor networks. Secondly, the transformation of college students' consumption concepts (accounting for 58%) and their understanding and values of tennis (accounting for 49%) also significantly affect the effectiveness of technology adoption. These non-technical factors work together in the intelligent process of tennis, highlighting the important influence of social culture and personal cognition on the application of technological innovation.

This study is centered on maintaining high efficiency within a multi-receiver system in the absence of real coupling information. It explores the derivation of an optimal driving current crucial for efficiency maximization, revealing its reliance on both loading and coupling conditions. Furthermore, an average current is defined based on known coupling ranges, typically accessible during the system's design phase. Employing this derived driving current significantly enhances system scalability with minimal additional requirements in communication, state estimation, and activating circuits. In an experimental setup, a two-receiver system is constructed to contrast the efficiency achieved when possessing real-time coupling knowledge vs solely knowing the coupling range. The observed maximum efficiency difference between these scenarios amounts to 1.7%.

As inductive power transfer (IPT) systems gain increasing attention, optimizing electric field distribution and reducing intensity are crucial to ensuring system safety within electromagnetic exposure limits. This letter addresses the issue of high electric field intensity by introducing a novel interleaved winding configuration. An Inter-Turn Anti-Phase (ITAP) method is also proposed to adjust the placement of distributed compensation capacitors, ensuring that the potential between adjacent turns exhibits opposite-phase characteristics. This adjustment maximizes the cancellation of the inter-turn electric field, effectively reducing the electric field intensity both within the coil gap and in the external environment. Finite element simulations and experimental validation on a 3.3 kW prototype demonstrate that, without observable changes in power transfer characteristics or efficiency, the proposed approach reduces leakage electric field intensity by approximately 40% compared to traditional distribution compensation with an average segmentation. When compared to non-segmented compensation methods, the reduction is around 50%. These results highlight the effectiveness of the proposed method in lowering electric field exposure levels and enhancing the safety of IPT systems.

This paper proposes a mutual inductance and load parameter identification method using an Improved Northern Goshawk Optimization (INGO) Algorithm after pulse frequency modulation (PFM), and validates the effectiveness of the proposed parameter identification method through a maximum efficiency tracking approach. One of the most challenging aspects of wireless power transfer (WPT) technology for electric vehicles is the variation in the magnetic coupling coefficient between the two coils due to inaccurate parking positions and differences in height. First, a steady-state circuit model of an SS-type compensation network and pulse frequency modulation strategy was established to determine the correlation between system parameters. The INGO was then introduced to convert the parameter identification problem into an optimization problem, enabling the identification of load and mutual inductance parameters. Finally, the proposed identification method was experimentally validated, and the maximum efficiency tracking of the proposed WPT system was achieved through a Sepic impedance matching circuit. The results show that the identification method can maintain high accuracy even under coil displacement and load variation conditions.