As a cable-free energy transmission method, wireless power transfer (WPT) offers significant advantages over wired transmission in terms of safety and applicability. It boasts features such as contactless operation, flexibility, convenience, and wide applicability, making it suitable for diverse fields. However, challenges such as transmission distance, efficiency, and device size limit its widespread application. To address issues like bulky device size and low efficiency in WPT systems, we propose the integration of a four-armed helical surface structure into a dual-coil WPT system in this study. This design aims to enhance both transmission efficiency and distance. The structure’s simplicity and compactness notably reduce the size of WPT devices, thereby expanding the feasibility of wireless charging for small equipment.

We first simulate and optimize the parameters of the proposed four-armed helical surface structure using 3D electromagnetic simulation software. Subsequently, we experimentally verify the effect of this structure on optimizing the transmission efficiency and increasing the transmission distance of the dual-coil WPT. In addition, the dual-coil WPT system with the four-armed helical surface structure is analyzed using the Fano resonance principle, which explains the physical mechanism underlying the enhanced transmission efficiency. Finally, to further elucidate the role of spatial field regulation in this system, we simulate and calculate the electromagnetic field during the transmission process, and utilize magnetic field distribution diagrams to illustrate changes in the spatial field.

The designed four-armed helical surface structure is integrated with a dual-coil system at near-field transmission distances, which greatly reduces the structure size. By incorporating the four-armed helical surface structure, the broadband transmission mode between the transmitting coil and the receiving coil [Fig. 7(b)], and the narrowband resonance mode between the resonant surface and the transmitting coil [Fig. 7(a)], interfere with each other. This interference induces the Fano localized resonance effect [Fig. 7(c)], enhances the electromagnetic field distribution near the receiving coil (Fig. 8), and improves both transmission efficiency and distance (Figs. 5 and 6), making it more suitable for practical near-field applications. Furthermore, the four-armed helical surface structure also effectively shields the propagation of near-field energy in the non-transmission direction and provides significant magnetic field shielding at the bottom (Fig. 8).

We introduce the Fano resonance effect into a dual-coil wireless power transfer system using a four-armed helical surface structure. The localization of Fano resonance is leveraged to control the spatial electromagnetic field of the wireless power transfer system. The results demonstrate that the four-armed helical surface structure effectively combines with the dual-coil structure to achieve the Fano resonance effect. This localized resonance regulates the spatial electromagnetic field between the dual-coils, significantly boosting the transmission efficiency of the wireless power transfer system. Additionally, the introduction of the four-armed helical surface structure acts as a shield for the spatial electromagnetic field opposite to the wireless power transfer direction of the dual-coil, thereby improving the spatial electromagnetic field energy. Moreover, the surface structure is simple and easy to integrate, offering a high-efficiency transmission solution for wireless charging technology.