Fig. 1. Schematic diagram of four-armed spiral surface structure

Fig. 2. Equivalent circuit diagram of four-armed helical surface structure

Fig. 3. Diagram of WPT with four-armed helical surface structure

Fig. 4. Diagram of experimental setup of WPT system containing four-armed helical surface structure

Fig. 5. Measurement and simulation plots of S₂₁ for WPT systems with and without four-armed helical surface

Fig. 6. Measured variations of S₂₁ with transmission distance for WPT systems containing four-armed helical surface structure and dual-coil

Fig. 7. Phenomena of Fano resonance. (a) Four-armed helical surface structure and transmitting coil; (b) transmitting coil and receiving coil; (c) WPT system with four-armed helical surface structure

Fig. 8. Distributions of magnetic field intensity in longitudinal section. (a) Spatial magnetic field distribution of WPT system with four-armed helical surface structure; (b) spatial magnetic field distribution of dual-coil WPT system

Fig. 9. Distributions of spatial magnetic field intensity at position 1. (a) WPT system containing four-armed helical surface structure; (b) dual-coil WPT system

Fig. 10. Distributions of spatial magnetic field intensity at position 2. (a) WPT system containing four-armed helical surface structure; (b) dual-coil WPT system

Fig. 11. Distributions of spatial magnetic field intensity at position 3. (a) WPT system containing four-armed helical surface structure; (b) dual-coil WPT system