Obstacle-Immune Microwave Wireless Power Transfer System Based on Amplitude-Dependent Caustic Metasurface.

Rapid advances in the Internet of Everything (IoE) drive microwave wireless power transfer (MWPT) technology for charging wireless smart devices. However, environmental obstacles and safety concerns associated with high-power transmission present new challenges for the technology. To address these problems, an amplitude-dependent caustic metasurface (ADCMs) design method is proposed for generating self-bending radio frequency circular Airy beams (RFCAB). The self-accelerating circular Airy beam has a natural hollow region, providing an obstacle avoidance and safety zone during microwave transmission focusing. The ADCMs, derived from caustic theory, are capable of generating RFCAB with arbitrary curvatures and offer flexible control over the positioning of the energy focus. An innovative feed architecture, a uniform circular array (UCA) emitting vortex electromagnetic waves, is used to match the amplitude excitation on which the metasurface depends. The designed ADCMs consists of 1/3 wavelength units and contains only two layers of substrate, with high transmittance and full 360 phase coverage, ensuring efficient beam generation and manipulation. Simulation and experimental analyses demonstrate the obstacle-avoidance characteristics and safety features under high-power transmission of ADCMs-based MWPT systems. The proposed MWPT system is anticipated to offer an effective obstacle avoidance and safety solution for the wireless charging of devices within the IoE.