Arbitrarily Conformal Metasurfaces for Enhanced Wireless Power Transfer Systems

In this paper, design guidelines and unique features of arbitrarily conformal metasurfaces for Wireless Power Transfer (WPT) systems are discussed. In particular, we demonstrate the flexibility of conformal metasurfaces in achieving different behaviors by proposing two different applicative test cases: 1) magnetic field shielding in the region behind an RF coil, as typically required in automotive WPT scenarios, and 2) wireless power transmission with a magnetic field distribution spatially focused by the metasurface, eventually useful for electromagnetic exposure and interferences reduction. In general, the metasurface design is performed by following an analytical method that allows controlling and tailoring its response even though the array is finite, conformal and near-field excited. For both the implementations, the analytical design was corroborated by accurate full-wave simulations and experimental measurements carried out at 13.56 MHz. In particular, the possibility to obtain a 8 dB shielding effectiveness of an RF coil magnetic field at distances larger than twice of its diameter was proved. Conversely, in the second implementation, the conformal metasurface was capable to guarantee a measured power transfer efficiency of 8% for a receiver placed in correspondence of the 4 cm diameter focusing spot, while drastically reducing the magnetic field everywhere else. The results demonstrated the excellent potentialities of conformal magnetic metasurfaces for WPT applications in ensuring the electromagnetic safety for operators while simultaneously achieving enhanced performance.