A Comparative Analysis of Fully-Digital and Dynamic Metasurface Antenna Architectures for Energy Beamforming in Wireless Power Transfer

This paper investigates trade-offs between fully-digital (FD) and dynamic metasurface antenna (DMA) architectures for energy beamforming in near-field wireless power transfer (NF-WPT). We consider a NF-WPT system in which an antenna array, which can be either an FD or a DMA structure, charges devices at the same time while avoiding transmitting power to specific directions, such as areas where people or animals may be present. Then, we optimize the transmit power to charge the intended devices while strictly avoiding these restricted areas. Results reveal that the FD array offers superior spatial resolution and is able to provide very concentrated energy beams, with low radiated power outside the intended directions. Nevertheless, its hardware complexity is considerably high due to the need of one RF chain per antenna element. Conversely, the DMA enables energy beamforming with a reduced total power consumption, standing out as a highly scalable solution. However, the energy beams provided by the DMA show non-negligible scattering, especially at distances closer to the DMA, thus making the restriction to avoid unintended users more challenging.