Nonlinear Metasurfaces for Health-Monitoring Magnetic Induction-Based SWIPT Base Stations

Metasurfaces based on periodic arrays of high-
$Q$
coils have been used as artificial lenses to boost the power transfer efficiency of magnetic induction (MI)-based power transmission systems. In conventional linear topologies, the metamaterial (MTM) focalization effect is physically limited to an extremely narrow bandwidth (BW) due to the high-
$Q$
of MTM cells. Through accurate large-signal numerical simulations and experimental measurements, this article demonstrates that nonlinear MTM lenses inspired by the Duffing resonator can produce a substantial and stable gain (up to 16 dB) over a two-times wider BW compared to the linear case. With modulated excitations (quadrature phase shift keying (QPSK) signals), such a gain reaches 17 dB. Furthermore, the proposed lens is proven to reduce the peak-to-average power ratio (up to 4 dB) and the magnetic channel attenuation as a function of the data rate. The proposed MTM lenses are believed to have great potential in developing high-performance, low-cost MI-based base stations for simultaneous wireless information and power transmission in health-monitoring wireless body area networks.