Wireless Power Transfer Using Oscillating Magnets

The advancement of portable and implantable electronic devices has driven active research into wireless power transfer (WPT) methods. Current commercial WPT techniques using coil coupling have limitations, such as range, frequency, safety, line of sight, orientation, and concurrency. This paper presents a system utilizing oscillating magnets to extract power from a low-level ac magnetic field. This system enables the simultaneous powering of multiple low-power devices in an environment that meets human safety requirements. Compared with conventional WPT techniques, such as RF or acoustic power transfer, the proposed system transfers stable power to electronic nodes placed anywhere within the magnetic field under low driving frequency. Theoretical power calculations and experimental demonstrations are presented to prove the concepts and quantify performance. A custom three-dimensional printed millimeter-size oscillator loaded with two 8
${\text{mm}^{3}}$
cubic permanent magnets is employed as the energy receiver to experimentally validate the proposed system. Measurements show that the raw ac electrical power and rectified dc power received by the oscillator achieve 269 and 135
${\mu {\text{W}}}$
, respectively, under 400
${\mu{\text{T}}}$
excitation magnetic field amplitude at 355
${\text{Hz}}$
.