Optimized Low-Power Flexible Magnetic-Coupling Antenna for Wearable Devices

Flexibility and low-power consumption are desirable for wearable magnetic-coupling antennas. In order to achieve these configurable designs, in this paper, we proposed an antenna architecture in which a coaxial distributed diameter coil with twisted loops antenna (DDC-TLA) is integrated with a flexible ferromagnetic core and a rubber-nature substrate. Through adjusting the diameter distribution of the DDC-TLA, the magnetic field distribution is adjusted to enhance communication reliability. While through moderating the weight ratio of the nanostructured magnetodielectric material, the concentration of the polymer hybrid solution and the filler content of the rubber substrate, the quality factor of the antenna is tailed to meet performance requirements. Furthermore, through an optimized algorithm, the preferable structure of the DDC-TLA and the suitable ingredient of the ferromagnetic core are determined, while the power loss are minimized. Finally, simulations and experiments are conducted to corroborate our studies.

I. Introduction

Mechanical deformability [1], [2] and miniaturization [2], [3] of passive electronic components are essential in fitting the space of a wearable device, which also desires a low power for a long standby time [4]–[6] and a low radiation [7], [8]. However, although an air-core coil shows good elasticity, it usually has diffusive magnetic field lines that weaken its signal strength. A solid magnetic core usually has hard stiffness and large weight density that narrow their uses. While a low input resistance usually results in nonmonotonous signal damping oscillation [9], large signal overshoot [10], [11], and frequency shift [12].