An Investigation of Lithium-ion Battery Induced Near Field Electromagnetic Interference in Wearable Audio Devices

Recently, lightweight, compact, and imperceptible wearable products push the interaction between consumers and electronic devices to a new level. However, they also pose more challenges in terms of EMC design. On one hand, it is also necessary to change the methods of coupling path analysis from large 2D-like circuit boards design to full 3D stacking since the predictable interferences have changed from traditional PCBs, high-speed/high-power IC, to various sensors and components with high sensitivity. Furthermore, in extreme compact stacking conditions, it is difficult to predict the spatial distribution of electric and magnetic fields and how they may affect various devices. On the other hand, the impact of electromagnetic interference on sensitive devices extends beyond the simple degradation of electronic performance. It directly impacts the user's perception and experience, which puts higher demands on the product level EMC design.In this paper, the TWS (True Wireless Stereo) earbuds are used as an example to illustrate an interdisciplinary electromagnetic analysis method that encompasses the fields of electromagnetics, battery design, acoustics, RF, and baseband. Our study analyzes the electromagnetic radiation emitted by batteries, and proposes high-precision models of batteries and high-sensitivity speakers. In order to verify its accuracy, we have compared the simulation and actual measurement and we have also proposed a new anti-interference battery to address these issues.