Giant magneto-impedance sensor with working point selfadaptation for unshielded human bio-magnetic detection  

作　　者：Changlin HAN Ming XU Jingsheng TANG Yadong LIU Zongtan ZHOU 

机构地区：[1]College of Intelligence Science and Technology,National University of Defense Technology,Changsha 410072,China

出　　处：《Virtual Reality & Intelligent Hardware》2022年第1期38-54,共17页虚拟现实与智能硬件（中英文）

基　　金：Supported by the China Postdoctoral Science Foundation(4139ZRL);the National Natural Science Foundation of China(U19A2083).

摘　　要：Background Compared with traditional biomagnetic field detection devices,such as superconducting quantum interference devices(SQUIDs)and atomic magnetometers,only giant magneto impedance(GMI)sensors can be applied for unshielded human brain biomagnetic detection,and they have the potential for application in next-generation wearable equipment for brain-computer interfaces(BCIs).Achieving a better GMI sensor without magnetic shielding requires the stimulation of the GMI effect to be maximized and environmental noise interference to be minimized.Moreover,the GMI effect stimulated in an amorphous filament is closely related to its working point,which is sensitive to both the external magnetic field and the drive current of the filament.Methods In this paper,we propose a new noise reducing GMI gradiometer with a dual-loop self-adapting structure.Noise reduction is realized by a direction-flexible differential probe,and the dual-loop structure optimizes and stabilizes the working point by automatically controlling the external magnetic field and drive current.This dual-loop structure is fully program controlled by a micro control unit(MCU),which not only simplifies the traditional constant parameter sensor circuit,saving the time required to adjust the circuit component parameters,but also improves the sensor performance and environmental adaptation.Results In the performance test,within 2 min of self-adaptation,our sensor showed a better sensitivity and signal-to-noise ratio(SNR)than those of the traditional designs and achieved a background noise of 12 pT/√Hz at 10 Hz and 7pT/√Hz at 200 Hz.Conclusion To the best of our knowledge,our sensor is the first to realize self-adaptation of both the external magnetic field and the drive current.

关 键 词：Brain-computer interface Biomagnetic detection GMI effect Working point self-adaptation Dual-loop control Magnetic gradiometer Differential noise reduction 

分 类 号：TN911.7[电子电信—通信与信息系统] TP212[电子电信—信息与通信工程]