A Displacement-based TMR-type Accelerometer For A High Sensitivity With A Low 1/f Noise

Accelerometers are widely applied in consumer electronics,inertial conduction and other fields.In the past decade,the rise of new concepts example span national defense,commercial space and metaverse facilitates the accelerometers boom in frontier areas.Nonetheless,the conventional commercial accelerometers represented by capacitive,piezoelectric,piezoresistive,etc.,are typically hindered by performance to applied in high precision field.Recently,diverse accelerometers based on new detection mechanism spring up like bamboo shoots with unique merits.Among them,Tunnel Magneto Resistance(TMR),as the fourth generation of magnetoresistance,owing high sensitivity,wide linear range,low power consumption and good stability,has occupied 90% of the magnetic head market.Utilizing tunnel magnetoresistance endow the accelerometer of cost-effective fabrication and high sensitivity.Therefore,the development of an ultra-high performance tunnel magnetoresistance accelerometer has great research potential and market space.Herein,an ultra-high performance tunnel magnetoresistance accelerometer is proposed,with high sensitivity,high resolution and low cross axis interference.Firstly,a new structure integrating acceleration sensing and 1/f noise suppression is designed.Then,based on the magnetic field theory and vibration theory,the accelerationdisplacement-magnetic-electric coupling theoretical model is established,and the input-output relation is derived.These prove the accelerometer can realize ultra-high linearity acceleration sensing.Further,in modulation and 1/f noise suppression,the principle of modulation-demodulation is expounded,and a magnetic field modulation method based on magnet is proposed.Additionally,three factors affecting the sensitivity of accelerometer are analyzed,and a sensitivity enhancement scheme based on beam structure is proposed.Based on the equivalent stiffness of the beam,the enhancement effect of the mouth-beam on the sensitivity was deduced,and the relationship between the structural parameters of the mouth-beam and the sensitivity amplification factor was established.Aforementioned is verified by simulation and the influence curves of the structural parameters of the mouth-beam on the sensitivity are drawn.Based on theory and simulation,a tunnel magnetoresistance accelerometer prototype is fabricated and experimentally studied.The sensor experiment platform is designed and built,demonstrating the prototype could realize the sensing of acceleration with sensitivity of 48 m V/g.Further,a comparative experimental platform is designed and built,demonstrating the sensitivity enhancement function of different beam structures and obtaining the sensitivity of 126 m V/g.Moreover,cross-axis interference experiments are carried out to verify the minimal cross-axis sensitivity of the proposed structure.Furthermore,the influence of noise on the resolution of the accelerometer is analyzed.The theory of modulation noise suppression is established for the first time.In this theory,the modulation efficiency is defined,the relation between the modulation efficiency and the modulation structure is derived,and the design principle that the displacement of the modulation structure should be proportional to the change of the magnetic field is expounded.Under the guidance of the theory,the modulation structure with 100% modulation efficiency is designed,and the simulation results show that the modulation efficiency is 97%,which verifies the correctness of the theory.Further,the experimental platform of acceleration sensing with modulation and noise suppression is designed and built.In the experiment,the prototype obtains 87% modulation efficiency and 20μg/√Hz resolution.In addition,this theory is applied to other sensors such as galvanometer,which proves that the theory has certain universality.Together,this study,addressing the two major problems of sensitivity and resolution of existing tunnel magnetoresistance accelerometers,provides a solution idea and experimental reference for researchers to excavate the advantages of high sensitivity of tunnel magnetoresistance and suppress the disadvantages of high noise in accelerometers,which will greatly contribute to the practical application and further development of accelerometers and tunnel magnetoresistance.