Lorentz force MEMS magnetometer with frequency modulated output

This work presents a frequency output micromachined silicon magnetometer comprised of a low stiffness thermal-piezoresistive electromechanical resonator coupled to a Lorentz force generator. The Lorentz force generator utilizes a leverage mechanism amplifying the force by ~55X. Upon application of a magnetic field perpendicular to the device, the leveraged Lorentz force deflects the resonator central beam changing its resonance frequency. Frequency modulated output, compared to amplitude modulated output, offers significantly improved noise and interference robustness and can be directly fed to a digital counter without the need for extensive signal conditioning and analog to digital conversion. Sensitivity of 7200 ppm/T/mA has been measured for the presented design showing frequency shifts as high as 0.123ppm/μT for a bias current of 17mA.