Design Optimization of a Lorentz Force, Amplitude Modulated, MEMS Space Magnetometer

摘要

This paper reports a MEMS magnetometer with geometrical improvements to increase the displacement resulting from Lorentz forces. It relies on lever-like suspension springs which present over tenfold lower electrical resistance (thus allowing higher currents) than conventional guided-beam springs with the same compliance. By combining multiple Lorentz force generating bars and off-resonance operation in vacuum (1 mbar), these devices can yield: noise of 2.65 nT/√Hz (theoretical) with bias current of 4 mA in each of the 6 Lorentz bars (63.6 nT.mA/√Hz) and sensitivity of $50.5 mathrm{aF}/mu mathrm{T} (1 mathrm{aF}.mu mathrm{T}^{-1}.mathrm{mA}^{-1}; 102 mu mathrm{V}/mu mathrm{T}$ with the electronic readout), corresponding to a 20 nT resolution (1 aF capacitance variation), over a 50 Hz bandwidth. This resolution figure over such large bandwidth is unprecedented whether for amplitude-modulated or frequency-modulated Lorentz force magnetometers.