A novel micromachined magnetic-field sensor

Optimization of Sensing Stators in Capacitive MEMS Operating at Resonance

“…Furthermore, for technological reasons, this principle is verified with two suitable structures, formed by a clampedclamped beam (rotor) and properly designed stators. The considerable improvements in the overall sensitivity predicted by simulations based on the rarefied gas theory are demonstrated by experimental results: in a representative example, the beams are driven by an AC current at resonance and used as Lorentz-force-based magnetometers [4]. It is experimentally demonstrated that, in this condition, one proposed structure shows an overall sensitivity which is 3× better than what obtained on devices based on continuous parallel plate stators and packaged in the same pressure conditions [6].…”

“…In this context several inertial MEMS (gyroscopes [2], [3] and magnetometers [4]) operate with at least one mode excited at resonance, with frequencies in the order of tens of kilohertz. For a given input quantity to be measured this allows to obtain the maximum output signal as described by the behavior of a second-order under-damped system [5].…”

A 3-D Micromechanical Multi-Loop Magnetometer Driven Off-Resonance by an On-Chip Resonator

“…The strategy here adopted to improve robustness against these effects is the use (for all the axes) of an architecture that implements a capacitive sensing configuration which inherently rejects accelerations as a common mode, differing from most of previous works, especially for Z-axis devices [2], [4], [14], [18], [19], [21], [34]. The strategy is further completed by the shift of the mode sensitive to accelerations to high frequencies, as discussed below.…”

“…From most of these standpoints, such devices (see e.g. the performance in [1]- [4]) are rapidly becoming competitive with commonly adopted technologies like Hall-effect, magnetic tunnel junction (MTJ) and anisotropic magneto-resistance (AMR) devices [5], [6]. This achievement is due to the conception and refinement of new operating principles, like parametric amplification [7], internal thermal-piezoresistive amplification [8], nonlinear sensitivity enhancement [9], off-resonance operation [1] or frequency modulation (FM) [2].…”

A Sub-400-nT/<inline-formula> <tex-math notation="LaTeX">$\sqrt {\text {Hz}}$ </tex-math></inline-formula>, 775-<inline-formula> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula>, Multi-Loop MEMS Magnetometer With Integrated Readout Electronics

“…Manuscript Currently, only a few works have addressed integrated electronics for Lorentz-force MEMS magnetometers [1]. Concerning the MEMS sensing element and its operation, most works exploited AC currents injected at the device resonance frequency (resonant operation) to amplify the Lorentz-force induced motion with a high quality factor [5]- [9]. In other words, the magnetic field induces, through the Lorentz force, an amplitude modulation (AM) of the resonant displacement of the MEMS suspended frame (this operating scheme resembles open-loop operation in modematched gyroscopes [10]).…”