Performance Improvement of a Capacitive MEMS Accelerometer using Three Phase Sensing Approach

The MEMS accelerometers play a pivotal role in the medical, automotive and smart phones industries. In this paper, a new approach to measure the acceleration by the capacitive MEMS accelerometer using the finite element analysis method is studied. This novel mechanism, which called the three-phase method, enhances the sensitivity of the accelerometer in comparison to the conventional two-phase measurement method and is capable of eliminating offsets and effects of manufacturing tolerances. In the two-phase method, there are generally only two capacitances between the rotor and stator electrodes of the accelerometer. These capacitors vary by applying the acceleration and relative displacement of the electrodes with a phase difference of 180. On the contrary, in the three-phase method, six variable capacitances vary with the phase difference of 120. In the latter approach, the sensitivity is twice of the two-phase approach, and also by adjusting the electrical phase angle, the manufacturing tolerances can be eliminated. The frequency response was investigated in this paper, which shows the ultra-low sensitivity of this accelerometer to the unwanted cross-sectional and rotational accelerations.