Opportunities and Challenges in Using Modulated Electrostatic Softening in FM MEMS Accelerometers

This work advances the research on time-switched frequency-modulated (FM) accelerometers by presenting both a new device and a new measurement architecture. The sensor exploits nanopiezoresistive gauges to minimize the oscillator frequency noise down to sub-sub-10 $\mu $ g/ $\sqrt {\text {Hz}}$ equivalent acceleration density, while at the same time holding almost 100-g full-scale. The corresponding dynamic range is promising for several applications; however, this article also shows how the theoretical performance is affected by noise associated with a pair of modulating voltage waveforms, required by the specific working principle. Exploiting a digital generation of these waves and low-noise digital-to-analog converters (DACs), the effect is only partially mitigated. Nevertheless, the system experimentally reaches up to 65-g full-scale and holds as low as 30- $\mu $ g stability at almost 1000-s observation interval.