MEMS based oscillator incorporating a displacement sensor

Abstract

This paper outlines the design and performance of an oscillator that incorporates a new type of MEMS resonator. The MEMS resonator is similar in design to many other electrostatically actuated MEMS resonators in the literature. However, the novel aspect of the resonator is the use of electrothermal displacement sensors to capture its motion. Due to the high resolution of these sensors compared to other sensor technologies used in MEMS, there is the potential for oscillators using this type of resonators to have good phase noise performance. However, due to the low bandwidth of the sensors, only low frequency oscillators can be fabricated with this technology. Despite the differences in dynamics between typical electrostatic or piezoelectric transduced resonators, the oscillator topology using a feedback gain was found to be robust at sustaining oscillations. This was due to the interaction between the dynamics of the capacitive feedthrough and the mechanical system in the device. The frequency of the fabricated oscillator is 8844 Hz.