Resonant MEMS sensors are commonly used for sensing pressure, mass, force, strain, and acceleration. Resonant readout is particularly attractive for piezoelectric sensors, since it is the only method that allows measurement of static or slowly-varying quantities. Fundamentally, resonant readout relies on a fixed dependence between the quantity to be measured and the resonant frequency of a mechanical structure. However, the resonant frequency is generally also a strong function of several unwanted variables, including temperature, fabrication variability, and packaging stress. One way to remove these variables from the measurement is to use differential readout, where two matched resonators are configured such that they have unequal sensitivities to the measurand, but equal sensitivity to outside disturbances. This requires the readout interface to simultaneously measure both resonant frequencies and perform appropriate subtraction and scaling. This project aims to create high-performance circuits for differential sensor readout, with an eventual goal of full monolithic integration.
Project end date: 08/18/11