Fall 2010 IAB
September 15 to 17
Differential Readout of Resonant MEMS Sensors
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. We discuss and analyze several possible architectures for the readout interface and relevant performance limitations. We also discuss implications for sensor design.