Sigma-delta modulator based control systems for MEMS gyroscopes

In this paper a review is presented about recent developments of using sigma-delta modulator (SDM) control systems for micromachined, capacitive vibratory rate MEMS gyroscopes. The design choices, their benefits and disadvantages are briefly discussed. As the most promising control system, a higher order, band-pass SDM is identified since it achieves high quantization noise shaping at a relatively low sampling frequency, in addition to the normal closed loop, force feedback control advantages such as improved bandwidth, linearity and dynamic range. Previous work applied this type of control system to gyroscopes with a relatively small proof mass. Here, results are presented applying the approach to a comparatively large, bulk-micromachined gyroscope sensing element, which has the potential to result in a high performance sensor. System level simulations are presented illustrating the benefits of the approach.