Simulation of Micromachined Inertial Sensors with Higher-Order Single Loop Sigma-Delta Modulators

Y. Dong and M. Kraft
University of Southampton, UK

Keywords: sigma-delta modulators, micromachined inertial sensors, higher-order, noise transfer function

Abstract:
Micromachined capacitive inertial sensors incorporated in sigma-delta force-feedback loops have been proven to improve linearity, dynamic range and bandwidth, and also provide a direct digital output. Previous work mainly focused on using only the sensing element to form a 2nd-order single loop sigma-delta modulator. Therefore, the advantages of higher-order (4th-order and 5th-order) single loop electro-mechanical have not been explored, especially for inertial sensors that require higher Signal to Quantization Noise Ratio (SQNR), wide-band signal and low power dissipation. This paper presents architecture for higher-order single loop electro-mechanical with optimal stable coefficients that lead to better SQNR. Simulations show the maximum SQNR of 3rd-order, 4th-order and 5th-order is 88dB, 105dB and 122dB, respectively, using an Oversampling Ratio (OSR) of 256.

Nanotech 2004 Conference Technical Program Abstract