System Design of Second-Order Sigma-Delta Micromachined Accelerometer

Previous researches indicate that a first-order sigma-delta micromachined accelerometer can hardly achieve a high dynamic rang at an acceptable oversampling rate. We have designed a second-order sigma-delta modulator, which includes two integrators and three gains, for micromachined accelerometers. By simulation in Matlab, we have found that the system gain of the second-order sigma-delta micromachined accelerometer is determined by the electrostatic force-feedback loop gain. Moreover we have found methods to regulate the climbing time of the step response of the second-order sigma-delta micromachined accelerometer. Noise simulations show that the dynamic rang of the second-order sigma-delta accelerometer is 35.4dB higher than that of the first-order one at the same oversampling rate