Authors: E. Gaura and M. Kraft
Affilation: Coventry University, United Kingdom
Pages: 154 - 157
Keywords: Brownian noise, quantisation noise, micromachined accelerometers, sigma-delta modulator
This paper investigates the noise shaping properties of a sigma-delta modulator type control system applied to a micromachined accelerometer. Three noise sources are present in such an electromechanical closed loop system: mechanical noise due to Brownian motion, electronic noise introduced by the interface circuit due to thermal noise sources in the electronic devices and quantisation noise due to the analog to digital conversion process. It is well known that the sigma-delta modulator system shapes the quantisation noise in an advantageous way by attenuating it in the signalband. It is shown here that it also shapes the electronic noise favorably. However, this property is less pronounced. The Brownian noise remains unaffected in the signal band. With the outlined simulation procedures it is possible to predict the dominant noise contributions for different sampling frequencies of the sigma-delta control system and hence design an optimized control system.