Authors: M. Kraft, W. Redman-White and M.E. Mokhtari
Affilation: University of Southampton, United Kingdom
Pages: 104 - 107
Keywords: inertial sensor, sigma-delta modulator, accelerometer, noise shaping
Micromachined inertial sensors are often incorporated in closed loop force feedback structures; a particularly advantageous approach is based upon the inclusion of the sensing element in a sigma-delta modulator (SDM) type control structure. The order of the SDM, and hence the noise shaping properties, is usually limited by the dynamics of the mechanical sensing element and may be insufficient for high performance applications. This paper presents a novel approach suggesting the use of a sigma-delta modulator with an order higher than the mechanical sensing element. This is achieved by a modified cascaded (or MASH) SDM loop architecture. A model of the electromechanical MASH is presented and the quantisation noise analysis is derived. Simulation results indicate nearly 30 dB increase in signal to quantisation noise ratio.