Abstract
Electromechanical multi stage noise shaping (MASH) sigma-delta modulator (Sigma Delta M) has the advantages of inherent stability, high dynamic range, and high overload input level compared with the single loop sigma-delta-modulator approach. In this paper, a fourth order electromechanical MASH is studied by Simulink modelling and hardware implementation using surface mount PCB technology. The accelerometer used in the study is fabricated using a Silicon on Insulator (SOI) wafer with a device layer thickness of 50 mu m, using a dicing free and dry release process. The experimental results confirm the concept of the MASH structure and show its potential as a closed loop interface concept fora high performance capacitive MEMS accelerometer. The 4th order MASH electromechanical Sigma Delta M system improves the performance of the 2nd order electromechanical Sigma Delta M by 20 dB, and shows a noise floor of -110 dB. Furthermore, the system is capable of handling an acceleration input of up to +/- 1.5 g. However, the MASH-Sigma Delta M is sensitive to the sensor and system parameters variation; it exhibited performance degradation of 10 dB, due to a leakage of the quantization noise to the input signal. (C) 2012 Elsevier B.V. All rights reserved.