Based On A Sigma-delta Modulation Digital Feedback Control System Design

The force balancing capacitive micro-accelerometers is particularly attractive compared to other inertia sensors at present. Sigma - delta modulation has become a popular technique in designing micro-accelerometers in foreign to restraint noise and enhance the system performance. Presently, micro-accelerometers using sigma-delta modulation is only on the researching stage although the prototypes has been made in the laboratory, and only little research in this domain has been reported in domestic, therefore it is promising to study this system.A new micro-accelerometer was designed using ∑-△ modulation in this article. Continuous-time model was transformed to discrete-time based on the IIR method. The linear quantizer linear model was established using the LMS method. By the analysis of the system character simulation using Matlab we can know that the micro-accelerometer system is a low pass system and it has linear phase characteristic approximately in the low frequency band (the accelerometer response frequency band). The simulation result also displayed that the second order noise shaping was performed in this system which made the noise transfer to high frequency band.Through the simulation of the output response of the sine acceleration input using Matlab/Simulink we see that the output follows the input approximately and the output signal is nearly a continuous signal because sampling frequency is very high.The result show that the method of designing micro-accelerometers using ∑-△ modulation is feasible and it can be the foundation of feather study.