Self-Clocking Electro-Mechanical Sigma-Delta Modulator Quadrature Error Cancellation for MEMS Gyroscope

This paper presents a novel electromechanical sigma-delta modulator (EM-ΣΔM) closed-loop quadrature error cancellation technique for the sense mode of a MEMS vibratory gyroscope. The interface circuit system adopts a quadrature sigma-delta modulator structure, which allows in-phase and quadrature decomposition to efficiently realize noise shaping and quadrature error cancellation. Experimental results demonstrate that the proposed quadrature sigma-delta modulator (Q-ΣΔM) control loop results in better noise and bias drift performance when compared with an EM-ΣΔM single-loop architecture. Measurement results showed that the proposed quadrature EM-ΣΔM gyroscope achieved -80dB quadrature error cancellation within a bandwidth of 64Hz, and an approximately 5.5-fold improvement in bias instability (decreasing the bias instability from 5°/h to 0.9°/h), compared to the same gyroscope operating in a single-loop EM-ΣΔM.