Drive and sense interface for gyroscopes based on bandpass sigma-delta modulators

This paper demonstrates a MEMS gyroscope system with extensive use of sigma-delta (ΣΔ) modulation in both, primary and secondary modes. The primary loop has a bandpass ΣΔ-digital-to-analog converter (DAC) driving the primary mass into resonance, which is implemented on a field programmable gate array (FPGA). With this strategy of shifting the primary oscillation control into the digital domain, the analog circuit complexity is enormously reduced. A continuous-time (CT) fourth-order micro-electro-mechanical ΣΔ Modulator (ΣΔM) incorporating the secondary resonator is used to convert the Coriolis rate signal into a bit stream. This ΣΔM is implemented on PCB performing an in-band noise (IBN) below -60 dBFS.