A Nearing-Free Constrained Architecture for Systematic Design of Electromechanical Sigma-Delta Modulator

An electromechanical sigma-delta modulator (EMSDM) is a good choice for inertial sensors to achieve high performance. However, there are few systematic methodologies to design it, due to a lack of degrees-of-freedom for implementing an arbitrary noise transfer function (NTF) in many EMSDM architectures. Previous work presented an unconstrained architecture to systematically design the EMSDM, enabling arbitrary placement of NTF poles, but NTF zeros were still constrained. Yet, the placement of the NTF zeros significantly impacts on the EMSDM noise-shaping performance. This paper proposes a nearing-free constrained architecture to address this issue. Based on this architecture, a simplified systematic design methodology for the EMSDM is demonstrated by using a capacitive MEMS accelerometer as an example. Simulation and experimental results validate that the novel architecture EMSDM accelerometer exhibits superior noise performance compared to the previously proposed unconstrained architecture EMSDM accelerometer. Furthermore, the advantages and disadvantages of the novel architecture are discussed.