System-Theoretical Analysis of Analog-CDMA Applied to Mixed-Signal Readout Interfaces for MEMS Gyroscopes

This paper presents a novel architecture for low noise mixed-signal readout systems for 3-axes micromachined gyroscopes; the proposed solution experiments an innovative readout technique based on analog-CDMA (Code Division Multiple Access) in order to extremely simplify the analog front-end which can be based on a single charge amplifier. Many family codes have been considered in order to find the best solution between performance and complexity. As a result, Walsh codes have been finally selected. Simulations prove the effectiveness of this technique in processing all the required gyro signals: the three sensing signals and one primary signal for keeping the sensor in resonance. The proposed solution can achieve good reduction of silicon area and current consumption in the analog section with reference to other multiplexing schemes. Keywords- CDMA, capacitive gyroscope, mixed-signal readout interfaces, MEMS, analog front-end, Walsh codes