Ju Chunge, Li Xiang, Zou Junjun, Wei Qi, Zhou Bin, Zhang Rong
Department of Precision Instruments, Tsinghua University, Beijing 10084, China.
Sensors (Basel). 2020 Apr 1;20(7):1973. doi: 10.3390/s20071973.
This paper presents the design and implementation of an auto-tuning continuous-time bandpass sigma-delta (ΣΔ) modulator for micro-electromechchanical systems (MEMS) gyroscope readout systems. Its notch frequency can well match the input signal frequency by adding a signal observation to the traditional ΣΔ modulator. The filter of the observation adopts the same architecture as that of the traditional ΣΔ modulator, allowing the two filters to have the same response to input signal change, which is converted into a control voltage on metal-oxide semiconductor (MOS) resistance in the filters. The automatic tuning not only works to solve the mismatch problem caused by process error and temperature variation, but can also be applied to the interface circuit of gyroscopes with different resonant frequencies. The circuit is implemented in a 0.18-μm complementary metal-oxide semiconductor (CMOS) process with a core area of 2.4 mm. The improved modulator achieves a dynamic range of 106 dB, a noise floor below 120 dB and a maximum signal-to-noise and distortion ratio (SNDR) of 86.4 dB. The tuning capability of the chip is relatively stable under input signals from 6 to 15 kHz at temperatures ranging from -45 to 60 °C.
本文介绍了一种用于微机电系统（MEMS）陀螺仪读出系统的自动调谐连续时间带通sigma-delta（ΣΔ）调制器的设计与实现。通过在传统ΣΔ调制器中增加信号观测，其陷波频率能够很好地匹配输入信号频率。观测滤波器采用与传统ΣΔ调制器相同的架构，使得两个滤波器对输入信号变化具有相同的响应，该响应被转换为滤波器中金属氧化物半导体（MOS）电阻上的控制电压。自动调谐不仅能解决由工艺误差和温度变化引起的失配问题，还可应用于具有不同谐振频率的陀螺仪接口电路。该电路采用0.18μm互补金属氧化物半导体（CMOS）工艺实现，核心面积为2.4平方毫米。改进后的调制器实现了106dB的动态范围、低于120dB的本底噪声以及86.4dB的最大信噪比和失真比（SNDR）。在温度范围为-45至60°C、输入信号频率为6至15kHz的情况下，芯片的调谐能力相对稳定。
