小型化硅微谐振式加速度计的实现与性能测试

Implementation and measurement of a miniaturized silicon resonant accelerometer

设计了一款由微机电系统和专用集成电路构成的小型化硅微谐振式加速度计。该加速度计采用80μm厚SOI工艺加工微机电系统(MEMS)结构,采取真空封装技术降低结构噪声。首先,采用振荡信号作为自动增益控制电路中斩波器的控制信号,降低了闪变噪声且不会引入额外的功耗。其次,使用线性区工作的乘法器取代传统的吉尔伯特单元,通过大幅降低系统总体供电电压来降低功耗。最后,采用复位计数器进行频率数字转换,在所关心的带宽内抑制量化噪声。实验显示:该加速度计在达到±30 g线性量程的前提下,实现了2.5μg/√Hz的分辨率和1μg的零偏不稳定度。此外,为了减小电路自身发热引起的温度漂移,该样机的功耗被控制在3.5mW以内,系统集成后的尺寸约为45mm×30mm×20mm。基于所述技术,系统在体积、功耗和性能方面均有较大的提升。

A miniaturized Silicon Resonant Accelerometer（SRA） consisting of a MEMS （Micro-electro- mechanical System） and an ASIC（Application Specific Integrated Circuit） readout circuit is designed. The MEMS sensor is fabricated by an 80 μm thick SOI process and the noise in the ASIC is reduced by a series of vacuum packaging technologies. Firstly, a vibration signal is used as the control signal of a chopper in automatic gain control circuit to reduce the flicker noise and extra power consumption. Then, a multiplier in the linear area multiplier is used to replace the traditional Gilbert unit to reduce power consumption by sharply reducing system power supply voltage. Finally, a reset counter is taken in digital frequency conversion to inhibit quantization noise in the concerned bandwidth. The ex- periments show that the proposed SRA achieves sub-μg bias instability and 2.5 μg/√Hz velocity ran- dom walk within ＋30 g full scale. Moreover, to reduce the temperature drifting due to self heating, the power consumption of the SRA has been carefully limited under 3.5 mW. After integration, theentire prototype occupies a space of 45 mm× 30 mm× 20 mm. It is characterized by high performance, low power and good miniaturization.