Test and evaluation of a silicon resonant accelerometer implemented in SOI technology

This paper describes a silicon resonant accelerometer implemented in SOI technology. With fully differential design and micro-lever system, the accelerometer achieves a sensitivity of 82Hz/g with a nominal frequency of 30 kHz. The MEMS device is placed in a ceramic vacuum package, so gets a quality factor nearly 1e5. Readout circuit is also introduced which includes two differential oscillators and a double channel frequency measure circuit. A novel differential capacitance sense circuit employing high frequency carrier and diodes ring is used to avoid driving signal feed through. And a 90° phase shifter and AAC (automatic amplitude control) are also used to maintain phase and amplitude balance. The frequency measurement circuit is based on all digital multi-bit PLL (phase lock loop) technology, which is implemented by 18bit ADC and FPGA, the accuracy of each channel is better than 1mHz. The complete resonant accelerometer achieves 13.5μg/ √ Hz resolution and 3.6μg bias stability.