Optimization Of Measurement And Control Circuit For Silicon Oscillating Accelerometer

Silicon oscillating accelerometer(SOA)is a micro-inertial device fabricated by MEMS technology to detect the acceleration by sensing the change of the frequency of the resonator.SOA has the characteristics of small size,low cost and wide dynamic range,with a wide application prospect in smart inertial navigation system.The measurement and control circuit is a crucial factor in determining the critical performance of SOA.In this paper,we optimized the measurement and control circuit of the SOA,reducing its noise and power consumption.Firstly,the system-level phase noise model of SOA is established.And the relationship of noise source parameters and phase noise is obtained.The influence mechanism of noise source on phase noise is revealed,which provides the guidelines for low noise and low power optimal design of the measurement and control circuit.Secondly,we optimized the design of the closed-loop oscillating circuit.The defects of AGC closed-loop oscillating circuit are summarized,and a comparator amplitude control circuit and two-stage integral interface circuit are proposed,which simplifies the circuit structure and reduces its noise floor.The prototype was fabricated and tested.The power consumption was reduced from 1.2W to 50mW,the bias stability was improved from 22.9μg to 13.3μg,and the bias instability was improved from 9.3μg to 4.3μg.Thirdly,we proposed a new frequency measurement circuit.Based on the analysis of commonly used frequency measurement methods,a frequency measurement method based on counter with first-order noise shaping is proposed.Under the premise of ensuring accuracy,the reference clock frequency is reduced from 300MHz to 10MHz.The frequency measurement algorithms were written in the Verilog language and implemented on the FPGA.Experimental results show that the frequency accuracy is 0.4528mHz.Finally,according to the IEEE test standards we did a performance test on SOA.The results showed that the bias stability(1σ)reached 12.8μg,the stability of 1g(1σ)reached 14.5μg and the stability of scale factor was 24.2ppm.