Research On Measurement Technique For MEMS Accelerometer And Signal Process Circuit

A MEMS (Micro-Electro-Mechanical Systems) accelerometer is the core componentin the new generation of digital geophone system. It mainly consists of a MEMS sensor, areadout ASIC(Application Specified Integrated Circuit) and some other peripheral circuits.Due to its high sensitivity in detecting seismic waves and better performance over thetraditional geophone, MEMS accelerometers have been widely used in deep oil exploration.Concentrating on the tasks of the12th five-year projects plan, this report researches on testtechniques for MEMS accelerometer and its readout circuit ASIC with support of StateSci-tech Special Projects. Major research work and achievements are summarized asfollowing:(a) MEMS accelerometer calibration in gravity field: MEMS accelerometer iscalibrated in gravity field according to the criterion of minimizing the second-ordernonlinear coefficient. Static deviation, sensitivity and sensitivity temperature coefficientare measured as well.(b) MEMS accelerometer system noise floor measurement: system noise floor ofanalog closed-loop accelerometer and digital closed-loop accelerometer are measured,respectively. Noise amplification method is applied to improve the accuracy of themeasurement when measuring the system noise floor of analog closed-loop accelerometer(c) MEMS accelerometer reference voltage noise measurement and improvement:the noise contributors of digital accelerometer are analyzed. Through calculation andsimulation, it is confirmed that the MEMS’s Brownian noise and quantization noise are notthe main noise contributors. The thesis presents a novel scheme to measure ultra lowvoltage noise, and measures the reference voltage noise of ASIC. The system noise ofdigital accelerometer was measured again after reducing the reference voltage noise byfiltering. Thereafter the reference voltage noise was recognized as a main noise contributor. (d) Parameters measurement of loop filter: The thesis proposes a method to measurethe loop filter parameters. The parameters of PD(proportional and differential circuit) andintegrator were measured.The study results provide an important basis to improve the ASIC design of MEMSaccelerometer.