Silicon Micromachined Gyro Anti-parasitic Capacitance Interference Interface Circuit And Digital Measurement And Control Circuit Design

This thesis focuses on the research of silicon microgyroscope developed by NJUST I-MEMS group.Low noise and anti-interference interface circuit and digital measurement and control system are designed.The main work is as follows:Firstly,the mechanical structure of silicon microgyroscope and the principle of its measurement and control circuit are introduced,the working mechanism of driving loop and detection are deduced,the error analysis is carried out.The topology of parasitic capacitance is established,and the parasitic capacitance is measured.Based on the measurement results,the problems caused by parasitic capacitance are analyzed and the solutions are put forward.Based on the requirements of gyro performance and the study of parasitic capacitance,the design objective of electromechanical interface circuit is proposed,which is low noise and anti-interference.In order to overcome the shortage of transimpedance interface,three kinds of improved interface circuits are proposed:T-network interface,Integral-differential interface,two cascaded integral interface.The principle of three kinds of interface circuits is introduced,and the noise performance and anti-interference performance are simulated and compared.Two cascaded integral interface shows better overall performance according to simulation.The test results show that its equivalent input current noise is 24.3fA/?Hz(@6.4KHz),with 20.6M ?-? gain and phase error of 0.66°.After adopting the newly proposed front-end,the gyroscope's demodulation phase error is only 0.44°.More importantly,it is not affected by the input stray capacitance effect,and reject high frequency oscillation.Then,the hardware design of digital measurement and control circuit for gyro is presented.Using FPGA as the digital platform.The signal integrity is ensured by reasonable design of PCB.Test results show that the noise floor of both analog and digital parts are below deign target,and the performance of the interface circuit is therefore ensured.Finally,the gyroscope is tested using the newly designed circuit.It's scale factor is 23.5mV/°/s with nonlinearity of 339.7ppm.The angle random walk is 0.011°/?h,and the bias instability is 0.4°/h.The corresponding 1? bias stability is 0.78°/h when the output rate is 10Hz.The performance meets the requirements of tactical gyro.