Research On Closed-loop Detection System Of Silicon Microresonance Pressure Sensor

Silicon micro-resonance pressure sensors are widely used in aviation,aerospace,military,civil and other fields.Silicon microresonant pressure sensors are an integral part of a variety of sensing systems due to their accuracy,which is almost in line with all current pressure sensors.Due to its weak output signal,accurate detection of the output signal becomes a major difficulty in the application of silicon microresonant pressure sensors.Therefore,the establishment of a reasonable and efficient detection system has become the focus of research on silicon micro-resonant pressure sensors,while the focus of the detection system is to detect the resonant frequency of silicon micro-resonant pressure sensors.There are various methods for detecting the resonant frequency of a resonator,and the phase-locked loop technology is relatively mature.Therefore,this paper first uses the phase-locked loop technology to construct an analog phase-locked loop closed-loop detection system to detect the resonant frequency of a silicon microresonant pressure sensor.The preamplifier module,signal processing module,phase-locked loop module and excitation module in the analog closed-loop detection system are designed,matched and simulated respectively.Finally,the actual measurement is performed on the PCB.The measured result shows that the main resonant frequency is 81.72 kHz,the resonance peak is 6dBm.Aiming at the problems of the peak of the resonant frequency exposed by the analog closed-loop detection system and the existence of the sub-resonance frequency,this paper uses the all-digital phase-locked loop instead of the analog phase-locked loop circuit to improve the analog closed-loop detection system and build a digital closedloop detection system.The digital phase detector,digital loop filter and numerically controlled oscillator of the all-digital phase-locked loop are simulated on the Quartus software respectively,and the hardware is measured on the FPGA.The measured results show the resonance peak at the main resonant frequency.Compared with the analog closed-loop detection system,the 8dBm is improved,but the sub-resonance frequency phenomenon still exists.In view of the still existing sub-resonant frequency phenomenon,considering that the phase-locked loop technology is based on the silicon resonant pressure sensor as a linear model,the linear resonant region of the silicon resonant pressure sensor is much smaller than the nonlinear working area,and is maintained.It is too difficult for a micromechanical system in complex conditions in a linear working area.In this paper,a nonlinear model of silicon resonant pressure sensor is established.The nonlinear model of the sensor is simulated by Matlab and compared with the linear model.The results show that the nonlinear model is more consistent with the actual working state of the resonator.On this basis,the closed-loop detection system based on nonlinear model phase-locked loop is first established and simulated.The results show that the phase-locked loop technique can not eliminate the linearity of the sub-resonance frequency,and then try to establish a linear feedback controller to solve the linear feedback.The parameters are constructed based on a linear feedback closed-loop detection system,and the simulation results show that the sub-resonance frequency phenomenon is eliminated.