| Silicon micro-resonance pressure sensor is the MEMS pressure sensor with the highest accuracy at present,and has become the focus and hotspot of development and research in recent years.In this thesis,the harmonic oscillator parameter test method,low power self-excitation drive circuit and high precision frequency measurement algorithm of silicon micro-resonant pressure sensor are studied.The main contents are as follows:（1）The overall design of silicon micro-resonant pressure sensor and its dynamic linear model are briefly introduced.The principle of electrostatic driving and piezoresistive detection of the resonator are introduced.The closed-loop self-oscillation principle of the pressure sensor is analyzed and the block diagram of closed-loop self-oscillation system is established.（2）An improved method is proposed to improve the precision and efficiency of measuring the resonant frequency and quality factor of silicon micro-resonant pressure sensor.Firstly,the time-frequency domain analysis of the excitation signal is carried out,and the frequency domain characteristics of the response signal are obtained by combining the dynamic model of the resonator.Secondly,for the resonant frequency test,the triangle method and the triangle method based on hanning window are analyzed.For the quality factor test,the half-power bandwidth method is analyzed and the Lorentz fitting method is proposed.Finally,through simulation verification and comparison,it is proposed that the above method can effectively improve the testing accuracy and efficiency by comparing the testing quality factor between the hanning window triangle method and lorentz fitting method.（3）Improved the low power consumption of the closed-loop self-excited driving circuit of the resonant pressure sensor from three aspects of power supply,chip replacement and circuit structure.The double power supply is changed to single power supply,the lower power consumption of the op amp chip and the voltage regulator chip are used to simplify the circuit structure of the AGC amplitude control circuit,the closed-loop self-excitation system model is established,the equilibrium point is solved,the stability condition is analyzed and verified in Simulink.Finally,the hardware circuit is debugged and the circuit performance and power consumption before and after the improvement are compared to verify the effectiveness of the low-power improvement of the circuit in this paper.（4）The frequency detection technology of the existing silicon micro-resonance pressure sensor is optimized.Firstly,the multi-period synchronous counting method and phase shift clock counting method are introduced.Secondly,the continuous time stamp counting method is discussed,and its principle and error are analyzed.Finally,the algorithm is implemented by FPGA,and the effectiveness of this method in improving the accuracy of frequency measurement is verified through experiments and comparison with the results of common frequency measurement methods.（5）The above results are applied to the silicon micro-resonant pressure sensor core respectively for the open-loop resonant oscillator parameter test experiment and the performance test of the whole system composed of closed-loop self-excited driving circuit and frequency measuring circuit.The experimental results show that the error between the resonance frequency and the mean value is less than 0.1Hz,and the relative error between the quality factor and the mean value is less than 10%.The closed-loop test experiment is divided into noise and frequency drift test for the measurement and control circuit at low temperature（-40℃）,normal temperature（21.8℃）and high temperature（70℃）.The frequency drift is1.6Hz and 0.9Hz respectively,and the output frequency noise is 7.899×10-8 and 2.818×10-8respectively under the condition of cold start at room temperature and pressure before and after improvement.The work carried out in this thesis provides theoretical support and practical measurement and control circuit scheme for the development of silicon micro-resonance pressure sensor system,and lays a foundation for further product development. |
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