Research On Wireless Sensing Technology Based On RF MEMS Piezoelectric Resonator

The rapid development of micromachining technology is a powerful driving force for the development of the integrated circuit industry,which can realize various microelectromechanical systems(MEMS)devices that are easy to integrate with ICs.Among them,MEMS resonators are widely used in sensors,filters and oscillators.Among various MEMS resonators,thin-film-on-silicon(TPoS)resonators have the advantages of small size,low power consumption,high electromechanical transduction efficiency,and the realization of single-chip multi-devices.Therefore,TPoS resonator technology has received extensive attention in the field of integrated,multifunctional,and high-performance microsensors.However,traditional miniature sensors based on TPoS resonators use wired sensing,which leads to the problems of poor portability and limited application scenarios.In recent years,wireless sensing technology for TPoS resonant sensors has received more and more attention from researchers.This technology combines TPoS resonators and near-field coupling coils to form wireless sensors,which has broad application prospects.However,this technology also has the problems of weak sensing signal and short sensing distance.Aiming at the above problems,this thesis studies a wireless sensor based on TPoS disc resonator.Through the optimal design of the resonator coupling coil,the signal strength of the wireless sensor is improved.The specific research contents are as follows:First,the different mechanical vibration modes of TPoS disk resonators are studied in this thesis,and then the vibration modes of the resonators suitable for wireless sensing applications are found.By comparing the performance of different vibration modes,two vibration modes,the circular mode and the button mode,are determined.Among them,the electromechanical conversion efficiency of the circular vibration mode is higher,and the quality factor of the button mode is higher.Secondly,this thesis designs a wireless temperature sensor scheme based on a TPoS disc resonator and a coupled coil,and uses the sensor's reflection coefficient S₁₁ as an electrical parameter to monitor the ambient temperature.On the one hand,the S₁₁parameter is used to transmit the frequency information of the resonator,that is,the ambient temperature change information;on the other hand,the S₁₁ parameter and the Smith chart are used to complete the impedance matching between the resonator and the coil,so as to achieve the goal of enhancing the strength of the wireless sensor signal.Finally,the designed wireless sensor temperature sensor is tested and its test performance is analyzed.Specifically,this thesis tests the frequency temperature coefficients of different vibration modes in wired and wireless connection states.The wired frequency temperature coefficient of the button mode is-28.6 ppm/?,and the wireless frequency temperature coefficient is-42 ppm/?;the wired frequency temperature coefficient of the circumferential mode is-30.2 ppm/?,and the wireless frequency temperature coefficient is-39.4 ppm/?.In addition,this thesis analyzes the wireless sensing signal strength of different vibration modes when the sensing distance is fixed.The test results show that the wireless sensing strength of the circular mode is better than that of the button mode.