Research On Special Modal Vibration Characteristics Of Piezoelectric Resonators

Piezoelectric resonators are the core components of some sensors and drivers.These devices include piezoelectric gyroscopes,piezoelectric oscillators,piezoelectric filters,piezoelectric transformers,etc.they are widely used in the national economy and people's livelihood.For example,the temperature sensor based on the piezoelectric resonance uses the resonance frequency offset caused by the thermal sensitivity of the piezoelectric resonator,which has the characteristics of high resolution,low cost and low power consumption;the transformer based on the piezoelectric resonance can realize the function of boosting or reducing voltage,which has small volume,light weight,high power density,high efficiency and avoidance compared with the traditional electromagnetic transformer The tunable filter based on piezoelectric resonator technology can produce low power frequency tuning with high quality factor(Q value).Compared with the traditional circuit filter bank,it has the advantages of small number of parts,small size,light weight and low price.The piezoelectric resonator studied in this paper is based on the positive piezoelectric effect and the reverse piezoelectric effect.By applying voltage on the driving electrode,the resonator is in resonance state.At the same time,the working state of the resonator is sensed by detecting the electrical signal on the output electrode,and then the influence of the driving signal on the vibration characteristics of the piezoelectric resonator is studied.In this paper,the influence of driving signal on the vibration characteristics of piezoelectric resonator is studied,that is,the influence of driving signal on resonance frequency,output signal amplitude,phase and Q value.The research results provide theoretical reference for the circuit design and control of piezoelectric resonator.In this paper,the vibration characteristics of two special modes of rectangular piezoelectric resonators excited in the frequency range of 300 kHz-400 kHz are studied.The measurement and control system is divided into two parts: driving signal,analytical signal generating circuit and signal detection and demodulation circuit.In the driving signal and analytic signal generating circuit,STM32 embedded system is used to control DDS chip to generate two driving signals with adjustable frequency and phase and two vector analytic orthogonal signals.By writing frequency control words and phase control words to DDS chip,the micro solid mode piezoelectric resonators are driven by sweeping frequency;two analog and analytical voltage signals are sampled by STM32 built-in ADC,and then the amplitude and phase of the output signals of the micro solid mode piezoelectric resonators at each frequency point are calculated,and the resonance frequencies of the two special vibration modes of the micro solid mode piezoelectric resonators are obtained,Q value,amplitude and phase of output signal.The research content of this paper provides an effective technical way for driving and signal detection of micro solid mode piezoelectric resonators.Based on the analysis of the experimental results,it has the following findings:(1)The amplitude of the output signal has a good linear correlation with the amplitude of the driving voltage.(2)The Q value of resonator decreases with the increase of driving voltage in low frequency mode,which means that the driving voltage in low frequency mode will increase the internal energy loss of the oscillator;while in high frequency mode,when the driving voltage increases,the Q value will increase,and the increase of driving voltage will reduce the proportion of the internal energy loss of the oscillator in the total energy in unit period.(3)With the increase of the driving voltage,the phase of the output signal of the two modes remains constant at the resonance frequency point,that is to say,the phase of the output signal in the resonance state is almost not affected by the external conditions,which further verifies the effectiveness of tracking the resonance frequency of the piezoelectric resonator through the phase-locked technology.(4)In both modes,the resonant frequency decreases with the increase of the driving voltage,which is known as the softening effect.The softening effect is an important factor to be considered in the mode excitation process of piezoelectric resonators.