Research On Processing Method Of Force Monitoring Signal In Metal Slit Based On SAW Device

In a monitoring system based on SAW device,there is a wave trough in resonance curve of frequency domain.When the environmental parameters change,the resonance frequency of the SAW sensor will change and the curve trough will shift.Therefore,this trough can be searched directly to get its corresponding frequency,which is used to measure the surrounding environmental parameters.However,the existence of noise decreases the stability of sensor resonance frequency which is calculated out.In order to improve the accuracy of environmental monitoring parameters,it is necessary to study signal processing methods based on research of the monitoring system.In this paper,considering the force monitoring system in metal slit based on SAW device,the signal processing method has been studied.The main work are as follows:1.The model of force monitoring system based on SAW device is built.The characteristic parameters of microwave network and the basic connection modes between networks are shown.The basic principles and working characteristics of SAW sensor,micro-strip transmission line,and antenna in the system are exhibited.According to the working characteristics and the cascade connection mode between every two units,the equivalent circuit model having two resonant working modes is established for the monitoring system.And then the influence of the parameters on the model curve is analyzed.2.The signal processing simulation experiment is carried out by using polynomial fitting method and parameter fitting method based on resonance model.By analyzing the frequency offsets of the minimum point and the resonance frequency point of the model,it is shown that the minimum point and the resonance frequency point can be used as the characteristic points of data processing even though the two points are different.The system response signal is simulated based on the equivalent circuit model having two resonant working modes.Then,the signal is processed respectively by using polynomial fitting method and parameter fitting method based on model,and the data range of data processing using the two methods is selected.3.The stability experiment of minimum point and resonance frequency simulation calculated out is carried out by using polynomial fitting method and parameter fitting method based on resonance model.By simulating certain SNR response signal,the polynomial fitting method is used in the selected ranges of data to calculate the minimum and its stability.Similarly,the parameter fitting method based on resonance model is used in the optimal ranges of data to calculate the resonance frequency and its stability.The results show that using the two methods the stability of resonance frequency may be improved under certain conditions,compared to the method of directly searching for minimum point.4.The experiment of loading and unloading force based on the SAW device is carried out and the data is processed.The experiment of loading and unloading force on SAW sensor chip is carried out.By using polynomial fitting method and parameter fitting method based on model respectively,the experimental data are processed and the resonance frequency is calculated.The results show that resonance frequency stability has been improved by using the two methods,compared to the method of directly searching for minimum point.Finally,the variation regularity between the force and the resonance frequency of the SAW sensor is analyzed.