Research On Techniques Of Coating FBAR Filter For 5G Communication Sub-6GHz Band

With the rapid development of modern communication technology,mobile communication system has proposed development goals such as faster transmission rate,higher spectrum utilization,more equipment access and lower delay,which put forward higher demand for the various components.Among them,the traditional SAW filter,whicn working frequency is much more lower than the demand,is difficult to meet the high frequency development trend of communication system because of its own structural limitations.Therefore,people began to search new scheme of filter.The filter based on thin film bulk acoustic resonator(FBAR)has attracted attention and become widely acceptable because of its high Q value,small size,low power consumption,good reliability and strong stability.Moreover,the fabrication process of FBAR filter is compatible so that it has great potential in integration.Therefore,FBAR filter has become a research hotspot in the field of filter.In this paper,the FBAR filter will be theoretically analyzed,modeled and simulated,and finally optimized by actual preparation and comparison theory analysis.Firstly,this thesis introduces the basic structure and working principle of FBAR filter based on piezoelectric effect.Then,the basic structure and working principle of the FBAR filter are introduced based on the resonator.By comparing the advantages and disadvantages of different structures,the cavity structure of the resonator and the step structure of the filter are established respectively at the last.Then,based on the working principle of FBAR resonator,combined with electrical and mechanical analysis,the impedance model of FBAR resonator is obtained,and the equivalent circuit model is deduced on the basis of the impedance model.Through the impedance model,the parameters of the resonator are simulated and analyzed,and the film material and single parameters of the FBAR filter are established according to the physical properties of the material.Based on the impedance analysis of the resonator and the design index of the filter,the circuit simulation and optimization of the filter are carried out.Finally,the structure parameters of the FBAR filter are established.Finally,the FBAR filter was prepared after optimizing the single-step coating process.By comparing the measured results with the simulation results,the optimization scheme for bandwidth and central frequency is proposed and verified.Finally,according to the optimized scheme,the filter sample is reproduced.Its 3dB bandwidth is 160MHz,passband insertion loss is less than 3.5dB,out-of-band suppression is more than 30dB,and echo loss is more than 12dB,which meets the application requirements of 5G communication sub-6GHz band.