Simulation Design Of Surface Acoustic Wave Filter Based On Lithium Niobate/Silicon Dioxide/Silicon Multilayered Structure

With the advent of the fifth generation（5G）mobile communication era,in order to meet the 5G communication technology’s requirements for higher communication transmission rates,denser connection density and greater communication data volume,it is required to be widely used in surface acoustic waves in the RF front-end（SAW）filter should have larger bandwidth,lower loss and higher frequency temperature stability.For this reason,the research on lithium niobate（LiNbO₃）/SiO₂/Simultilayer film structure SAW filter has become a hot spot in recent years.This is because lithium niobate single crystal film has a large electromechanical coupling coefficient（K²）,SiO₂ has a temperature coefficient of frequency（TCF）compensation characteristic,and the Sisubstrate has a lower cost.Therefore,through the optimization of SAW propagation characteristics in IDT/LiNbO₃/SiO₂/Simultilayer structure,Large K² and TCF close to zero can be obtained,which is of great significance for designing and manufacturing SAW filters with large bandwidth,low loss and high frequency temperature stability.In this paper,the design of SAW filter is divided into three steps.Firstly,optimizing the LiNbO₃ Euler angle.Secondly,optimizing the SAW propagation characteristics in the IDT/LiNbO₃/SiO₂/Simultilayer film structure.Finally,optimizing the design of IDT/LiNbO₃/SiO₂/Sistructure SAW single-ended resonator and SAW ladder filter.The specific research results are as follows:Using the finite element simulation software COMSOL Multiphysics to study the influence of the rotation angleθof YX-LiNbO₃ and the propagation angleψof XY-LiNbO₃ in the LiNbO₃/SiO₂/Sistructure on the propagation characteristics of SH-SAW,30°YX-LiNbO₃ and X（-10°）Y-LiNbO₃ makes SH-SAW have a large electro-mechanical coupling coefficient,while the electromechanical coupling coefficient of other modes is well suppressed.Using COMSOL,a 2.5-dimensional periodic model of IDT/LiNbO₃/SiO₂/Sistructure was established.Study and optimize the tangential IDT/X（-10°）Y-LiNbO₃/SiO₂/Siand IDT/30°YX-LiNbO₃/SiO₂/Sistructure in the LiNbO₃ film thickness,SiO₂ film thickness,electrode film thickness and metallization rate,And the influence of the electrode material on the phase velocity,electro-mechanical coupling coefficient and frequency temperature coefficient of SH-SAW.A systematic comparison of the two cut-type lithium niobates in the IDT/LiNbO₃/SiO₂/Sistructure shows that 30°YX-LiNbO₃ has a greater advantage,with K² reaching 39.36%and TCF as low as-10ppm/℃.Using COMSOL,a quasi-three-dimensional finite-length single-ended resonator model with IDT/YX-LiNbO₃/SiO₂/Sistructure was established,its admittance characteristics were calculated,and the influence of the number of reflection grids and the number of IDT fingers on its electrical characteristics was analyzed.The simulation results show that when the IDT is 150 pairs and the reflector is 25 pairs,the SH-SAW single-ended resonator has good performance.Finally,using the optimized SH-SAW single-ended resonator results,the parameters of the components of the MBVD equivalent model of the resonator are extracted.In ADS,the order of the SAW ladder filter and the resonator electrostatic capacitance C₀ are simulated and analyzed,and the center frequency is 1.85GHz,the bandwidth is 400MHz,the insertion loss is less than 2dB,and the out-of-band suppression is greater than 40dB.