The Research On Design And Synthesis Of FBAR Filter

The FBAR filters and duplexers can provide better filter performance,since the FBAR filter curve is steep with high isolation,the insertion loss is small,and can be adapt to higher frequency band.For the rapid development of 5G communications,requirements for better performance,higher frequency,and greater power capacity will be put forward for the performance of filters in the radio frequency front end of mobile terminals.Using FBAR filters as high-performance filters in the RF front-end will become a hot trend in the future.Therefore,FBAR-related modeling,simulation,design,and basic research on algorithms are particularly important for applications in the future.The subject of this thesis has carried out research on two major aspects of FBAR filter design and synthesis algorithm.In terms of FBAR filter design:1.The basic principle of the FBAR filter is firstly introduced.In order to accurately simulate the characteristics of the FBAR resonator,the commonly used Mason model is derived and the physical meaning of the Mason model is explained.Then,in response to the high-power capacity requirements of the FBAR filter applied to the transmitting port,with the help of the ANSYS simulation platform,a complete specific method for estimating the temperature distribution of the resonator on the FBAR filter given the input of a single tone high-power signal.And the method is applied to the subsequent engineering design to guide the design.2.According to the specific experimental design requirements,we simulated and designed a FBAR filter that works in the 4G Band 41 communication frequency band(2.535GHz-2.655GHz)with a bandwidth of 120 MHz.And according to the filter performance obtained by wafer test and packaging test,a detailed analysis was carried out to verify the accuracy of the model and design process.Finally,based on the design experience and temperature simulation under high power conditions,we further improved on the performance of the previous design,simulated and designed a high-performance FBAR filter that meets the requirements.In terms of FBAR filter synthesis method:1.This article introduces an acoustic wave filter synthesis method in detail.Starting from the required filter design target such as the target filter bandwidth,return loss,orders,and transmission zero points,the S-parameters of the specific target response can be obtained with the help of Chebyshev characteristics,and the dangling resonator model.Then the unknown parameters of ladder-type filter are obtained by connecting the suspension resonator model and simplifying process.The last step is to extract and restore the resonator parameters one by one according to the zero-point correspondence between the two.Finally,the ADS simulation verifies that the response obtained by the algorithm parameters is highly consistent with the target response.2.Based on the synthesis method,a method that can adjust the input phase by introducing external capacitors and inductors to eliminate the load effect and realize the synthesis of the acoustic duplexer with good performance is introduced.To improve the practicability of the algorithm,a specific method based on the effective electromechanical coupling coefficient parameters limitation and the correction of effective electromechanical coupling coefficient parameters obtained by the algorithm is further proposed.Finally,the current limitations of the algorithm are also analyzed.