Research On Surface Acoustic Wave Filter

With the advent of 5G era,terminal products need to support more and more frequency bands,so the demand for filters is increasing.Surface acoustic wave(SAW)filters are widely used in various communication systems and have the characteristics of small size,light weight,and strong anti-interference ability.This thesis focuses on the industrial product design of SAW technology,and makes research and innovation in COM model,SAW filter and SAW duplexer.The main contents are as follows:1.This thesis expounds the modeling method of COM model,applies it to ADS platform and encapsulates it into PDK model library.The COM parameters are expanded to enhance the representation ability of the model in the wide-band range.Finally,the COM model simulation results are compared with the FEM/BEM calculation results and the measured results,and a good agreement is obtained.2.Using the above PDK model library,two broadband SAW filters are designed.The first method is to set reflection gates between the IDT of DMS filter to obtain a new resonance point.It is found that the phase is suitable for passband synthesis.Two DMS filters with non-overlapping passbands are connected in parallel.A broadband filter with center frequency of 785.5MHz and-3d B relative bandwidth of 8.27%is realized on normal SAW process and 42°Y-X Li Ta O₃ piezoelectric substrate.The filter layout size is1.13×0.85mm~2.The second method is to divide the pitchsize of the IDT of the DMS filter into a variety of pitchsize to differentiate the grid resonant frequency,so as to support the broadband.Under the same process conditions as above,the band 20+28 RX filter is realized.The passband range is 758MHz?821MHz,the edge loss is less than2.4d B,and the out of band suppression is-40d B.The filter layout size is 0.87×0.64mm~2.3.A high-performance Band-1 duplexer is designed,which combines LC resonance and suppression resonator to achieve-58d B isolation in Rx band and edge loss within2d B.The layout size of duplexer is 1.5×1.1mm~2.