Study On Multi-channel Surface Acoustic Wave Filter

Surface acoustic wave filter is the key component of small and portable mobile communication terminal,which plays great role in effectively reducing the terminal equipment volume,enhancing the anti-jamming ability of the terminal,improving the receiver sensitivity and optimizing of communication channel and other aspects.With the increasing attention to the mobile communication terminal with the requirement of the multi-network and multi-channel function,it is practically important to develop a small multi-channel surface acoustic wave filter.As for the multi-channel filtering method,traditionally individual multiple filters are packaged together or filters be encapsulated in a shell to realize the multi-channel function.However,the chip size in the two methods is relatively large,of poor stability and not suitable for radio frequency system.In view of the deficiency of technology,this paper provides a single chip which can realize multi-channel filtering,which not only realize the characteristics of multi-pass filter,but also has the characteristics of small size,simple circuit connection.The main contents of this paper are as follows:1?First of all,the research background,previous studies at home and abroad of surface acoustic wave devices are briefly described.Secondly,the thesis introduces the key structure of the surface acoustic wave device in detail,and points out the main factors that affect the work of the transducer.Last but not the least,the design method of surface acoustic wave filter and multi-channel surface acoustic wave filter is introduced,which lays the theoretical foundation for the design of surface acoustic wave devices.2 ? Design of surface acoustic wave filter for ISM band 433MHz: Based on surface acoustic wave devices of all kinds of model,surface acoustic wave filter focuses on using finite-element multiphysics simulation tool COMSOL Multiphysics to design and simulate a ISM band 433 MHz,in order to optimize the phenomenon of insertion loss that is too large,the frequency offset in the simulation the absorbing device on the substrate at both ends,sound change the pore size change,interdigital width,and resonant gate method,the filter insertion loss of 2dB,to meet the design requirements.3?Design of WiFi dual channel surface acoustic wave filter: The thesis combines three schemes: multi filter in parallel,the reflection grating,the structure symmetry and obtains each parameter in the COMSOL simulation.In order to optimize the performance,the bottom depth of cross horizontal slotted substrate scheme,and get inspiration from the traditional structure of surface acoustic wave sensor,the multilayer composite structure applied to surface acoustic wave filter,the two layer IDT/LiNbO3 structure instead of the traditional IDT/LiNbO3/ diamond three layer structure,this structure with LiNbO3 high electromechanical coupling coefficient and wave velocity of large diamond the two advantages,for 2.4G and 5G band filter insertion loss reduction of 1.2dB and 1.1dB.So that the two channels of the dual channel insertion loss of 2.6dB and 3.1dB respectively.Thus,the design meets the basic requirements of device applications.