Design Of Ultra-wideband Radio Frequency Front End Surface Acoustic Wave Filters

Because of the advantages such as simple structure,excellent performance,low insertion loss,low cost,small size and mass production,filters based on Surface Acoustic Wave(SAW)technology have attracted more and more attention and have been widely used in the radio frequency(RF)front end of electric devices,especially in the RF front end of mobile phone.With the emergence of the new communication protocol4G Long Tern Evolution(LTE)communication standard,the filters in the Radio Frequency(RF)front end of mobile phone requires ultra-wideband to satisfy the demand of LTE standard.The research on the ultra-wideband RF front end SAW filters has become a hot topic.Since the circuit of the filter consists of resonators,and the band of SAW resonators mainly depends on the electromechanical coupling factor K~2 of the piezoelectric materials in the resonators,this paper propose the research on two new types of piezoelectric materials with higher K~2 to improve the band of SAW filters:Lithium Niobate on insulator LNOI and relaxor ferroelectric single crystal PIMNT.First,a one-port SAW resonator simulation model is built by using Finite Element Method(FEM)simulation software COMSOL to research the SAW performance of the SAW resonators with different materials and thickness of electrodes,piezoelectric materials and Euler angle.The resonators can be fabricated by the experiment and the experiment results are compared with the simulation ones.Then according to the performance of SAW resonators,we design the SAW filter circuits based on ladder type filter circuits.By using circuit simulation software QUCS to simulate the model of the filter circuit,the performance of filters can be achieved by adjusting the parameters of the resonators and the circuits of the filtes.These research results can provide enough theoretical basis for the design and preparation of the ultra-wideband resonators and filters.