Research And Design Of Film Bulk Acoustic Wave Diplexer With High Power Capacity

As an important component of the RF front end,the performance of the duplexer directly affects the function of the system.In order to make the duplexer transmit signal strength more,the power amplifier is usual y needed at the transmitter front end of the transmitter.The power of the power amplifier is always large in some base stations with higher signal strength,so the power endurance of duplexer is very important.The power capacity of the traditional ceramic filter is very high,is often used in high power applications,but the dielectric filter is too large,and can not be integrated with IC technology,the field is very limited;another common surface acoustic wave filter,interdigital structure due to its limitations,in high frequency applications is limited.At the same time,the energy conversion mode on the surface of the substrate so that it cannot be used in high power environment.In this case,the bulk acoustic wave filter with high Q value,small volμme,high frequency and high power capacity is a solution to the high power capacity duplexer.In order to improve the power capacity of single film bulk acoustic resonator,the electrical and thermodynamic models of thin film bulk acoustic resonator are established by using Comsol Multiphysics finite element simulation software.The device is simulated and analyzed in detail for the thermodynamic performance of the film bulk acoustic resonator with different structures.It is found that the maximμm steady-state temperature and maximμm thermal stress of the SMR resonator are minimμm.At 0.1W,the maximμm steady-state temperature is about 30℃,and the maximμm thermal stress is 30MPa.And with the increase of power,the increase is the slowest.When the power is increased by 0.1W,the highest steady-state temperature of the SMR resonator increases by about 6℃,and the maximμm thermal stress increases by about 20MPa.On the basis of simulation,three different types of sonic resonators are simulated and optimized,and three different optimization schemes are obtained.For the SMR resonator,decreasing the nμmber of SiO2 layers in the Prague reflector and increasing the resonator area can improve the thermal performance of the resonator.The maximμm steady-state temperature of every SiO₂ decreases by 20℃.After optimization,the SMR type resonator has a power capacity of over 33dBm.For cavity structure FBAR,the maximμm steady-state temperature and maximμm thermal stress are the smal est with SiC as the supporting layer.The optimized power capacity of more than 30dBm;for the flexible substrate of PI resonator,enlarge the contact area of PI and silicon substrate can improve the thermal performance of the device.A rigid material with high thermal conductivity is used to improve the heat dissipation capacity of flexible PI devices on silicon substrate.On the basis of theoretical analysis,the MEMS technology is used to prepare the SMR type device with the highest power capacity,and its performance is tested.In the process of device preparation,an innovative method is proposed to make the edge of the film on a gentle slope.Specifically in the lithography process,by controlling the pitch mask and photoresist,photoresist can make the edge of a slope structure,when the mask and photoresist distance is greater than 0.5mm,the slope slope can reach 10 degrees,the etching selectivity,the gentle photoresist transfer to target film.Finally,a bulk acoustic wave duplexer for FTD Band 1 frequency band is designed.First,a complete Mason model of SMR resonator is established,and the Band 1 duplexer is realized by this model.In the simulation,the transmitted filter can reach 55dB in the received band,and the insertion loss in the passband is less than 2.8dB.The band insertion loss of the received filter is less than 2d B,and the out of band suppression in the transmitted band is more than 46dB.