The Optimised Design Of Acoustic Surface Wave Devices With Acoustoelectric Amplification Effect

As the 5G communication technology is getting developed in recent years,the demand for Surface Acoustic Wave(SAW)filters of Radio Frequency(RF)front end has greatly increased.Meanwhile,with the increase of the number of the communication frequency bands and the development of carrier aggregation,packaging the power amplifiers and filters in the same module will both reduce the crosstalk and improve the integration.In order to achieve the goal of integrating filtering and amplification,the acoustoelectric amplification effect has been introduced to amplify the amplitude of the SAW,which will also play an important role in the integration of RF and the development of mobile communication.The current research of the acoustoelectric amplification effect mainly focuses on the analysis of the high-mobility semiconductor thin films on piezoelectric substrates with high electromechanical coupling coefficient.There is a lack of research about the simulated models and optimisation design of SAW devices using acoustoelectric amplification effect.Aiming at filling the gap,this dissertation built the simulated model of Coupling-of-Mode(COM)using the acoustoelectric amplification effect.By changing the structure of the interdigital transducer,the type of the devices and the acoustoelectric amplification coefficients,the insertion loss decreases and the pass-band ripple becomes smaller,so as to filter and amplify the surface acoustic wave.In this dissertation,the acoustoelectric effect was analysed and the acoustoelectric amplification effect was incorporated in the model of COM.Furthermore,we made SAW delay-lines which set the frequency at 121 MHz and the acoustoelectric film was deposited on the devices for testing.The testing result is in accordance with that of the COM model with the acoustoelectric effect,which verifies the result of the model.In addition,this dissertation attempted to optimise the design of the SAW delay-lines filter.The single-electrode IDT of SAW delay-line devices,the single-electrode IDT with reflection gates of SAW delay-line devices were simulated to reduce the pass-band ripple.In order to achieve a better device performance and to decrease the insertion loss and the passband ripple.The coupling-of-modes parameters of SPUDT were then calculated by Kenya-Hashimoto method,and the SAW delay-line devices with the SPUDT structure was simulated.The insertion loss is converted from a negative value to a positive one,with a gain of 1.13 d B.The results of the simulation study show that compared with the single-electrode IDT structure,SPUDT structure of SAW delay-line devices using the acoustoelectric amplification effect enables the insertion loss convert from a negative value to a positive one,make it possible for the device to amplify the signals and effectively reduce the passband ripple.Last,this dissertation optimised the design of the SAW resonator and LCRF with firstthird modes.In the purpose of obtaining a new version of SAW filter with less passband ripple,we conducted simulation study on the the SAW resonator and LCRF with firstthird modes and applying the acoustoelectric amplification effect.Then we cascaded the LCRF with first-third modes to suppress sidelobe.For efficiency,the simulated annealing algorithm was then introduced to obtain the optimal input parameters of the devices.By using the simulated annealing algorithm,the value of the insertion loss is increased from a negative number to a positive number,with a gain of 1.01 d B in LCRF with first-third modes and the sidelobe suppression is-7.65 d B;meanwhile,the cascade LCRF with first-third modes has a gain of 1.04 d B and the sidelobe suppression is-14.5 d B.The optimisation results indicate that the study of the structure of LCRF with first-third modes using the acoustoelectric amplification effect will inform the design of the SAW devices with flat passband ripple and the amplification function.