Research On RF Filter Chips Of Thin Film IPD And FBAR Technology

5th Generation Mobile Communication Technology has put forward more strict requirements for the current signal communication system than before.As an important part of radio frequency(RF)front-end device,RF filter plays an important role in screening out clutter signal and ensuring high quality communication.Integrated Passive Devices(IPD)technology and Film Bulk Acoustic Resonator(FBAR)technology are two important design technologies for RF filters,which have occupied an important market share.Thin film IPD technology has the advantages of high quality factor,low insertion loss,miniaturization,easy integration,etc.,which is suitable for fabricating wideband and ultra-wideband RF filters.FBAR technology has the advantages of extremely high quality factor,high electromechanical coupling coefficient,high rectangular coefficient,high stopband suppression,etc.,and is uniquely positioned to fabricate highselectivity RF filters.In this thesis,the author uses the above two technologies to design RF filters,which include the following aspects.(1)Two high-selectivity RF filters based on LC resonator structures are proposed,which are suitable for sub-6G communication.Controllable transmission zeros on both sides of the passband are introduced by LC resonators,achieving the design goal of high roll-off and high stopband suppression.The measured dynamic bandwidth adjustment range of these two filters is large,and the return loss is excellent,and the stopband suppression is high.The relevant researches have been published in international academic journal IEEE Transactions on Circuits and SystemsⅡ.(2)A high roll-off millimeter wave IPD filter chip with adjustable bandwidth is proposed.By adding a branch circuit into the three-level cascade coupled line filter structure,two transmission zeros on both sides of the passband are successfully introduced,which significantly improve the roll-off and stopband suppression.The measured results show that the millimeter wave filter chip has the characteristics of high roll-off,high stopband suppression,low insertion loss,and good passband matching.The relevant researches have been published in international academic journal International Journal of RF and Microwave Computer-Aided Engineering.(3)A high frequency FBAR filter for 3.4-3.6 GHz is proposed.Compared with most traditional acoustic filters working below 3 GHz,the requirements of high frequency and wideband have set higher standard for design work.To solve these problems,the author adopts scandium doped FBAR process.The electromechanical coupling coefficient of the FBAR resonator can be improved by doping scandium into the aluminum nitride piezoelectric layer.The longitudinal wave velocity and material density of the FBAR resonator are measured by model fitting.The model parameters are modified,and then the schematic of the circuit is analyzed in detail.The experimental results show that the FBAR filter chip is of high roll-off and high stopband suppression.The relevant researches have been published in international academic journal Electronics.