Research And Design Of Low Phase Noise Oscillator Based On Thin Film Bulk Acoustic Resonator

With the development of human history,communication technology is gradually moving from backward to advanced.In modern times,people are relying more and more on communication technology,so the demand for communication technology is getting higher and higher.Communication systems are required to be smaller,faster and lower power consumption.As one of the most popular researches,the thin film bulk acoustic resonator(FBAR)has a promising prospect in the future market.The thin film bulk acoustic resonator has many advantages.For example,it has a small size,high quality factor(up to 1000 or more),low insertion loss,high resonant frequency and it also has a larger power capacity than surface acoustic wave resonators.The most important is that the preparation process of the thin film bulk acoustic resonator is compatible with the CMOS process.Therefore,the application of FBAR in communication systems,especially RF front-end,is more and more important.A low phase noise oscillator based on thin film bulk acoustic resonator is studied in this paper.In this paper,the phase noise and the thin film bulk acoustic resonator which are the key performance and core component of the oscillator.At first,the theory and model of the oscillator are studied and then,some theories of FBAR resonator are studied such as piezoelectric theory and acoustic theory and so on.On the basis,the working principle and several important parameters of the FBAR resonator are studied.The bulk acoustic wave resonator has three basic structures: FBAR?SMR and silicon back etching type.The structures of these three kinds of bulk acoustic wave resonators are introduced and their advantages and disadvantages are analyzed.In order to analyze and study the FBAR resonator better,the FABR resonator is modeled.There are three models: Mason model,BVD model and MBVD model.After analyzing these three models,the MBVD model is the final choice of this paper.Explained how to get the six parameters of the MBVD model.In order to improve the quality factor,a cavity-type FBAR resonator is prepared.Each layer of materials constituting the FBAR resonator are compared and the most suitable material is selected.The experimental procedure and process parameters for the preparation of FBAR resonators are briefly described.The special features of the FBAR resonators prepared in this paper is the difference in the structure of the cavity.A method of preparing a gentle slope structure on the edge of the pattern has been invented in this paper which can avoid the problem that the upper layer of thin film is too stressed to fractured at the edge of the pattern(which can reduce the quality factor).The prepared FBAR resonator was tested and its operating frequency was about 1.92 GHz.The phase noise is the key parameter of the oscillator.In this paper,the Leeson model of oscillator is studied,and three factors which affect the phase noise of oscillator are analyzed.The three factors include the noise of the transistors in the amplify circuit,the output power of the oscillator and the quality factor of the frequency-selective network.Finally,based on the entire contents of the research,the circuit of the oscillator is designed using the ADS tool.The phase noise of the oscillator reaches-140.532dBc@1MHz.