Research On Low Phase Noise FBAR Oscillator

Emerging wireless systems aim to combine more functions and comply with more telecommunication standards.For this reason,wireless systems increasingly require circuits with smaller size,lower cost,and higher performance.In this complex system architecture,the oscillator is the most critical and one of the bulky modules in today's commercial wireless systems,so there is a great demand for reducing such modules.Film Bulk Acoustic Resonator(FBAR)has the characteristics of high quality factor and low size,which has greatly improved performance compared with traditional SAW and other devices.This makes it a good candidate to replace on-chip tuning large-volume resonant circuits and off-chip crystal resonators,and thus has become a hot spot in domestic and foreign research in recent years.This article first carried on the modeling research to the FBAR resonator.The working principle and important performance parameters of the FBAR resonator are clarified.Several equivalent circuit models of FBAR,including Mason,BVD and MBVD models,are analyzed in detail.In the ADS software,one-dimensional modeling and simulation analysis of FBAR is carried out and the Mason ADS equivalent circuit simulation simulation library of FBAR is established.Finally,the parameter values in the MBVD model are extracted,and this model is used in the subsequent oscillator simulation design.Then the phase noise of the FBAR oscillator is analyzed.Introduce the Leeson phase noise model,and use it as a guide to obtain the factors affecting phase noise through theoretical analysis.The passive network theory is used to derive the expression of the loaded quality factor in the Pierce structure FBAR oscillator circuit.Combining these two theories,a verification circuit of FBAR oscillator based on Pierce structure and oscillating frequency of 5.8GHz is designed in ADS,and the influence of the quality factor of the resonator and the loaded quality factor of the circuit on its phase noise is analyzed through simulation.Finally,the FBAR oscillator is designed based on the principle of negative resistance,which is simulated and analyzed in ADS and processed and tested in kind.The measurement results show that the designed FBAR oscillator has an oscillation frequency of 5.83 GHz,an output power of 9.493 d Bm,and a second harmonic suppression degree of-29 d Bc.The phase noise level is-99.57 d Bc/Hz@1MHz,-76.23 d Bc/Hz@100KHz,and the physical size is 26mm*31mm.The actual oscillator finally works between the series and parallel resonant frequencies of the FBAR resonator to meet the design requirements.It is smaller in size and has better output power and second harmonic suppression.