摘要:
在薄膜体声波谐振器(FBAR)振荡器中,振荡器的有载品质因数(QL)和FBAR的品质因数(Q值)均与振荡器的频率稳定度有关。为了研究这两种品质因数对FBAR振荡器频率稳定度的影响,在COMSOL Multiphysics软件中建立了FBAR的多物理场模型,通过频域仿真和MBVD(Modified Butterworth-Van Dyke)模型参数拟合,得到了MBVD模型参数,并在ADS软件中建立了MBVD模型电路,通过S参数仿真结合求取Q值的Bode法得到了不同损耗对应的Q值；再建立基于Pierce架构的振荡器,通过谐波平衡仿真得到了相位噪声,通过分别改变QL和Q得到了二者对FBAR振荡器频率稳定度的影响。结果表明：频率稳定度随QL和Q的增大而增大,Q值随不同损耗的增大而减小。当FBAR的Q值低于338时,即使通过增大QL来提高频率稳定度,其效果也不佳,以此FBAR构成的振荡器将不能满足作为无线通信射频前端参考信号源或者FBAR传感器读出电路的要求。为FBAR参考信号源和FBAR传感器读出电路的设计提供了一定的参考。
Abstract:
The loaded quality factor (QL) of the film bulk acoustic resonator(FBAR) oscillator and the quality factor (Q value) of FBAR are related to the frequency stability of FBAR oscillator. In order to study the effect of the two kinds of quality factors on the frequency stability, the multi physical field model of FBAR was established in the COMSOL multiphysics software. The parameters of the modified Butterworth-Van Dyke (MBVD) model were got by frequency domain simulation and model parameter fitting. A model of MBVD circuit was established in the ADS software, and Q value for different loss was obtained by the simulation of S parameters and computing the corresponding Q value with the Bode method. The Pierce-based oscillator was established and simulated with the harmonic balance, thus the phase noise was obtained by changing QL and Q, and the effect of the two factors on frequency stability was got. The results show that the frequency stability increased with the increase of QL and Q, Q decreased with the increase of different losses. If the Q is lower than 338, the effect of increasing QL to improve the frequency stability is poor. Using this kind of FBAR to construct oscillator will not meet the requirements of FBAR wireless communication RF front-end as the reference signal source and the readout circuit of FBAR sensor. This paper provides a reference for FBAR frequency reference design and FBAR sensor readout circuit.
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