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石英晶体振荡器的极限稳定度是由时域噪声本底相对应的石英谐振器频率噪声决定的。只有减小电子噪声的起伏,才能测量谐振器本身的谐振频率起伏。使用π型传输网络和相位平衡电桥,能够将激励源的相位起伏抑制50-60dB。此测量系统曾在室温下测量了大量的成对谐振器,发现1/f 频率噪声电平和 Q 值之间的相互关系遵循1/Q~4规律。为了将谐振器频率起伏的测量扩展到极低温,研究了一种能测不同谐振器对的新测量系统。因此,在4K 和1K 温度下测得了1/f 频率噪声,并观察到随着 Q 值的增加而噪声大大减小。现在有一种理论能解释1/Q~4规律。这就是根据声波衰减和速度变化引起的三声子相互作用过程来解释。声波衰减和速度变化这两种现象均可用热声子的张弛时间来加以说明。
The limit stability of quartz crystal oscillator is determined by the quartz resonator frequency noise corresponding to the time-domain noise floor. Only by reducing the fluctuation of the electronic noise can the resonant frequency of the resonator itself be measured. Using pi-type transmission networks and phase-balanced bridges, the phase fluctuations of the excitation sources can be suppressed by 50-60 dB. This measurement system has measured a large number of pairs of resonators at room temperature and found that the relationship between the 1 / f frequency noise level and Q follows the 1 / Q ~ 4 law. In order to extend the measurement of resonator frequency fluctuations to cryogenic temperatures, a new measurement system that can measure different pairs of resonators is studied. Therefore, 1 / f frequency noise was measured at 4K and 1K temperatures and it was observed that the noise was greatly reduced as the Q value increased. There is a theory that can explain 1 / Q ~ 4 law. This is explained by the three-phonon interaction process caused by sound attenuation and velocity variations. Both acoustic attenuation and velocity variations can be explained by the relaxation time of thermoacoustic phonons.