The prediction, simulation and verification of the phase noise in low-phase-noise crystal oscillator

In order to achieve the prediction of the phase noise of low phase noise crystal oscillator, based on the classic phase noise model of Leeson, the load Q value (Q_L) is calculated according to the selected oscillator circuit parameters. Thus, on the basis of Lesson phase noise formula, the predicted results of the phase noise of low phase noise crystal oscillators are obtained. Then, the nonlinear transistor model is constructed to simulate the phase noise of low phase noise crystal oscillator by using the ADS (Advanced Design System) simulation software of Agilent and obtain the simulated curve of the phase noise. At last, practical measurement has been performed on these low phase noise crystal oscillator prototypes. The measured results show that: the predicted phase noise of the oscillators and the ADS simulation results obtained by using nonlinear transistor model are both close to the actual measured phase noise, which are at 100Hz and far away offset the carrier frequency. After that, the existence of the deviation, which is near carrier frequency, is analyzed. The prediction and simulation methods given by this paper might be beneficial to simplify the design progress of the low phase noise crystal oscillator.