Phase Noise Analysis for Differential Cross-Coupled LC Oscillators Using the Impulse Sensitivity Function

A new method for analyzing the phase noise in the oscillator is proposed using the impulse sensitivity function(ISF) model to improve the prediction accuracy of phase noise in differential cross-coupled LC oscillators.A general relation expression between the phase noise and an arbitrary noise source in the oscillator is derived based on large-signal analysis.The effective ISF for each noise device is solved and employed to calculate the contribution of each device to the phase noise.The closed-form expression of phase noise due to the total thermal noise in the oscillator is determined explicitly.Simulation results show that the relative errors in noise prediction for the tank and the differential pair are 1.34% and 2.88%,respectively,and are consistent with conventional methods.The relative error in noise prediction for the tail transistor reduces to 5.2% from 20.4% of the conventional methods.Moreover,the proposed method is more intuitive,and easier to implement.