A computational method in predicting distributed oscillator phase noise

Distributed oscillator as a new type of oscillator for the integrated circuit design has emerged. In this paper, a frequency-domain analytical method is employed for the purpose of predicting phase noise in distributed oscillators. The method is founded upon a linear model, and then nonlinear effects are taken into consideration. The computational formulae are obtained for predicting distributed oscillator phase noise. The correctness and accuracy of the computational formulae are verified by harmonic balance (HB) simulation in advance design system (ADS). It is found that the calculated phase noise shows a good agreement with the phase noise observed in simulation. In three test cases, namely, three 4-stage distributed oscillators operating at three different frequencies, the calculated and simulated phase noise follow the same pattern while a maximum absolute error of 2.3dBc/Hz is observed at 5 MHz offset.