Evaluation of Phase Noise Close to Carrier Frequencies in Narrow-Band Colpitts Oscillator Using Nonlinear Model

Abstract

This letter describes an analysis of the close to carrier phase noise characteristics of the Colpitts oscillator circuit with two or more crystal resonators. The open-loop impedance and the quality factor of a regular oscillation state are computed by using a nonlinear transistor model. Moreover, based on the Leeson’s model, the near carrier phase noises are estimated using the calculated Q-factors. As a result, it was shown by using a crystal filter that the phase noise close to carrier frequencies is improved.