This tutorial by Thomas H. Lee and Ali Hajimiri provides a comprehensive overview of oscillator phase noise, emphasizing the limitations of linear time-invariant (LTI) theories and introducing a more accurate, linear, time-varying (LTV) model. The authors highlight that device noise undergoes multiple frequency translations to become oscillator phase noise, and the LTV model accounts for this process by considering the noise-to-phase transfer function. Key insights include the importance of symmetry in suppressing the upconversion of 1/f noise into close-in phase noise, the role of cyclostationary effects, and the AM-PM conversion. The tutorial also discusses the performance of specific oscillator topologies, such as the Colpitts oscillator, and provides practical examples of LC and ring oscillators. The appendices cover simulation issues and the accommodation of amplitude noise. Overall, the LTV model offers a more quantitative understanding of oscillator phase noise, allowing for better design and optimization of oscillators.This tutorial by Thomas H. Lee and Ali Hajimiri provides a comprehensive overview of oscillator phase noise, emphasizing the limitations of linear time-invariant (LTI) theories and introducing a more accurate, linear, time-varying (LTV) model. The authors highlight that device noise undergoes multiple frequency translations to become oscillator phase noise, and the LTV model accounts for this process by considering the noise-to-phase transfer function. Key insights include the importance of symmetry in suppressing the upconversion of 1/f noise into close-in phase noise, the role of cyclostationary effects, and the AM-PM conversion. The tutorial also discusses the performance of specific oscillator topologies, such as the Colpitts oscillator, and provides practical examples of LC and ring oscillators. The appendices cover simulation issues and the accommodation of amplitude noise. Overall, the LTV model offers a more quantitative understanding of oscillator phase noise, allowing for better design and optimization of oscillators.