A general-purpose harmonic-balance approach to the computation of near-carrier noise in free-running microwave oscillators

Discusses a novel harmonic-balance approach to the computation of near-carrier phase noise and amplitude noise in free-running microwave oscillators. The well-known qualitative picture of phase noise generation is quantitatively restated in a way compatible with the needs of general-purpose CAD (computer-aided design). The capabilities of previously available approaches to the same problem are extended in several respects. The proposed method allows the computation of far- and near-carrier noise in arbitrary user-defined circuits, without any compromise on circuit topology, nonlinear device models, and harmonic content of the periodic steady state. Noise generation in autonomous systems is shown to be caused by two independent mechanisms: direct frequency modulation of the oscillator, dominant at low-frequency deviations, and conventional frequency conversion, dominant at high-frequency deviations. A unified treatment of the two aspects is found to be possible as a rigorous logical consequence of the harmonic-balance equations.<>