An optimized multiphase oscillator with harmonic balance analysis for oscillation frequency and amplitude prediction

Predicting the oscillation frequency and amplitude of oscillators is a non-trivial exercise. This work presents a modified multiphase Colpitts oscillator with improved phase noise performance and presents a different approach to oscillator analysis. Frequency pulling is not accurately predicted and cross-coupling of currents in multiphase oscillators makes frequency and amplitude difficult to predict accurately. A single and multiphase oscillator analysis using the harmonic balance method is presented. A new multiphase oscillator structure based on the Colpitts´ oscillator is investigated. The numerical and analytical solutions are able to accurately predict the oscillation frequency to within 2.5 % of the SPICE solution. The analytical solution can be used to predict the first harmonic and combined with the numerical simulations will allow for the harmonic amplitudes to be tailored to specific applications.