This paper presents a systemic analysis for phase noise performances of differential cross-coupled LC oscillators by using Hajimiri and Lee's model. The effective impulse sensitivity functions (ISF) for each noise source in the oscillator is mathematically derived. According to these effective ISFs, the phase noise contribution from each device is figured out, and phase noise contributions from the device noise in the vicinity of the integer multiples of the resonant frequency, weighted by the Fourier coefficients of the effective ISF, are also calculated. The explicit closed-form expression for phase noise of the oscillator is definitely determined. The validity of the phase noise analysis is verified by good simulation agreement.

This paper presents a systemic analysis for phase noise performances of the series quadrature oscillator (QOSC) by using the time-variant impulse sensitivity function (ISF) model. The effective ISF for each noise source in the oscillator is derived mathematically. According to these effective ISFs, the explicit closed-form expression for phase noise due to the total thermal noise in the series QOSC is derived, and the phase noise contribution from the flicker noise in the regenerative and coupling transistors is also figured out. The phase noise contributions from the thermal noise and the flicker noise are verified by SpectreRF simulations.