An analysis of phase noise in differential cross-coupled tuned tank voltage controlled oscillators is presented. The effect of active device noise sources as well as the noise due to the passive elements are taken into account. The predictions are in good agreement with the measurements for different tail currents and supply voltages. The effect of the complementary cross-coupled pair is analyzed and verified experimentally. A 1.8GHz LC oscillator with a phase noise of -12ldBc/Hz at 600kHz is demonstrated, dissipating 6mW of power using spiral inductors.