In this paper we present an analysis of phase noise distribution. Phase noise, of designed and realized test oscillator, as a consequence of low frequency (LF) noise up-conversion was simulated. The analysis shows that low frequency noise sources, which are inside of transistor, give the pure Gaussian distribution of phase noise and LF noise sources located out of transistor change this distribution. This behavior could be explained by the influence of transistors and transistor's package impedance, which contribute to the signal delay.