On the estimating of power spectral density of fractional frequency fluctuations from the sampled phase deviations

Rectangular and Hanning windows were used in spectral analysis, using the FFT estimator, applied on the sampled phase-time deviations and sampled averaged fractional frequency fluctuations. All five noise types were investigated, the sequences being produced by a computer noise generator. Despite a little difference in the spectrum level, both windows gave the correct slope for S_x(f). Slight distortion was observed at low frequencies for the white phase noise when a rectangular window is used. For S_x(f) the window type does not affect the spectrum slope for white phase, flicker phase and white frequency noises. In the case of flicker frequency and random walk frequency noises, the rectangular window produced an incorrect spectrum slope, while the Hanning window allows the correct identification of the noise type