An approach to frequency stability analysis using signal processing models （or systems） based on the stochastic signal processing theory is proposed

and the following are derived: unit impulse responses

tranfer functions

autocorrelations of the unit impulse responses

power or energy transfer functions of systems and subsystems; auto-covariances and power spectral density of the stochastic signals at every point in the systems; formulas of evaluating N sampling variances <σy2（N

T0

T）>or serveral main stochastic signals with the power law spectral type; and the theoretical

engineering and relative error formulas for the Allan variance.It is also pointed out that the Allan variance formulas in some literature [3

8

9-11] for calculating the flicker phase noise are improper.