The third-difference approach to modified Allan variance

This study gives strategies for estimating the modified Allan variance (MVAR), and formulas for computing the equivalent degrees of freedom (EDF) of the estimators. A third-difference formulation of MVAR leads to a tractable formula for EDF in the presence of power-law phase noise. The effect of estimation stride on EDF is shown. First-degree rational-function approximations for EDF are derived, and their errors tabulated. A theorem allowing conservative estimates of EDF in the presence of compound noise processes is given.