The total deviation approach to long-term characterization of frequency stability

Total variance represents the first advancement in the estimation of an oscillating signal's long-term frequency stability since the conventional Allan variance estimator. It is called "Totvar" (pronounced tot'-var) for short. Its commonly reported square-root is the total deviation function called "Totdev" (tot'-dev). Totdev efficiently extracts broadband FM oscillator noise levels and types commonly encountered at long-term tau-averaging times, even though these are difficult to measure. The notable advantages of Totdev include: significantly improved confidence for estimating long-term frequency stability, lower sensitivity to the removal of linear frequency drift, and exact decomposition of the sample variance of frequency residuals.