Time deviation (TDEV), also known as
Time variance (TVAR) also known as
TDEV is a metric often used to determine an aspect of the quality of timing signals in telecommunication applications and is a statistical analysis of the phase stability of a signal over a given period. Measurements of a reference timing signal will refer to its TDEV and maximum time interval error (MTIE) values, comparing them to specified masks or goals.
Definition
The most common estimator uses the modified Allan variance
where
or TDEV, which is the square-root of TVAR, may be derived from MDEV modified Allan deviation