An overview of oscillator jitter

A basic measure of an oscillator’s performance is its frequency stability (or instability depending on one’s point of view). In the long term (timescales of days or years), we refer to frequency changes as aging. On moderate timescales (seconds), the stability of an oscillator is often characterized in terms of its Allan variance [1]. On short timescales (usually less than one second), frequency stability is often characterized in terms the fluctuations of the phase of the signal (phase noise) or the fluctuations in timings of its transitions or the periods of its cycles (jitter).