Jitter
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In telecommunication, jitter is an abrupt and unwanted variation of one or more signal characteristics, such as the interval between successive pulses, the amplitude of successive cycles, or the frequency or phase of successive cycles.
Jitter may be specified in qualitative terms (e.g. amplitude, phase, pulse width or pulse position), or quantitative terms (e.g. mean, RMS, or peak-to-peak displacement).
The low-frequency cutoff for jitter is usually specified at 1 Hz.
For clock jitter, there are two main parameters: phase jitter and cycle to cycle jitter (or period jitter).
Phase jitter consists of peak to peak phase jitter and RMS phase jitter. The peak to peak phase jitter is the difference between the maximum and minimum phase of the clock signal over all time. The RMS phase jitter is the standard deviation of the peak to peak phase jitter.
Cycle to cycle (or period) jitter is the variation from one period to the next adjacent period of the signal. In order to determine the variation between adjacent periods, all consecutive periods need to be measured. The peak to peak period jitter is the worst case of cycle to cycle jitter.
Inside digital to analog converters jitter causes unwanted high-frequency distortions. In this case it can be suppressed with high fidelity clock signal usage.
See also
Source: Federal Standard 1037C and MIL-STD-188