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Jitter is often measured as a fraction of UI. For example, jitter of 0.01 UI is jitter that moves a signal edge by 1% of the UI duration. The widespread use of UI in jitter measurements comes from the need to apply the same requirements or results to cases of different symbol rates. This can be d
In electronics and telecommunications, jitter is the deviation from true periodicity of a presumably periodic signal, often in relation to a reference clock signal. In clock recovery applications it is called timing jitter. [1] Jitter is a significant, and usually undesired, factor in the design of almost all communications links.
Jitter is the undesired deviation from true periodicity of an assumed periodic signal in electronics and telecommunications, often in relation to a reference clock source. Jitter may be observed in characteristics such as the frequency of successive pulses, the signal amplitude , or phase of periodic signals.
Instantaneous packet delay variation is the difference between successive packets—here RFC 3393 does specify the selection criteria—and this is usually what is loosely termed "jitter", although jitter is also sometimes the term used for the variance of the packet delay. As an example, say packets are transmitted every 20 ms.
The counter implementation's accuracy is limited by the clock frequency. If time is measured by whole counts, then the resolution is limited to the clock period. For example, a 10 MHz clock has a resolution of 100 ns. To get resolution finer than a clock period, there are time interpolation circuits. [6]
This of course means that the clock skew between two points varies from cycle to cycle, which is a complexity that is rarely mentioned. Many other authors use the term clock skew only for the spatial variation of clock times, and use the term clock jitter to represent the rest of the total clock timing uncertainty. This of course means that the ...
During an interval of time τ, as measured by the reference clock, the clock under test advances by τy, where y is the average (relative) clock frequency over that interval. If we measure two consecutive intervals as shown, we can get a value of ( y − y ′ ) 2 —a smaller value indicates a more stable and precise clock.
Because the CAS latency is specified in clock cycles, and not transfers (which occur on both the rising and falling edges of the clock), it is important to ensure it is the clock rate (half of the transfer rate) which is being used to compute CAS latency times. [citation needed] Another complicating factor is the use of burst transfers.