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Owning Palette: Jitter VIs
Requires: Jitter Analysis Toolkit
Computes the bit error rate at positions along the unit interval and returns a bathtub plot that represents the eye opening as a function of the bit error rate (BER). Bathtub plots are useful for showing the relationship of the sampling time in the waveform to BER.
|Note This VI appears on the block diagram when you add a bathtub plot to the front panel. On the Controls palette, select Addons»Jitter Analysis to navigate to the bathtub plot indicator.|
|TB specifies the length in time of the unit interval on the x-axis of the bathtub plot.|
|random jitter specifies the amount of random jitter in the signal.|
|deterministic jitter specifies the amount of deterministic jitter in the signal.|
|BER limit specifies the minimum bit error rate (BER) you want to display in the bathtub plot. The default is 1E–25.|
|error in describes error conditions that occur before this node runs. This input provides standard error in functionality.|
|Bathtub plot returns the data you can wire to a bathtub plot indicator.|
|BER eye closure returns the level at which the eye becomes completely closed.|
|error out contains error information. This output provides standard error out functionality.|
The following front panel shows how a bathtub plot illustrates the probability of a bit error occurring given the sampling time along the unit interval.
Near the level crossings, the BER is 0.5, which means there is an equal probability of an error occurring in a bit transmission. The curve is mainly flat near the level crossings because deterministic jitter, colored yellow, primarily affects signals at those positions. The BER, represented by the curve, drops sharply as the sampling point moves away from the level crossings on either end of the unit interval. These areas, colored blue, contain random jitter mechanisms. The sigma of the Gaussian processes that produce random jitter determines the BER.