SIGLENT TECHNOLOGIES SNA5000A Series User Manual Download

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SNA5000A Vector Network Analyzer User Manual 134

5.8.5

Eye Diagram Scale Management

By default, the eye diagram is displayed in the automatic scale settings, which show the

details as clearly as possible. They can also be manually changed.

The scale settings in the vertical axis can be changed manually. But those in the

horizontal axis depend on the data rate of the input signal, which can't be changed after the
simulation starts.

To switch to a scale setting mode, click the

Auto Scale

Manual

radio button in the

Scale/Mask

bar.

To change the scale or offset values in

Manual

scale mode, set the value in the

Scale/Div

Offset

textbox. The

Offset

value here is the value that the center vertical scale

line refers to.

5.8.6

Mask Test for Eye Diagram

Mask patterns are some areas where the eye diagram is forbidden to pass, which

transfer the design requirements of the transmission systems into the numerical
characteristics of eye diagrams. They usually rule the tolerance of logic 0,1 level and rise or
fall time. If the eye diagram passes through the areas, the TDR option judges that the eye
diagram can't meet the requirement, leading to the failure of the mask test. According to
different communication standards, or at the different nodes in a communication system,
different mask patterns should be applied. The first step to mask test is to select or design a
suitable mask pattern based on the requirements.

To select or change the mask pattern applied, click the

Mask Pattern

button in the

Scale/Mask

bar to open the

Mask Pattern

dialog.

In the

File

tab of the dialog, preinstalled standard patterns or user-defined mask files

(.MSK format) can be loaded. In the

Scale

tab, the

Margin

of the mask, start

Position

of a

bit,

Delta

time of a bit, and

Logic Level

can be set in textboxes. In the

Edit

tab, the positions

of vertices in the mask pattern can be changed by set values in the textboxes. Dragging the
vertices in the left window also makes sense, but it's recommended to drag with a mouse
connected to the VNA, because the points may be too close together for easy entry using
touch operation.

Close the dialog after saving the modifications to a mask file, the new pattern will be

applied to the next mask test.

To switch on or off the mask test, click the

Mask Test

checkbox in the

Scale/Mask

bar.

5.8.7

Jitter & Statistical Eye Diagram

Jitter is the transient deviation from the corresponding ideal position of a signal over

successive trigger events. High jitter worsens the transmission performance. It's divided into
the Deterministic Jitter (DJ) and the Random Jitter (RJ). RJ is generated by some
unpredictable factors and is independent of the input bit patterns. The models for RJ usually
have a Gaussian distribution, and the magnitudes are represented in root mean square
(RMS) values. DJ is generated by some repeatable and predictable factors and usually has a
finite magnitude value. The jitter related to the input bit patterns in DJ is called the Data
Dependent Jitter (DDJ), while the other jitter in DJ is called the Periodic Jitter (PJ).