PAM Eye Levels

The Eye mode PAM Eye Levels measurement measures all three eye amplitude levels (vertical centers) of a PAM4 signal. On NRZ signals, the vertical center of the single eye is measured.

Settings That Affect This Measurement

Setting	Description
PAM-N Analysis Setup Dialog Box Settings
Receiver Sample Timing	Configures the timing for sampling the signal data for all PAM measurements in Eye/Mask mode. Depending on measurement conditions, this command may not affect the measurement.
Eye Center Location	Selects the basis for determining the location of an eye's center on the waveform: at maximum eye width or maximum eye height. Depending on measurement conditions, this command may not affect the measurement.
Eye Level Width	Defines the timespan (in percentage of symbol width) over which an eye's amplitude level is measured.
Amplitude Units	Sets the amplitude units for measurement: volts, Watts, or percent.

• Overall PAM4 measurement algorithm for Eye mode

Measurement Algorithm

1. An autoscale is performed to determine if the signal is formatted as PAM4 or NRZ.
2. Determine the approximate signal-level amplitudes.
3. Locate the crossing (transition) regions on both sides of the eyes.
4. Determine the symbol period.
5. Find the center of each eye. Note that the Receiver Sample Timing setting determines if only the middle eye (Eye 1/2) is located or if all three eyes are located (Eyes 0/1, 1/2, and 2/3).
• If the Eye Center Location setting is set to Maximum Eye Width, determine the horizontal line (center amplitude) across the eye at the maximum eye width and find the time at the line's midpoint (center time).
• If the Eye Center Location setting is set to Maximum Eye Height, determine the vertical line (center time) across the eye at the maximum eye height and find the amplitude at the line's midpoint (center amplitude).
6. The Eye Level measurements are the amplitudes of the eye centers located above.

To measure

1. Select Eye/Mask Mode.
2. Click Auto Scale in the menu toolbar.
3. Click the toolbar's PAM tab.
4. On the toolbar, locate and click the Eye Levels button.

SCPI Command

:MEASure:EYE:PAM:ELEVel