PAM Levels

PAM Levels measures all levels of a PAM signal displayed as a single-valued waveform. On NRZ signals, this measurement will measure the zero and one levels.

Settings That Affect This Measurement
Setting Description
PAM-N Analysis Setup Dialog Box Settings
Amplitude Units Sets the amplitude units for measurement: volts, Watts, or percent.

Measurement Algorithm

  1. Identify one of each of the "n" logic levels on a PAMn signal or two levels on an NRZ signal.
  2. Determine the center 12.5% (1/8) interval of each identified level.
  3. Calculate the mean amplitude level over each identified interval.

Setting the Timespan

You must set Infiniium's timespan wide enough so that each logic level is visible on the screen. For example, for a PAM4 signal this would be four levels (0, 1, 2, 3) or for an NRZ signal this would be two levels (0, 1). Failure to set the timespan wide enough results in an error. Consider the following items when setting the timespan:

  • If multiple identical levels are displayed, the level that is present for the longest time will be selected for measurement. For example, if two logic levels are shown on the waveform, with one being 100 ps and the other being 150 ps, the 150 ps level is selected to be measured.
  • To be considered a measurable level, the level must include at least 50% of the leading and trailing edges.

To measure

  1. Click Auto Scale in the menu toolbar.
  2. Adjust the time scale so that at least one of each of the four possible PAM levels or two of NRZ levels are displayed. Any number of the same level can be displayed, but there must be at least one of each level displayed.

    3. If the timespan is too narrow, the measurement results panel displays Region? or Level? instead of a measured value. Increase the timespan.

  3. Click the toolbar's PAM tab.
  4. On the toolbar, locate and click the Levels button.
  5. Select the Region in which to make the measurement:
    • Displayed Waveform — is what you see in the waveform window (which can be a zoomed-in view of the complete waveform).
    • Entire Waveform — specifies the complete waveform.
    • Region N — If regions are enabled for the selected signal, you can select one of those regions.

SCPI Command

:MEASure:PAM:LEVel