:MEASure:EYE:DI

Meas. mode:
Eye
Package License:
L-RND
FlexDCA mode:
Eye
Compatible waveforms:
NRZ
PAM4
Flex Apps:
FlexDCA
FlexRT
DI Commands

Command Syntax

:MEASure:EYE:DI

Query Syntax

:MEASure:EYE:DI?

Description

Performs an Advanced Eye Deterministic Interference (DI) measurement in Eye/Mask mode on NRZ or PAM4 signals. DI is the amount of vertical interference on a signal that is due to deterministic causes. Since the measurement is made on an eye diagram, the pattern itself can be of any type or length, such as PRBS31. (Jitter Mode is limited to making measurements on patterns up to PRBS16.) The corresponding jitter measurement is Deterministic Jitter (DJ). The DI measurement result is reported for both One and Zero levels. If you experience difficulties measuring a PAM4 signal, confirm that the signal-type setting is set to PAM4 with the :CHANnel:SIGNal:TYPE command.

DI is measured using the following steps:

  1. The instrument measures Random Noise (RN), Periodic Interference (PI), and Inter-Symbol Interference (ISI).
  2. The ISI histogram for the one level is convolved with the histogram of the one level RN and PI data, and the same is done for the zero level data. These histograms are referred to as the Total Interference (TI) histograms.
  3. Using the measured value of RN, a dual-dirac model is fit to the TI histogram. The model is fit at a probability of 10E-3 divided by the pattern length.

The random and deterministic components, RI and RN, are determined by analyzing the crossing regions of the eye and measuring random jitter using a Q-scale approach. Separation of RN is made in the presence of all DI components using this method. Total Jitter (TI) is measured at the probabilities specified by :MEASure:EYE:TI:TIBer. To measure RN, use the :MEASure:EYE:RN command. To measure TJ, use the :MEASure:EYE:TI command.

The query form of the command returns the measured DI. If the measurement is already on, the measurement listing is moved to the top of the displayed results table.

To increase measurement accuracy, use RN stabilization:

  1. In Jitter Mode, measure Random Noise (RN) on the signal while using a short pattern.
  2. Switch to Eye/Mask Mode
  3. Use the :MEASure:EYE:DI:RNSTabilize to turn on RN stabilization and :MEASure:EYE:DI:RNSValue commands to specify the short-pattern RJ result measured in step 1.
  4. Switch to a long pattern.
  5. Measure DI, RN, and TI.

This Eye mode measurement can be applied to both NRZ and PAM4 waveforms.

Requires FlexDCA revision A.05.30 and above.

Requires Option 401, Advanced Eye Analysis Software license.

Measurement Identification

Avoid subtle programming errors! To ensure that the correct measurement is installed or queried, always explicitly identify a measurement when installing a measurement or querying a measured value, status, or detail. To identify a measurement, specify the measurement's source waveform (:SOURce child command). With some measurements, you may also need to specify other identifying values. Generally, when selecting a measurement using FlexDCA's GUI, if a dialog appears prompting you to select values, you should explicitly specify these values when remotely identifying the measurement. More information.

For example, to return the status of the measurement, :MEASure:EYE:DI:

flex.write(':MEASure:EYE:DI:SOURce CHAN1A')
if flex.query(':MEASure:EYE:DI:STATus?') == 'CORR';
    measurement = flex.query(':MEASure:EYE:DI?')
else:
	details = flex.query(':MEASure:EYE:DI:STATus:DETails?')
	reason = flex.query(':MEASure:EYE:DI:STATus:REASon?')

Child commands for measurement identification:

  • :MEASure:EYE:DI:SOURce
  • :MEASure:EYE:DI:RNSTabilize
  • :MEASure:EYE:DI:RNSValue:LEVel1
  • :MEASure:EYE:DI:RNSValue:LEVel0

Common Measurement Queries

Example Command Sequence

:SYSTem:MODE EYE
:MEASure:EYE:DI:SOURce CHAN1A
:MEASure:EYE:DI?