ISI (p-p) Result

The Jitter mode Inter-Symbol Interference (ISI) measurement is the measure of the pattern-dependent interference effects within a signal. It is a measure of how much the amplitude of a symbol depends on its location within the pattern. The corresponding jitter measurement is Data Dependent Jitter (DDJ). The ISI measurement result is reported for both one and zero levels. You can select the one/zero level definitions to be based on an average level or on minimum Consecutive Identical Digits (CID). Measurements based on CID minimize the effects of ISI on the levels. Inter-Symbol Interference is displayed in the current vertical channel units or Unit Amplitude. These selections are made in the Amplitude Measurements tab of the Configure Jitter Measurements dialog.

ISI is measured using the following steps:

1. The instrument acquires 16 samples from each of the first 256 symbols in the pattern. If the pattern has fewer than 256 symbols, 16 samples are acquired from every symbol in the pattern. These samples (up to 4096) are taken in random order at the measurement location, which is normally the center of the symbol.
2. The average level of each symbol is obtained. These averaged levels are combined into an ISI histogram for the ones and a similar histogram for the zeros. The ISI for each level is calculated as the peak-to-peak width of each histogram.
3. The above steps are continually repeated, displaying a running average level for each symbol.

More Information

• Interference Components Tree
• Amplitude Toolbar

SCPI Command

:MEASure:AMPLitude:ISI