QE and VE Crosstalk Analysis

For crosstalk analysis, the design incorporates multiple combinations of Eye Sources and Eye Probes. The typical crosstalk situation has one victim channel (the one whose integrity is being assessed) and one or more aggressor channels creating the crosstalk. Each channel has an Eye Source on the transmit end and an Eye Probe at the receive end; these two components link to each other via parameters. (A channel may have multiple Eye Probes, but only the probe at the receiver should be linked to the source.) To make the analysis meaningful, the design should use coupled transmission lines.

The basic idea of crosstalk analysis is to run the victim channel alone to obtain the victim’s eye diagram with no crosstalk. Then run both the victim and the aggressor channels, compute the victim’s eye diagram again, and compare the two eyes to assess the effect of the crosstalk.

Quick Eye and VerifEye treat correlation differently, affecting the treatment of crosstalk.

QuickEye is similar to transient in the way it deals with correlation. The algorithm inherently takes into consideration the time behavior at the output due to each source given by the step response. When convolving the step responses from various sources, the factors that contribute to correlation (bit sequence, phase delays, bps/UI) are taken into consideration.

By default, the VerifEye statistical methodology computes correlated crosstalk, but uncorrelated crosstalk can also be computed.

Uncorrelated Crosstalk

If the two lines (i.e., the victim and the aggressor channels) have the same UI, the crosstalk pulse occurs in the same place in each bit time. QE shows the pulse, but VE does not. However, if the two UIs differ, the crosstalk pulse is out of phase with the intended signal, and its effect shows up equally at any location in the eye. This circumstance is “uncorrelated crosstalk". To compute uncorrelated crosstalk, uncheck the Calculated correlated crosstalk box in the VerifEye (Statistical Eye) Analysis window, or set the solver option eye.verifeye_correlated_crosstalk to zero.  Refer to Set Up the VerifEye Analysis and VerifEye and Quick Eye Analysis Options Reference.