Crosstalk analysis in high-speed serial links.(COMMUNICATIONS TEST)

The bit error ratio (BER) of a serial data stream is impacted by both jitter and noise. There are several tools that allow the visualization and measurement of jitter, such as BER contours and BER vs. decision timing, also known as the bathtub curve.

But while these measurements do a good job of validating overall channel performance, they do not necessarily provide much help when looking for the root cause of noise related channel problems. As the data rates climb above 6 Gb/s and toward 10 Gb/s, it becomes apparent that the effects of noise must be included when predicting BER.

Jitter analysis methods are well established, but methods of handling noise analysis are not broadly agreed upon. Now there is a new method of handling noise analysis in a manner similar to jitter. This approach supports tracking BER problems back to their various jitter and noise components, giving clear insight into problems and facilitating design trade-offs. It allows for the identification of the true source of channel impairments, enhancing the reliability and accuracy of BER estimations.

Jitter and Noise Measurements

Jitter has long been broken down into a number of distinct components under total jitter (TJ). This model has proved helpful for modeling and analyzing behaviors of communications circuits. However, as data rates increase, the effects of noise need to be taken into account.

By sampling the signal at two locations, a high slew-rate edge and a zero slew location, it is possible to make similar analyses for both the jitter and noise components of a signal. …

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