Oscilloscope News

TLC PAM413 April 2015 – Teledyne LeCroy launched a PAM4 Signal Analysis software for its real-time oscilloscopes. This new set of analysis tools makes essential eye, jitter and noise measurements on all three eye openings of a PAM4 signal, a requirement for engineers who are designing next-generation electrical and optical links that seek to double data transfer rates by leveraging PAM4 signaling.

PAM4 encodes two bits of information per symbol rather than one by using a 4-level signal. This doubling comes at a price of increased signal complexity as compared to 2-level NRZ signaling. The PAM4 eye diagram contains 3 eye openings rather than one, and includes 12 types of transitions rather than two. Engineers must understand how their transmitters, channels, and links affect PAM4 eye quality, and quantify the degree of eye closure due to timing jitter and noise as a function of bit error ratio (BER).

Traditional serial data analysis tools found in oscilloscopes are designed to work with NRZ signals, forcing new measurement tools and techniques to be created for analysis of 4-level signaling. The new PAM4 Signal Analysis software is specifically designed for 4-level signaling and makes eye, jitter and noise measurements on all three eye openings of the PAM4 signal. Total jitter and noise are decomposed into random and deterministic components to give a full accounting of the jitter and noise behavior. In addition to quantifying jitter, and noise and eye height/width, the software allows users to understand the root causes of jitter by displaying a rich set of visualizations including histograms, tracks, spectra, and bathtub curves.


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