Exploration of differential via stub effect mitigation by using PAM4 and PAM8 line coding

Article Number
7944020
Citation
2017 IEEE 21st Workshop on Signal and Power Integrity, SPI 2017 - Proceedings: 7944020 (2017-06-07)
Contribution to Conference
2017 IEEE 21st Workshop on Signal and Power Integrity, SPI 2017  
Publisher DOI
10.1109/SaPIW.2017.7944020
Scopus ID
2-s2.0-85022182238
Publisher
IEEE
The use of spectrally efficient line codings is an important factor to facilitate high bitrates. By using PAM4 and PAM8 instead of PAM2 line coding the bandwidth of the signal is reduced considerably. On printed circuit boards vias are a major cause of signal distortion. Especially via stubs lead to resonances that degrade the transmission. By using higher order line codings with a lower fundamental frequency it is possible to operate the channel at higher data rates by keeping the fundamental frequency away from the stub resonances. In this work an extensive study using eye diagrams of differential links with via stubs is conducted to investigate the correlation of stub length and signaling performance using different line codings. It can be shown that, if the fundamental frequency of PAM2 approaches the stub notch frequency, PAM4 and PAM8 will in general improve the eye openings.
DDC Class
600: Technik