An Enhanced Eye-Opening PAM-4 with Encoding for Short-Reach Wireline Communication Systems

This paper presents a new encoding scheme for PAM-4 signaling with the aim of reducing the inter-symbol interference (ISI) caused due to the bandwidth limited channel. The proposed encoding converts any consecutive identical sym-bols (CIS) in the input data to an alternative transition, which helps to mitigate inter-symbol interference and results in wider eye opening at the receiver as compared to unencoded PAM-4. Performance of the proposed encoding is validated through transistor level simulations at 56Gb/s using two different pseudo random quaternary sequence (PRQS) data patterns across two communication channels (6dB and 9dB channel loss) in 16nm FinFET technology. Simulations show more than <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2\times$</tex> improve-ment in the vertical and horizontal eye opening with the proposed encoding scheme.