Effect of Equalization Bandwidth and Linearity on NRZ and PAM4 Eye Diagram

In this paper, a study of the effect of bandwidth (BW) and linearity of a linear redriver on PAM2 and PAM4 signals is presented. Due to the robustness of PAM2, the effect of BW on the signal quality is manageable and improves with higher linearity. However, a higher than Nyquist BW is needed for PAM4 to achieve a minimum eye opening. Also, higher linearity will be needed for a PAM4 signal to achieve an acceptable eye opening across PVT (process, temperature, voltage) variations. A combination of higher BW and higher linearity makes PAM4 eye diagrams closer to the maximum achievable value. A tradeoff between linearity and BW can be considered to get the optimum eye opening in a linear redriver.