A fully adaptive continuous-time linear equalizer for PAM4 signaling based on a statistical algorithm (Invited paper)

This work presents a self-adaptation algorithm to automatically adjust the peaking settings of a continuous-time linear equalizer (CTLE) in a high-speed PAM4 receiver. A statistical approach is adopted to improve the robustness and flexibility of the adaptation algorithm. The PAM4 top level distribution around the peak value of several consecutive top levels guides the CTLE to attain the optimal digital settings. By performing the peak detection at the output of the equalization summer, the effect of digital equalization is inherently accounted for by the proposed algorithm. To demonstrate the effectiveness of the proposed algorithm, a PAM4 receiver employing two stages of CTLE and 1-tap feed forward equalizer (FFE) is designed to compensate up to 11.8-dB channel loss for a data rate of 56 Gb/s.