Transition-aware feed-forward equaliser for reducing pattern-dependent jitter in four-level pulse-amplitude modulation transmitters

To reduce pattern-dependent jitter in four-level pulse-amplitude modulation (PAM-4) signalling, a transition-aware feed-forward equaliser (TFFE) is proposed. By allowing the transition time to vary according to the transition types of the PAM-4 symbols, switching jitter in TFFE-based PAM-4 transmitters can be greatly suppressed, down to the non-return-to-zero (NRZ) level. Simulation results confirm that a PAM-4 transmitter that employs a TFFE can reduce the jitter level by 0.18 unit interval peak-to-peak, and this proposed equaliser can achieve nearly identical eye height as the conventional PAM-4 feed-forward equalisers design without introducing any signal-to-noise ratio penalty.