Per-bit equalization approach for multi-level signal in high-speed design

A new feed forward equalization (FFE) method for four-level pulse-amplitude modulation signal (PAM4) is introduced. The new FFE method equalizes the signal by bit instead of by symbol which provide the better high frequency compensation in some situations. The advantages and limitations of per bit FFE is discussed and compared against per symbol FFE. Several test cases are presented to show the advantages and limitations of the new FFE method.