An Adaptive Equalizer for 56 Gb/s PAM4 SerDes

Aiming at the problems of high bit error rate and large channel high-frequency loss in high-speed transmission, an adaptive equalizer suitable for 56 Gb/s PAM4 SerDes is designed. In order to improve the signal transmission bandwidth, PAM4 signal is used instead of NRZ signal. In order to improve the equalization effect, 4-tap FFE is used for pre-emphasis at the transmitter, and a two-stage CTLE is used for coarse equalization at the receiver. Furthermore, digital based 16-tap adaptive FFE and 1-tap adaptive DFE are used at the receiver to further reduce the bit error rate. Simulation results show that the equalizer can work at the rate of 56 Gb/s, and the eye diagram of PAM4 signal is obviously open. Compared with the traditional adaptive equalizer, it can effectively reduce the convergence time and bit error rate.