PCIe Gen6 Retimer Equalization

Equalization is the process of compensating the distortion introduced by the channel. After passing through a band-limited channel, the high frequency components of the signal are heavily attenuated which distorts the signal and spreads it into subsequent symbol periods. Implementaion of Equalization is prefered on Tx side where signal is free from noise. While equalization was implemented on the Tx side with a 3-tap FIR filter in PCIe Gen 3 through 5, it is implemented with a 4-tap FIR filter in PCIe Gen 6 as shown in Figure 1 & 2. Four consecutive pulses are multiplied with their respective coefficients and added to generate the filter output.