A 4-PAM adaptive analog equalizer for backplane interconnections

Increasing of data rate has created a major challenge for electronic circuits used at the interface of the backplane physical layer links. As the data rate increases above Gb/s, intersymbol interference (ISI) becomes a critical issue in received signal quality, limiting the achievable transmission speed and distance over channels. A 4-PAM (pulse amplitude modulation) adaptive analog equalizer is proposed to compensate the FR-4 PCB backplane interconnections by using a sum- feedback filter (SFF), relaxing the design requirement of the conventional analog feed-forward equalizers (FFE). Fabricated in a 0.13- mum digital CMOS technology, the analog equalizer recovers 14 Gb/s random data transmitted over FR-4 PCB copper channels.