Circuit Bandwidth Requirements for NRZ and PAM4 Signals

Wireline links present various circuit stages in the signal path, requiring sufficient bandwidth so as to contribute negligible intersymbol interference. This paper analyzes the effect of circuit bandwidth limitations on NRZ and PAM4 waveforms and quantifies the necessary excess bandwidth when the data format is changed from the former to the latter so as to double the data rate. It is observed that the PAM4 eye width is particularly sensitive, demanding at least a fourfold increase in the bandwidth.