A Comparative Study of 20-Gb/s NRZ and Duobinary Signaling Using Statistical Analysis

A statistical analysis technique for estimating bit-error rate (BER) and eye opening is presented for both non-return-to-zero (NRZ) and duobinary signaling schemes. This method enables fast and accurate BER distribution simulation of a serial link transceiver including channel and circuit imperfections, such as finite pulse rise/fall time, duty cycle variation and both receiver and transmitter forwarded-clock jitter. A comparison between 20-Gb/s NRZ and duobinary transmitters using this simulator shows that while duobinary transmission relaxes the requirements on the receiver equalizer due to the lower Nyquist frequency of the transmitted data, significant eye-opening and BER degradation can arise from clock non-idealities. The proposed statistical analysis is verified against traditional time-domain, transient eye-diagram simulations at 20-Gb/s, transmitted through measured s-parameter channel characteristics.