A Novel High-Speed Adaptive Duobinary Digital Detector Based on the Feed-Forward Equalizer and the Maximum Likelihood Sequence Detector for Wireline Transceivers

To solve the high bit error rate (BER) problem of conventional 56-Gb/s nonreturn-to-zero (NRZ) transceivers under high-insertion loss (IL) channels, this study proposes a high-speed adaptive duobinary (DB) digital detector based on the feed-forward equalizer (FFE) and the maximum likelihood sequence detector (MLSD). In this detector, adaptive FFE is combined with channel characteristics to generate DB signals and complete equalization, thus extending the transmission bandwidth and eye height and allowing a larger sampling phase offset. The parallel MLSD is used to complete the detection and decoding of DB signals to reduce the BER. An adaptive algorithm is proposed to avoid the long convergence time of the conventional zero-forcing (ZF) algorithm applied to the DB detector, so that it can be applied to various bit rates and IL channels. In this study, the verification of this DB detector is accomplished at 56 Gb/s. The platform based on a 56-Gb/s analog front-end chip (AFEC) and field-programmable gate array (FPGA) proves that the detector can work well in 12-56 Gb/s and multiple IL channels. The BER was less than 2e-8 at 56 Gb/s on -42-dB channel loss at 28 GHz. The structure can be well used for higher rate transceivers, such as 112 Gb/s.