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Title:A Comparative Study of Duobinary and NRZ Modulation for High-Speed I/O
Author(s):Koh, Yee Lih
Abstract:High-speed serial I/O links are limited in throughput due to intersymbol interference (ISI) and noise. At high data rates, on-board traces are bandlimited due to frequency dependent skin effect and dielectric losses. In order to analyze the effectiveness of using different modulation schemes in improving the reliability of serial links, we conduct a system level study to compare duobinary modulation with the traditional non-return-to-zero (NRZ) modulation scheme. The advantage presented by duobinary is that the modulation scheme only requires half the bandwidth required by NRZ. As a result, signal attenuation at high frequencies is avoided and noise enhancement is reduced. Nevertheless, the use of duobinary comes with a penalty at the receiver as the received signal consists of three signaling levels while NRZ has only two. Analytical results are presented to show when one scheme proves to be advantageous over the other. Comparisons for the modulation schemes are done across data rates using a measured 20-in FR4 channel, and across channel attenuations at 10 Gb/s. These comparisons are done using receive side equalization, comparing both modulation schemes using a linear equalizer as well as a decision feedback equalizer. In this thesis, we find that the advantages of utilizing duobinary appear at high data rates and high channel attenuation.
Issue Date:2008-01
Publisher:Coordinated Science Laboratory, University of Illinois at Urbana-Champaign
Series/Report:Coordinated Science Laboratory Report no. UILU-ENG-08-2201, DAC-107
Genre:Technical Report
Sponsor:SRC / SRC 05-HJ-1305
Date Available in IDEALS:2018-04-04

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