Modeling and simulation of high speed serial transmitter based on duobinary signal modulation
With the rapid development of the big data industry,the data transmission rate of the SerDes system continues to increase,but the high-frequency attenuation suffered during high-speed signal transmission brings stronger inter-symbol interference(ISI),which greatly reduces the signal quality and hinders further increase in transmission rate.To suppress the signal loss of intersymbol interference during transmission,in addition to improving the circuit structure,another feasible path is to concentrate the signal energy in the lower frequency and reduce the high frequency attenuation while keeping the signal baud rate unchanged,aiming to alleviating the Intersymbol interference caused by non-ideal channels.The modulation principle of Duobinary signal modulation is discussed and compared with NRZ coding,the transfer function of Duobinary signal modulation is analyzed,and the system modeling and simulation of 56 Gb/s high-speed serial transmitter is carried out with Cadence based on Duobinary modulation.The transmitter includes parallel PRBS generator,tree structure MUX,3-tap forward feedback equalizer(FFE),non-ideal channel and other circuit modules.Theoretical analysis shows that,compared with the traditional non-return-to-zero code(NRZ),the power spectrum of the Duobinary coded signal at the same rate is more concentrated in the low frequency components.The simulation results show that the eye diagram of the Duobinary coded signal after passing through the non-ideal channel is clearer than that of the NRZ signal at the same rate,and suffers less inter-symbol interference.Therefore,as the modulation method of the SerDes system,the Duobinary signal has advantages in resisting channel interference.
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