Design And Implementation Of Signal Integrity Analysis Module For Broadband Digital Oscilloscope

There are many signal integrity problems in high speed transmission.In order to optimize the performance of transmission link,the signal integrity analysis function is added to the oscilloscope to realize the simulation and signal quality test of high-speed serial transmission link.Signal integrity analysis module is divided into two parts: simulation and test.The signal integrity simulation part provides the simulation of the whole process of high-speed transmission link,including the five functions of sending end equalization(pre-emphasis / de-emphasis),fixture de-embedding,channel simulation,receiving end equalization(CTLE/FFE/DFE)and clock restoration.The problem of signal integrity mainly comes from the transmission line loss of the channel,so channel simulation is the core of signal integrity simulation.Since S parameter represents the transmission response of the channel,the data modeled in channel simulation is derived from S parameter.Fixture may be introduced in the process of testing S parameters,which results in that the measured S parameters contain the S parameters of fixture,so the function of embedding shall be provided to eliminate the influence of fixture.The purpose of pre-weighting/de-weighting at the transmitter is the same as that of equalization at the receiver,which is to compensate the channel loss and improve the signal quality.According to the principle of equalization,this paper provides the corresponding simulation algorithm.The clock is the basis of receiving end analog-to-digital conversion,and is also the basis of eye map and dither measurement in oscilloscope.Signal integrity test part provides eye chart and jitter two indicators to detect signal quality.For eye chart measurement,this paper takes the clock recovered from clock as the standard cutting signal,and then superimposes the obtained waveform fragments to form a two-dimensional matrix containing probability information,from which an eye chart with color temperature can be drawn and the parameters of the eye chart can be calculated.For the jitter analysis,due to the complexity of jitter components,this paper analyzes jitter from multiple perspectives of time domain,frequency domain and statistical domain,and provides the measurement of traditional jitter parameters(TIE,CJ,CCJ)in time domain.In the frequency domain,the data correlation jitter is extracted first,and then the spectrum diagram of the remaining jitters is distinguished by the threshold to realize the decomposition of random jitter and periodic jitter.In the statistical domain,the Dirac model is constructed according to the jitter histogram,and the total jitter,random jitter and deterministic jitter are deduced based on the tail fitting.This design uses the broadband digital oscilloscope platform based on Windows system to complete the simulation of high-speed serial transmission link and the test of signal quality,which enriches the advanced measurement and analysis functions of the oscilloscope,and is of great significance to the development of the advanced measurement functions of domestic oscilloscope.