Analysis Of The Worst-Case Data Patterns And Eye Diagram Based On MER For High-Speed Nonlinear Links

With the rapid increase of high-speed link data throughput and the continuous increase of signal rate,the signal integrity problem in the link has become more prominent.When engineers design links,accurately predicting system performance has become a challenging problem.For linear time-invariant link,the single-bit responses(SBR)can be used to predict the link response well,and this method can greatly improve the simulation efficiency compared with transient simulation.For links with asymmetry between the rising edge and the falling edge,the SBR method is extended to the double-edge responses(DER)method.However,as the system faces more and more serious nonlinearities,neither SBR nor DER can accurately characterize the link response.In order to capture the effect of nonlinearity on the system response,some people have proposed the multiple-edge response(MER),which can construct multiple rising and falling edges according to the previous bit pattern to obtain more accurate results of the nonlinear link.The worst-case eye diagram reflects the performance of the link in the worst case.In order to obtain the worst-case eye diagram of the link and the corresponding worst-case data pattern,engineers usually use SPICE models or convolution to perform transient simulations.Although these two methods can obtain accurate results,they are very time-consuming for complex high-speed links.Driven by this demand,fast time domain simulation algorithms are developing rapidly.The fast time domain simulation technology and peak distortion analysis method based on the assumption of linear time invariance can quickly calculate the worst-case data pattern of the link and the link performance under the worst-case data pattern,and then evaluate the link performance,but this method is not suitable for more serious nonlinear links.In order to solve the above problems,this thesis first takes a high-speed serial link as an example to introduce the basic structure of the link and related signal integrity issues,by building a non-linear and controllable high-speed link in Simulink,three fast time-domain simulation techniques are analyzed;Secondly,this thesis proposes an analysis method based on the MER method for solving the worst-case pattern and the worst-case eye diagram of a nonlinear link.By establishing a dynamic matrix to track the worst cumulative inter-symbol interference voltage,the thesis introduces the detailed calculation process,and uses a second-order algorithm as an example to illustrate;then this article simulates the proposed algorithm on the basis of a nonlinear high-speed link from the first-order to the tenth-order results,an actual test environment was built,and the method was tested and verified on a differential cable.By comparing the results of simulation verification and test verification,analyzing the worst-case eye diagram and worst-case pattern data under different orders,the accuracy and effectiveness of this method are verified.The calculation of the bad-case eye diagram and the worst-case pattern provides an effective and accurate estimation method.Finally,this thesis develops a simulation tool for the worst-case eye diagram of nonlinear links based on the MATLAB User Graphical Interface(MATLAB-GUI),which embeds algorithms of calculating nonlinear worst-case data pattern and worst-case eye diagram of different orders in the tool,and introduces the interface of the tool and its use process are introduced in detail.