Research On High-speed Signal Transmission Model Based On Board-level Design

In recent years,with the increasing demand for high-frequency circuit design,some interconnected transmission structures that were originally unaffected in low-speed digital design have also begun to cause signal integrity problems.In view of the strong electrical characteristics exhibited by the passive interconnection structure at high frequencies,based on the transmission line theory and electromagnetic theory,this paper investigates the equivalent circuit extraction method of the transmission line,and innovatively proposes a fast extraction method of equivalent capacitance parameters of through-hole channel of hierarchical model,and further integrates simulation analysis and theoretical analysis to extract the parasitic inductance of the through-hole model,so as to prepare for the simulation of signal link.Based on signal integrity issues that arise in engineering applications,this article studies key impact modules: terminations,traces,stack-ups on end-to-end passive signal links,and summarizes the practical optimization design methods and rules.In view of that,the main research work of this paper can be summarized as:1.Equivalent circuit extraction.According to the characteristics of that transmission line circuit parameters changing with frequency,we have found how to use S-parameter model measurement of the limited frequency section to predict the response of transmission line circuit parameters in the higher frequency section,so as to allow for high frequency scalability for PCB board design in advance.Aiming at the study of through-holes,a fast extraction method of equivalent capacitance parameters of through-hole channel of hierarchical model is proposed.The calculation model fully integrates the specific physical meaning of different structures.Under the specific electrical requirements,it has a most significance in the guidance of adjustment among parameters of via pad diameter,anti-pad diameter and via diameter.It also provides guidance for electrical parameter extraction on multilayer vias.Making use of that ANSYS Q3 D Extractor's equivalent circuit extraction tool and Hyperlynx's through-hole time-delay simulation,the additional inductance in the through-hole model is derived inversely.It greatly reduces the difficulty of the parasitic inductance extraction method of through-hole model,and saves the solution time.2.Aiming at solution of common signal integrity problems.It can be divided into the following aspects:1)Modeling and simulating different termination strategies to solve the reflection ringing phenomenon during signal propagation.Based on the classical reflection theory,ringing,linked with three factors(transmission line delay vs.rise time ratio,termination resistance and transmission line impedance)is found by modeling.Then LTspice simulation software is used to analyze the effect of different termination strategies to solve the actual overshoot problem.That provides a technical solution reference for suppressing the reflection overshoot problem.For crosstalk problem of microstrip and strip-line coupling,specific noise voltage expressions are given.It is found that power/ground plane of the strip-line can reduce the inductive crosstalk on the far side of the coupled victim line.Finally,five common wiring methods of PCB are studied in combination with the actual situation,so as to guide the PCB design from a practical perspective.2)Research on different via connection methods.While different layers are interconnected by a via,the return loss of the front and back ends of via and the insertion loss of the via are mainly studied.And it is found that the via stub is the biggest factor affecting the signal conducted on the via.3)Research on sensitivity of characteristic impedance change.Based on the empirical formula of microstrip and strip-line characteristic impedance design,key design parameters affecting the impedance of microstrip and strip-line are found.The study has compared the sensitivity of its impedance changes to various parameters,and has obtained very meaningful guidance for impedance design.4)Research on design of laminated structure.Two different types of crosstalk on line-ground coupling design(intra-layer crosstalk and interlayer crosstalk)are discussed,based on Hyperlynx simulation software.On the other hand,a comparison of the network impedances of different degrees of coupling between pairs of power/ground layers was studied.The thesis summarizes the application range of copper-clad technology and points out the significance of its effect after completion.Based on the research results,the preliminary summary can be used for the sequence planning of the power layers,the ground layers,and the signal layers to ensure the scientific design of the stack.