Research And Design Of Signal Integrity Based On High-speed Backplane Passive Link

In recent years,with the rapid development and popularization of technologies such as the Internet of Things,big data,artificial intelligence,and 5G communications,electronic devices and products in related fields have also continued to increase and increase in the direction of higher speed,higher bandwidth,and higher density.development of.At present,the single-channel rate of high-speed serial links has been increased from 5Gbps and 10 Gbps to 25 Gbps or even 56 Gbps.With the continuous improvement of the transmission rate and clock frequency in the circuit,the tendency of high-speed signals to be affected by signal integrity problems such as loss,reflection,resonance and crosstalk in transmission is becoming more and more serious.For highspeed digital signals with a transmission rate of Gbps,the effective frequency spectrum has been extended to microwave or even millimeter wave frequency bands,and has shown obvious electromagnetic wave characteristics during transmission in complex interconnection systems.At this time,the analysis of signal integrity problems is essentially a solution A complex boundary value problem of electromagnetic fields.For solving the boundary value problem of electromagnetic field,the traditional analytical formula method is no longer applicable.At present,the relevant electromagnetic effects are generally analyzed by the method of finite element analysis.In order to achieve the high-rate transmission requirements of 56 Gbps,the transmission lines and vias in the backplane passive link need to have lower transmission loss and higher transmission bandwidth.The-3d B bandwidth needs to meet at least the 56 Gbps transmission base frequency of 28 GHz.The transmission lines,vias,and reference planes in the backplane passive link are the key components of the entire passive link,and they are representative of the current high-speed circuit design.Therefore,based on the research and design of a high-speed backplane with a transmission rate of 56 Gbps,this paper conducts modeling research on the transmission lines,vias and reference planes in its passive links,and optimizes the design.The main research contents of this paper are as follows:(1)A strip coplanar waveguide transmission line model with dual ground reference planes is studied,and the equivalent permittivity and characteristic impedance of the transmission line model are mathematically modeled.Then based on experimental research and combined with finite element simulation methods,a simulation prototype of the transmission line was constructed and verified by simulation.The simulation results showed that the-3d B bandwidth of the strip coplanar waveguide transmission line can reach 60 GHz.(2)In order to explore the relationship between the reference plane of the transmission line and its resonant frequency,based on the theory of rectangular resonant cavity,a coplanar waveguide transmission line resonant cavity model composed of a grounded reference plane is studied.Through theoretical analysis of the model,The mathematical expression of the resonant frequency of the model has been revised,and the calculation result of the resonant frequency of the transmission line obtained by the revision is closer to the actual situation.(3)Based on experimental research and combined with the finite element simulation method,a belt-shaped coplanar waveguide transmission line model was established.Through the finite element simulation tool,the width of the reference plane on the adjacent side of the coplanar waveguide and the diameter and number of grounding vias on the reference plane were three The influence of the parameters on the resonance and bandwidth of the transmission line is analyzed.By increasing the diameter and the number of vias,the transmission line can be free from resonance in the DC?60GHz frequency band,and the-1d B bandwidth reaches 60 GHz,which is higher than the 40 GHz that does not consider the via parameter model.Up 50%.(4)Based on the equivalent circuit analysis method,the single-ended and differential vias were modeled and studied,and the parasitic capacitance of the vias was mathematically characterized,and the influence of the added vias in the link on the link impedance was explored.Based on experimental research,it is analyzed that the joint anti-pad design method of the circular anti-pad splicing with the rectangular anti-pad can reduce the impedance fluctuation of the differential via to 100?±3%,which is 7%higher than the standard requirement of 100?±10%.At the same time,by optimizing the stump length of the differential via,the number of return ground holes and the teardrop design parameters,the loss and impedance curve of the differential via is optimized and improved.(5)Finally,the impedance matching design of the connector and the transmission line interconnection through the Klopfenstein graded transmission line is studied,and the co-simulation model of the backplane passive link is built,and the simulation of the backplane passive link is based on the previous research.The model is optimized for design.The simulation results show that through the overall co-simulation optimization,the passive link parameters of the backplane can meet the 100BASE-KR4 backplane Ethernet specification,ensuring that the link can realize 100 G Ethernet applications.Finally,the actual circuit design is guided by simulation,and the measured results show that the relevant optimization method reduces the link loss and improves the link performance.