Abstract
In recent years, with the development of the communication industry, the need to use Ethernet switches to transmit big data has become more urgent, and its protocol standards are iterating towards higher return loss, wider bandwidth, lower impedance fluctuations and insertion loss. Based on the research of high-speed backplane with a single channel 25 Gbps transmission rate, a novel double grounded planar strip coplanar waveguide design is presented, which significantly improved return loss to 20 dB and reduced insertion loss, which meet the loss standard of 100GBASE-KR4. The resonant cavity model of transmission line reference plane is improved by introducing vias and the parameters of vias in the reference plane are studied to reduce the impact of resonance, which improved the transmission −1 dB bandwidth to 60 GHz. Based on equivalent circuit analysis of differential vias’ joint reverse pad, the parameters related to the differential vias are studied, the impedance fluctuation is reduced to 100 ± 3 Ω, which is 70% better than the impedance fluctuation standard (100 ± 10 Ω) of 100GBASE-KR4. After optimizing the mathematical model of strip coplanar waveguide, reference plane and differential vias, we built a simulation model of the backplane passive link which met the 100GBASE-KR4 backplane Ethernet specification. In the actual test, it was found that the optimized model can improve the link performance.
Highlights
With the rapid development of the global Internet, with cloud computing, mega data and 5G communication services gradually entering people’s lives, there are greater requirements for data exchange rate and bandwidth
We study the modeling of transmission line, reference plane and vias, and conduct the optimization design including: (1) in order to correct the loss, modeling and analysis of transmission line based on strip coplanar waveguide; (2) modeling and analysis based on strip coplanar waveguide transmission line reference plane which increased passband width; (3) modeling and analysis of differential vias which reduced impedance fluctuations; (4) the passive link model of high speed backplane is established
Three aspects are simulated and optimized: (1) the best height of strip coplanar waveguide metal plate is determined by simulation, the insertion loss was reduced and the return loss was increased to 20 dB, which meet the 100GBASE-KR backplane Ethernet specification; (2) the factor of the transmission line reference plane affecting the resonant frequency are deduced, and the optimal parameters are determined by simulation, so that the signal transmission bandwidth of −1 dB can reach 60 GHz; (3) an equivalent circuit model is established for the differential vias, and the simulation results show that impedance fluctuation with the best via parameters is 100 ± 3 Ω
Summary
With the rapid development of the global Internet, with cloud computing, mega data and 5G communication services gradually entering people’s lives, there are greater requirements for data exchange rate and bandwidth. The concept of backplane Ethernet first appeared in the IEEE 802.3ap standard issued by IEEE in 2007. IEEE proposed the concept of backplane Ethernet, and released 10GBASE-KR backplane Ethernet specification [1] for the proposed concept of backplane Ethernet. The development of Ethernet is even more amazing, IEEE has successively released. The 100GBASE-KR backplane Ethernet specification has begun to challenge the single channel rate of 25 Gbps. With the development and maturity of Ethernet specification, it can be used in switches, routers and other network communication equipment, and be applied to embedded switching equipment such as automation of power distribution networks and intelligent traffic road monitoring systems
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