Analysis Of Signal Integrity Of High-speed Backplane Connectors

With the development of semiconductor technology, in high speed digital system, clock frequency has increased to GHz as well as transmission rate.Effective frequency of high speed signal has reached microwave-band even millimeter wave band. Due to the transmission line effect, high speed signal will be affected by signal integrity(SI) problems and the design method of mature MHz speed system has been unable to apply for high speed product.Signal integrity problems is that the amplitude and phase of signal which mainly caused by Return Loss, Insertion Loss and Crosstalk, can not ran up to the signal receiver’s request. High speed backplane connector is the bridge of parent Board and daughter Board and plays a vital role on communications between the Boards. According to the demand of high-speed servers and high-speed digital system, the high-speed backplane connector rate has reached 54 Gbps in foreign country. But there is little study about the signal integrity of 25 Gbps high-speed backplane connector in China.A high-speed backplane connector which’s rate up to 25 Gbps will be studied in this subject, especially its signal integrity parameters analyzed through simulation and testing. With the help of electromagnetic simulation software HFSS which has a good accuracy on high speed backplane connector simulation, some important parameters can achieve like high speed backplane connector’ time domain reflection impedance, return loss, insertion loss, near-end crosstalk(NEXT) and far-end crosstalk(FEXT). High speed backplane connector TDR impedance is sensitive to parasitic capacitance and parasitic inductance, especially in its male that located in cavity and female. Thanks to dielectric parameters existing frequency dependence and dimensions the key of high speed backplane connector, which’s impact on TDR impedance, loss is relatively large, this research optimization focused on dimensions, dielectric constant ? and loss tangent angle δ.After optimization simulation analyzed on high speed backplane connector, it is necessary to measure by Vector Network Analyzer(VNA) in this research study. Because the measuring system includes test Boards and VNA, it should be calibrated by the method of Thru-Reflect-Line(TRL). Comparing the results of simulation and measurement, it will be found that the minimum measured 84Ω of TDR impedance is 3Ω less than the minimum simulation result 87Ω and the minimum measured-1.25 d B result of insertion 1oss reduces to the simulation result-2.34 d B, which meeting the requirements of above-3d B. The measured results of NEXT and FEXT both achieve the standard of less than-30 d B. Finally, analyzing the results of measured and simulation, the measured signal integrity parameters are consistent with the trends of curve of the simulation results, which verified the rationality of design and reliability.