Electromagnetic Compatibility Analysis And Optimization Of High-speed PCIe Serial Channel

With the continuous development of communication technology,data transmission speed has been rapidly improved.In the 1990 s,data speeds of 100 Mbps were considered "high",while the most advanced PCIe5.0 technology has reached speeds of 32 Gbps.With the increase of transmission speed,the rise time of signals has entered the picosecond era,and signals are more sensitive to the interference factors on the serial channel.Therefore,it is necessary to conduct a comprehensive study on the EMC of the differential transmission channel.Differential transmission line is the basis of PCIe serial channel.Firstly,the advantages and disadvantages of different coupling modes of differential lines and the influencing factors of far-field radiation are analyzed.Then on the basis of the single line crosstalk analysis method,the crosstalk coefficient and the mixed mode S parameter of the differential pair are derived and through the frequency domain and channel simulation,the influence of the distance between the differential pair and the coupling degree of the differential line on the crosstalk between the differential pair is analyzed,the relationship between the length of the differential line and the near-end and far-end crosstalk of the differential pair is analyzed.Finally,the same method is used to derive the crosstalk coefficient between the difference pair and the single line,and the effect of the distance between the difference pair and single lines on the crosstalk between them is analyzed by electromagnetic field simulation.In the era of low speed,FR4 can be thought of evenly distributed,however,when the signal transmission speed reaches the GHz,must consider the effect of glass fiber,in this paper,the glass fiber model is established,and the influence of glass fiber effect on the differential signal is analyzed through electromagnetic field simulation,and the glass fiber effect is optimized.AC coupling capacitor is an important part in PCIe serial channel.This paper establishes the model of AC coupling capacitor,analyzes the influence of pad of AC coupling capacitor,and it is optimized.Via is the most widely used PCB passive components,this paper established the 3D model of a differential via.,and the via stub and via pads is optimized.Finally,the return path of differential via is analyzed,the importance of the ground via to common impedance is pointed out,and the number and location of the ground via are analyzed,the best arrangement of the ground via is obtained.In this paper,the differential transmission line,differential via,AC coupling capacitance on the PCIe serial channel are analyzed and optimized.The signal quality is improved and the electromagnetic radiation is reduced by the study,so the paper has practical value.