Signal Integrity Model of Multilayer PCB and Boundary Element Method Numerical Analysis
|Course||Mechanical Design and Theory|
|Keywords||Signal integrity Multilayer printed circuit board Power/ground plane Via Crosstalk Boundary element method|
Nowadays, under the trend of Electronic products are miniaturization、high speed and highdensity, which lead to the number of layers and vias are increasing in High-speed printed circuitboard (PCB). Under the condition of high frequency, the parasitic effect is more complicatedthan the low frequency, at the same time the parasitic effect has become the important factors ofaffecting the signal transmission quality in the high speed PCB. Meanwhile, the high-speedsignal through the interconnect lines will produce some signal integrity trouble, such as delay,reflection, crosstalk, attenuation and dispersion. Predicting the influence of via and modeling forvias have become very important component in the process of high-speed PCB design. Inaddition, these directly affect the success or failure of high speed digital system design.In this paper, the boundary element method was used to mode, simulate and analysisresonator structure，which is composed of power/ground plane. According to the analysis of thefield distribution within the power/ground plane, the complex3-d problems convert to2-dproblem. Study numerical method of the return path input impedance on power/ground plane,which containing some vias, shorting vias and shorting via,which are located around the signalvia. First of all, according the vias and interconnect structure on multilayer PCB to modelingequivalent circuit, using transmission line theory and PSPICE prediction crosstalk betweendifferent microstrip at the source side line. Second, using the boundary element numericalmethod to calculate the return path impedance and apply PSPICE (ADS) to simulating reflectioncoefficient and transmission coefficient. In the meantime, analyze the influence of parameters ofvia, the number of shorting via and the gap between signal via and shorting vias for signaltransmission. At last, through the HFSS to verify the boundary element method and theequivalent circuit model.The equivalent circuit model to calculate the reflection coefficient and transmissioncoefficient comparison with the3d electromagnetic simulation software HFSS, the results showthat the method is correct and effective. Due to the via is fine structure in the PCB, if usingdiscrete algorithm to calculate will be produce a lot of grid. Boundary element method onlyneeds to discrete the boundary of the PCB and via, without solving the value of the electric fieldin the PCB region, thus, this can effectively reduce the number of grid, decrease the computer’smemory and improve calculation efficiency. The most important thing is that boundary elementsuitable for any shape’s power/ground plane, so, it has more extensive applicability than cavity-model theory. Although the electromagnetic field method is more accurate, it consumesmore computer resources, the circuit method is simple, but this accuracy is low. In this paper,according to the characteristics of the field and the circuit, using this method which combine thischaracteristic of electromagnetic field and circuit,the electromagnetic problem will convert tocircuit.