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90 DESIGN007 MAGAZINE I NOVEMBER 2018 In Table 3, at 1 Gbps signal transmission, the attenuation at the receiving end is due to dielectric loss. The intra-pair skew due to non- homogeneous length up to 50% of 5 inches does not have a significant impact on attenua- tion. However, at 10 Gbps, the signal attenua- tion at the receiving end is more than 5% con- tributed by the non-homogeneous length up to 40% of 5 inches. This poses a critical impact to the signal integrity at 10 Gbps and beyond. A larger intra-pair skew worsens the jitter and attenuation of the channel, which is indicated by the smaller eye width and height. Case Study 2 Simulation of the s-parameter illustrated in Figure 2 was conducted to study the impact of fiberglass materials on signal integrity. The plots of Sdd21 for microstrip and stripline are shown in Figures 7a and 7b. These plots indi- cate that with the same non-homogeneous length on the substrate, the channel on NE- glass experiences lower attenuation compared to E-glass. This is due to the fact that the dif- ference in dielectric constant values between NE-glass and resin is smaller compared to E-glass and resin. This weakens the non- homogeneous effect. The plots of Scd21 for microstrip and strip- line are shown in Figures 8a and 8b. A larger absolute magnitude of Scd21 indicates that tougher for differential be converted to com- mon mode, which is encountered by transmis- sion channel with NE-glass versus E-glass fiber. This strengthens the immunity of the channel against common-mode noise or crosstalk. As in Case Study 1, this study was also per- formed in the frequency and time domains. In these two analyses, a differential signal with a 600 mVpp amplitude at 1G bps (35 ps rise- fall time) and 10 Gbps (5 ps rise-fall time) is injected into the transmission line models listed in Table 2. The results of intra-pair skew and eye-opening are summarized in Table 4. Figure 7a: Sdd21 for microstrip. Figure 8a: Scd21 for microstrip. Figure 7b: Sdd21 for stripline. Figure 8b: Scd21 for stripline.