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NOVEMBER 2018 I DESIGN007 MAGAZINE 91 In Table 4, at 1-Gbps signal transmission, the attenuation at the receiving end is due to dielectric loss. The intra-pair skew due to the non-homogeneous length up to 10% of 5 inches using either NE-glass or E-glass does not have a significant impact on attenuation. However, at 10 Gbps, the signal attenuation at the receiv - ing end is more than 5% contributed by the non-homogeneous length up to 10% of 5 inches for E-glass versus NE-glass. This poses a criti- cal impact on the signal integrity at 10 Gbps and beyond. A larger intra-pair skew worsens the jitter and attenuation of the channel, as indicated by the smaller eye width and height respectively. Summary In multi-gigabit transmission, NE-glass fiber with denser weave such as 3313 shall be applied in PCB substrate to minimize the attenuation and intra-pair skew, which strengthens the signal integrity. The attenuation due to fiber weave effect shall be kept below 5% to allow more headroom for channel loss contributed by other factors, such as dielectric loss, copper surface roughness, etc. DESIGN007 References 1. G. Romo, C. Nwachukwu, R. Torres, W. Baek, & M. Schauer. "Stack-up and routing optimization by understanding micro- scale PCB effects." DesignCon, 2011. 2. B. Olney. "Beyond Design: Material Selection for SERDES Design." The PCB Design Magazine, September 2013. 3. H. Li, D. Eng, C. Tang, & P. Westbrook. "Low dielectric glass fibre development: New printed circuit board base materials." European Journal of Glass Science and Technology, 2013. 4. Isola. "PCB Material Selection for High-speed Digital Designs." Microwave Journal, 2013. 5. E. Chua, J. Zhang, & K. See. "A study on fibre weave effect on intra-pair skew of differential lines using analytical approach." IEEE, 2017. 6. Altera Corporation. "PCB Dielectric Material Selection and Fiber Weave Effect on High-Speed Channel Routing." Intel, 2011. Chang Fei Yee is a hardware engineer with Keysight Technologies. His responsibilities include embedded system hardware development, and signal and power integrity analysis. Table 4: Summary of skew and eye-opening. which graphene switches from conducting to insulating. Now, by using quantum simulation methods that model electron interactions explicitly, Yunoki and his colleagues have discovered that graphene instead transitions to a more exotic nonmagnetic topological state called a Kekulé-like dimerized nonmagnetic insulator, which could have interesting technological applications. "This discovery only became possible using our quan- tum Monte Carlo simulations, for which RIKEN's K com- puter was essential due to the extremely heavy computa- tions involved," notes Yunoki. (Source: RIKEN) By using the powerful K supercomputer to simulate with unprecedented accuracy what happens to graphene as it is stretched, RIKEN researchers have discovered a new state of the material. Graphene is being intensively investigated for appli- cations ranging from electronics and energy storage to optics and even tissue engineering. But graphene still needs to be integrated with non-conducting or insulating elements to provide useful functionality. For many years, Seiji Yunoki from the RIKEN Center for Computational Sci- ence has been seeking to ascertain the conditions under New Insulating State Found in Stretched Graphene

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