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
