48 The PCB Design Magazine • August 2017
• High-frequency harmonics can beat with
the resonant frequency of the plane pairs creat-
ing a rough wave effect which can cause total
system failure
• Solving signal integrity issues is always the
best starting place to minimizing EMI.
• To improve signal integrity, hence EMI,
one needs to slow down the rise time of the sig-
nal to reduce the high-frequency components.
This is easily achieved by placing a termination
resistor in series with the transmission line at
the source.
• It is always good design practice to allow
space for a series terminator by adding a zero-
ohm resistor to the critical interconnects to fu-
ture-proof the design.
PCBDESIGN
References
1. Barry Olney's Beyond Design columns:
Material Selection for SERDES Design, Mas-
tering 'Black Magic' with Howard Johnson's
Seminars, Signal Integrity Part 1, New Function-
ality Improves Designer's Productivity, Plane
Crazy Part 2.
2. Eric Bogatin, Signal and Power Integrity
Simplified, Rule of Thumb #1: Bandwidth of a
signal from its rise time.
3. Howard Johnson, Martin Graham. High-
speed Digital Design.
Barry Olney is managing director
of In-Circuit Design Pty Ltd (iCD),
Australia, a PCB design service
bureau that specializes in board-
level simulation. The company
developed the iCD Design Integrity
software incorporating the iCD
Stackup, PDN and CPW Planner. The software can
be downloaded from www.icd.com.au. To read
past columns, click here.
Design and nanomanufacturing have collided in-
side a Northwestern University laboratory.
An interdisciplinary team of researchers
has used
mathematics and machine learning to design an
optimal material for light management in solar cells,
then fabricated the nanostructured surfaces simulta
-
neously with a new nanomanufacturing technique.
"We have bridged the gap between design and
nanomanufacturing,"
said Wei Chen, the Wilson-
Cook Professor in Engineering Design and professor
of mechanical engineering in Northwestern's Mc
-
Cormick School of Engineering.
"The concurrent design and processing of nano-
structures paves the way to avoid trial-and-error
manufacturing, increasing
the cost effectiveness to
prototype nanophotonic devices," said Teri
Odom,
Charles E. and Emma H. Morrison Professor of
Chemistry in Northwestern's Weinberg College of
Arts and Sciences.
Researchers are currently in
-
terested in nanophotonic mate-
rials for light absorption in ultra-
thin, flexible solar cells. The same
principle could also be applied to implement color
into clothing without dyes and to create anti-wet
surfaces. For solar cells, the ideal nanostructure sur-
face features quasi-random structures, meaning the
structures appear random but do have a pattern.
To bypass the issues of nano-lithography,
Odom
and Chen manufactured the quasi-random struc-
tures with wrinkle lithography, a new nanomanu-
facturing technique that can rapidly transfer wrinkle
patterns into different materials to realize a nearly
unlimited number of quasi-random nanostructures.
"Importantly
, the complex geometries can be
described computationally with only three param
-
eters — instead of thousands typically required by
other approaches," Odom said. "We then used the
digital designs in an iterative search
loop to deter
-
mine the optimal nanowrinkles for a desired out-
come."
Next,
the
team plans to ap-
ply its method to other materi-
als, such as polymers, metals,
and oxides, for other photonics
applications.
Simultaneous Design and Nanomanufacturing
Speeds Up Fabrication
WHEN LEGACY PRODUCTS NO LONGER PERFORM
