June 2015
16
I
NTERNET
-O
F
-T
HINGS
– S
YSTEMS
D
ESIGN
loss. In our device-crowded world, electro-
magnetic interference (EMI) and electromag-
netic compatibility (EMC) issues also a ect
power integrity (PI) and signal integrity (SI).
e Ansys Nexxim circuit simulator in Ansys
SIwave o ers an e cient way to design and
test memory channels for servers that power
our cloud-computing world. When this sim-
ulator is used in combination with IBIS-AMI,
or Nexxim QuickEye and VerifEye models, it
represents the leading solution for high-speed
communication channel design.
To squeeze every bit of performance, prod-
uct development teams need to use coupled
multiphysics so ware, which can analyze the
trade-o s among speed, bandwidth, signal
integrity, power integrity, thermal perfor-
mance and EMI/EMC. For example, maxi-
mizing data throughput in a smartphone may
require system engineers to focus on elec-
tromagnetic, structural, and thermal perfor-
mance of the RF shielding.
Power e ciency can be discussed from two
perspectives: power delivery and power con-
sumption. e rst one is delivering power
e ciently and safely. As an example, consider
an implanted medical device. It needs a power
source, which can be charged wirelessly,
without damaging living tissue. So, wireless
power transfer, energy harvesting, and regu-
latory compliance are key considerations for
IoT devices. On the power consumption side,
engineers need to fully model integrated cir-
cuits, IC packaging and printed circuit boards.
Low-power IC design begins with optimi-
zation of Verilog and VHDL (RTL) code.
Clock gating, memory-access optimization,
and turning o unutilized logic are simple
improvements that can make a big di er-
ence in lowering power consumption. Design
automation tools like Ansys PowerArtist can
identify the key RTL changes with the greatest
power-saving potential. Power e ciency isn’t
limited to the design of ICs.
To achieve best power e ciency, engineers
need to consider the whole system, includ-
ing antenna and wireless systems. An opti-
mized antenna system can provide a better
user experience, including increased talk time.
For example, simulation allows engineers to
model the performance of antennas in free-
space, within device enclosure, and then next
to the human head. Properly designed anten-
nas can provide 2.25 times more talk time.
e proliferation of wireless devices creates
new performance demands for antennas and
radio systems, which need to deliver unin-
terrupted connectivity. As previously noted,
antenna system designers must consider the
comprehensive characteristics of the environ-
ment in which the antenna will operate. is
can include modeling e ects such as plastic
covering over the antenna, the interaction of
a mobile handset with the human hand, or
the way an antenna is installed in an automo-
bile. With so many complex wireless systems
operating in close proximity, electromagnetic
interference can become a big issue. Consider
the design of antennas and sensors for a smart
watch. e watch band contains a biometric
sensor antenna, operating at 400MHz, and a
Bluetooth antenna, operating at 2.4GHz. Each
frequency band excites a di erent part of the
antenna requiring additional sophisticated
engineering analysis. Using nite element
(FEM) domain decomposition, 3-D method
of moment (MoM) and hybrid FEM–MoM
enables antenna engineers to quickly solve
electrically large and complex, full-wave elec-
tromagnetic models. To get a complete picture,
engineers need to examine the behavior and
scattering of radiation across time and space
using transient analysis.
Today, high-tech companies turn to advanced
lightweight, yet strong, materials to create ex-
ible mobile and wearable electronics. However,
a range of complex issues must be considered
when evaluating new materials - including
electrical conduction properties, structural
strength, and dimensional stability over time
and resistance to thermal build-up. Design for
manufacturability is also an important con-
sideration. For example, even when a smart
watch has been designed with the strongest
practical materials, the device may be damaged
due to impact. To achieve the right trade-o s
between material strength, cost and design ele-
ments, engineers can turn to simulation tools
for structural and explicit dynamics analysis to
model physical impact and drop-tests.
Manufacturing robust modern electronics
products is complicated by their complex
shapes and functions. In the smart watch
example, the electronics within the watch are
under stress due to the curvature of the wrist-
band. Understanding this issue beforehand
can help the device last longer and deliver bet-
ter user experience. In this case, the curvature
of the wristband was adjusted to reduce the
stress on the antenna.
n
Figure 3. Simulation for structural and explicit dynamics analysis to model physical impact and
drop-tests
Figure 4. Impact of shape on antenna
