Magnetics Business & Technology - November/December 2024 - 30

TECH TIPS
Meeting the EMI/EMC Challenge with Noise Suppression Sheets
By Patrik Kalbermatten, Senior Manager - Distribution Promotion Product Management Magnetic, Sensor &
Actuator at KEMET Electronics Corporation
All products must be tested
for EMC compliance
before being sold and
experienced engineers
know that planning must
start in the early design
phases to be successful.
Approaches include good
design practice, simulation,
and pre-testing
although these are not
always successful, and
issues found during testing
are often mitigated by adding additional filtering or shielding
to obtain a pass.
An alternative (or additional) 'fix' involves sheets of composite
magnetic materials that can be cut, shaped, and stuck to block
EMI. These noise suppression sheets (NSS) are available
with differing permeabilities and thicknesses to suit multiple
frequencies.
Compared to metal shields, NSS are easy to use and require
no tooling. They can also wrap around wires to replace ferrite
beads. While NSS are often used tactically to address issues
found in testing, they can also be used strategically as part of a
well-considered design.
NSS overview
NSS are made by blending micron-sized magnetic material
powders in a polymer to create a composite magnetic material.
Figure 3: NSS in an RF receiver.
Designs will contain multiple interference sources, including
signals reflected from casings, openings in the case, internally
radiated noise, and even crosstalk from other sections
of the circuit. Adding multiple filters and introducing shielding
requires space, complicates the design, and adds weight and
cost. However, applying NSS is faster, simpler, and cheaper as
no real-estate or additional components are needed.
NSS for noise absorption
Given that EMC mitigation should be considered from the
inception of all design projects, NSS can be considered as part
of any solution from the outset. In addition to preventing unwanted
interference with nearby equipment, good EMC design
will prevent any system from self-interference.
Figure 1. NSS construction
The material has complex permeability (µ) comprising two
components, µ' and µ''that respectively determine the ability
to support magnetic flux and the noise absorption effectiveness.
By carefully controlling these properties, KEMET created
the FLEX SUPPRESSOR® NSS product line, that attenuates
noise signals and sustains magnetic flux from 1MHz to 40GHz.
Figure 4: NSS for ESD protection
NSS can de-sensitize receiver circuitry in wireless devices
such as mobiles, IoT nodes, and remote controls to enhance
reliability and range while reducing RF transmitter power
requirements and easing receiver design. This reduces overall
power consumption and size and extends battery life.
NSS can be applied to protect against electrostatic discharges
(ESD) that cause system failures as well as being used to
boost electromagnetic coupling between transmitters and receivers,
thereby enhancing the performance of wireless power
transfer (WPT) systems for faster charging and increased
energy efficiency.
For more info, visit www.kemet.com
Figure 2: FLEX SUPPRESSOR® NSS covers a wide frequency range
30 Magnetics Business & Technology * November/December 2024
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