Application of Electromagnetic Interference Shielding 1 (Project Paper)

i
APPLICATION OF ELECTROMAGNETIC INTERFERENCE SHIELDING
Project Paper
Submitted to
College of Engineering and Computer Science
Southern University and AM College
A project submitted in partial fulfillment of the requirements for
The degree of
Master of Engineering in Electrical Engineering
By
Vernon Dutch Jr.
Baton Rouge, Louisiana
May 2016

i
APPLICATION OF ELECTRONIC INTERFERENCE SHIELDING
Dutch Jr., Vernon Dion
APPROVED BY:
___________________________________________
Fred Lacy, PhD
Faculty Advisor
Committee Chair Professional
____________________________________________
Zhengmao Ye, PhD
_____________________________________________________
Raife Smith, PhD
_____________________________________________________
Damien Ejigiri, PhD
Graduate School
Dean of Graduate School, Southern University
-

ii
Copyright by
Vernon Dutch Jr.
All rights reserved
2016

iii
Abstract
APPLICATION OF ELECTROMAGNETIC INTERFERENCE SHIELDING
by
Dutch, Vernon Dion
Southern University and A&M College
Professor, Dr. Fred Lacy
This project was to designed to investigate the high-value, environmentally friendly and low-
cost conducting composites for protection against the effects of electromagnetic interference and
electrostatic discharge. Shielding of electromagnetic waves involves utilizing metals and other
conductive materials. Shielding also incorporates the carbon fibers polymer matrix, as well as hybrid
systems with combinations of both fillers. An oscilloscope was used to measure the range of absorbed
frequencies (8 MHz to 56 MHz) when small shields of copper or carbon fiber are utilized. The
Arduino circuit board generates a consistent range of oscillations up to 16 MHz and Raltron crystal
oscillators can generate up to 40 MHz with the appropriate circuit setup. These oscillators were
measured with a magnetic probe to determine the efficiency of the shielding materials. The analyzed
results showed that generally, carbon fiber has better shielding effectiveness in comparison to copper
plating when both have a similar thickness and are shielding similar low frequencies.

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Table of Contents
Chapter 1.....................................................................................................................................1
Electromagnetic Fields and Waves .............................................................................................1
Electromagnetic Wave Propagation............................................................................................4
Electromagnetic Radiation Spectrum..........................................................................................7
Chapter 2...................................................................................................................................10
Electromagnetic Interference...................................................................................................10
Electromagnetic Shielding Theory ............................................................................................ 12
Polymer Composites ............................................................................................................... 15
Chemical Modification……………………….……………………………………………………………………………………….17
Chapter 3...................................................................................................................................19
Reflection Aspect for Shielding ................................................................................................ 19
Absorption Aspect of Shielding ................................................................................................ 20
Multiple Reflection Occurrence in Shielding ............................................................................. 21
Skin Effect............................................................................................................................... 21
Chapter 4...................................................................................................................................24
Crystal Oscillators.................................................................................................................... 24
Importance of the Magnetic Probe........................................................................................... 26
Near Field and Far Field .......................................................................................................... 28
Application of Magnetic Probe ................................................................................................ 30
Chapter 5...................................................................................................................................33
Experimental Procedure ......................................................................................................... 33
Analysis of Experiment............................................................................................................ 36
Works Cited............................................................................................................................ 41

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Acknowledgment
I would like to thank both my mother, Bernadette Dutch-Griffin and step-father John Griffin,
for their continued support and prayers.

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Chapter 1
Introduction
1.1 Electromagnetic Fields and Waves
An electromagnetic (EM) field, is generated when charged particles, such as
electrons, are accelerated. All electrically charged particles are surrounded by electric fields.
When charged particles are in motion they produce magnetic fields. When the velocity of a
charged particle changes, an EM field is produced (10).
Electromagnetic fields were initially discovered in the 19th century, when physicists
noticed that electric arcs (sparks) could be reproduced at a distance, with no connecting wires
in between. This discovery led scientists to believe that it was possible to communicate over
long distances without wires (24). The first radio transmitters made use of electric arcs and
were known as "spark transmitters and receivers”.
To put these discoveries into context, during 1820 the only magnetism known was
that of iron magnets and of "lodestones", natural magnets of iron-rich ore. It was believed
that the inside of the Earth was magnetized in the same fashion, and scientists were greatly
puzzled when they found that the direction of the compass needle at any place slowly shifted,
decade by decade, suggesting a slow variation of the Earth's magnetic field. Obviously, there
was inquiry as to how an iron magnet can produce such changes. Edmond Halley (later
renowned for his cosmologic discoveries) had proposed that the Earth contained a number of
spherical shells, one inside the other, each magnetized differently, each slowly rotating in
relation to the others.
Another example of the advances in magnet science was Hans Christian Oersted. He

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was a professor of science at Copenhagen University and his experiments ultimately lead to
the principle known as Oersted Law stating that a steady electric current creates a magnetic
field around it. He noticed that the needle of a compass next to a wire carrying current turned
so that the needle was perpendicular to the wire. Oersted investigated and found the
mathematical law which governs how strong the field was, which is now called Oersted's
Law. Oersted's discovery was the first connection found between electricity and magnetism,
and the first of two laws that link the two; the other is Faraday's law of induction. These two
laws became part of the equations that govern electromagnetism, Maxwell's equations.
Oersted rules for a straight wire carrying a steady DC current are listed.
 The magnetic field lines encircle the current-carrying wire
 The magnetic field lines lie in a plane perpendicular to the wire
 If the direction of the current is reversed, the direction of the magnetic force reverses.
 The strength of the field is directly proportional to the magnitude of the current.
 The strength of the field at any point is inversely proportional to the distance of the
point from the wire.
Understanding a magnetic field requires knowing its direction in relation to the material
around it. The direction of the magnetic field at a point and the direction of the arrowheads
on the magnetic field lines is also the direction that the "North pole" of the compass needle
points and can be found from the current by the right hand rule. This simple rule dictates that
if the right hand is wrapped around the wire so the thumb points in the direction of the
current (conventional current, flow of positive charge), the fingers will curl around the wire
in the direction of the magnetic field.
As important as Oersted’s contribution has been to the fields of physics and

3
engineering, his rule has a significant disadvantage relating to time dependent systems.
Oersted's law only holds for steady currents, which don't change with time. Naturally, this
means it only applies for DC electric circuits, with no capacitors or inductors. It can be seen
that it fails for time varying currents by considering the case of a circuit consisting of a
battery charging a capacitor through a resistor. It can be verified experimentally that the
current in this circuit creates a magnetic field, yet any closed curve encircling the conductor
can be spanned by a surface passing between the capacitor plates, through which no current
passes, from which the equation would give zero magnetic field. Ørsted's law was modified
by Maxwell to cover the case of time-varying currents by adding a new source term called
displacement current, resulting in the Ampere-Maxwell equation.
Ampere's law with Maxwell's addition states that magnetic fields can be generated in
two ways: by electric current (this was the original "Ampère's law") and by changing electric
fields (this was "Maxwell's addition"). Maxwell's addition to Ampère's law is particularly
important: it shows that not only does a changing magnetic field induce an electric field, but
also a changing electric field induces a magnetic field (18). Therefore, these equations allow
self-sustaining "electromagnetic waves" to travel through empty space. This is more easily
verified by the theory in Maxwell equations explained in more detail later.
The speed calculated for electromagnetic waves, which could be predicted from
experiments on charges and currents, exactly matches the speed of light; indeed, light is one
form of electromagnetic radiation (as are X-rays, radio waves, and others). Maxwell
understood the connection between electromagnetic waves and light in 1861, thereby
unifying the theories of electromagnetism and optics.
In most electronic applications, EM fields are generated by alternating current (AC)

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in electrical conductors. The frequency of the AC can range from one cycle in thousands of
years (lowest extreme) to trillions of cycles per second (highest extreme). The standard unit
of EM frequency is the hertz, abbreviated Hz. Larger units are often used. This unit follows
the metric conventions of increase, so frequency of 1,000 Hz is one kilohertz (kHz); a
frequency of 1,000 kHz is one megahertz (MHz).
The wavelength of an EM field is related to the frequency (9). The frequency (f) of an
EM wave is specified in megahertz and the wavelength λ is specified in meters (m), so within
free space, the two are related as wavelength is inversely proportional to frequency.
Figure 1 This a diagram of the relationship between wavelength and amplitude. (4)
This experiment required the use of an oscilloscope to view the sine wave produced from
crystal oscillators. The oscilloscope measures amplitude by peak to peak voltage (𝑉𝑝−𝑝),
which must be converted into the decibel unit for the shielding equations used in later stages.
𝑑𝐵 𝑉 = 20𝑙𝑜𝑔10(𝑉𝑝−𝑝 ∗ 0.3535) (1)
1.2 Electromagnetic Wave Propagation
Electromagnetic waves are capable of traveling through the vacuum of outer space.
The mechanism of energy transport through a medium involves the absorption and emission
of the wave energy by the atoms of the material. Once EM wave impinges upon the atoms of

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a material, the energy of that wave is absorbed. The absorption of energy causes the electrons
within the atoms to undergo vibrations. After a short period of vibrational motion, the
vibrating electrons create a new electromagnetic wave with the same frequency as the first
electromagnetic wave. While these vibrations occur for only a very short time, they delay the
motion of the wave through the medium. Once the energy of the electromagnetic wave is re-
emitted by an atom, it travels through a small region of space between atoms. Once it reaches
the next atom, the electromagnetic wave is absorbed, transformed into electron vibrations and
naturally re-emitted as an electromagnetic wave. While the electromagnetic wave will travel
at a speed of light denoted as c (3 x 108 m/s) through the vacuum of inter-atomic space, the
absorption and re-emission process causes the net speed of the electromagnetic wave to be
less than c (10).
The propagation of an electromagnetic wave, is normally generated by a discharging
capacitor or an oscillating molecular dipole. The current oscillates at a frequency f, which is a
characteristic of the circuit. The electromagnetic disturbance that results is propagated with
the electronic E and magnetic B vectors vibrating perpendicularly to each other and also to
the direction of propagation Z. The frequency f, is determined by the oscillator (10), while
the wavelength is determined by the oscillation frequency divided by the velocity of the
wave.

6
Figure 2 Propagation of electromagnetic wave requires a discharge or oscillation (17)
As the current oscillates up and down in the spark gap, at the characteristic circuit frequency
f, a magnetic field is created that oscillates in a horizontal plane. The alternating magnetic
field, due to the interaction will induces an electric field so that a series of electrical and
magnetic oscillations combine to produce a formation that propagates as an electromagnetic
wave.
The electric field in an electromagnetic wave vibrates with its vector of force growing
stronger and then weaker, pointing in one direction, and then in the other direction,
alternating in a sinusoidal pattern. At the same frequency, the magnetic field oscillates
perpendicular to the electric field. The electric and magnetic vectors, reflecting the amplitude
and the vibration directions of the two waves, are oriented perpendicular to each other and to
the direction of wave propagation. The velocity of the resulting electromagnetic wave can be
deduced from the relationships defining the electric and magnetic field interactions (21).
Maxwell's equations prove that velocity equals the speed of light in a vacuum c divided by
the square root of the dielectric constant 𝜀 of the medium times the magnetic permeability 𝜇
of the medium.
The actual speed of an electromagnetic wave through a material medium is dependent

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upon the optical density of that medium. Different materials cause a different amount of
delay due to the absorption and re-emission process. Furthermore, different materials have
their atoms more closely packed and thus the amount of distance between atoms is less.
These two factors are dependent upon the nature of the material through which the
electromagnetic wave is traveling. It is possible to determine the density of a new metal or
plastic by determining the speed of an electromagnetic wave through the material.
1.3 Electromagnetic Radiation Spectrum
The realm of EM field energy is called the electromagnetic radiation spectrum. It is
inclusive of radio waves, microwaves, infrared light, visible light, ultraviolet light, X rays
and gamma rays. The difference between these manifestations of electromagnetic radiation is
due to different magnitudes of the frequency and wavelength of the oscillations. These two
quantities are related in that the speed of light c is equal to the dot product of frequency and
wavelength. An electromagnetic wave is associated with changing electric and magnetic
fields that travel through a particular medium and transfer energy from one location to
another. It should be noted that with electromagnetic radiation, decreasing the wavelength
results in increasing the frequency.
Astronomers who study radio waves tend to use wavelengths or frequencies. Most of
the radio part of the EM spectrum falls in the range from about 1 cm to 1 km, which is 30
gigahertz (GHz) to 300 kilohertz (kHz) in frequencies. The radio is a very broad part of the
EM spectrum. Infrared and optical astronomers generally use wavelength. Infrared
astronomers use microns (millionths of a meter) for wavelengths, so their part of the EM
spectrum falls in the range of 1 to 100 microns. Optical astronomers use both angstroms
(0.00000001 cm, or 10-8 cm) and nanometers (0.0000001 cm, or 10-7 cm). Using nanometers,

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violet, blue, green, yellow, orange, and red light have wavelengths between 400 and 700
nanometers. Since this range is a miniscule part of the entire EM spectrum, the light that
human eyes can perceive is only small fraction of all the EM radiation.
Figure 3 Electromagnetic Spectrum (5)
The wavelengths of ultraviolet, X-ray, and gamma-ray regions of the EM spectrum
are very small. Instead of using wavelengths, astronomers that study these portions of the EM
spectrum usually refer to these photons by their energies, measured in electron volts (eV).
Ultraviolet radiation falls in the range from a few electron volts to about 100 eV. X-ray
photons have energies in the range 100 eV to 100,000 eV (or 100 keV). Gamma-rays then are
all the photons with energies greater than 100 keV.
The regions (or bands or types) of the electromagnetic spectrum are referred to as
bands or types in most conventional literature. It is important to note that there are no exact
or defined boundaries between the bands of the electromagnetic spectrum. The rainbow
represents the entire spectrum of visible light, so bands have a tendency to fade into each

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other like the colors in a rainbow. Radiation of each frequency and wavelength (or in each
band) has a mix of properties of the two regions of the spectrum that bound it. A strong
example of is how red light resembles infrared radiation in that it can excite and add energy
to some chemical bonds and indeed must do so to power the chemical mechanisms
responsible for photosynthesis and the working of the visual system.
EM radiation helps to create a more productive world, especially in communication
technology. However, their hazards are very prevalent and should be always be considered in
design choices. At present, scientists around the world have done many investigations and
statistical analysis for the effect of EM radiation on human health. The results show that the
possibility of cancerization is closely related to long term exposure to low frequency EM
radiation. Researchers have found that EM radiation could influence the central nervous
system, cardiovascular system, endocrine system, and genital system (13).
Incidentally, a signal from a certain device may interfere with others. One method to
reduce the interference is applying EM wave absorption materials to shield signals from
spurious generating sources. There is also the growing recognition that installing EM wave
absorption materials in electronic equipment helps to inhibit noisy signals. In military science
and technology, the absorption materials are utilized as “stealth” function materials (13).

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Chapter 2
2.1 Electromagnetic Interference
Electromagnetic interference shielding (EMI) is an undesired electromagnetic (EM)
induction triggered by extensive use of alternating current/voltage which tries to produce
corresponding induced signals (voltage and current) in the nearby electronic circuitry,
thereby altering its original signal (9). The mutual interference among electronic gadgets,
business machines, process equipment, measuring instruments and appliances lead to
disturbance or complete breakdown of normal performance of appliances. EM disturbances
across communication channels, automation, and process control may lead to loss of time,
energy, resources and also adversely affect human health. Strictly due to these restrictions,
use of mobile phone is restricted inside robotic operation theatres or during
onboard/flight which may trigger series of electronic failures and or system malfunction in
the egregious circumstances. Therefore, some shielding mechanism must be provided to
ensure undisturbed functioning of devices even in the presence of external electromagnetic
(EM) noises. For efficient shielding action, a shield should possess either mobile charge
carriers (electrons or holes) or electric and/or magnetic dipoles which interact with the
electric E and magnetic H vectors of the incident EM radiation (19). In the recent past, a
wide variety of materials (15) have been used for EMI shielding with a broad range of
electrical conductivity σ, good electromagnetic attributes such as permittivity 𝜀 or
permeability μ and engineered geometries. The designing a EMI shielding with a certain
level of attenuation, meeting a set of physical criteria, maintaining economics and regulating
the involved shielding mechanism is not a straight forward task and involves complex
interplay of intrinsic properties (σ and μ) of shield material and logical selection of extrinsic

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parameters. Therefore, to touch the theoretically predicted shielding performance of a
materials and to satisfy stringent design criteria, knowledge of shielding theory, set of
governing theoretical equations, important design parameters and relevant measurement
technique becomes a prime prerequisite.
Frequent usage of wireless signal devices indicates the need to protect components
against electromagnetic interference (EMI) in order to decrease the chances of these
components adversely affecting each other. The effects of electromagnetic interference can
be reduced or diminished by positioning a shielding material between the source of the
electromagnetic field and the sensitive component. This protection may be achieved by
making the housing of electronic components electronically conducting.
Electrical conductivity is a considerable factor for an EMI shielding material. This is
due to the physical phenomenon that electric fields and magnetic fields induce currents in the
electrically conducting shielding material. As a result of this induction, these currents
generate counteracting fields which weaken (or ideally cancel) the originally applied fields
(19). It is preferential that the external fields stay outside the shielding material, and internal
fields stay inside. Effective EMI shielding is composed of reflection and absorption
contributions, both the conductivity in the volume of the protecting material as well as the
thickness of the material may be of importance.
The practical applications of shielding have certain limits, since the extent of
shielding is also subject to the size and shape of openings in the shield. For example, if a
component produces a frequency of 1 GHz, the opening must be less than 12 mm for
effective EMI shielding. Another aspect related to EMI shielding is the protection against
electrostatic discharge (ESD) in electronic devices. ESD is the uncontrolled transfer of static

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charge between two objects with different electrical potential. For ESD protection surface
conductivity is important, to allow a fast and controlled discharge of static charge. Protection
against ESD is used in a wire mesh encircling an inner core conductor such as coaxial cable
for transmission of radio and television frequency signals.
2.2 Electromagnetic Shielding Theory
EMI shield is essentially a barrier to regulate the transmission of the EM wave across
its bulk. In power electronics, term shield usually refers to an enclosure that completely
encloses an electronic product or a portion of that product and prevents the EM emission
from an outside source to deteriorate its electronic performance (19). Conversely, it may also
be used to prevent an external susceptible (electronic items or living organisms) from internal
emissions of an instrument’s electronic circuitry.
Shielding is the process by which a certain level of attenuation is extended using a
strategically designed EM shield. The shielding efficiency is generally measured in terms
of reduction in magnitude of incident power/field upon transition across the shield.
Mathematically shielding effectiveness (SET) can be expressed in logarithmic scale with the
proven expressions. This experiment focuses
𝑆𝐸 𝑇 ( 𝑑𝐵) = 𝑆𝐸 𝑅 + 𝑆𝐸𝐴 + 𝑆𝐸 𝑀 = 10log10(
𝑃 𝑇
𝑃𝐼
) = 20log10(
𝐸 𝑇
𝐸𝐼
) = 20𝑙𝑜𝑔10(
𝐻 𝑇
𝐻𝐼
)
(2)
In this equation, the term PI (EI or HI) and PT (ET or HT) are the power (electric or
magnetic field intensity) of incident and transmitted EM waves respectively. The E and H
variables are not used in this experiment because the focus is on the shielding effectiveness
variables. The three mechanisms of reflection (R), absorption (A) and multiple internal
reflections (MIRs) contribute towards overall attenuation with SER, SEA and SEM
respectively.

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When applying SE to actual technologies, it is vital to understand the physics behind
how shielding material operates. According to the distance r between the radiating source
and the observation point, an electromagnetic radiative region can be divided into three parts
relative total wavelength 𝜆 of the electromagnetic wave. The region within the distance 𝑟 <
𝜆
2𝜋
is the near field while the distance 𝑟 <
𝜆
2𝜋
is the far field. Between the two regions, as
the distance 𝑟 =
𝜆
2𝜋
is the transition region.
Figure 4 Schematic representation of EMI Shielding for Incident Waves (19)
When selecting the appropriate material for particular shielding application, it is
imperative to have in-depth knowledge of both intrinsic & extrinsic parameters on which
shielding effectiveness depend along with suitable theoretical relations correlating them with
reflection, absorption and multiple-reflection loss components. Shielding effectiveness is

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best explained by using the transmission line theory and the plane wave shielding theory (7).
Assuming a uniform plane wave characteristic by E and H that vary within a plane only with
x direction. This is explained with Maxwell’s curl equation.
𝑑𝐸
𝑑𝑥
= −𝑗𝜔𝜇𝐻 𝑎𝑛𝑑
𝑑𝐻
𝑑𝑥
= −( 𝜎 + 𝑗𝜔𝜀) 𝐸
(3)
As expressed previously, σ is the conductivity, ε is the permittivity of the material
and ω is the angular frequency. The variable of 𝜀0 is the vacuum permittivity and the 𝜀 𝑟 is the
relative permittivity of the material. Likewise, 𝜇 𝑜 is the vacuum permeability and 𝜇 𝑟 is the
relative permeability of the material.
Figure 5 Electromagnetic wave propagation within a material. (19)

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2.3 Polymer Composites
Due to their high electrical conductivity, metals are particularly suitable as shielding
material against electromagnetic fields. This can be a self-supporting full metal shielding, but
also a sprayed or painted applied conducting coating (such as nickel) on a supporting
material such as plastic. Another option is the incorporation of metal (preferably stainless
steel) powder or fibers as conducting filler in a plastic matrix.
However, there are a few drawbacks to using metal as a shielding material. The
weight of the ‘heavy’ metal can be an issue in the case of full metal shielding and plastic
matrices with high metal filler content, especially in applications where mass should be as
low as possible. Furthermore, metals are prone to corrosion. In order to produce metal
coatings, at least two processing techniques have to be applied, one for support and the other
for coating. Applying both techniques is usually significant in cost. Since the application
techniques are also systematic, it is challenging to apply these coatings onto complicated
shaped objects and maintain long-term adhesion.
The most practical solution to problems using metal coatings is by substituting with a
different means of coating. It involves incorporating small volume fractions of non-metal,
electrically conducting fillers in a non-conducting plastic matrix by means of compounding
(injection molding or extrusion) as a one-step process (6). Housings for electronic products
(computers, communication devices) and business equipment (including devices for payment
processing) are often made of engineering plastics. The standard issue for shielding is that
plastics generally have effective electrical insulating properties, demonstrated in commercial
products useful as insulation for electric wires. The insulation of typical electrical
conductivity is less than 10-14 Siemens/cm and therefore these engineering plastics lack the

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capability shield electronic devices from electromagnetic radiation. For most industrial EMI
shielding, the conductivity should be higher than 10-2 Siemens/cm.
The method of filling a matrix of engineering plastic with an electrically conducting
material combines the availability of a housing made of shielding material with the
advantages of traditional compounding of this composite. The most prolific advantages
include the usage of existing compounding equipment, so no additional investments have to
be made for manufacturing. The creation of these matrix shields can be performed with
relative ease of by implementing small, complex shapes in a one-step process and allowing
several fillers to be incorporated.
Traditionally, metal or carbon black particles have been used as electrically
conducting filler materials. A high level of these fillers can be detrimental for the density and
surface quality of the material, the costs and mechanical properties of the molded product,
and may cause wear to the processing equipment. Material production industries are
developing novel filler materials such as intrinsically conducting polyaniline polymers and
conducting carbon nanotubes, with a filler content that is as low as possible (6). In this way,
conductivity will be provided to the material while the original plastic processing properties
will remain the same. When the concentration of electrically conducting particles in a
composite exceeds a certain level, recognized as the percolation limit, the particles come into
contact with each other and form a continuous path in the material for electrons to travel. In
this way, the composite material has become electrically conducting. The conductivity of the
filler material will be the upper limit for the electrical conductivity of the entire composite.
The percolation limit varies with the shape of the conducting particles. For traditional
spherical shaped fillers at a random distribution, approximately 10 to 20% has to be added

17
before the composite will be electrically conducting. The higher the aspect ratio (length-to-
width ratio) of the particles, the lower the concentration for percolation occurrence. Carbon
nanotubes (CNT) with a diameter of a few nanometers and a length of micrometers (a high
aspect ratio) can form a conducting network at much lower volume fractions than cheaper,
traditional fillers such as carbon fiber and carbon black.
Multiple walled carbon nanotubes (MWCNT) are best described as multiple layers of
graphite rolled in on themselves, and are known to conduct electricity. For intrinsically
electrically conducting plastics, conjugated polymers form the basis. These are polymers
with alternating single and double carbon-carbon bonds in their chains. Common examples
of intrinsically conducting polymers are polyacetylene, polyaniline and polypyrrole. The
primary advantage of MWCNT is there importance in developing large-scale, commercially
applicable production processes. These processes allow new products that contain conducting
plastics to perform more efficiently than standard plastics. MWCNT is used as a filler
material because of its conductivity, weight reduction, cost reduction and production time,
with improved balances of physical and electrical properties.
2. 4 Chemical Modification
A chemical approach to modifying carbon fibers was to process the inherently
conducting polyaniline and the non-conducting polymer matrix at the same time. The
problem is that the well-conducting emeraldine salt form of polyaniline, resulting from an
emeraldine base doped with an acid which will not feasibly melt (via injection molding or
extrusion), and hence can be dispersed only in the matrix as conducting hard particles with
relatively low aspect ratios.
For the final product to become electrically conducting, this would require a high

18
concentration of polyaniline particles, which is not desirable due to the high material costs. In
order to manage these impasses, it is anticipated that polyaniline would form better
conducting mixtures at lower filler fractions if a continuous network together with the matrix
polymer could be established. The chemical modification of polyaniline and usage of
additives improves the conducting polymer with a lower filler content and result in a higher
level of conductivity.
Quantum mechanics theory, specifically orbital hybridization, best describes chemical
bonds in nanotubes. The chemical bonding of nanotubes is composed entirely of covalent
bonds, similar to those of graphite. These bonds, which are stronger than the sp3 found in
alkanes, provide nanotubes with their unique strength. Moreover, the various combinations of
the rolling angle and radius also determine the many unusual properties of nanotubes, which
are valuable in nanotechnology, electronics, optics and other fields of materials science and
technology.

19
Chapter 3
3.1 Reflection Aspect of Shielding
To maintain reflection for the radiation of the shield, the shield must have mobile
charge carriers which includes electrons or holes (7). These charge carriers interact with the
electromagnetic field in the radiation. As a result, the shield has a tendency to be electrically
conducting, yet a high conductivity is not required. Electrical conductivity is not the
scientific criteria for shielding, as conduction requires connectivity in the conduction path
(more formally known as percolation). However, shielding is enhanced by connectivity and
metals are still generally used for EMI shielding. The free electrons in metal are what make
them ideal for reflection. As explained previously, metal plating is bulky, so coatings made
via electroplating, electroless plating, and vacuum deposition are more commonly used for
shielding.
The reflection loss is related to the relative impedance mismatch between the shield’s
surface and propagating wave. The magnitude of reflection loss under plane wave (far field
conditions) can be expressed with the appropriate equation. The shielding effectiveness
equation (SER) includes 𝜇 as the magnetic permeability, 𝑓 is the frequency, 𝜀0 is the vacuum
permittivity and 𝜇0 as the vacuum permeability respective to free space.
𝑆𝐸 𝑅 ( 𝑑𝐵) = 20𝑙𝑜𝑔10 (
𝜂0
4𝜂𝑠
) = 20𝑙𝑜𝑔10
(
√
𝜇0
𝜀0
4√2𝜋𝑓𝜇
𝜎 )
(4)
All shielding equations all reach their respective solutions in terms of decibels (dB). For any
given material with a stable atomic structure (i.e. fixed σT and μr) SER decreases with
increase in frequency.

20
3.2 Absorption Aspect of Shielding
The subsequent attribute for shielding is the property of absorption (7). The shield
must contain electric or magnetic dipoles so that significant absorption of radiation is
possible. It interacts with electromagnetic fields in the radiation. The electric dipoles are
usually provided in materials with a high dielectric constant. The magnetic dipoles require
material that have a high value of magnetic permeability. Magnetic permeability can be
enhanced by reducing the magnetic domain walls by using multiple layers of magnetic film.
Loss of absorption is due to the product of conductivity and permeability. The loss of
reflection is a function of the ratio of conductivity over permeability. The conductivity is
respective to the electrical conductivity of copper, while relative magnetic permeability is the
property being referenced. Increasing frequency causes a decrease in reflection loss and an
increase in absorption loss.
As an electromagnetic wave pass through a medium its amplitude
decreases exponentially. This decay or absorption loss occurs because currents induced in
the medium produce ohmic losses and heating of the material. The magnitude of
absorption term (SEA) in decibel (dB) can be expressed with the following equation.
𝑆𝐸𝐴 (𝑑𝐵) = 20𝑙𝑜𝑔10 𝑒
𝑡
𝛿
(5)
It is important to know that absorption requires t for thickness and 𝛿 for skin depth of a given
material. The absorption loss increases with increase in frequency. Therefore, a good
absorbing material should possess high conductivity and high permeability, and sufficient
thickness to achieve the required number of skin depths even at low frequency.

21
3.3 Multiple Reflection Occurrence in Shielding
In addition to the aforementioned properties, multiple reflections are also very
important to shielding. This refers to various surfaces or interfaces in the shield. This
mechanism requires the presence of large surface area or interface area in the shield. An
example of a shield with large interface area is a composite material containing filler (7),
which has a large surface area. The loss resulting from multiple reflections can be ignored
when the distance between reflecting surfaces or interfaces is sizable in comparison to skin
depth.
If the shield is thin, the reflected wave from the second boundary is re-reflected from
the first boundary and returns to the second boundary to be reflected continuously. The
attenuation due these multiple internal reflections can be expressed mathematically.
𝑆𝐸 𝑀 = 20𝑙𝑜𝑔10 (1 − 𝑒
−
2𝑡
5 ) = 20𝑙𝑜𝑔10|(1 − 10
𝑆𝐸 𝐴
10 )|
(6)
Therefore, it can be seen from the above expression that SEM is closely related to absorption
loss (SEA). SEM is also important for porous structures and for certain type of filled
composites or for certain design geometries. It can be neglected in the case of a thick
absorbing shield due high value of SEA so that by the time the wave reaches the second
boundary, it is of negligible amplitude. For practical purposes, when SEA is ≥ 10 dB, SEM can
be safely neglected. Usually SEM is important only when metals are thin and are used at very
low frequencies (normally in kHz range). However, for highly absorbing materials or at very
high frequencies (normally GHz), the condition of |SEA| ≥ 10dB gets satisfied and re-
reflections can be safely ignored.

22
3.4 Skin Effect
Losses resulting from reflection, absorption, and multiple reflections are commonly
expressed as dB (decibels). Furthermore, absorption loss is proportional to the thickness of
the shield (20). The skin effect occurs when electromagnetic radiation at high frequencies can
only penetrate the near surface region of an electrical conductor. The electric field of a plane
wave penetrating a conductor exponentially decreases with an increase depth into the
conductor. The skin depth formula is as follows, with frequency f, free space times the
relative permeability 𝜇0 𝜇 𝑟 = 𝜇 and σ as the electrical conductivity.
𝛿 =
1
√ 𝜋 ∗ 𝑓 ∗ 𝜇 ∗ 𝜎
(7)
As frequencies increase, conduction begins to move from an equal distribution through the
conductor cross section toward existence almost exclusively near the surface. Depending on
the conductor bulk resistivity (δs), at sufficiently high frequency all the RF current is flowing
within a very small thickness at the surface. Furthermore, the current concentrates nearest to
the surface that abuts the highest relative dielectric constant. Lower bulk resistivity result in
shallower skin depths.
Figure 6 Example of the skin depth of a micro-strip wafer (20)
In the case of a micro-strip layout, the current concentrates nearest to the substrate dielectric
material, although current does also concentrate at the other surfaces as well (redder regions).
For a solid wire, the current concentrates on the outer surface. For this reason, when skin

23
depth is shallow, the solid conductor can be replaced with a hollow tube with no perceivable
loss of performance. Choice of a plating material can degrade performance (increase
attenuation) if its bulk resistivity is greater than that of the copper. Most common conductors
have a relative permeability near 1, so for copper, aluminum, etc., a µ value of 4π* 10-7 H/m
can safely be assumed. Magnetic materials like iron, cobalt, nickel, mumetals, and permalloy
can have relative permeability of hundreds or thousands.

24
Chapter 4
4.1 Crystal Oscillators
There are many different electronic devices that produce EMI. A common method
of troubleshooting for EMI is by analyzing an electronic board capable of emitting waves
from its oscillator component. The specific board being used for this project is the Arduino
UNO board. Arduino is an open-source prototyping platform based on easy-to-use hardware
and software (3). Arduino boards are able to read inputs such as light on a sensor, a finger on
a button, or a text message and turn it into an output. These outputs can vary from activating
a motor, turning on an LED, or simply responding with a text message statement. The board
can be programmed by sending a set of instructions to the micro-controller on the board (3).
Performing specific functions requires using the Arduino programming language and the
Arduino Software integrated development environment (IDE). This experiment requires the
crystal oscillator component on the Arduino board. The oscillator on the Arduino has a
maximum frequency of 16 MHz. Due to this restriction, Raltron crystal oscillators were
measured in order to evaluate the shield effectiveness over a range of frequencies. These
oscillators can input into a circuit board and range from 20 MHz to 40 MHz.
Figure 7 This is an Arduino Uno board. The 16 MHz oscillator is indicated in the circled area. (3)
A crystal oscillator is an electronic oscillator circuit that uses the mechanical

25
resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a
precise frequency. This frequency is commonly used to keep track of time, as in quartz
wristwatches, to provide a stable clock signal for digital integrated circuits, and to stabilize
frequencies for radio transmitters and receivers. The most common type of piezoelectric
resonator used is the quartz crystal, so oscillator circuits incorporating them became known
as crystal oscillators, but other piezoelectric materials including polycrystalline ceramics are
used in similar circuits. Most are used for consumer devices such as wristwatches, clocks,
radios, computers, and cellphones. Quartz crystals are also found inside test and
measurement equipment, such as counters, signal generators, and oscilloscopes.
A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a
regularly ordered, repeating pattern extending in all three spatial dimensions. Almost any
object made of an elastic material could be used like a crystal, with appropriate transducers,
since all objects have natural resonant frequencies of vibration. For example, steel can be
used to conduct sound traveling at high velocity. Steel was often used in mechanical filters
before quartz. The resonant frequency depends on size, shape, elasticity, and the speed of
sound in the material. High-frequency crystals are typically cut in the shape of a simple,
rectangular plate. Low-frequency crystals, such as those used in digital watches, are typically
cut in the shape of a tuning fork. For applications not needing very precise timing, a low-cost
ceramic resonator is often used in place of a quartz crystal.
When a crystal of quartz is properly cut and mounted, it can be made to distort in an
electric field by applying a voltage to an electrode near or on the crystal. This property is
considered to be electrostriction or inverse piezoelectricity. When the field is removed, the
quartz generates an electric field as it returns to its previous shape, and this can generate a

26
voltage. The result is that a quartz crystal behaves like an RLC circuit, composed of an
inductor, capacitor and resistor, with a precise resonant frequency.
Quartz has the further advantage that its elastic constants and its size change in such a
way that the frequency dependence on temperature can be very low. The specific
characteristics depend on the mode of vibration and the angle at which the quartz is cut
(relative to its crystallographic axes). Therefore, the resonant frequency of the plate, which
depends on its size, does not change much. This means that a quartz clock, filter or oscillator
remains accurate.
4.2 Importance of the Magnetic Probe
The magnetic field probe is a tool used in conjunction with an oscilloscope or
spectrum analyzer. It detects the emitted waves and is very beneficial in the troubleshooting
for EMC compatibility. Electromagnetic compatibility (EMC) is the branch of electrical
engineering concerned with the unintentional generation, propagation and reception of
electromagnetic energy which may cause unwanted effects such as electromagnetic
interference (EMI) or even physical damage in operational equipment (6). There are two
different types of emissions the magnetic probe can detect: conducted emissions and
radiation emissions.
The term conducted emissions refers to the mechanism that enables electromagnetic
energy to be created in an electronic device and coupled to its AC power cord. Similarly, to
radiated emissions, the allowable conducted emissions from electronic devices are controlled
by regulatory agencies. Most electronics producers will ensure that a product passes all
radiated emissions regulations. However, a product that fails a conducted emissions test
cannot be legally sold in the United States. The primary reason that conducted emissions are

27
regulated is that electromagnetic energy that is coupled to a product’s power cord can find its
way to the entire power distribution network that the product is connected to and use the
larger network to radiate more efficiently than the product could by itself. There are other
electronic devices that can then receive the EMI through a radiated path direct electrical
connection. The frequency ranges where conducted emissions are regulated is typically lower
than the frequency range where radiated emissions are regulated. The longer wavelengths
where conducted emissions are a problem need a much larger antenna to radiate and receive
EMI than the shorter wavelengths studied for radiated emissions.
The term radiated emissions refers to the unintentional release of electromagnetic
energy from an electronic device. An electronic device can generate electromagnetic fields
that unintentionally propagate away from the device’s structure. Radiated emissions are
usually associated with non-intentional radiators, however intentional radiators can also have
unwanted emissions at frequencies outside their intended transmission frequency band.
Allowable radiated emissions from electronic modules are regulated by various organizations
and agencies. Electronic devices that have copious amounts of radiated emissions will have
interference with their normal operation or the operation of other devices in close proximity.
EM radiation is classified into two modes: differential and common. Differential
mode radiation is the result of normal operations through circuit loops. Larger loops will emit
stronger harmonic emissions. Radiation for differential mode can be modeled in small loops
antennas. Magnetic field probes are normally used to detect differential mode noise. This
project will primarily focus on this differential mode radiation. Common mode radiation
results from parasitic occurrences in the circuit and voltage drops in the conductor. It is
difficult to understand and control since it is not intentionally designed into the system. The

28
most frequent appearance of common mode radiation is from cables and the radiation can be
modeled as a dipole or monopole driven by noise voltage. Current probes or electric field
probes are needed to detect common mode radiation.
Figure 8 Differential Mode Radiation (15)
Figure 9 Common Mode Radiation (15)
4.3 Near Field and Far Field
An electromagnetic field characteristics change depending on the distance from the
antenna. This varying field is typically divided into two segments—the near field and the far
field. Understanding the differences is important for EMI testing and creating appropriate
shields for electronic devices.
The near field region is mostly a function of the properties of the source. An object
with high current and low voltage yields a magnetic field. An object with high voltage and
low current produces an electric field. The ratio of an E and H field are not constant, so they

29
are considered independently for near field calculations. There is no formal definition for the
near field, since it depends on the type of application and the antenna. The most agreed upon
definition submits that the near field is less than one wavelength (λ) from the antenna.
In the far field region, the nature of the EM fields is normally predictable. The
predictability is dependent on the source, the distance from the source, and the properties of
the material between the source and the receiver. Similar to the near field, there is no specific
point for the beginning of the far field. It is possible that it can be 2λ, 3λ or 10λ from the
antenna. Another definition indicates that it starts at 5λ/2π, while other sources mandate that
it depends on the largest dimension of the antenna D or 50D2/λ. For electronic
measurements, the fuzzy boundary between near and far field initiates at 2D2/λ. The simplest
definition is that the far field begins where the near field leaves off, or as indicated earlier,
λ/2π. The distance of the probe from the emitter is defined as r.
𝑀𝑎𝑔𝑛𝑒𝑡𝑖𝑐 𝑆𝑜𝑢𝑟𝑐𝑒 𝑜𝑓 𝐸𝑚𝑖𝑠𝑠𝑖𝑜𝑛 ∶ 𝑍 𝑤 = 120𝜋
𝑟
√𝑟2 + 1
(8)
𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑒 𝑆𝑜𝑢𝑟𝑐𝑒 𝑜𝑓 𝐸𝑚𝑖𝑠𝑠𝑖𝑜𝑛 ∶ 𝑍 𝑤 = 120𝜋
√𝑟2 + 1
𝑟
(9)
In the H-field, the wave impedance starts low and increases. In the E-field, the wave
impedance starts high and then decreases. This change in wave impedance happens because
as the distance from the source increases each field begins to produce its complimentary
field. The E and H fields support and regenerate one another as their strength decreases
inversely as the square of the distance (1/r2) as described by Maxwell.

30
𝐺𝑎𝑢𝑠𝑠 𝐿𝑎𝑤 ∇ ∗ 𝑬 =
𝜌𝑣
𝜀
𝐺𝑎𝑢𝑠𝑠 𝐿𝑎𝑤 𝑓𝑜𝑟 𝑀𝑎𝑔𝑛𝑒𝑡𝑖𝑠𝑚 ∇ ∗ 𝑯 = 0
Faraday′
s Law ∇ 𝑥 𝑬 = −𝜇
𝑑𝑯
𝑑𝑡
Ampere′
s Law ∇ 𝑥 𝐻 = 𝑱 + 𝛿
𝑑𝑬
𝑑𝑡
(10)
While Maxwell's equations (along with the rest of classical electromagnetism) are
extraordinarily successful at explaining and predicting a variety of phenomena, they are not
exact, but approximations. In some special situations, they can be noticeably inaccurate.
Examples include extremely strong fields such as Euler–Heisenberg Lagrangian and
extremely short distances referenced in vacuum polarization. There are various incidents that
occur in the world even though Maxwell's equations predict them to be impossible, such as
the quantum entanglement of electromagnetic fields such as quantum optics. All the apparent
phenomenon involving individual photons, such as the photoelectric effect, Planck's law, and
single-photon light detectors would be difficult or impossible to explain if Maxwell's
equations were exactly true, as Maxwell's equations do not involve photons specifically. To
account for these outlier situations, the most accurate predictions needed to supersede
Maxwell's equations by new laws in quantum electrodynamics.
4.4 Application of the Magnetic Probe
The magnetic field (or H-field probe) is essentially an electrically small loop antenna
that detects emitted waves. Because the loop is small, the current is constant around the loop
with zero phase around the loop. The shape of the loop does not matter, rather the
importance is on the current and the area. A magnetic field passing through the probe loop
generates a voltage, which is known as Faraday's Law. The induced voltage is proportional

31
to the rate of change of magnetic flux through a circuit loop.
The diameter of the loop determines the sensitivity of the probe, the frequency
response, and the spatial resolution. The larger the loop, the more H field lines the loop will
cross hence better inductive coupling which results in higher sensitivity. However, larger
loops cause a lower resonance frequency and usable range. Smaller loops give higher
frequency response but they remain less sensitive, resulting in lower inductance.
Deciding on whether to use a shielded or unshielded probe for detecting EMI varies
with different circumstances. Shielded probes are used for many EMC applications and are
prevalent for electric field shielding. They prevent shield currents from flowing around the
loop, which may cancel incident magnetic fields to a large extent. The shielding prevents
voltage from developing in the center conductor. The unshielded probes are normally used
for circuit level measurements. The unshielded probes can be positioned closer to the circuit
being measured resulting in higher sensitivity. This is the reason why selecting the
appropriate magnetic field probe is significant, as certain probes can have higher sensitivity
in near field situations, which is crucial for EMI troubleshooting. There are variations of
ranges that magnetic field probes can detect emitted frequency signals. The probe used for
this experiment was the 100C model from the Beehive Electronics company. This model can
detect a range from 0 to 100 MHz, so it is considered a low-range model.

32
Figure 10 This is a graph of the output power of the 100 series probes respective to their
detection frequencies. The 100C probe is the one that used for this experimentation as it had
the highest sensitivity for low frequency. (1)

33
Chapter 5
5.1 Experimental Procedure
The setup for the experiment was simple in execution. It required the activation of an
oscilloscope and the subsequent attachment of the magnetic field probe. A BNC (Bayonet
Neil Concelman) connector was used to attach the probe, serving as a radio frequency
connection. The probe was used to scan for frequency waves generated from the Arduino
crystal oscillator. The first stage was to measure the oscillation activity with no shielding
protection to determine the standard frequency from the Arduino. Measurements showed that
this frequency was approximately 16 MHz. The initial frequency can be adjusted for more
analysis, which will be explained in a subsequent section. The next stage was to measure the
EMI from a carbon fiber enclosed Arduino. The carbon fiber shielding was very effective as
the oscilloscope showed a strong decrease in the oscillator frequency. The final stage was to
cover the oscillator with a layer of copper plated conductive adhesive. This reduced the
magnetic interference of the probe, but was not as effective in blocking emitted waves
compared with the carbon fiber shielding. The following diagram and figures display both
the setup and results of the experiment.

34
CNT Carbon Fiber and Copper Adhesive Parameters
CNT Carbon Fiber Copper Adhesive
Thickness (in) t 2.36x 10-3 2.36x 10-3
Conductivity (S/m) 𝝈 𝒓 1.00×108 5.96×107
Electrical Resistivity (𝛀𝒎) 𝝆 1.00×10−8 1.68×10−8
Relative Permeability 𝝁 𝒓 100 0.999994
Magnetic Permeability (H/m) 𝝁 1.26×10−4 1.256629×10−6
Vacuum Permittivity (F/m) 𝜺 𝟎 8.854 187 817× 10−12 8.854 187 817× 10−12
Vacuum Permeability (H/m) 𝝁 𝟎 1.2566370614 ×10−6 1.2566370614 ×10−6

35
Block Diagram of EMI Shield Testing
Figure 11 This picture was taken of the oscilloscope measuring the Arduino oscillator with
no shielding. The probe detection with the oscilloscope showed a 22.4 mV peak to peak
amplitude.
Oscilloscope
H Field Probe
Shield Material
Oscillator (Varying Frequencies)

36
Figure 12 This picture was taken of the oscilloscope measuring the Arduino oscillator with
carbon fiber shielding. The probe detection with the oscilloscope showed a 3.6 mV peak to
peak amplitude.
Figure 13 This picture wastaken of the oscilloscope measuring the Arduino oscillator with copper
adhesive shielding.The probe detection with the oscilloscope showed a 15.6 mV peak to peak
amplitude
5.2 Analysis of Experiment
It is important to assess the results found by magnetic probing. The structure of CF is
a major factor in its conductivity and tensile strength. The CF is made of carbon crystals
aligned in a long axis. These hexagonal shaped crystals organize themselves in long flattened

37
ribbons. This crystal alignment makes the ribbon strong in the long axis and these ribbons
align themselves within fibers. These fibers (containing flat ribbons of carbon crystals) in
turn are bundled by the manufacturer in thicker fibers and are woven into carbon cloth, which
is what was used in this experiment.
Metals such as copper typify conductors and have an extremely high resistance to the
flow of charge through them. An object identified as a "conductor" implies that the outer
electrons of the atoms are loosely bound and free to move through the material. In copper,
the valence electrons are essentially free and strongly repel each other. Any external
influence which moves one of them will cause a repulsion of other electrons.
Figure 14 This is an example of the carbon fiber material and the copper adhesive used in
the experiment.
For appropriate comparison, it is necessary to analyze the measurements from the experiment
by converting them to decibels.
𝑑𝐵 𝑉 = 20𝑙𝑜𝑔10(𝑉𝑝−𝑝 ∗ 0.3535) = 20𝑙𝑜𝑔10( 22.4 ∗ 0.3535) = 23.993
𝐶𝑜𝑝𝑝𝑒𝑟 𝐴𝑑ℎ𝑒𝑠𝑖𝑣𝑒 20𝑙𝑜𝑔10( 15.6 ∗ 0.3535) = 20.682
𝐶𝑁𝑇 𝐶𝑎𝑟𝑏𝑜𝑛 𝐹𝑖𝑏𝑒𝑟 20𝑙𝑜𝑔10( 3.6∗ 0.3535) = 8.114
Calculations for shielding loss with respect to the 16 MHz oscillator.

38
𝐶𝑜𝑝𝑝𝑒𝑟 𝑆𝐸 𝑅( 𝑑𝐵) = 20𝑙𝑜𝑔10 (
𝜂0
4𝜂 𝑠
) = 20𝑙𝑜𝑔10
(
√
𝜇0
𝜀0
4√2𝜋𝑓𝜇
𝜎 )
=
377
1.842 ∗ 10−4 = 1.26 ∗ 102
𝐶𝑎𝑟𝑏𝑜𝑛 𝐹𝑖𝑏𝑒𝑟 𝑆𝐸 𝑅( 𝑑𝐵) = 20𝑙𝑜𝑔10
(
√
𝜇0
𝜀0
4√2𝜋𝑓𝜇
𝜎 )
=
377
1.422 ∗ 10−4
= 1.08 ∗ 102
Now we solve for the skin depth of the materials needed for other equations.
𝐶𝑜𝑝𝑝𝑒𝑟 𝑆𝑘𝑖𝑛 𝐷𝑒𝑝𝑡ℎ 𝛿 =
1
√ 𝜋 ∗ 𝑓 ∗ 𝜇 ∗ 𝜎
=
1
√𝜋 ∗ 16000 ∗ 1.256629 ∗ 10−6 ∗ 5.96 ∗ 107
= 5.15 ∗ 10−4
𝐶𝑎𝑟𝑏𝑜𝑛 𝐹𝑖𝑏𝑒𝑟 𝑆𝑘𝑖𝑛 𝐷𝑒𝑝𝑡ℎ 𝛿 =
1
√𝜋 ∗ 16000 ∗ 1.256629 ∗ 10−6 ∗ 5.96 ∗ 107
= 3.97 ∗ 10−5
Now we solve for the absorption loss equation.
𝐶𝑜𝑝𝑝𝑒𝑟 𝑆𝐸𝐴 ( 𝑑𝐵) = 20𝑙𝑜𝑔10 𝑒
𝑡
𝛿 = 20𝑙𝑜𝑔10 𝑒
2.36∗10−3
5.15∗10−4
= 3.98 ∗ 101
𝐶𝑎𝑟𝑏𝑜𝑛 𝐹𝑖𝑏𝑒𝑟 𝑆𝐸𝐴( 𝑑𝐵) = 20𝑙𝑜𝑔10 𝑒
2.36∗10−3
3.98∗10−4
= 5.15 ∗ 102
The multiple internal reflection must now be solved.
𝐶𝑜𝑝𝑝𝑒𝑟 𝑆𝐸 𝑀 = 20𝑙𝑜𝑔10 (1 − 𝑒
−
2𝑡
5 ) = 20𝑙𝑜𝑔10 |1 − 10
𝑆𝐸 𝐴
10 | = 7.95 ∗ 101
𝐶𝑎𝑟𝑏𝑜𝑛 𝐹𝑖𝑏𝑒𝑟 𝑆𝐸 𝑀 = 20𝑙𝑜𝑔10 (1 − 𝑒
−
2𝑡
5 ) = 20𝑙𝑜𝑔10 |1 − 10
𝑆𝐸 𝐴
10 | = 1.03 ∗ 103
After calculating all the necessary equations, we can now solve for the total effectiveness.
𝐶𝑜𝑝𝑝𝑒𝑟 𝑆𝐸 𝑇 ( 𝑑𝐵) = 𝑆𝐸 𝑅 + 𝑆𝐸𝐴 + 𝑆𝐸 𝑀 = 2.46 ∗ 102
𝐶𝑎𝑟𝑏𝑜𝑛 𝐹𝑖𝑏𝑒𝑟 𝑆𝐸 𝑇 ( 𝑑𝐵) = 𝑆𝐸 𝑅 + 𝑆𝐸𝐴 + 𝑆𝐸 𝑀 = 1.66 ∗ 103
𝐶𝑎𝑟𝑏𝑜𝑛 𝐹𝑖𝑏𝑒𝑟 𝑆𝐸 𝑇 > 𝐶𝑜𝑝𝑝𝑒𝑟 𝑆𝐸 𝑇
In order to test the consistency of the shielding effectiveness, the materials were

39
tested over a range of frequencies from 16 MHz to 40 MHz. The following graphs are a
comparison of the frequencies respective to an attribute of shielding.
0.00E+00
2.00E+01
4.00E+01
6.00E+01
8.00E+01
1.00E+02
1.20E+02
1.40E+02
0 5000 10000 15000 20000 25000 30000 35000 40000 45000
ReflectionLoss(dB)
Frequency (Hz)
Frequency vs Reflection Loss
Frequency Vs Reflection Loss (Copper) Frequency Vs Reflection Loss (CNT-CF)
0.00E+00
1.00E+02
2.00E+02
3.00E+02
4.00E+02
5.00E+02
6.00E+02
7.00E+02
8.00E+02
9.00E+02
0 5000 10000 15000 20000 25000 30000 35000 40000 45000
AbsorptionLoss(dB)
Frequency (Hz)
Frequency vs Absorption Loss
Frequency vs Absorption (Copper) Frequency vs Absorption (CNT-CF)

40
Conclusion
In order to properly understand the principle of EMI shielding, two common materials were
compared using magnetic field probing. The probing was utilized on an Arduino board in
order to test the shielding material application to common electronic devices. The carbon
fiber was tested and found to be an efficient material for shielding the magnetic frequency
generated from crystal oscillators. The copper plating adhesive was also effective in
shielding the oscillator frequency, yet the oscilloscope shows that the detected amplitude is
higher for the copper in comparison to the carbon fiber. Future developments of this
experimentation will require comparison with more conventional shielding materials such as
mu-metal under various environmental circumstances and frequency ranges.
0.00E+00
2.00E+02
4.00E+02
6.00E+02
8.00E+02
1.00E+03
1.20E+03
1.40E+03
1.60E+03
1.80E+03
0 5000 10000 15000 20000 25000 30000 35000 40000 45000
MultipleReflectionLoss(dB)
Frequency (Hz)
Frequency vs Multiple Reflections

41
Works Cited
(1) The 100 Series EMC Probes Are Designed for Identifying and Fixing
EMC Problems. 100 Series EMC Probes (n.d.): n. pag. Web.
(2) "Addressing the Environmental Impact of Carbon Fiber Scuttlebutt
Sailing News." Scuttlebutt Sailing News. N.p., 17 Oct. 2013.
Web. 23 Apr. 2016.
(3) "Arduino - Introduction." Arduino - Introduction. N.p., n.d. Web. 23
Apr. 2016.
(4) "Basic Properties of Waves." - Amplitude, Wavelength, Period &
Speed. N.p., n.d. Web. 23 Apr. 2016.
(5) "Chapter 11 Modern Atomic Theory." Coffey-SAA-Chemistry. N.p.,
n.d. Web. 23 Apr. 2016.
(6) Chung, Deborah D. L. Composite Materials: Functional Materials for
Modern Technologies. London: Springer, 2003. Print.
(7) "Electromagnetic Interference Shielding Fundamentals and Design
Guide." Advanced Materials and Design for Electromagnetic
Interference Shielding (2008): 1-36. Web.

42
(8) "EMC Testing and Standards in Transient Immunity Testing, RF
Immunity." EMC Testing and Standards in Transient Immunity
Testing, RF Immunity. N.p., n.d. Web. 23 Apr. 2016.
(9) Greiner, Walter. Classical Electrodynamics. New York: Springer,
1998. Print.
(10) Griffiths, David J. Introduction to Electrodynamics. Upper Saddle
River, NJ: Prentice Hall, 1999. Print.
(11) "Magnetic Susceptibilities of Paramagnetic and Diamagnetic
Materials at 20°C." Magnetic Properties of Solids. N.p., n.d.
Web. 23 Apr. 2016.
(12) "Materials Science and Engineering." MIT Open Courseware. N.p.,
n.d. Web. 23 Apr. 2016.
(13) Mcrobbie, Donald. "Concerning Guidelines for Limiting Exposure to
Time-Varying Radiation”.
(14) Electric, Magnetic, And Electromagnetic Fields (1 Hz–100 KHz)."
Health Physics 100.4 (2011): 442. Web.

43
(15) Mehdizadeh, Mehrdad. "Magnetic Field and Inductive Applicators
and Probes at High Frequencies." Microwave/RF Applicators
and Probes for Material Heating, Sensing, and Plasma
Generation (2010): 219-68. Web.
(16) "Molecular Expressions Microscopy Primer: Light and Color -
Electromagnetic Wave Propagation - Interactive Java
Tutorial." Molecular Expressions Microscopy Primer: Light
and Color - Electromagnetic Wave Propagation - Interactive
Java Tutorial. N.p., n.d. Web. 23 Apr. 2016.
(17) Light and Color - Electromagnetic Wave Propagation - Interactive
Java Tutorial. N.p., n.d. Web. 23 Apr. 2016.
(18) Ott, Henry W., and Henry W. Ott. Electromagnetic Compatibility
Engineering. Hoboken, NJ: John Wiley & Sons, 2009. Print.
(18) "Physical Space as a Quaternion Structure I: Maxwell Equations. A
Brief Note: Peter Michael Jack." Internet Archive. N.p., n.d.
Web. 23 Apr. 2016.

44
(19) Saini, Parveen, and Manju Aror. "Microwave Absorption and EMI
Shielding Behavior of Nanocomposites Based on
Intrinsically Conducting Polymers, Graphene and Carbon
Nanotubes." New Polymers for Special Applications
(2012): n. pag. Web.
(20) "Skin Depth Equation Formula (aka Skin Effect) - RF Cafe." Skin
Depth Equation Formula (aka Skin Effect) - RF Cafe. N.p.,
n.d. Web. 23 Apr. 2016.
(21) Sluder, Greenfield, and D. E. Wolf. Video Microscopy. San Diego:
Academic, 1998. Print.
(22) "Volts-to-dBm." Conversion Table: N.p., n.d. Web. 23 Apr. 2016.
(23) Wang, Yangyong, and Xinli Jing. "Intrinsically Conducting
Polymers for Electromagnetic Interference Shielding." Polymers
for Advanced Technologies 16.4 (2005): 344-51. Web.
(24) "What Is Electromagnetic Field? - Definition from WhatIs.com."
WhatIs.com. N.p., n.d. Web. 23 Apr. 2016.

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