EMC Management & Lab Accreditation
Poojita Rao Bhattu
EMC Test Engineer at Cisco Systems, Inc. San Jose, CA, USA; Master Graduate in Electrical Engineering from CSUF
[email protected]

Abstract — EMC is the ability of equipment to function
satisfactorily in its electromagnetic environment without
introducing intolerable disturbances into that environment or
into other equipment. The methods of coupling
electromagnetic energy from a source to a receptor can be
done in four categories – Conducted, Inductively, Capacitively
coupled and radiated. Emphasis is placed upon an intersystem
approach to the improvement of the overall electromagnetic
environment. There are a plethora of tests which are done
under EMC is Emissions and Immunity– Radiated &
Conducted (PLCE and SLCE), Radiated & Conducted,
Immunity, ESD (Electrostatic Discharge), EFT/B (Electric
Fast Transient/Burst), Surge, VDI, Magnetic and Flickers.
This paper provides the overview of all the EMC testing’s,
EMC Management, Laboratory Accreditation, Standards,
different EMC Chambers and Legal issues of EMC.
Keywords— EMC, RE (Radiated Emissions), CE
(Conducted Emissions), ESD (Electrostatic discharge), EFT/B
(Electric Fast Transient/Burst), PLCE (Power Line Conducted
Emission), SLCE (Signal Line Conducted Emissions), VDI
(voltage dips and Interruptions).
INTRODUCTION
When we hear “EMC” or its longer version,
“electromagnetic compatibility”, it suggests elaborate anechoic
chambers with pretty tiles, highly-specialized antennae,
sophisticated EMI receivers, copper and more copper, and a
thicket of regulations. We all are concerned with
electromagnetic compatibility because we face specific
problems in our own specialized areas. In addition to this,
natural environment, intentional electromagnetic threats are
also now emerging to which unprotected systems will be
vulnerable. The environment itself is also a pertinent factor
because its characteristics influence the electromagnetic energy
present within it. The fundamental work of strategic nature in
EMC is required now to support emerging technologies and
prevent new threats. A European technology Network on
Sustainable Electromagnetic Environments (ETN-SEE) has
been established to facilitate, coordinate, and accelerate the
development and acceptance of technologies which will create
an electromagnetic friendly and secure society in the future.
Electromagnetic compatibility invariably has two aspects. For
any incompatibility to exist there must be a source of
interference. If either of these is absent, there is no EMC
problem. Electromagnetic Interference (EMI) has become a
major problem for circuit designers, and it is likely to become even more severe in the future. As circuitry has become smaller
and more sophisticated, more circuits are being crowded into
less space, which increases the probability of interference.
Interference is the undesirable effect of noise. If a noise voltage
causes improper operation of a circuit, it is interference. Noise
cannot be eliminated, but it can be reduced in magnitude. An
EMI filter is designed to attenuate one or more specific
frequencies in order to provide electromagnetic compatibility
of an electronic device while in the presence of an
electromagnetic emitter operating at the same or similar
frequencies.
EMISSIONS AND IMMUNITY TESTS
Radiated Emissions:
Radiated Emissions testing involves measuring the
electromagnetic field strength of the emissions that are
unintentionally generated by the system. The electromagnetic
waves don’t extend out from the system in a spherical pattern.
The emissions tend to be pretty directional, so in the test lab,
we can just vary the height of the receiving antenna. The
antenna picks up both the signal direct from the system and
from the ground. The types of Antennas used for Radiated
Emissions are more than three types. Bilog Antenna (30MHz-
1GHz), Horn Antenna (1-18GHz) and Fixed Gain Horn
Antenna (18-40GHz) are mainly used.
Performing radiated emissions measurements is not as
straightforward as performing conducted emissions
measurements. The complexity of the ambient environment is
added which could interfere with measuring the emissions from
a DUT. There are some methods that can be used to
discriminate between ambient environment and signals from
the DUT. Testing in a semi-anechoic chamber can simplify and
accelerate measurements because the ambient signals are no
longer present. Chambers are an expensive alternative to open
area testing. If the device is placed on a turntable, rotate the
device while observing a signal in question. If the signal
amplitude remains constant during device rotation, then the
signal is more likely to be an ambient signal. Signals from a
DUT usually vary in amplitude based on its position.
Conducted Emissions:
Conducted RF emissions are electromagnetic disturbances
(noise voltages and currents) caused by the electrical and
electronic activity in an item of equipment and conducted out
of that equipment along its interconnecting cables, such as
power, signal or data cables. The conducted disturbances in a
conductor, emitted by one item of equipment, can couple

directly into another item of equipment that is connected to the
same conductor. Conducted disturbances are also radiated from
the conductors they travel along, as both electric and magnetic
waves, and in this sense, the conductor is acting as an
‘accidental transmitting antenna’. A very common frequency
range called out by conducted emissions standards is 150 kHz
to 30 MHz. We have two different emission testing under
Conducted Emission Testing, they are – 1) PLCE (tested on
power ports) and 2) SLCE (tested on telecommunication ports).
Power Line Conducted Emissions – CE limit are imposed
on power lines primarily to protect other equipment that shares
the power lines. The ripple caused by emissions from multiple
devices on the line can at times be additive. In the power line
conducted emission test, EUT is the interference resource and
the equivalent circuits of parallel transmission lines.
Signal Line Conducted Emissions – CE limits on signal
lines apply to the entire cable bundle and are intended to
control low-frequency radiation produced by cabling harnesses.
Radiated and Conducted Immunity/Susceptibility:
Radiated Immunity test is intended to see how well our
EUT performs when it is encountered with different types of
electromagnetic field disturbances in normal usage. A signal
generator feeds a modulated sine wave to a broadband RF
power amplifier. The output of the amplifier is connected to a
transducer, which turns the varying conducted voltage into a
varying radiated electromagnetic field. For RS test, we use
Log periodic Antenna and Horn Antenna. The compliance
testing for radiated immunity for commercial products is
based on the international standard, IEC 61000-4-3, and is
performed from 80 to 1,000 MHz at e-field levels from 3 to 20
V/m, depending on the production environment or application.
The RF signal is generally modulated by a 1,000 Hz
Amplitude Modulation sine wave modulation set to 80% for
commercial testing, and short duration (as little as 1%) pulsed
modulation for military and aerospace testing. The modulation
is designed to test for “audio rectification” issues.
Testing should be performed in a configuration, close to
actual conditions in which the EUT will be used. A metallic
grounding plane is not required, but the EUT should be placed
on a non-metallic, non-conductive material. The required
wiring length required for the EUT is less than 3m, then the
specified length should be used. The required length is longer,
a minimum of 1m of cable should be exposed to the RF field,
and excess cables should be bundled in the center of the cable
in lengths of 30-40cm.
Conducted Susceptibility is to test the immunity to
conducted disturbances induced by radio-frequency fields. It is
used to stimulate the normal voltage and current environment
of external power and signal cables. We can have both
capacitive and inductive coupling when the cables are bundled
together. The different transducers that are used in CS test are
CDNs, BCI Probe, EM Clamp and direct voltage injection.
This test simulates adjacent cabling by injecting a common mode disturbance into your cabling using a transducer. The
compliance testing for conducted immunity is based on
international standard, IEC 61000-4-6, and it is performed to
test the requirement of electrical and electronic equipment to
electromagnetic disturbances coming from intended RF
transmitters in the 9 kHz – 80 MHz frequency range.
Figure 1: Conducted Immunity Test Setup
The frequency range is swept from 150 kHz to 80MHz,
using the signal levels established during the settling process,
and with disturbance signal 80% amplitude modulated with a
1 kHz sine wave, pausing to adjust the RF signal level or to
change coupling devices as necessary. Where the frequency is
swept incrementally, the step size shall not exceed 1% of the
preceding frequency value. The dwell time of the amplitude
modulated carrier at each frequency shall not be less than the
time necessary for the EUT to be exercised and to respond, but
shall in no case be less than 0.5s. The sensitive frequencies
shall be analyzed separately.
ESD (Electrostatic Discharge):
An electrostatic discharge test is a common form of EMC
immunity test. ESD involves in applying the discharges to any
areas of the EUT which are normally accessible to a human
touch. An ESD test has two discharge pins i.e. 1) Air and 2)
Contact. In air discharge, the tip is blunt which is charged up
to full voltage. When the air discharge tip is moved closer to
the conductive surfaces of the EUT with a sufficiently large
potential difference, a spark will arc across to the device. In
contact discharge, the uncharged sharp tip gets in contact with
a point on the EUT. When the trigger is applied to the ESD
simulator, the tip is charged that discharges the energy through
the EUT. ESD can attack via two paths – conduction (direct)
and electromagnetic radiation (indirect). The indirect effects
are real, and I’ve seen indirect ESD induced failures occur up
to 20 feet away. These multiple paths often mean multiple
design fixes. For the direct effects, filters/transient protection
are used for vulnerable inputs/outputs, while ferrites or other
current limiting are used for power/ground paths. For the
indirect effects, high-frequency shielding is used. Damage is
common when ESD is injected on an unprotected I/O pin –
digital, analog, or even power. Circuits vulnerable to ESD
damage include I/O or any other lines directly connected to
the outside world. Circuits vulnerable to ESD upset include
resets, interrupts, and controls. Unwanted resets are very
common with ESD — so common that we routinely add
protection to these devices. Even power circuits are

vulnerable. I have seen ESD shut down power supplies due to
ESD upsetting power protection circuits.
EFT/B, Surge, and VDI:
The repetitive fast transient test with bursts consisting of a
number of fast transients, coupled into the power supply,
control and signal ports of electrical and electronic equipment.
Significant for the test are the short rise time, the repetition
rate and the low energy of the transients. EFT is done in two
coupling methods. They are – 1) Direct and 2) Capacitive.
Indirect coupling for power ports, the EFT disturbances are
injected directly onto the relevant signals with a carefully
defined source impedance. In capacitive coupling, the signals
are fed through a capacitive coupling clamp, which couples
the disturbance to the cables. The International standard for
EFT/B test is IEC-61000-4-4. Test voltages of up to 4 kV in
positive and negative polarities are applied to the A/C power
leads and up to 2 kV is applied to the I/O cables. The test
voltages are at a 5 kHz pulse repetition frequency and applied
for 60 seconds to each power supply terminal including
protective earth and every combination of these terminals. The
coupling clamp is used to apply up to 2 kV to the I/O cables.
Surge is usually applied to AC (or DC) power input ports,
but in some cases, it is also applied to the I/O ports. The surge
pulses are coupled directly to the signals via defined source
impedance. The coupling network is usually contained inside
an immunity test system along with a decoupling network
which helps to protect the power supply or auxiliary
equipment. Surge coupling mechanisms are described in two
modes: 1) Common mode 2/10 us, 6kV open-circuit voltage,
100 amp short-circuit current. (Longitudinal surge), 2)
Differential mode 2/10 us, 1kV open-circuit voltage, 100 amp
short-circuit current (metallic surge). In common mode surge,
all the conductors in the cable develop the same instantaneous
voltage with respect to earth ground. There is no voltage
difference between any two conductors in the cable. The
majority of surges that affect communication cables are
common mode surges.
Figure 2: Common surge mode
When considering common mode surge, it is important to
understand that if there is no path for surge current to exit the
equipment, no surge current can flow. Similarly, even if there
is a path that contains an isolation barrier that is stronger than
the applied surge voltage, no current can flow, and this
strategy particularly works very well for Ethernet ports. In differential mode surge, a surge voltage appears
between the individual conductors in a multi-conductor cable.
The surge current will attempt to enter the equipment on one
of the cable conductors and exit the equipment on another
conductor in the same cable.
Figure 3: Differential surge mode
VDI test is normally used to simulate voltage dips and
short brownouts on AC or DC power supplies. This test allows
us to know whether the EUT works properly with the power
supply fluctuations. IEC 61000-4-11 defines the immunity test
methods and range of preferred test levels for electrical and
electronic equipment connected to low-voltage power supply
networks for voltage dips, short interruptions, and voltage
variations. This standard applies to electrical and electronic
equipment having a rated input current not exceeding 16 A per
phase, for connection to 50 Hz or 60 Hz A.C. networks.
Figure 4: Dips for a period in the order of a millisecond.
Voltage dips and short interruptions are caused by faults in
the network, in installations or by a sudden large change of
load. Voltage variations are caused by the continuously
varying loads connected to the network. The EUT is tested for
test levels of 30%, 60% and ;95% below the rated voltage for
the equipment. The duration of the dips/interruptions are
10ms, 100ms and 5000ms respectively. Five dips are
performed for each test level at a rate of one dip per minute.
The changes in supply voltage occur at zero crossing of the
voltage. A test level of 0% corresponds to a total supply
voltage interruption.
Harmonics and Flickers:
Flicker and harmonics testing are another forms of
emissions testing. These EMC tests are usually performed to
the EN61000-3-2 and EN61000-3-3 standards respectively. In
Europe, these are considered to be 'horizontal' standards,
which means that they apply to almost all types of electronic
or electrical equipment that enter the EU. Harmonics is
current testing, which is usually associated with switch mode

power converters and other non-linear loads. The harmonics
load on local power supplies is reduced, which helps to avoid
overheating and increases efficiency. The test setup for
measuring harmonic currents is very similar, only a sense
resistor is added in series. By measuring the dynamic current
consumption across the frequency range of interest, the
analyzer is able to calculate the current consumption of the
power supply harmonics.
Figure 5: Harmonics Current measurement circuit.
Flicker is voltage testing that is caused arcing between
contacts which in turn would cause nearby lamps sharing the
same power supply to flicker. In figure 6, all the analyzer is
measuring the voltage across the EUT. There is a calibrated
complex source impedance, so the analyzer can work out the
voltage fluctuations across a range of frequencies.
Figure 6: Flicker measurement circuit.
Pass/Fail Criteria:
When performing all the EMC Immunity tests, we have to
evaluate whether the product passes or fails each EMC
immunity test. They need to monitor your equipment during
and after each test and watch for any changes to the behavior
or operation. The performance of the product usually falls into
categories A, B, C, and D.
? Criteria A: It is considered perfect, which means our
product performs normally and within specifications,
usually in the product manual, during and after the
test. So essentially nothing bad happens to the
product.
? Criteria B: The product may have a temporary loss of
function of performance which ceases after the
applied disturbance ceases. So after the test finishes,
the equipment under test recover to its normal
performance without operator intervention. ? Criteria C: It is the same as Criteria B, but the
operator intervention is required. So maybe the EMC
phenomena reset the device and we need to power it
back on manually.
? Criteria D: There is a loss of degradation of
performance which is not recoverable, owing to
damage to the hardware or loss of data. So basically
in some way the test has trashed the product. It might
have fried some components or caused corruption of
some data.
EMC MANAGEMENT AND METHODOLOGIES
To facilitate assurance of achieving compatibility, an EMC
management lifecycle for every project is required. Each phase
of the project lifecycle can be termed Definition, Requirement,
Tendering, Design, Manufacture, Installation, Commissioning,
and Operations ; Maintenance.
A. Definition Phase
In this phase, the potential impact of EM interference
between different electrical and electronic systems in the pre-
defined electromagnetic environment is accessed and
identified.
B. Requirement Phase
In this phase, the general EMC management and specific
EMC technical requirements applicable to the project is
formulated.
C. Tendering Phase
During this stage, EMC competence of the tenders is
assessed based on their technical abilities to comply with the
specific EMC requirements. Upon completion of the EMC
assessment, the relevant project leaders should be advised of
the results to enable them to finalize their overall assessment.
D. Design Phase
In the Design phase, EMC design progress, and compliance
with requirements of each sub-system should be monitored.
The design submissions include EMC Management Plan, EMC
Test Specification, EMC Test Reports or Certificates and EMC
Design Review.
E. Manufacture Phase
All EMC design should be completed with each system
with the compliance requirements. Based on the proven
designs, manufacturing of the system hardware is commenced.
F. Installation Phase
To make certain system design integrity, good EMC
installation is practiced.

G. Commissioning Phase
During this phase, the identification of all necessary EMC
interface and integration tests for each component of the
system should be carried out.
H. Operation ; Maintenance Phase
The operators ; maintainers monitor the performance of
the system. Enhancement of the EMC Compliance Matrix
should be revised which will facilitate the preparation of the
EMC specifications for the future system upgrade.
EMC management mode enables the interpretation of role
definition and the management required in each phase of the
project is to manage the EMC assurance in a large-scale
project.
LABORATORY ACCREDITATION
Since 1990, the accreditation of EMC laboratories has
become increasingly important in many parts of the world. The
compliance of most of the electronic products with national
and international electromagnetic compatibility (EMC)
requirements is to be determined and documented. Qualified
test laboratories can help reduce the test and approval periods,
especially when regulatory authorities accept test data and
reports documented without further evaluations. For example,
in the US, an EMC test laboratory is accredited by A2LA
(American Association for Laboratory Accreditation), NVLAP
(National Voluntary Laboratory Accreditation Program). A2LA
works with government and industry to serve as a resource on
issues of quality and competence, provides technical expertise
and recommendations on approaches to oversight, and helps to
ensure conformance with established policies and requirements
through accreditation.
Accreditation of US EMC test laboratories to the foreign
standards serves as a basis for their recognition by the foreign
regulatory authority as a conformance assessment body (CAB).
Accreditation provides a formal recognition to competent EMC
testing laboratories based on the authentication of the
enforcement of a quality system in the laboratory (in
accordance with ISO/IEC 17025) and the determination of a
minimum level of technical proficiency to perform the EMC
tests. There are four distinct groups that benefit from
accreditation in general: EMC laboratories, users of laboratory
testing services, regulatory authorities (private and public
entities that require quality test data to operate), and the public.
Accreditation has a positive impact on the public by
stimulating higher standards of quality within EMC testing
laboratories. Manufacturers also gain efficiency because of
accreditation as they do not have to perform their own on-site
assessments. Manufacturers who have in-house EMC testing
capabilities can reduce or eliminate the overhead costs by using
external accredited laboratories with the assurance of technical
proficiency. Laboratory accreditation uses criteria and
procedures specifically developed to determine technical
competence. Qualified technical assessors conduct a thorough
evaluation of all factors in a laboratory that affects the production of test or calibration data. Very often these criteria
are based on ISO/IEC 17025, which is used for evaluating
EMC test laboratories throughout the world.
Mutual recognition arrangements (MRAs), are crucial in
enabling test and calibration data which are accepted by the
countries. MRAs rely on accreditation as a basis for
establishing technical competence and building regulator
confidence. The accreditation bodies are responsible for
accrediting competent conformity assessment bodies (CABs)
in accordance with international standards and to the importing
party’s technical requirements. In the United States, NIST
(National Institute of Standards and Technology) currently lists
A2LA, ANAB (ANSI-ASQ National Accreditation Board) , and
NVLAP as acceptable for use by MRAs for EMC and
telecommunications test laboratories (ISO/IEC 17025). Both
A2LA and ANSI are recognized through the National
Voluntary Conformity Assessment Systems Evaluation
(NVCASE) Program as accreditors of certification bodies
(ISO/IEC Guide 65). ISO/IEC 17025 allows laboratories to
implement a sound quality system and demonstrate that they
are technically competent and produce valid and reliable
results.
The accreditation of EMC test laboratories around the
world becomes more important with the globalization of trade
and the proliferation of electronic and electric products in all
aspects of life. Regulatory authorities in many countries have
changed product approval processes for various product
categories and now allow manufacturers to determine and
declare product compliance with applicable standards.
Qualified EMC test laboratories can now test products in
accordance with foreign requirements/standards and prepare
test reports that serve as the basis for product approval in
foreign markets. EMC test laboratories must demonstrate their
technical proficiency to perform these tests and also establish a
quality framework that allows testing under repeatable and
consistent conditions. The laboratory accreditation process
(applied by recognized accreditation bodies), based on the
generally accepted standard ISO/IEC 17025, allows test
laboratories to obtain this independent determination and
documentation of technical proficiency in the technical field of
EMC.
From my experience, few things that I can share about ISO
17025 Accreditation. ISO 17025 is mainly applicable for
testing and calibration laboratories. Normally the process of
ISO 17025: 1) Scope, 2) Normative References, 3) Terms and
Definitions, 4) Management Requirements and 5) Technical
Requirements. In Scope, meet general requirements a
laboratory has to meet to be considered competent. In
Normative references, general terms and their definitions
concerning standardization and other quality systems like
installation, designing and development are done. Terms and
Definitions are for the purpose of International standards such
as shall, should, policy, procedure, documents, quality system
and recording of the product is done in the process or not.
Quality control data shall be analyzed where they are found to
be outside pre-defined criteria, the planned action shall be

taken to correct the problem and to prevent incorrect results
from being reported. Under Management Requirements we
ensure that the quality system, document control, review of
requests, tenders, service to the client, purchasing services and
suppliers, correction, prevention and management reviews are
performed. Finally, under technical requirements,
environmental conditions. Test methods, validations, sampling,
traceability and reporting the results are completed. Therefore,
the ISO 17025 pass level is 80%. The newer version of
ISO/IEC 17025 calls out requirements for impartially stating
that the laboratory management must commit to impartially
and that the laboratory must ensure impartially in all its
activities and not allow commercial, financial or other
pressures to compromise impartially. Impartially is the
principle that decisions are based on objective evidence
obtained during the performance of the laboratory’s activities,
not on the basis of bias or prejudice caused by the influence of
different interests of individuals or other involved parties.
EMC STANDARDS
Standards were created to provide a method of testing
products so that different test facilities could compare test
data. Without standards, each test lab or manufacturer was
performing testing of products to their own methods and
limits. The major worldwide standards for the EMC sector are
IEC (International Electrotechnical Commission) standards
and CISPR (Comité international spécial des perturbations
radioélectriques) standards. IEC standard defines the input
from the country organizations as they are trade consensus.
CISPR addresses at 9 KHz and also 18-40GHz. CISPR is the
standard that presents several test methods, with suggested
limits, to evaluate the level of radiated emissions from a
component designed for installation. CISPR is subdivided into
three categories. They are 1) Basic standards 2) Generic
standards 3) product standards. The basic standards tell us
what actually the procedure is, but, it doesn’t explain at which
level the product should be tested. Generic standards are
applied when the product doesn’t have its specific standards
but, explains how to perform the test. Product standards are
the product group’s i.e. medical, household equipment’s and
explains which test should be performed t what level on each
equipment. CISPR 11 is widely used international standard for
EMC within Europe for electromagnetic emissions or
disturbances from Industrial, Scientific, and Medical, ISM,
Equipment. CISPR 11 applies to a very wide variety of
equipment including everything from Wi-Fi systems, and
microwaves through to arc welders, all of which fall into the
industrial, scientific and medical category that can use the
ISM license-free bands like 2.4 GHz.
CISPR 16 is a series of fourteen publications specifying
equipment and methods for measuring radio disturbances and
immunity of voltages and currents in the frequency range 9
kHz to 1GHz. CISPR 16 is split into four distinct parts with an
overall number of fourteen different elements i.e. CISPR 16-1,
CISPR 16-2, CISPR 16-3 and CISPR 16-4. CISPR 16-1
consists of five parts which specify voltage, current, and field measuring apparatus. CISPR 16-2 specify the methods for
measuring high-frequency EMC phenomena. It addresses both
EMC disturbances and immunity. CISPR 16-3 is basically a
technical report rather than a standard and it contains specific
technical reports and information on the history of CISPR.
CISPR 16-4 consists of five parts and contains information
related to uncertainties, statistics and limit modeling . CISPR
22 is widely used standard for electromagnetic compatibility
within Europe for Information Technology Equipment, ITE.
CISPR 22 differentiates between Class A and Class B
equipment and it gives figures for conducted and radiated
emissions for each class. CISPR 22 requires certification over
the frequency range of 0.15 MHz to 30 MHz for conducted
emissions. CISPR 22 has no specified limits for frequencies
above 1.0 GHz, and CISPR limits are provided in dBµV, while
the FCC limits are specified in µV. In terms of similarities, the
conducted and radiated emission limits specified in CISPR 22
and FCC Part 15 are similar.
The tables below give a summary of the field strength limits
for conducted and radiated emissions of CISPR 22 standard.
Table 1: CISPR 22 CLASS A Conducted EMI Limit:
The
frequency of
Emission
(MHz) Conducted
limit
(dBuV)

Quasi-peak Average
0.15-0.50
79 66
0.50-30.0
73 60
Table 2: CISPR 22 CLASS B Conducted EMI Limit:
The frequency
of Emission
(MHz) Conducted
limit
(dBuV)
Quasi-peak Average
0.15-0.50 66 to 56 56 to 46
0.50-30.0 56 46
5.00-30.0 60 50
Table 3: CISPR 22 CLASS A 10-meter Radiated EMI Limit:
The frequency of
Emission (MHz) Field Strength
Limit (dBuV/m)
30-88 39
88-216 43.5
216-960 46.5
above 960 49.5
Table 4: CISPR 22 CLASS B 3-metre Radiated EMI Limit:
The frequency of
Emission (MHz) Field Strength
Limit (dBuV/m)
30-88 40
88-216 43.5
216-960 46
above 960 54

FCC Part 15 is a Code of Federal Regulations, Title 47, Part
15, 47 CFR 15. Title 47 regulates everything from spurious
emissions to unlicensed low-power broadcasting in the USA.
Part 15 of the FCC Title 47 is often just called FCC part 15
and it relates to EMC. The FCC Part 15 rules and regulations
have been designed to align with the European CISPR
regulations.
The scope of FCC Part 15 is split into three sections as
follows:
? FCC Part 15A: This section sets out the regulations
under which an intentional, unintentional, or
incidental radiator may be operated without an
individual license. It also contains the technical
specifications as well as the administrative
requirements and other conditions relating to the
marketing of FCC Part 15 devices.
? FCC Part 15B: This covers the operation of an
intentional or unintentional radiator that is not in
accordance with the regulations in this part must be
licensed according to the provisions of section 301 of
the US Communications Act of 1934.
? FCC Part 15C: Unless specifically exempted, the
operation or marketing of an intentional or
unintentional radiator that is not in compliance with
the administrative and technical provisions, including
prior FCC authorization or verification, as
appropriate, is prohibited under section 302 of the US
Communications Act of 1934.
There are two classes of the device for FCC Part 15:
? Class A digital device: Within FCC Part 15, a Class
"A" digital device is one that is used in a commercial,
industrial or business environment.
? Class B digital device: Within FCC Part 15, a Class
"B" digital device is used in a residential or domestic
environment. Examples of devices in this category
may be personal computers, calculators, and similar
electronic devices that are marketed for use by the
general public.
One of the major elements of this was the EMC Directive –
89/336/EC. EMC standard applied to all equipment that was
placed on the market of users within the EC. The EMC
Directive from the EC (European Commission) was ground-
breaking in terms of EMC standards and legislation as it was
the first time that limits had been placed on the immunity of
the equipment to interference as well as its emissions. The
EMC Directive has moved onwards and is now a well-
established EMC standard. EMC CHAMBERS
A Chamber is used for EMC and RF (Wireless) testing. The
word ‘anechoic’ more or fewer means ‘without echo.’ An
anechoic chamber is designed to absorb reflections of waves
within the chamber rather than have them bounce off the walls
which can cause echo. If these chambers are designed and
assembled correctly, they can keep the waves entering from
the chamber i.e. they provide shielding from outside
interference. There are many types of anechoic chambers that
are designed for different applications. Some of the most
common uses and types are for things like audio recording,
radiated emissions testing, radiated immunity testing, wireless
transmitter (RF) testing, antenna testing and specific
absorption rate (SAR) testing. Audio chambers are the odd
man out here because they deal with absorption of sound
waves rather than electromagnetic energy which is common to
all the other types of chambers.
Semi-Anechoic Chamber: An anechoic chamber is an RF
shielded room whose walls and ceiling have been covered
with microwave absorbers and ferrites. Ferrites are used for
low frequencies for continuous matching between the
impedance of interior of the chamber and the impedance of the
shielded walls. The most common type of EMC testing
chamber by far is the semi-anechoic chamber. The word ‘semi’
indicates that it’s only partially able to absorb electromagnetic
energy and one of the reasons for that is, the floor of the
chamber is reflective rather than absorptive. The test distance
for the semi-anechoic chamber is 3m, 5m, and 10m. A semi-
anechoic chamber is a room where sound reflections only
come from the floor because the walls and ceiling are
absorbent. The solid floor makes this room much easier to
work in than the anechoic chamber because equipment can be
stood on the solid floor. We often put absorbent material on
the floor to reduce floor reflections.
Figure 7: Semi-Anechoic Chamber
Full-Anechoic Chamber: The main purpose of a fully
anechoic chamber is to perform full compliance measurements
of radiated emission and immunity. The full anechoic chamber
is a multi-functional EMC test facility for commercial and
telecom testing. The combination of the pan-type 2mm
galvanized panel system, parallel closing RF shielded doors
and polystyrene hybrid absorbers on the walls, floor and
ceiling create a high performance controlled electromagnetic
environment that complies with international immunity and
emission test standards. The FAR test volume is measured at

three levels, bottom, middle and top, with a fixed position for
the receive antenna. The two methods for FAR validation are
the reference site method (RSM) for path lengths of 3 and 5
meters and traditional NSA for 5 and 10-meter distances. The
RSM is required in the shorter paths in order to reduce
coupling or near-field effects related to biconical receive
antennas.
Figure 8: Full-Anechoic Chamber
OATS (Open Area Test Site): In OATS is preferable to the
SAC because there are no walls in the vicinity of the
measurement area. Even with plenty of absorbing material on
the walls of a SAC, there will still be a portion of the wave
energy that gets through the absorber and reflects back off the
metallic surface of the chamber wall. An Open Test Area Site
is a 3m and 10m emissions test range. The receiving
measurement antenna, in that case, picks up the wave coming
from the equipment under test (EUT), the reflection off the
floor and the partial reflection off one or more walls.
Figure 9: OATS (Open Area Test Site)
GTEM (Gigahertz Transmissive Electromagnetic cell ):
GTEMs are used to measure radiated emissions for FCC part
15B and 18 devices (with some caveats) and perform radiated
immunity testing according to IEC61000-4-3. The two main
downsides of a GTEM are the limited EUT size and the
measurement error at lower frequency ranges (approximately
under 200 MHz). The GTEM cell is a frequency extended
variant of the traditional TEM (Transverse Electro-Magnetic)
cell. It is designed for EMC applications, calibration of
antennas/field probes, test and measuring of mobile phones
and screening measuring of material. Figure 10: GTEM cell
Reverberation Chamber: An electromagnetic
reverberation chamber (RVC) is a chamber which is made to
resonate. They are predominantly used as a cavity resonator to
perform radiated immunity testing. Due to the high Q-factor of
the chamber and the almost complete reflectivity of the walls
and floor, an electromagnetic field of a given strength can be
created using a much smaller power amplifier compared to
that needed in a SAC.
Figure 11: Reverberation Chamber
RF Shielded Room: An RF shielded room forms the basis
for a semi-anechoic chamber. It is a well-sealed metal box
which offers electric and magnetic field shielding
effectiveness over a given range of frequencies. RF Shielded
rooms provide RF quiet environment in which to conduct
different application tests such as EMC, wireless technology
on automotive or military vehicles, MRI scans, etc. These
rooms are built with Smart shield TM modular RF shielding,
electromagnetic pulse protection EMPP shielding, TEMPEST
(secure communications) shielding and architectural shielding
full systems.
Figure 12: RF Shielded Room

LEGAL EMC ISSUES
Traditionally, EMC and EMI issues are solved in the EMC
lab, often without getting a full understanding of the
underlying effects. The root causes of electromagnetic
resonance, effects the product, enabling fast design cycles and
high product quality. To reduce the EMC issues, power
chokers are used with inverters. In general, one choke is used
for each phase of an inverter. Currents flowing through these
chokes are in the range of a few amps. Electric and magnetic
losses lead to heat generation, and this heat can affect the
performance and reliability of inverters. The denser the
individual components of an inverter are packed together, the
more critical heat management is. AC Inverters use a fast
switching PWM (Pulse Width Modulation) technique to create
a variable frequency AC Output to the connected motor. The
fast switching of the output of the drive when connected with
long motor cables results in a reflected voltage at the motor
which can be up to three times the AC supply voltage. Output
chokes help to reduce this peak voltage, and increase the rise
time, to reduce the stress applied to the motor insulation and
prevent damage. Currents flowing through these chokes are in
the range of a few amps.
Electric and magnetic losses lead to heat generation, and
this heat can affect the performance and reliability of
inverters. The denser the individual components of an inverter
are packed together, the more critical heat management is.
Some EMC issues are caused by poor grounding and shielding
i.e. quieting the sources of interference, inhibiting coupling
paths and hardening the potential victims. The issues with
shielded enclosures are when the longest dimension
approaches half wavelength. There are three main issues of
concern for wound (inductive) components which control
stray magnetic fields, the variability of their parameters with
current and temperature, and their resistivity. While
performing EMC tests, the test setup, including the layout of
the equipment, the cable used, cable length, supporting
equipment, etc. shall follow the relevant EMC standards.
Sometimes, we need to maintain the exact length of the cables
that are connected to the system to simulate the actual
operating conditions of the equipment in its applications.
FUTURE EMC
Today, the trends of the past 20 years are continuing.
Computing devices are getting denser, faster, more complex
and more pervasive, creating new challenges for the EMC
engineer. At the same time, advances in electromagnetic
analysis and available design possibilities are revolutionizing
the methods used to ensure compliance with EMC
requirements. Newer technologies are more likely to cause an
EMI disruption that could cause functional degradation to
another system with low levels of immunity protection.
Mixed-signal components (digital and analog) are both used
on printed circuit boards, yet during the design process
hardware engineers are concerned with functionality as per
market specifications. Digital devices may emit EMI that
could interfere with the operation of other electrical devices and systems. Newer technologies are in general more likely to
cause an EMI disruption or induce an event that could cause
functional degradation to another system with low levels of
immunity protection.
Government and industry conventions, the test procedures
related to electromagnetic compatibility continue to be
introduced and updated on a regular basis. Nevertheless, the
rapid pace of technical innovation basically ensures that
regulations alone will never be sufficient to guarantee the
safety and compatibility of electronic systems. This makes it
more important than ever to address electromagnetic
compatibility issues early in the design, rather than “fixing” a
product after it fails to meet a given requirement.
Understanding the nature of EMI in a real-life environment and
how to deal with it can help users to make their processes and
equipment much more effective and error-free, and their
sensitive devices better protected from EMI-caused electrical
overstress. EMC engineers should be educated in Hazard
Based Safety Engineering (HBSE) which addresses functional
safety along with hazard and risk assessments. As of today,
only a few engineers are aware of a new HSBE standard (IEC
62368-1) that may eventually replace certain UL, CSA, IEC
and EN product safety standards.
ACKNOWLEDGMENT
I would like to express my deep gratitude to my Professors
and Colleagues, for their patient guidance, enthusiastic
encouragement and useful critiques of this paper. Finally, I
wish to thank my parents for their support and encouragement
throughout my study.
REFERENCES
1 Electromagnetic Compatibility Engineering by Henry W.
Ott.
2 Electromagnetic Compatibility of Integrated Circuits:
Techniques for Low Emissions and Susceptibility by
Sonia ben dhia , Mohamed ramdani , Etienne sicard J.
3 Woodrow W. Everett, JR, Member of IEEE, and R.
Powers, Member of IEEE “Electromagnetic
Compatibility: A Position Paper,” IEEE Transl. Volume:
EMC-8, Issue:3 , pp. 161-168, 1966 8 th
National
Symposium.
4 EMC standards and legislation from Electronic Notes
5 COMTEST Engineering
6 EMC FastPass, by Andy Eadie.
7 https://incompliancemag.com/article/designing-ethernet-
cable-ports-to-withstand-lightning-surges/
8 CST – Computer Simulation Technology webinars.
9 www.a2la.org/regulators .
10 In Compliance Editorial Team.
11 Interference Technology.
12 Electro Magnetic Test Inc. – EMC Testing, Standards etc