IEC 61000-4-21:2011

IEC 61000-4-21 ®
Edition 2.0 2011-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
BASIC EMC PUBLICATION
PUBLICATION FONDAMENTALE EN CEM

Electromagnetic compatibility (EMC) –
Part 4-21: Testing and measurement techniques – Reverberation chamber test
methods
Compatibilité électromagnétique (CEM) –
Partie 4-21: Techniques d'essai et de mesure – Méthodes d'essai en chambre
réverbérante
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IEC 61000-4-21 ®
Edition 2.0 2011-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
BASIC EMC PUBLICATION
PUBLICATION FONDAMENTALE EN CEM

Electromagnetic compatibility (EMC) –
Part 4-21: Testing and measurement techniques – Reverberation chamber test
methods
Compatibilité électromagnétique (CEM) –
Partie 4-21: Techniques d'essai et de mesure – Méthodes d'essai en chambre
réverbérante
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX XE
ICS 33.100.10; 33.100.20 ISBN 978-2-88912-324-7

– 2 – 61000-4-21  IEC:2011
CONTENTS
FOREWORD . 4
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms, definitions and abbreviations . 9
3.1 Terms and definitions . 9
3.2 Abbreviations . 12
4 General . 13
5 Test environments and limitations . 13
6 Applications . 14
6.1 Radiated immunity . 14
6.2 Radiated emissions . 14
6.3 Shielding (screening) effectiveness . 14
7 Test equipment . 14
8 Chamber validation. 15
9 Testing . 16
10 Test results, test report and test conditions . 16
Annex A (informative) Reverberation chamber overview . 17
Annex B (normative) Chamber validation for mode-tuned operation . 41
Annex C (normative) Chamber validation and testing for mode-stirred operation . 50
Annex D (normative) Radiated immunity tests . 56
Annex E (normative) Radiated emissions measurements . 61
Annex F (informative) Shielding effectiveness measurements of cable assemblies,
cables, connectors, waveguides and passive microwave components . 68
Annex G (informative) Shielding effectiveness measurements of gaskets and materials . 72
Annex H (informative) Shielding effectiveness measurements of enclosures . 82
Annex I (informative) Antenna efficiency measurements . 89
Annex J (informative) Direct evaluation of reverberation performance using field
anisotropy and field inhomogeneity coefficients . 91
Annex K (informative) Measurement uncertainty for chamber validation – Emission
and immunity testing . 100
Bibliography . 107

Figure A.1 – Typical field uniformity for 200 independent tuner steps . 32
Figure A.2 – Theoretical modal structure for a 10,8 m × 5,2 m × 3,9 m chamber . 32
Figure A.3 – Theoretical modal structure with small Q-bandwidth (high Q)
th
superimposed on 60 mode . 33
Figure A.4 – Theoretical modal structure with greater Q-bandwidth (lower Q)
th
superimposed on 60 mode . 33
Figure A.5 – Typical reverberation chamber facility . 34
Figure A.6 – Theoretical sampling requirements for 95 % confidence . 34
Figure A.7 – Normalized PDF of an electric field component at a fixed location for a
measurement with a single sample . 35

61000-4-21  IEC:2011 – 3 –
Figure A.8 – Normalised PDF of the mean of an electric field component at one fixed
location for a measurement with N independent samples . 35
Figure A.9 – Normalised PDF of the maximum of an electric field component at a fixed
location for a measurement with N independent samples . 36
Figure A.10 – Chamber working volume . 37
Figure A.11 – Typical probe data . 37
Figure A.12 – Mean-normalized data for x-component of 8 probes . 38
Figure A.13 – Standard deviation of data for E-field components of 8 probes . 38
Figure A.14 – Distribution of absorbers for loading effects test . 39
Figure A.15 – Magnitude of loading from loading effects test . 39
Figure A.16 – Standard deviation data of electric field components for eight probes in
the loaded chamber . 40
Figure B.1 – Probe locations for chamber validation . 49
Figure C.1 – Received power (dBm) as a function of tuner rotation (s) at 500 MHz . 55
Figure C.2 – Received power (dBm) as a function of tuner rotation (s) at 1 000 MHz . 55
Figure D.1 – Example of suitable test facility. 60
Figure E.1 – Example of suitable test facility . 66
Figure E.2 – Relating to the calculation of the geometry factor for radiated emissions . 67
Figure F.1 – Typical test set-up . 71
Figure G.1 – Typical test set-up . 80
Figure G.2 – Typical test fixture installation for gasket and/or material testing . 80
Figure G.3 – Test fixture configured for validation . 81
Figure H.1 – Typical test enclosure installation for floor mounted enclosure testing . 88
Figure H.2 – Typical test enclosure installation for bench mounted enclosure testing . 88
Figure J.1 – Theoretical and typical measured distributions for field anisotropy
coefficients in a well-stirred chamber . 97
Figure J.2 – Theoretical and typical measured distributions for field anisotropy
coefficients in a poorly stirred chamber . 98
Figure J.3 – Typical measured values for field anisotropy coefficients as a function of
N in a well-stirred chamber . 99
Figure K.1 – Average emitted power as a function of frequency for a typical
unintentional radiator . 105
Figure K.2 – Estimated standard uncertainty . 105
Figure K.3 – Mean normalized width (in dB) of a η%-confidence interval . 106
Figure K.4 – Individual mean-normalized interval boundaries (in linear units) for
maximum field strength as a function of the number of independent stirrer positions N . 106

Table B.1 – Sampling requirements . 48
Table B.2 – Field uniformity tolerance requirements . 48
Table J.1 – Typical values for total field anisotropy coefficients for ‘medium’ and ‘good’
reverberation quality . 96

– 4 – 61000-4-21  IEC:2011
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROMAGNETIC COMPATIBILITY (EMC) –

Part 4-21: Testing and measurement techniques –
Reverberation chamber test methods

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61000-4-21 has been prepared by subcommittee 77B: High
frequency phenomena, of IEC technical committee 77: Electromagnetic compatibility, in co-
operation with CISPR subcommittee A: Radio-interference measurements and statistical
methods.
It forms Part 4-21 of IEC 61000. It has the status of a basic EMC publication in accordance
with IEC Guide 107.
This second edition cancels and replaces the first edition published in 2003. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the first
edition.
• In Clause 8, the use and specifications of E-field probes for application to reverberation
chambers has been added. Additional Notes refer to general aspects and procedures of

61000-4-21  IEC:2011 – 5 –
probe calibrations. The specified range for linearity of the probe response is larger and
covers an asymmetric interval compared to that for use in anechoic chambers (see
Annex I of IEC 61000-4-3), because
– the fluctuations of power and fields in reverberation chambers exhibit a larger dynamic
range, and
– the chamber validation procedure is based on using maximum field values, as opposed
to the field itself or its average value,
respectively.
• In Annex A, additional guidance and clarifications on the use of reverberation chambers at
relatively low frequencies of operation (i.e., close to the lowest usable frequency of a given
chamber) are given, and its implications on the estimation of field uncertainty are outlined.
Guidelines on cable-layout have been added. A rationale has been added that explains the
relaxation of the field uniformity requirement below 400 MHz, being a compromise between
scientific-technical and economical reasons when using chambers around 100 MHz. A first-order
correction for the threshold value of the correlation coefficient at relatively low numbers of tuner
positions has been added. Issues regarding the use of non-equidistant tuner positions at low
frequencies are discussed in an additional Note.
• In Annex B, symmetric location of the field probes when the chamber exhibits cylindrical
symmetry has been disallowed, as such placement could otherwise yield a false indication of
field uniformity and chamber performance at different locations. The difference between start
frequency for chamber validation and lowest test frequency has been clarified. The tuner
sequencing for chamber validation and testing is now specified to be equal in both cases. In
sample requirements for chamber validation, emphasis is now on the required minimum number of
independent tuner steps to be used, whereas the minimum recommended number of samples per
frequency interval has been replaced with he number of independent samples that the tuner can
provide per frequency, for use in case when the chamber validation fails for the required minimum
number.
• Annex C now contains more quantitative guidance on the setting of the maximum
permissible stirring speeds that warrant quasi-static conditions of operation for chamber
validation and testing. Consideration is given to all characteristic time scales of all
components or subsystems of a measurement or test. Specific issues relating to chamber
validation, immunity testing and bandwidth are addressed. Particular requirements for field
probes when used with mode stirred operation are listed.
• In Annex D, a requirement for the EUT and equipment not to occupy more than 8 % of the
total chamber volume in immunity testing has been added. The maximum number of
frequency points and the formula to calculate these points have been generalized. A
mandatory specification for including the measurement equipment, test plan and cable
layout in the test report has been added to resolve any dispute in case of discrepancies,
particularly for low-frequency immunity testing.
• Annex E has been extended with further guidance on the value of EUT directivity to be
used in the estimation of radiated power and field. Extended estimates have been added
for the maximum directivity of electrically large, anisotropically radiating EUTs and for
radiated emissions in the presence of a ground plane. A mandatory specification for
including the measurement equipment, test plan and cable layout in the test report has
been added to resolve any dispute in case of discrepancies, particularly for low-frequency
emissions testing.
• In Annex I, some clarifications on antenna efficiency measurements have been added.
• A new Annex K has been added that covers measurement uncertainty in reverberation
chambers. The intrinsic field uncertainty for chamber validation, immunity and emissions
measurements is quantified. Other contributors to measurement uncertainty are listed.

– 6 – 61000-4-21  IEC:2011
The text of this standard is based on the following documents:
CDV Report on voting
77B/619/CDV 77B/640/RVC
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
61000-4-21  IEC:2011 – 7 –
INTRODUCTION
IEC 61000 is published in separate parts according to the following structure:
Part 1: General
General considerations (introduction, fundamental principles)
Definitions, terminology
Part 2: Environment
Description of the environment
Classification of the environment
Compatibility levels
Part 3: Limits
Emission limits
Immunity limits (in so far as they do not fall under the responsibility of the product
committees)
Part 4: Testing and measurement techniques
Measurement techniques
Testing techniques
Part 5: Installation and mitigation guidelines
Installation guidelines
Mitigation methods and devices
Part 6: Generic standards
Part 9: Miscellaneous
Each part is further subdivided into several parts, published either as international standards
or as technical specifications or technical reports, some of which have already been published
as sections. Others will be published with the part number followed by a dash and a second
number identifying the subdivision (example: IEC 61000-6-1).

– 8 – 61000-4-21  IEC:2011
ELECTROMAGNETIC COMPATIBILITY (EMC) –

Part 4-21: Testing and measurement techniques –
Reverberation chamber test methods

1 Scope
This part of IEC 61000 considers tests of immunity and intentional or unintentional emissions
for electric and/or electronic equipment and tests of screening effectiveness in reverberation
chambers. It establishes the required test procedures for performing such tests. Only radiated
phenomena are considered.
The objective of this part is to establish a common reference for using reverberation
chambers to evaluate the performance of electric and electronic equipment when subjected to
radio-frequency electromagnetic fields and for determining the levels of radio-frequency
radiation emitted from electric and electronic equipment.
NOTE Test methods are defined in this part for measuring the effect of electromagnetic radiation on equipment
and the electromagnetic emissions from equipment concerned. The simulation and measurement of
electromagnetic radiation is not adequate for quantitative determination of effects. The defined test methods are
organized with the aim to establish adequate reproducibility and repeatability of test results and qualitative analysis
of effects.
This part of IEC 61000 does not intend to specify the tests to be applied to a particular
apparatus or system. Its main aim is to give a general basic reference to all concerned
product committees of the IEC. The product committees should select emission limits and test
methods in consultation with CISPR. The product committees remain responsible for the
appropriate choice of the immunity tests and the immunity test limits to be applied to their
equipment. Other methods, such as those covered in IEC 61000-4-3, CISPR 16-2-3 and
CISPR 16-2-4 may be used.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60050(161):1990, International Electrotechnical Vocabulary – Chapter 161:
Electromagnetic compatibility
Amendment 1 (1997)
Amendment 2 (1998)
IEC 60068-1, Environmental testing – Part 1: General and guidance
IEC 61000-4-3:2006, Electromagnetic compatibility (EMC) – Part 4-3: Testing and
measurement techniques – Radiated, radio-frequency, electromagnetic field immunity test
Amendment 1 (2007)
___________
For further information consult with CISPR (International Special Committee on Radio Interference) or
Technical Committee 77 (Electromagnetic compatibility).

61000-4-21  IEC:2011 – 9 –
CISPR 16-1-1, Specification for radio disturbance and immunity measuring apparatus and
methods – Part 1-1: Radio disturbance and immunity measuring apparatus – Measuring
apparatus
CISPR 16-2-3, Specification for radio disturbance and immunity measuring apparatus and
methods – Part 2-3: Methods of measurement of disturbances and immunity – Radiated
disturbance measurements
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions together with those in
IEC 60050(161) apply.
3.1.1
antenna
that part of a radio transmitting or receiving system which is designed to provide the required
coupling between a transmitter or a receiver and the medium in which the radio wave
propagates
[IEC 60050-712:1992, 712-01-01]
NOTE For the purpose of this procedure, antennas are assumed to have an efficiency of 75 % or greater.
3.1.2
electromagnetic wave
EM wave
wave characterized by the propagation of a time-varying electromagnetic field and caused by
acceleration of electric charges
[IEC 60050-705:1995, 705-01-09, modified]
3.1.3
far field region
that region of the electromagnetic field of an antenna or unintentional radiator wherein the
predominant components of the field are those which represent a propagation of energy and
wherein the angular field distribution is essentially independent of the distance from the
antenna
NOTE 1 In the far field region, all the components of the electromagnetic field decrease in inverse proportion to
the distance from the antenna.
NOTE 2 For a broadside antenna having a maximum overall dimension, D, which is large compared to the wave-
length, λ, the far field region is commonly taken to exist at distances greater than from the antenna in the
2D λ
direction of maximum radiation.
[IEC 60050-712:1992, 712-02-02]
the region far from a source or aperture where the radiation pattern does not vary with
distance from the source
[IEC 60050-731:1991, 731-03-92]
3.1.4
field strength
magnitude of the electromagnetic field created at a given point by a radio transmitting system
operating at a specified characteristic frequency with specified installation and modulation
conditions
[IEC 60050-705:1995, 705-08-31]

– 10 – 61000-4-21  IEC:2011
NOTE 1 The term "electric field strength" (in V/m) or "magnetic field strength" (in A/m) is used according to
whether the magnitude of the electric or magnetic field, respectively, is measured. In the near-field region, the
relationship between the electric and magnetic field strength and distance depends on the specific configuration
involved. The power flux density of the field is similarly indeterminate.
NOTE 2 In the far zone, field strength is sometimes identified with power flux density P. For a plane wave in free
space, P = E / η , where
V
E is the electric field strength, and
η is the intrinsic impedance of free space, approximately equal to 120π Ω.
V
3.1.5
polarization
property of a sinusoidal electromagnetic wave or field vector defined at a fixed point in space
by the direction of the electric field strength vector or of any specified field vector; when this
direction varies with time, the property may be characterized by the locus described by the
extremity of the considered field vector
[IEC 60050-726:1982, 726-04-01]
3.1.6
reverberation chamber
room specially designed to have a very long reverberation time
[IEC 60050-723:1997, 723-03-30]
(reverberation room) room having a long reverberation time, especially designed to make the
field therein as diffuse as possible
NOTE 1 The room consists of a shielded enclosure that is generally equipped with mechanical tuners/stirrers that
change (stir) the boundary conditions within the enclosure and, thus, alter the structure of the electromagnetic
fields within the enclosure.
[IEC 60050-801:1994, 801-31-13, modified]
NOTE 2 Reverberation rooms are used in particular for the measurement of absorption coefficients of materials
and measurement of the power emitted by intentional or unintentional radiating sources.
NOTE 3 Testing in a reverberation chamber can be described as a stochastic process in which the mechanical
tuners/stirrers “stir” the “modes” inside the enclosure. Therefore, such chambers is also called stirred-mode, mode-
stirred or mode-tuned chamber.
3.1.7
quality factor (of a reverberation chamber)
Q
(quality factor) frequency-dependent measure of sharpness of the resonance, equal to 2π
times the ratio of the maximum stored energy to the energy dissipated during one period
[IEC 60050-151:2001, 151-15-46, modified]
measure of how well the chamber stores energy (see Clause A.6 [2] )
NOTE For a given chamber, Q varies as a function of frequency and can be calculated using the following formula:
16π V P
AveRec
Q = (4)
P
η η λ
Input
Tx Rx
n
where
V is the chamber volume (in m ),
___________
Numbers in square brackets refer to the reference documents in the respective annexes.

61000-4-21  IEC:2011 – 11 –
λ is the wavelength (in m),
P /P is the ratio of the received power to the input power, each averaged over one complete
AveRec Input
tuner/stirrer sequence,
denotes averaging with respect to the number of antenna locations and orientations, n,
n
η and η are the antenna efficiency factors (dimensionless) for the Transmit (Tx) and Receive (Rx)
Tx Rx
antennas, respectively. If manufacturer’s data is not available then the efficiency can be assumed to be
0,75 for log periodic antennas and 0,9 for horn antennas,
n is the number of antenna locations and orientations that the Q is evaluated for. Only one location is
required as a minimum; however, multiple locations and orientations may be evaluated and the data
averaged over them.
3.1.8
Q-bandwidth (of a reverberation chamber)
BW
Q
measure of the frequency range over which the modes in a reverberation chamber are
correlated (see Clause A.2)
NOTE The BW of a reverberation chamber can be calculated using the following formula:
Q
BW = f/Q (5)
Q
where
f is the frequency (in Hz),
Q is the quality factor defined in 3.1.7.
3.1.9
malfunction
loss of capability of the equipment to initiate or sustain a required function, or the initiation of
undesired spurious action which might result in adverse consequences
NOTE The criteria of functional acceptance have to be precisely specified.
[IEC 60050-393:2003, 393-17-79]
3.1.10
emission
phenomenon by which energy emanates from a source in the form of waves or particles
[IEC 60050-702:2003, 702-02-03]
3.1.11
tuner/stirrer
mechanical device constructed from low-loss electrically conductive material which alters the
electromagnetic boundary conditions inside a reverberation chamber
NOTE In general, a reverberation chamber is a shielded enclosure with the smallest dimension being large with
respect to the wavelength at the lowest usable frequency. The chamber is normally equipped with a mechanical
tuning/stirring device whose dimensions are significant fractions of the chamber dimensions and of the wavelength
at the lowest usable frequency. When the chamber is excited with RF energy, the boundary conditions of the
resulting multi-mode electromagnetic environment can be altered by the mechanical tuner/stirrer. The resulting
environment is statistically uniform and statistically isotropic (i.e., the energy arriving from all aspect angles with all
directions of polarizations) when considered over a sufficiently large number of positions of the mechanical
tuner/stirrer.
3.1.12
electromagnetic mode
one solution of Maxwell’s equations representing an electromagnetic field in a certain space
domain and belonging to a family of independent solutions defined by specified boundary
conditions
– 12 – 61000-4-21  IEC:2011
[IEC 60050-705:1995, 705-01-12]
3.1.13
validation
process of confirming that a finalized instrumentation, control system (hardware and software)
and test facility complies with all of its functional, performance and interface requirements
[IEC 60050-394:2007, 394-40-42, modified]
3.1.14
chamber validation
process of confirming that a chamber complies with all of its functional, performance and
interface requirements
[IEC 60050-394:2007, 394-40-42, modified]
3.1.15
intrinsic field uncertainty
IFU
contribution to the overall uncertainty budget that is caused by the random (statistical) nature
of the field inside a reverberation chamber
NOTE Typically, the intrinsic field uncertainty is considerably larger than the measurement instrumentation
uncertainty in typical operation of a reverberation chamber, except when the chamber has an exceptionally high
quality factor. As a result, the IFU is typically the only or main contribution to be considered in estimating the
overall uncertainty during test or measurement.
3.1.16
working volume
region defined by 8 points inside the chamber at sufficient distance away from the walls to
avoid boundary effects, for rectangular chambers typically defined by the corners of a cubic or
parallelepiped region at quarter-wavelength distance from the nearest walls
NOTE For frequencies below 100 MHz, the distances can be restricted to 0,75 m.
3.2 Abbreviations
AVF Antenna Validation Factor
CVF Chamber Validation Factor
CDF Cumulative Distribution Function
CISPR Comité International Spécial des Perturbations Radioélectriques
CLF Chamber Loading Factor
CW Continuous Wave
EM Electromagnetic
EMC Electromagnetic Compatibility
EMI Electromagnetic Interference
EUT Equipment Under Test
IEC International Electrotechnical Commission
IEEE Institute of Electrical and Electronics Engineers
IF Image Frequency
IFU Intrinsic Field Uncertainty
IL Insertion Loss
ISO International Organization for Standardization
___________
International Special Committee on Radio Interference

61000-4-21  IEC:2011 – 13 –
LUF Lowest Usable Frequency
MIU Measurement Instrumentation Uncertainty
MU Measurement Uncertainty
OATS Open Area Test Site
PDF Probability Density Function
RC Reverberation Chamber
RE Radiated Emissions
RF Radio Frequency
RMS Root Mean Square
rps revolutions per second
RSS Root Sum of the Squares
Rx Receive (antenna)
SE Shielding Effectiveness
SW Square Wave modulation
TFVF Test Fixture Validation Factor
Tx Transmit (antenna)
4 General
Most electronic equipment is, in some manner, affected by electromagnetic radiation. Sources
of radiation can be natural or man-made in origin and can be intentional or unintentional.
Examples of intentional radiators are wireless and personal communication systems. Examples
of unintentional radiators are welders, thyristors, high-speed data buses, fluorescent lights,
switches operating inductive loads, etc.
Realistic environments for propagation of electromagnetic waves are often characterized by
multiple reflections and multipath effects. Reverberation chambers go some way to simulate
such complex environments in an extreme manner (worst-case effect) and may be more
representative than other EMC test methods in this respect. An advantage of reverberation
chambers is the ability to generate a statistically isotropic, homogeneous, unpolarized and
uncorrelated interior field, through action of the tuner/stirrer.
High-level electromagnetic fields are easily and safely generated using reverberation chambers.
The high quality factor or “Q” of such chambers allows fairly high field strengths to be generated
with relatively moderate input powers (resonant fields). The absence of absorber makes
generation of high field levels safer as the risk of igniting absorbers is eliminated. Adequate
screening of the enclosure confines the high fields to the interior of the chamber.
5 Test environments and limitations
The reverberation chamber method is suitable for performing tests from relatively low to
extremely high field levels. Due to the high level of isolation from the ambient environment,
both emissions and immunity tests can be performed for most commercial requirements
without limitations. At present, the IEC sets the transition frequency between radiated and
conducted testing at 80 MHz for immunity testing.
NOTE IEC 61000-4-6 also defines test methods for establishing the immunity of electrical and electronic
equipment against conducted electromagnetic energy. It covers frequencies below 80 MHz.
As stated in Annex A, the frequency range of tests is determined by the size and construction
of the chamber and the effectiveness of the mechanical tuner(s) in altering the spatial field
pattern. There are no fundamental restrictions with regard to the shape and size of enclosures

– 14 – 61000-4-21  IEC:2011
eligible for use as reverberation chambers. However, good reverberant properties at a
specified frequency of operation require a minimum chamber size. Room-sized reverberation
3 3
chambers (e.g., volumes between 75 m to 100 m ) are typically operated from 200 MHz to
18 GHz without limitations. Operation below 200 MHz requires chambers that are larger than
the typical shielded room.
6 Applications
6.1 Radiated immunity
The use of reverberation chambers for performing radiated immunity testing is covered in
Annex D. This annex covers test set-up, chamber validation, and test procedures. Injecting a
predetermined level of RF power into the chamber generates the desired field strength within
the chamber. This predetermined level of RF power is derived from chamber validation data
described in Annexes B and C.
6.2 Radiated emissions
The use of reverberation chambers to measure radiated emissions is covered in Annex E. The
described method measures the amount of RF power radiated by the EUT within the
measurement bandwidth. As with radiated immunity testing, chamber validation data
described in Annexes B and C are used to determine radiated emissions levels.
6.3 Shielding (screening) effectiveness
Three annexes are devoted to performing screening effectiveness measurements. Screening
effectiveness measurements of cable assemblies, cables, connectors, waveguides and
passive microwave components are described in Annex F. Annex G covers screening
effectiveness of gaskets and materials. The approach outlined in Annex G uses a nested
chamber methodology (e.g., a reverberation chamber located inside a larger reverberation
chamber). Annex G also covers validation of test fixtures that are usually necessary for
conducting screening effectiveness measurements on gaskets and materials. Minor
differences in test fixture design/ construction can have significant influence on test results.
Fixture materials, bolt spacing, surface finishes, torque settings, etc. shall all be controlled in
order to get repeatable results. Due to the large number of variations that would be needed in
order to accommodate the many different gaskets and materials that require evaluation, this
annex does not contain detailed design guidance for test fixtures. Annex H covers screening
effectiveness measurements of enclosures. As in Annex G, the methodology described in
Annex H uses the “nested chamber” approach.
7 Test equipment
The following types of test equipment are recommended:
– Reverberation chamber: having a size that is adequate to maintain a multi-mode
electromagnetic environment with respect to the lowest test frequency. This implies that
the chamber dimensions in all directions shall be large compared to the wavelength;
– Mechanical tuner(s)/stirrer(s) (see Annex A): having one dimension that is at least one-
quarter wavelength at the lowest frequency. Each tuner/stirrer should also be as large as
possible with respect to the overall chamber size in that one dimension and should be at
least three-quarters of the smallest chamber dimension. In addition, each tuner/stirrer
should be shaped asymmetrically, i.e., such that a non-repetitive field pattern is obtained
over one revolution of the tuner/stirrer;
– Field generating antennas (see Annex B): log periodic or other well-matched antenna
capable
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