SIST R210-010:2003

SLOVENSKI STANDARD
SIST R210-010:2003
01-december-2003
Electromagnetic compatibility - Emission measurements in fully anechoic
chambers
Electromagnetic compatibility - Emission measurements in fully anechoic chambers
Elektromagnetische Verträglichkeit - Störaussendung in Absorberräumen
Compatibilité électromagnétique - Émission en chambres anéchoïques entiers
Ta slovenski standard je istoveten z: R210-010:2002
ICS:
33.100.10 Emisija Emission
SIST R210-010:2003 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST R210-010:2003

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SIST R210-010:2003
CENELEC R210-010
REPORT June 2002
English Version
Electromagnetic compatibility -
Emission measurements in fully anechoic chambers
Compatibilité électromagnétique - Elektromagnetische Verträglichkeit -
Émission en chambres anéchoïques Störaussendung in Absorberräumen
entiers
This CENELEC Report has been prepared by TC 210, Electromagnetic compatibility (EMC). It
was approved by TC 210 on 2001-11-13 and was endorsed by the CENELEC Technical Board
on 2002-03-05.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech
Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg,
Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2002 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. R210-010:2002 E

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Foreword
This Technical Report has been prepared by the joint WG 4 of CENELEC TC 210, Electromagnetic
compatibility, and SC 210A, EMC Products.
It was approved for publication by the CENELEC Technical Board on 2002-03-05.
_____________
Contents
1 Scope.3
2 References .3
3 Definitions and abbreviations .4
3.1 Definitions.4
3.2 Abbreviations.5
4 Test and measurement equipment.5
4.1 Fully Anechoic Rooms (FARs).5
4.2 Antenna .5
5 Anechoic Room performance.5
5.1 Theoretical normalised site attenuation .5
5.2 Room validation procedure.7
5.3 Anechoic room requirements.11
6 Emission measurement.11
6.1 Test set up.11
6.2 EUT position .12
6.3 Cable layout and termination.14
7 Test procedure.15
8 Test plan.15
9 Test report.16
Annex A Determining the Site Reference .17
Annex B (informative) Limit values.19
Annex C (informative) Comparison of measurement uncertainties for 3 m OATS and
3 m FAR.25
Annex D (informative) Derivation of free space NSA formula.30
Annex E (informative) Corrections of field strength for test distance.33
Annex F (informative) NSA measurements with biconical antennas .35
Annex G (informative) Measurement of Balun imbalance .38
Annex H (informative) The FAR project .39

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1 Scope
This technical report applies to emission measurements of radiated electromagnetic fields in Fully
Anechoic Rooms in the frequency range from 30 MHz to 18 GHz. This report covers the frequency
range from 30 MHz – 1000 MHz. The frequency range above 1 GHz is under consideration, due to the
absence of practical experience.
This report describes the validation procedure for the Fully Anechoic Room (FAR) for radiated
emission tests and the procedures to carry out the tests (e.g. test set up, EUT position, cable layout
and termination, test procedures). Recommendations for the relation between FAR emission limits and
common Open Area Test Site (OATS) emission limits given in standards such as EN 55011 and
EN 55022 are given in Annex B.
This FAR emission method may be chosen by product committees as an alternative method to
emission measurement on an Open Area Test Site (OATS) as described in CISPR 16. In such cases,
the product committee should also define the appropriate limits. Typical measurement uncertainty
values for FARs and OATS are given in Annex C.
2 References
This technical report incorporates by dated or undated reference, provisions from other publications.
These references are cited at the appropriate places in the text and the publications are listed
hereafter. For dated references, subsequent amendments to or revisions of any of these publications
apply to this European Standard only when incorporated in it by amendment or revision. For undated
references the latest edition of the publication referred to applies (including amendments).
Publication Title
CISPR 16-1 Specification for radio disturbance and immunity measuring apparatus and
methods – Part 1: Radio disturbance and immunity measuring apparatus
CISPR 16-2 Specification for radio disturbance and immunity measuring apparatus and
methods – Part 2: Methods of measurement of disturbance and immunity
CISPR 16-3 Reports and recommendations of CISPR
EN 50147-1 Anechoic chambers – Part 1: Shield attenuation measurement
EN 55011 Industrial, scientific and medical (ISM) radio-frequency equipment – Radio
disturbance characteristics – Limits and methods of measurement (CISPR 11,
mod.)
EN 55022 Information technology equipment – Radio disturbance characteristics - Limits
and methods of measurement (CISPR 22, mod.)
IEC 60050-161 International Electrotechnical Vocabulary (IEV) – Chapter 161: Electromagnetic
compatibility
ISO/IEC 17025 General requirements for the competence of testing and calibration
laboratories
ANSI C 63.4/ American national standard for methods of measurement of radio-noise
emissions from low voltage electrical and electronic equipment in the range of
9 kHz – 40 GHz
ANSI C 63.5 Electromagnetic compatibility – Radiated emission measurements in
Electromagnetic Interference (EMI) control – Calibration of antennas

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3 Definitions and abbreviations
3.1 Definitions
For the purpose of this technical report, the following definitions and the definitions contained in
IEC 60050-161 apply.
3.1.1
Fully Anechoic Room (FAR)
shielded enclosure whose internal surfaces are lined with radio frequency absorbing material (i.e.
RAM), that absorbs electromagnetic energy in the frequency range of interest.
NOTE The fully Absorber-Lined Room is intended to simulate free space environment.
3.1.2
Equipment Under Test (EUT)
test sample including connected cables.
NOTE The EUT may consist of one or several pieces of equipment.
3.1.3
test volume
region of the Room that meets the NSA requirements of this technical report and which contains the
EUT as fully set up
3.1.4
free space antenna factor (AF )
FS
antenna factor of an antenna which is not affected by mutual coupling to conducting bodies in the
environment of the antenna
NOTE It is also the antenna factor measured when the antenna under test is illuminated by a plane wave, which implies
that the source antenna is in the far-field of the antenna under test. Antenna factor is defined as the ratio of the magnitude of
the E-field in which the antenna is immersed to the voltage at the antenna output of a given transmission line impedance,
usually 50 �.
3.1.5
antenna reference point
physical position on the antenna from which the separation distance to the defined reference plane on
the EUT is measured
NOTE For dipole and biconical antennas this will be the centre of the antenna in line with the central antenna elements. For an
LPDA antenna and a hybrid antenna, the reference point is the mark on the antenna provided by the manufacturer for this
purpose. The reference point is approximately at the mid-way point between the array elements that are active at the top and
bottom frequencies at which the measurements are being made. Hybrid antenna is here defined as a combination of a biconical
and LPDA antenna which has a frequency range including 30 MHz to 1 GHz.
3.1.6
Normalised Site Attenuation (NSA)
site attenuation obtained from the ratio of the source voltage connected to a transmitting antenna and
the received voltage as measured on the receiving antenna terminals
NOTE Normalised site attenuation is site attenuation in decibels minus the antenna factors of the transmit and receive antenna
factors. NSA was first introduced for evaluation of open area test sites with ground planes and was measured by height
scanning the receive antenna. In this technical report, NSA is measured in a quasi-free space environment, and because there
is no deliberate ground plane height scanning is not required.
3.1.7
test distance (d )
t
distance measured from the reference point of the antenna to the front of the boundary of the EUT

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3.2 Abbreviations
EUT Equipment Under Test
FAR Fully Anechoic Room
NSA Normalised Site Attenuation
AF antenna factor (free space)
FS
LPDA Log-Periodic Dipole Array
OATS Open Area Test Site
RS reference site
SA
site attenuation
SA measurement of SA made on RS
R
NEC Numerical Electromagnetic Code
4 Test and measurement equipment
Equipment in accordance with CISPR 16 shall be used.
4.1 Fully Anechoic Rooms (FARs)
A Fully Anechoic Room is required for the emission testing in which the radiated electromagnetic
waves propagate as in free space and only the direct ray from the transmitting antenna reaches the
receiving antenna. All indirect and reflected waves shall be minimised with the use of proper absorbing
material on all walls, the ceiling and the floor of the FAR.
The screening of the FAR shall have an adequate attenuation level to avoid outside electromagnetic
radiation entering the Room and influencing the measurement results. The shield attenuation is
measured in accordance with EN 50147-1. Shielding recommendations are given in the technical
report 'recommendation on shielded enclosures'.
4.2 Antenna
Linear polarised antennas shall be used to measure the emitted electromagnetic field of the EUT.
Biconical or log-periodic antennas and hybrid antennas are typical antennas used. The free space
antenna factor shall be used. CISPR 16-3 clause 4.7 gives parameters of broadband antennas.
However no length limitation on LPDA or hybrid antennas is given. Subclauses 5.5.4 and 5.5.5 of
CISPR 16-1 give information on antennas. Subclause 5.5.5.2 states “it is essential that the variation of
the effective distance of the antenna from the source and its gain with frequency be taken into
account”. Antennas over 1,5 m in length could increase the uncertainties of emission testing using a
separation of 3 m between the reference point of the antenna and the front of the EUT.
5 Anechoic Room performance
5.1 Theoretical normalised site attenuation
The Site Attenuation (SA) is the loss measured between the connectors of two antennas on a
particular site. For a free space environment the SA (in dB) can be defined by Equation 1 (see
Annex D):

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� �
� �
� �
� �
� �
� �
� 5Z � d
(1)
O
SA � 20log � 20log f � AF � AF ��dB
� �� �
10� � 10 m R T
2�
� �� 1 1 �
� �
1� �
� �
2 4
� �
� �
���d ���d
� �
� �
where AF and AF are the antenna factors of the receive and transmit antenna in dB/m, d is the
R T
distance between the reference points of both antennas in meters, Z is the reference impedance (i.e.
0
50 �), ß is defined as 2�/� and f is the frequency in MHz.
m
The theoretical Normalised Site Attenuation (NSA) in dB is defined as site attenuation with respective
antenna factors subtracted, thus:
� �
� �
� �
� �
� �
� �
� 5Z � d
O
� �
NSA � 20log � � � 20log f (2)
� �
calc 10 10 m
� �
2� � �
�� � 1 1 �
1� �
� �
� �
2 4
� �
���d ���d
� �
� �
� �
40
30
20
10
0
-10
-20
30 m
-30
10 m
 5 m
-40
 3 m
-50
10 100 1000 10000 100000
Frequency [MHz]
Figure 1a - Plot of theoretical NSA values in free space for far field conditions (Equation 3)
In far-field conditions Equation 2 simplifies to Equation 3 by omitting the near field terms:
� 5Z d �
O
(3)
NSA � 20log � 20log f
calc 10 10 m
� �
2�
� �
NSA [dB]

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0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
-1.2
2.3
-1.4
0 2 4 6 8 10 12 14 16
Separation, m
Figure 1b - Difference in theoretical NSA between Equation 2 and Equation 3
Distances relate to a frequency of 30 MHz
Using the simplified equation (Equation 3) the error is less than 0,1 dB at frequencies above 60 MHz
for 5 m distance and above 110 MHz for 3 m distance. Figure 1b shows the worst case near-field error
which is at 30 MHz. However at higher frequencies there are Fresnel zone errors for large antennas
which is treated in Annex F.
Equation 1 and Equation 2 account for near field effects of small antennas. In this context, using a
transmit antenna less than 40 cm long, near-field effects become significant (> 0,2 dB) where the
receive antenna length is greater than a quarter of the separation distance. This assumes the use of a
1,4 m long biconical antenna at 300 MHz. The graph in Annex F shows that the error is less than
0,2 dB for a separation of 3 m and a maximum frequency of 200 MHz (it is common to change to a log
antenna above 200 MHz). To cater for the general use of antennas (biconicals up to 300 MHz, or
bilogs), the site reference method (6.2.1 and Annex A) shall be used for chamber validation at
distances up to 5 m. In this method the site attenuation measured in the FAR are compared to those
measured on a free space reference site.
5.2 Room validation procedure
The test volume must meet the Room requirements given in 5.3. The shape of the test volume will be
a cylinder, due to the rotation of the EUT on a turntable. The minimum height and diameter of the test
volume shall be 1 m. The height and diameter do not have to be equal between the maximum and
minimum values.
A single SA measurement is insufficient to pick up possible reflections from the construction and/or
absorbing material comprising the walls, the floor and the ceiling of the Fully Anechoic Room.
In validating the Fully Anechoic Room SA measurements shall be performed at 15 measurement
points for horizontal and vertical polarisation of the antennas:
1) at three heights of the test volume: bottom, middle and top of test volume
2) at five positions in all three horizontal planes: the centre, left, right, front and back position of
the horizontal plane
Difference, dB

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For SA measurements, two broadband antennas shall be used: one transmit antenna at the
measurement points of the test volume and one receive antenna outside this test volume at a
prescribed orientation and position. The transmit antenna shall approximate an omnidirectional
antenna pattern and shall have a maximum dimension of 40 cm. Typical antennas are biconical
antennas. The receive antenna used during the Room validation shall be of the same type as the
receive antenna used during radiated emission testing of the EUT.
The frequency range 30 MHz to 1 GHz can be covered with one antenna, a hybrid antenna. The
measurement results may be different if separate biconical and LPDA antennas are used.
For FAR validation the receive antenna shall be in the position of the middle level of the test volume
as shown in Figure 2 and operated in horizontal and vertical polarisation. The distance between
reference points of the receive and transmit antenna shall be d . The height of the measurement
nominal
volume is less than the height of the test volume by the height of the transmit antenna. This is in order
that the tip of the vertically polarised transmit antenna does not protrude above the top plane or below
the top plane of the test volume. This treatment has not been applied, by reducing the diameter, to the
horizontally aligned antenna, because it is room height rather than width which is at issue.
When varying the transmit antenna to the other positions of the test volume the receive antenna shall
be moved to d . In all positions and polarisation the antennas shall face each other (receive
nominal
antenna tilted). When the transmit antenna is placed in the upper and bottom level, the receive
antenna remains in the middle level. The transmit antenna is moved to all 15 positions, the 30 site
validation measurements are performed. Tilting of the antennas implies that only one site reference
measurement is needed to cover all 15 positions.
The back-position does not need to be taken into account if the distance between the boundary of the
test volume and tips of the absorber is more than 1 m. Experiments and modelling have shown that
this distance could be reduced to 0,5 m and further work may be needed to confirm this.

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Figure 2 – Measurement points in room validation procedure
For each measurement the frequency range is incrementally swept. The frequency step size shall not
exceed 1% and need not be less than 1 MHz as given in Table 1.
Table 1 - Frequency ranges and step sizes
Frequency range Maximum Frequency step
MHz MHz
30 – 100 1
100 – 500 5
500 – 1000 10
For validating the Room performance, two methods exist:
1) the site-reference method, preferred for a test distance up to 5 m
2) the NSA-method, preferred for test distances larger than 5 m
NOTE With reference to the site reference method, achieving quasi-free space conditions requires expertise. The problem is in
sufficiently eliminating reflections from the ground. In practice this probably confines the site reference method as described in
Annex A to distances of less than 5m. On the other hand there are also limitations with the NSA method in that the free space
antenna factor is used. At 3 m distance the antenna coupling is not negligible and expertise is required to correct the free space
antenna factor for coupling. A practical solution is to confine the NSA method to distances greater than 5 m. Corrections, such
as to phase centre, are required, but this can be done precisely.

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The intention of the SA measurement is to give "0 dB" deviation on an ideal site. Any measure can be
taken to improve the measurement accuracy as long as it is not contradictory to the described setup
and procedure and does not hide any bad Room performance (e.g. smoothing).
The accuracy in the validation procedure can be improved by the following measures:
1) The cables are extended by at least 2 m behind each antenna before dropping the cable to the
ground for a vertically polarised antenna. The cables will - if possible - extend straight back to
the bulkhead connectors in the wall of the room. Additional possibilities are ferrite rings around
cables.
2) Any bad match of the antennas is padded out by use of attenuators at the antenna connectors
(e.g. 6 dB or 10 dB).
3) Antennas with a good balance of the balun shall be used, giving a change in receiver reading
of less than � 0,5 dB when the illuminated antenna is inverted with respect to its input cable
(see Annex G).
4) The directional pattern of the receive antenna can be accounted for on site validations with the
NSA method.
The Room validation procedure shall be applied at a regular interval (to detect long-term changes in
Room characteristics) and when changes in the Fully Anechoic Room are implemented or occurred,
that might influence the electromagnetic wave transmission characteristics of the Room.
5.2.1 The site reference method
The SA measurement of the antenna pair (transmit and receive antenna) on a quasi free space test
site is required as reference. The antenna pair that is used for site validation is calibrated as a pair on
a reference site. In Annex A the procedure of determining this Site Reference (SR) is described. This
method accounts for coupling of the antennas and near field effects which can have a significant
influence at a 3 m test distance, reducing as the distance increases to 5 m.
The site validation for each measurement point is performed in three steps:
1) The insertion loss (M ) is measured in dB with the cables connected together.
0
2) The transmission loss (M ) is measured in dB with the cables connected to the antennas.
1
3) The deviation of the measured site attenuation from site reference is calculated according
Equation 4:
(4)
Dev � M � M � SR�d�
0 1
5.2.2 The NSA method
The NSA method is recommended for distances equal to or greater than 5 m. The free space antenna
factors of the transmit and receive antenna are required for this procedure. The theoretical NSA is a
simple calculation between point sources, and therefore does not account for the radiation patterns of
the actual antennas used. As the transmit antenna is moved throughout the volume it will be slightly
off the boresight direction of the receive antenna. The effects of the radiation pattern are small and
can be corrected for assuming the pattern is that of a Hertzian dipole, or cos �. The phase-centre
variation of log.-periodic and bicon.-log.-periodic antennas have also to be taken into account –
see 6.1.
The site validation for each measurement point is performed in four steps:
1) The insertion loss (M ) is measured in dB with the cables connected together.
0
2) The transmission loss (M ) is measured in dB with the cables connected to the antennas.
1

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3) The measured NSA (NSA ) is calculated in dB according to Equation 5:
m
(5)
NSA � M � M � AF � AF in dB
m 0 1 T R
AF and AF are free space antenna factors in dB/m.
T R
4) The deviation of the measured NSA (Equation 5) from the theoretical NSA (Equation 2) is
calculated according to Equation 6. NSA is given by equation 2 in 5.1.
calc
NOTE The real distance d between the reference points of the transmit and receive antenna has to be used in
Equation 2, not the nominal test distance d . i.e. if the LPDA antenna has been calibrated at its true phase centre
nominal
at each frequency, a phase centre correction must be included if a fixed distance (to the reference point on the LPDA)
is used.
Dev � NSA � NSA in dB (6)
calc m
5.3 Anechoic room requirements
A measurement site shall comply with the two following requirements:
1) the Room validation procedure shall provide deviations which are within � 4 dB of the site
reference values (or the theoretical NSA values for the NSA method) for both horizontal and
vertical polarisation and for the test volume intended to be occupied by the EUT.
2) the maximum diameter and height of the EUT is equal or less than the test distance divided by
2. This requirement ensures acceptable uncertainties in EUT emission testing. These include
distance variation to the emission source, antenna directivity and near field effects. The
maximum diameter as a function of 3 test distances is given in Table 2.
Table 2 - Relation between maximum diameter of EUT and test distance
Maximum diameter and Test distance
height of EUT
1,5 m 3,0 m
2,5 m 5,0 m
5,0 m 10,0 m
The uncertainty budget of the site evaluation measurement shall be available.
6 Emission measurement
6.1 Test set up
The same type of antenna shall be used for EUT emission testing as the receive antenna used for
Room validation testing. The antenna height is fixed at the geometrical centre height of the test
volume. The test distance is measured from the reference point of the antenna to the boundary of the
EUT. In the case of a difference between the reference point on an antenna and the phase centre, a
correction factor, C dB, shall be applied to obtain the field strength at the test distance (see Annex E).
R
(6.1a)
C � 20log��d � P � R� d�
R f
E-field strength is given by Equation 6.1b:
(6.1b)
E � V � AF � C
f f FS( f ) R

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The correction factor C is only applicable if the calibration distance is different from the measurement
R
distance.
where:
f
= frequency, (MHz).
d
= the required separation from the source to the reference point (m).
Pf = phase centre position as a function of frequency, (m from tip of the LPDA).
R = distance of the LPDA reference point from the antenna tip (m).
E = E-field at distance R from source (dBV/m).
f
V = voltage at output of antenna at frequency f (dBV).
f
AF
FS(f) = antenna factor (free space) for E-field at the phase centre (dB/m).
C = phase centre correction factor
R
Figure 3 illustrates a typical test set up.
a
Test volume
b X
EUT volume
80 cm
X
Antenna
EUT
box EUT cabling
1)
80 cm
X
A
h d
m
e
Ferrite
c
clamp 2)
A: turntable and EUT-support
2X:
1,5 m; 2,5 m , 5 m
h : middle level of the test volume
m
d: 3 m; 5 m or 10 m
a, b, c and e:
� 0,5 m recommended (� 1 is discretionary)
1): The antenna cable layout shall be the same as in the validation procedure
2): Ferrite clamp under consideration
Figure 3 - Typical test set-up in FAR, where a, b, c and e depend on the room performance
The EUT shall be placed on a turntable to enhance the emission testing procedure. The turntable can
be arranged above the floor absorbers. The turntable, antenna mast and any supporting floor material
shall be transparent to electromagnetic waves (relative permitivity, є , as near to one as practicable).
r
6.2 EUT position
The EUT shall be configured, installed, arranged and operated in a manner consistent with typical
applications. Interface cables shall be connected to each type of interface port of the EUT.

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If the EUT consists of separate devices the space between the devices shall be in normal
configuration but with 10 cm separation if possible. Interconnecting cables shall be bundled and
separated from each other. The bundle shall be around 30 to 40 cm long and longitudinal to the cable.
Ancillary equipment, which is required to exercise the EUT but does not form part of the EUT, shall be
located outside the screened room.
The entire EUT shall fit in the test volume.
To improve the measurement repeatability, the following guidelines shall be taken into account:
1) Smaller table-top equipment (including cabling) will be placed in the geometrical centre
(horizontally and vertically) of the calibrated volume (see Figure 4).
2) The bottom of larger table-top equipment (Figure 5) and floor standing equipment will coincide
with the bottom of the test volume.
Figure 4 and Figure 5 illustrate the set up of several types of EUT’s in the Fully Anechoic Room. Work
is in progress to decide the appropriate termination condition for cables exiting the volume. Ferrite
clamps are shown here for purposes of illustration.
Test volume
X
EUT volume
80 cm
X
Antenna
EUT
EUT cabling
1) box
80 cm
X A
d
Ferrite
clamp 2)
A: turntable and EUT-support
2X: 1,5 m; 2
...