CISPR 16-1-4:2019/AMD1:2020

CISPR 16-1-4 ®
Edition 4.0 2020-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
INT ERNATIONAL SPECIAL COMMITTEE ON RADIO INTERFERENCE
C OMITÉ INTERNATIONAL SPÉCIAL DES PERTURBATIONS RADIOÉLECTRIQUES

AMENDMENT 1
AMENDEMENT 1
Specification for radio disturbance and immunity measuring apparatus
and methods –
Part 1-4: Radio disturbance and immunity measuring apparatus – Antennas
and test sites for radiated disturbance measurements
Spécifications des méthodes et des appareils de mesure des perturbations
radioélectriques et de l'immunité aux perturbations radioélectriques –
Partie 1-4: Appareils de mesure des perturbations radioélectriques et de
l'immunité aux perturbations radioélectriques – Antennes et emplacements
d'essai pour les mesures des perturbations rayonnées

CISPR 16-1-4:2019-01/AMD1:2020-06(en-fr)

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CISPR 16-1-4 ®
Edition 4.0 2020-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
INT ERNATIONAL SPECIAL COMMITTEE ON RADIO INTERFERENCE

C OMITÉ INTERNATIONAL SPÉCIAL DES PERTURBATIONS RADIOÉLECTRIQUES

AMENDMENT 1
AMENDEMENT 1
Specification for radio disturbance and immunity measuring apparatus

and methods –
Part 1-4: Radio disturbance and immunity measuring apparatus – Antennas

and test sites for radiated disturbance measurements

Spécifications des méthodes et des appareils de mesure des perturbations

radioélectriques et de l'immunité aux perturbations radioélectriques –

Partie 1-4: Appareils de mesure des perturbations radioélectriques et de

l'immunité aux perturbations radioélectriques – Antennes et emplacements

d'essai pour les mesures des perturbations rayonnées

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.100.10; 33.100.20 ISBN 978-2-8322-8450-6

– 2 – CISPR 16-1-4:2019/AMD1:2020
© IEC 2020
FOREWORD
This amendment has been prepared by subcommittee CISPR A: Radio-interference
measurements and statistical methods, of IEC technical committee CISPR: International special
committee on radio interference.
The text of this amendment is based on the following documents:
FDIS Report on voting
CIS/A/1316/FDIS CIS/A/1320/RVD

Full information on the voting for the approval of this amendment can be found in the report on
voting indicated in the above table.
The committee has decided that the contents of this amendment and the base publication will
remain unchanged until the stability date indicated on the IEC website 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.

_____________
3.2 Abbreviated terms
Add the following new abbreviated terms to the existing list:
DRH double ridged horn
XP cross polarization
PDF probability density function

4.5.5 Cross-polar response of antenna
Delete, in the first sentence of the existing last paragraph, the cross-reference to [21].

© IEC 2020
4.7 Special antenna arrangements – large-loop antenna system
Replace the first sentence of the third paragraph with the following new sentence:
The EUT shall be positioned in the centre of the LLAS on a non-conductive support table.

Replace the third sentence of the third paragraph with the following new sentence:
Guidelines for routing of EUT cables are given in C.3 and Figure C.6.

Add, after the existing third paragraph, the following new paragraph:
The LLAS may be placed in any environment. Placement inside a shielded room, SAC, FAR, or
weather-protected OATS is permitted. Placement in a shielded environment is recommended
to eliminate ambient signals allowing for better sensitivity to EUT emissions. A minimum
distance of 0,5 m between the LLAS and any metallic plane is recommended. The validation of
the LLAS shall be performed at the location where the LLAS measurements normally take place
to take into account the effect of the environment (see C.4).

Replace, in the NOTE, "Correction factors" with "Conversion factors".

C.3 Construction of a large-loop antenna (LLA)
Replace the existing third paragraph with the following paragraph:
The standard diameter of each LLA is defined as D = 2 m (i.e. the reference diameter). If
necessary, e.g. in the case of a large EUT, D may be increased. However, in the frequency
range up to 30 MHz, the maximum diameter allowed is 4 m. Further increase of the diameter
can result in non-reproducible resonances of the LLAS response at the high-frequency end of
the measuring range. The validation method specified in C.4 applies for LLAS loops with
diameters of 2 m, 3 m, or 4 m.

Replace the second sentence of the seventh paragraph "The insertion loss of the current probe
shall be sufficiently low (see NOTE 1)." with "The insertion impedance of the current probe
should be sufficiently low (see NOTE)."
Delete the existing NOTE 1 and NOTE 2.

– 4 – CISPR 16-1-4:2019/AMD1:2020
© IEC 2020
Add, between the seventh and eighth paragraphs, the following new NOTE:
NOTE To obtain a flat frequency response for each LLA at the lower end of the 9 kHz to 30 MHz frequency range,
the resistive part of the insertion impedance, R , of the current probe is designed to be much smaller than 2π f L at
c c
f = 9 kHz, where L represents the inductance of the current probe. In addition, R + R is to be less than or equal to
c c i
X /10 = (2π f L)/10 at 9 kHz, where R is the resistance of the inner conductor of the loop and L is the loop inductance.
i i
This inductance is about 1,5 µH/m along the circumference; thus, for each standard LLA whose diameter is 2 m,
X ≈ 0,5 Ω at f = 9 kHz.
i
Add, at the end of the existing text (before Figure C.1), the following new paragraph:
To avoid unwanted capacitive coupling between the EUT and the LLAS, the distance between
the EUT and components of the LLAS shall be at least 0,10 times the loop diameter. Particular
attention should be paid to the leads of an EUT. Cables shall be routed together and leave the
test volume in the same octant of the LLAS, no closer than 0,4 m to any of the LLAS loops (see
Figure C.6).
C.4 Validation of an LLA
Replace the existing title of this clause with the following new title:
C.4 Validation of the LLAS
Replace the first paragraph of this clause with the following three new paragraphs:
The validation of the LLAS shall be carried out by measuring the current induced in each of the
three LLAs by means of the LLAS verification dipole connected to a 50 Ω RF generator, as
described in C.5. The magnetic field emitted by the dipole allows verification of the magnetic
field sensitivity of the LLAS. The electric field emitted by the LLAS verification dipole is intended
to verify that the electric field sensitivity of the LLAS is sufficiently low.
The validation of an LLAS shall be performed at the site where the LLAS measurements
normally take place. This is to account for the effect of the floor, walls, and similar objects or
surfaces in the specific environment of the LLAS.
Validation measurements shall be performed at least at the following frequencies: 9 kHz,
100 kHz, 1 MHz, 2 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, 20 MHz, 25 MHz, and 30 MHz.

Replace the existing second and third paragraphs with the following new paragraphs:
The induced current shall be measured as a function of frequency in the range of 9 kHz to
30 MHz at the eight positions of the LLAS verification dipole shown in Figure C.7. During this
measurement, the LLAS verification dipole shall be in the plane of the LLA under test.
In each of the eight positions, the measured validation factor, expressed in dB(Ω) as
20 lg(V /I ), where V is the open circuit voltage of the RF generator and I is the measured
go I go I
current, shall not deviate by more than ±3 dB from the applicable reference validation factor
given in Figure C.8 and Table C.1.

© IEC 2020
Delete the existing fourth paragraph.

Add, before Figure C.7, three new paragraphs as follows:
The reference validation factors given in Figure C.8 and Table C.1 are valid for an LLAS with
circular loops having diameters of D = 2 m, 3 m, or 4 m.
Tabular values of the curves presented in Figure C.8 are given in Table C.1. These tabular
values shall be used for the LLAS validation.
Background material and the equations for calculating the reference validation factors are given
in CISPR TR 16-3:2020 [23].
Figure C.7 – The eight positions of the LLAS verification dipole during validation of an
LLA
Replace the existing figure with the following new figure:

Figure C.7 – The eight positions of the LLAS verification
dipole during validation of an LLA

– 6 – CISPR 16-1-4:2019/AMD1:2020
© IEC 2020
Figure C.8 – Validation factor for an LLA of 2 m diameter
Replace the existing figure, including its title, with the following new figure:

Figure C.8 – Reference validation factors for loops
of 2 m, 3 m, and 4 m diameters

© IEC 2020
Add, after the new Figure C.8, the following new table:
Table C.1 – Reference validation factors of Figure C.8 for
loops of 2 m, 3 m, and 4 m diameters
Reference validation factor Reference validation factor
Frequency Frequency
2 m LLAS 3 m LLAS 4 m LLAS 2 m LLAS 3 m LLAS 4 m LLAS
MHz dB(Ω) MHz dB(Ω)
0,009 72,52 81,07 86,64 7 79,57 87,87 93,13
0,01 72,52 81,07 86,64 8 80,47 88,71 93,88
0,02 72,52 81,07 86,64 9 81,30 89,45 94,54
0,03 72,52 81,07 86,64 10 82,04 90,12 95,11
0,04 72,52 81,07 86,64 11 82,72 90,71 95,62
0,05 72,52 81,07 86,64 12 83,34 91,24 96,07
0,06 72,52 81,07 86,65 13 83,90 91,72 96,47
0,07 72,52 81,07 86,65 14 84,42 92,15 96,84
0,08 72,52 81,07 86,65 15 84,90 92,54 97,18
0,09 72,52 81,07 86,65 16 85,34 92,89 97,50
0,1 72,52 81,07 86,65 17 85,75 93,22 97,80
0,2 72,54 81,08 86,66 18 86,13 93,53 98,10
0,3 72,55 81,10 86,68 19 86,48 93,82 98,39
0,4 72,58 81,13 86,70 20 86,81 94,09 98,67
0,5 72,61 81,16 86,73 21 87,12 94,35 98,94
0,6 72,65 81,20 86,77 22 87,41 94,60 99,21
0,7 72,70 81,24 86,82 23 87,68 94,85 99,47
0,8 72,75 81,30 86,87 24 87,94 95,09 99,72
0,9 72,81 81,36 86,93 25 88,19 95,32 99,96
1 72,88 81,42 86,99 26 88,43 95,56 100,18
2 73,81 82,33 87,88 27 88,66 95,79 100,38
3 75,01 83,51 89,02 28 88,88 96,02 100,57
4 76,26 84,72 90,19 29 89,09 96,25 100,73
5 77,46 85,88 91,28 30 89,30 96,47 100,88
6 78,56 86,93 92,26 - - - -
C.5 Construction of the LLAS verification dipole antenna
Replace the first paragraph with the following paragraph:
The LLAS verification dipole, shown in Figure C.9, has been designed to emit simultaneously a
magnetic field, which should be measured by the LLAS, and an electric field, which should be
rejected by the LLAS.
– 8 – CISPR 16-1-4:2019/AMD1:2020
© IEC 2020
Replace the existing second and third paragraphs with the following two paragraphs:
The LLAS verification dipole antenna shall be constructed in accordance with Figure C.9, using
RG-223/U or similar type of coaxial cable. It shall have a width W = 150 cm and a spacing
s = 10 cm (cable centre to cable centre distances), as depicted in Figure C.9. A slit in the outer
conductor of the coaxial cable shall separate the dipole into two halves. One half of the dipole
(the right-hand half in Figure C.9) shall be short-circuited near the connector as well as near
the slit opposite from the connector. Short-circuited means that the inner and outer conductors
of the coaxial cable shall be electrically bonded together. This half shall be connected to the
reference-ground of the coaxial connector (BNC or similar type). The inner conductor of the
coaxial cable, forming the left-hand half of the dipole in Figure C.9, shall be connected to the
centre-pin of the coaxial connector, and its outer conductor connected to the reference ground
of that coaxial connector.
A small metal box shall be used to screen the connections near the coaxial connector. The
outer conductor of the two halves of the dipole coaxial cable and the reference ground of the
coaxial connector shall be bonded to this box.

Replace, in the existing fourth paragraph, "is used" with "may be used".

Figure C.9 – Construction of the LLAS verification dipole antenna
Replace the existing figure with the following new figure, without modifying its title:
Dimensions in millimetres
NOTE Distances indicated are cable centre to cable centre distances.

© IEC 2020
C.6 Conversion factors
Replace the existing text this clause, including Figure C.10 and Figure C.11, by the following
new Clauses C.6 and C.7.
C.6 Conversion factors
C.6.1 General
This subclause deals with the factor that converts the current measured in an LLA with a non-
standard diameter to a current that would have been measured using an LLA with the standard
diameter of D = 2 m (see Figure C.10 and Table C.2). It also deals with the factor that converts
the current (I) induced in an LLA by an EUT into a magnetic field strength H at a specified
distance from the EUT (see Figure C.11 and Table C.3). Background material and the equations
for calculating these conversion factors are given in CISPR TR 16-3:2020 [23].
C.6.2 Current conversion factors for an LLAS with non-standard diameter
The difference S in decibels, between the current measured in an LLA with diameter D, in m,
D
and the current that would be measured using an LLA having the standard diameter D = 2 m,
expressed in logarithmic units (such as dB(µA)), is given in Figure C.10 (and Table C.2) for
several values of D, as determined using Equation (C.1):

S = I − I
(C.1)
D D m 2 m
where I and I are the values of the induced currents in an LLA with diameter D and the
D m 2 m
standard 2 m diameter LLA, respectively, both expressed in logarithmic units (such as dB(µA)).

Figure C.10 – Sensitivity S of an LLA with diameter D
D
relative to an LLA with 2 m diameter

– 10 – CISPR 16-1-4:2019/AMD1:2020
© IEC 2020
Table C.2 – Sensitivity S of an LLA with diameter D
D
relative to an LLA with 2 m diameter (Figure C.10)
LLAS diameter D LLAS diameter D
Frequency Frequency
1 m 1,5 m 3 m 4 m 1 m 1,5 m 3 m 4 m
MHz MHz
dB dB dB dB dB dB dB dB
0,009 12,88 5,34 -7,50 -12,80 7 12,72 5,24 -7,25 -12,24
0,01 12,88 5,34 -7,50 -12,80 8 12,67 5,22 -7,18 -12,08
0,02 12,88 5,34 -7,50 -12,80 9 12,62 5,19 -7,11 -11,92
0,03 12,88 5,34 -7,50 -12,80 10 12,56 5,16 -7,02 -11,75
0,04 12,88 5,34 -7,50 -12,80 11 12,50 5,12 -6,94 -11,58
0,05 12,88 5,34 -7,50 -12,80 12 12,43 5,08 -6,85 -11,41
0,06 12,88 5,34 -7,50 -12,80 13 12,36 5,04 -6,76 -11,25
0,07 12,88 5,34 -7,50 -12,80 14 12,29 5,00 -6,67 -11,09
0,08 12,88 5,34 -7,50 -12,80 15 12,21 4,96 -6,58 -10,96
0,09 12,88 5,34 -7,50 -12,80 16 12,12 4,91 -6,50 -10,84
0,1 12,88 5,34 -7,50 -12,80 17 12,04 4,87 -6,42 -10,73
0,2 12,88 5,33 -7,50 -12,80 18 11,95 4,82 -6,35 -10,65
0,3 12,88 5,33 -7,50 -12,80 19 11,86 4,77 -6,28 -10,58
0,4 12,88 5,33 -7,50 -12,80 20 11,77 4,73 -6,23 -10,53
0,5 12,88 5,33 -7,50 -12,80 21 11,68 4,68 -6,18 -10,50
0,6 12,88 5,33 -7,50 -12,80 22 11,60 4,64 -6,14 -10,48
0,7 12,88 5,33 -7,50 -12,80 23 11,51 4,60 -6,11 -10,46
0,8 12,88 5,33 -7,49 -12,80 24 11,42 4,55 -6,09 -10,45
0,9 12,88 5,33 -7,49 -12,79 25 11,33 4,52 -6,08 -10,44
1 12,87 5,33 -7,49 -12,79 26 11,25 4,48 -6,08 -10,43
2 12,86 5,33 -7,48 -12,75 27 11,17 4,45 -6,08 -10,40
3 12,85 5,32 -7,45 -12,69 28 11,09 4,41 -6,09 -10,37
4 12,83 5,30 -7,41 -12,61 29 11,02 4,39 -6,10 -10,32
5 12,80 5,29 -7,37 -12,50 30 10,95 4,36 -6,12 -10,25
6 12,76 5,27 -7,31 -12,38 - - - - -

C.6.3 Conversion of LLAS measured current to magnetic field strength
The conversion factor in Figure C.11 and Table C.3 represent the worst-case (highest) of all
three polarizations when considering a source of magnetic field positioned in the centre of an
LLA with its magnetic dipole moment perpendicular to the plane of that LLA, for all three loops
of an LLAS. As such, this conversion factor may be used to estimate the worst-case magnetic
field strength that would be measured with the loop antenna specified in 4.3, at a specific
measurement distance (3 m, 10 m, or 30 m) from the EUT periphery, with the loop antenna
centre at 1,3 m above the metallic ground plane of a test site, with the EUT’s lowest surface
positioned at 80 cm above the ground plane, and with the EUT rotated through all azimuth
angles, for all three loop antenna polarizations. This field strength estimation may be obtained
by adding the conversion factor of Figure C.11 and Table C.3 to the worst-case induced current
level measured from the EUT with the three loops of the LLAS, at the frequency of
measurement.
NOTE 1 Often, traditional magnetic field strength test methods (e.g. from CISPR 11 [24]) apply a loop antenna as
specified in 4.3 and positioned in a vertical plane only while the EUT is rotated only around its vertical axis. In that
case only the horizontal dipole moments, i.e. the dipole moments parallel to the ground plane, are measured.
Consequently, in case the EUT also generates vertical dipole moments, the LLAS conversion factor cannot be used
to compare the results of both measurement methods. However, the LLAS conversion factor can be used for
comparisons with the magnetic field strength measurement method results when the loop antenna of 4.3 is positioned
in a horizontal plane, in addition to the two vertical loop plane polarizations.

© IEC 2020
If the actual position of a disturbance source within an EUT is at a distance less than 0,5 m
from the centre of the standard LLAS, the measurement results differ by less than 3 dB from
those with that source in the centre of the LLAS.
The relation between the magnetic field strength H in dB(µA/m) measured at a distance d and
the LLA current I in dB(µA) is per Equation (C.2):

H= I+ C (C.2)
dA
-1
where C is the current-to-field conversion factor in dB(m ) for a certain distance d when
dA
expressing H in dB(µA/m) (see also NOTE 2).
In general, the conversion factor is frequency-dependent; Figure C.11 (and Table C.3) present
C for standard measurement distances of 3 m, 10 m, and 30 m.
dA
If the current is measured in an LLAS with a non-standard diameter D, Equation (C.2) can be
written as Equation (C.3):
(C.3)
H= I− S + C
D dA
–1
where H is expressed in dB(µA/m), I in dB(µA), S in dB, and C in dB(m ).
D dA
NOTE 2 For disturbance level calculations, CISPR uses the magnetic field strength H in dB(µA/m) instead of electric
field strength E in dB(µV/m). In this context, the relation between H and E is given by Equation (C.4):

E= H+ 51,5 (C.4)
where E is expressed in dB(µV/m) and H in dB(µA/m). The constant 51,5, in dB(Ω) in Equation (C.4), is explained in
the NOTE in 4.3.2.
Figure C.11 – Conversion factor C [for conversion into dB(μA/m)]
dA
for three standard measurement distances d

– 12 – CISPR 16-1-4:2019/AMD1:2020
© IEC 2020
Table C.3 – Magnetic field strength conversion factor C
dA
for three measurement distances (Figure C.11)
2 m LLAS to 2 m LLAS to 2 m LLAS to 2 m LLAS to 2 m LLAS to 2 m LLAS to
Frequency
Frequency
3 m field 10 m field 30 m field 3 m field 10 m field 30 m field
MHz
dB(1/m) dB(1/m) dB(1/m) (MHz) dB(1/m) dB(1/m) dB(1/m)
0,009 -19,77 -47,18 -75,09 7 -18,97 -42,23 -55,72
0,01 -19,77 -47,18 -75,09 8 -18,76 -41,45 -53,41
0,02 -19,77 -47,18 -75,09 9 -18,56 -40,74 -51,4
0,03 -19,77 -47,18 -75,09 10 -18,35 -40,08 -49,63
0,04 -19,77 -47,18 -75,09 11 -18,14 -39,24 -48,04
0,05 -19,77 -47,18 -75,08 12 -17,93 -37,72 -46,61
0,06 -19,77 -47,18 -75,08 13 -17,73 -36,36 -45,31
0,07 -19,77 -47,18 -75,08 14 -17,54 -35,11 -44,12
0,08 -19,77 -47,18 -75,08 15 -17,35 -33,97 -43,03
0,09 -19,77 -47,18 -75,08 16 -17,18 -32,92 -42,02
0,1 -19,77 -47,18 -75,07 17 -17,02 -31,95 -41,08
0,2 -19,77 -47,17 -75,02 18 -16,87 -31,05 -40,21
0,3 -19,77 -47,16 -74,94 19 -16,73 -30,22 -39,40
0,4 -19,77 -47,15 -74,82 20 -16,60 -29,44 -38,63
0,5 -19,76 -47,13 -74,68 21 -16,48 -28,71 -37,92
0,6 -19,76 -47,11 -74,51 22 -16,37 -28,02 -37,25
0,7 -19,76 -47,09 -74,32 23 -16,27 -27,37 -36,61
0,8 -19,76 -47,06 -74,11 24 -16,18 -26,76 -36,01
0,9 -19,75 -47,02 -73,88 25 -16,10 -26,18 -35,43
1 -19,75 -46,99 -73,64 26 -16,03 -25,62 -34,89
2 -19,69 -46,46 -70,97 27 -15,96 -25,10 -34,37
3 -19,60 -45,70 -68,52 28 -15,90 -24,59 -33,87
4 -19,48 -44,83 -65,70 29 -15,52 -24,11 -33,39
5 -19,33 -43,93 -61,65 30 -15,04 -23,64 -32,93
6 -19,15 -43,06 -58,41 - - - -

C.7 Examples
The following examples explain use of Equation (C.1), Equation (C.2), Equation (C.3),
Figure C.8, Figure C.10, and Figure C.11.
a) Given: measuring frequency f = 100 kHz, LLA diameter D = 2 m, current in LLA I = X dB(µA).
Then using Equation (C.1) and Figure C.10, it follows that:
–1
at d = 3 m: H = [X/dB(µA) + C /dB(m )] dB(µA/m) = (X − 19,5) dB(µA/m)
3A
at d = 3 m: E = [X/dB(µA) + C /dB(Ω/m)] dB(µV/m) = [X + (51,5 − 19,5)] dB(µV/m)
3V
b) Given: measuring frequency f = 100 kHz, LLA diameter D = 2 m, current in LLA I = X dB(µA).
Then, using Equation (C.2) and Figure C.11 (Table C.3), it follows that:
–1
at d = 3 m: H [dB(µA/m)] = X [dB(µA)] + C [dB(m )] = (X – 19,77) dB(µA/m)
3A
c) Given: measuring frequency f = 100 kHz, LLA diameter D = 4 m, current in LLA I = X dB(µA).
Then, using Equation (C.1) and Figure C.10 (Table C.2), it follows that the same EUT
would induce a current:
I [dB(µA)] = X [dB(µA)] – S [dB] = X – (–12,80) = (X + 12,80) dB(µA)
in an LLA with the standard diameter D = 2 m.

© IEC 2020
Add, after the existing Annex G, the following new Annex H:
Annex H
(informative)
Definition of uncertainty in cross-polar response measurement
H.1 General
Subclause 4.5.5 of this document describes the method of cross-polar response (XPR)
measurement for antennas with LPDA type design. This annex defines and discusses the
sources of uncertainty involved in the measurement and provides example uncertainty
estimates.
The uncertainty estimates in this annex are based on an LPDA (or hybrid) antenna that is placed
in a FAR, with elements oriented along the vertical axis (i.e. in VP), for frequencies above
100 MHz. It is anticipated that a FAR would be most suitable for this measurement; however,
the uncertainty analysis may be adapted for other facilities such as OATS or SAC. The
uncertainty estimate applies when using either a dipole antenna (below 1 GHz), or linearly-
polarized horn antenna (above 1 GHz) as the receive antenna (Rx antenna, denoted by ‘R’).
For best results, the frequency should be swept from 30 % to 150 % of the dipole’s tuned
frequency. The analysis uses linear ratio terms because the final uncertainty will always be
asymmetric for low cross-polar signals.
The AUT (transmit antenna, denoted by ‘T’) generates a primary (vertically polarized) field (E ),
x
and a secondary cross-polar (horizontally polarized) field (E ). Here E is the field strength,
y ISO
which would be generated by a perfect linearly-polarized source with unity gain of an isotropic
radiator, in accordance with Equation (H.1) and Equation (H.2).

η P
0 T
E = G × = G × E (H.1)
x T T
ISO
4πd
G
T
E = × E
(H.2)
y
ISO
A
xpT
where
G is the transmit antenna (AUT) gain;
T
η is the impedance of free space;
P is the transmit power;
T
d is the distance between the antennas.
NOTE 1 The XPR measurement in 4.5.5 arbitrarily describes the AUT as Rx antenna in VP. For passive antennas,
the use of the AUT as Tx antenna does not change the principles of uncertainty analysis. The terms co-polar and
cross-polar in this annex consequently refer to VP and HP respectively. The AUT could also be used in HP, which
then would mean that co-polar and cross-polar would refer to HP and VP. Here VP relates to the chamber (e.g. FAR)
x-axis and HP relates to the chamber y-axis.
Ideally E and E are only determined by the properties of the AUT. However, there are sources
x y
of uncertainty caused by imperfections of the receive antenna and the test site (e.g. FAR). The
XPR (A ) of each antenna is defined by the associated field-strength ratio (see Equation (H.3)
xp
for the AUT, transmit antenna):

– 14 – CISPR 16-1-4:2019/AMD1:2020
© IEC 2020
E
x
A =
xpT (H.3)
E
y
Φ = A ×Φ
(H.4)
aCx xpR aCo
where Φ and Φ of Equation (H.4) are linear AFs (F = 20lgΦ and F = 20lgΦ
aCo aCx aCo aCo aCx aCx
are AFs in dB) of the non-ideal receive antenna (A relates to the calibrated receive AF and
xpR
is also a linear ratio).
NOTE 2 Assuming that only one field strength component E exists, then the co-polarized receive antenna output
x
voltage consists of two components V = E /Φ and V = E /Φ .
Co x aCo Cx x aCx
An error matrix for the anechoic chamber is defined to show how the true electric field strengths
relate to the ideal AUT field strength. The matrix terms are described as errors, which in
principle are deterministic values related to standing waves and cross-polar scattering in the
chamber at each frequency. In this analysis they are processed as broadband statistical
uncertainty contributions, because measurements of these matrix terms have uncertainties, and
they are both frequency-dependent and location-dependent within the chamber.

 
δ
E 1+δ 
  
xy
x xx
  (H.5)
= × G × E

   T ISO
E δ
1+δ  
 y  yx
yy A
  

xpT
 
The chamber error terms describe reflections, which add uncertainty either in the same
polarization as the original AUT field strengths (i.e. δ and δ ), or in the other polarization (i.e.
xx yy
δ and δ ). This analysis considers field components such that even a pure linearly-polarized
xy yx
electric field source will generate a small component along the cross-polar axis.
The chamber error terms are:
δ for VP wall reflections resulting from the true co-polar field strength, contributing to E ;
xx x
δ for VP wall reflections resulting from the true cross-polar field strength, contributing to E ;
xy x
δ for HP wall reflections resulting from the true cross-polar field strength, contributing to E ;
yy y
δ for HP wall reflections resulting from the true co-polar field strength, contributing to E .
yx y
Equation (H.6) and Equation (H.7) define the true field strength produced at the position of the
Rx antenna. This field strength is measured in two polarizations by rotating the Rx antenna.
From the electric field-strength expression of Equation (H.5) the AUT field strength is derived:

E ≈ G × E (1+δ ) (H.6)
x T ISO xx
 
1+δ
yy
 
E = G × E δ +
(H.7)
y T ISO yx
 
A
xpT
 
In Equation (H.6) the second-order term (δ × G × E /A ) is dropped because it is
xy T ISO xpT
negligibly small. The voltage V is the receive antenna output voltage when it is co-polarized.
Co
is the receive antenna output voltage, when it is rotated from co-polar
Similarly, the voltage V
Cx
to cross-polar (VP to HP). It is clear from Equation (H.6) and Equation (H.7) that the measured
XPR will depend on the magnitude of the cross-polar terms, per Equation (H.8).

© IEC 2020
 1 1 
   1 1 
E  E 
V  Φ Φ
x 1 x
Co  aCo aCx
 
A
= =
1 xpR (H.8)
   
 
 
 
E E
V 1 1 Φ
 y  y
 Cx aCo
   
A
 
 xpR   1 
Φ Φ
 
aCx aCo
 
The received voltage is derived assuming the chamber error terms are uncorrelated, and
second order terms are removed if the typical value of the divisor is large [i.e. A will be > 20
xpR
(dimensionless)], per Equation (H.9) and Equation (H.10):

G × E
E
x T ISO
V ≈ = (1+δ ) (H.9)
Co xx
Φ Φ
aCo aCo
 

GE× A
xpT
T ISO
  
VA× 11±δδ±×+ ×±δ
 ( ) (H.10)
Cx yy xpT yx xx

 
A ×Φ A
xpT aCo xpR

 
The chamber delta terms (δ etc.) will appear as frequency dependent oscillations about 0 dB.
xx
Over a broad range they may be considered as random contributions with symmetric PDF for
this analysis. The term A /A , relates to the increase in measured V due to the
xpT xpR Cx
polarization mismatch between the transmit antenna and the receive antenna. This term has an
asymmetric PDF, however for the purposes of limit testing the relevant side of the PDF is finite
and the worst case increase in V is used, which is indicated by the sign. This reduces the
Cx
measured ratio A , and for simplicity this is represented as a systematic term in the
xpT
uncertainty budget.
The XPR including its uncertainty is then calculated using the voltages from Equation (H.9) and
Equation (H.10), per Equation (H.11) and Equation (H.12):

V
Co
A = (H.11)
xpT meas
V
Cx

V
Co
(H.12)
a = 20lg in dB

xpT meas
V
Cx
Rationale H5) in H.3 contains remarks about the terms in Equation (H.9) and Equation (H.10),
and the chamber error matrix.
H.2 Example uncertainty estimate
The example shown in Table H.1 pertains to measuring a true XPR of 22 dB (12,6 linear ratio),
with a dipole antenna that would have an XPR similar to a double-ridged horn (DRH) antenna.
Because measurement of XPR depends on chamber performance, it is crucial to average
several measurements in different locations, especially in a chamber with poor performance.
Three measurements are assumed in this example, and hence for a Type A contribution the
uncertainty of the mean value is obtained by the standard deviation divided by .
The chamber reflection terms are associated with the error terms in Equation (H.9) and Equation
(H.10). The assumed values for chamber and receive antenna uncertainty are given in Table
H.1, with an extra factor of 0,5 given to the cross-polar term (0,5 is an estimate subject to
reduction upon further investigation). The uncertainty arising from the chamber errors may be
estimated from chamber evaluation measurements.
=
– 16 – CISPR 16-1-4:2019/AMD1:2020
© IEC 2020
Table H.1 – Example uncertainty estimate for XPR measurement
in a FAR and assumed a = 22 dB, a = 34 dB
xpT xpR
a
Uncertainty in X u(x ) Sensitivity c u(x )
Input quantity
i i i i
c
X
i
i
Average of 3
for A
dB linear PDF linear
xpT
measurements
H1)
0,08 0,009 3 normal, k = 1 0,009 3 0,577 0,005 3
VNA reading, co-polar
H1)
0,08 0,009 3 normal, k = 1 0,009 3 0,577 0,005 3
VNA reading, non-linearity cross-polar
H2)
0,035 0 rectangular 0,020 2 0,577 0,011 7
Antenna misalignment (2°)
H3)
0,005 0 rectangular 0,002 9 0,577 0,001 7
Distance uncertainty (1 cm)
H4)
0,1 0,011 6 rectangular 0,006 7 1 0,006 7
AUT depolarization due to environment
H4)
0,1 0,011 6 rectangular 0,006 7 1 0,006 7
Rx ant. depolarization due to environment
H5)
0,056 0 triangular 0,022 9 0,577 0,013 2
Chamber reflection, δ = 0,056
xx
H5)
0,251 5 rectangular 0,145 2 1 0,145 2
A /A
xpT xpR
δ 0,056 0 triangular 0,022 9 0,577 0,013 2
yy
(A /A ) × δ 0,014 1 triangular 0,005 7 0,577 0,003 3
xpT xpR xx
A × δ (with factor 0,5) 0,352 8 triangular 0,144 0 0,577 0,083 2
xpT yx
Combined standard uncertainty u   k = 1 0,169 2
c
H6)
k = 1,64 0,277 6
Expanded uncertainty ku
c
Expanded uncertainty in dB  20lg(1/[1+ku ]) k = 1,64
−2,13
c
a H1)
Footnote references, e.g. , refer to rationale details listed in H.3.

H.3 Rationale for the estimates of input quantities in Table H.1 and Table H.3
H1) The reading uncertainty of a VNA has been assumed to be 0,08 dB, based on Type A
repeatability testing. This value also contains the uncertainty due to the VNA nonlinearity,
which affects the difference between the two readings.
H2) If θ is the angle of misalignment, then δE ∝ sin θ ≈ θ × (π/180), where θ is measured in
degrees.
H3) δE ∝ δd/d evaluated for δd = 1 cm uncertainty over d = 200 cm range, when the AUT is
rotated.
H4) The closeness of the chamber walls can influence the polarization purity of the AUT and
Rx antenna. ‘Depolarization’ means (partial) change of polarization, e.g. by reflection
effects or similar.
H5) The delta terms in the chamber error matrix can be equal in worst-case conditions, which
implies the distribution of electric field strength uncertainty is equal in both polarizations,
even if the source is linearly polarized. This is unlikely to be true for a higher performance
δ and δ terms can be reduced (a value of half is
chamber with good absorbers, so the
yx xy
assumed). In the uncertainty estimate, a PDF factor of (triangular) is assumed for
chamber uncertainties based on an initial estimate that chamber reflections are more
likely to be around zero (see the text following Equation (H.9) and Equation (H.10) in H.1).
The error terms in Equation (H.9) and Equation (H.10) show how the real electric field
strengths couple into the measured XPR. It is worth understanding what the dominant
terms in Table H.1 and Table H.3 relate to. The term A /A relates to the fundamental
xpT xpR
limit of the measurement, i.e. the XPR of the receive antenna, as a ratio of the XPR level
being measured, and this is not improved by averaging several measurements because

© IEC 2020
it is a systematic uncertainty. The term A × δ relates to the cross-polar error of the
xpT yx
chamber, which will make a co-polar field appear as cross-polar. In a good chamber, it is
assumed that this is half the co-polar error, and it is likely that this will be even less for
directive antennas.
So far, all chamber performance data in this uncertainty estimate are based on
assumptions. No specific test method or site validation method has yet been developed.
The direct errors δ and δ may be derived from NSA or S measurement results. The
xx yy vswr
cross-polar terms δ and δ may then be estimated. After further experience is gained,
yx xy
this annex might be revised. Note the importance of using at least three averages taken
at different locations in the FAR, which reduces the Type A terms and allows the chamber
reflections to be considered more as random components, applied to each data point,
rather than systematic with precise locations. A single measurement is applied at an
OATS. Generally, an OATS is considered better than a FAR with good absorber material,
and a large FAR is considered better than a small FAR.
H6) Because the requirement in 4.5.5 is A > 20 dB, it is possible to show that this is fulfilled
xp
with a level of confidence of 95 % if the condition A /(1 + 1,64u ) > 10 (or 20 dB)
xpT meas c
applies. The coverage factor of k = 1,64 (rather than k = 2) applies for a one-sided
probability distribution (the value k = 2 is a widely accepted approximation for the exact
two-sided value k = 1,96).
NOTE The measured ratio in Equation (H.11) shows that the outcome is more sensitive to uncertainty in the
denominator, which will be a smaller voltage. When V is reduced by measurement uncertainty, the final
Cx
ratio is then very large, but this is not important. For limit testing against a minimum A requirement, the
xpT
largest positive uncertainty in V is taken such that the final ratio is reduced. Thus, as a reasonable
Cx
approximation the worst-case uncertainty scales (1/[1+ku ]), and this value will change with different A .
c xpT meas
of 12,6 was assumed in Table H.1, giving A = 12,6/(1+0,277 6) = 9,86, which is equivalent
An A
xpT meas xpT95 %
to (22 dB − 2,13 dB).
The analysis demonstrates that the largest influence factor is the relationship A /A ,
xpT xpR
and that a good chamber is preferred for accurate XPR measurement. Table H.2 gives an
example of how the uncertainty changes with AUT XPR value, for fixed receive antenna
properties. Using the values in the worked example, the interpretation is that a measured
XPR of 22 dB indicates a 95 % probability that the true value is greater than 19,87.
= 40 dB) and an improved chamber (δ = δ = 0,028
For a better receive antenna (a
xpR xx yy
and δ = 0,014), the effective limit value is improved. The improved uncertainty will be
yx
20lg(1/[1+1,64u ]) = −1,16 dB, and thus a measured XPR of 22 dB indicates a 95 %
c
probability that the true value is greater than 20,84 dB.
Table H.2 – Uncertainties depending on other values of A
xpT
(other assumptions as in Table H.1)
A
a /dB 20lg(1/[1+1,64u ])/dB
xpT
xpT c
10 3,2 −0,68
13 4,5 −0,88
16 6,3 −1,16
18 7,9 −1,42
20 10,0 −1,74
22 12,6 −2,13
24 15,8 −2,59
– 18 – CISPR 16-1-4:2019/AMD1:2020
© IEC 2020
H.4 Measurement of XPR below 100 MHz at an OATS
Where anechoic chambers do not perform well below 100 MHz, XPR may be measured at an
OATS with the antennas at a large height above the ground plane. In this case it is assumed
that the δ and δ error terms are negligible. Table H.3 shows this for a measurement at 6 m
yx xy
height and 3 m distance as an example.
Table H.3 – Example uncertainty estimate for XPR measurement
at an OATS and assumed a = 22 dB, a = 34 dB
xpT xpR
a
Uncertainty in X u(x ) Sensitivity c u(x )
Input quantity
i i i i
c
X
i
i
dB δ linear PDF linear 1 for A
xpT
measurement
H1)
0,08 0,009 3 normal, k = 1 0,009 3 1 0,009 3
VNA reading, co-polar
H1)
0,08 0,009 3 normal, k = 1 0,009 3 1 0,009 3
VNA reading, non-linearity cross-polar
H2)
0,035 0 rectangular 0,020 2 1 0,020 2
Antenna misalignment (2°)
Distance uncertainty (2 cm over 3 m 0,007 0 rectangular 0,004 0 1 0,004 0
H3)
range)
H4)
0,1 0,011 6 rectangular 0,006 7 1 0,006 7
AUT depolarization due to environment

Rx ant. depolarization due to environment 0,1 0,011 6 rectangular 0,006 7 1 0,006 7
H4)
H5)
0,034 0 triangular 0,013 9 1 0,013 9
Antenna mast reflection, δ = 0,034
xx
H5)
0,251 5 rectangular 0,145 2 1 0,145 2
A /A
xpT xpR
Δ 0,034 0 triangular 0,013 9 1 0,013 9
yy
0,008 6 triangular 0,003 5 1 0,003 5
(A /A ) × δ
xpT xpR xx
Combined standard uncertainty u   k = 1 0,148 9
c
H6)
k = 1,64 0,244 2
Expanded uncertainty ku
c
Expanded uncertainty in dB  20lg(1/[1+ku ]) k = 1,64 −1,90
c
a H1)
Footnote references, e.g. , refer to rationale details listed in H.3.

Bibliography
Replace the existing reference [21] with the following:
[21] Void
Add the following new references to the existing list:
[23] CISPR TR 16-3:2020, Specification fo
...