IEC 62153-4-15:2021

IEC 62153-4-15 ®
Edition 2.0 2021-08
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Metallic communication cables and other passive components test methods –
Part 4-15: Electromagnetic compatibility (EMC) – Test method for measuring
transfer impedance and screening attenuation – or coupling attenuation with
triaxial cell
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IEC 62153-4-15 ®
Edition 2.0 2021-08
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Metallic communication cables and other passive components test methods –
Part 4-15: Electromagnetic compatibility (EMC) – Test method for measuring
transfer impedance and screening attenuation – or coupling attenuation with
triaxial cell
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.100.10; 33.120.10 ISBN 978-2-8322-5214-7
– 2 – IEC 62153-4-15:2021 RLV © IEC 2021
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references. 7
3 Terms and definitions . 8
4 Physical background . 10
5 Principle of the test methods . 10
5.1 General . 10
5.2 Transfer impedance . 12
5.3 Screening attenuation . 13
5.4 Coupling attenuation . 13
5.5 Tube-in-tube method . 13
6 Test procedures . 14
6.1 General . 14
6.2 Triaxial cell . 14
6.3 Cut-off frequencies, higher-order modes . 14
6.4 Test equipment . 14
6.5 Calibration procedure . 16
6.6 Test leads and connecting cables to the DUT . 17
7 Sample preparation . 17
7.1 Coaxial connector or assembly or quasi-coaxial component . 17
7.2 Balanced or multipin connectors or components . 17
7.3 Cable assemblies . 19
7.4 Other screened devices . 19
8 Transfer impedance (short-matched) . 20
8.1 General . 20
8.2 Principle block diagram of transfer impedance . 20
8.3 Measuring procedure . 20
8.4 Evaluation of test results . 21
8.5 Test report . 21
9 Screening attenuation . 21
9.1 General . 21
9.2 Impedance matching . 21
9.3 Measuring with matched conditions . 22
9.3.1 Procedure . 22
9.3.2 Evaluation of test results . 22
9.4 Measuring with mismatch . 23
9.4.1 General . 23
9.4.2 Evaluaton of test results . 23
9.5 Test report . 24
10 Coupling attenuation . 24
10.1 General . 24
10.2 Procedure . 24
10.2.1 Coupling attenuation with balun . 24
10.2.2 Balunless coupling attenuation . 25
10.3 Expression of results . 25

10.4 Test report . 25
11 Coupling transfer function .
Annex A (informative) Principle of the triaxial test procedure . 28
A.1 General . 28
A.2 Transfer impedance . 29
A.3 Screening attenuation . 29
A.4 Coupling attenuation . 30
Annex B (informative) Triaxial cell . 33
Annex C (informative) Cut off frequencies, higher order modes .
Annex D (informative) Coupling transfer function .
Annex E (informative) Attenuation versus scattering parameter S .
Annex C (normative) Triaxial absorber cell . 42
C.1 Cut-off frequencies, higher order modes . 42
C.2 Absorber . 43
C.3 Influence of absorber . 45
Annex D (informative) Application of a moveable shorting plane. 46
D.1 Coupling transfer function . 46
D.2 Effect of the measurement length on the measurement cut-off frequency . 47
D.3 Details of the movable shorting plane . 47
D.4 Measurement results . 49
Annex E (informative) Correction in the case that the receiver input impedance R is
higher than the characteristic impedance of the outer circuit Z . 52
E.1 Impedance Z lower than the input impedance of the receiver . 52
E.2 Correction . 54
Annex F (informative) Test adapter . 55
Annex G (informative) Attenuation versus scattering parameter S . 56
Bibliography . 58

Figure 1 – Definition of Z . 8
T
Figure 2 – Principle depiction of the triaxial cell test setup (tube) to measure transfer
impedance and screening attenuation with tube in tube in accordance with IEC 62153-4-7 . 11
Figure 3 – Principle depiction of the triaxial cell to measure transfer impedance and
screening attenuation of connectors or assemblies with tube in tube in accordance with
IEC 62153-4-7 . 12
Figure 4 – Rectangular waveguide . 15
Figure 5 – Preparation of balanced or multipin connectors for transfer impedance and
screening attenuation. 18
Figure 6 – Preparation of balanced or multipin connectors for coupling attenuation
measurement . 19
Figure 7 – Test setup (principle) for transfer impedance measurement in accordance
with test method B of IEC 62153-4-3 . 20
Figure 8 – Principle test setup for balunless coupling attenuation measurement
according to IEC 62153-4-9 . 25
Figure A.1 – Principle test setup to measure transfer impedance and screening
attenuation . 28
Figure A.2 – Equivalent circuit of the principle of the test setup in Figure A.1 . 29
Figure A.3 – Coupling attenuation, principle of test setup with balun and standard tube . 31

– 4 – IEC 62153-4-15:2021 RLV © IEC 2021
Figure A.4 – Coupling attenuation, principle of setup with multiport VNA and standard
head . 31
Figure B.1 – Principle depiction of the triaxial cell to measure transfer impedance and
screening attenuation at HV-assemblies on a connector with tube-in-tube according to
IEC 62153-4-7 . 33
Figure B.2 – Examples of different designs of triaxial cells . 34
Figure C.1 – Comparison of the measurements with tube and with triaxial cell of a RG
11 cable with single braid construction, linear scale .
Figure C.2 – Comparison of the measurements with tube and with triaxial cell of a
cable RG 11 with single braid construction, log scale .
Figure D.1 – Measured coupling transfer function of a braided screen vs. frequency
with the triaxial cell .
Figure E.1 – Measurement with HP8753D of S21 of a 3dB attenuator .
Figure E.2 – Measurement with ZVRE of S of a 3dB attenuator .
Figure C.1 – Cavity or rectangular waveguide . 42
Figure C.2 – Comparison of the measurements of a RG 214 cable with 40 mm tube
and triaxial cells . 43
Figure C.3 – Principle of the triaxial cell with tube in tube and ferrite tiles as absorber . 43
Figure C.4 – Comparison of the measurements of an RG 214 with 40 mm tube and

triaxial cells with magnetic absorber . 44
Figure C.5 – Examples of magnetic flat absorber . 44
Figure C.6 – Setup for correction measurement . 45
Figure C.7 – Correction measurement . 45
Figure D.1 – Measured coupling transfer function of a braided screen versus frequency
with the triaxial cell . 46
Figure D.2 – Cross-section of triaxial cell with movable shorting plane . 48
Figure D.3 – Crosscut of plane shortening housing and tube-in-tube . 48
Figure D.4 – Detail H of Figure D.3: contact between plane and housing . 49
Figure D.5 – Detail G of Figure D.3: contact between plane and tube-in-tube . 49
Figure D.6 – Compilation of transfer impedance test results with different shorting
plane distances . 50
Figure E.1 – Example of forward transfer scattering parameter S for different
impedances in the outer circuit where the receiver input impedance is 50 Ω . 53
Figure E.2 – DUT with uniform cylindrical shape in the centre of the cell . 54
Figure F.1 – Principle of the test setup to measure transfer impedance and screening
or coupling attenuation of connectors . 55
Figure F.2 – Principle of the test setup to measure transfer impedance and screening
attenuation on a cable assembly . 55
Figure G.1 – Measurement with HP8753D of S of a 3 dB attenuator . 56
Figure G.2 – Measurement with ZVRE of S of a 3 dB attenuator . 57
Table 1 – IEC 62153-4 series, Metallic communication cable test methods – Test
procedures with triaxial test setup . 10
Table C.1 – Resonance frequencies of different triaxial cells .

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
METALLIC COMMUNICATION CABLES AND OTHER PASSIVE
COMPONENTS TEST METHODS –
Part 4-15: Electromagnetic compatibility (EMC) – Test method for
measuring transfer impedance and screening attenuation –
or coupling attenuation with triaxial cell

FOREWORD
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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.
This redline version of the official IEC Standard allows the user to identify the changes made to
the previous edition IEC 62153-4-15:2015. A vertical bar appears in the margin wherever a change
has been made. Additions are in green text, deletions are in strikethrough red text.

– 6 – IEC 62153-4-15:2021 RLV © IEC 2021
International Standard IEC 62153-4-15 has been prepared by IEC technical committee 46:
Cables, wires, waveguides, R.F. connectors, R.F. and microwave passive components and
accessories.
This second edition cancels and replaces the first edition published in 2015. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) measurement of coupling attenuation of balanced connectors, assemblies and components
with balun and balunless added;
b) application of a test adapter was added;
c) application of a moveable shorting plane;
d) application of the triaxial "absorber" cell;
e) correction of test results in the case that the receiver input impedance R is higher than the
characteristic impedance of the outer circuit Z .
The text of this International Standard is based on the following documents:
FDIS Report on voting
46/814/FDIS 46/822/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
A list of all the parts in the IEC 62153-4 series, published under the general title Metallic
communication cable test methods – Electromagnetic compatibility (EMC), can be found on the
IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document 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.

METALLIC COMMUNICATION CABLES AND OTHER PASSIVE
COMPONENTS TEST METHODS –
Part 4-15: Electromagnetic compatibility (EMC) – Test method for
measuring transfer impedance and screening attenuation –
or coupling attenuation with triaxial cell

1 Scope
This part of IEC 62153 specifies the procedures for measuring with triaxial cell the transfer
impedance, screening attenuation or the coupling attenuation of connectors, cable assemblies
and components, for example accessories for analogue and digital transmission systems, and
equipment for communication networks and cabling (in accordance with the scope of IEC
technical committee 46).
Measurements can be achieved by applying the device under test directly to the triaxial cell or
with the tube-in-tube method in accordance with IEC 62153-4-7.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 61196-1, Coaxial communication cables – Part 1: Generic specification – General,
definitions and requirements
IEC TS 62153-4-1:20132014, Metallic communication cable test methods – Part 4-1:
Electromagnetic Compatibility (EMC) − Introduction to electromagnetic screening
measurements
IEC 62153-4-3, Metallic communication cable test methods – Part 4-3: Electromagnetic
compatibility (EMC) − Surface transfer impedance − Triaxial method
IEC 62153-4-4:2015, Metallic communication cable test methods – Part 4-4: Electromagnetic
compatibility (EMC) – Shielded screening attenuation, Test method for measuring of the
screening attenuation a up to and above 3 GHz, triaxial method
S
IEC 62153-4-7, Metallic communication cable test methods – Part 4-7: Electromagnetic
compatibility (EMC) – Test method for measuring the transfer impedance ZT and the screening
attenuation a or coupling attenuation a of connectors and assemblies up to and above 3 GHz
s c
– Triaxial Tube in tube method
IEC 62153-4-8, Metallic communication cables and other passive components – Test methods
– Part 4-8: Electromagnetic compatibility (EMC) – Capacitive coupling admittance
IEC 62153-4-9:20092018, Metallic communication cable test methods – Part 4-9:
Electromagnetic compatibility (EMC) – Coupling attenuation of screened balanced cables,
triaxial method
– 8 – IEC 62153-4-15:2021 RLV © IEC 2021
IEC 62153-4-10, Metallic communication cable test methods – Part 4-10: Electromagnetic
compatibility (EMC) – Shielded screening attenuation test method for measuring the screening
effectiveness Transfer impedance and screening attenuation of feed-throughs and
electromagnetic gaskets – Double coaxial test method
IEC TS 62153-4-16, Metallic communication cable test methods – Part 4-16: Electromagnetic
compatibility (EMC) – Extension of the frequency range to higher frequencies for transfer
impedance and to lower frequencies for screening attenuation measurements using the triaxial
set-up
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61196-1 and the
following apply.
3.1
triaxial cell
rectangular housing in analogy to the principles of the triaxial test procedure, consisting of a
non-ferromagnetic metallic material
Note 1 to entry: The triaxial test procedure is described in IEC 62153-4-3 and IEC 62153-4-4.
3.2
surface transfer impedance
Z
T
for an electrically short screen, quotient of the longitudinal voltage U induced to the inner
circuit by the current I fed into the outer circuit or vice versa [Ω] (see Figure 1)
Note 1 to entry: The value Z of an electrically short screen is expressed in ohms [Ω] or decibels in relation to 1 Ω.
T
Figure 1 – Definition of Z
T
U
Z =
T (1)
I
 Z 
T
 
Z dB(Ω)= 20⋅lg (2)
T
 
1Ω
 
3.3
effective transfer impedance
Z
TE
impedance defined as:
Z = max Z ± Z
TE F T
(3)
where Z is the capacitive coupling impedance
F
3.4
screening attenuation
a
s
for electrically long devices, i.e. above the cut-off frequency, logarithmic ratio of the feeding
power P and the periodic maximum values of the coupled power P in the outer circuit
1 r,max
 
P
a 10⋅lgEnv  (4)
s
 
P
r,max
 
where
Env is the minimum envelope curve of the measured values in dB
Note 1 to entry: The screening attenuation of an electrically short device is defined as:
150Ω
a 20⋅lg
(5)
s
Z
TE
where
150 Ω is the standardised impedance of the outer circuit.
3.5
coupling attenuation
a
c
for a screened balanced device, sum of the unbalance attenuation a of the symmetric pair and
u
the screening attenuation a of the screen of the device under test
s
Note 1 to entry: For electrically long devices, i.e. above the cut-off frequency, the coupling attenuation a is defined
c
as the logarithmic ratio of the feeding power P and the periodic maximum values of the coupled power P in the
1 r,max
outer circuit.
3.6
coupling length
length of cable that is inside the test jig, i.e. the length of the screen under test
Note 1 to entry: The coupling length is electrically short, if
λ c
o
o
>⋅10 ε
or f < (6)
r1
L
10⋅⋅L ε
r1
or electrically long, if <
c
λ
o
o
f >
≤⋅2 εε− or  (7)
r1 r2
L
2⋅⋅L εε−
r1 r2
where
L is the effective coupling length, in m;
λ is the free space wavelength, in m;
ε is the resulting relative permittivity of the dielectric of the cable;
r1
ε is the resulting relative permittivity of the dielectric of the secondary circuit;
r2
=
=
– 10 – IEC 62153-4-15:2021 RLV © IEC 2021
f is the frequency, in Hz;
c is the velocity of light in free space, in m/s.
3.7
device under test
DUT
connector with mating connector and attached connecting cables or cable assembly consisting
of the assembly with their attached mated connectors and with connecting cables
4 Physical background
See IEC TS 62153-4-1, IEC 62153-4-3, IEC 62153-4-4, and Annex A to Annex F.
5 Principle of the test methods
5.1 General
The IEC 62153-4 series describes different test procedures to measure screening effectiveness
on communication cables, connectors and components.
Table 1 gives an overview of the test procedures of the IEC 62153-4 series carried out with the
triaxial test setup.
Table 1 – IEC 62153-4 series, Metallic communication cable test methods –
Test procedures with triaxial test setup
IEC 62153-4 series Metallic communication cable test methods – Electromagnetic compatibility
(EMC)
IEC TS 62153-4-1 Introduction to electromagnetic screening measurements
IEC 62153-4-3 Surface transfer impedance – Triaxial method
IEC 62153-4-4 Shielded screening attenuation, test method for measuring of the screening attenuation
a up to and above 3 GHz
S
IEC 62153-4-7 Shielded screening attenuation test method for measuring the Transfer impedance Z
T
and the screening attenuation a or the coupling attenuation a of RF-connectors and
S C
assemblies up to and above 3 GHz, tube in tube method
IEC 62153-4-9 Coupling attenuation of screened balanced cables, triaxial method
IEC 62153-4-10 Shielded screening attenuation test method for measuring the screening effectiveness
of feedtroughs and electromagnetic gaskets double coaxial method
IEC 62153-4-15 Test method for measuring transfer impedance and screening attenuation – or coupling
attenuation with triaxial cell
IEC TS 62153-4-16 Extension of the frequency range to higher frequencies for transfer impedance and to
lower frequencies for screening attenuation measurements using the triaxial setup

Larger connectors, cable assemblies, and components do not fit into the commercially available
test rigs (tubes) of the triaxial test procedures of IEC 62153-4-x series according to Table 1
IEC 62153-4-3, IEC 62153-4-4, and IEC 62153-4-7, respectively, which were designed
originally to measure transfer impedance and screening attenuation on communication cables,
connectors, and assemblies.
Since rectangular housings with RF-tight caps are easier to manufacture than tubes, the "triaxial
cell" was designed to test larger components devices, such as connectors, assemblies and
components. The principles of the triaxial test procedures in accordance with IEC 62153-4-x
series IEC 62153-4-3, IEC 62153-4-4 and IEC 62153-4-7 can be transferred to rectangular
housings. Tubes and rectangular housings can may be operated in combination in one test
setup (see Figure 2 and Figure 3).

DUT
Generator
Receiver
Test head with
screening cap
Connecting cable
Housing resp. triaxial cell
IEC
Figure 2 – Principle depiction of the triaxial cell test setup (tube) to measure transfer
impedance and screening attenuation with tube in tube in accordance with IEC 62153-4-7
In principle, the triaxial cell can be used in accordance with all triaxial procedures of Table 1,
where originally a cylindrical tube is used. The screening effectiveness of connectors,
assemblies or other components can be measured, in principle, in the tube as well as in the
triaxial cell. Test results of measurements with tubes and with triaxial cells correspond well.

– 12 – IEC 62153-4-15:2021 RLV © IEC 2021
Generator
DUT
Receiver
Tube in tube
Connecting cable
Test head with
screening cap
Housing resp. triaxial cell
IEC
Figure 3 – Principle depiction of the triaxial cell to measure transfer
impedance and screening attenuation of connectors or assemblies
with tube in tube in accordance with IEC 62153-4-7
The triaxial cell test setup is based on the triaxial system in accordance with IEC 62153-4-3
and IEC 62153-4-4, consisting of the DUT, a solid metallic housing and an RF-tight extension
tube (optional). The matched device under test (DUT), which is fed by a generator via a
connecting cable, forms the disturbing circuit, which may also be designated as the inner or the
primary circuit.
The disturbed circuit, which may also be designated as the outer or the second circuit, is formed
by the outer conductor of the device under test, connected to the connecting cable (or the tube
in tube, if applicable) and a solid metallic housing or cell having the DUT in its axis.
5.2 Transfer impedance
The test determines the screening effectiveness of a shielded device by applying a well-defined
current and voltage to the screen of the cable, the assembly or the device under test and
measuring the induced voltage in the secondary circuit in order to determine the surface transfer
impedance. This test measures only the galvanic and magnetic components of the transfer
impedance. To measure the electrostatic component (the capacitance coupling impedance), the
method described in IEC 62153-4-8 should shall be used.
The triaxial method for the measurement of the transfer impedance is in general suitable in the
frequency range up to 30 MHz for a 1 m sample length and 100 MHz for a 0,3 m sample length,
which corresponds to an electrical length less than 1/6 of the wavelength in the sample. A
detailed description could can be found in Clause 9 of IEC TS 62153-4-1:20132014 as well as
in IEC 62153-4-3.
5.3 Screening attenuation
The disturbing (or primary) circuit is the matched cable, assembly or component under test. The
disturbed (or secondary) circuit consists of the outer conductor (or the outermost layer in the
case of multiscreen cables or devices) of the cable, or the assembly or the device under test
and a solid metallic housing, having the device under test in its axis (see Figure 3).
The voltage peaks at the far end of the secondary circuit have to be measured. The near end
of the secondary circuit is short-circuited. For this measurement, a matched receiver is not
necessary. The expected voltage peaks at the far end are not dependent on the input
impedance of the receiver, provided that it is lower than the characteristic impedance of the
secondary circuit. However, it is an advantage to have a low mismatch, for example, by
selecting housings of sufficient an appropriate size. A detailed description could can be found
in Clause 10 of IEC TS 62153-4-1:20132014, as well as in IEC 62153-4-4.
5.4 Coupling attenuation
Balanced cables, connectors, assemblies or devices which are driven in the differential mode
may radiate a small part of the input power, due to irregularities in the symmetry. For
unscreened balanced cables, connectors, assemblies or devices, this radiation is related to the
unbalance attenuation a . For screened balanced cables, connectors or assemblies, the
u
unbalance causes a current in the screen which is then coupled by the transfer impedance and
capacitive coupling impedance into the outer circuit. The radiation is attenuated by the screen
of the component and is related to the screening attenuation a .
s
Consequently the effectiveness against electromagnetic disturbances of shielded balanced
cables, connectors or assemblies is the sum of the unbalance attenuation a of the pair and the
u
screening attenuation a of the screen. Since both quantities usually are given in a logarithmic
s
ratio, they may simply be added to form the coupling attenuation a :
c
a = a + a (8)
c u s
Coupling attenuation a is determined from the logarithmic ratio of the feeding power P and
c 1
the periodic maximum values (the envelope) of the power P (which may be radiated due to
r,max
the peaks of voltage U in the outer circuit):
 
P
 
a = 10⋅ lg Env (9)
c
 
 P 
r,max
 
where
Env is the minimum envelope curve of the measured values in dB.
The relationship of the radiated power P (related to the normalised impedance of the
r
environment Z =150Ω), to the measured power P received on the input impedance of the
S 2
receiver R is:
P
R
r,max
(10)
=
P 2Z
2,max s
There will be a variation of the voltage U on the far end, caused by the electromagnetic
coupling through the screen and superposition of the partial waves caused by the surface

– 14 – IEC 62153-4-15:2021 RLV © IEC 2021
transfer impedance Z , the capacitive coupling impedance Z (travelling to the far and near
T F
end) and the totally reflected waves from the near end.
To feed the balanced device under test, a differential mode signal is necessary. This can be
achieved with a two port network analyser (generator and receiver) and a balun or a multiport
network analyser (two generators with 180° phase shift and one receiver). The procedure to
measure coupling attenuation with a multiport network analyser is under consideration.
The coupling attenuation of screened balanced pairs describes the global effect against
electromagnetic interference (EMI) and takes into account the screening attenuation of the
screen and the unbalance attenuation of the pair. A detailed description of coupling attenuation
can be found in IEC 62153-4-9.
5.5 Tube-in-tube method
If required, measurements in accordance with IEC 62153-4-7 can also be achieved in the triaxial
cell. The measurements shall be performed in accordance with IEC 62153-4-7 but, using the
triaxial cell instead of the tube fixture (see Figure 2 and Figure 3).
6 Test procedures
6.1 General
The measurements shall be carried out at the temperature of (23 ± 3) °C. The test method
determines the transfer impedance or and the screening attenuation or the coupling attenuation
of a DUT by measuring in a triaxial test setup in accordance with IEC 62153-4-3 and IEC 62153-
4-4.
6.2 Triaxial cell
The triaxial cell consists of a rectangular housing in analogy to the principles of the triaxial test
procedures in accordance with IEC 62153-4-3 and IEC 62153-4-4. The material of the housing
shall be of non-ferromagnetic metallic material. The length of the housing should be
preferably 1 m.
Reflections of the transmitted signal may can occur (in the outer circuit) owing to the deviation
of the characteristic impedances. The plane of the short circuit at the near end (generator side)
should be therefore preferably directly on the wall of the housing.
At the receiver side, the transition of the housing to the coaxial system impedance (50 Ω-
system) should be also directly on the wall of the housing.
6.3 Cut-off frequencies, higher-order modes
The housing, respectively the triaxial cell, is in principle a cavity resonator which shows different
resonance frequencies, depending on its dimensions.
For a rectangular cavity resonator, the resonance frequencies can be calculated according to
equation (11). For this calculation, one of the parameters M,N may be set to zero. Conductive
parts inside the cavity resonator or a poor centering of the DUT in the triaxial cell may lead to
deviating resonance frequencies or to mute them.
2 2
   
c M N
f =   + 
(11)
MNP
   
a b
   
where
M,N are the number of modes (even, 2 of 3 > 0);
a,b,c are the dimensions of cavity;
c is the velocity of light in free space.
Measurements of screening attenuation can be achieved up to the first cut off frequency,
(M, N = 1).
The behaviour of the triaxial cell above the first cut off frequency is under consideration.
The triaxial test procedure uses the principle of transverse electromagnetic wave propagation
(TEM – waves). At higher frequencies, the triaxial cell becomes in principle a cavity resonator,
or a rectangular waveguide, which exhibits resonances depending on its dimensions;
see Figure 4.
Above these resonance frequencies, propagation of TEM waves is disturbed and measurements
of screening attenuation with triaxial test method are limited.

Figure 4 – Rectangular waveguide
The cut-off frequency f of a rectangular cavity resonator is given by:
c
c
f = (8)
c
2a
For a rectangular cavity resonator, the resonance frequencies can be calculated using Equation
(9). For this calculation, one of the parameters M, N, P can be set to zero.
2 22
c
 M NP 
f ++ (9)
MNP    
2 a b c
   
where
M, N are the number of modes (even, 2 of 3 > 0);
a,b,c are the dimensions of the cavity;
c is the velocity of light in free space.
NOTE Conductive parts inside the cavity resonator or a poor centring of the DUT in the triaxial cell can lead to
deviating resonance frequencies or to muting them.
Measurements of screening attenuation can be achieved up to the first cut-off frequency
(M, N = 1).
The frequency range of the triaxial cell can be extended up to and above 3 GHz by using
absorber material placed on the bottom of the cell, see Annex C.
=
– 16 – IEC 62153-4-15:2021 RLV © IEC 2021
6.4 Test equipment
The measurements can be performed using a vector network analyser (VNA) or alternatively a
discre
...

IEC 62153-4-15 ®
Edition 2.0 2021-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Metallic cables and other passive components test methods –
Part 4-15: Electromagnetic compatibility (EMC) – Test method for measuring
transfer impedance and screening attenuation – or coupling attenuation with
triaxial cell
Méthodes d’essais des câbles métalliques et autres composants passifs –
Partie 4-15: Compatibilité électromagnétique (CEM) – Méthode d’essai pour
le mesurage de l’impédance de transfert et de l’affaiblissement d’écran –
ou de l’affaiblissement de couplage avec cellule triaxiale

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IEC 62153-4-15 ®
Edition 2.0 2021-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Metallic cables and other passive components test methods –

Part 4-15: Electromagnetic compatibility (EMC) – Test method for measuring

transfer impedance and screening attenuation – or coupling attenuation with

triaxial cell
Méthodes d’essais des câbles métalliques et autres composants passifs –

Partie 4-15: Compatibilité électromagnétique (CEM) – Méthode d’essai pour

le mesurage de l’impédance de transfert et de l’affaiblissement d’écran –

ou de l’affaiblissement de couplage avec cellule triaxiale

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.100.10; 33.120.10 ISBN 978-2-8322-1003-2

– 2 – IEC 62153-4-15:2021 © IEC 2021
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references. 7
3 Terms and definitions . 8
4 Physical background . 10
5 Principle of the test methods . 10
5.1 General . 10
5.2 Transfer impedance . 12
5.3 Screening attenuation . 12
5.4 Coupling attenuation . 12
5.5 Tube-in-tube method . 12
6 Test procedures . 12
6.1 General . 12
6.2 Triaxial cell . 12
6.3 Cut-off frequencies, higher-order modes . 13
6.4 Test equipment . 14
6.5 Calibration procedure . 14
6.6 Test leads and connecting cables to the DUT . 15
7 Sample preparation . 15
7.1 Coaxial connector or assembly or quasi-coaxial component . 15
7.2 Balanced or multipin connectors or components . 15
7.3 Cable assemblies . 16
7.4 Other screened devices . 17
8 Transfer impedance (short-matched) . 17
8.1 General . 17
8.2 Principle block diagram of transfer impedance . 17
8.3 Measuring procedure . 18
8.4 Evaluation of test results . 18
8.5 Test report . 18
9 Screening attenuation . 19
9.1 General . 19
9.2 Impedance matching . 19
9.3 Measuring with matched conditions . 19
9.3.1 Procedure . 19
9.3.2 Evaluation of test results . 19
9.4 Measuring with mismatch . 20
9.4.1 General . 20
9.4.2 Evaluaton of test results . 20
9.5 Test report . 21
10 Coupling attenuation . 21
10.1 General . 21
10.2 Procedure . 21
10.2.1 Coupling attenuation with balun . 21
10.2.2 Balunless coupling attenuation . 22
10.3 Expression of results . 22

10.4 Test report . 23
Annex A (informative) Principle of the triaxial test procedure . 24
A.1 General . 24
A.2 Transfer impedance . 25
A.3 Screening attenuation . 25
A.4 Coupling attenuation . 26
Annex B (informative) Triaxial cell . 28
Annex C (normative) Triaxial absorber cell . 30
C.1 Cut-off frequencies, higher order modes . 30
C.2 Absorber . 31
C.3 Influence of absorber . 33
Annex D (informative) Application of a moveable shorting plane. 34
D.1 Coupling transfer function . 34
D.2 Effect of the measurement length on the measurement cut-off frequency . 35
D.3 Details of the movable shorting plane . 35
D.4 Measurement results . 37
Annex E (informative) Correction in the case that the receiver input impedance R is
higher than the characteristic impedance of the outer circuit Z . 39
E.1 Impedance Z lower than the input impedance of the receiver . 39
E.2 Correction . 40
Annex F (informative) Test adapter . 41
Annex G (informative) Attenuation versus scattering parameter S . 42
Bibliography . 44

Figure 1 – Definition of Z . 8
T
Figure 2 – Principle depiction of the triaxial test setup (tube) to measure transfer
impedance and screening attenuation with tube in tube in accordance with IEC 62153-4-7 . 11
Figure 3 – Principle depiction of the triaxial cell to measure transfer impedance and
screening attenuation of connectors or assemblies with tube in tube in accordance with
IEC 62153-4-7 . 11
Figure 4 – Rectangular waveguide . 13
Figure 5 – Preparation of balanced or multipin connectors for transfer impedance and
screening attenuation. 16
Figure 6 – Preparation of balanced or multipin connectors for coupling attenuation
measurement . 16
Figure 7 – Test setup (principle) for transfer impedance measurement in accordance
with test method B of IEC 62153-4-3 . 17
Figure 8 – Principle test setup for balunless coupling attenuation measurement
according to IEC 62153-4-9 . 22
Figure A.1 – Principle test setup to measure transfer impedance and screening
attenuation . 24
Figure A.2 – Equivalent circuit of the principle of the test setup in Figure A.1 . 25
Figure A.3 – Coupling attenuation, principle of test setup with balun and standard tube . 26
Figure A.4 – Coupling attenuation, principle of setup with multiport VNA and standard
head . 27
Figure B.1 – Principle depiction of the triaxial cell to measure transfer impedance and
screening attenuation on a connector with tube-in-tube according to IEC 62153-4-7 . 28

– 4 – IEC 62153-4-15:2021 © IEC 2021
Figure B.2 – Examples of different designs of triaxial cells . 29
Figure C.1 – Cavity or rectangular waveguide . 30
Figure C.2 – Comparison of the measurements of a RG 214 cable with 40 mm tube
and triaxial cells . 31
Figure C.3 – Principle of the triaxial cell with tube in tube and ferrite tiles as absorber . 31
Figure C.4 – Comparison of the measurements of an RG 214 with 40 mm tube and
triaxial cells with magnetic absorber . 32
Figure C.5 – Examples of magnetic flat absorber . 32
Figure C.6 – Setup for correction measurement . 33
Figure C.7 – Correction measurement . 33
Figure D.1 – Measured coupling transfer function of a braided screen versus frequency
with the triaxial cell . 34
Figure D.2 – Cross-section of triaxial cell with movable shorting plane . 36
Figure D.3 – Crosscut of plane shortening housing and tube-in-tube . 36
Figure D.4 – Detail H of Figure D.3: contact between plane and housing . 37
Figure D.5 – Detail G of Figure D.3: contact between plane and tube-in-tube . 37
Figure D.6 – Compilation of transfer impedance test results with different shorting
plane distances . 38
Figure E.1 – Example of forward transfer scattering parameter S for different
impedances in the outer circuit where the receiver input impedance is 50 Ω . 39
Figure E.2 – DUT with uniform cylindrical shape in the centre of the cell . 40
Figure F.1 – Principle of the test setup to measure transfer impedance and screening
or coupling attenuation of connectors . 41
Figure F.2 – Principle of the test setup to measure transfer impedance and screening
attenuation on a cable assembly . 41
Figure G.1 – Measurement with HP8753D of S of a 3 dB attenuator . 42
Figure G.2 – Measurement with ZVRE of S of a 3 dB attenuator . 43
Table 1 – IEC 62153-4 series, Metallic communication cable test methods – Test
procedures with triaxial test setup . 10

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
METALLIC CABLES AND OTHER PASSIVE
COMPONENTS TEST METHODS –
Part 4-15: Electromagnetic compatibility (EMC) – Test method for
measuring transfer impedance and screening attenuation –
or coupling attenuation with triaxial cell

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 this end and
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Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
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6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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 62153-4-15 has been prepared by IEC technical committee 46:
Cables, wires, waveguides, R.F. connectors, R.F. and microwave passive components and
accessories.
This second edition cancels and replaces the first edition published in 2015. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) measurement of coupling attenuation of balanced connectors, assemblies and components
with balun and balunless added;
b) application of a test adapter was added;
c) application of a moveable shorting plane;

– 6 – IEC 62153-4-15:2021 © IEC 2021
d) application of the triaxial "absorber" cell;
e) correction of test results in the case that the receiver input impedance R is higher than the
characteristic impedance of the outer circuit Z .
The text of this International Standard is based on the following documents:
FDIS Report on voting
46/814/FDIS 46/822/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
A list of all the parts in the IEC 62153-4 series, published under the general title Metallic
communication cable test methods – Electromagnetic compatibility (EMC), can be found on the
IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document 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.

METALLIC CABLES AND OTHER PASSIVE
COMPONENTS TEST METHODS –
Part 4-15: Electromagnetic compatibility (EMC) – Test method for
measuring transfer impedance and screening attenuation –
or coupling attenuation with triaxial cell

1 Scope
This part of IEC 62153 specifies the procedures for measuring with triaxial cell the transfer
impedance, screening attenuation or the coupling attenuation of connectors, cable assemblies
and components, for example accessories for analogue and digital transmission systems, and
equipment for communication networks and cabling.
Measurements can be achieved by applying the device under test directly to the triaxial cell or
with the tube-in-tube method in accordance with IEC 62153-4-7.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 61196-1, Coaxial communication cables – Part 1: Generic specification – General,
definitions and requirements
IEC TS 62153-4-1:2014, Metallic communication cable test methods – Part 4-1:
Electromagnetic Compatibility (EMC) − Introduction to electromagnetic screening
measurements
IEC 62153-4-3, Metallic communication cable test methods – Part 4-3: Electromagnetic
compatibility (EMC) − Surface transfer impedance − Triaxial method
IEC 62153-4-4:2015, Metallic communication cable test methods – Part 4-4: Electromagnetic
compatibility (EMC) – Test method for measuring of the screening attenuation a up to and
S
above 3 GHz, triaxial method
IEC 62153-4-7, Metallic communication cable test methods – Part 4-7: Electromagnetic
compatibility (EMC) – Test method for measuring the transfer impedance Z and the screening
T
attenuation as or coupling attenuation ac of connectors and assemblies up to and above 3 GHz
– Triaxial Tube in tube method
IEC 62153-4-8, Metallic cables and other passive components – Test methods – Part 4-8:
Electromagnetic compatibility (EMC) – Capacitive coupling admittance
IEC 62153-4-9:2018, Metallic communication cable test methods – Part 4-9: Electromagnetic
compatibility (EMC) – Coupling attenuation of screened balanced cables, triaxial method
IEC 62153-4-10, Metallic communication cable test methods – Part 4-10: Electromagnetic
compatibility (EMC) – Transfer impedance and screening attenuation of feed-throughs and
electromagnetic gaskets – Double coaxial test method

– 8 – IEC 62153-4-15:2021 © IEC 2021
IEC 62153-4-16, Metallic communication cable test methods – Part 4-16: Electromagnetic
compatibility (EMC) – Extension of the frequency range to higher frequencies for transfer
impedance and to lower frequencies for screening attenuation measurements using the triaxial
set-up
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61196-1 and the
following apply.
3.1
triaxial cell
rectangular housing in analogy to the principles of the triaxial test procedure, consisting of a
non-ferromagnetic metallic material
Note 1 to entry: The triaxial test procedure is described in IEC 62153-4-3 and IEC 62153-4-4.
3.2
surface transfer impedance
Z
T
for an electrically short screen, quotient of the longitudinal voltage U induced to the inner
circuit by the current I fed into the outer circuit or vice versa [Ω] (see Figure 1)
Note 1 to entry: The value Z of an electrically short screen is expressed in ohms [Ω] or decibels in relation to 1 Ω.
T
Figure 1 – Definition of Z
T
U
Z =
T (1)
I
 Z 
T
 
Z dB(Ω)= 20⋅lg (2)
T
 
1Ω
 
3.3
effective transfer impedance
Z
TE
impedance defined as:
Z = max Z ± Z
TE F T
(3)
where Z is the capacitive coupling impedance
F
3.4
screening attenuation
a
s
for electrically long devices, i.e. above the cut-off frequency, logarithmic ratio of the feeding
power P and the periodic maximum values of the coupled power P in the outer circuit
1 r,max
 
P
(4)
a 10⋅lgEnv 
s
 
P
r,max
 
Note 1 to entry: The screening attenuation of an electrically short device is defined as:
150Ω
a 20⋅lg (5)
s
Z
TE
where
150 Ω is the standardised impedance of the outer circuit.
3.5
coupling attenuation
a
c
for a screened balanced device, sum of the unbalance attenuation a of the symmetric pair and
u
the screening attenuation a of the screen of the device under test
s
Note 1 to entry: For electrically long devices, i.e. above the cut-off frequency, the coupling attenuation a is defined
c
as the logarithmic ratio of the feeding power P and the periodic maximum values of the coupled power P in the
1 r,max
outer circuit.
3.6
coupling length
length of cable that is inside the test jig, i.e. the length of the screen under test
Note 1 to entry: The coupling length is electrically short, if
λ c
o
o
>⋅10 ε or f < (6)
r1
L
10⋅⋅L ε
r1
or electrically long, if
c
λ
o
o
≤⋅2 εε− or f > (7)
r1 r2
L
2⋅⋅L εε−
r1 r2
where
L is the effective coupling length, in m;
λ is the free space wavelength, in m;
ε is the resulting relative permittivity of the dielectric of the cable;
r1
ε is the resulting relative permittivity of the dielectric of the secondary circuit;
r2
f is the frequency, in Hz;
c is the velocity of light in free space, in m/s.
=
=
– 10 – IEC 62153-4-15:2021 © IEC 2021
3.7
device under test
DUT
connector with mating connector and attached connecting cables or cable assembly consisting
of the assembly with their attached mated connectors and with connecting cables
4 Physical background
See IEC TS 62153-4-1, IEC 62153-4-3, IEC 62153-4-4, and Annex A to Annex F.
5 Principle of the test methods
5.1 General
The IEC 62153-4 series describes different test procedures to measure screening effectiveness
on communication cables, connectors and components.
Table 1 gives an overview of the test procedures of the IEC 62153-4 series carried out with the
triaxial test setup.
Table 1 – IEC 62153-4 series, Metallic communication cable test methods –
Test procedures with triaxial test setup
IEC 62153-4 series Metallic communication cable test methods – Electromagnetic compatibility
(EMC)
IEC TS 62153-4-1 Introduction to electromagnetic screening measurements
IEC 62153-4-3 Surface transfer impedance – Triaxial method
IEC 62153-4-4 Shielded screening attenuation, test method for measuring of the screening attenuation
a up to and above 3 GHz
S
IEC 62153-4-7 Shielded screening attenuation test method for measuring the Transfer impedance Z
T
and the screening attenuation a or the coupling attenuation a of RF-connectors and
S C
assemblies up to and above 3 GHz, tube in tube method
IEC 62153-4-9 Coupling attenuation of screened balanced cables, triaxial method
IEC 62153-4-10 Shielded screening attenuation test method for measuring the screening effectiveness
of feedtroughs and electromagnetic gaskets double coaxial method
IEC 62153-4-15 Test method for measuring transfer impedance and screening attenuation – or coupling
attenuation with triaxial cell
IEC 62153-4-16 Extension of the frequency range to higher frequencies for transfer impedance and to
lower frequencies for screening attenuation measurements using the triaxial setup

Larger connectors, cable assemblies, and components do not fit into the commercially available
test rigs (tubes) of the triaxial test procedures of IEC 62153-4-3, IEC 62153-4-4, and
IEC 62153-4-7, respectively, which were designed originally to measure transfer impedance
and screening attenuation on communication cables, connectors, and assemblies.
Since rectangular housings with RF-tight caps are easier to manufacture than tubes, the "triaxial
cell" was designed to test larger devices, such as connectors, assemblies and components.
The principles of the triaxial test procedures in accordance with IEC 62153-4-3, IEC 62153-4-4
and IEC 62153-4-7 can be transferred to rectangular housings. Tubes and rectangular housings
may be operated in combination in one test setup (see Figure 2 and Figure 3).

Figure 2 – Principle depiction of the triaxial test setup (tube) to measure transfer
impedance and screening attenuation with tube in tube in accordance with IEC 62153-4-7
In principle, the triaxial cell can be used in accordance with all triaxial procedures of Table 1,
where originally a cylindrical tube is used. The screening effectiveness of connectors,
assemblies or other components can be measured, in principle, in the tube as well as in the
triaxial cell. Test results of measurements with tubes and with triaxial cells correspond well.

Figure 3 – Principle depiction of the triaxial cell to measure transfer
impedance and screening attenuation of connectors or assemblies
with tube in tube in accordance with IEC 62153-4-7
The triaxial cell test setup is based on the triaxial system in accordance with IEC 62153-4-3
and IEC 62153-4-4, consisting of the DUT, a solid metallic housing and an RF-tight extension
tube (optional). The matched device under test (DUT), which is fed by a generator via a
connecting cable, forms the disturbing circuit, which may also be designated as the inner or the
primary circuit.
The disturbed circuit, which may also be designated as the outer or the second circuit, is formed
by the outer conductor of the device under test, connected to the connecting cable (or the tube
in tube, if applicable) and a solid metallic housing or cell having the DUT in its axis.

– 12 – IEC 62153-4-15:2021 © IEC 2021
5.2 Transfer impedance
The test determines the screening effectiveness of a shielded device by applying a well-defined
current and voltage to the screen of the cable, the assembly or the device under test and
measuring the induced voltage in the secondary circuit in order to determine the surface transfer
impedance. This test measures only the galvanic and magnetic components of the transfer
impedance. To measure the electrostatic component (the capacitance coupling impedance), the
method described in IEC 62153-4-8 shall be used.
The triaxial method for the measurement of the transfer impedance is in general suitable in the
frequency range up to 30 MHz for a 1 m sample length and 100 MHz for a 0,3 m sample length,
which corresponds to an electrical length less than 1/6 of the wavelength in the sample. A
detailed description can be found in Clause 9 of IEC TS 62153-4-1:2014 as well as in
IEC 62153-4-3.
5.3 Screening attenuation
The disturbing (or primary) circuit is the matched cable, assembly or component under test. The
disturbed (or secondary) circuit consists of the outer conductor (or the outermost layer in the
case of multiscreen cables or devices) of the cable, or the assembly or the device under test
and a solid metallic housing, having the device under test in its axis (see Figure 3).
The voltage peaks at the far end of the secondary circuit have to be measured. The near end
of the secondary circuit is short-circuited. For this measurement, a matched receiver is not
necessary. The expected voltage peaks at the far end are not dependent on the input
impedance of the receiver, provided that it is lower than the characteristic impedance of the
secondary circuit. However, it is an advantage to have a low mismatch, for example, by
selecting housings of an appropriate size. A detailed description can be found in Clause 10 of
IEC TS 62153-4-1:2014, as well as in IEC 62153-4-4.
5.4 Coupling attenuation
The coupling attenuation of screened balanced pairs describes the global effect against
electromagnetic interference (EMI) and takes into account the screening attenuation of the
screen and the unbalance attenuation of the pair. A detailed description of coupling attenuation
can be found in IEC 62153-4-9.
5.5 Tube-in-tube method
If required, measurements in accordance with IEC 62153-4-7 can also be achieved in the triaxial
cell, using the triaxial cell instead of the tube fixture (see Figure 2 and Figure 3).
6 Test procedures
6.1 General
The measurements shall be carried out at the temperature of (23 ± 3) °C. The test method
determines the transfer impedance and the screening or the coupling attenuation of a DUT by
measuring in a triaxial test setup in accordance with IEC 62153-4-3 and IEC 62153-4-4.
6.2 Triaxial cell
The triaxial cell consists of a rectangular housing in analogy to the principles of the triaxial test
procedures in accordance with IEC 62153-4-3 and IEC 62153-4-4. The material of the housing
shall be of non-ferromagnetic metallic material. The length of the housing should be
preferably 1 m.
Reflections of the transmitted signal can occur (in the outer circuit) owing to the deviation of
the characteristic impedances. The plane of the short circuit at the near end (generator side)
should be therefore preferably directly on the wall of the housing.
At the receiver side, the transition of the housing to the coaxial system impedance (50 Ω-
system) should be also directly on the wall of the housing.
6.3 Cut-off frequencies, higher-order modes
The triaxial test procedure uses the principle of transverse electromagnetic wave propagation
(TEM – waves). At higher frequencies, the triaxial cell becomes in principle a cavity resonator,
or a rectangular waveguide, which exhibits resonances depending on its dimensions;
see Figure 4.
Above these resonance frequencies, propagation of TEM waves is disturbed and measurements
of screening attenuation with triaxial test method are limited.

Figure 4 – Rectangular waveguide
The cut-off frequency f of a rectangular cavity resonator is given by:
c
c
(8)
f =
c
2a
For a rectangular cavity resonator, the resonance frequencies can be calculated using Equation
(9). For this calculation, one of the parameters M, N, P can be set to zero.
2 22
c M NP
   
f ++ (9)
MNP
   
2 a b c
   
where
M, N are the number of modes (even, 2 of 3 > 0);
a,b,c are the dimensions of the cavity;
c is the velocity of light in free space.
NOTE Conductive parts inside the cavity resonator or a poor centring of the DUT in the triaxial cell can lead to
deviating resonance frequencies or to muting them.
Measurements of screening attenuation can be achieved up to the first cut-off frequency
(M, N = 1).
The frequency range of the triaxial cell can be extended up to and above 3 GHz by using
absorber material placed on the bottom of the cell, see Annex C.
=
– 14 – IEC 62153-4-15:2021 © IEC 2021
6.4 Test equipment
The measurements can be performed using a vector network analyser (VNA) or alternatively a
discrete signal generator and a selective measuring receiver.
The measuring equipment consists of the following:
a) a vector network analyser (with S-parameter test set), or
b) a signal generator with the same characteristic impedance as the coaxial system of the
cable under test or with an impedance adapter and complemented with a power amplifier, if
necessary, for very high screening attenuation, in combination with a receiver with optional
low-noise amplifier for very high screening attenuation;
c) impedance-matching circuit if necessary:
– primary side: nominal impedance of generator,
– secondary side: nominal impedance of the inner circuit,
– loss: > 10 dB.
d) balun for impedance matching of the unbalanced generator output signal to the
characteristic impedance of balanced cables for measuring the coupling attenuation.
Requirements for the balun are given in IEC 62153-4-9:2018, 6.3. Alternatively, a VNA with
a mixed mode option may be used, see IEC TR 61156-1-2.
Optional equipment is:
– time domain reflectometer (TDR) with a rise time of less than 200 ps or network analyser
with maximum frequency up to 5 GHz and time domain capability;
– absorber material.
6.5 Calibration procedure
The calibration shall be established at the same frequency points at which the measurement of
the transfer impedance is done, i.e. in a logarithmic frequency sweep over the whole frequency
range, which is specified for the transfer impedance.
When using a vector network analyser with S-parameter test-set, a full two-port calibration shall
be established, including the connecting cables used to connect the test setup to the test
equipment. The reference planes for the calibration are the connector interface of the
connecting cables.
When using a (vector) network analyser without an S-parameter test-set, i.e. by using a power
splitter, a THRU calibration shall be established that includes the test leads used to connect
the test setup to the test equipment.
When using a separate signal generator and receiver, the composite loss of the test leads shall
be measured and the calibration data shall be saved, so that the results can be corrected:
 P
a =10⋅lg =−20⋅lg S (10)
( )
 
cal 21
P
 2
where
a is the attenuation obtained at the calibration procedure, in dB;
cal
P is the power fed during calibration procedure, in W;
P is the power at the receiver during calibration procedure, in W;
S is the measured S-parameter.
If amplifiers are used, their gain shall be measured over the above-mentioned frequency range
and the data shall be saved.
If an impedance-matching adapter or balun is used, the attenuation shall be measured over the
above-mentioned frequency range, and the data shall be saved.
6.6 Test
...