IEC TR 62153-4-1:2007

Metallic communication cable test methods - Part 4-1: Electromagnetic compatibility (EMC) - Introduction to electromagnetic (EMC) screening measurements

It gives a brief introduction to basic concepts and terms that reveal the common features of various test methods.

General Information

• Status: Published
• Publication Date: 20-Nov-2007
• ICS: 33.100.10 - Emission
• ICS: 33.120.10 - Coaxial cables. Waveguides
• Technical Committee: TC 46 - Cables, wires, waveguides, RF connectors, RF and microwave passive components and accessories
• Drafting Committee: WG 5 - TC 46/WG 5
• Current Stage: DELPUB - Deleted Publication
• Start Date: 12-May-2010
• Completion Date: 26-Oct-2025

Relations

• Replaces: IEC TR 61917:1998 - Cables, cable assemblies and connectors - Introduction to electromagnetic (EMC) screening measurements
• Effective Date: 05-Sep-2023
• Revised: IEC TR 62153-4-1:2010 - Metallic communication cable test methods - Part 4-1: Electromagnetic compatibility (EMC) - Introduction to electromagnetic (EMC) screening measurements
• Effective Date: 05-Sep-2023

Overview

IEC TR 62153-4-1:2007 is a Technical Report from the International Electrotechnical Commission (IEC) that introduces fundamental concepts for electromagnetic compatibility (EMC) screening measurements of metallic communication cables. As part of the IEC 62153 series on metallic communication cable test methods, this report (Edition 1.0, 2007) summarizes common features of various test methods and provides a conceptual basis for measuring and interpreting cable screening performance.

Key Topics

The report focuses on core EMC screening concepts and measurement parameters rather than prescriptive test procedures. Major technical topics include:

• Surface transfer impedance (ZT) - intrinsic parameter describing how well a cable screen prevents magnetic coupling.
• Capacitive coupling admittance (Yc) - describing electric-field coupling between conductor and screen.
• Coupling transfer functions and summing effects (near-end and far-end coupling) and the influence of cable length.
• Transfer impedance of braided-wire outer conductors and screens - practical behaviour of braid constructions.
• Test set-ups and measurement possibilities - including triaxial set-ups, double short-circuited methods and assessment of connector and assembly screening.
• Simulation and frequency-response analysis, including cut-off frequency × length products and the impact of dielectric permittivity on screening.
• Equivalent circuit models, reciprocity/symmetry and load conditions for interpreting measurement results.

Practical Applications

This Technical Report is intended to help professionals understand, compare and interpret EMC screening measurements. Typical uses include:

• Evaluating shielding performance of coaxial, braided and multi-conductor cable assemblies.
• Selecting cable and connector designs for improved EMC/screening effectiveness in industrial, telecom and broadcast systems.
• Preparing test plans and interpreting results in EMC test laboratories that perform transfer impedance and related measurements.
• Informing product specifications, procurement and compliance strategies where cable screening affects system immunity and emissions.
• Supporting simulation and modelling efforts during cable design and troubleshooting of EMC problems.

Who Should Use It

• EMC engineers and test laboratory personnel
• Cable and connector designers and manufacturers
• System integrators and telecom/broadcast engineers
• Standards writers and technical procurement teams

Related Standards

• IEC TR 62153 series (metallic communication cable test methods) - this report provides introductory EMC screening concepts referenced by more specific measurement standards.
• IEC TR 62153-4-1 replaces earlier IEC/TR 61917 (1998) and should be read alongside other IEC EMC measurement standards relevant to cable screening and transfer impedance testing.

Keywords: IEC TR 62153-4-1, electromagnetic compatibility, EMC screening measurements, metallic communication cable test methods, transfer impedance, surface transfer impedance, triaxial set-up, cable shielding, screening effectiveness.

Standards Content (Sample)

IEC/TR 62153-4-1
Edition 1.0 2007-11
TECHNICAL
REPORT
Metallic communication cable test methods –
Part 4-1: Electromagnetic compatibility (EMC) – Introduction to electromagnetic
(EMC) screening measurements
IEC/TR 62153-4-1:2007(E)
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IEC/TR 62153-4-1
Edition 1.0 2007-11
TECHNICAL
REPORT
Metallic communication cable test methods –
Part 4-1: Electromagnetic compatibility (EMC) – Introduction to electromagnetic
(EMC) screening measurements
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XA
ICS 33.100; 33.120.10 ISBN 2-8318-9364-X

– 2 – TR 62153-4-1 © IEC:2007(E)

CONTENTS
FOREWORD.5

INTRODUCTION.7

1 Scope.8

2 Normative references.8

3 List of symbols.9

4 Electromagnetic phenomena.10

5 Intrinsic screening parameters of short cables.12
5.1 Surface transfer impedance, Z .12
T
5.2 Capacitive coupling admittance, Y .12
c
5.3 Injecting with arbitrary cross-sections.14
5.4 Reciprocity and symmetry.14
5.5 Arbitrary load conditions .14
6 Long cables – Coupled transmission lines .14
7 Transfer impedance of a braided-wire outer conductor or screen.20
8 Test possibilities .26
8.1 Measuring the transfer impedance of coaxial cables.26
8.2 Measuring the transfer impedance of cable assemblies.27
8.3 Measuring the transfer impedance of connectors .27
8.4 Calculated maximum screening level .27
9 Comparison of frequency response of different triaxial test set-ups to measure
transfer impedance of cable screens.32
9.1 Introductory remark .32
9.2 Physical basics.32
9.3 Simulations.35
9.4 Conclusion .49

Bibliography .50

Additional reading .51

Figure 1 – Incident (i), scattered (s) and resulting total electromagnetic fields (E , H )
t t
with induced surface current- and charge- densities J (A/m) and σ (C/m ) .11
Figure 2 – Defining and measuring screening parameters – Triaxial set-up .11
Figure 3a – Equivalent circuit for the definition and possible testing of Z .13
Figure 3b – Equivalent circuit for the definition and possible testing of Y = j ωC .13
c T
Figure 3c – Definition of electrical quantities in a set-up that is matched at all ends .13
Figure 3 – Defining and measuring screen parameters – Equivalent circuits.13
Figure 4 – Summing function S{}l ⋅ f for near (n) and far (f) end coupling .17
Figure 5a – Transfer impedance of a typical single braid screen .18
Figure 5b – Coupling transfer function for the same cable with negligible Z (Z << Z ):
F F T
frequency responses of Figure 4 and Figure 5a added on log scale .18
Figure 5 – The effect of the summing function .18

TR 62153-4-1 © IEC:2007(E) – 3 –

Figure 6 – The effects of the Z and Z to the coupling transfer functions T and T .19
T F n f
Figure 7 – l ×S: complete length dependent factor in the coupling function T (see Table 1) .20

Figure 8 – Transfer impedance of typical cables .21

Figure 9a – Complete flux .21

Figure 9b – Left-hand lay contribution.21

Figure 9c – Right-hand lay contribution.21

Figure 9 – Magnetic coupling in the braid.21

Figure 10a – Complex plane, Z = Re Z + j Im Z frequency f as parameter .22
T T T,
Figure 10b – Magnitude (amplitude), | Z (f) | .23
T
Figure 10 – Measured transfer impedance Z (d.c. resistance Z (d.c.) set to the value
T T
of 10 mΩ/m.23
Figure 11a – Overbraided cable.24
Figure 11b – Underbraided cable.24
Figure 11 – Typical Z (time) step response of an overbraided and underbraided single
T
braided outer conductor of a coaxial cable.24
Figure 12a – Contributions to the transfer impedance .25
Figure 12b – Significant elements of circuits (1) and (2).25
Figure 12 – Z equivalent circuits of a braided-wire screen.25
T
Figure 13 – Example of visualization of the maximum measurable screening level .28
Figure 14 – Triaxial set-up for the measure- ment of the transfer impedance Z .32
T
Figure 15 – Equivalent circuit of the triaxial set-up.32
Figure 16 – Simulation of frequency response for different factors of v = Z /R

2 2,f
with ε = 2,3 (solid PE), ε = 1,0, n = 0,659.37
r1 r2
Figure 17 – Simulation of the frequency response for different factors of v = Z /R

2 2f
with ε = 1,6 (foam PE), ε = 1,0, n = 0,791 .37
r1 r2
Figure 18 – Simulation of frequency response for different factors of v = Z /R

2 2f
with ε ε 38
= 1,3 (foam PE), = 1,0, n = 0,877 .
r1 r2
Figure 19 – Simulation of frequency response for different factors of v = Z /R
2 2f
with ε = 5 (PVC), ε = 1,0, n = 0,447 .38
r1 r2
Figure 20 – Simulation of the 3 dB cut off wavelength (L/λ ) as a function of factor
n = ε / ε given for different factors v = Z /R .39
r,2 r,1
2 2f
Figure 21 – Interpolation of the simulated 3 dB cut off wavelength (L/λ ) as a function
of factor n = ε / ε given for different factors v = Z /R .39
r,2 r,1 2 2f
Figure 22 – 3 dB cut-off frequency length product as a function of dielectric permittivity
of the inner circuit (cable) given for different factors v = Z /R .40
2 2,f
Figure 23 – Measurement result of the normalized voltage drop of a single braid screen
in the triaxial set-up for different factors of v = Z /R with ε = 2,3 (PE), ε = 1,0,

2 2,f r1 r2
n = 0,659, Z = 130 Ω, L = 1 m .41
Figure 24 – Measurement result of the normalized voltage drop of a single braid screen
in the triaxial set-up for different factors of v = Z /R with ε = 1,6 (foam PE),
2 2,f r1
ε = 1,0, n = 0,791, Z = 130 Ω, L = 1 m.41
r2 2
Figure 25 – Triaxial set-up (measuring tube), double short-circuited method .42
Figure 26 – Simulation of the frequency response for different factors of v = Z /R

2 2,f
with ε = 2,3 (solid PE), ε = 1,0, n = 0,659.43
r1 r2
Figure 27 – Simulation of the frequency response for different factors of v = Z R
/
2 2,f
with ε = 1,6 (foam PE), ε = 1,0, n = 0,791 .43
r1 r2
– 4 – TR 62153-4-1 © IEC:2007(E)

Figure 28 – Simulation of the frequency response for different factors of v = Z /R

2 2,f
with ε = 1,3 (foam PE), ε = 1,0, n = 0,877 .44
r1 r2
Figure 29 – Simulation of the frequency response for different factors of v = Z /R

2 2,f
with ε = 5 (PVC), ε = 1,0, n = 0,447 .44

r1 r2
Figure 30 – Interpolation of the simulated 3 dB cut-off wavelength (L/λ ) as a function
of factor n = ε / ε given for different factors v = Z /R .45
r,2 r,1
2 2,f
Figure 31 – 3 dB cut-off frequency length product as a function of dielectric permittivity

of the inner circuit (cable) given for different factors v = Z /R .46
2 2,f
Figure 32 – Simulation of the frequency response for different factors of v = Z /R

2 2,f
with ε = 2,3 (PE), ε = 5 (PVC), n = 1,474 .47
r1 r2
Figure 33 – Interpolation of the simulated 3 dB cut off wavelength (L/λ ) as a function
of factor n = ε / ε given for v = Z /R <<1 .48
r,2 r,1 2 2f
Figure 34 – 3 dB cut-off frequency length product as a function of the dielectric
permittivity of the inner circuit (cable) given for different factors
n = ε / ε , v = Z /R <<1 .48
r,2 r,1 2 2,f
Table 1 – The coupling transfer function T (coupling function).16
Table 2 – Screening effectiveness of cable test methods for surface transfer impedance Z .30
T
Table 3 – Load conditions of the different set-ups.34
Table 4 – Parameters of the different set-ups .36
Table 5 – Cut-off frequency length product .40
Table 6 – Typical values for factor v, for an inner tube diameter of 40 mm and a
generator output impedance of 50 Ω.42
Table 7 – Cut-off frequency length product .45
Table 8 – Material combinations and factor n.47
Table 9 – Cut-off frequency length product for some typical cables in the different set-
ups .49

TR 62153-4-1 © IEC:2007(E) – 5 –

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
METALLIC COMMUNICATION CABLE TEST METHODS –

Part 4-1: Electromagnetic compatibility (EMC) –

Introduction to electromagnetic (EMC) screening measurements

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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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.

The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC/TR 62153-4-1, which is a technical report, has been prepared by IEC technical committee
46: Cables, wires, waveguides, R.F. connectors, R.F. and microwave passive components and
accessories.
This publication cancels and replaces IEC/TR 61917, published in 1998.

– 6 – TR 62153-4-1 © IEC:2007(E)

The text of this technical report is based on the following documents:

Enquiry draft Report on voting

46/199/DTR 46/253/RVC
Full information on the voting for the approval of this technical report can be found in the report

on voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

The committee has decided that the contents of this publication will remain unchanged until the
maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

TR 62153-4-1 © IEC:2007(E) – 7 –

INTRODUCTION
Screening is one basic way of achieving electromagnetic compatibility (EMC). However, a

confusingly large number of methods and concepts is available to test for the screening quality

of cables and related components, and for defining their quality.

IEC/TR 62153-4-1 provides a brief introduction to basic concepts and terms trying to reveal the

common features of apparently different test methods. It should assist in correct interpretation

of test data, and in the better understanding of screening (or shielding) and related

specifications and standards.
– 8 – TR 62153-4-1 © IEC:2007(E)

METALLIC COMMUNICATION CABLE TEST METHODS –

Part 4-1: Electromagnetic compatibility (EMC) –

Introduction to electromagnetic (EMC) screening measurements

1 Scope
IEC/TR 62153-4-1, which is a technical report, gives a brief introduction to basic concepts and

terms that reveal the common features of various test methods.
2 Normative references
The following referenced documents are indispensable for the application of this document. For
dated references, only the edition cited applies. For undated references, the latest edition of
the referenced document (including any amendments) applies.
IEC 60096-4-1:1990, Radio-frequency cables – Part 4: Specification for superscreened cables
– Section 1: General requirements and test methods
IEC 60169-1-3:1988, Radio frequency connectors – Part 1: General requirements and
measuring methods – Section 3: Electrical tests and measuring procedures – Screening
effectiveness
IEC 61196-1:2005, Coaxial communication cables – Part 1: Generic specification – General,
definitions and requirements – Second edition
IEC 61726: Cable assemblies, cables, connectors and passive microwave components –
Screening attenuation measurement by the reverberation chamber method
IEC 62153-4-2, Metallic communication cables test methods – Part 4-2: Electromagnetic
compatibility (EMC) – Screening and coupling attenuation – Injection clamp method
IEC 62153-4-3, Metallic communication cables test methods – Part 4-3: Electromagnetic
compatibility (EMC) – Surface transfer impedance – Triaxial method
IEC 62153-4-5, Metallic communication cables test methods – Part 4-5: Electromagnetic

compatibility (EMC) – Coupling or screening attenuation – Absorbing clamp method
IEC 62153-4-7, Metallic communication cables test methods – Part 4-7: Electromagnetic
compatibility (EMC) – Test method for measuring the transfer impedance and the screening –
or the coupling attenuation – Tube in tube method
IEC 62153-4-9, Metallic communication cable test methods – Part 4-9: Electromagnetic
Compatibility (EMC) – Coupling attenuation of screened balanced cables, triaxial method
EN 50289-1-6, Communication cables – Specification for test methods – Electrical test
methods – Electromagnetic performance
___________
To be published.
TR 62153-4-1 © IEC:2007(E) – 9 –

3 List of symbols
a screening attenuation
s
a normalized screening attenuation with phase velocity difference not greater than 10 %
sn
and 150 Ω characteristic impedance of the injection line

c velocity of light
C through capacitance of the braided cable

T
CUT cable or component under test

E EMF
f frequency
f far end
f cut-off frequency
c
f far end cut-off frequency
cf
f near end cut-off frequency
cn
Φ the total flux of the magnetic field induced by the disturbing current I

1 1
Φ′ the direct leaking magnetic flux

Φ″ complete magnetic flux in the braid
I , U current and voltage in the primary circuit (feeding system)
1 1
I current coupled by the feed through capacitance to the secondary system (measuring
F
system)
ε relative permittivity of the injection line (feeding system)
r1
ε relative permittivity of the cable (measuring system)

r2
l cable length
L (external) inductance of the outer circuit
L (external) inductance of the inner circuit

M′ mutual inductance related to direct leakage of the magnetic flux Φ′

12 12
M″ mutual inductance related to the magnetic flux Φ″ (or ½ Φ″ ) in the braid

12 12 12
'
Φ ′′
Φ
' 12 1 12
M = and  M ′′ = ⋅
jω I 2 jω I
n near end
P sending power
P far end measured power
2f
P near end measured power
2n
T coupling transfer function
T far end transfer function
f
– 10 – TR 62153-4-1 © IEC:2007(E)

T near end transfer function
n
T = T
n,f n
f
U′ the disturbing voltage induced by Φ′

2 12
U″ the disturbing voltage induced by ½ Φ″ of the right hand lay contribution

rh 12
U″ the disturbing voltage induced by ½ Φ″ of the left hand lay contribution

lh 12
U″ is equal to U″ and U″ (= the disturbing voltage induced by ½ Φ″ )

2 rh lh 12
v phase velocity
v phase velocity of the "primary" system (feeding system)
v phase velocity of the "secondary" system (measuring system)
v relative phase velocity of the "primary" system (feeding system)
r1
v relative phase velocity of the "secondary" system (measuring system)
r2
Z characteristic impedance of the "primary" system (feeding system or line (1))
Z characteristic impedance of the cable under test (CUT) (measuring system or line (2))
Z terminating impedance of the line (1) in the far end

1f
Z terminating impedance of the line (2) in the near end

2n
Z terminating impedance of the line (2) in the far end (in a matched set-up

2f
Z = Z and Z = Z = Z )
1f 1 2n 2f 2
ZZ= Z
12 1 2
Z surface impedance of the braided cable
a
Z capacitive coupling impedance per unit length
F
Z capacitive coupling impedance
f
Z surface transfer impedance per unit length
T
Z transfer impedance of a tubular homogeneous screen per unit length
Th
Z surface transfer impedance
t
Z effective transfer impedance (= | Z + Z | ) per unit length in the near end
TEn F T
Z effective transfer impedance (= | Z – Z | ) per unit length in the far end
TEf F T
Z effective transfer impedance (= | Z ± Z | ) per unit length in the near end or in the far
,f
TEn F T
end
Z effective transfer impedance (= max | Z Z | ) per unit length
,
TE TEn TEf
Z effective transfer impedance (= max | Z ± Z | )

te f t
Z normalized effective transfer impedance of a cable (Z = 150 Ω and | v – v | / v ≤
ten 1 1 2 2
10 % velocity difference in relation to velocity of CUT
4 Electromagnetic phenomena
It is assumed that if an electromagnetic field is incident on a screened cable, there is only weak
coupling between the external field and that inside, and that the cable diameter is very small
compared with both the cable length and the wavelength of the incident field. The superposition
of the external incident field and the field scattered by the cable yields the total electromagnetic
field (E , H , in Figure 1). The total field at the screen's surface may be considered as the
t t
source of the coupling: the electric field penetrates through apertures by electric or capacitive
coupling; also magnetic fields penetrate through apertures by inductive or magnetic coupling.

TR 62153-4-1 © IEC:2007(E) – 11 –

Additionally, the induced current in the screen results in conductive or resistive coupling.

(E , H ) (E , H )
i i s s
E
t
n
H
t
σ
J
X
(E , H ) = (E , H ) + (E , H )
s s i i s s (1)
J = n ⋅ H
t (2)
σ = n ⋅ E ε ε
(3)
t 0 r
IEC  2152/07
Key
n unit vector normal to surface
Figure 1 – Incident (i), scattered (s) and resulting total electromagnetic fields (E , H )
t t
with induced surface current- and charge- densities J (A/m) and σ (C/m )
As the field at the surface of the screen is directly related to density of surface current and
surface charge, the coupling may be assigned either to the total field (E , H ) or to the surface
t t
current- and charge- densities (J and σ). Consequently, the coupling can be simulated into the
cable by reproducing through any means the surface currents and charges on the screen.
Because a cable of small diameter is assumed, higher modes can be neglected and an
additional coaxial conductor can be used as the injection structure, as shown in Figure 2.
Concept of a triaxial set-up
l
1) Outer circuit, formed by injection
+
cylinder and screen, characteristic
E
1 impedance Z ,
U
Z
1n
U
1f Z
1f
2) Inner circuit, formed by a screen,
and centre conductor, characteristic
Z U
2n
2n Z
(1) U 2f
2f
impedance Z ; screening at the ends
not shown.
D
(2) 1
Z
Z
IEC  2153/07
Conditions Z , Z , Z and λ are observed in Figure 3a and Figure 3b.
1f 2n 2f
NOTE 1 D << l.
NOTE 2 Both ends of circuit (2) must be well screened.
Figure 2 – Defining and measuring screening parameters – Triaxial set-up

– 12 – TR 62153-4-1 © IEC:2007(E)

5 Intrinsic screening parameters of short cables

The intrinsic parameters refer to an infinitesimal length of cable, like the inductance or

capacitance per unit length of transmission lines. Assuming electrically short cables, with l << λ

which will always apply at low frequencies, the intrinsic screening parameters are defined and

can be measured as follows:
5.1 Surface transfer impedance, Z
T
As shown in Figure 2 and Figure 3a (where Z and Z are zero):
1f 2f
Z = U / I ⋅ l ) (Ω/m) (4)
T 2 1
The dependence of Z on frequency is not simple and is often shown by plotting log Z against
T T
log frequency. Note that the phase of Z may have any value, depending on braid construction
T
and frequency range.
NOTE In circuit 2 of Figure 3a the voltmeter and short-circuit can be interchanged.
5.2 Capacitive coupling admittance, Y
c
As shown in Figure 2 and Figure 3b (where Z and Z are open circuit):
1f 2f
Y = jω C = I /()U ⋅ l (mho/m) (5)
C T 2 1
The through capacitance (C ) is a real capacitance and has usually a constant value up to
T
1 GHz and higher (with aperture a << λ).
While Z is independent of the characteristics of the coaxial circuits, C is dependent on those
T T
characteristics. There are two ways of overcoming this dependence:
a) The normalized through elastance K derived from C is independent of the size of the
T T
outer coaxial circuit, but it depends on its permittivity:
() ()
K = C / C ⋅C   (m/F)    K ~ 1/ ε + ε (6) (7)
T T 1 2 T r1 r 2
where C and C are the capacitance per unit length of the two coaxial circuits.
1 2
b) The capacitive coupling impedance Z again derived from C is also independent of the
F T
size of the outer coaxial circuit and, for practical values of ε , is only slightly dependent on
r1
its permittivity:
()()
Z = Z Z Y = Z Z jω C  (Ω/m)  Z ~ ε ⋅ ε / ε + ε (8) (9)
F 1 2 C 1 2 T F r1 r 2 r1 r 2
Compared with Z , Z is usually negligible, except for open weave braids. It may, however, be
T F
significant when Z and Z >> Z (audio circuits).
2n 2f 2
TR 62153-4-1 © IEC:2007(E) – 13 –

Injection cylinder
+
E
(1)
U
Z = 0
1f
Z ⋅ l
I T
Shield
U
T
(2)
V
U
Z = 0
2f
Z = ∞
2n Center conductor
l << λ
IEC  2154/07
Figure 3a – Equivalent circuit for the definition and possible testing of Z

Injection cylinder
+
E
(1)
U
Z = ∞
1f
Shield with apertures
(2)
C ⋅ l
T
A Z = 0
2n
Z = ∞
2f
I
Center conductor
Z ⋅ l = jωC ⋅ l
l << λ
T T
IEC  2155/07
Figure 3b – Equivalent circuit for the definition and possible testing of Y = j ωC
c T
Z
U
1 1
+
E
1 U U (x) Z , β U
1 1 1f (1)
1 1 Z
Z
T I (x)
C
T
(2)
Z Z , β U Z
U (x)
2 2 2 2f 2
U 2
2n
x
l
U l : arbitrary U
2f
2n
IEC  2156/07
NOTE Z and C are distributed (not correctly shown here). The loads Z at the ends may represent matched
T T 2
receivers.
Figure 3c – Definition of electrical quantities in a set-up that is matched at all ends
Figure 3 – Defining and measuring screen parameters – Equivalent circuits

– 14 – TR 62153-4-1 © IEC:2007(E)

5.3 Injecting with arbitrary cross-sections

A coaxial outer circuit has been assumed so far in this report, but it is not essential because of

the invariance of Z and Z . Using a wire in place of the outer cylinder, the injection circuit
T F
becomes two-wire with the return via the screen of the cable under test. Obviously the charge

and current distribution become non-uniform, but the results are equivalent to coaxial injection,
especially if two injection lines are used opposite to each other, and may be justified for worst-
case testing. Note that the IEC line injection test uses a wire.

5.4 Reciprocity and symmetry
Assuming linear shield materials, the measured Z and Z values will not change when
T F
interchanging injection (1) and measuring (2) circuits. Each of the two conductors of the two-
line circuit can be interchanged, but in practice the set-up will have to take into account
possible ground loops and coupling to the environment.
5.5 Arbitrary load conditions
When the circuit ends of Figure 3a and Figure 3b are not ideally short or open circuit, Z and
T
Z will act simultaneously. The superposition is noticeable in the low-frequency coupling of the
F
matched circuits (Figure 3c and Table 1).
6 Long cables – Coupled transmission lines
The coupling over the whole length of the cable is obtained by summing up (integrating) the
infinitesimal coupling contributions along the cable while observing the correct phase. The
analysis utilizes the following assumptions and conventions:
– matched circuits considered with the voltage waves U , U , U , see Figure 3c,
1 2n 2f
– representation of the coupling, using the normalized wave amplitudes U / Z[]Watt ,
instead of voltage waves, i.e. the coupling transfer function, in the following denoted by
"coupling function", will be defined as
U Z U Z
2 2
2n 2f
T = ,   T = (10) (11)
n f
U Z U Z
1 1
1 1
NOTE 1 is the ratio of the power waves travelling in circuits (2) and (1). Due to reciprocity and assuming
T
linear screen (shield) materials, T is reciprocal, i.e. invariant with respect to the interchange of injection and
measuring circuits (1) and (2).

NOTE 2 The quantity , or in logarithmic quantities
1/ T
, (12)
A = −20 log T
s 10
may be considered as the "screening attenuation" of the cable, specific to the set-up.
Performing the straight-forward calculations of coupled transmission line theory, the coupling
function, T, given in Table 1, is obtained. The term Slf is the "summing function" S being
{}
dependent on l and f. (The wavy bracket just indicates that the product l⋅ f is the argument
of the function S and not a factor to S). S represents the phase effect, when summing up the
infinitesimal couplings along the line, and is:
β l ±
sin
β l ±
⎧ ⎫
S {}l f = exp - j (13)
⎨ ⎬
n
l
β ±
⎩ ⎭
f
TR 62153-4-1 © IEC:2007(E) – 15 –

with
() { }
β l± = β ± β ⋅ l = 2πl f 1/ ν ± 1/ ν
2 1 2 1
(14a) (14b) (14c)
= 2πl f()ε ± ε / c
r 2 r 1
subscript ± refers to near/far end respectively

+ refers to both near/far ends

Note that weak coupling, i.e. T << 1, has been assumed. This case, including losses, is given
in [20 Halme, Szentkuti] .
NOTE 3 Equation (15) and representation in Table 1 visualizes the contributions of the different parameters to the
coupling function T:
1 l
T =()Z ± Z ⋅ ⋅ ⋅ S{}l ⋅ f ,ε ,ε (15)
n F T n r1 r2
Z ⋅ Z
f f
1 2
Note especially the following points:
a) There may be a directional effect (T ≠ T ) in the whole frequency range if Z is not
n f F
negligible. (But Z is usually negligible except with loose, single braid shields.)
F
b) Up to a constant factor, T is the quantity directly measured in a set-up.
c) For low frequencies, i.e. for short cables (l << λ), the trivial coupling formula is obtained
that is directly proportional to l :
1 l
T =()Z ± Z ⋅ ⋅ with Z = Z ⋅ Z (15) (16a) (16b)
12 1 2
n F T
Z 2
f
d) The summing function Sl⋅f is presented in Figure 4. Note also that:
{}
e) Sl⋅f has a sin(x)/x behaviour. A cut-off point may be defined as ()lf⋅ :
{}
C
c
()l ⋅ f = (17)
C
n
π ε ± ε
f r1 r2
f) The exact envelope of Sl⋅f is
{}
Env S{}l ⋅ f = (18)
n
f
()l ⋅ f
1+
()l ⋅ f
cn
f
___________
Figures in square brackets refer to the bibliography.

– 16 – TR 62153-4-1 © IEC:2007(E)

a
Table 1 – The coupling transfer function T (coupling function)

b
Set-up parameters
()Zl,,ε
11r
/\
--------------------- -----------------------

/ \
1 l
TZ=±()Z⋅ ⋅⋅Sl⋅f,εε,
{}
n FT n rr12
ZZ⋅
f 12 f
\ / \ /
----- -------- ----------------- -----------------
\/ \/
b
Intrinsic Cable parameters
screen parameters (,Zl),ε
22r
\ / \ /
---------------- ----------------- ----------- ------------
\/ \/
"Low-frequency coupling", "HF-effect",
c
short cables  cut-off ()lf⋅ .
C
\ /
-------------- ---------------
\/
Length + frequency effect
a
T is the power coupling from circuit (1) to circuit (2).
n
The stacked subscripts are associated to the stacked operation symbols ± in
f
the obvious way: upper subscript → upper operation, lower subscript → lower
operation.
b
ε and ε contained in S as parameters.
r1 r2
c
for l << λ: Sl f → 1 .
{}
g) The first minimum (zero) of Sl⋅f occurs at
{}
()l ⋅ f = π()l ⋅ f (19)
min C
h) As seen from Equations (13) and (18), below the cut-off points ()l ⋅ f is S{}l⋅≈f 1 and
cn
f
above them it starts to oscillate and its envelope drops asymptotically 20 dB/decade,
⎛ ⎞
cn
()l ⋅ f
⎜ ⎟
⎝ f ⎠
{}
Env S l ⋅ f = (20)
n
()l ⋅ f
f
TR 62153-4-1 © IEC:2007(E) – 17 –

l l
i) S is symmetrical in and f, i.e. and f are interchangeable. For a fixed length a cut-off

frequency f and vice versa, for a fixed frequency a cut-off length l may be defined.
c c
Substituting c/λ for f, we obtain the cut-off length as
o
λ
l = (21)
C
n
π ε ± ε
f
r1 r2
j) The effect of S in the frequency range (l = constant) is illustrated in Figure 5. The coupling
function is proportional to Z , only if f < f . Note also the typical values indicated for f .

T c c
k) The minima and maxima of S are not resonances but are due to cancelling and additive

effects of the coupling along the line.
l) The far end cut-off frequency is significantly influenced by the permittivity of the outer
system ()ε . In selecting ε → ε we obtain ()l ⋅ f → ∞, i.e. no cut-off at the far end.
r1 r1 r2 Cf
Due to practical aspects (tolerances, homogeneity, etc.), an ideal phase-matching
()ε ≡ ε is not feasible.
r1 r2
m) The total effect of l on the coupling is not contained in S alone, but in the product lS⋅⋅{}l f .
The product l × S is presented in Figure 7 for f = constant. The coupling function T, which
can be measured in a set-up, is proportional to l if l< l . However, for appropriately long
c
cables (l< l ), the maximum coupling is independent of l and a length of independent
c
()
shielding attenuation is obtained above the cut-off point l ⋅ f . But we should remember
C
()
that l ⋅ f as well as A are still dependent on the set-up parameters ()ε , Z .
r1 1
C s
S
Log scale
S
S f
n
(l ⋅ f) (l ⋅ f) (l ⋅ f) log(l ⋅ f)
cn min, n cf cn
IEC  2157/07
NOTE S >S above near end cut-off, yielding a directive effect.
f n
Key
(l × f ) cut-off point
c
{}
Figure 4 – Summing function S l ⋅ f for near (n) and far (f) end coupling

– 18 – TR 62153-4-1 © IEC:2007(E)

log ⏐Z ⏐
T
20 dB/dec.
log f
f
IEC  2158/07
Z()f = 10 MHz = 20 mΩ/m
T 1
Figure 5a – Transfer impedance of a typical single braid screen

l
log ⏐Z ⏐
T Z ⋅ ⋅
T
Z
Env (T )
f
T
f
Env (T )
n
T
n
log f
f f f
r cn cf
IEC  2159/07
Figure 5b – Coupling transfer function for the same cable with negligible Z (Z << Z ):
F F T
frequency responses of Figure 4 and Figure 5a added on log scale
NOTE The cut-off effect for f > f .
c
EXAMPLE: ε = 1 (set-up), ε = 2.2 (cable),
r1 r2
l = 1 m → f = 40 MHz, f = 200 MHz
Cn Cf
Figure 5 – The effect of the summing function

TR 62153-4-1 © IEC:2007(E) – 19 –

-40
T  [dB]
T
f
-60 T
fztdBk
T
n
Figure 6a – Calculated coupling transfer

functions T and T for a single braided when
n f
Z = 0
F
– In calculations the used parameters are:
-80
T
nztdBk
Z (d.c.) =15 mΩ/m and Z (10 MHz) = 20 mΩ/m
T T
increasing 20 dB/decade (see Figure 5a), cable
5 6 7 8 10
1⋅10 1⋅10 1⋅10 1⋅10 1⋅10 1⋅10
length 1 m, and velocities of the outer and inner
f
k
f   [Hz] line: v = 200 Mm/s and v = 280 Mm/s
1 2
corresponding a velocity difference of 40 %.
IEC  2160/07
-40
T  [dB]
T
fztdBk
T
f
T
fdBk
-60
Figure 6b – As Figure 6a but Im(Z ) is positive
T
and Z = +0,5*Im (Z ) at high frequencies:
T
n
F T
– T is 3,5 dB higher and T 6 dB lower than in
T n f
ndBk
reference Figure 6a because
-80
T ∼⎪Z + Z = 1,5*Z and
T
nztdBk
n F T ⎪ T
5 6 7 8 9 10 T ∼⎪Z – Z = 0,5*Z .
1⋅10 f F T ⎪ T
1⋅10 1⋅10 1⋅10 1⋅10 1⋅10
f  [Hz]
f
k
IEC  2161/07
-40
T  [dB]
Tf
T
fdBk
T
fztdBk
-60
Figure 6c – As Figure 6a but Im(Z ) is negative
T
T
nztdBk and Z = –0,5*Im(Z ) at high frequencies:
F T
T – T is 3,5 dB higher and T 6 dB lower than in
ndBk
f n
reference Figure 6a because
T
n
-80
T ∼⎪Z – Z ⎪= 1,5* ⎪Z ⎪ and
f F T T
5 6 7 8 9 10
1⋅10 1⋅10 1⋅10 1⋅10 1⋅10
1⋅10
T ∼⎪Z + Z ⎪= 0,5* ⎪Z ⎪
n F T T
f
k
f  [Hz]
IEC  2162/07
NOTE 1 T for near-end, T for far-end and dB means that T are calculated in dB ( 20 lg | T | ).
n f n,f n,f
NOTE 2 T dB: near-end when Z =()1 / 2 ⋅ Z and T dB: near-end when Z = 0.

n nzt F
F T
NOTE 3 T dB: far-end when Z =()1 / 2 ⋅ Z and T dB: far-end when Z = 0.

f fzt F
F T
Figure 6 – The effects of the Z and Z to the coupling transfer functions T and T
T F n f
– In Figure 6a, Z = 0.
F
– 20 – TR 62153-4-1 © IEC:2007(E)

()
– In Figure 6b and Figure 6c, Z is significant ( Z = 1 / 2 ⋅ Z ).
F
F T
– In Figure 6b Z is positive and Figure 6c negative at high frequencies.
T
log ⏐l ⋅ S⏐
Env (l ⋅ S )
f
f
Env (l ⋅ S )
n
n
f = const.
log l
IEC  2163/07
NOTE 4 For l >l , the maximum value of T is attained, i.e. the maximum coupling (or the screening attenuation) is
c
not dependent on l .
NOTE 5 l strongly depends on ε .
cf r1
Figure 7 – l ×S: complete length dependent factor in the coupling function T
(see Table 1)
7 Transfer impedance of a braided-wire outer conductor or screen
Typical transfer impedances of cables with braided-wire screens are shown in Figure 8.
The constant Z value at the low-frequency end is equal to the DC resistance of the screen, the
T
20 dB/decade rise at the high-frequency end is due to the inductive coupling through
the screen and the dip at the middle frequencies is caused by eddy currents or skin effect of
the braid. Some braided cables may behave anomalously, having less than a 20 dB/decade
rise at high frequencies. By using an extrapolation of 20 dB/decade, this remains in most cases
on the conservative side. This extrapolation can be used up to several GHz.
An electrically short piece of braided coaxial cable (2) is considered to be placed in a triaxial

arrangement as in Figure 2.
It is assumed that the outer circuit (1) is the disturbing one. As stated a braided cable has a
transfer impedance Z that increases proportionally to frequency
...