EN 50289-1-6:2002

SLOVENSKI STANDARD
01-september-2002
Communication cables - Specifications for test methods - Part 1-6: Electrical test
methods - Electromagnetic performance (Note: Applies in conjunction with EN
50289-1-1)
Communication cables - Specifications for test methods -- Part 1-6: Electrical test
methods - Electromagnetic performance
Kommunikationskabel - Spezifikationen für Prüfverfahren -- Teil 1-6: Elektrische
Prüfverfahren - Elektromagnetisches Verhalten
Câbles de communication - Spécifications des méthodes d'essai -- Partie 1-6: Méthodes
d'essais électriques - Performance électromagnétique
Ta slovenski standard je istoveten z: EN 50289-1-6:2002
ICS:
33.120.10 Koaksialni kabli. Valovodi Coaxial cables. Waveguides
33.120.20 äLFHLQVLPHWULþQLNDEOL Wires and symmetrical
cables
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 50289-1-6
NORME EUROPÉENNE
EUROPÄISCHE NORM March 2002
ICS 33.120.10
English version
Communication cables -
Specifications for test methods
Part 1-6: Electrical test methods -
Electromagnetic performance
Câbles de communication - Grundnorm für Kommunikationskabel -
Spécifications des méthodes d'essai Spezifikationen für Prüfverfahren
Partie 1-6: Méthodes d'essais électriques - Teil 1-6: Elektrische Prüfverfahren -
Performance électromagnétique Elektromagnetisches Verhalten
This European Standard was approved by CENELEC on 2000-11-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands,
Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2002 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 50289-1-6:2002 E
Foreword
This European Standard was prepared by the Technical Committee CENELEC TC 46X,
Communication cables.
The text of the draft was submitted to the formal vote and was approved by CENELEC as
EN 50289-1-6 on 2000-11-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2002-10-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2003-11-01
This European Standard has been prepared under the European Mandate M/212 given to
CENELEC by the European Commission and the European Free Trade Association.

- 3 - EN 50289-1-6:2002
Contents
1 Scope . 5
2 Normative references. 5
3 Definitions . 5
4 Survey of electromagnetic test methods . 6
4.1 General . 6
4.2 Transfer impedance Z and capacitive coupling impedance Z . 6
T F
4.3 Screening attenuation. 7
4.4 Normalised screening attenuation . 9
4.5 Coupling attenuation. 10
5 Theoretical background. 10
5.1 General . 10
5.2 Matched inner and outer circuit . 12
5.3 Matched inner and mismatched outer circuit. 13
6 Transfer impedance, triaxial method. 16
6.1 Introduction . 16
6.1.1 Inner and outer circuit . 16
6.1.2 Transfer impedance Z . 16
T
6.1.3 Coupling length. 16
6.2 Test method. 16
6.2.1 Equipment. 16
6.2.2 Test sample . 17
6.2.2.1 General . 17
6.2.2.2 Coaxial cables. 17
6.2.2.3 Screened symmetrical cables. 18
6.2.2.4 Screened multi-conductor cables . 18
6.2.3 Calibration procedure . 19
6.2.4 Test set-up. 19
6.2.4.1 General . 19
6.2.4.2 Impedance of inner system. 19
6.2.4.3 Impedance matching circuit . 20
6.2.5 Measuring procedure. 21
6.2.5.1 General . 21
6.2.5.2 Evaluation of test results. 21
6.3 Expression of test results. 22
6.3.1 Expression . 22
6.3.2 Temperature correction . 22
6.4 Test report . 22
6.5 Non-reference measurements (informative). 22
7 Transfer impedance, line injection method . 23
7.1 Introduction . 23
7.1.1 Inner and outer circuit . 23
7.1.2 Transfer impedance Z . 23
T
7.1.3 Sample length. 24
7.2 Test method. 24
7.2.1 Equipment. 24
7.2.2 Test sample . 25
7.2.2.1 Preparation of test sample. 25
7.2.3 Calibration. 25
7.2.4 Test set-up. 27
7.2.4.1 General . 27
7.2.4.2 Impedance of inner system. 27
7.2.4.3 Impedance matching circuit . 28

7.2.5 Measuring procedure. 29
7.2.6 Evaluation of test results. 30
7.3 Expression of test results. 31
7.3.1 Expression . 31
7.3.2 Temperature correction . 31
7.4 Test report . 31
8 Screening attenuation test method, triaxial method. 31
8.1 Introduction . 31
8.1.1 Inner and outer circuit . 31
8.1.2 Screening attenuation. 32
8.1.3 Related lengths. 32
8.2 Test method. 33
8.2.1 Equipment. 33
8.2.2 Test sample . 33
8.2.2.1 General . 33
8.2.2.2 Coaxial cables. 33
8.2.2.3 Screened symmetrical cables. 34
8.2.2.4 Screened multi-conductor cables . 34
8.2.3 Calibration procedure . 34
8.2.4 Test set-up. 35
8.2.4.1 General . 35
8.2.4.2 Impedance of inner system. 35
8.2.4.3 Impedance matching circuit . 36
8.2.5 Measuring procedure. 37
8.2.6 Evaluation of test results. 38
8.3 Expression of test results. 39
8.3.1 Expression . 39
8.3.2 Temperature correction . 40
8.4 Test report . 40
9 Coupling attenuation or screening attenuation, absorbing clamp method. 40
9.1 Introduction . 40
9.1.1 Coupling Attenuation or Screening attenuation . 40
9.2 Test method. 40
9.2.1 Equipment. 40
9.2.1.1 General . 40
9.2.1.2 Balun requirements. 42
9.2.2 Test sample . 43
9.2.2.1 Tested cable length. 43
9.2.2.2 Preparation of test sample. 43
9.2.3 Calibration procedure . 44
9.2.3.1 Attenuation of the measuring set-up. 44
9.2.3.2 Insertion loss of the absorbers. 47
9.2.4 Test set-up. 48
9.2.5 Test set-up verification. 50
9.2.5.1 Determination of measurement sensitivity of the set-up. 50
9.2.5.2 Verification of test set-up calibration. 50
9.2.5.3 Pulling force on cable. 50
9.2.6 Measuring procedure. 50
9.3 Expression of test results. 51
9.3.1 Expression . 51
9.4 Test report . 52
9.4.1 General . 52
9.4.2 Evaluation of test results (informative). 52
9.4.3 Examples . 53

- 5 - EN 50289-1-6:2002
1 Scope
This EN 50289-1-6 details four different test methods to determine the electromagnetic
performance characteristics of cables used in analogue and digital communication systems. The
four methods are detailed in clauses 6 to 9.
This document discusses test methods aiming to facilitate a selection of the applicable
electromagnetic test method.
It is to be read in conjunction with Part 1-1 of EN 50289, which contains essential provisions for its
application.
2 Normative references
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of
any of these publications apply to this European Standard only when incorporated in it by
amendment or revision. For undated references the latest edition of the publication referred to
applies (including amendments).
EN 50289-1-1 2001 Communication cables - Specifications for tests methods -
Part 1-1: Electrical test methods - General requirements
EN 50289-1-9 2001 Communication cables - Specifications for tests methods -
Part 1-9: Electrical test methods - Unbalance attenuation
(longitudinal conversion loss, longitudinal conversion
transfer loss)
1)
EN 50290-1-2 Communication cables - Part 1-2: Definitions
IEC 61196-1 1995 Radio-frequency cables
Part 1: Generic specification - General, definitions,
requirements and test methods
CISPR 16-1 1993 Specification for radio disturbance and immunity measuring
+ A1 1997 apparatus and methods
Part 1: Radio disturbance and immunity measuring
apparatus
ITU-T Recommendation 1988 Series O - Specifications of measuring equipment -
O.9 General - O.9: Measuring arrangements to assess the
degree of unbalance about earth
ITU-T Recommendation 1996 Series G - Transmission systems and media, digital
G.117 systems and networks - International telephone connections
and circuits - General recommendations on the
transmission
3 Definitions
For the purposes of this European Standard, the definitions of EN 50290-1-2 apply.

1)
At draft stage.
4 Survey of electromagnetic test methods
4.1 General
The electromagnetic performance of unbalanced cables (e.g. coaxial RF-cables) is determined
only by the quality of the screen. In the case of balanced cables the electromagnetic performance
is determined by the combined result of both unbalance attenuation and the effect of screen(s), if
any.
The quality of the screen may be evaluated by the measurement of transfer impedance (clauses 6
and 7) or screening attenuation (clauses 8 and 9). The combined result of the unbalance
attenuation and the screening attenuation (if applicable) may be evaluated using the coupling
attenuation test method (clause 9).
4.2 Transfer impedance Z and capacitive coupling impedance Z
T F
Two important properties in characterising screening effectiveness of cables are transfer
impedance Z and capacitive coupling admittance Y respectively capacitive coupling impedance
T C
Z . These properties can be used to calculate the normalised screening attenuation in dB
F
(see 4.4)
The transfer impedance Z of an electrically short uniform cable is defined as the quotient of the
T
longitudinal voltage induced in the outer circuit (environment) to the current in the inner circuit
(cable) or vice versa, related to unit length (see IEC 61196-1, 12.1.2.1).
U
Z = (1)
T
IL⋅
where
L coupling length
U
I
Figure 1 - Definition of transfer impedance Z
T
The capacitive coupling admittance Y of an electrically short uniform cable is defined as the
C
quotient of the current in the inner circuit caused by the capacitive coupling to the voltage in the
outer circuit, related to unit length (see IEC 61196-1, 12.1.2.1).
I
Y = =jCω (2)
C T
UL⋅
where
C through capacitance
T
L coupling length
U
CT
I
Figure 2 - Definition of coupling admittance

- 7 - EN 50289-1-6:2002
The through capacitance C and thus the capacitive coupling admittance Y are dependent on the
T C
permittivity and geometry of the outer circuit. In order to have a quantity which is invariant on the
permittivity and the geometry of the outer circuit and is also comparable to the transfer impedance
Z we introduce the capacitive coupling impedance Z .
T F
ZZ=⋅Z⋅Y (3)
F1 2 C
where
Z characteristic impedance of inner circuit
Z characteristic impedance of outer circuit
Y capacitive coupling admittance
C
If there are no holes in the screen C and Z are zero. This is the case for a foil and for double
T F
braided screen construction. But in a single braided construction Z and Z are about the same
T F
and Z must be taken into consideration.
F
With electrically short cables, where wave propagation can be neglected, the transfer impedance
can be simply obtained as measuring current and voltage.
Therefore the transfer impedance is a suitable criteria to describe the screening effectiveness of
electrically short uniform cables.
IEC 61196-1 contains two methods - the triaxial and line injection methods - describing how to
measure the transfer impedance of coaxial RF-cables. Clauses 6 and 7 of this standard extend
these methods for symmetrical and multi conductor cables as well. In addition this standard
provides guidance on impedance matching circuits to be used if the cable impedance is different
from the impedance of the test equipment.
The triaxial method only allows measurements at low frequencies (max. 100 MHz) while the line
injection method applies for higher frequencies.
4.3 Screening attenuation
With electrically short cables, where wave propagation can be neglected, the screening quantities
related to unit length can be obtained as measurement values and directly used to calculate an
induced disturbing voltage. In the higher frequency range the transmission characteristics are
dependent on the impedance and admittance per unit length as well as on the terminating
resistors.
The screening attenuation is a suitable criteria to describe the screening effectiveness of
electrically long cables. The screening attenuation is defined as the logarithmic ratio of the power
fed into the cable and the radiated maximum peak power:
P
feed
a =⋅10 log (4)
s 10
P
rad,max
For electrically long cables - in a frequency range where the transfer impedance of the cable
screen is proportional to frequency - the screening attenuation is length and frequency
independent.
The screening attenuation is related to the transfer impedance in one of the following ways:
a) for a matched outer circuit (cable environment) for example in the absorbing clamp method
(see clause 9 or IEC 61196-1, 12.4);
� �
ω⋅⋅ZZ
� �
a =⋅20 log ⋅±εε (5)
s,matched 10� rr12 �
far end
cZ⋅
� �
TE
near end
� �
Z = max Z ± Z (6)
TE F T
where
“+“ applies for the near end
“-“ applies for the far end
Z transfer impedance
T
Z capacitive coupling impedance
F
Z effective transfer impedance when the capacitive coupling is present (single braided screen)
TE
or
b) for a mismatched outer circuit (cable environment) - with a short circuit at the near end - for
example in the shielded screening attenuation method (see clause 8 or IEC 61196-1, 12.6):
� �
c
ZZ− Z +Z
� �
TF TF
(7)
a =⋅− 20 log ⋅ +
� �
s, mismatched
ωεZZ⋅ 2 −εε +ε
� �
12 r1 r2 r1 r2
� �
Respectively neglecting of the capacitive coupling
� �
ωε⋅⋅ZZ −ε
� �
12 r1 r2
a2=⋅0log ⋅ (8)
s, mismatched 10� �
cZ⋅
2ε
� �
T
r1
� �
In many cases the capacitive coupling can be neglected. In this case also the near end coupling in
a matched outer circuit can be neglected (equation 5). Then the difference between these
equations is:
� �
ε
r 2
� �
Δa = a − a ≈ 20 ⋅ log 1+ − 4dB (9)
s s, mismatched s, matched 10
far end
� �
ε
r1
� �
for ε = 1,6 and ε = 1,1 this difference is Δa ≈ 1,5 dB.
r1 r2 s
where
Z transfer impedance of cable screen
T
Z characteristic impedance of cable (inner circuit)
Z characteristic impedance of outer circuit (environment)
.
m/s
c velocity of light, 3 10
ε resulting relative permittivity of the dielectric of the cable
r1
ε resulting relative permittivity of the environment
r2
- 9 - EN 50289-1-6:2002
4.4 Normalised screening attenuation
The screening attenuation is highly dependent on the velocity difference between the inner and
outer circuit. Therefore the test results of the screening attenuation may also be presented in
normalised conditions. The normalised conditions are Δv/v = 10% or εε = 11, and Z
1 2
rr12,n
becomes the normalised impedance Z = 150 Ω.
s
The difference between the normalised screening attenuation and the measured screening
attenuation is calculated by:
aa=+Δa (10)
sn, s
where
a is the normalised screening attenuation
s,n
ωε⋅⋅ZZ⋅ −ε
11S rr2,n
a =⋅20 log (11)
sn 10
,
Zc⋅
TE
ω ⋅ Z ⋅150 ⋅ ⋅ ε
1 r1
a = 20 ⋅ log (12)
s,n 10
Z ⋅ c
TE
� �
� �
� 11 �
Δa=⋅20 log 2⋅ (13)
� �
ε
rt2,
� 1 − �
ε
� �
r1
where
a normalised screening attenuation
s,n
a measured screening attenuation
s
ε relative dielectric permittivity of the cable under test
r1
ε relative dielectric permittivity of the outer circuit (tube) during the measurement
r2,t
(equals 1,1)
Z equivalent transfer impedance of the cable under test
TE
Z normalised value of the characteristic impedance of the outer circuit of the cable
s
under test, Z = 150 Ω
s
ε normalised value of the relative dielectric permittivity of the environment of the cable
r2,n
Z characteristic impedance of the cable under test
Therefore we have for both solid PE and foamed PE dielectric of the cable (with ε ≈ 2,3
r1
respectively ε ≈ 1,6):
r1
Δa ≈ - 10 dB
The equations (8) and (9) shall be taken to calculate the normalised screening attenuation with a
measured transfer impedance.
4.5 Coupling attenuation
The cable (for unbalanced cables) or one cable pair (for symmetrical cables) is fed with the power
P . Due to the electromagnetic coupling between the cable or pair and the environment surface
waves are exited which propagate in both directions along the screen surface (or the cable surface
waves where there is not a screen). A surface current transformer is used for picking up the power
of the surface waves with an absorber (usually a ferrite tube) to suppress unwanted common
mode currents. These kinds of combinations are known as absorbing clamps. On the basis of the
peak values of the measured surface currents it is possible to calculate the maximum peak power,
P max, in the secondary system formed by the screen of the cable (or the cable itself) and the
environment.
The logarithmic ratio of the powers P and P max is termed coupling attenuation, expressed in
1 2
dB.
For unbalanced cables the coupling attenuation equals the screening attenuation. For symmetrical
cables the coupling attenuation is the combined result of both unbalance attenuation and
screening attenuation.
The surface current is measured on a swept-frequency basis with a stationary clamp.
Taking into account the effect of both near and far end surface waves, the coupling attenuation a
c
is specified by
� �
P
� �
a = 10 log (14)
c10
� �
maxP;P
[]2,n 2,f
� �
where
P input power of inner circuit of the sample
maximum near end coupling peak power
P
2,n
P maximum far end coupling peak power
2,f
The advantage of coupling attenuation measurements is that they can be directly used to give
information about EMC performance of both screened and unscreened cables.
5 Theoretical background
5.1 General
The three methods (clauses 6, 7 and 8) to measure the screening effectiveness of a cable screen
all have the same equivalent circuit.

- 11 - EN 50289-1-6:2002
R
gen
inner circuit
Z , ε , β
1 r1 1
U
1, n
R
1,f
Z ⋅l
T c
screen
R Y ⋅l R U
2,n C c 2,f 2, f
U
2, n
outer circuit
ε β
Z , ,
2 r2 2
Key
β phase constant of inner circuit
β phase constant of outer circuit
ε relative dielectric permittivity of the inner circuit
r1
relative dielectric permittivity of the outer circuit
ε
r2
L coupling length
c
M effective mutual inductance per unit length
T
'''
For braided screens MM=−M
T 12 12
where M’ relates to the direct leakage of the magnetic flux and M’’ relates to the
12 12
magnetic flux in the braid
R output resistance of generator
gen
R load resistance of inner circuit at the far end
1, f
load resistance of outer circuit at the far end
R
2, f
R load resistance of outer circuit at the near end
2, n
R screen resistance per unit length
T
U voltage fed into the inner circuit at the near end
1, n
U voltage coupled into the outer circuit at the far end
2, f
U voltage coupled into the outer circuit at the near end
2, n
Y capacitive transfer admittance per unit length =jCω
C
T
Z capacitive coupling impedance per unit length =ZZ Y
F
12 C
Z characteristic impedance of the inner circuit
Z characteristic impedance of the outer circuit
Z transfer impedance per unit length
T =+RjωM
TT
Figure 3 - Definitions
5.2 Matched inner and outer circuit
In the line injection method (clause 7) both the inner and outer circuit are matched (Z = R = R ;
1 gen 1,f
Z = R = R ). In that case the coupling through the cable screen, if feedback from the
2 2,n 2,f
secondary to the primary circuit and the losses are negligible, can be calculated by:
U
2,n
ZZ±
f
FT
= LS⋅ (15)
cn
U 2Z
11,n f
−+jββ .L
( )
12 c
1 − e
S = (16)
n
jL()ββ+.
12 c
−−jββ .L
( )
12 c
1 − e
−jβ .L
2 c
S = e (17)
f
jL()ββ−.
12 c
�ββ± .L �
( )
12 c
2 sin� �
� �
S = (18)
n
()ββ±.L
12 c
f
LL2π⋅⋅f
βπ⋅=L 2⋅ε⋅ = (19)
r
λ c
The first factor in equation (15) relates to the screen parameter and the summing function S to the
set-up parameter. Figure 4 shows an example for the summing function S.
|S| log scale
S
f
S
n
log scale
f .L
f .L cf c
cn c
Figure 4 - Calculated summing function S

- 13 - EN 50289-1-6:2002
For high frequencies the asymptotic value becomes
S → (20)
n
()ββ±.L
12 c
f
And for low frequencies the summing function becomes
S → 1 (21)
n
f
The point of intersection between the asymptotic values for low and high frequencies is the so-
called cut-off frequency f :
c
c
fL⋅= (22)
cn, c
πε⋅± ε
f
rr12
With equation (22) we have the condition for electrical short or long cables.
The cable is electrical short if
c
fL⋅≤ (23)
n c
πε⋅± ε
f
rr12
or electrical long if
c
fL⋅≥ (24)
n c
πε⋅± ε
f
rr12
The frequencies where the periodic maxima of S occur are given by
(12+⋅mc)
fL⋅= (25)
max ima,n c
2⋅±εε
f
rr12
where m is an integer.
5.3 Matched inner and mismatched outer circuit
In the triaxial methods (clauses 6 and 8) the inner circuit is matched (Z = R = R ) and the
1 gen 1,f
outer circuit is mismatched ( R = 0, Z ≠ R ). In this case the coupling through the cable screen,
2,n 2 2,f
if feedback from the secondary to the primary circuit and the losses are negligible, can be
calculated by:
U
ZZ− ZZ+
2,f
TF−−jϕϕTF j
≈ ⋅−11e + ⋅− e ⋅ ⋅
[] []
U ω ⋅ Z
εε− εε+
1,n 1
rr12 rr1 2
(26)
c
−jϕ
21+−ZR/ ⋅1−e
( )
22,f ( )
ϕπ=−2 ε ε L /λ
( )
11rr2c0
ϕπ=+2 ε ε L /λ (27)
21(rr2 )c0
ϕϕ=−ϕ= 4πε L /λ
32 1 rc2 0
i.e. formally  A + B ⋅C⋅D, where AC is the far end crosstalk, BC is the reflected near end
crosstalk and D is the mismatch factor.
Total oscillations of D are
< 2 dB, if   1 < Z / R < 1,25
2 2,f
3 dB,   if   Z / R = 1,4
2,f
but 10 dB and more, if Z /R >3
2 2,f
The functional equation (Figure 5)
−jϕ ϕ
12−=e sin with ϕ = ϕ , ϕ , ϕ (28)
1 2 3
shows, that the equation of the voltage ratio contains three periodic partial functions of the ratio
to wave length λ :
coupling length L
c 0
− jϕ
1 − e
ϕ3
ϕ
2 ϕ
0 1 2 3 4 5
l/λ
Figure 5 - Calculated periodic functions for ε = 2,3 and ε = 1,1
r,1 r2
An example of the theoretical curve of the voltage ratio is shown in Figure 6 and Figure 7. Figure 6
with a logarithmic scale to extend the lower frequency range and Figure 7 with a linear scale up to
very high frequencies.
- 15 - EN 50289-1-6:2002
U
20⋅ log in dB
U
0.01 0.1 1 10 100
f/MHz
Figure 6 - Calculated voltage ratio using a logarithmic scale
U
20 ⋅ log in dB
U
0 500 1000 1500 2000 2500 3000
f/MHz
Figure 7 - Calculated voltage ratio using a linear scale
From equation (26) we obtain periodic maximum values of the voltage ratio, which are
independent of the load resistor R - provided that R ≤ Z - and of coupling cable length L .
2,f 2,f 2 c
U c
ZZ− Z +Z
2,f
TF TF
≈⋅ + (29)
U ω Z
εε− εε+
11,n r1 r2 r1 r2
max
In Figures 4, 6 and 7 the envelope rise is reached with the first maximum of the wide period at
c
fL⋅≥ (30)
c
2⋅−εε
rr12
In this frequency range Z can be calculated if Z is negligible
T F
ωε⋅⋅Z −ε U
11rr2 2,f
Z ≈ ⋅ (31)
T
U
2⋅⋅c ε
1,n
r1
max
For low frequencies, when L << λ and, consequently, sinϕ ≈ ϕ, equation (26) changes into
c 0
U
ZL⋅
2,f
Tc
= (32)
U Z
11,n
6 Transfer impedance, triaxial method
6.1 Introduction
6.1.1 Inner and outer circuit
The inner circuit (cable under test) is fed and indicated by the subscript 1. The subscript 2 denotes
the outer circuit, which consists of the screen surface and the triaxial tube.
6.1.2 Transfer impedance Z
T
The transfer impedance, Z of an electrically short uniform cable is defined as the quotient of the
T
longitudinal voltage induced in the outer circuit - formed by the screen under test and the
measuring tube - to the current in the inner circuit or vice versa related to unit length.
6.1.3 Coupling length
The coupling length depends on the highest frequency to be measured
50 ⋅10
L ≤ (33)
c,max
ε ⋅ f
r1 max
The minimum coupling length shall be 0,3 m.
The highest frequency to be measured is given by the shortest permissible coupling length
L = 0,3 m:
c,min
167 ⋅10
f ≤ (34)
max
ε
r1
where
L maximum coupling length in m
c,max
f highest frequency in Hz
max
ε resulting relative permittivity of the dielectric of cable
r1
The condition means that the phase constant of the cable multiplied with the length is less than 1.
Commonly a tube of 1 m is suitable for frequencies up to 30 MHz and a tube of 0,3 m is suitable
up to 100 MHz.
6.2 Test method
6.2.1 Equipment
The measurements can be performed using a network analyser or alternatively discrete signal
generator and selective measuring receiver.
The measuring equipment is shown in 6.2.4 Figure 11 and consists of
a) a network analyser or alternatively
• signal generator with the same characteristic impedance as the quasi -coaxial system of
the cable under test or with an impedance adapter and complemented with a power
amplifier if necessary for very low transfer impedance,

- 17 - EN 50289-1-6:2002
• receiver with a calibrated step attenuator and complemented with a low noise amplifier for
very low transfer impedance,
b) triaxial tube with terminations to cable screen and network analyser or receiver. The material of
the tube shall be well conductive and non ferromagnetic for example brass,
c) printing facility,
d) impedance matching circuit if necessary
primary side: Nominal impedance of generator
secondary side: Nominal impedance of cable under test (see 6.2.4.2)
return loss: > 10 dB.
6.2.2 Test sample
6.2.2.1 General
The test sample shall have a length not more than 50 % longer than the coupling length.
6.2.2.2 Coaxial cables
Coaxial cables are prepared as shown in Figure 8.
screen
XXXXXXXXXXXXXXXXXX
well screened load
R
connector
resistor R
XXXXXXXXXXXXXXXXXX
Figure 8 - Preparation of test sample (coaxial cable)
One end of the coaxial or quasi coaxial system is matched with a well screened resistor, R the
value of which is equal to the characteristic impedance of the system, Z . The other end is
prepared with a connector to make a connection to the generator. All connections shall be made
so that the RF-contact resistance can be neglected with respect to the results.
The test sample shall be fitted to the test set-up (see 6.2.4). The test set-up is an apparatus of a
triple coaxial form. The cable screen forms both the outer conductor of the inner system and the
inner conductor of the outer system. The outer conductor of the outer system is the tube with a

short circuit to the screen on the fed side of the cable (see Figure 9).

Figure 9 - Connection to the tube
The resistor R has a value of 150 Ω for a tube size of 55 mm inner diameter and cables with a
diameter of approximately 5 mm. For other sizes of tubes and cables with other diameters the
value of the resistor is calculated according to the formula:
d
o
R ≈⋅14,l60n − 50 (35)
d
c
where
d inner diameter of tube
o
d outer diameter of cable screen.
c
6.2.2.3 Screened symmetrical cables
Screened symmetrical cables are treated as a quasi coaxial system. Therefore the conductors of
all pairs shall be connected together at both ends. All screens, also those of individually screened
pairs or quads, shall be connected together at both ends. The screens shall be connected over the
whole circumference (see Figure 10).
screen
XXXXXXXXXXXXXXXXXX
well screened load
R
pairs/quads
connector
resistor R
XXXXXXXXXXXXXXXXXX
Figure 10 - Preparation of test sample (symmetrical and multi conductor cables)
6.2.2.4 Screened multi-conductor cables
Screened multi-conductor cables are prepared as symmetric cables (6.2.2.3).

- 19 - EN 50289-1-6:2002
6.2.3 Calibration procedure
The composite loss of the connecting cables shall be measured in a logarithmic frequency sweep
over the whole frequency range, which is specified for the transfer impedance. The calibration
data has to be saved, so that the results may be corrected.
U
Fc, al
a =⋅20 log (36)
cal 10
U
Rc, al
where
U voltage fed during calibration procedure
F,cal
U voltage at the receiver during calibration procedure
R,cal
6.2.4 Test set-up
6.2.4.1 General
A block diagram of the test set-up is shown in Figure 11.
Figure 11 - Test set-up
6.2.4.2 Impedance of inner system
If the impedance Z of the inner system (coaxial or quasi coaxial) is not known, it may be
determined by using this method:
One end of the prepared sample is connected to a network analyser, which is calibrated for
impedance measurements at the connector interface reference plane. The test frequency shall be
the approximate frequency for which the length of the sample is 1/8 λ, where λ is the wavelength.
c
f ≈ (37)
test
8.L ε
sample r1
where
f test frequency
test
.
c velocity of light, 3 10 m/s
L length of sample
sample
The sample is short circuited at the far end. The impedance Z is measured.
short
The sample is left open at the same point where it was shorted. The impedance Z is measured.
open
Z is calculated as
ZZ=⋅Z (38)
1 short open
6.2.4.3 Impedance matching circuit
6.2.4.3.1 General
If R is not 50 Ω then an impedance matching circuit is needed. It shall be implemented as a two
resistor circuit with one series resistor, R and one parallel resistor R . The value of the resistors
s p
and the configurations are shown in 6.2.4.3.2 and 6.2.4.3.3.
6.2.4.3.2 R < 50 Ω
If the impedance of the inner system, and subsequently R is less than 50 Ω the formulas below
are used.
R
R=−50 1 (39)
s
R
R = (40)
p
R
1 −
The configuration is depicted in Figure 12.
R
s
R side
50 Ω side
R
p
Figure 12 - Impedance matching for R < 50 Ω
The voltage gain k of the circuit is:
m
RR
1 p
k = (41)
m
RR++R R RR
11pps s
6.2.4.3.3 R > 50 Ω
If the impedance of the inner system, and subsequently R is greater than 50 Ω the formulas
below are used.
RR=−1 (42)
s 1
R
R = (43)
p
1 −
R
- 21 - EN 50289-1-6:2002
The configuration is depicted in Figure 13.
R
s
R side
50 Ω side
R
p
Figure 13 - Impedance matching for R >50 Ω
The voltage gain k of the circuit is:
m
R
k = (44)
m
RR+
s 1
6.2.5 Measuring procedure
6.2.5.1 Gen
...