SIST EN 50289-1-11:2017
(Main)Communication cables - Specifications for test methods - Part 1-11: Electrical test methods - Characteristic impedance, input impedance, return loss
Communication cables - Specifications for test methods - Part 1-11: Electrical test methods - Characteristic impedance, input impedance, return loss
This Part of EN 50289 details the test methods to determine characteristic impedance, input impedance and return loss of cables used in analogue and digital communication systems. It is to be read in conjunction with EN 50289-1-1, which contains essential provisions for its application.
Kommunikationskabel - Spezifikationen für Prüfverfahren - Teil 1-11: Elektrische Prüfverfahren - Wellenwiderstand, Eingangsimpedanz, Rückflußdämpfung
Dieser Teil EN 50289 beschreibt die Prüfverfahren zur Bestimmung des Wellenwiderstandes, der Eingangsimpedanz und der Rückflussdämpfung von fertiggestellten Kabeln, welche in analogen und digitalen Kommunikationssystemen eingesetzt werden.
Dieser Teil ist in Verbindung mit der EN 50289 1 1 zu lesen, in dem grundlegende Festlegungen zur Anwendung dieser Norm getroffen sind.
Câbles de communication - Spécifications des méthodes d'essai - Partie 1-11: Méthodes d'essais électriques - Impédance caractéristique, impédance d'entrée, affaiblissement de réflexion
Komunikacijski kabli - Specifikacije za preskusne metode - 1-11. del: Električne preskusne metode - Karakteristična impedanca, vhodna impedanca, povratne izgube
Ta del standarda EN 50289 podrobno navaja preskusne metode za ugotavljanje karakteristične impedance, vhodne impedance in povratne izgube kablov, ki se uporabljajo v analognih in digitalnih komunikacijskih sistemih.
Ta del standarda je treba brati v povezavi s standardom EN 50289-1-1, ki vključuje bistvene določbe za njegovo uporabo.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 50289-1-11:2017
01-februar-2017
1DGRPHãþD
SIST EN 50289-1-11:2002
.RPXQLNDFLMVNLNDEOL6SHFLILNDFLMH]DSUHVNXVQHPHWRGHGHO (OHNWULþQH
SUHVNXVQHPHWRGH.DUDNWHULVWLþQDLPSHGDQFDYKRGQDLPSHGDQFDSRYUDWQH
L]JXEH
Communication cables - Specifications for test methods - Part 1-11: Electrical test
methods - Characteristic impedance, input impedance, return loss
Kommunikationskabel - Spezifikationen für Prüfverfahren - Teil 1-11: Elektrische
Prüfverfahren - Wellenwiderstand, Eingangsimpedanz, Rückflußdämpfung
Câbles de communication - Spécifications des méthodes d'essai - Partie 1-11: Méthodes
d'essais électriques - Impédance caractéristique, impédance d'entrée, affaiblissement de
réflexion
Ta slovenski standard je istoveten z: EN 50289-1-11:2016
ICS:
33.120.20 äLFHLQVLPHWULþQLNDEOL Wires and symmetrical
cables
SIST EN 50289-1-11:2017 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 50289-1-11:2017
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SIST EN 50289-1-11:2017
EUROPEAN STANDARD
EN 50289-1-11
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2016
ICS 33.120.20 Supersedes EN 50289-1-11:2001
English Version
Communication cables - Specifications for test methods - Part
1-11: Electrical test methods - Characteristic impedance, input
impedance, return loss
Câbles de communication - Spécifications des méthodes Kommunikationskabel - Spezifikationen für Prüfverfahren -
d'essai - Partie 1-11: Méthodes d'essais électriques - Teil 1-11: Elektrische Prüfverfahren - Wellenwiderstand,
Impédance caractéristique, impédance d'entrée, Eingangsimpedanz, Rückflußdämpfung
affaiblissement de réflexion
This European Standard was approved by CENELEC on 2016-09-05. 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 CEN-CENELEC
Management Centre 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 CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2016 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN 50289-1-11:2016 E
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EN 50289-1-11:2016 (E)
Contents Page
European foreword . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Test method for mean characteristic impedance (S type measurement) . 10
21
4.1 Principle . 10
4.2 Expression of test results . 10
5 Test method for input impedance and return loss (S type measurement) . 10
11
5.1 Method A: measurement of balanced cables using balun setup . 10
5.1.1 Test Equipment . 10
5.1.2 Test sample . 11
5.1.3 Calibration procedure . 11
5.1.4 Measuring procedure . 12
5.2 Method B: measurement of balanced cables using balun-less setup . 12
5.2.1 Test Equipment . 12
5.2.2 Test sample . 13
5.2.3 Calibration procedure . 13
5.2.4 Measuring procedure . 13
5.3 Method C: measurement of coaxial cables . 14
5.3.1 Test Equipment . 14
5.3.2 Test sample . 14
5.3.3 Calibration procedure . 14
5.3.4 Measuring procedure . 15
5.4 Expression of test results . 15
6 Test report . 17
Annex A (normative) Function fitting of input impedance . 18
A.1 General . 18
A.2 Polynomial function for function fitting of input impedance . 18
A.3 Fewer terms . 19
Annex B (normative) Correction procedures for the measurement results of return loss and
input impedance . 21
B.1 General . 21
B.2 Parasitic inductance corrected return loss (PRL) . 21
B.3 Gated return loss (GRL) . 23
B.4 Fitted return loss (FRL) . 25
B.5 Comparison of gated return loss (GRL) with fitted return loss (FRL) . 31
2
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B.6 Influence of the correction technique on return loss peaks . 32
Annex C (normative) Termination loads for termination of conductor pairs . 35
C.1 General . 35
C.2 Verification of termination loads. 36
Bibliography . 37
3
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EN 50289-1-11:2016 (E)
European foreword
This document [EN 50289-1-11:2016] has been prepared by CLC/TC 46X "Communication cables".
The following dates are fixed:
• latest date by which this document has to be (dop) 2017-09-05
implemented at national level by publication of
an identical national standard or by
endorsement
• latest date by which the national standards (dow) 2019-09-05
conflicting with this document have to
be withdrawn
This document supersedes EN 50289-1-11:2001.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent rights.
4
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SIST EN 50289-1-11:2017
EN 50289-1-11:2016 (E)
1 Scope
This part of EN 50289 details the test methods to determine characteristic impedance, input impedance and
return loss of cables used in analogue and digital communication systems.
It is to be read in conjunction with EN 50289-1-1, which contains essential provisions for its application.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
EN 50289-1-1:2001, Communication cables - Specifications for test methods - Part 1-1: Electrical test
methods - General requirements
EN 50289-1-5:2001, Communication cables - Specifications for test methods - Part 1-5: Electrical test
methods - Capacitance
EN 50289-1-7:2001, Communication cables - Specifications for test methods - Part 1-7: Electrical test
methods - Velocity of propagation
EN 50290-1-2, Communication cables - Part 1-2: Definitions
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 50290-1-2 and the following apply.
3.1
characteristic impedance
Z
C
(wave) impedance at the input of a homogeneous line of infinite length. The characteristic impedance Z of a
c
cable is defined as the quotient of a voltage and current wave which are propagating in the same direction,
either forwards or backwards.
uu
fr
(1)
Z
C
ii
fr
where
Z is characteristic impedance;
c
u is voltage wave propagating in forward respectively reverse direction;
f,r
i is current wave propagating in forward respectively reverse direction.
f,r
5
= =
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EN 50289-1-11:2016 (E)
3.2
mean characteristic impedance
Z
cm
in practice for real cables which always have structural variations the characteristic impedance is described
by the mean characteristic impedance which is derived from the measurement of the velocity of propagation
(EN 50289-1-7) and the mutual capacitance (EN 50289-1-5). However, this method is only applicable for
frequencies above 1 MHz and non-polar insulation materials (i.e. materials having a dielectric permittivity
which doesn’t change over frequency). The mean characteristic impedance approaches at sufficiently high
frequencies (≈100 MHz) an asymptotic value Z
∞
The characteristic impedance may be expressed as the propagation coefficient divided by the shunt
admittance. This relationship holds at any frequency.
aβ+ j β a
(2)
Zj≈−
c
jCω 1− j tanδωC ωC
( )
where
is complex characteristic impedance (Ω);
Z
c
α is attenuation coefficient (Np/m) ;
β is phase constant (rad/m);
tanδ is loss factor;
ω -1
is circular frequency (s );
C is mutual capacitance (F/m).
At high frequencies, where the imaginary component of impedance is small, and the real component and
magnitude are substantially the same we get for the mean characteristic impedance
τ
β 1
p
(3)
Z ≈==
cm
ω ××C C vC
Where
Z is mean characteristic impedance (m);
cm
v is velocity of propagation (m/s);
τ is phase delay (s/m);
p
C is mutual capacitance (F/m).
3.3
terminated input impedance
Z
in
impedance measured at the near end (input) when the far end is terminated by a load resistance of value
equal to the system nominal impedance Z
R
6
=
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EN 50289-1-11:2016 (E)
3.4
open/short input impedance
Z
OS
impedance measured at the near end (input) when the far end is terminated with its own impedance. In
practice this is the case when the round trip attenuation is greater than 40 dB at any measured frequency.
This property takes into account structural variations in the cable. For samples with lower round trip loss it is
determined by the open/short circuit method:
Z ZZ× (4)
os open short
where
is input Impedance of the cable obtained from an open/short measurement;
Z
os
Z is impedance with an open circuit at the far end of the cable;
open
Z is impedance with a short circuit at the far end of the cable.
short
3.5
fitted characteristic impedance
Z
fit
is obtained from a least square error function fitting of the open/short input impedance. The fitting can be
applied on the magnitude, real and imaginary part of the input impedance. The fitted characteristic
impedance is an alternative to the mean characteristic impedance to describe the characteristic impedance. It
is only valid if the variations with frequency of the input impedance around its characteristic impedance are
balanced.
3.6
(operational) return loss
RL
(operational) return loss is measured at the near end (input) when the far end is terminated by a load
resistance of value equal to the system nominal impedance Z . It quantifies the reflected signal caused by
R
impedance variations. The (operational) return loss takes into account the structural variations along the
cable length and the mismatch between the reference impedance and the (mean) characteristic impedance
of the cable (pair). If the (mean) characteristic impedance of the cable (pair) is different from the reference
impedance, one gets, especially at lower frequencies (where the round trip attenuation is low), multiple
reflections that are overlaid to the structural and junction reflections. Therefore, return loss RL is also
referenced as operational return loss.
As an example, Figure 1, shows the operational return loss under different conditions. The blue line shows
the return loss of a pair having a characteristic impedance equal to the reference impedance but taking into
account that the impedance is varying with frequency (see right-hand graph). The red line shows the return
loss of a pair having a characteristic impedance that is different from the reference impedance (110 Ω vs. 100
Ω). For both lines, periodic variations – that are caused by multiple reflections between the junctions at the
near and far end – are observed. The green line shows a simulation of a pair having a frequency independent
characteristic impedance which is equal to the reference impedance.
7
=
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EN 50289-1-11:2016 (E)
frequency dependent factor of the characteristic impedance
Return Loss
1,2 0,2
0
RLRL w/o mismatch
1,16 0,16
5 RLRL w mismatch
RLRL w /o mismatch; ZZcc frequency independent
1,12 0,12
10
1,08 0,08
15
1,04 0,04
20
1 0
25 Real
Imag
0,96 -0,04
30
0,92 -0,08
35
0,88 -0,12
40
0,84 -0,16
45
0,8 -0,2
0,1 1 10 100
50
0,1 1 10 100 MHz
MHz
Figure 1 — Return loss with and without junction reflections
3.7
open/short return loss
OSRL
way to avoid in the measurement of return loss multiple reflections due to a mismatch between the
characteristic impedance (asymptotic value at high frequencies) of the CUT and the reference impedance is
to use a CUT terminated in its nominal impedance and having a very long test length such that the round trip
attenuation of the CUT is at least 40 dB at the lowest frequency to be measured. For standard LAN cables,
this would result in a CUT length of roughly 1 000 m for the lowest frequency of 1 MHz.
Another way (when long CUT length is not available) is to measure the characteristic impedance (open/short
method) and to calculate the return loss. As the characteristic impedance is obtained from the measurement
of the open and short circuit impedance, it is proposed to name such obtained return loss open/short return
loss.
This open/short return loss includes the effect of structural variations and the mismatch at the near end
(including the effect due to a frequency-dependent characteristic impedance), but it does not take into
account multiple reflections.
Figure 2 shows the difference between operational return loss and open/short return loss. The left-hand
graph shows the results of a pair having a characteristic impedance which is different from the reference
impedance (110 Ω vs. 100 Ω). The right-hand graph shows the results of a pair having a characteristic
impedance which is equal to the reference impedance (100 Ω). One may recognize that the open/short return
loss does not take into account multiple reflections.
Return Loss Return Loss
0 0
RLRL w mismatch RLRL w /o mismatch
5 5
OSOSRLRL w/o mismatch
OSOSRLRL w mismatch
10 10
15 15
20 20
25 25
30 30
35 35
40 40
45 45
50 50
0,1 1 10 100 0,1 1 10 100
MHz MHz
Figure 2 — Return loss and open/short return loss
8
dB
dB
dB
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EN 50289-1-11:2016 (E)
3.8
structural return loss
SRL
The structural return loss is the return loss where only structural variations along the cable are taken into
account. The mismatch effects at the input and output of the transmission line (including the effect due to a
frequency-dependent characteristic impedance) have been eliminated. The structural return loss cannot be
measured directly but is calculated from the measurement of the characteristic impedance (open/short
method).
ZZ−
OS fit
SRL 20× lg (5)
ZZ+
fit
OS
where
Z is the (complex) input impedance obtained from the measurement of the open and short
OS
circuit impedance;
Z is the (complex) characteristic impedance obtained from a curve fitting of the real and
fit
imaginary part of ZOS.
The left-hand graph of Figure 3 shows the operational return loss, open/short return loss and structural return
loss of a CUT having a characteristic impedance of 110 Ω. A difference between both is observable. The
operational return loss takes into account all effects (structural variations, mismatch effects at the input and
output). The open/short return loss does not take into account mismatch effects at the output (i.e. no multiple
reflections). Whereas the structural return loss only takes into account structural variations along the cable.
The right-hand graph shows the real and imaginary part of the mean characteristic impedance (obtained from
the measurement of the open and short circuit impedance) and it’s fitting.
Return Loss Mean Characteristic Impedance
0 140 80
RLRL
OSOSRLRL 130 70
10
SSRLRL
120 60
20
110 50
30
100 40
Re(Zos)
fitted Re(Zos)
40 90 30
Im(Zos)
fitted Im(Zos)
80 20
50
70 10
60
60 0
70
50 -10
80 40 -20
0,1 1 10 100
0,1 1 10 100
MHz MHz
Figure 3 — Return loss, open short return loss and structural return loss
3.9
parasitic inductance corrected return loss
PRL
return loss where the effect a parasitic inductance (due to sample preparation and/or test fixture), which is
observed as an increase of the input impedance at high frequencies (above 100 Mhz), has been corrected
9
dB
Real Part [Ohm]
Imaginary Part [Ohm]
=
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EN 50289-1-11:2016 (E)
3.10
gated return loss
GRL
return loss where the effect of the test fixtures and sample preparation, which is observed as an increase of
the input impedance at high frequencies (above 100 MHz), has been corrected by a gating function
3.11
fitted return loss
FRL
return loss where the effect of the test fixtures and sample preparation, which is observed as an increase of
the input impedance at high frequencies (above 100 MHz), has been corrected by applying fitting function on
the input impedance
4 Test method for mean characteristic impedance (S type measurement)
21
4.1 Principle
This method shall only be applied for cables having non-polar insulation materials (e.g. PE, PTFE), i.e.
materials having a dielectric permittivity which doesn’t change over frequency. Or in other words this method
shall only be applied to cables having a mutual capacitance which doesn’t change over frequency.
The mean characteristic impedance shall be derived from the measurement of the velocity of propagation,
respectively phase delay, according to EN 50289-1-7 and the mutual capacitance according EN 50289-1-5.
The measurement shall be carried out at frequencies above 100 MHz where the phase delay approaches an
asymptotic value.
4.2 Expression of test results
The mean characteristic impedance Z shall be derived from Formula (6):
cm
τ
1
p
(6)
Z
cm
C vC×
where
Z is mean characteristic impedance (Ω);
cm
v is velocity of propagation (m/s), measured according EN 50289-1-7;
is phase delay (s/m), measured according EN 50289-1-7;
τ
p
C is mutual capacitance (F/m), measured according EN 50289-1-5.
5 Test method for input impedance and return loss (S type measurement)
11
5.1 Method A: measurement of balanced cables using balun setup
5.1.1 Test Equipment
The test equipment consists of a 2-port vector network analyser (VNA) with:
— S-parameter set-up;
10
= =
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EN 50289-1-11:2016 (E)
— Balun to convert the unbalanced signal of the VNA to a balanced signal. The balun shall have an
impedance on the primary (unbalanced) side equal to the nominal impedance of the measuring devices
(in general 50 Ω) and on the secondary (balanced) side equal to the nominal impedance of the CUT (e.g.
100 Ω) (the balun shall fulfil the requirements of Class A baluns as described in EN 50289-1-1);
— To perform a calibration of the test equipment (on the secondary side of the balun), a short circuit, an
open circuit and a reference load are required. The short circuit shall have negligible inductance and the
open circuit shall have negligible capacitance. The load resistor shall have a value close (within 1%) to
the nominal impedance of the CUT (e.g. 100 Ω) and with negligible inductance and capacitance;
— For the measurement of the input impedance and (operational) return loss a T-resistor network (see
Figure 4) is required to terminate the common and differential mode impedance at the far end of the
sample. The differential mode termination resistors shall be matched in pairs, each half the value of the
differential mode reference impedance Z (in general 100 Ω). If not specified otherwise, for example by
R
particular cabling standards, the common mode termination resistors shall be:
— 0 Ω for individually screened pair cables;
— 25 Ω for overall screened cables;
— 45 Ω to 50 Ω for unscreened cables.
Key
DM
R differential mode termination resistor
term
CM
R common mode termination resistor
term
Figure 4 — T-resistor network
5.1.2 Test sample
The CUT shall have or exceed the minimum length specified in the relevant sectional specification. Both ends
of the CUT shall be prepared, such that when connected to the terminals of the test equipment the influence
to the test result is minimised. The twisting of the pairs/quads shall be maintained.
5.1.3 Calibration procedure
It is not the intent of the standard to detail the algorithms applied by a VNA to correct the measured results
based on a calibration procedure but to detail the calibration procedure. Further information may be obtained
in the manuals of the VNA supplier.
The calibration shall be performed on the secondary side of the balun by applying consecutively an open,
short and load standard (see Figure 5).
11
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EN 50289-1-11:2016 (E)
Ri
open
reflection
Generator
bridge
short
Ri
Receiver
load
Figure 5 — Calibration set-up
5.1.4 Measuring procedure
The test sample shall be connected to the terminals of the test fixture. The scattering parameter S – i.e. the
xx
reflection coefficient Γ (in Formulae (9) to (13)) – shall be measured over the whole specified frequency range
and at the same frequency points as for the calibration procedure. The values shall be measured as complex
parameters. All pairs/quads shall be measured from both ends unless otherwise specified.
a) terminated input impedance (Z ) and (operational) return loss (RL)
in
Measure the scattering parameter S – i.e. the reflection coefficient Γ – of the CUT with the far end
xx
terminated by a load resistance as described in 4.1.1. Inactive pairs shall also be terminated by this T-
resistor network.
b) Open/short input impedance (Z ) and open/short return loss (OSRL)
OS
Measure consecutively the scattering parameter S – i.e. the reflection coefficient Γ – of the CUT with
xx
the far end in open and short circuit.
5.2 Method B: measurement of balanced cables using balun-less setup
5.2.1 Test Equipment
Method B is the preferred one for balanced cables for frequencies above 1 000 MHz as it avoids the use of
baluns which are often limited to 1 000 MHz. With this configuration it is possible to measure impedance and
return loss both of the differential and common mode.
Multiport vector network analyser VNA (having at least 4 ports) with
— S-parameter set-up;
— A mathematical conversion from unbalanced to balanced, i.e. the mixed mode set-up which is often
referred to as an unbalanced, modal decomposition or balun-less setup. This allows measurements of
balanced devices without use of an RF balun in the signal path. With such a test set-up, all balanced and
unbalanced parameters can be measured over the full frequency range;
— Coaxial cables – where the characteristic impedance shall be the same as the nominal impedance of the
VNA – are needed to interconnect the network analyser, switching matrix and the test fixture. The screen
12
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EN 50289-1-11:2016 (E)
of the coaxial cables shall have a low transfer impedance, i.e. double screen or more with a transfer
impedance less than 100 mΩ/m at 100 MHz. The screens of each cable shall be electrically bonded to a
common ground plane, with the screens of the cable bonded to each other at multiple points along their
length. To optimize the dynamic range, the total interconnecting cable attenuation shall not exceed 3 dB
at 1 000 MHz;
— To perform a calibration at the end of the coaxial interconnection cable coaxial reference standards, so
called calibration standards, i.e. a short circuit, an open circuit and a reference load, are required. An
alternative to the before mentioned open, short and load references is the use of an electronic multiport
calibration kit (E-cal module) which is supplied by the supplier of the VNA.
— If the calibration is performed at the test interface calibration reference artefact, i.e. a short circuit, an
open circuit and a reference load, are required. For further details refer to EN 50289-1-1.
— Termination loads as described in Annex C.
5.2.2 Test sample
The CUT shall have or exceed the minimum length specified in the relevant sectional specification. Both ends
of the CUT shall be prepared, such that when connected to the terminals of the test equipment the influence
to the test result is minimised. In case of balanced cables the twisting of the pairs/quads shall be maintained.
5.2.3 Calibration procedure
It is not the intent of the standard to detail the algorithms applied by a VNA to correct the measured results
based on a calibration procedure but to detail the calibration procedure. Further information may be obtained
in the manuals of the VNA supplier.
A full 4-port single ended (SE) calibration shall be performed. The calibration shall be either performed at the
ends of the coaxial interconnection cables or on the test interface.
In the first case open, short and load measurements (using coaxial reference standards, so called calibration
standards) shall be taken at the ends of the coaxial interconnection cables of each port concerned, and
through and isolation measurements shall be
...
SLOVENSKI STANDARD
oSIST prEN 50289-1-11:2016
01-julij-2016
.RPXQLNDFLMVNLNDEOL6SHFLILNDFLMH]DSUHVNXVQHPHWRGHGHO (OHNWULþQH
SUHVNXVQHPHWRGH.DUDNWHULVWLþQDLPSHGDQFDYKRGQDLPSHGDQFDSRYUDWQH
L]JXEH
Communication cables - Specifications for test methods - Part 1-11: Electrical test
methods - Characteristic impedance, input impedance, return loss
Kommunikationskabel - Spezifikationen für Prüfverfahren - Teil 1-11: Elektrische
Prüfverfahren - Wellenwiderstand, Eingangsimpedanz, Rückflußdämpfung
Câbles de communication - Spécifications des méthodes d'essai - Partie 1-11: Méthodes
d'essais électriques - Impédance caractéristique, impédance d'entrée, affaiblissement de
réflexion
Ta slovenski standard je istoveten z: prEN 50289-1-11
ICS:
33.120.20 äLFHLQVLPHWULþQLNDEOL Wires and symmetrical
cables
oSIST prEN 50289-1-11:2016 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN 50289-1-11:2016
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oSIST prEN 50289-1-11:2016
EUROPEAN STANDARD DRAFT
prEN 50289-1-11
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2016
ICS 33.120.20 Will supersede EN 50289-1-11:2001
English Version
Communication cables - Specifications for test methods - Part
1-11: Electrical test methods - Characteristic impedance, input
impedance, return loss
Câbles de communication - Spécifications des méthodes Kommunikationskabel - Spezifikationen für Prüfverfahren -
d'essai - Partie 1-11: Méthodes d'essais électriques - Teil 1-11: Elektrische Prüfverfahren - Wellenwiderstand,
Impédance caractéristique, impédance d'entrée, Eingangsimpedanz, Rückflußdämpfung
affaiblissement de réflexion
This draft European Standard is submitted to CENELEC members for enquiry.
Deadline for CENELEC: 2016-07-29.
It has been drawn up by CLC/TC 46X.
If this draft becomes a European Standard, 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.
This draft European Standard was established by CENELEC 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 CEN-CENELEC Management Centre has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to
provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and
shall not be referred to as a European Standard.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2016 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Project: 61099 Ref. No. prEN 50289-1-11 E
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1 Contents Page
2 European foreword . 4
3 1 Scope . 5
4 2 Normative references . 5
5 3 Terms and definitions . 5
6 4 Test method for mean characteristic impedance (S type measurement) . 9
21
7 4.1 Principle . 9
8 4.2 Expression of test results . 9
9 5 Test method for input impedance and return loss (S type measurement) . 10
11
10 5.1 Method A: measurement of balanced cables using balun setup . 10
11 5.1.1 Test Equipment . 10
12 5.1.2 Test sample . 11
13 5.1.3 Calibration procedure . 11
14 5.1.4 Measuring procedure . 11
15 5.2 Method B: measurement of balanced cables using balun-less setup . 12
16 5.2.1 Test Equipment . 12
17 5.2.2 Test sample . 12
18 5.2.3 Calibration procedure . 12
19 5.2.4 Measuring procedure . 13
20 5.3 Method C: measurement of coaxial cables . 13
21 5.3.1 Test Equipment . 13
22 5.3.2 Test sample . 14
23 5.3.3 Calibration procedure . 14
24 5.3.4 Measuring procedure . 14
25 5.4 Expression of test results . 14
26 6 Test report . 16
27 Annex A (normative) Function fitting of input impedance . 17
28 A.1 General . 17
29 A.2 Polynomial function for function fitting of input impedance . 17
30 A.3 Fewer terms . 18
31 Annex B (normative) Correction procedures for the measurement results of return loss and
32 input impedance . 19
33 B.1 General . 19
34 B.2 Parasitic inductance corrected return loss (PRL) . 19
35 B.3 Gated return loss (GRL) . 21
36 B.4 Fitted return loss (FRL) . 23
37 B.5 Comparison of gated return loss (GRL) with fitted return loss (FRL) . 28
38 B.6 Influence of the correction technique on return loss peaks . 29
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39 Annex C (normative) Termination loads for termination of conductor pairs . 31
40 C.1 General . 31
41 C.2 Verification of termination loads. 32
42 Bibliography . 33
43
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44 European foreword
45 This document [prEN 50289-1-11:2016] has been prepared by CLC/TC 46X "Communication cables".
46 This document is currently submitted to the Enquiry.
47 The following dates are proposed:
• latest date by which the existence of (doa) dor + 6 months
this document has to be announced
at national level
• latest date by which this document has to be (dop) dor + 12 months
implemented at national level by publication of
an identical national standard or by
endorsement
• latest date by which the national standards (dow) dor + 36 months
conflicting with this document have to (to be confirmed or
be withdrawn modified when voting)
48 This document will supersede EN 50289-1-11:2001.
49 This European Standard has been prepared under the European Mandate M/212 given to CENELEC by the
50 European Commission and the European Free Trade Association.
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51 1 Scope
52 This Part of EN 50289 details the test methods to determine characteristic impedance, input impedance and
53 return loss of cables used in analogue and digital communication systems.
54 It is to be read in conjunction with EN 50289-1-1, which contains essential provisions for its application.
55 2 Normative references
56 The following documents, in whole or in part, are normatively referenced in this document and are
57 indispensable for its application. For dated references, only the edition cited applies. For undated references,
58 the latest edition of the referenced document (including any amendments) applies.
59 EN 50289-1-1:2001, Communication cables - Specifications for test methods - Part 1-1: Electrical test
60 methods - General requirements
61 EN 50289-1-5:2001, Communication cables - Specifications for test methods - Part 1-5: Electrical test
62 methods - Capacitance
63 EN 50289-1-7:2001, Communication cables - Specifications for test methods - Part 1-7: Electrical test
64 methods - Velocity of propagation
65 EN 50290-1-2, Communication cables - Part 1-2: Definitions
66 3 Terms and definitions
67 For the purposes of this document, the terms and definitions given in EN 50290-1-2 and the following apply.
68 3.1
69 characteristic impedance
70 Z
C
71 (wave) impedance at the input of a homogeneous line of infinite length. The characteristic impedance Z of a
c
72 cable is defined as the quotient of a voltage and current wave which are propagating in the same direction,
73 either forwards or backwards.
u
u
f
r
74 (1)
Z = =
C
i i
f r
75 where
Z is characteristic impedance;
c
u is voltage wave propagating in forward respectively reverse direction;
f,r
i is current wave propagating in forward respectively reverse direction.
f,r
76 3.2
77 mean characteristic impedance
78 Z
cm
79 in practice for real cables which always have structural variations the characteristic impedance is described
80 by the mean characteristic impedance which is derived from the measurement of the velocity of propagation
81 (EN 50289-1-7) and the mutual capacitance (EN 50289-1-5). However, this method is only applicable for
82 frequencies above 1 MHz and non-polar insulation materials (i.e. materials having a dielectric permittivity
83 which doesn’t change over frequency). The mean characteristic impedance approaches at sufficiently high
84 frequencies (≈100 MHz) an asymptotic value Z
∞
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85 The characteristic impedance may be expressed as the propagation coefficient divided by the shunt
86 admittance. This relationship holds at any frequency.
α + jβ β α
87 (2)
Z = ≈ − j
c
jωC(1− j tanδ ) ωC ωC
88 where
Z is complex characteristic impedance (Ω);
c
α is attenuation coefficient (Np/m) ;
β is phase constant (rad/m);
tanδ is loss factor;
ω -1
is circular frequency (s );
C is mutual capacitance (F/m).
89 At high frequencies, where the imaginary component of impedance is small, and the real component and
90 magnitude are substantially the same we get for the mean characteristic impedance
τ
β 1
p
91 (3)
Z ≈ = =
cm
ω × C C v × C
92 Where
Z is mean characteristic impedance (m);
cm
v is velocity of propagation (m/s);
τ is phase delay (s/m);
p
C is mutual capacitance (F/m).
93 3.3
94 terminated input impedance
95 Z
in
96 impedance measured at the near end (input) when the far end is terminated by a load resistance of value
97 equal to the system nominal impedance Z
R
98 3.4
99 open/short input impedance
100 Z
OS
101 impedance measured at the near end (input) when the far end is terminated with its own impedance. In
102 practice this is the case when the round trip attenuation is greater than 40 dB at any measured frequency.
103 This property takes into account structural variations in the cable. For samples with lower round trip loss it is
104 determined by the open/short circuit method:
105 Z = Z × Z (4)
os open short
106 where
Z is input Impedance of the cable obtained from an open/short measurement;
os
Z is impedance with an open circuit at the far end of the cable;
open
Z is impedance with a short circuit at the far end of the cable.
short
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107 3.5
108 fitted characteristic impedance
109
Z
fit
110 is obtained from a least square error function fitting of the open/short input impedance. The fitting can be
111 applied on the magnitude, real and imaginary part of the input impedance. The fitted characteristic
112 impedance is an alternative to the mean characteristic impedance to describe the characteristic impedance. It
113 is only valid if the variations with frequency of the input impedance around its characteristic impedance are
114 balanced.
115 3.6
116 (operational) return loss
117 RL
118 (operational) return loss is measured at the near end (input) when the far end is terminated by a load
119 resistance of value equal to the system nominal impedance Z . It quantifies the reflected signal caused by
R
120 impedance variations. The (operational) return loss takes into account the structural variations along the
121 cable length and the mismatch between the reference impedance and the (mean) characteristic impedance
122 of the cable (pair). If the (mean) characteristic impedance of the cable (pair) is different from the reference
123 impedance, one gets, especially at lower frequencies (where the round trip attenuation is low), multiple
124 reflections that are overlaid to the structural and junction reflections. Therefore, return loss RL is also
125 referenced as operational return loss.
126 As an example, Figure 1, shows the operational return loss under different conditions. The blue line shows
127 the return loss of a pair having a characteristic impedance equal to the reference impedance but taking into
128 account that the impedance is varying with frequency (see right-hand graph). The red line shows the return
129 loss of a pair having a characteristic impedance that is different from the reference impedance (110 Ω vs. 100
130 Ω). For both lines, periodic variations – that are caused by multiple reflections between the junctions at the
131 near and far end – are observed. The green line shows a simulation of a pair having a frequency independent
132 characteristic impedance which is equal to the reference impedance.
Return Loss frequency dependent factor of the characteristic impedance
1,2 0,2
0
RLRL w/o mismatch
1,16 0,16
5 RLRL w mismatch
RLRL w /o mismatch; ZZcc frequency independent
1,12 0,12
10
1,08 0,08
15
1,04 0,04
20
1 0
25 Real
Imag
0,96 -0,04
30
0,92 -0,08
35
0,88 -0,12
40
0,84 -0,16
45
0,8 -0,2
0,1 1 10 100
50
0,1 1 10 100 MHz
MHz
133 Figure 1 — Return loss with and without junction reflections
134 3.7
135 open/short return loss
136 OSRL
137 way to avoid in the measurement of return loss multiple reflections due to a mismatch between the
138 characteristic impedance (asymptotic value at high frequencies) of the CUT and the reference impedance is
139 to use a CUT terminated in its nominal impedance and having a very long test length such that the round trip
140 attenuation of the CUT is at least 40 dB at the lowest frequency to be measured. For standard LAN cables,
141 this would result in a CUT length of roughly 1 000 m for the lowest frequency of 1 MHz.
142 Another way (when long CUT length is not available) is to measure the characteristic impedance (open/short
143 method) and to calculate the return loss. As the characteristic impedance is obtained from the measurement
144 of the open and short circuit impedance, it is proposed to name such obtained return loss open/short return
145 loss.
7
dB
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146 This open/short return loss includes the effect of structural variations and the mismatch at the near end
147 (including the effect due to a frequency-dependent characteristic impedance), but it does not take into
148 account multiple reflections.
149 Figure 2 shows the difference between operational return loss and open/short return loss. The left-hand
150 graph shows the results of a pair having a characteristic impedance which is different from the reference
151 impedance (110 Ω vs. 100 Ω). The right-hand graph shows the results of a pair having a characteristic
152 impedance which is equal to the reference impedance (100 Ω). One may recognize that the open/short return
153 loss does not take into account multiple reflections.
Return Loss Return Loss
0 0
RLRL w mismatch RLRL w /o mismatch
5 5
OSOSRLRL w/o mismatch
OSOSRLRL w mismatch
10 10
15 15
20 20
25 25
30 30
35 35
40 40
45 45
50 50
0,1 1 10 100 0,1 1 10 100
MHz MHz
154 Figure 2 — Return loss and open/short return loss
155 3.8
156 structural return loss
157 SRL
158 The structural return loss is the return loss where only structural variations along the cable are taken into
159 account. The mismatch effects at the input and output of the transmission line (including the effect due to a
160 frequency-dependent characteristic impedance) have been eliminated. The structural return loss cannot be
161 measured directly but is calculated from the measurement of the characteristic impedance (open/short
162 method).
Z − Z
OS fit
163 SRL = 20 ×lg (5)
Z + Z
OS fit
164 where
Z is the (complex) input impedance obtained from the measurement of the open and short
OS
circuit impedance;
is the (complex) characteristic impedance obtained from a curve fitting of the real and
Z
fit
imaginary part of ZOS.
165 The left-hand graph of Figure 3 shows the operational return loss, open/short return loss and structural return
166 loss of a CUT having a characteristic impedance of 110 Ω. A difference between both is observable. The
167 operational return loss takes into account all effects (structural variations, mismatch effects at the input and
168 output). The open/short return loss does not take into account mismatch effects at the output (i.e. no multiple
169 reflections). Whereas the structural return loss only takes into account structural variations along the cable.
170 The right-hand graph shows the real and imaginary part of the mean characteristic impedance (obtained from
171 the measurement of the open and short circuit impedance) and it’s fitting.
8
dB
dB
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Return Loss Mean Characteristic Impedance
0 140 80
RLRL
130 70
OSOSRLRL
10
SSRLRL
120 60
20
110 50
30
100 40
Re(Zos)
fitted Re(Zos)
40 90 30
Im(Zos)
fitted Im(Zos)
80 20
50
70 10
60
60 0
70
50 -10
80 40 -20
0,1 1 10 100 0,1 1 10 100
MHz MHz
172 Figure 3 — Return loss, open short return loss and structural return loss
173 3.9
174 parasitic inductance corrected return loss
175 PRL
176 return loss where the effect a parasitic inductance (due to sample preparation and/or test fixture), which is
177 observed as an increase of the input impedance at high frequencies (above 100 Mhz), has been corrected
178 3.10
179 gated return loss
180 GRL
181 return loss where the effect of the test fixtures and sample preparation, which is observed as an increase of
182 the input impedance at high frequencies (above 100 MHz), has been corrected by a gating function
183 3.11
184 fitted return loss
185 FRL
186 return loss where the effect of the test fixtures and sample preparation, which is observed as an increase of
187 the input impedance at high frequencies (above 100 MHz), has been corrected by applying fitting function on
188 the input impedance
189 4 Test method for mean characteristic impedance (S type measurement)
21
190 4.1 Principle
191 This method shall only be applied for cables having non-polar insulation materials (e.g. PE, PTFE), i.e.
192 materials having a dielectric permittivity which doesn’t change over frequency. Or in other words this method
193 shall only be applied to cables having a mutual capacitance which doesn’t change over frequency.
194 The mean characteristic impedance shall be derived from the measurement of the velocity of propagation,
195 respectively phase delay, according to EN 50289-1-7 and the mutual capacitance according EN 50289-1-5.
196 The measurement shall be carried out at frequencies above 100 MHz where the phase delay approaches an
197 asymptotic value.
198 4.2 Expression of test results
199 The mean characteristic impedance Z shall be derived from Formula (6):
cm
τ
1
p
200 (6)
Z = =
cm
C v × C
9
dB
Real Part [Ohm]
Imaginary Part [Ohm]
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201 where
Z is mean characteristic impedance (m);
cm
v is velocity of propagation (m/s), measured according EN 50289-1-7;
τ is phase delay (s/m), measured according EN 50289-1-7;
p
C is mutual capacitance (F/m), measured according EN 50289-1-5.
202 5 Test method for input impedance and return loss (S type measurement)
11
203 5.1 Method A: measurement of balanced cables using balun setup
204 5.1.1 Test Equipment
205 The test equipment consists of a 2-port vector network analyser (VNA) with:
206 — S-parameter set-up;
207 — Balun to convert the unbalanced signal of the VNA to a balanced signal. The balun shall have an
208 impedance on the primary (unbalanced) side equal to the nominal impedance of the measuring devices
209 (in general 50 Ω) and on the secondary (balanced) side equal to the nominal impedance of the CUT (e.g.
210 100 Ω) (the balun shall fulfil the requirements of Class A baluns as described in EN 50289-1-1);
211 — To perform a calibration of the test equipment (on the secondary side of the balun), a short circuit, an
212 open circuit and a reference load are required. The short circuit shall have negligible inductance and the
213 open circuit shall have negligible capacitance. The load resistor shall have a value close (within 1%) to
214 the nominal impedance of the CUT (e.g. 100 Ω) and with negligible inductance and capacitance;
215 — For the measurement of the input impedance and (operational) return loss a T-resistor network (see
216 Figure 4) is required to terminate the common and differential mode impedance at the far end of the
217 sample. The differential mode termination resistors shall be matched in pairs, each half the value of the
218 differential mode reference impedance Z (in general 100 Ω). If not specified otherwise, for example by
R
219 particular cabling standards, the common mode termination resistors shall be:
220 — 0 Ω for individually screened pair cables;
221 — 25 Ω for overall screened cables;
222 — 45 Ω to 50 Ω for unscreened cables.
223
224 Key
DM
R differential mode termination resistor
term
CM
R common mode termination resistor
term
225 Figure 4 — T-resistor network
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226 5.1.2 Test sample
227 The CUT shall have a minimum length as specified in the relevant sectional specification. Both ends of the
228 CUT shall be prepared, such that when connected to the terminals of the test equipment the influence to the
229 test result is minimised. The twisting of the pairs/quads shall be maintained.
230 5.1.3 Calibration procedure
231 It is not the intent of the standard to detail the algorithms applied by a VNA to correct the measured results
232 based on a calibration procedure but to detail the calibration procedure. Further information may be obtained
233 in the manuals of the VNA supplier.
234 The calibration shall be performed on the secondary side of the balun by applying consecutively an open,
235 short and load standard (see Figure 5).
Ri
open
reflection
Generator
bridge
short
Ri
Receiver
load
236
237 Figure 5 — Calibration set-up
238 5.1.4 Measuring procedure
239 The test sample shall be connected to the terminals of test fixture. The scattering parameter S – i.e. the
xx
240 reflection coefficient Γ (in Formulae (8) to (12)) – shall be measured over the whole specified frequency range
241 and at the same frequency points as for the calibration procedure. The values shall be measured as complex
242 parameters. All pairs/quads shall be measured from both ends unless otherwise specified.
243 a) terminated input impedance (Z ) and (operational) return loss (RL)
in
244 Measure the scattering parameter S – i.e. the reflection coefficient Γ – of the CUT with the far end
xx
245 terminated by a load resistance as described in 4.1.1. Inactive pairs shall also be terminated by this T-
246 resistor network.
247 b) Open/short input impedance (Z ) and open/short return loss (OSRL)
OS
248 Measure consecutively the scattering parameter S – i.e. the reflection coefficient Γ – of the CUT with
xx
249 the far end in open and short circuit.
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250 5.2 Method B: measurement of balanced cables using balun-less setup
251 5.2.1 Test Equipment
252 Method B is the preferred one for balanced cables for frequencies above 1 000 MHz as it avoids the use of
253 baluns which are often limited to 1 000 MHz. With this configuration it is possible to measure impedance and
254 return loss both of the differential and common modes.
255 Multiport vector network analyser VNA (having at least 4 ports) with
256 — S-parameter set-up;
257 — A mathematical conversion from unbalanced to balanced, i.e. the mixed mode set-up which is often
258 referred to as an unbalanced, modal decomposition or balun-less setup. This allows measurements of
259 balanced devices without use of an RF balun in the signal path. With such a test set-up, all balanced and
260 unbalanced parameters can be measured over the full frequency range;
261 — Coaxial cables – where the characteristic impedance shall be the same as the nominal impedance of the
262 VNA – are needed to interconnect the network analyser, switching matrix and the test fixture. The screen
263 of the coaxial cables shall have a low transfer impedance, i.e. double screen or more with a transfer
264 impedance less than 100 mΩ/m at 100 MHz. The screens of each cable shall be electrically bonded to a
265 common ground plane, with the screens of the cable bonded to each other at multiple points along their
266 length. To optimize the dynamic range, the total interconnecting cable attenuation shall not exceed 3 dB
267 at 1 000 MHz;
268 — To perform a calibration at the end of the coaxial interconnection cable coaxial reference standards, so
269 called calibration standards, i.e. a short circuit, an open circuit and a reference load, are required. An
270 alternative to the before mentioned open, short and load references is the use of an electronic multiport
271 calibration kit (E-cal module) which is supplied by the supplier of the VNA.
...
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