IEC TR 61156-1-2:2009

IEC/TR 61156-1-2 ®
Edition 1.0 2009-05
TECHNICAL
REPORT
Multicore and symmetrical pair/quad cables for digital communications –
Part 1-2: Electrical transmission characteristics and test methods of symmetrical
pair/quad cables
IEC/TR 61156-1-2:2009(E)
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IEC/TR 61156-1-2 ®
Edition 1.0 2009-05
TECHNICAL
REPORT
Multicore and symmetrical pair/quad cables for digital communications –
Part 1-2: Electrical transmission characteristics and test methods of
symmetrical pair/quad cables
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
X
ICS 33.120.20 ISBN 978-2-88910-418-5
– 2 – TR 61156-1-2 © IEC:2009(E)

CONTENTS
FOREWORD.4

1 Scope.6

2 Normative references .6

3 Terms, definitions, symbols, units and abbreviated terms .6

3.1 Terms and definitions .6

3.2 Symbols, units and abbreviated terms .6

4 Basic transmission line equations.9

4.1 Introduction .9
4.2 Characteristic impedance and propagation coefficient equations .10
4.2.1 General .10
4.2.2 Propagation coefficient .10
4.2.3 Characteristic impedance .11
4.2.4 Phase and group velocity .12
4.3 High frequency representation of secondary parameters .13
4.4 Frequency dependence of the primary and secondary parameters .14
4.4.1 Resistance .14
4.4.2 Inductance.14
4.4.3 Characteristic impedance .15
4.4.4 Attenuation coefficient .15
4.4.5 Phase delay and group delay.16
5 Measurement of characteristic impedance .17
5.1 General .17
5.2 Open/short circuit single-ended impedance measurement made with a balun
(reference method).18
5.2.1 Principle .18
5.2.2 Test equipment.18
5.2.3 Procedure.19
5.2.4 Expression of results .19
5.3 Function fitting the impedance magnitude and angle .20
5.3.1 General .20
5.3.2 Impedance magnitude .20
5.3.3 Function fitting the angle of the characteristic impedance .22

5.4 Characteristic impedance determined from measured phase coefficient and
capacitance.22
5.4.1 General .22
5.4.2 Equations for all frequencies case and for high frequencies.22
5.4.3 Procedure for the measurement of the phase coefficient .23
5.4.4 Phase delay .25
5.4.5 Phase velocity .25
5.4.6 Procedure for the measurement of the capacitance .25
5.5 Determination of characteristic impedance using the terminated
measurement method.25
5.6 Extended open/short circuit method using a balun but excluding the balun
performance .26
5.6.1 Test equipment and cable-end preparation .26
5.6.2 Basic equations .26
5.6.3 Measurement principle .26

TR 61156-1-2 © IEC:2009(E) – 3 –

5.7 Extended open/short circuit method without using a balun.28

5.7.1 Basic equations and circuit diagrams.28

5.7.2 Measurement principle .30

5.8 Open/short impedance measurements at low frequencies with a balun.31

5.9 Characteristic impedance and propagation coefficient obtained from modal

decomposition technique .32

5.9.1 General .32

5.9.2 Procedure.33

5.9.3 Measurement principle .33

5.9.4 Scattering matrix to impedance matrix .35

5.9.5 Expression of results .37
6 Measurement of return loss and structural return loss .37
6.1 General .37
6.2 Principle.37
7 Propagation coefficient effects due to periodic structural variation related to the
effects appearing in the structural return loss .38
7.1 General .38
7.2 Equation for the forward echoes caused by periodic structural
inhomogeneities .38
8 Unbalance attenuation.40
8.1 General .40
8.2 Unbalance attenuation near end and far end .40
8.3 Theoretical background .42
Bibliography.46

Figure 1 – Secondary parameters extending from 1 kHz to 1 GHz.16
Figure 2 – Diagram of cable pair measurement circuit.19
Figure 3 – Determining the multiplier of 2π radians to add to the phase measurement .24
Figure 4 – Measurement configurations .27
Figure 5 – Measurement principle with four terminal network theory .27
Figure 6 – Admittance measurement configurations .30
Figure 7 – Admittance measurement principle.30
Figure 8 – Transmission line system .34
Figure 9 – Differential-mode transmission in a symmetric pair.40

Figure 10 – Common-mode transmission in a symmetric pair.40
Figure 11 – Circuit of an infinitesimal element of a symmetric pair .43
Figure 12 – Calculated coupling transfer function for a capacitive coupling of 0,4 pF/m
and random ±0,4 pF/m (l = 100 m; ε = ε = 2,3).45
r1 r2
Figure 13 – Measured coupling transfer function of 100 m Twinax 105 Ω .45

Table 1 – Unbalance attenuation at near end.41
Table 2 – Unbalance attenuation at far end.41
Table 3 – Measurement set-up.42

– 4 – TR 61156-1-2 © IEC:2009(E)

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
MULTICORE AND SYMMETRICAL PAIR/QUAD CABLES FOR DIGITAL

COMMUNICATIONS –
PART 1-2: ELECTRICAL TRANSMISSION CHARACTERISTICS AND TEST

METHODS OF SYMMETRICAL PAIR/QUAD CABLES

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since
...

IEC TR 61156-1-2 ®
Edition 1.1 2014-09
CONSOLIDATED VERSION
TECHNICAL
REPORT
colour
inside
Multicore and symmetrical pair/quad cables for digital communications –
Part 1-2: Electrical transmission characteristics and test methods of
Symmetrical pair/quad cables
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form

or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from

either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or

your local IEC member National Committee for further information.

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3, rue de Varembé Fax: +41 22 919 03 00

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Switzerland www.iec.ch
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IEC TR 61156-1-2 ®
Edition 1.1 2014-09
CONSOLIDATED VERSION
TECHNICAL
REPORT
colour
inside
Multicore and symmetrical pair/quad cables for digital communications –

Part 1-2: Electrical transmission characteristics and test methods of

Symmetrical pair/quad cables
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.120.20 ISBN 978-2-8322-1857-0

IEC TR 61156-1-2 ®
Edition 1.1 2014-09
CONSOLIDATED VERSION
REDLINE VERSION
colour
inside
Multicore and symmetrical pair/quad cables for digital communications –
Part 1-2: Electrical transmission characteristics and test methods of
Symmetrical pair/quad cables
– 2 – IEC TR 61156-1-2:2009
+AMD1:2014 CSV  IEC 2014
CONTENTS
FOREWORD . 5

1 Scope . 7

2 Normative references . 7

3 Terms, definitions, symbols, units and abbreviated terms . 7

3.1 Terms and definitions . 7

3.2 Symbols, units and abbreviated terms . 8

4 Basic transmission line equations . 11

4.1 Introduction . 11
4.2 Characteristic impedance and propagation coefficient equations . 11
4.2.1 General . 11
4.2.2 Propagation coefficient . 11
4.2.3 Characteristic impedance . 12
4.2.4 Phase and group velocity . 13
4.3 High frequency representation of secondary parameters . 14
4.4 Frequency dependence of the primary and secondary parameters . 15
4.4.1 Resistance . 15
4.4.2 Inductance . 16
4.4.3 Characteristic impedance . 16
4.4.4 Attenuation coefficient . 16
4.4.5 Phase delay and group delay . 17
5 Measurement of characteristic impedance . 18
5.1 General . 18
5.2 Open/short circuit single-ended impedance measurement made with a balun
(reference method) . 19
5.2.1 Principle . 19
5.2.2 Test equipment . 20
5.2.3 Procedure . 20
5.2.4 Expression of results . 21
5.3 Function fitting the impedance magnitude and angle . 21
5.3.1 General . 21
5.3.2 Impedance magnitude . 21
5.3.3 Function fitting the angle of the characteristic impedance . 23

5.4 Characteristic impedance determined from measured phase coefficient and
capacitance . 23
5.4.1 General . 23
5.4.2 Equations for all frequencies case and for high frequencies . 24
5.4.3 Procedure for the measurement of the phase coefficient . 24
5.4.4 Phase delay . 26
5.4.5 Phase velocity . 26
5.4.6 Procedure for the measurement of the capacitance . 26
5.5 Determination of characteristic impedance using the terminated
measurement method . 26
5.6 Extended open/short circuit method using a balun but excluding the balun
performance . 27
5.6.1 Test equipment and cable-end preparation . 27
5.6.2 Basic equations . 27

+AMD1:2014 CSV  IEC 2014
5.6.3  Measurement principle . 27

5.7  Extended open/short circuit method without using a balun . 29

5.7.1  Basic equations and circuit diagrams . 29

5.7.2  Measurement principle . 31

5.8  Open/short impedance measurements at low frequencies with a balun. 32

5.9  Characteristic impedance and propagation coefficient obtained from modal

decomposition technique . 33

5.9.1  General . 33

5.9.2  Procedure . 34

5.9.3  Measurement principle . 34

5.9.4  Scattering matrix to impedance matrix . 36
5.9.5  Expression of results . 38
6  Measurement of return loss and structural return loss . 38
6.1  General . 38
6.2  Principle . 38
7  Propagation coefficient effects due to periodic structural variation related to the
effects appearing in the structural return loss . 39
7.1  General . 39
7.2  Equation for the forward echoes caused by periodic structural
inhomogeneities . 39
8  Unbalance attenuation . 40
8.1  General . 40
8.2  Unbalance attenuation near end and far end . 41
8.3  Theoretical background . 43
9  Balunless test method . 46
9.1  Overall test arrangement . 46
9.1.1  Test instrumentation . 46
9.1.2  Measurement precautions . 47
9.1.3  Mixed mode S-parameter nomenclature . 47
9.1.4  Coaxial cables and interconnect for network analysers . 48
9.1.5  Reference loads for calibration . 49
9.1.6  Calibration . 49
9.1.7  Termination loads for termination of conductor pairs . 50
9.1.8  Termination of screens . 51
9.2  Cabling and cable measurements . 52

9.2.1  Insertion loss and EL TCTL . 52
9.2.2  NEXT . 53
9.2.3  ACR-F . 55
9.2.4  Return loss and TCL . 57
9.2.5  PS alien near-end crosstalk (PS ANEXT-Exogenous crosstalk) . 59
9.2.6  PS attenuation to alien crosstalk ratio, far-end crosstalk (PS AACR-
F- Exogenous crosstalk . 62
Annex A (informative) Example derivation of mixed mode parameters using the modal
decomposition technique . 66
Bibliography . . 69

Figure 1 – Secondary parameters extending from 1 kHz to 1 GHz . 18
Figure 2 – Diagram of cable pair measurement circuit . 20

– 4 – IEC TR 61156-1-2:2009
...