Bsi bs en 50289 1 9 2017

BS EN 50289-1-9:2017 BSI Standards Publication Communication cables — Specifications for test methods Part 1-9: Electrical test methods — Unbalance attenuation (transverse conversion loss TCL transverse conversion transfer loss TCTL) BS EN 50289-1-9:2017 BRITISH STANDARD National foreword This British Standard is the UK implementation of EN 50289-1-9:2017 It supersedes BS EN 50289-1-9:2002 which is withdrawn The UK participation in its preparation was entrusted to Technical Committee EPL/46, Cables, wires and waveguides, radio frequency connectors and accessories for communication and signalling A list of organizations represented on this committee can be obtained on request to its secretary This publication does not purport to include all the necessary provisions of a contract Users are responsible for its correct application © The British Standards Institution 2017 Published by BSI Standards Limited 2017 ISBN 978 580 94378 ICS 33.120.20 Compliance with a British Standard cannot confer immunity from legal obligations This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 March 2017 Amendments/corrigenda issued since publication Date Text affected BS EN 50289-1-9:2017 EUROPEAN STANDARD EN 50289-1-9 NORME EUROPÉENNE EUROPÄISCHE NORM March 2017 ICS 33.120.20 Supersedes EN 50289-1-9:2001 English Version Communication cables - Specifications for test methods Part 1-9: Electrical test methods - Unbalance attenuation (transverse conversion loss TCL transverse conversion transfer loss TCTL) Câbles de communication - Spécifications des méthodes d'essai Partie 1-9: Méthodes d'essais électriques Affaiblissement de disymétrie (perte de conversion longitudinale, perte de transfert de conversion longitudinale) Kommunikationskabel - Spezifikationen für Prüfverfahren Teil 1-9: Elektrische Prüfverfahren - Unsymmetriedämpfung (Unsymmetriedämpfung am nahen und am fernen Ende) This European Standard was approved by CENELEC on 2016-12-16 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, Serbia, 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 © 2017 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members Ref No EN 50289-1-9:2017 E BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) Contents Page European foreword Scope Normative references Terms and definitions 4 Test method 4.1 4.1.1 Test equipment 4.1.2 Test sample 4.1.3 Calibration procedure 4.1.4 Measuring procedure 4.1.5 Expression of test results 10 4.2 Method A: measurement using balun setup Method B: measurement using balun-less setup 11 4.2.1 Test equipment 11 4.2.2 Test sample 11 4.2.3 Calibration procedure 12 4.2.4 Measuring procedure 12 4.2.5 Expression of test results 13 Test report 14 Annex A (informative) General background of unbalance attenuation 15 A.1 General 15 A.2 Unbalance attenuation near end and far end 16 A.3 Theoretical background 17 Bibliography 21 BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) European foreword This document [EN 50289-1-9:2017] has been prepared by CLC/TC 46X “Communication cables” The following dates are fixed: • latest date by which this document has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2017-09-16 • latest date by which the national standards conflicting with this document have to be withdrawn (dow) 2019-12-16 This document supersedes EN 50289-1-9:2001 Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights CENELEC shall not be held responsible for identifying any or all such patent rights EN 50289-1, Communication cables — Specifications for test methods, is currently composed with the following parts: — Part 1-1: Electrical test methods — General requirements; — Part 1-2: Electrical test methods — DC resistance; — Part 1-3: Electrical test methods — Dielectric strength; — Part 1-4: Electrical test methods — Insulation resistance; — Part 1-5: Electrical test methods — Capacitance; — Part 1-6: Electrical test methods — Electromagnetic performance; — Part 1-7: Electrical test methods — Velocity of propagation; — Part 1-8: Electrical test methods — Attenuation; — Part 1-9: Electrical test methods — Unbalance attenuation (transverse conversion loss TCL transverse conversion transfer loss TCTL); — Part 1-10: Electrical test methods — Crosstalk; — Part 1-11: Electrical test methods — Characteristic impedance, input impedance, return loss; — Part 1-12: Electrical test methods — Inductance; — Part 1-13: Electrical test methods — Coupling attenuation or screening attenuation of patch cords / coaxial cable assemblies / pre-connectorised cables; — Part 1-14: Electrical test methods — Coupling attenuation or screening attenuation of connecting hardware; — Part 1-15: Electromagnetic performance — Coupling attenuation of links and channels (Laboratory conditions); — Part 1-16: Electromagnetic performance — Coupling attenuation of cable assemblies (Field conditions); — Part 1-17: Electrical test methods — Exogenous Crosstalk ExNEXT and ExFEXT BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) Scope This European Standard details the test methods to determine the attenuation of converted differential-mode signals into common-mode signals, and vice versa, due to balance characteristics of cables used in analogue and digital communication systems by using the transmission measurement method The unbalance attenuation is measured in, respectively converted to, standard operational conditions If not otherwise specified, e.g by product specifications, the standard operational conditions are a differential-mode which is matched with its nominal characteristic impedance (e.g 100 Ω) and a common-mode which is loaded with 50 Ω The difference between the (image) unbalance attenuation (matched conditions in the differential and common-mode) to the operational (Betriebs) unbalance attenuation (matched conditions in differential-mode and 50 Ω reference load in the common-mode) is small provided the common-mode impedance Zcom is in the range of 25 Ω to 75 Ω For cables having a nominal impedance of 100 Ω, the value of the common-mode impedance Zcom is about 75 Ω for up to 25 pair- count unscreened pair cables, 50 Ω for common screened pair cables and more than 25 pair- count unscreened pair cables, and 25 Ω for individually screened pair cables The impedance of the common-mode circuit Zcom can be measured more precisely either with a time domain reflectometer (TDR) or a network analyser The two conductors of the pair are connected together at both ends and the impedance is measured between these conductors and the return path This European Standard is bound to be read in conjunction with EN 50289-1-1, which contains essential provisions for its application 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 50289-1-1:2017, Communication cables — Specifications for test methods — Part 1-1: Electrical test methods — General requirements EN 50289-1-8, Communication cables - Specifications for test methods - Part 1-8: Electrical test methods Attenuation EN 50290-1-2, Communication cables - Part 1-2: Definitions 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 unbalance attenuation logarithmic ratio of the differential-mode power (transmission signal of a balanced pair) to the common-mode power (signal in the pair to ground/earth unbalanced circuit) measured at the near and at the far end Note to entry: The (operational) unbalance attenuation is described by the logarithmic ratio of the differential-mode power to the common-mode power in standard operational conditions If not otherwise specified, e.g by product specifications, the standard operational conditions are a differential-mode which is matched with its nominal characteristic impedance (e.g 100 Ω) and a common-mode which is loaded with 50 Ω a u = 10 × lg Pdiff Pcom = 20 × lg U diff Ucom Z + 10 × lg  com  Z  diff     where Pdiff is the power in the differential-mode (balanced) circuit; (1) BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) Pcom is the power in the common-mode (unbalanced) circuit; Udiff is the voltage in the differential-mode (balanced) circuit; Ucom is the voltage in the common-mode (unbalanced) circuit; Zdiff is the characteristic impedance of the differential-mode (balanced) circuit; Zcom is the characteristic impedance of the common-mode (unbalanced) circuit 3.2 transverse conversion loss TCL logarithmic ratio of the differential-mode injected signal at the near end to the resultant common-mode signal at the near end of a balanced pair, and which is equal to unbalance attenuation at near end when the CUT is terminated with the same impedances as defined for unbalance attenuation measurement Note to entry: This definition stems from ITU-G.117 3.3 transverse conversion transfer loss TCTL logarithmic ratio of the differential-mode injected signal at the near end to the resultant common-mode signal at the far end of a balanced pair, and which is equal to unbalance attenuation at far end when the CUT is terminated with the same impedances as defined for unbalance attenuation measurement Note to entry: This definition stems from ITU-G.117 Test method 4.1 Method A: measurement using balun setup 4.1.1 Test equipment a) It is mandatory to create a defined return (common-mode) path This is achieved by grounding all other pairs and screen(s) if present in common to the balun ground However in addition in the case of unscreened cables the cable under test shall be wound onto a grounded metal drum The drum surface may have a suitable groove, wide enough to contain the cable, and shall be adequate to hold 100 m of cable in one layer The pair under test shall be terminated with differential-mode and common-mode terminations and grounded at near and far ends b) A network analyser or generator/receiver combination suitable for the required frequency and dynamic range c) The baluns shall have a common-mode port and the characteristics given in EN 50289-1-1:2017, Table d) Time domain reflectometer (optional) 4.1.2 Test sample The ends of the cable under test (CUT) shall be prepared so that the twisting of the pairs/quads is maintained up to the terminals of the test equipment If not otherwise specified the CUT shall have a length of 100 m ± m For the measurement or evaluation of the equal level unbalance attenuation at the far end the following applies: if the CUT length is not otherwise specified and the attenuation of the CUT at the highest frequency to be measured is higher than or equal to 80 dB the length of the CUT may be reduced to limit the attenuation to maximum 80 dB All pairs not under test and all screens shall be connected in common to the same ground as the balun at both ends of the CUT BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) For unscreened cables the CUT shall be wound tightly around the metal drum in one layer The distance between the windings should be at least the diameter of the cable The metal drum shall be connected to the same ground as the balun, e.g by fixing the baluns to the drum 4.1.3 Calibration procedure a) The reference line calibration (0 dB-line) shall be determined by connecting coaxial cables between the analyser input and output The same coaxial cables shall also be used for the balun loss and unbalance attenuation measurements The calibration shall be established over the whole frequency range specified in the relevant cable specification This calibration method is valid for closely matched baluns that satisfy the characteristics of Table b) Figure gives the schematic for the measurement of the differential-mode loss of the baluns Two baluns are connected back to back on the symmetrical output side and their attenuation measured over the specified frequency range The connection between the two baluns shall be made with negligible loss Key U0 voltage at network analyser port or signal generator U1 Udiff voltage at network analyser port or receiver voltage at symmetrical port of baluns Figure — Test set-up for the measurement of the differential-mode loss of the baluns The differential-mode loss of the baluns is given by:  0, ×  20 × lg α diff =   U0  = −0, × 20 × lg S 21 U1   ( ) (2) where αdiff is the differential-mode loss of the balun (dB); S21 is the scattering parameter S21 (forward transmission coefficient) where port is the primary (unbalanced side) side of the near end balun and port is the primary side (unbalanced port) of the far end balun BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) c) Figure gives the schematic for the measurement of the common-mode loss of the baluns The baluns used in b) are connected together; the unbalanced balun ports are terminated with the nominal test equipment impedance, the test equipment is connected to the common-mode ports (centre taps) of the baluns Key U0 voltage at network analyser port or signal generator U1 voltage at network analyser port or receiver Figure — Test set-up for the measurement of the common-mode loss of the baluns The common-mode loss of the baluns is given by:  α com = 0, ×  20 × lg   U0  = −0, × 20 × lg S 21 U1   ( ) (3) where d) αcom is the common-mode loss of the balun (dB); S21 is the scattering parameter S21 (forward transmission coefficient) where port is the commonmode port of the near end balun and port is the common-mode port of the far end balun The operational attenuation of the balun αbalun takes into account the common-mode and differentialmode losses of the balun: α balun = α diff + α com (4) where αbalun is the operational attenuation or intrinsic loss of the balun (dB) NOTE More precise results can be obtained using either poling of the baluns for αdiff and αcom and averaging the results or using three baluns In the latter case, the assumption of identical baluns is not required BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) e) The voltage ratio of the balun can be expressed by the turns ratio of the balun and the operational attenuation of the balun: 20 × lg U diff 20 × lg U diff U0 U1 10 × lg = Z diff 10 × lg = Z diff Z0 Z1 − α balun (5) − α balun where Udiff is the differential-mode voltage at the input of the cable under test (V); U0 is the voltage at the network analyser port or signal generator (V); Zdiff is the characteristic impedance of the differential-mode circuit (Ω); Z0 is the output impedance of the network analyser or signal generator (Ω); U1 is the voltage at the input of the load (V); Z1 is the input impedance of the load (Ω) 4.1.4 Measuring procedure All pairs/quads of the cable shall be measured at both ends of the CUT The unbalance attenuation shall be measured over the whole-specified frequency range and at the same frequency points as for the calibration procedure The measurement is done under standard operational conditions, i.e one is measuring the Betriebs(operational) unbalance attenuation If not otherwise specified, e.g by product specifications, the standard operational conditions are a differential-mode which is matched with its nominal characteristic impedance (e.g 100 Ω) and a common-mode which is loaded with 50 Ω Figure gives a schematic of the measurement for unbalance attenuation at the near end Figure — Test set-up for unbalance attenuation at near end (TCL) BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) 4.1.5 Expression of test results The unbalance attenuation is defined as the logarithmic ratio of the differential-mode power to the commonmode power: α u,n = 20 × lg u,f Pdiff P = 20 × lg n,com f,com U diff U + 10 × lg Z com n,com f,com Z diff (8) where αu is the unbalance attenuation (dB) at the near end (subscript n) respectively far end (subscript f); Pcom is the common-mode power (W) at the near end (subscript n) respectively far end (subscript f); Pdiff is the differential-mode power (W); Zdiff is the nominal characteristic impedance of the differential-mode of the CUT; Zcom is the standardized operational impedance of the common-mode, 50 Ω When measuring with S-parameter test-sets, the output voltage of the generator is measured instead of the differential-mode voltage in the cable under test Taking the operational attenuation of the balun into account, the formula for the unbalance attenuation near or far end is: 10 × lg α u, n = u, f Pdiff Pn,com 10 × lg = U U0 + 10 × lg n, com f, com α u,= α meas + 10 × lg n f,n Pn,com − α balun f, com f, com = 20 × lg P0 Z com Z0 Z com Z0 (9) − α balun − α balun (10) The equal level unbalance attenuation at the far end is then: EL α u,= α meas + 10 × lg f Z com Z0 − α balun − α cable (11) where 10 EL αu,f is the equal level unbalance attenuation at far end (EL TCTL) (dB); αu is the unbalance attenuation (dB) at the near end (subscript n) respectively far end (subscript f); αbalun is the operational attenuation or intrinsic loss of the balun (dB); αcable is the attenuation of the pair under test (dB) and is measured according to EN 50289–1-8; BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) 4.2 Pcom is the common-mode power (W) at the near end (subscript n) respectively far end (subscript f); Pdiff is the differential-mode power (W); Z0 is the impedance of the generator (Ω); Zcom is the standardized operational impedance of the common-mode, 50 Ω Method B: measurement using balun-less setup 4.2.1 Test equipment Method B is the preferred one for balanced cables for frequencies above 000 MHz as it avoids the use of baluns which are often limited to 000 MHz With this configuration it is possible to change the operational conditions for unbalance attenuation to any desired value of the differential-mode and common-mode reference impedance It is mandatory to create a defined return (common-mode) path This is achieved by grounding all other pairs and screen(s) if present in common to the test system ground However in addition in the case of unscreened cables the cable under test shall be wound onto a grounded metal drum The drum surface may have a suitable groove, wide enough to contain the cable, and shall be adequate to hold 100 m of cable in one layer The pair under test shall be terminated with differential-mode and common-mode terminations and grounded at near and far ends Multiport vector network analyser VNA (having at least 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 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 100MHz 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 dB at 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 4.2.2 Test sample The ends of the cable under test (CUT) shall be prepared so that the twisting of the pairs/quads is maintained up to the terminals of the test equipment If not otherwise specified the CUT shall have a length of 100 m ± m For the measurement or evaluation of the equal level unbalance attenuation at the far end the following applies: if the CUT length is not otherwise specified and the attenuation of the CUT at the highest frequency to be measured is higher than or equal to 80 dB the length of the CUT may be reduced to limit the attenuation to maximum 80 dB All pairs not under test and all screens shall be connected in common to the test system ground at both ends of the CUT 11 BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) For unscreened cables the CUT shall be wound tightly around the metal drum in one layer The distance between the windings should be at least the diameter of the cable The metal drum shall be connected to the test system ground 4.2.3 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 taken on every pair combination of those ports One may also use an electronic multiport calibration kit (E-cal module) which reduces significantly the calibration time As the calibration plane is the end of the coaxial interconnection cables the effect of the test interface is not removed from the results which may have an influence in particular at high frequencies To remove the effect of the test interface it may be de-embedded from the measurement or a correction procedure applied If the effect of the test fixture is removed by de-embedding techniques it shall incorporate a fully populated 16 port S-matrix The de-embedded calibration shall not be performed by using only reflection terms (S11, S22, S33, S44) or only near-end terms (S11, S21, S12, S22) When the calibration is performed at the test interface, open, short and load measurements (using calibration reference artefacts) shall be taken on each SE port concerned, and through and isolation measurements shall be taken on every pair combination of those ports 4.2.4 Measuring procedure All pairs/quads of the cable shall be measured at both ends of the CUT The unbalance attenuation shall be measured over the whole-specified frequency range and at the same frequency points as for the calibration procedure The measurement is done under standard operational conditions, i.e one is measuring the Betriebs(operational) unbalance attenuation If not otherwise specified, e.g by product specifications, the standard operational conditions are a differential-mode which is matched with its nominal characteristic impedance (e.g 100 Ω) and a common-mode which is loaded with 50 Ω In the balun-less set-up the common-mode impedance of the system is half the differential-mode impedance of the system, i.e 25 Ω Therefore the test results shall be converted to the standardized common-mode impedance of 50 Ω This conversion is obtained by setting at the multi-port VNA the reference impedance of the common-mode to the standardized common-mode impedance of 50 Ω Further information may be obtained in the manuals of the VNA supplier (see common-mode impedance conversion function) and in EN 60512-28-100 The pair under test of the CUT is connected to the ports of the VNA, see Figure Figure — Connection of the pair under test to the VNA ports For the measurement of the unbalance attenuation at near end the mixed mode scattering parameter Scd11, and for the unbalance attenuation at far end the mixed mode scattering parameter Scd21 shall be measured Table shows the correspondence between unbalance attenuation and mixed mode scattering parameters (see also A.2) 12 BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) Table — Correspondence between unbalance attenuation and mixed mode scattering parameters 4.2.5 near end far end TCL TCTL measured at cable end A Scd11 Scd21 measured at cable end B Scd22 Scd12 Expression of test results The unbalance attenuation is defined as the logarithmic ratio of the differential-mode power to the commonmode power: α u,n = 20 × lg u,f Pdiff P = 20 × lg n,com f,com α u,n = −20 × lg S MM + 10 × lg u,f EL α u, f = α u,f + 10 × lg EL α u, f = α u,f + 10 × lg Z com Z0 Z com Z0 U diff U + 10 × lg n,com f,com Z com (12) Z diff Z com (13) Z diff − α cable (14) + 20 × lg S dd21 where αu is the unbalance attenuation (dB) at the near end (subscript n) respectively far end (subscript f); EL αu,f is the equal level unbalance attenuation at far end (EL TCTL) (dB); Pdiff is the differential-mode power (W); Pcom is the common-mode power (W) at the near end (subscript n) respectively far end (subscript f); Zdiff is the nominal characteristic impedance of the differential-mode of the CUT; Zcom is the standardized operational impedance of the common-mode, 50 Ω; αcable is the attenuation of the pair under test (dB) and is measured according to EN 50289–1-8; SMM mixed mode scattering parameter measurement, see Table corresponding to the unbalance attenuation 13 BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) Test report The test report shall include: — temperature, — frequency range, — sample length, — the unbalance attenuation, transverse conversion loss (TCL) or transverse conversion transfer loss (TCTL), as required 14 BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) Annex A (informative) General background of unbalance attenuation A.1 General Symmetric pairs may be operated in the differential-mode (balanced) (see Figure A.1) or the common-mode (unbalanced) (see Figure A.2) In the differential-mode, one conductor carries the current and the other conductor carries the return current The return path (common-mode) should be free of any current In the common-mode, each conductor of the pair carries half of the current and the return path carries the sum of both these currents All pairs not under test and any screens, if present, represent the return path for the common-mode voltage Figure A.1 — Differential-mode transmission in a symmetric pair Figure A.2 — Common-mode transmission in a symmetric pair Under ideal conditions, both modes are independent of one another In reality, both modes influence each other Differences in the diameter of the insulation, unequal twisting and different distances of the conductors to the screen are some reasons for the unbalance of a pair The asymmetry is caused by the transverseasymmetry and by the longitudinal asymmetry The transverse asymmetry, TA, is caused by longitudinally distributed unbalances to earth of the capacitance and conductance The longitudinal asymmetry, LA, is caused by the inductance and resistance unbalances between the two conductors of the pair 15 BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) A.2 Unbalance attenuation near end and far end Unbalance attenuation is measured as the logarithmic ratio of the differential-mode power to the commonmode power at the near end and at the far end of the cable The unbalance attenuation is also often referred to as conversion loss: – LCL longitudinal conversion loss; – LCTL longitudinal conversion transfer loss; – TCL transverse conversion loss; – TCTL transverse conversion transfer loss Additionally, the equal level unbalance attenuation at far end is defined as follows: – EL LCTL equal level longitudinal conversion transfer loss; – EL TCTL equal level transverse conversion transfer loss The equal level unbalance attenuation is defined as an output-to-output measurement of the logarithmic ratio of the differential-mode power to the common-mode power or vice versa The output-to-output measurements correspond to the difference of the input-to-output measurement and the respective attenuation: EL LCTL = LCTL − α com EL TCTL = TCTL − α diff (A.1) As it is not a common practice to measure the output-to-output ratios directly, the above differences are utilized to determine the equal level unbalance attenuation The measurement of the common-mode attenuation of balanced cables is prone to error (due to the undefined conditions of the common-mode), and the differential attenuation of the cables shall be measured anyway Therefore, the measurement of the equal level unbalance attenuation far end is limited here to the equal level transverse conversion transfer loss The unbalance attenuation near end or far end is related to the conversion losses as indicated in Table A.1 and Table A.2 Table A.1 — Unbalance attenuation at near end Power fed at the near end into the differential-mode and coupled power measured at the near end in the common-mode TCL Power fed at the near end into the common-mode and coupled power measured at the near end in the differential-mode LCL Table A.2 — Unbalance attenuation at far end Power fed at the near end into the differential-mode and coupled power measured at the far end in the common-mode TCTL Power fed at the near end into the common-mode and coupled power measured at the far end in the differential-mode LCTL Same as TCTL but the measured common-mode power is related to the differentialmode power at the far end (equal level) EL TCTL Table A.3 indicates the common- and differential-mode circuit of the input, and the receive signal for the different types of unbalance attenuation 16 BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) Table A.3 — Measurement set-up Set-up Unbalance attenuation Near end Far end Near end Far end Common-mode circuit Differentialmode circuit Common-mode circuit Differentialmode circuit TCL Receiver Generator – – LCL Generator Receiver - – TCTL – Generator Receiver – LCTL Generator – – Receiver Using the concept of operational attenuation, the generator and receiver on one port of the network are interchangeable without any change in the results Therefore, the measurements of TCL are identical to those of LCL However, the measurement of LCTL or TCTL is inherently a two-port measurement Therefore, the measurements of LCTL are only identical to those of TCTL, if the longitudinal distribution of the unbalances is homogeneous, and if the velocity of propagation of differential- and common-mode signals is identical In this case, the twisted pair corresponds to a reciprocal and impedance symmetrical two-port network If differential-mode transmission is considered, then the loss due to conversion of the differential-mode signal into common-mode signal only is of interest This yields an additional advantage Feeding the power into the differential-mode ports of the balun yields the benefit that the balun then represents a matched generator, which avoids the need of any additional matching pads The differential-mode impedance of multiple pair cables is a well-known design parameter However, the common-mode impedance depends largely upon the design of the cable and is influenced primarily by the insulation thickness, the dielectric constant of the insulation, the proximity and number of neighbouring pairs and finally by the presence of shields Thus the common-mode impedance of nominally 100 Ω cables can vary within the range of 25 Ω to 75 Ω depending on cable construction For STP (individually screened twisted pair) cables, it is approximately 25 Ω For FTP (common screened twisted pair) cables, it is approximately 50 Ω For UTP (unscreened twisted pair) cables, it is approximately 75 Ω The baluns used for measuring generally match the input impedance of the S-parameter test set to the differential-mode impedance of the cable under test (CUT) It is, however, impractical to measure first for each cable the common-mode impedance to match it then to the corresponding common-mode impedance terminations used on the balun Therefore, the terminations at the common-mode port are made throughout in 50 Ω, 60 Ω or 75 Ω for 100 Ω, 120 Ω or 150 Ω nominal impedance cables respectively, to match the common-mode impedance of the balun and the pair under test (cable under test, e.g CUT) For cables with a nominal impedance of 100 Ω, the 50 Ω termination is presented by the input impedance of the network analyser This proceeding entails due to eventual impedance mismatches a variation of the unbalance attenuation due to the reflected signal Thus, a return loss of 10 dB yields an uncertainty of about ± dB A.3 Theoretical background The transverse asymmetry, TA, is caused by longitudinally distributed unbalances to earth of the capacitance and conductance The longitudinal asymmetry, LA, is caused by the inductance and resistance unbalances between the two conductors of the pair 17 BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) Figure A.3 — Circuit of an infinitesimal element of a symmetric pair The unbalance of a symmetric pair can be expressed by Formulae (A.2) and (A.3) (see Figure A.3): TA= (G2 + j × ω × C ) − (G1 + j × ω × C1 ) (A.2) LA= ( R2 + j × ω × L2 ) − ( R1 + j × ω × L1 ) (A.3) The coupling between the differential- and common-mode circuits is expressed by: α u,n = 20 × log 10 Tu,n u,f Tu, n = u, f (A.4) u,f U com (A.5) U diff With the definition of an unbalance impedance: Z= unbal Z diff × Z com (A.6) The terms for the unbalance coupling functions represent, in principle, the same coupling transfer functions as for the coupling through screens or the coupling between lines (crosstalk) Hence, they can be formally written down as: 1 T u, n = × × Z unbal x = ∫x =0 −( γ diff  TA( x ) × Z  unbal + LA( x ) × e  −γ × 1 T u, f = × × e com × Z unbal x = ∫x =0 + γ com ) × x × dx −( γ diff  TA( x ) × Z  unbal − LA( x ) × e  − γ com ) × x (A.7) × dx (A.8) When γ ×  ≈ 0, the unbalance coupling functions can be separated into the following formulae for the unbalances of the primary parameters: 18 BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) Z unbal = TConductance Z unbal = TResistance × ΔG × ΔR = TCapacitance = TInductance Z unbal Z unb al × ω × ΔC (A.9) × ω × ΔL Formulae (A.7) and (A.8) represent, in principle, the same coupling transfer functions compared to the coupling through the screen or the crosstalk between lines The integral can only be solved if the distribution of the capacitance, resistance and inductance unbalances along the cable length are known For longitudinally constant unbalances, the transfer function gives comparable results as for the coupling through cable screens, or the crosstalk between lines  Tu, n=  TA ⋅ Z unbal ± LA  ⋅ ⋅ ⋅ Sn   Z unbal u, f f (A.10) The phase effect, when summing up the infinitesimal couplings along the line is expressed by the summing function S When the cable attenuation is neglected S can be expressed by the following formula: Sn f sin( β diff ± β com ) × ( β diff   −  j ⋅( β diff ×e  ± β com  ± β com ) × ) × 2  (A.11) For high frequencies, the asymptotic value becomes: Sn = f ( β diff ± β com ) ×  (A.12) and for low frequencies, the summing function becomes: Sn → (A.13) f In practice, symmetric pairs have small systematic couplings together with random couplings Thus, Tu,n increases by approximately 15 dB per decade Figure A.4 shows the calculated coupling transfer function for a cable length of 100 m and a capacitance unbalance to earth, which consists of a constant part of 0,4 pF/m and a random ± 0,4 pF/m longitudinal variation The relative dielectric permittivity of the differential- and common-mode circuit is here assumed to be 2,3 The magnetic coupling and the cable attenuation have been neglected Figure A.5 shows the measured coupling transfer function for a length of 100 m of a Twinax 1) cable with 105 Ω differential-mode impedance, and with a braided screen The conductors are PE insulated and have an inner PE sheath The resultant velocity difference is, therefore, nearly zero 1) Twinax is an example of a suitable product available commercially This information is given for the convenience of users of this document and does not constitute an endorsement of this product 19 BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) Figure A.4 — Calculated coupling transfer function for a capacitive coupling of 0,4 pF/m and random ± 0,4 pF/m (  = 100 m; εr1 = εr2 = 2,3) Figure A.5 — Measured coupling transfer function of 100 m Twinax 105 Ω 20 BS EN 50289-1-9:2017 EN 50289-1-9:2017 (E) Bibliography [1] KADEN H., Die elektromagnetische Schirmung in der Fernmelde- und Hochfrequenz-technik Springer Verlag, 1950 [2] SCHMID H., Theorie und Technik der Nachrichtenkabel Hüthig Verlag, 1976 [3] HÄHNER T., MUND B., EMC performance of balanced (symmetrical) cables; Colloquium on screening effectiveness measurements, Savoy Place London, May 1998 Reference No, 1998, pp 452 [4] HÄHNER T., MUND B., Test Method for Screening and Balance of Communication Cables; 13th international Zurich EMC Symposium, February 16-18 1999 [5] EN 60512-28-100, Connectors for electronic equipment - Tests and measurements - Part 28-100: Signal integrity tests up to 000 MHz on IEC 60603-7 and IEC 61076-3 series connectors - Tests 28a to 28g (IEC 60512-28-100) [6] ITU-G 117, Transmission aspects of unbalance about earth 21 This page deliberately left blank This page deliberately left blank NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW British Standards Institution (BSI) BSI is the national body responsible for preparing British Standards and other standards-related publications, information and services BSI is incorporated by Royal Charter British Standards and other standardization products are published by BSI Standards Limited About us Reproducing extracts We bring together business, industry, government, consumers, innovators and others to shape their combined experience and expertise into standards -based solutions For permission to reproduce content from BSI publications contact the BSI Copyright & Licensing team The knowledge embodied in our standards has been carefully assembled in a dependable format and refined through our open consultation process 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