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1、TECHNICAL REPORT IEC TR 62064 First edition 1999-07 Radio-frequency cables Relationship between surface transfer impedance and screening attenuation (A background to the recommended limits contained in IEC 61196-1, clause 14) Cblages pour frquences radiolectriques Relation entre limpdance de transfe
2、rt en surface et laffaiblissement dcran Reference number IEC/TR 62064:1999(E) Copyright International Electrotechnical Commission Provided by IHS under license with IECLicensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale, 03/06/2007 06:27:50 MSTNo reproduction or networking permit
3、ted without license from IHS -,-,- Numbering As from 1 January 1997 all IEC publications are issued with a designation in the 60000 series. Consolidated publications Consolidated versions of some IEC publications including amendments are available. For example, edition numbers 1.0, 1.1 and 1.2 refer
4、, respectively, to the base publication, the base publication incorporating amendment 1 and the base publication incorporating amendments 1 and 2. Validity of this publication The technical content of IEC publications is kept under constant review by the IEC, thus ensuring that the content reflects
5、current technology. Information relating to the date of the reconfirmation of the publication is available in the IEC catalogue. Information on the subjects under consideration and work in progress undertaken by the technical committee which has prepared this publication, as well as the list of publ
6、ications issued, is to be found at the following IEC sources: IEC web site* Catalogue of IEC publications Published yearly with regular updates (On-line catalogue)* IEC Bulletin Available both at the IEC web site* and as a printed periodical Terminology, graphical and letter symbols For general term
7、inology, readers are referred to IEC 60050: International Electrotechnical Vocabulary (IEV). For graphical symbols, and letter symbols and signs approved by the IEC for general use, readers are referred to publications IEC 60027: Letter symbols to be used in electrical technology, IEC 60417: Graphic
8、al symbols for use on equipment. Index, survey and compilation of the single sheets and IEC 60617: Graphical symbols for diagrams. * See web site address on title page. Copyright International Electrotechnical Commission Provided by IHS under license with IECLicensee=IHS Employees/1111111001, User=l
9、istmgr, listmgr Not for Resale, 03/06/2007 06:27:50 MSTNo reproduction or networking permitted without license from IHS -,-,- TECHNICAL REPORT IEC TR 62064 First edition 1999-07 Radio-frequency cables Relationship between surface transfer impedance and screening attenuation (A background to the reco
10、mmended limits contained in IEC 61196-1, clause 14) Cblages pour frquences radiolectriques Relation entre limpdance de transfert en surface et laffaiblissement dcran PRICE CODE IEC 1999 Copyright - all rights reserved No part of this publication may be reproduced or utilized in any form or by any me
11、ans, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Electrotechnical Commission3, rue de Varemb Geneva, Switzerland Telefax: +41 22 919 0300e-mail: inmailiec.ch IEC web site http:/www.iec.ch G For price, see current cat
12、alogue Commission Electrotechnique Internationale International Electrotechnical Commission Copyright International Electrotechnical Commission Provided by IHS under license with IECLicensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale, 03/06/2007 06:27:50 MSTNo reproduction or net
13、working permitted without license from IHS -,-,- 2 TR 62064 IEC:1999(E) CONTENTS Page FOREWORD . 3 Clause 1Scope 4 2General 4 3Correlation between measured screening attenuation as and measured surface transfer impedances at 30 MHz and 300 MHz 6 4Recommended limits for surface transfer impedance and
14、 screening attenuation . 6 5Reference documents 14 Copyright International Electrotechnical Commission Provided by IHS under license with IECLicensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale, 03/06/2007 06:27:50 MSTNo reproduction or networking permitted without license from IH
15、S -,-,- TR 62064 IEC:1999(E) 3 INTERNATIONAL ELECTROTECHNICAL COMMISSION _ RADIO-FREQUENCY CABLES RELATIONSHIP BETWEEN SURFACE TRANSFER IMPEDANCE AND SCREENING ATTENUATION (A background to the recommended limits contained in IEC 61196-1, clause 14) FOREWORD 1)The IEC (International Electrotechnical
16、Commission) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end a
17、nd in addition to other activities, the IEC publishes International Standards. Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International, governmental and non-governmental organizati
18、ons liaising with the IEC also participate in this preparation. The IEC collaborates closely 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 the IEC on technical
19、 matters express, as nearly as possible, an international consensus of opinion on the relevant subjects since each technical committee has representation from all interested National Committees. 3)The documents produced have the form of recommendations for international use and are published in the
20、form of standards, technical reports, technical specifications or guides and they are accepted by the National Committees in that sense. 4)In order to promote international unification, IEC National Committees undertake to apply IEC International Standards transparently to the maximum extent possibl
21、e in their national and regional standards. Any divergence between the IEC Standard and the corresponding national or regional standard shall be clearly indicated in the latter. 5)The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any equipment decl
22、ared to be in conformity with one of its standards. 6) Attention is drawn to the possibility that some of the elements of this technical report may be the subject of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights. The main task of IEC technical com
23、mittees is to prepare International Standards. However, a technical committee may propose the publication of a technical report when it has collected data of a different kind from that which is normally published as an International Standard, for example “state of the art“. Technical reports do not
24、necessarily have to be reviewed until the data they provide are considered to be no longer valid or useful by the maintenance team. IEC 62064, which is a technical report, has been prepared by subcommittee 46A: Coaxial cables, of IEC technical committee 46: Cables, wires, waveguides, R.F. connectors
25、, and accessories for communication and signalling. The text of this technical report is based on the following documents: Enquiry draftReport on voting 46A/330/CDV46A/348/RVC Full information on the voting for the approval of this technical report can be found in the report on voting indicated in t
26、he above table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 3. This document which is purely informative is not to be regarded as an International Standard. A bilingual version of this technical report may be issued at a later date. Copyright International Elect
27、rotechnical Commission Provided by IHS under license with IECLicensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale, 03/06/2007 06:27:50 MSTNo reproduction or networking permitted without license from IHS -,-,- 4 TR 62064 IEC:1999(E) RADIO-FREQUENCY CABLES RELATIONSHIP BETWEEN SURFA
28、CE TRANSFER IMPEDANCE AND SCREENING ATTENUATION (A background to the recommended limits contained in IEC 61196-1, clause 14) 1 Scope This technical report describes the valuable background material used during the revision of IEC 61196-1, clause 14, guidance for surface transfer impedance and screen
29、ing attenuation limits for flexible r.f. cables. In this report the relationship between surface transfer impedance (ZT) and screening attenuation (as) is given, also measurements of ZT and as are provided to show the correlation of mean scanning attenuation between 200 MHz and 500 MHz and ZT at bot
30、h 30 MHz and 300 MHz. The sensitivity of as and the relative velocity difference between the inner and outer system is shown, also the need for the cable data sheet to show the as values in a standardized form v/v = 10 % and the characteristic impedance of the outer system is 150 . It is also shown
31、that a relative velocity difference change from 10 % to 40 % gives an improvement of 12 dB in screening attenuation. 2 General At high frequencies when the surface transfer impedance ZT and effective transfer impedance TFTE fn, ZZZ=, and increases 6 dB per octave, its relation to the screening atten
32、uation as is frequency independent and can be written as (see also figure 1): n f 10 n f s log20Ta=(1) r1r221 oT 10 12 21 T 10 log20log20 = = ZZ cZ v l v l ZZ Z (2) and 11 22n f n f/ / ZU ZU T= where lis the length of the cable under test; Tn,fare the coupling transfer functions; nfor the near end a
33、nd f for the far end; Z1is the characteristic impedance of the cable; Z2is the impedance of the outer circuit; r1is the cable dielectric permittivity; r2is the permittivity of the outer circuit; cois the velocity of light in vacuum; v1is the propagation velocity of the inner circuit; Copyright Inter
34、national Electrotechnical Commission Provided by IHS under license with IECLicensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale, 03/06/2007 06:27:50 MSTNo reproduction or networking permitted without license from IHS -,-,- TR 62064 IEC:1999(E) 5 v2is the propagation velocity of th
35、e outer circuit; ZFis the capacitive coupling impedance; ZTis the surface transfer impedance; fn, TE Z is the effective transfer impedance. l E1 Z1 Z2 Z2 Z1 D1 Z1v1 Z2v2 U1n U2n U2f U1f + (1) (2) IEC 884/99 (1) The inner circuit, cable under test. (2) The outer circuit, formed by test line or cylind
36、er or the outer environment as in the absorbing clamp method. Figure 1 Concept of screening measurement set-ups When the capacitive coupling impedance ZF is present (spaces in the outer conductor), ZT shall be substituted by ZTE. “+“ sign is for the near end and “ sign for the far end. Z1 and Z2 are
37、 the impedances of the inner and outer system and v1 and v2 the corresponding velocities. Screening attenuation as is a reliable measure of screening efficiency when the frequency is constant. This is true when ZT or ZTE increases 6 dB/octave and the following criterion is fulfilled: r2r1 o n f l(4)
38、 where o is the wave length in free space. At lower frequencies when l is smaller than that found from (4) the coupling attenuation is: 21 TF 10 n f 10 n f s 2 )( log20log20 ZZ lZZ TA =(5) More detailed information on the above equations is given in the IEC 61917. Copyright International Electrotech
39、nical Commission Provided by IHS under license with IECLicensee=IHS Employees/1111111001, User=listmgr, listmgr Not for Resale, 03/06/2007 06:27:50 MSTNo reproduction or networking permitted without license from IHS -,-,- 6 TR 62064 IEC:1999(E) 3 Correlation between measured screening attenuation as
40、 and measured surface transfer impedances at 30 MHz and 300 MHz ZT and as were measured using the same cable construction. Figures 2, 3 and 4 show the correlation between as (mean value between 200 MHz and 500 MHz) and the ZT values correspondingly at 30 MHz and 300 MHz. In figure 5, typical ZT curv
41、es are shown. For single and double braided outer conductors the 6 dB/octave increase is reached at 30 MHz but for foil-braid constructions at 30 MHz the ZT can still be decreasing. The effect of this can be clearly seen when comparing the test results in figures 2, 3 and 4 for the foil-braid cables
42、. The correlation between as and ZT (30 MHz) is poor, but much better between as and ZT (300 MHz). For single and double braided cables the correlation is equally good for 30 MHz and 300 MHz. The increase in the values of ZT which should have been 10 fold (20 dB) is somewhat lower. The full 6 dB/oct
43、ave increase in ZT between 30 MHz and 300 MHz has not been reached for all single and double braided cables. The ZT(as) correlation line slope from equations (1) and (2) is 20 dB/decade. One reason for the spread in correlation is the strong effect of the velocity differences v2 v1 on the as value.
44、To demonstrate this, two lines are shown for 40 % and one for 10 % relative velocity difference ( |v2 v1 |/v1). Also, the outer circuit impedance has been altered from 300 to 150 . Other reasons for the widespread of the correlation points are that only the cable construction has been kept the same,
45、 but the tested samples are different. It is impossible to use the same samples in ZT and as measurements because of the required difference in length of the cable under test (CUT). Even if the samples had been the same, a difference of 6 dB would exist when the CUT is removed from the test fixture
46、and then remounted. As shown above, the screening attenuation as is dependent on the outer circuit propagation velocity and to a lesser extent on the impedance, and decreases rapidly when the velocities v2 and v1 approach each other. For these reasons it has been recommended that as shall also be gi
47、ven in standardized conditions asn where the outer circuit velocity differs by 10 % from the inner circuit velocity, and the outer circuit impedance is 150 . It can be seen from figures 2 and 3 that the difference is about 10 dB. A drop in relative velocity difference from 40 % to 10 % causes a decr
48、ease of 12 dB in as. A decrease in impedance of 50 % causes an increase in as of 3 dB. The values of the standardized condition 10 % relative velocity difference / 150 have been shown to be that of a typical cable tray surrounding. Normally the measurement conditions of the absorbing clamp set-up gives approximately a 10 dB improvement value for as. Figures 5 and 6 show typical test results for single braided, double braided and foil-braid outer conductor construct