1、BRITISH STANDARD BS EN 60512-25-7:2005 Connectors for electronic equipment Tests and measurements Part 25-7: Test 25g Impedance, reflection coefficient and voltage standing wave ratio (VSWR) The European Standard EN 60512-25-7:2005 has the status of a British Standard ICS 31.220.10 BS EN 60512-25-7:
2、2005 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 18 April 2005 BSI 18 April 2005 ISBN 0 580 45822 9 National foreword This British Standard is the official English language version of EN 60512-25-7:2005. It is identical with IEC 60512-25-
3、7:2005. The UK participation in its preparation was entrusted to Technical Committee EPL/48/2, Connectors for electronic equipment, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standar
4、ds which implement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This p
5、ublication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible interna
6、tional/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the EN tit
7、le page, pages 2 to 35 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEAN STANDARD EN 60512-25-7 NORME EUROPENNE EUROPISCHE NORM March 2005 CENELEC European Committee fo
8、r Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members
9、. Ref. No. EN 60512-25-7:2005 E ICS 31.220.10 English version Connectors for electronic equipment Tests and measurements Part 25-7: Test 25g Impedance, reflection coefficient and voltage standing wave ratio (VSWR) (IEC 60512-25-7:2004) Connecteurs pour quipements lectroniques Essais et mesures Parti
10、e 25-7: Essai 25g Impdance, coefficient de rflexion et rapport dondes stationnaires en tension (VSWR) (CEI 60512-25-7:2004) Steckverbinder fr elektronische Einrichtungen - Mess- und Prfverfahren Teil 25-7: Prfung 25g Impedanz, Reflexionskoeffizient und Spannungsstehwellenverhltnis (IEC 60512-25-7:20
11、04) This European Standard was approved by CENELEC on 2005-03-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographi
12、cal references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a
13、CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, I
14、reland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. Foreword The text of document 48B/1479/FDIS, future edition 1 of IEC 60512-25-7, prepared by SC 48B, Connectors, of IEC TC 48, Electromechani
15、cal components and mechanical structures for electronic equipment, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 60512-25-7 on 2005-03-01. The following dates were fixed: latest date by which the EN has to be implemented at national level by publication of an ident
16、ical national standard or by endorsement (dop) 2005-12-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2008-03-01 _ Endorsement notice The text of the International Standard IEC 60512-25-7:2004 approved by CENELEC as a European Standard without any m
17、odification. _ Page2 EN60512257:2005 CONTENTS 1 Scope and object4 2 Terms and definitions .4 3 Test resources5 3.1 Equipment.6 3.2 Fixture.6 4 Test specimen 8 4.1 Description 8 5 Test procedure .8 5.1 Time domain .8 5.2 Frequency domain .10 6 Details to be specified.11 7 Test documentation 12 Annex
18、A (normative) Measurement system rise time.13 Annex B (informative) Determination of the near end and far end of the specimen 16 Annex C (informative) Calibration standards and test board reference traces17 Annex D (informative) Interpreting TDR impedance graphs.22 Annex E (informative) Terminations
19、 Electrical25 Annex F (informative) Practical guidance variable rise time28 Annex G (informative) Printed circuit board design considerations for electronics measurements 29 Annex H (informative) Test signal launch hardware 33 Figure A.1 Example of rise-time measurement points .13 Figure A.2 Example
20、 of TDR output; 2 curves (different rise times) and start and stop specimen points14 Figure A.3 Example of analyzer output, impedance versus log frequency plot15 Figure C.1 Typical mother-board test fixture .18 Figure C.2 Typical daughter-board test fixture 18 Figure C.3 Example of near-end referenc
21、e trace.21 Figure D.1 Example of an impedance profile of connector using a measurement system rise time of 35 ps.23 Figure D.2 Example of impedance profiles of cable at the rise time of 35 ps and 1 ns .24 Figure E.1 Single-ended terminations .26 Figure E.2 Differential (balanced) terminations .27 Fi
22、gure G.1 Microstrip (a) and stripline (b) geometries .29 Figure G.2 Buried microstrip geometry30 Table 1 Additional measurement system rise time (including fixture and filtering)9 Page3 EN60512257:2005 CONNECTORS FOR ELECTRONIC EQUIPMENT TESTS AND MEASUREMENTS Part 25-7: Test 25g Impedance, reflecti
23、on coefficient, and voltage standing wave ratio (VSWR) 1 Scope and object This part of IEC 60512 applies to interconnect assemblies, such as electrical connectors and cable assemblies, within the scope of IEC technical committee 48. This standard describes test methods to measure impedance, reflecti
24、on coefficient, and voltage standing wave ratio (VSWR) in the time and frequency domains. NOTE These test methods are written for test professionals who are knowledgeable in the electronics field and are trained to use the referenced equipment. Because the measurement values are heavily influenced b
25、y the fixturing and equipment, this method cannot describe all of the possible combinations. The major equipment manufacturers provide application notes for a more in-depth technical description of how to optimize the use of their equipment. It is imperative that the referencing document include the
26、 necessary description and sketches for the test professional to understand how to set up and perform the requested measurements. 2 Terms and definitions For the purposes of this document, the following terms and definitions apply. 2.1 measurement system rise time rise time measured with the fixture
27、 in place, without the specimen, and with filtering (or normalization). Rise time is typically measured from 10 % to 90 % levels 2.2 specimen environment impedance impedance presented to the signal conductors by the fixture. This impedance is a result of transmission lines, termination resistors, at
28、tached receivers or signal sources, and fixture parasitics 2.3 reflection coefficient ratio of the reflected to incident voltages at any given point. The reflection coefficient is given by = incident reflected V V= O L O L Z Z Z Z + = s 11where Z Lis the fixture or specimen impedance and Z Ois the s
29、pecimen environment impedance. NOTE In the time domain, the reflection coefficient symbol typically used is rho (), while gamma () is used for frequency-domain measurements. Page4 EN60512257:2005 2.4 impedance total opposition that a circuit offers to the flow of alternating current at a particular
30、frequency. It is a combination of the resistance (R) and reactance (X) measured in ohms ( ). The equation for impedance as a function of s-parameters is: 11 11 0 1 1 s s Z Z + = = R + jX = () () + 1 1 0 Z 2.5 voltage standing wave ratio VSWR ratio of the maximum magnitude of the voltage on a line to
31、 the minimum magnitude at any given point. VSWR can be expressed by the following equations: 2.6 scattering parameter (s-parameter) s 11reflection coefficient at the input port of the device under test, defined as the ratio of the reflected voltage to the incident voltage 2.7 termination (electronic
32、s usage) impedance connected to the end of a transmission line, typically to minimize reflected energy on the line 2.8 step amplitude voltage difference between the 0 % and 100 % levels, ignoring overshoot and undershoot 3 Test resources Care should be taken when establishing the equivalence between
33、 time- and frequency-domain measurements. The relationship between the two is complex, and the application of bandwidth = (0,35/rise time) should not be used without further computations and understanding. refl inc refl inc min maxVSWR V V V V V V + = = ( ) () + =11VSWR Page5 EN60512257:2005 3.1 Equ
34、ipment 3.1.1 Time domain 3.1.1.1 A Time Domain Reflectometer (TDR) is preferred as the measurement accuracy is improved with the use of a step function, although an oscilloscope and pulse generator may be used. A network analyzer may be used with FFT (Fast Fourier Transform) software. NOTE The test
35、professional should be aware of limitations of any mathematical operation performed by an instrument (for example, FFT). 3.1.1.2 Variable rise time A means should be provided for varying the signal rise time if required. This may be included within the test equipment itself, or possibly through addi
36、tional filtering or software. NOTE The test professional should be aware of limitations of any mathematical operation performed by an instrument or software; for example, normalization or filtering. 3.1.1.3 Differential measurements The test equipment shall have the capability to perform differentia
37、l measurements directly, or provisions shall be made to calculate the impedance from multiple single-ended measurements. 3.1.2 Frequency domain 3.1.2.1 A vector network analyzer or impedance analyzer shall be used. NOTE 1 The test professional should be aware of the frequency limitations of the fixt
38、ure. NOTE 2 The test professional should be aware of any limitations of any mathematical functions performed (for example, normalization, inverse FFT, or software filtering.) 3.1.2.2 Differential measurements For differential measurements, a network analyzer and baluns may be used. NOTE The test pro
39、fessional should be aware of the electrical characteristics of the baluns that become part of the test fixture and can significantly affect the measurement. 3.2 Fixture The fixture(s) shall allow for enough measurements throughout the specimen so that variations in geometries, materials, transmissio
40、n paths, etc. may be demonstrated and provide a representative sampling of specimen performance. NOTE The fixture geometry and materials will impact the measurements due to the fixture parasitics. Usually, the intended use of the product dictates the most meaningful way to fixture it. 3.2.1 Specimen
41、 environment impedance Unless otherwise specified in the referencing document, the specimen environment impedance shall match the impedance of the test equipment. Typically this will be 50 for single-ended measurements and 100 for differential measurements. Page6 EN60512257:2005 3.2.2 Terminations W
42、hen using termination resistors, care should be taken to minimize the parasitic reactances of the terminators over the range of test frequencies (see Annex E). 3.2.3 Calibration features See Annex C for calibration and reference traces. NOTE The term “calibration” used in this document is not to be
43、confused with the periodic factory equipment calibration. Calibration is used in the sense of characterizing the fixture so that when the “fixture plus specimen” measurement is taken, the characteristics of the specimen alone can be accurately determined. 3.2.3.1 Time domain The fixture shall includ
44、e features such that the near and far ends of the specimen may be determined in time (see Annex B). The calibration plane should be as close to the specimen as possible. When the fixture includes a pc board with line traces connecting two connectors, it shall have a reference trace(s) that will allo
45、w the measurement system rise time to be measured. The reference trace shall have starting points and end points at the same location as the DUT (device under test) starting point and end point. This is because the reference trace(s) length shall be the same as the pc board traces. 3.2.3.2 Frequency
46、 domain It is necessary to include fixture features that will allow for the open, short, and load measurements to be taken. This may be accomplished by one of two methods. Firstly, provide reference traces that include the open, load and short standards. Secondly, provide an interface where these st
47、andards can be applied directly to the end of the fixture and immediately before the input plane of the device under test. When using the open/short method, the fixture shall include features such that measurements may be conducted with the far end of the driven line both open-circuited and short-ci
48、rcuited. NOTE Other calibration techniques (such as through-reflect-line) may be used. The fixture should incorporate features appropriate to that (these) calibration method(s). 3.2.4 Single-ended The fixture shall allow one signal line to be driven at a time. The far end of the driven line shall be
49、 terminated in the specimen environment impedance (typically 50 ). It is recommended that a length of transmission line be added after the sample that has a propagation delay greater than twice the measurement system rise time. Unless otherwise specified in the referencing document, a 1:1 signal to ground ratio shall be used; designated ground lines shall be
