1、BRITISH STANDARD AEROSPACE SERIES Cables, electrical, aircraft use Test methods Part 805: Characteristic impedance The European Standard EN 3475-805:2002 has the status of a British Standard ICs 49.060 BS EN 3475-80512002 WkNb A%“ U- rn% E rn NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY
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6、Date I Comments O BSI 25 June 2002 ISBN O 580 39909 5 EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 3475-805 June 2002 ICs 49.060 English version Aerospace series - Cables, electrical, aircraft use - Test methods - Part 805: Characteristic impedance Srie arospatiale - Cbles lectriques usage a
7、ronautique - Mthodes dessais - Partie 805: Impdance caractristique Luft- und Raumfahrt - Elektrischen Leitungen fr Luftfahrt Verwendung - Prfverfahren - Teil 805: Wellenwiderstand This European Standard was approved by CEN on 20 January 2002 CEN members are bound to comply with the CENKENELEC Intern
8、al 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 Management Centre or to any CEN member. T
9、his European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official versions. CEN members are th
10、e national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION EUROPISCHES KOMITEE FR NORMUNG
11、COMIT EUROPEN DE NORMALISATION Management Centre: rue de Stassart, 36 B-1050 Brussels O 2002 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 34758052002 E EN 3475-80512002 (E) Foreword This document (EN 3475-805:2002) has been prep
12、ared by the European Association of Aerospace Manufacturers (AECMA). After enquiries and votes carried out in accordance with the rules of this Association, this Standard has received the approval of the National Associations and the Official Services of the member countries of AECMA, prior to its p
13、resentation to CEN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by December 2002, and conflicting national standards shall be withdrawn at the latest by December 2002. According to the CENKENELEC
14、 Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden,
15、 Switzerland and the United Kingdom. 2 EN 3475-80512002 (E) 1 Scope This standard specifies methods for measuring the characteristic impedance of a cable. It shall be used together with EN 3475-100. 2 Normative references This European Standard incorporates by dated or undated reference provisions f
16、rom other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amend
17、ment or revision. For undated references the latest edition of the publication referred to applies. EN 3475-1 O0 Aerospace series - Cables, electrical, aircraft use - Test methods - Part 100: General EN 3475-804 Aerospace series - Cables, electrical, aircraft use - Test methods - Part 804: Velocity
18、of propagation 3 Preparation of specimens These shall be stripped and prepared for connection to the measuring device. 4 Methods 4.1 Length of sample: 2 3 m Equipment: impedance measuring bridge Frequency: as indicated in the product standard Measuring principle: the input impedance of the sample sh
19、all be measured first with its end in open circuit (Z,) and then with its end in short circuit (Z,). The characteristic impedance of the cable shall be calculated from these two measurements using the following formula: Method A: measurement with impedance bridge on coaxial cable zc = Jzco zcc 4.2 T
20、he measurement shall be taken using the same equipment and on the same sample as for the velocity of propagation, connected in the same way according to EN 3475-804. The characteristic impedance Z, of the cable shall be calculated from the reflection coefficient shown on the oscilloscope screen usin
21、g the formula: Method B: reflectometer measurement on coaxial cable I+ P zc = zo - 1-P so that Z, = value in ohms of characteristic impedance in common mode. 3 EN 3475-80512002 (E) Measurement of p shall be taken one metre from the cable input (t/3). 7 Mismatch at cable input Referencelevel - - - -
22、for precision coaxial air line - Open circuit at free end of cable Figure 1 4.3 The characteristic impedance of the cable at the specified frequency shall be derived from the input impedance of a length of cable when its far end is put in open and short circuit, using the following formula: Method C
23、: shielded symmetric cable measurement Z, and Z, shall be derived from the reflection coefficients pco and pcc at the input of the length of cable, using the following formulas: In which Zb is the characteristic impedance of the test set up at the place where the cable is connected. 4.3.1 Apparatus
24、- A vectoriel network analyser able to make reflexion measurement on one port devices - A balun with: 1) coaxial port matched to the characteristic impedance Z, of the network analyser; 2) symmetrical port with characteristic impedance Zb = 75 Q. See figure 2. All the screens and all the conductors
25、other than those making of the equipment under test are earthed Figure 2 4 EN 3475-80512002 (E) 4.3.2 Measurement procedure Calibration The scattering parameters of the balun shall be derived from the reflection coefficients measured at the coaxial port of the balun when its symmetrical port is load
26、ed as it follows: - open circuit p sym CO - short circuit p sym cc - matched Zb = 75 Q p sym ad by the following formulas: sI1 = p sym ad (4) (5) 2 p sym ad -psym cc- psym CO p sym cc - p sym co szz = sI2 . sZ1 = (p sym ad - p sym cc) (1 - sZ2) (6) 4.3.3 Measurements The values of the reflection coe
27、fficients at the coaxial port of the balun shall be measured with the symmetrical port loaded by the length of cable to be measured, when its far end is as it follows: - open circuit PICO - short circuit Pcc The values of the reflection factor at the input of the cable shall be derived from the abov
28、e values by the following formulas: Pcc - SI1 s22 (Pcc - SI 1) + SI2 S21 &c = PICO - SI1 22(Pcc-11) + S12S21 &o = Zco and Zcc are derived from the formulas given in (2) and (3). Zc is derived from the formula given in (1). 5 Req u i remen t The characteristic impedance shall be within the limits ind
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