1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 + TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU02/4%#4)/.G0G0!).34G0G0).4%2&%2%.#%-%4(/$G0G0&/2G0G0-%!352).2!$)/G13&2%15%.#9G0G0).$5#%$G0G0./)3%/.G0G04%,%#/-5.)#!4)/.3G0G00!)23)45G134G0G0RecommendationG0G0+ (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recomm
2、endation K.24 was published in Volume IX of the Blue Book. This file is an extract from theBlue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are identical to the Blue Book version and copyright conditions remain u
3、nchanged (see below).2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part of this publication may be reproduced or utilized in any form or by
4、any means, electronic ormechanical, including photocopying and microfilm, without permission in writing from the ITU.Volume IX - Rec. K.24 1Recommendation K.24Volume IX - Rec. K.24METHOD FOR MEASURING RADIO-FREQUENCYINDUCED NOISE ON TELECOMMUNICATIONS PAIRS(Melbourne, 1988)1 Purpose of this Recommen
5、dationThis Recommendation is intended to standardize the method for measuring radio-frequency induced noise thatmay cause degradation of equipment performance and transmission quality. Standardization of the method formeasuring induced noise makes possible the international standardization of the qu
6、ality of the telecommunicationsystem.2 ScopeThis Recommendation considers measurement methods for radio-frequency induced noise at anytelecommunication pair. Locations for measurement are both the cable entry into a building and the interface point of aterminal equipment.The frequency range to be co
7、nsidered is 10 kHz to 30MHz.Note Above 30 MHz, the technical problems of making measurements have not been solved and are thereforestill under study.3 Circuits for measuring radio-frequency induced noise voltage1) Measured mode of induced noise voltageBoth transverse and longitudinal voltages should
8、 be measured.2) Measured condition of telecommunication lineMeasurements should be made with all telecommunications equipment disconnected at measuring end andwith a measurement termination network.i) Termination network for measurementsMeasurements should be made at both the cable entry point into
9、the subscribers premises and at theterminal equipment point. In the measurement, a T network shown in Figure 1/K.24 should be used.The longitudinal conversion loss of the T network should be at least 10 dB higher than the value ofthe LCL for the cable type to be measured (e.g. 60 dB cable requires 7
10、0 dB measurement terminationnetwork).Note Values of Rxand Ryare under consideration. Administrations and RPOAs are requested tomake measurements at both sets of values indicated in Figure 1/K.24.ii) Reference earthing pointEither of two reference earthing points may be used. In order of preference t
11、hey are: 1) the screen ofthe cable, or 2) the primary protection ground terminal, protective earth, or nearby grounded metalwork. Since it affects the result, the reference earthing point used for a measurement should be stated.Note For transverse measurements, a connection to a reference point may
12、not be required, but caremust be taken with the capacitance of the measurement equipment to ground. This may be done byusing battery powered measuring equipment. An isolating transformer for mainspowered equipment,or a balun termination network, must be used when measuring metallic transverse voltag
13、e.2 Volume IX - Rec. K.24iii) Termination network to use at the central officeOn inside house wire (such as the S/T interface line of ISDN) it is important to terminate the far endof the cable. However, when measuring at the entry point of the local network into the customerspremises (such as the 2-
14、wire interface to NT1 of ISDN), it is not important to have a termination atthe far end if the cable length exceeds 1 km. Less than 1 km, it may still be possible to makemeasurements without terminating the far end, depending on the frequency of the interfering signaland the make-up of the local net
15、work.3) Detector typeThe detector shall have fundamental characteristics as defined in Section 1 of CISPR specification for radiointerference measuring apparatus and measurement method, CISPR publication No. 16, 1987.4) Bandwidth of measurementThe bandwidth of measurement shall have fundamental char
16、acteristics as defined in Section 1 of CISPRspecification for radio interference measuring apparatus and measurement method, CISPR publication No.16, 1987.Improvements in narrowing the bandwidth and the standardization of appropriate measuring equipmentneeds further study in cooperation with CISPR (
17、International Special Committee on Radio Interference.).5) Electric field immunity of measurement equipmentThe test equipment should have an overall immunity to electromagnetic fields in accordance with CISPRpublication 16. Adequate accuracy should be provided for extending the use of the equipment to locationswith field strengths above 3 V/m to 10 V/m.
