BS 6513-2-1984 Wideband cabled distribution systems - Methods of measurement《宽带电缆配电系统 第2部分 测量方法》.pdf

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1、BRITISH STANDARD BS 6513-2: 1984 Incorporating Amendment No. 1 Wideband cabled distribution systems Part 2: Methods of measurement UDC 621.396.44:654.195.2+621.397.132.122:654.197.2BS 6513-2:1984 This British Standard, having been prepared under the directionof the Electronic Equipment Standards Com

2、mittee,was published underthe authority of the BoardofBSI and comes intoeffecton 31 July 1984 BSI 01-2000 The following BSI references relate to the work on this standard: Committee reference EEL/25 Draft for comment 83/23518 DC ISBN 0 580 13909 3 Committees responsible for this British Standard The

3、 preparation of this British Standard was entrusted by the Electronic Equipment Standards Committee (EEL/-) to Technical Committee EEL/25 upon which the following bodies were represented: British Broadcasting Corporation British Radio and Electronic Equipment Manufacturers Association British Teleco

4、mmunications Department of Trade and Industry, Directorate of Radio Technology Institution of Electronic and Radio Engineers Radio, Electrical and Television Retailers Association The following bodies were also represented in the drafting of the standard, through subcommittees and panels: British Ki

5、nematograph, Sound and Television Society Cable Television Association of Great Britain Consumer Standards Advisory Committee of BSI Consumers Association Electric Cable Makers Confederation Electronic Components Industry Federation Electronic Engineering Association Independent Broadcasting Authori

6、ty Institution of Electrical Engineers Society of Cable Television Engineers Telecommunication Engineering and Manufacturing Association Amendments issued since publication Amd. No. Date of issue Comments 5065 December 1985 Indicated by a sideline in the marginBS 6513-2:1984 BSI 01-2000 i Contents P

7、age Committees responsible Inside front cover Foreword iii Section 1. General 1.1 Scope 1 1.2 Definitions, designations and abbreviations 1 Section 2. Methods of measurement applicable to both television and f.m. sound radio signals 2.1 Mutual isolation between system outlets 1 2.2 Amplitude/frequen

8、cy response within a channel 2 2.3 Single intermodulation product 5 2.4 Signal levels 8 2.5 Radiation from components 8 2.6 Carrier-to-noise ratio 18 Section 3. Methods of measurement applicable to television signals only 3.1 Chrominance-luminance gain and delay inequalities 21 3.2 Composite beat 23

9、 3.3 Two signal cross-modulation 27 3.4 Hum modulation of carriers 29 3.5 Differential gain and phase 34 3.6 Echo rating 37 Appendix A Monitoring and assessment of system radiation 39 Appendix B General information on non-linear distortion 40 Appendix C Test carriers, levels and intermodulation prod

10、ucts 42 Appendix D Absorbing clamp and its application to measurement ofradiatedpower 44 Appendix E Stop filter 46 Appendix F Cable connecting adaptors 47 Appendix G Calibration of modulation depth 48 Figure 1 Arrangement of test equipment for measurement of mutual isolationbetween system outlets 2

11、Figure 2 Arrangement of test equipment for measurement of frequencyresponse within a channel 4 Figure 3 Interpretation of displays for measurement of frequency responsewithin a channel 4 Figure 4 Basic arrangement of test equipment for evaluation of the ratioofsignal to intermodulation product 6 Fig

12、ure 5 Connections to input of system head end 7 Figure 6 Measurement of radiation, general set-up 11 Figure 7 Measurement of radiation, component with several outputs 11 Figure 8 Measurement of radiation, absorbing clamp method 12 Figure 9 Example of general set-up for measurement of radiation in th

13、efrequency range 30 MHz to 300 MHz 14 Figure 10 Example of radiation measurement set-up (frequency range 30 MHzto 300 MHz) for measurements on the input port of an activecomponent 15 Figure 11 Radiation method without measurement cable 16 Figure 12 Radiation method with measurement cable 16 Figure 1

14、3 Example of radiation measurement set-up for frequency range 300 MHz to 1 GHz 17BS 6513-2:1984 ii BSI 01-2000 Page Figure 14 Arrangement of test equipment for carrier-to-noise ratio measurement 20 Figure 15 Test signals employed for chrominance/luminance gain and delayinequality 21 Figure 16 Arrang

15、ement of test equipment for measurement of chrominance/luminance gain and delay inequality 23 Figure 17 Displayed pulses: chrominance low and lagging 23 Figure 18 Displayed pulses: chrominance high and leading 24 Figure 19 Connection of test equipment for measurement of non-lineardistortion by compo

16、site beat 25 Figure 20 Weighting curve for 625-line PAL system I, C.W. interferencewithno special control 26 Figure 21 Measurement of two signal cross-modulation 29 Figure 22 Hum modulation envelope 30 Figure 23 Connection of equipment for measurement of hum modulation (d.c.method) 31 Figure 24 Cali

17、brated potential divider 32 Figure 25 Stable variable d.c. source 32 Figure 26 Oscilloscope display 33 Figure 27 Connection of equipment for measurement of hum modulation (a.c.method) 33 Figure 28 Signal D2 for 625-line systems 34 Figure 29 Arrangements of test equipment for measurement ofdifferenti

18、algain and phase 36 Figure 30 Example of the modified staircase waveform 36 Figure 31 Echo rating graticule 38 Figure 32 Arrangement of test equipment for measurement of echo rating 38 Figure 33 Example showing products formed when 2f a f b 42 Figure 34 Examples of products formed when 2f a f b 43 F

19、igure 35 Products of the form f a f b f c 44 Figure 36 Example of measurement of interference power between 30 MHzand 300 MHz 44 Figure 37 Detail of absorbing clamp 45 Figure 38 Example of calibration curve of absorbing clamp 45 Figure 39 Calibration of absorbing clamp between 30 MHz and 300 MHz 46

20、Figure 40 Stop filter 47 Figure 41 Adaptor for components with screwed clamp terminals 47 Figure 42 Adaptor for components with coaxial terminals 48 Figure 43 Calibration of modulation depth 49 Table 1 Correction factors where the modulation depth used is other than100% 30 Table 2 Residual carrier r

21、eduction factors 31 Table 3 Test signal levels relative to reference level 43 Publications referred to Inside back coverBS 6513-2:1984 BSI 01-2000 iii Foreword This Part of BS 6513 has been prepared under the direction of the Electronic Equipment Standards Committee. It is based on a draft provided

22、by the Department of Trade and Industry. It forms Part 2 of a multipart standard for wideband cabled distribution systems; the other Parts to date are as follows: Part 1: Glossary of terms; Part 3: Specification for performance requirements, including system safety, for downstream television and f.m

23、. sound radio signals; Part 4: Specification for performance requirements, including system safety, for upstream television. Details of the characteristics of the various signals referred to in this standard are given in the following International Radio Consultative Committee (CCIR) publications: t

24、elevision, 625-line, PAL, system I: CCIR Report 624-2 (1982); stereo radio, band II f.m.: CCIR Recommendation 450-1 (1982); teletext: CCIR Report 957 (1982). The following subjects relative to this Part will be included as additional clauses or supplements at a later date. Test methods for f.m. soun

25、d radio signals: echo rating; hum modulation; single and multiple frequency interference; data signals within the channel. Test methods for television signals: signals received via earth-orbiting satellites; teletext; crossview ratio. General test methods: immunity of system components; immunity of

26、complete systems; radiation from complete systems. Test methods for digital signals. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of its

27、elf confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages1 to 50, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be in

28、dicated in the amendment table on the inside front cover.iv blankBS 6513-2:1984 BSI 01-2000 1 Section 1. General 1.1 Scope This Part of BS 6513 describes methods of measuring the performance of wideband cabled distribution systems for downstream and upstream television signals and f.m. sound radio s

29、ignals. A method of monitoring and assessing system radiation is described in Appendix A. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 1.2 Definitions, designations and abbreviations 1.2.1 Definitions. For the purposes of this Part of BS 6513,

30、the definitions given in Part 1 apply. 1.2.2 Designations and abbreviations. For the purposes of this Part of BS 6513, the frequency band designations and abbreviations given in BS4727-3:Group 07 apply. Section 2. Methods of measurement applicable to both television and f.m. sound radio signals 2.1

31、Mutual isolation between system outlets 2.1.1 Principle. The method describes the measurement of the attenuation between two system outlets at any frequency within the range of a cabled distribution system. Usually this is specified as the minimum value obtained and isolation is measured between any

32、 combination of the following: a) system outlets connected to adjacent subscribers taps; b) system outlets connected to the same multiple subscribers taps; c) adjacent looped system outlets. 2.1.2 Equipment NOTEIt is essential that the test set-up is well-matched. 2.1.2.1 Sweep frequency generator,

33、with frequency range or ranges to suit the system to be examined, equipped with a frequency marking system. 2.1.2.2 Terminating wideband detector, with sensibly flat response. NOTE 1Any departures from a flat response will be compensated by calibration of the test equipment (see 2.1.3.1 to 2.1.3.3).

34、 NOTE 2In this context, “wideband” means of sufficient bandwidth to cover the full frequency range of the system under investigation. NOTE 3This device may be included in some sweep frequency generators. 2.1.2.3 Variable attenuator, adjustable in steps of not more than 1 dB up to a value greater tha

35、n the maximum mutual isolation to be measured. 2.1.2.4 Wideband amplifier, with a sensibly flat amplitude/frequency characteristic (see notes 1 and 2 of2.1.2.2) and sufficient gain to raise the signal level at the system outlet to a level suitable to drive the detector. 2.1.2.5 Oscilloscope or other

36、 display unit, suitable for operation with the sweep frequency generator. 2.1.2.6 Appropriate coaxial cable, of sufficient length to reach from one system outlet to the other selected outlet in the cabled distribution system. 2.1.3 Procedure 2.1.3.1 With the equipment connected as shown in Figure 1(

37、a), set the variable attenuator to a value just greater than the maximum value of mutual isolation expected to be measured. Record this value of the attenuator as a 1 . 2.1.3.2 Adjust the output level of the sweep generator to give a level at the input to the amplifier approximately equal to that av

38、ailable at a system outlet. 2.1.3.3 Adjust the oscilloscope and amplifier gain controls to produce a display and note the amplitude of the display over the frequency range under inspection.BS 6513-2:1984 2 BSI 01-2000 2.1.3.4 Remove from the section under test the signals normally distributed on the

39、 system whilst maintaining the correct terminating conditions. Connect the equipment as shown in Figure 1(b). NOTEThe output from the sweep generator is connected to the local system outlet and the long cable (2.1.2.6) is used to connect to the remote outlet. 2.1.3.5 Reduce the attenuator setting un

40、til the peak of the display just reaches the same amplitude as that noted in 2.1.3.3 for the frequency at which peak occurs. Record the new value of the attenuator as a 2 . 2.1.3.6 If the system outlets are of dual socket design, for example, television/radio, the mutual isolation should also be mea

41、sured at the appropriate frequencies between one socket, for example television, of the local system outlet and the alternate socket, for example, radio, of the remote system outlet and vice versa. In these cases, it will also be necessary to measure mutual isolation with the unused sockets in both

42、terminated and open-circuit conditions. The conditions of measurement should be stated when tabulating results. 2.1.4 Expression of results. Mutual isolation is given by a 1p a 2 . Where the measurement is made within a number of discrete frequency bands, take the lowest result obtained as the mutua

43、l isolation between the two system outlets under investigation. 2.2 Amplitude/frequency response within a channel 2.2.1 Principle. The method describes the measurement of the frequency response of cabled distribution systems over the frequency range of an individual channel between two specified poi

44、nts within the system. However, where input signals to the system are received at, or are reduced to, baseband, and modulated on to the system carrier frequencies, the response of any demodulator and modulator is not included. If it is required to include the characteristics of these items, a separa

45、te assessment should be made using test techniques applicable to such equipment. Figure 1 Arrangement of test equipment for measurement of mutual isolation between system outletsBS 6513-2:1984 BSI 01-2000 3 Where the system contains frequency changing equipment between the antenna input and the syst

46、em outlet at which the tests are to be made, the calibration of the equipment is carried out at the output frequencies, having first checked that the output of the sweep frequency generator is also flat over the input channel. 2.2.2 Equipment NOTEIt is essential that the test set-up is well-matched.

47、 2.2.2.1 Sweep frequency generator, adjustable to cover the frequency range of the channel to be measured. 2.2.2.2 Terminating r.f. detector, with a sensibly flat response over the channel to be measured. NOTEAny departures from a flat response will be compensated by calibration of the test equipmen

48、t (see 2.2.3.1 to 2.2.3.5). 2.2.2.3 Two variable attenuators, adjustable in steps of not more than 1 dB. 2.2.2.4 Amplifier, with a sensibly flat response over the channel to be measured (see note to 2.2.2.2) and sufficient gain to raise the signal level at the output test point to a level suitable t

49、o drive the detector. 2.2.2.5 Dual trace oscilloscope, having sufficient sensitivity to produce a satisfactory display from the output signal available from the detector. 2.2.2.6 High output signal generator (having an output of at least 300 mV r.m.s. terminated), of known frequency calibration over the frequency range of the channel to be tested. 2.2.2.7 Balanced mixer, suitable for use in the frequency range of the channel to be tested. 2.2.2.8 Low-pass filter, with