ITU-T G 222-1993 NOISE OBJECTIVES FOR DESIGN OF CARRIER-TRANSMISSION SYSTEMS OF 2500 km《设计2500km载波传输系统的噪声指标》.pdf
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1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU).4%2.!4)/.!,G0G0!.!,/5%G0G0#!22)%2G0G03934%-3%.%2!,G0G0#(!2!#4%2)34)#3G0G0#/-/.G0G04/G0G0!,!.!,/5%G0G0#!22)%2G1342!.3-)33)/.G0G03934%-3./)3%G0G0/“*%#4)6%3G0G01.2.2 the mean psophometric noise power over one mi
2、nute shall not exceed 50 000 pW0p for more than 0. 1 % ofany month;1.2.3 the unweighted noise power, measured or calculated with an integrating time of 5 ms shall not exceed1 000 000 pW0 (106pW0) for more than 0.01% (10-4) of any month.Note - For carrier transmission systems with one-minute mean noi
3、se power distributions which are not welldefined, the inclusion of another one-minute mean noise clause would be desirable to ensure equivalent performance forall systems. This clause would specify that:The mean psophometric noise power over one minute shall not exceed 20 000 pW0p for more than 3% o
4、f anymonth.This clause has not been specifically included because the CCIR has determined that for radio-relay links, theapplication of clauses 1.2.1 and 1.2.2 are sufficient to ensure, with high probability, that the additional clause will alsobe satisfied.1.3 If it is intended to use amplitude-mod
5、ulated voice-frequency telegraph equipment for 50 bauds conforming tothe Series R Recommendations and to obtain the quality shown in Recommendation F.10 1, the mean nonweightednoise power over 5 ms must not exceed 106pW0 during more than 0.001% (10-5) of any month, nor more than 0.1% ofany hour, for
6、 cable systems and for radio-relay links.If frequency-modulated voice-frequency telegraph equipment operating at 50 bauds is used, it is to be expectedthat the quality specified in 1.1 and 1.2 respectively above will be satisfactory as far as the telegraph transmission isconcerned.The conditions und
7、er which the above design objectives should apply are given in 2 below.2 Fascicle III.2 - Rec. G.2222 Conditions in which the design objectives for hypothetical reference circuits apply2.1 The values mentioned in 1 above are design objectives and it is not intended that they should be quoted inspeci
8、fications for equipment or used for acceptance tests. The noise on a homogeneous section of an actual carriersystem is dealt with in Recommendation G.226.The following Recommendations specify the conditions in which these general objectives apply to differenttypes of system, account being taken of t
9、he special characteristics of each system:- symmetric pair cable systems (Recommendation G.322);- symmetric pair cable “12 + 12“ systems (Recommendation G.326);- 4-MHz systems (Recommendation G.338 2), 12-MHz systems (Recommendations G.332 and G.339),18 MHz systems (Recommendation G.334) and 60 MHz
10、systems (Recommendation G.333) on 2.6/9.5-mm coaxial pairs;- systems on 1.2/4.4-mm coaxial pairs (Recommendations G.341, G.343, G.344, G.345 and G.346);- radio-relay links using frequency-division multiplex (Recommendation 393 3 of the CCIR).In particular, Recommendation G.442 lays down objectives f
11、or the use of amplitude-modulation voice-frequency telegraphy used in line-of-sight radio-relay systems.Tropospheric-scatter radio-relay systems should meet the objectives of this Recommendation, or otherobjectives, according to the circumstances of operation (see CCIR Recommendation 397 4).Other ob
12、jectives are recommended for systems providing 12 carrier circuits on an open-wire pair (seeRecommendation G.311).2.2 Designers are expected to fit their distribution curves to fall below both points given in 1.2.1 and 1.2.2above.2.3 In connection with 1.2.2 above, the CCITT would have preferred to
13、indicate a figure of 100 000 pW0p(average psophometric power over one minute at a zero relative level point), not to be exceeded during more than 0.01%of any month. On account of difficulties in measurement, a figure of 50 000 pW0p for 0.1% of any month has beenshown.2.4 Within each homogeneous sect
14、ion of a hypothetical reference circuit, the telephone channels will occupy thesame position in relation to each other. Within these sections, certain intermodulation products (those of odd order) tendto add on the basis of linear addition of voltages, but between sections it may be considered that
15、in respect of noise apower-additive law applies exclusively.In a part of a hypothetical reference circuit consisting of one or more equal homogeneous sections, the one-minute mean noise power not exceeded during 20% of any month shall be considered to be proportional to the numberof homogeneous sect
16、ions involved.2.5 In parts of a hypothetical reference circuit consisting of one or more equal homogeneous sections, the smallpercentage of any month in which the one-minute mean power may exceed the design objective for 0.1% of the time orless shall be regarded as proportional to the number of homo
17、geneous sections involved. This principle also applies to theobjective mentioned in 1.2.3 above.2.6 Although in principle it is to be understood that the general noise objectives are all-embracing, in practice it isrecognized that there will be abnormalities from time to time which will result in ad
18、ditional noise sources becomingevident. Often, such extra contributions can be accommodated within the margin available within the system design. Inother cases, no concern need be felt provided that such additional contributions are small compared to the generalobjective, for example, less than 10%
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