ITU-T J.21 (08 1994)(英) Performance characteristic

INTERNATIONALTELECOMMUNICATIONUNION)454*EX#-44 TELECOMMUNICATION(08/94)STANDARDIZATIONSECTOROFITU4%,%6)3)/.!.$3/5.$42!.3-)33)/.0%2&/2-!.#%#(!2!#4%2)34)#3/&K(Z490%3/5.$02/'2!--%#)2#5)43#)2#5)43&/2()'(15!,)49-/./0(/.)#!.$34%2%/0(/.)#42!.3-)33)/.3)4542ECOMMENDATION*(FormerlyRecommendationITU-RCMTT)FOREWORDTheITU-T(TelecommunicationStandardizationSector)isapermanentorganoftheInternationalTelecommunicationUnion(ITU).TheITU-Tisresponsibleforstudyingtechnical,operatingandtariffquestionsandissuingRecommen-dationsonthemwithaviewtostandardizingtelecommunicationsonaworldwidebasis.TheWorldTelecommunicationStandardizationConference(WTSC),whichmeetseveryfouryears,establishesthetopicsforstudybytheITU-TStudyGroupswhich,intheirturn,produceRecommendationsonthesetopics.TheapprovalofRecommendationsbytheMembersoftheITU-TiscoveredbytheprocedurelaiddowninWTSCResolutionNo.1(Helsinki,March1-12,1993).ITU-TRecommendationJ.21wasrevisedbyITU-TStudyGroup9(1993-1996)andwasapprovedundertheWTSCResolutionNo.1procedureonthe22ndofAugust1994.___________________NOTEInthisRecommendation,theexpression“Administration”isusedforconcisenesstoindicatebothatelecommunicationadministrationandarecognizedoperatingagency.ITU1995Allrightsreserved.Nopartofthispublicationmaybereproducedorutilizedinanyformorbyanymeans,electronicormechanical,includingphotocopyingandmicrofilm,withoutpermissioninwritingfromtheITU.RecomendationJ.21(08/94)iCONTENTSRecomendationJ.21(08/94)Page1Application.....................................................................................................................................................12Interfacecharacteristics..................................................................................................................................12.1Testconditions..................................................................................................................................12.2Impedance.........................................................................................................................................12.3Levels................................................................................................................................................23Overallperformance.......................................................................................................................................23.1Commonparameters.........................................................................................................................23.2Additionalparametersforstereophonicprogrammetransmission...................................................53.3Additionalrequirementsfordigitalsystems.....................................................................................6AnnexA–Themeasurementofnon-linearityintheupperfrequencyrange...........................................................7iiRecomendationJ.21(08/94)SUMMARYThisRecommendationcontainsdesignobjectivesforequipmenttobedevelopedforthetransmissionofhigh-qualitytypesound-programmes.Itgivestheparameterstobeenvisagedandappropriatequalityvalues.Measuringmethodsforseveralparametersarespecified.RecommendationJ.21(08/94)1RecommendationJ.21 RecommendationJ.21(08/94)PERFORMANCECHARACTERISTICSOF15kHz-TYPESOUND-PROGRAMMECIRCUITS–CIRCUITSFORHIGHQUALITYMONOPHONICANDSTEREOPHONICTRANSMISSIONS2)(1974;revised1978,1982,1986,1990and1994)TheITU-T,considering(a)thatitisnecessarytosettransmissionstandardsforsound-programmecircuits;(b)thatqualityrequirementsforthehypotheticalreferencecircuitareestablishedforanaloguesoundprogrammes;(c)thatadvantageshouldbetakenofthetechnicalevolutionmadepossiblebytheintroductionofdigitaltechniques,particularlyformixedanalogueanddigitalcircuits,recommendsthat,withdueregardtotheapplicationconstraints,equipmentfornewcircuitsshallmeettherequirementslaidoutbelow.1ApplicationThisRecommendationappliestohomogeneousanalogueormixedanalogue-and-digitalcircuits.Therequirementsbelowapplytothehypotheticalreferencecircuit(HRC)definedinRecommendationJ.11(formerlyITU-RRecommendationCMTT.502).ForestimationoftheperformanceofcircuitsshorterorlongerthantheHRC,seeITU-TRecommendationCMTT.605.NOTES1Forall-digitalcircuits,aseparateRecommendationmightbeenvisagedafterfurtherstudy.2Forfurtherinformation,ITU-RReportCMTT.496maybeconsulted.ThisReportalsodrawsattentiontocertaindifferencesbetweenCCIRandOIRTRecommendations.2Interfacecharacteristics2.1TestconditionsWhencircuitperformanceistobemeasured,thesystemoutputshallbeterminatedbyabalancedtestload,nominally600Ωresistive.2.2ImpedanceSysteminputimpedance600Ωbalanced3)Systemoutputimpedance,provisionallyLow,balanced_______________1)FormerlyITU-RRecommendationCMTT.505-4.2)Forthedefinitionofabsolutepower,relativepowerandnoiselevels,seeITU-RRecommendationV.574.3)Thetolerance,permittedreactanceanddegreeofunbalanceneedfurtherstudy.2RecommendationJ.21(08/94)Theopen-circuitoutputlevelshallnotdecreasemorethan0.3dBwithinthenominalfrequencyrange,iftheoutputist